US20120311810A1 - Autonomous coverage robot - Google Patents

Abstract

A surface treatment robot including a robot body, a differential drive system mounted on the robot body and configured to maneuver the robot over a cleaning surface, a liquid applicator carried by the robot body, and a collection assembly carried by the robot body and configured to remove waste from the cleaning surface. The robot body has a forward portion and a rear portion, with the forward portion preceding the rear portion as the robot moves in a forward direction over the cleaning surface. The liquid applicator is configured to dispense a liquid to the cleaning surface such that at least a portion of the liquid is dispensed rear of the collection assembly as the robot moves in the forward direction.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This U.S. patent application is a continuation, and claims priority under 35 U.S.C. §120, from U.S. patent application Ser. No. 12/983,837, filed Jan. 3, 2011, entitled AUTONOMOUS COVERAGE ROBOT, now pending, the disclosure of which is considered part of the disclosure of this application and is hereby incorporated by reference in its entirety.
TECHNICAL FIELD
• The disclosure relates to surface cleaning robots, such as robots configured to perform autonomous cleaning tasks.
BACKGROUND
• Wet cleaning of household surfaces has long been done manually using a wet mop or sponge. The mop or sponge is dipped into a container filled with a cleaning fluid to allow the mop or sponge to absorb an amount of the cleaning fluid. The mop or sponge is then moved over the surface to apply a cleaning fluid onto the surface. The cleaning fluid interacts with contaminants on the surface and may dissolve or otherwise emulsify contaminants into the cleaning fluid. The cleaning fluid is therefore transformed into a waste liquid that includes the cleaning fluid and contaminants held in suspension within the cleaning fluid. Thereafter, the sponge or mop is used to absorb the waste liquid from the surface. While clean water is somewhat effective for use as a cleaning fluid applied to household surfaces, most cleaning is done with a cleaning fluid that is a mixture of clean water and soap or detergent that reacts with contaminants to emulsify the contaminants into the water. In addition, it is known to clean household surfaces with water and detergent mixed with other agents such as a solvent, a fragrance, a disinfectant, a drying agent, abrasive particulates and the like to increase the effectiveness of the cleaning process.
• The sponge or mop may also be used as a scrubbing element for scrubbing the floor surface, and especially in areas where contaminants are particularly difficult to remove from the household surface. The scrubbing action serves to agitate the cleaning fluid for mixing with contaminants as well as to apply a friction force for loosening contaminants from the floor surface. Agitation enhances the dissolving and emulsifying action of the cleaning fluid and the friction force helps to break bonds between the surface and contaminants.
• After cleaning an area of the floor surface, the waste liquid must be rinsed from the mop or sponge. This is typically done by dipping the mop or sponge back into the container filled with cleaning fluid. The rinsing step contaminates the cleaning fluid with waste liquid and the cleaning fluid becomes more contaminated each time the mop or sponge is rinsed. As a result, the effectiveness of the cleaning fluid deteriorates as more of the floor surface area is cleaned.
• Some manual floor cleaning devices have a handle with a cleaning fluid supply container supported on the handle and a scrubbing sponge at one end of the handle. These devices include a cleaning fluid dispensing nozzle supported on the handle for spraying cleaning fluid onto the floor. These devices also include a mechanical device for wringing waste liquid out of the scrubbing sponge and into a waste container.
• Manual methods of cleaning floors can be labor intensive and time consuming. Thus, in many large buildings, such as hospitals, large retail stores, cafeterias, and the like, floors are wet cleaned on a daily or nightly basis. Industrial floor cleaning “robots” capable of wet cleaning floors have been developed. To implement wet cleaning techniques required in large industrial areas, these robots are typically large, costly, and complex. These robots have a drive assembly that provides a motive force to autonomously move the wet cleaning device along a cleaning path. However, because these industrial-sized wet cleaning devices weigh hundreds of pounds, these devices are usually attended by an operator. For example, an operator can turn off the device and, thus, avoid significant damage that can arise in the event of a sensor failure or an unanticipated control variable. As another example, an operator can assist in moving the wet cleaning device to physically escape or navigate among confined areas or obstacles.
SUMMARY
• Presently disclosed is an autonomous robot for treating surfaces, such as floors and countertops, which has a form factor that facilitates cleaning in tightly dimensioned spaces, such as those found in many households. In one example, the robot may include a weight distribution that remains substantially constant throughout the cleaning process, the weight distributed between a cleaning element, a squeegee, and drive wheels. The weight distribution can provide sufficient pressure to the wetting assembly and the squeegee while allowing sufficient thrust to be applied at drive wheels. As an advantage, the robot can have a small volume required to navigate in tightly dimensioned spaces while having a weight distribution configured for wet-cleaning a surface.
• A surface treatment robot includes a robot body, a differential drive system, a liquid applicator, a controller, and a potting material. The robot body has a forward portion, a rear portion, an upper portion, and a lower portion, the forward portion preceding the rear portion as the robot moves in a forward direction over a cleaning surface, and the upper portion disposed above the lower portion as the robot moves over the cleaning surface. The differential drive system is mounted on the robot body and configured to maneuver the robot over a cleaning surface. The liquid applicator is carried by the robot body and defines a liquid storage volume. The liquid applicator is configured to dispense a liquid from the liquid storage volume to the cleaning surface.
• The controller is carried by the robot body and is in communication with the differential drive system to direct the robot over the cleaning surface. The potting material has a coefficient of linear thermal expansion of less than about 250 ppm/° C., and the potting material is disposed about the controller such that the potting material substantially isolates the controller from fluid communication with the liquid applicator.
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In some implementations, the potting material has a glass transition temperature less than about −40° C. The potting material can be a two-component urethane with a set time of less than about ten minutes.
• In certain implementations, the potting material is between about 5 percent and about 20 percent of the mass of the robot. For example, the potting material can have a mass of between about 110 g and about 140 g. Additionally or alternatively, the potting material can have a specific gravity of between about 1.2 and about 1.6. In certain examples, the potting material has a thermal conductivity of about 0.15 W/(m·K) to about 0.40 W/(m·K).
• In some implementations, the potting material is disposed along the lower portion of the robot body. In certain implementations, the robot body defines an orifice configured to receive the potting material into the robot body. For example, the orifice can be defined along the lower portion of the robot body. Additionally or alternatively, the robot body can have a substantially flat side portion and the orifice is defined toward the substantially flat side portion. The potting material can have an uncured viscosity at room temperature of between about 8000 centipoise and about 10000 centipoise and is heatable to an uncured viscosity of between about 3000 centipoise and about 5000 centipoise.
• In certain implementations, the robot further includes a liquid collection assembly carried by the robot body and defining a liquid collection volume. The liquid collection assembly can be configured to remove at least a portion of the dispensed liquid from the cleaning surface into the liquid collection volume, and the potting material can substantially isolate the controller from fluid communication with the liquid collection assembly. For example, the controller can include a circuit board, a plurality of proximity sensors, and a plurality cliff sensors.
• A method of assembling a surface treatment robot includes introducing a potting material into a body of the surface treatment robot, moving the potting material in a vertical direction through the body such that the potting material moves over a controller disposed within the body, and curing the potting material to isolate the controller from fluid communication with a liquid applicator carried by the body. The potting material is introduced through an orifice defined by the body
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In some implementations, the body is oriented substantially perpendicular to the orientation of the body as the robot moves over a cleaning surface such that a forward portion of the robot body is above a rear portion of the robot body in the substantially perpendicular orientation. In certain implementations, the substantially perpendicular orientation of the body is substantially parallel to the vertical direction of movement of the potting material through the body.
• In certain implementations, the orifice is disposed toward a rear portion of the body and movement of the potting material in a vertical direction includes moving air out of the body. For example, the air can be moved out of the body through a forward portion of the body. Additionally or alternatively, the rear portion of the body includes a substantially flat portion and orienting the body substantially perpendicular to the orientation of the body as the robot moves over the cleaning surface can include positioning the substantially flat portion of the body on a surface.
• In some implementations, the orifice is defined through a portion of the robot body disposed toward a cleaning surface as the robot moves over the cleaning surface. For example, the orifice can be an x-shaped orifice, and the cured potting material can seal the orifice.
• In certain implementations, introducing the potting material into the body of the surface treatment robot includes introducing between about 110 g and about 140 g of potting material into the robot body. The potting material can have a specific gravity of between about 1.2 and about 1.6. Additionally or alternatively, the potting material can have a coefficient of linear thermal expansion of less than about 250 ppm/degrees C.
• In some implementations, the potting material has a thermal conductivity of about 0.15 W/(m·K) to about 0.40 W/(m·K). In some implementations, the potting material is a two-part urethane. The potting material can have a viscosity at room temperature of about 8000 centipoise to about 10000 centipoise viscosity at room temperature. Additionally or alternatively, the potting material can be heated to reduce the viscosity of the potting material to about 3000 centipoise to about 5000 centipoise. In some implementations, cured potting material isolates the controller from fluid communication with a liquid storage volume at least partially defined by the body.
• A surface treatment robot includes a robot body, a cleaning assembly, and a right drive wheel and a left drive wheel. The robot body has a forward portion, a rear portion, the forward portion preceding the rear portion as the robot moves in a forward direction over a cleaning surface. The cleaning assembly is carried by the robot body and configured to remove debris from the cleaning surface. Each drive wheel is rotatable about an axis parallel to the cleaning surface and transverse to the forward direction of movement of the robot over the cleaning surface. Each drive wheel includes a rim and a right tire and a left tire disposed about a circumference of a respective drive wheel. Each tire includes a base having a first side and a second side substantially opposite the first side, a first and second set of treads, each tread of the first and second set of treads extending radially from the first side of the base toward the cleaning surface. Each tread of the first and second set of treads is elongate in a direction substantially parallel to the transverse axis, and each tread of the first set of treads is circumferentially offset from each of the treads of the second set of treads.
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In some implementations, each tread of the first and second set of treads has at least one substantially square edge disposed toward the cleaning surface. Additionally or alternatively, each tread of the first and second set of treads has substantially the same circumferential width. In certain implementations, each tread of the first and second set of treads is circumferentially spaced from a preceding tread of the respective set of treads by a distance about three times the circumferential width of the tread. Additionally or alternatively, each tread can extend radially from the base by a distance between about ⅕ to about ½ the radial thickness of the base.
• In some implementations, the tire includes natural rubber and between about 20 percent and about 30 percent particulate matter. For example, the particulate matter can include one or more of the following: kaolin clay and calcium carbonate.
• In certain implementations, each wheel is disposed rear of at least a portion of the cleaning assembly as the robot moves in the forward direction over the cleaning surface. The cleaning assembly can include a liquid applicator. For example, at least a portion of the liquid applicator is disposed forward of each wheel as the robot moves in the forward direction over the cleaning surface. In some implementations, the cleaning assembly includes a vacuum assembly. For example, at least a portion of the vacuum assembly is disposed rear of each wheel as the robot moves in the forward direction over the cleaning surface.
• In some implementations, each tire includes a third and fourth set of treads extending radially from the second side of the base toward the respective rim. For example, the third set of treads can be substantially opposite the first set of treads and the fourth set of treads can be substantially opposite the second set of treads. Additionally or alternatively, each tread of third set of treads is circumferentially offset from each tread of the first set of treads and each tread of the fourth set of treads is circumferentially offset from each tread of the second set of treads.
• In certain implementations, at least a portion of the base is movable toward the wheel when a tread of the first or second set of treads contacts the cleaning surface. In some implementations, the third set of treads and the fourth set of treads define at least a portion of channel extending circumferentially around the tire, along the second surface of the base. Additionally or alternatively, each wheel can include a circumferential ridge extending radially outward, toward the cleaning surface, the circumferential ridge engageable with the channel defined by the respective tire. In some implementations, the tire is reversible such that the third and fourth sets of treads extend toward the cleaning surface and the first and second sets of treads extend toward the respective rim.
• A surface treatment robot includes a robot body, a differential drive system mounted on the robot body and configured to maneuver the robot over a cleaning surface, a collection assembly carried by the robot body and configured to remove waste from the cleaning surface, a liquid applicator carried by the robot body and a wetting assembly. The robot has a forward portion and a rear portion, with the forward portion preceding the rear portion as the robot moves in a forward direction over a cleaning surface. The liquid applicator defines a liquid storage volume and the liquid applicator is configured to dispense a liquid rear of the collection assembly as the robot moves in the forward direction. The wetting assembly includes a plurality of rows of bristles forward of the collection assembly and a row of bristles rear of the collection assembly. The row of bristles rear of the collection assembly has an angle of incidence of about 45 degrees with the cleaning surface as the robot moves in the forward direction.
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In some implementations, the base of the robot is supported about 4 mm above the cleaning surface as the robot moves across the cleaning surface in the forward direction and the bristles of the row of bristles rear of the collection assembly have a length of about 5 mm to about 6 mm. In certain implementations, the collection assembly includes a squeegee formed with a longitudinal ridge disposed proximate to the cleaning surface and extending across a cleaning width for providing a liquid collection volume at a forward edge of the ridge as the robot moves in the forward direction. The longitudinal ridge can have about 0.25 mm to about 0.75 mm of interference with the cleaning surface. Additionally or alternatively, the longitudinal ridge can be movable in a direction away from the cleaning surface by between about 2 mm and about 4 mm.
• In certain implementations, a baseplate is carried on the robot body, and the wetting assembly is disposed on the baseplate. Additionally or alternatively, at least a portion of the collection assembly can be disposed on the baseplate and the baseplate can be releasably attachable to the robot body.
• In some implementations, the plurality of rows of bristles forward of the collection assembly includes at least one row of bristles having about zero interference with the cleaning surface and a row of bristles having an interference with the cleaning surface. For example, the row of bristles having an interference with the cleaning surface can be disposed rear of the at least one row of bristles having about zero interference with the cleaning surface as the robot moves across the cleaning surface in the forward direction. Additionally or alternatively, the bristles of the at least one row of bristles having about zero interference with the cleaning surface are longer than the bristles of the row of bristles having an interference with the cleaning surface.
• In certain implementations, a baseplate is carried on the robot body, and the baseplate has a recessed portion and an unrecessed portion. The at least one row of bristles having about zero interference with the cleaning surface can be disposed along the recessed portion. Additionally or alternatively, the row of bristles having an interference with the cleaning surface can be disposed along the unrecessed portion.
• In some implementations, the differential drive system includes a right drive wheel and a left drive wheel and the collection assembly is disposed rear of the right and left drive wheels. In certain implementations, the surface treatment robot has a center of gravity substantially at the center of the robot as viewed from the above the robot as the robot moves across the cleaning surface and the liquid storage volume is full of liquid.
• In certain implementations, the diameter of each bristle of the row of bristles rear of the collection assembly is about twice the diameter of each bristle of the plurality of rows of bristles forward of the collection assembly. Additionally or alternatively, the diameter of the bristles of the row of bristles rear of the collection assembly is about 0.05 mm to about 0.2 mm. In another additional or alternative example, the coefficient of friction of the bristles of each row of bristles is about 0.1 to about 0.3 on a wet cleaning surface. In certain implementations, each row of bristles comprises a plurality of plugs about 1 mm in diameter.
• A surface treatment robot including a robot body, a differential drive system mounted on the robot body and configured to maneuver the robot over a cleaning surface, a liquid applicator carried by the robot body, and a collection assembly carried by the robot body and configured to remove waste from the cleaning surface. The robot body has a forward portion and a rear portion, with the forward portion preceding the rear portion as the robot moves in a forward direction over the cleaning surface. The liquid applicator is configured to dispense a liquid to the cleaning surface such that at least a portion of the liquid is dispensed rear of the collection assembly as the robot moves in the forward direction.
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In some implementations, the liquid applicator dispenses between about 30 percent and about 70 percent of the liquid forward of the collection assembly and at least about 30 percent of the liquid rear of the collection assembly. For example, the liquid applicator can dispense about 60 percent of the liquid forward of the collection assembly and about 40 percent of the liquid rear of the collection assembly.
• In certain implementations, the liquid applicator includes a spray nozzle arranged to dispense liquid rear of the collection assembly as the robot moves in the forward direction. Additionally or alternatively, the liquid applicator can include a drip assembly configured to drip liquid rear of the collection assembly as the robot moves in the forward direction.
• In some implementations, the collection assembly is a vacuum assembly including a collection region and a suction region in fluid communication with the collection region.
• In certain implementations, a collection volume carried is carried by the robot body, and the collection volume is in fluid communication with the vacuum assembly to collect waste removed by the vacuum assembly.
• In some implementations, the collection assembly includes a surface agitation assembly. The surface agitation assembly can include one or more of the following: a stationary brush, a rotating brush, a woven cloth, a nonwoven cloth, a sponge, and a compliant blade.
• In some implementations, the robot includes a humidity sensor and the surface agitation assembly includes an active scrubbing element configured to act on the cleaning surface based at least in part on detection of humidity on the cleaning surface.
• In certain implementations, the differential drive system includes right and left drive wheels and the collection assembly is disposed rear of the right and left drive wheels.
• In some implementations, a wetting assembly is carried by the robot body. At least a portion of the wetting assembly can be disposed rear of the collection assembly and rear of the liquid applicator as the robot moves in the forward direction. At least a portion of the wetting assembly can contact the cleaning surface as the robot moves in the forward direction.
• In some implementations, the wetting assembly includes a compliant blade extending in a direction substantially parallel to the cleaning surface. In certain implementations, the wetting assembly includes a plurality of bristles extending from the robot body, toward the cleaning surface. For example, at least some of the plurality of bristles and the cleaning surface define an oblique angle therebetween (e.g., an acute angle in the direction toward the forward portion of the robot).
• A method of surface treatment includes maneuvering a surface treatment robot over a cleaning surface, dispensing a liquid from the liquid applicator to the cleaning surface, and collecting waste into the collection assembly from the cleaning surface. The robot has a forward portion and a rear portion, with the forward portion preceding the rear portion over the cleaning surface as the robot moves in a forward direction, and the robot includes a liquid applicator and a collection assembly. At least a portion of the liquid is dispensed rear of the collection assembly as the robot moves in the forward direction.
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In some implementations, dispensing liquid from the liquid applicator to the cleaning surface includes dispensing between about 30 percent and about 70 percent of the liquid forward of the collection assembly and at least about 30 percent of the liquid rear of the collection assembly. For example, dispensing liquid from the liquid applicator to the cleaning surface includes dispensing about 60 percent of the liquid forward of the collection assembly and about 40 percent of the liquid rear of the collection assembly.
• In certain implementations, maneuvering the surface treatment robot includes returning to a portion of the cleaning surface to collect the liquid dispensed rear of the collection assembly.
• A surface treatment robot includes a robot body, a drive system mounted on the robot body and configured to maneuver the robot over a cleaning surface, a base plate detachably coupled to the robot body, and a squeegee disposed on the base plate. The robot body has a forward portion and a rear portion, with the forward portion preceding the rear portion as the robot moves in a forward direction over a cleaning surface. The squeegee is formed with a longitudinal ridge disposed proximate to the cleaning surface and extending across a cleaning width for providing a liquid collection volume at a forward edge of the ridge as the robot moves in the forward direction. The squeegee includes a first edge portion and a second edge portion disposed on respective sides of the longitudinal ridge. The first edge portion is releasably attached to the base plate and the second edge portion is unattached to the base plate.
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In some implementations, the squeegee is at least partially pivotable about the first edge portion as the second edge portion is moved away from the base plate. In certain implementations, the releasable attachment of the first edge portion of the squeegee to the base plate includes an interference fit. In some implementations, the first edge portion is disposed forward of the second edge portion as the robot moves over the cleaning surface in the forward direction.
• In certain implementations, a vacuum chamber is at least partially formed by the squeegee. The vacuum chamber can be disposed proximate to the longitudinal ridge such that suction applied at the vacuum chamber holds the second edge portion of the squeegee in a substantially fixed position relative to the base plate. Additionally or alternatively, the vacuum chamber is in fluid communication with the liquid collection volume by a plurality of suction ports defined by the squeegee.
• In some implementations, the drive system includes right and left drive wheels and the base plate defines at least a portion of a wheel well of each drive wheel.
• In certain implementations, the squeegee is disposed rear of the right and left drive wheels as the robot moves in the forward direction over the cleaning surface. In some implementations, an interference between the longitudinal ridge and the cleaning surface is between about 0.5 mm and about 2.5 mm.
• In some implementations, a wetting assembly is disposed on the base plate. At least a portion of the wetting assembly can be disposed rear of the squeegee as the robot moves in the forward direction over the cleaning surface.
• A method of assembling a surface treatment robot includes testing performance of a plurality of motors on an encoder station, classifying each motor based at least in part on the performance test results; selecting a first and a second motor from the same class;
• and mounting the first and second motors on a robot body of an autonomous surface coverage robot. The first motor drives a right drive wheel of the robot and the second motor drives a left drive wheel of the robot.
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In some implementations, testing performance of the plurality of motors includes providing power to each motor and determining the speed of the output shaft of the respective motor. In certain implementations, classifying each motor includes identifying motors with output shaft speed varying by less than about ten percent from one another as a function of power to each motor.
• In some implementations, the robot body is driven in a substantially straight line by providing substantially the same amount of power to the first drive motor and the second drive motor.
• A surface treatment robot includes a robot body, a differential drive system mounted on the robot body and configured to maneuver the robot over a cleaning surface, a liquid applicator carried by the robot body, a pump, an encoder arranged to measure speed of the pump, and a controller carried by the robot body. The robot body has a forward portion, a rear portion, an upper portion, and a lower portion. The forward portion precedes the rear portion as the robot moves in a forward direction over a cleaning surface. The upper portion is disposed above the lower portion as the robot moves over the cleaning surface. The liquid applicator defines a liquid storage volume. The liquid applicator includes a pump in fluid communication with the liquid storage volume and an encoder. The pump is configured to move a liquid from the liquid storage volume to the cleaning surface, and the encoder is arranged to measure speed of the pump. The controller is in communication with the encoder and configured to receive a signal from the encoder to determine speed of the pump as a function of voltage supplied to the pump.
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In some implementations, the controller is further configured to determine the speed of the pump as a function of voltage supplied to the pump during a start-up period and to control the speed of the pump based at least in part on controlling voltage supplied to the pump after the start-up period. For example, the start-up period can be greater than about 5 seconds and less than about 300 seconds.
• In certain implementations, the controller is further configured to receive the signal from the encoder at a first rate during the start-up period and to receive the signal from the encoder at a second rate after the start-up period, wherein the first rate is greater than the second rate.
• In some implementations, the encoder is an optical encoder including an emitter and receiver pair. The emitter can be arranged to direct a signal toward the pump and the receiver can be arranged to receive the signal reflected from the pump.
• A surface treatment robot includes a robot body, a drive system mounted on the robot body and configured to maneuver the robot over a cleaning surface, and a vacuum assembly carried by the robot body. The vacuum assembly defines an intake conduit and a vacuum chamber in fluid communication with the intake conduit. The vacuum assembly includes a fan in fluid communication with the intake conduit. The fan is configured to draw air through the intake conduit to draw waste liquid from the cleaning surface into the vacuum chamber and a first portion of the fan is disposed in the intake conduit in the path of air drawn through the intake conduit.
• Implementations of one or more of these aspects of the disclosure may include one or more of the following features. In certain implementations, the first portion of the fan disposed in the intake conduit includes a heat sink. In certain implementations, a potting material is disposed about a second portion of the fan. The potting material can have a thermal conductivity greater than the thermal conductivity of air. Additionally or alternatively, the potting material substantially isolates the fan and the intake conduit from fluid communication with the robot body. In certain implementations, a liquid applicator carried by the robot body and defining a liquid storage volume, the liquid applicator configured to dispense a liquid from the liquid storage volume to the cleaning surface, wherein the potting material substantially isolates the fan from fluid communication with the liquid applicator.
• Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.
DESCRIPTION OF DRAWINGS
• FIG. 1 is a schematic block diagram showing the interrelationship of subsystems of an autonomous cleaning robot.
• FIG. 2 is a perspective view of an autonomous cleaning robot.
• FIG. 3 is a bottom view of the autonomous cleaning robot ofFIG. 2.
• FIG. 4 is a side view of the autonomous cleaning robot ofFIG. 2.
• FIG. 5 is a front view of the autonomous cleaning robot ofFIG. 2.
• FIG. 6 is a rear view of the autonomous cleaning robot ofFIG. 2.
• FIG. 7 is an exploded perspective view of the autonomous cleaning robot ofFIG. 2.
• FIG. 8 is a schematic representation of a liquid applicator module of the autonomous cleaning robot ofFIG. 2.
• FIG. 9 is a block diagram of a pump control routine of an autonomous cleaning robot.
• FIG. 10A is a perspective view of a baseplate of the autonomous cleaning robot ofFIG. 2.
• FIG. 10B is a bottom view of the baseplate of the autonomous cleaning robot ofFIG. 2.
• FIG. 10C is a top view of the baseplate of the autonomous cleaning robot ofFIG. 2.
• FIG. 10D is a front view of the baseplate of the autonomous cleaning robot ofFIG. 2.
• FIG. 10E is a side view of the baseplate of the autonomous cleaning robot ofFIG. 2.
• FIG. 11 is a perspective view of an active brush element.
• FIG. 12 is a schematic representation of a vacuum module of an autonomous cleaning robot.
• FIG. 13 is a perspective view of a squeegee of the autonomous cleaning robot ofFIG. 2.
• FIG. 14 is a side view of the squeegee of the autonomous cleaning robot ofFIG. 2.
• FIG. 15 is a bottom view of the squeegee of the autonomous cleaning robot ofFIG. 1.
• FIG. 16 is a block diagram of a method of selecting motors for an autonomous cleaning robot.
• FIG. 17 is an exploded perspective view of a wheel of an autonomous cleaning robot.
• FIG. 18A is a front view of a tire of the wheel ofFIG. 17.
• FIG. 18B is a side view of the tire of the wheel ofFIG. 17.
• FIG. 19 is an exploded perspective view of a signal channeler and omni-directional receiver of an autonomous cleaning robot.
• FIG. 20 is a schematic side view of a potted printed circuit board of an autonomous cleaning robot.
• FIGS. 21A-C are schematic top views of a method of potting a printed circuit board of an autonomous cleaning robot.
• FIG. 22 is a perspective view of a printed circuit board cover of an autonomous cleaning robot.
• FIG. 23 is a perspective exploded view of a printed circuit board cover of an autonomous cleaning robot.
• FIG. 24 is a bottom view of a printed circuit board cover mounted on an autonomous cleaning robot.
• FIG. 25 is a perspective exploded view of a trough of an autonomous cleaning robot.
DETAILED DESCRIPTION
• An autonomous robot may be designed to clean flooring. For example, the autonomous robot may vacuum carpeted or hard-surfaces and wash floors via liquid-assisted washing and/or wiping and/or electrostatic wiping of tile, vinyl or other such surfaces. U.S. application Ser. No. 11/359,961 by Ziegler et al. entitled AUTONOMOUS SURFACE CLEANING ROBOT FOR WET AND DRY CLEANING, the disclosure of which is herein incorporated by reference in its entirety, discloses an autonomous cleaning robot.
• An autonomous robot is movably supported on a surface and is used to clean the surface while traversing the surface. The robot can wet clean the surface by applying a cleaning liquid to the surface, spreading (e.g., smearing, scrubbing) the cleaning liquid on the surface, and collecting the waste (e.g., substantially all of the cleaning liquid and debris mixed therein) from the surface. As compared to comparable-sized autonomous dry cleaning robots, an autonomous wet cleaning robot can remove more debris from a surface.
• FIG. 1 is a schematic block diagram showing the interrelationship of subsystems of an autonomous cleaning robot. Acontroller1000 is powered by apower module1200 and receives inputs from asensor module1100 and aninterface module1700. Thecontroller1000 combines the inputs from thesensor module1100 with information (e.g., behaviors) preprogrammed on thecontroller1000 to control aliquid storage module1500, aliquid applicator module1400, and a collection module1300 (e.g., a dry vacuum module, a wet-dry vacuum module, a woven cloth, a nonwoven cloth and/or a sponge) while also controlling atransport drive1600 to maneuver the autonomous cleaning robot across a cleaning surface (also referred to hereinafter to as a “surface”).
• A controller1000 (e.g., a controller on the robot) controls the autonomous movement of the robot across the surface by directing motion of the drive wheels that are used to propel the robot across the surface. Thecontroller1000 can redirect the motion of the robot in response to any of various different signals from sensors (e.g., sensors carried on the robot, a navigation beacon). Additionally or alternatively, the controller can direct the robot across the surface in a substantially random pattern to improve the cleaning coverage provided by the robot.
• Prior to the cleaning operation, cleaning liquid can be added to theliquid storage module1500 via an external source of cleaning liquid. The robot can then be set on a surface to be cleaned, and cleaning can be initiated through an interface module1700 (e.g., a user interface carried by the robot). Thecontroller1000 controls thetransport drive1600 to maneuver the robot in a desired pattern across the surface. As thecontroller1000 controls the movements of the robot across the surface, the controller also controls aliquid applicator module1400 to supply cleaning liquid to the surface and acollection module1300 to collect waste from the surface. For example, as described below, thecontroller1000 can control theliquid applicator module1400 to dispense at least a portion of the total volume of dispensed liquid rear of thecollection module1300 as thedrive1600 maneuvers the robot in a forward direction over the surface. Thecollection module1300 can collect the dispensed liquid from the surface as the robot returns to the area of the dispensed liquid. Additionally or alternatively, the liquid dispensed rear of thecollection module1300 can remain on the surface (e.g., to evaporate over time).
• After the cleaning operation is complete (e.g., after all of the cleaning liquid has been dispensed from the robot, after the robot has completed a routine, after an elapsed period of time), waste can be removed from the robot. The robot is lightweight and has a compact form factor that each facilitate, for example, handling of the robot such that the robot can be moved to another area to be cleaned or put in storage until a subsequent use. The robot is substantially sealable (e.g., passively sealable, actively sealable) to minimize spillage of cleaning liquid and/or waste from the robot while the robot is in use or while the robot is being handled.
• Referring toFIGS. 2-7, arobot10 includes achassis100 carrying abaseplate200, abumper300, auser interface400, andwheel modules500,501.Wheel modules500,501 are substantially opposed along a transverse axis defined by thechassis100.Baseplate200 is carried on a substantially bottom portion ofchassis100 and at least partially supports a front portion of thechassis100 above the surface. Aswheel modules500,501 propel therobot10 across the surface during a cleaning routine, thebaseplate200 makes slidable contact with the surface and can wet-vacuum the surface by delivering a portion of the cleaning liquid to the surface forward of the wet-vacuum assembly, as described below. Thebaseplate200 can spread the cleaning liquid on the surface, and collect waste from the surface and into the volume defined by therobot10. Auser interface400 is carried on a substantially top portion of thechassis100 and configured to receive one or more user commands and/or display a status of therobot10. Theuser interface400 is in communication with a controller (described in detail below) carried by therobot10 such that one or more commands to theuser interface400 can initiate a cleaning routine to be executed by therobot10. Abumper300 is carried on a forward portion of thechassis100 and configured to detect one or more events in the path of the robot10 (e.g., aswheel modules500,501 propel therobot10 across a surface during a cleaning routine). As described below, therobot10 can respond to events (e.g., obstacles, cliffs, walls) detected by thebumper300 by controllingwheel modules500,501 to maneuver therobot10 in response to the event (e.g., away from the event). While some sensors are described herein as being arranged on the bumper, these sensors can additionally or alternatively be arranged at any of various different positions on therobot10.
• Therobot10 stores cleaning fluid and waste and, thus, substantially the entire electrical system is fluid-sealed and/or isolated from cleaning liquid and/or waste stored on therobot10. Examples of sealing that can be used to separate electrical components of therobot10 from the cleaning liquid and/or waste include covers, plastic or resin modules, potting, shrink fit, gaskets, or the like. Any and all elements described herein as a circuit board, PCB, detector, or sensor can be sealed using any of various different methods. An example of the use of a potting material to isolate electrical components of the robot from the cleaning liquid and/or waste is described below.
• Therobot10 can move across a surface through any of various different combinations of movements relative to three mutually perpendicular axes defined by the chassis: a centralvertical axis20, a fore-aftaxis22 and atransverse axis24. The forward travel direction along the fore-aftaxis22 is designated F (sometimes referred to hereinafter as “forward”), and the aft travel direction along the fore-aftaxis22 is designated A (sometimes referred to hereinafter as “rearward”). The transverse axis extends between a right side, designated R, and a left side, designated L, of therobot10 substantially along an axis defined by center points ofwheel modules500,501. In subsequent figures, the R and L directions remain consistent with the top view, but may be reversed on the printed page.
• In use, a user opens afill door304 disposed along thebumper300 and adds cleaning fluid to the volume within therobot10. After adding cleaning fluid to therobot10, the user then closes thefill door304 such that thefill door304 forms a substantially water-tight seal with thebumper300 or, in some implementations, with a port extending through thebumper300. The user then sets therobot10 on a surface to be cleaned and initiates cleaning by entering one or more commands on theuser interface400.
• The controller carried by therobot10 directs motion of thewheel modules500,501. The controller can control the rotational speed and direction of eachwheel module500,501 independently such that the controller can maneuver therobot10 in any of various different directions. For example, the controller can maneuver therobot10 in the forward, reverse, right, and left directions. For example, as therobot10 moves substantially along the fore-aftaxis22, therobot10 can make repeated alternating right and left turns such that therobot10 rotates back and forth around the center vertical axis20 (hereinafter referred to as a wiggle motion). As described in detail below, such a wiggle motion of therobot10 can allow therobot10 to operate as a scrubber during the cleaning operation. Additionally or alternatively, a wiggle motion of therobot10 can be used by the controller to detect stasis of therobot10. The controller can maneuver therobot10 to rotate substantially in place such that, for example, the robot can maneuver out of a corner or away from an obstacle. In some implementations, the controller directs therobot10 over a substantially random (e.g., pseudo-random) path traversing the surface to be cleaned. The controller is responsive to any of various different sensors (e.g., bump sensors, proximity sensors, walls, stasis conditions, and cliffs) disposed about therobot10. The controller can redirectwheel modules500,501 in response to signals from the sensors such that therobot10 wet vacuums the surface while avoiding obstacles and clutter. If therobot10 becomes stuck or entangled during use, the controller is configured to directwheel modules500,501 through a series of escape behaviors such that therobot10 can resume normal cleaning of the surface.
• Therobot10 is generally advanced in a forward direction during cleaning operations. Therobot10 is generally not advanced in the aft (rear) direction during cleaning operations but may be advanced in the aft direction to avoid an object or maneuver out of a corner or the like. All or a portion of a cleaning operation can continue or be suspended during aft transport. For example, therobot10 can dispense liquid rear of a vacuum assembly as the robot is advanced in a forward direction and can suspend dispensing this liquid as the robot is advanced in the aft direction.
• During wet vacuuming, cleaning liquid can be dispensed to the surface through an applicator mounted directly to the chassis (e.g., to be used as an attachment point for the bumper and/or to conceal wires). Additionally or alternatively, the cleaning liquid can be dispensed to the surface through an applicator mounted to a baseplate. For example, cleaning liquid can be dispensed throughtroughs202a,bcarried on thebaseplate200. Thetrough202ais carried along a substantially forward portion of therobot10, andtrough202bis carried along a substantially rear portion of therobot10 such that thetrough202ais disposed forward of a collection assembly (e.g., a squeegee208) and thetrough202bis disposed rear of the collection assembly. Eachtrough202a,bcan definerespective injection orifices210a,bto produce a spray or drip pattern of cleaning fluid to the surface. For example, a pump upstream of thetrough202a,bcan force cleaning liquid throughinjection orifices210a,bto deliver cleaning liquid to the surface. In some implementations,injection orifices210a,bare substantially equally spaced along the length of eachtrough202a,bto produce a substantially uniform spray pattern of cleaning liquid on the surface. In some embodiments, theinjection orifices210a,bare configured to allow cleaning liquid to drip from theinjection orifices210a,b.
• A wettingassembly204 is carried on thebaseplate200, substantially rearward of thetrough202a. The wettingassembly204 includesrows205 and row206 of bristles substantially forward of thesqueegee208 and row207 of bristles substantially rear of thesqueegee208.Rows205 of bristles extend in a transverse direction substantially the entire width (e.g., diameter) of therobot10. In use, at least a portion of the wettingassembly204 slidably contacts the surface to support a forward portion and/or a rear portion of therobot10 above the cleaning surface. As therobot10 moves in a substantially forward direction, the sliding contact between the wettingassembly204 and the surface spreads the cleaning liquid on the surface. In some implementations, additional rows of bristles and/or other types of wetting elements are carried on thebaseplate200 to further spread and/or agitate the cleaning liquid on the surface. As the robot continues to move forward,wheel modules500,501 pass through the cleaning liquid spread on the surface byrows205 forward of thesqueegee208. A combination of weight distribution (e.g., drag) of therobot10, material selection and tread geometry for the tires of thewheel modules500,501, and a biased-to-drop suspension system improve the traction ofwheel modules500,501 through the cleaning liquid such thatwheel modules500,501 can pass over the cleaning liquid without substantial slipping and can navigate small obstacles (e.g., grout lines, tile edges, etc.) that may be wet.
• Asqueegee208 formed with a longitudinal ridge is carried on thebaseplate200 and, during use, extends from thebaseplate200 to movably contact the surface. Thesqueegee208 is positioned substantially rearward of thewheel modules500,501. As compared to a robot including a squeegee in a more forward position, such rearward positioning of thesqueegee208 can increase the dwell time of the cleaning liquid dispensed through thetrough202aon the surface and, thus, increase the effectiveness of the cleaning operation. Additionally or alternatively, such a rearward positionedsqueegee208 can stabilize therobot10 by reducing rearward tipping of therobot10 in response to thrust created by thewheel modules500,501 propelling therobot10 in a forward direction. In another example, the rearward positionedsqueegee208 can stabilize therobot10 by reducing rearward tipping of therobot10 as therobot10 climbs a grout line. In yet another example,squeegee208 has about 0.25 mm to about 0.75 mm of interference with the cleaning surface such that thesqueegee208 biases the weight of therobot10 toward the forward direction as therobot10 maneuvers over an obstacle. In some implementations, thesqueegee208 is movable away from the cleaning surface by about 2 mm to about 4 mm to facilitate, for example, movement of therobot10 over an obstacle such as a grout line.
• As described in detail below, the movable contact between thesqueegee208 acts to lift waste (e.g., a mixture of cleaning liquid and debris) from the cleaning surface as therobot10 is propelled in a forward direction. Thesqueegee208 is configured to pool the waste substantially nearsuction apertures262 defined by thesqueegee208. A vacuum assembly carried by therobot10 suctions the waste from the cleaning surface and into therobot10, leaving behind a wet vacuumed surface.
• After all of the cleaning fluid has been dispensed from therobot10, the controller stops movement of therobot10 and provides an alert (e.g., a visual alert or an audible alert) to the user via theuser interface400. The user can then open anempty door104 to expose a waste port defined by the waste collection volume remove collected waste from therobot10. Because thefill door304 and theempty door104 are disposed along substantially opposite sides of the chassis, thefill door304 and theempty door104 can be opened simultaneously to allow waste to drain out of therobot10 while cleaning liquid is added to therobot10.
• If the user wishes to move therobot10 between uses, the user may move (e.g., rotate) ahandle401 away from thechassis100 and lift therobot10 using thehandle401. Thehandle401 can pivot about a transverse axis (e.g., a center transverse axis) including the center of gravity of therobot10 such that thehandle401 can be used to carry therobot10 substantially like a pail. Therobot10 includes a sealing system601 (e.g., a passive sealing system and/or an active sealing system) such that therobot10 remains substantially water-tight during transport. Thesealing system601 can reduce the escape of waste and/or cleaning fluid from therobot10 as the robot is moved from one area to another. Accordingly, therobot10 can be moved and stored with little risk of creating hazardous, slippery conditions resulting from liquid dripping from the robot. Additionally or alternatively, therobot10 can be moved and stored with little risk of dripping liquid on the user or on surfaces that have already been cleaned.
• After moving therobot10, the user can position thehandle401 back into a position substantially flush with the top portion of the robot to reduce the potential for thehandle401 becoming entangled with an object while therobot10 is in use. In some implementations, thehandle401 can be magnetized to bias thehandle401 toward a position flush with the top portion of the robot. In some implementations, thehandle401 includes a spring that biases thehandle401 toward a position substantially flush with the top portion of therobot10.
• Between uses, the user can recharge a power supply carried on-board therobot10. To charge the power supply, the user can open acharge port door106 on a back portion of thechassis100. With thecharge port door106 open, the user can connect a wall charger to a charge port behind thecharge port door106. The wall charger is configured to plug into a standard household electrical outlet. During the charging process, one or more indicators (e.g., visual indicators, audible indicators) on theuser interface400 can alert the user to the state of charge of the power supply. Once the power supply has been recharged (e.g., as indicated by the user interface400), the user can disconnect therobot10 from the wall charger and close thecharge port door106. Thecharge port door106 forms a substantially water-tight seal with thechassis100 such that the charge port remains substantially free of liquid when thecharge port door106 is closed. In some implementations, the power supply is removed from therobot10 and charged separately from therobot10. In some implementations, the power supply is removed and replaced with a new power supply. In some implementations, therobot10 is recharged through inductive coupling between therobot10 and an inductive transmitter. Such inductive coupling can improve the safety of therobot10 by reducing the need for physical access to electronic components of therobot10.
• Form Factor
• Thechassis100,baseplate200,bumper300,user interface400, andwheel modules500,501 fit together such thatrobot10 has a substantially cylindrical shape with a top surface and a bottom surface that is substantially parallel to and opposite the top surface. Such a substantially cylindrical shape can reduce the potential for therobot10 to become entangled (e.g., snagged) and/or break on obstacles as therobot10 traverses a surface.
• In some implementations, the substantially cylindrical shape of therobot10 has a form factor that allows a user to lift and manipulate therobot10 in a manner similar to the manipulation of a typical canteen carried by hikers. For example, a user can fill therobot10 with cleaning liquid by placing therobot10 under a typical bathroom or kitchen faucet. With therobot10 in the same orientation used to fill the robot with cleaning liquid, the robot can be emptied into the bathroom or kitchen sink. Therobot10 includes afront face302 and aback face102, each of which are substantially flat and configured to balance therobot10 on end. For example, a user can place back face102 on a substantially flat surface (e.g., a countertop, bottom of a kitchen sink, bottom of a bathtub) such that therobot10 is balanced on the countertop withfront face302 facing upward toward the user. Such an orientation can allow a user to fill therobot10 with cleaning liquid without holding the robot. Additionally or alternatively, a user can placefront face302 on a substantially flat surface to allow a user to more easily access components of the robot10 (e.g., a battery compartment, a charging port).
• Therobot10 performs cleaning operations in tightly dimensioned areas. In some implementations, therobot10 can have a compact form factor for avoiding clutter or obstacles while dispensing liquid on a surface and/or removing waste from the surface. For example, therobot10 can be dimensioned to navigate household doorways, under toe kicks, and under many typical chairs, tables, portable islands, and stools, and behind and beside some toilets, sink stands, and other porcelain fixtures. In certain implementations, the overall height of therobot10 is less than a standard height of a toe-kick panel of a standard North American bathroom vanity. For example, the overall height of therobot10 can be less than about 18 centimeters (e.g., about 15 centimeters, about 12 centimeters, about 9 centimeters). In certain implementations, the overall diameter of therobot10 is approximately equal to the standard distance between the base of an installed toilet and a bathroom wall. As compared to larger diameter robots, such a diameter of therobot10 can improve cleaning around the base of a toilet, e.g., substantially between the toilet and the wall. For example, the overall diameter of therobot10 can be less than about 26 centimeters (e.g., about 12-18 cm to permit, for example, going behind many bathroom surfaces not reachable by conventional robots). In certain implementations, thewheel modules500,501 are configured to maneuver therobot10 in such tightly dimensioned spaces (e.g., in a volume of less than about 3 L).
• While therobot10 is described as having a substantially cylindrical shape in the range of dimensions described above, therobot10 can have other cross-sectional diameter and height dimensions, as well as other cross-sectional shapes (e.g. square, rectangular and triangular, and volumetric shapes, e.g. cube, bar, and pyramidal) to facilitate wet cleaning narrow or hard-to-reach surfaces.
• Within a given size envelope, larger volumes of cleaning liquid can be stored by reducing, for example, the volume required for the other functions (e.g., liquid dispensing, collecting) of therobot10. For example, the volume of cleaning liquid that can be stored can be increased by increasing the fraction of cleaning liquid dispensed rear of thesqueegee208 as the robot moves in the forward direction such that a larger portion of the dispensed cleaning liquid can evaporate before therobot10 can return to collect the cleaning liquid. In some implementations, therobot10 carries a volume of cleaning fluid that is at least about 20 percent (e.g. at least about 30 percent, at least about 40 percent) of the volume of therobot10.
• Physics and Mobility
• Therobot10 is configured to clean approximately 150 square feet of cleaning surface in a single cleaning operation. A larger or smaller tank may permit this to range from 100 square feet to 400 square feet. The duration of the cleaning operation is approximately 45 minutes. In implementations with smaller, larger, or 2 or more batteries on board, the cleaning time can range down to 20 minutes or up to 2 hours. Accordingly, therobot10 is configured (physically, and as programmed) for unattended autonomous cleaning for 45 minutes or more without the need to recharge a power supply, refill the supply of cleaning fluid or empty the waste materials collected by the robot.
• In implementations in which therobot10 is configured to collect substantially all of the cleaning fluid delivered to the surface upstream of thesqueegee208 in a single pass, the average forward travel speed of therobot10 can be a function of the cleaning quality and/or the surface coverage area required for a given implementation. For example, slower forward travel speeds can allow a longer soak time (e.g., longer contact time) between the cleaning fluid (e.g., cleaning fluid dispensed throughtrough202a) and the debris on the surface such that the debris can be more easily removed from the surface through suction with thesqueegee208. In some implementations, the average forward travel speed of therobot10 can be increased by dispensing at least some of the cleaning liquid rear of the squeegee as the robot moves in the forward direction.
• Additionally or alternatively, faster forward travel speeds can allow therobot10 to clean a larger surface area before requiring refilling with cleaning liquid and/or recharging the power supply. Accordingly cleaning quality and surface coverage that is acceptable to consumers is achieved by configuring therobot10 to dispense between about 30 percent and about 70 percent (e.g., about 60 percent by volume) of a cleaning liquid through thetrough202aforward of the squeegee, dispensing at least about 30 percent (e.g., about 40 percent by volume) of the cleaning liquid through thetrough202brear of the squeegee, and allowing between about 0.3 and about 0.7 seconds of contact between the cleaning liquid dispensed throughtrough202aand the surface before the cleaning liquid dispensed through thetrough202ais collected into therobot10 throughsqueegee208. In some implementations, substantially all of the liquid dispensed through thetrough202ais collected (e.g., vacuumed) through thesqueegee208. Additionally or alternatively, therobot10 may return to collect at least a portion of the liquid dispensed through thetrough202b. Given that the liquid dispensed through thetrough202aand collected throughsqueegee208 cleans the surface in advance of application of liquid through thetrough202bas the robot moves in the forward direction, the liquid dispensed through thetrough202bis dispensed onto a substantially clean surface and, therefore, may be left on the cleaning surface to evaporate.
• In one example, when therobot10 has a diameter of about 17 centimeters and travels at a forward rate of about 25 centimeters/second, the contact time between the cleaning liquid and the surface is about 0.25 to about 0.6 seconds, the variation in contact time depending on the positioning of the cleaning fluid distribution relative to the forward edge of therobot10 and the positioning of the collection assembly (e.g., squeegee208) relative to the rearward edge of the robot.
• In some implementations, therobot10 thecontroller1000 is configured to allow therobot10 to subsequently return (e.g., through navigation) to collect from the surface at least some of the cleaning liquid dispensed, throughtrough202b, rear of thesqueegee208. For example, therobot10 may make multiple passes over the cleaning surface to collect at least a portion of the liquid left on the cleaning surface. As compared to dispensing all of the cleaning liquid forward of the squeegee208 (e.g., throughtrough202a), dispensing at least some of the cleaning liquid rear of thesqueegee208 allows cleaning liquid to be left on the surface for a longer period of time (e.g., to allow the cleaning liquid to react chemically with debris on the surface) while therobot10 travels at a higher rate of speed. Thecontroller1000 allows therobot10 to return to positions where the cleaning fluid has been deposited on the surface but not yet collected. In some implementations, thecontroller1000 can maneuver the robot in a pseudo-random pattern across the surface such that the robot is likely to return to the portion of the surface upon which cleaning fluid has remained.
• As described above, the transverse distance betweenwheel modules500,501 (e.g., the wheel base of robot10) is substantially equal to the transverse cleaning width (e.g., the transverse width of the wettingassembly204. Thus, during a cleaning operation,wheel modules500,501 are configured to grip a portion of the surface, including obstacles such as grout lines that may form part of the surface, covered with cleaning liquid. With sufficient traction force, thewheel modules500,501 can propel therobot10 through the cleaning liquid. With insufficient traction force, however, thewheel modules500,501 can slip on the cleaning liquid and therobot10 can become stuck in place. As described below, thewheel modules500,501 include tires with a surface roughness sufficient to penetrate the surface tension of the cleaning liquid on the surface to facilitate gripping the surface. As also described below, thewheel modules5001,501 include tires with tread patterns that facilitate gripping small obstacles (e.g., the edges) to propel therobot10 over such small obstacles.
• Heavier robots can apply sufficient pressure at wheels to avoid slipping as the wheels pass over the cleaning liquid. As compared to lighter robots, however, heavier robots are more difficult to handle (e.g., for refilling at a sink, for carrying to storage). Accordingly, therobot10 is configured to weigh less than 3 kg (fully loaded with cleaning liquid) whilewheel modules500,501 provide sufficient traction to propelrobot10 through cleaning liquid on distributed on the surface.
• In some implementations, the center of gravity of therobot10 is substantially along thetransverse axis24 such that much of the weight of therobot10 is over thewheel modules500,501 during a cleaning operation. Such a weight distribution ofrobot10 can exert a sufficient downward force onwheel modules500,501 to overcome slippage while also allowingwheel modules500,501 to overcome drag forces created as wettingassembly204 andsqueegee208 movably contact the surface. In some implementations, the weight of the robot is distributed to overcome such drag forces while applying sufficient cleaning pressure to the surface (e.g., sufficient pressure to wettingassembly204 and squeegee208). For example, thewheel modules500,501 can support about 50% to about 70% of the weight of therobot10 above the surface. The wettingassembly204 can support at least about 10% of the weight of the robot above the surface, along the forward portion of the robot. Thesqueegee208 can support at least about 20% of the weight of the robot above the surface, along the rearward portion of the robot. As described in detail below, the supply volume and the collection volume are configured to maintain the center of gravity of the robot substantially over thetransverse axis24 while at least about 25 percent of the total volume of the robot shifts from cleaning liquid in the supply volume to waste in the collection volume as the cleaning cycle progresses from start to finish.
• In certain implementations, a robot of between 12-18 cm in diameter and less than 15 cm high is between 1-2 kg when full of fluid, the volume being largely occupied by water (specific gravity 1), plastic (close to specific gravity 1) and a few heavier components (ballast, motors, batteries). Exemplary ranges for physical dimensions of a robot intended to reach narrower bathroom areas (such as beside toilets) include: a full mass of 0.5-4 kg; a cleaning width of 5 cm-20 cm within a diameter of 10-20 cm; a wheel diameter 1.5 cm-8 cm; drivewheel contact line 1 cm-3 cm for all drive wheels (two, three, four drive wheels); drive wheel contact patch for all wheels 0.5-1.5 cm²or higher.
• Therobot10 can be less than about 0.5 kg empty, and less than approximately 3 kg full, and carry about 0.5 kg to about 2.5 kg (or 500-2500 ml) of clean or dirty fluid (in the case where the robot applies fluid as well as picks it up). The waste tank can be sized according to the efficiency of the pick-up process and/or according to the fraction of liquid dispensed rear of thesqueegee208. For example, with a comparatively inefficient squeegee designed to or arranged to leave a predetermined amount of wet fluid on each pass (e.g., so that the cleaning fluid can dwell and progressively work on stains or dried food patches), the waste tank can be designed to be equal in size or smaller than the clean tank. A portion of the deposited fluid will never be picked up, and another portion will evaporate before it can be picked up. In an additional or alternative example, at least a portion of the liquid dispensed rear of thesqueegee208 will evaporate before therobot10 returns to pick up this dispensed liquid and, in some instances, therobot10 may not return to pick up the dispensed liquid. In implementations in which an efficient squeegee is used (e.g., silicone) and substantially all of the cleaning liquid is dispensed forward of thesqueegee208, then it may be necessary to size the waste tank to be equal to or bigger than the clean fluid tank. A proportion of the tank volume, e.g., 5% or higher, may also be devoted to foam accommodation or control, which can increase the size of the waste tank.
• To effectively brush, wipe, or scrub the surface, the wettingassembly204 and thesqueegee208 create drag that acts to agitate debris on the surface. For a robot under 3 kg, the wetting assembly204 (e.g.,rows205,row206, and row207 of bristles) should have a length, stiffness, and height to balance (whether full or empty) at least about ⅓ of the empty weight of the robot per wheel (e.g., for an empty robot of 1 kg, at least 300 weight borne by each wheel). Drag forces (total drag associated with any blades, squeegees, dragging components such as bristles) should not exceed 25% of robot weight to ensure good mobility in the absence of active suspensions/constant weight systems, as any lifting will otherwise remove weight from the tires and affect motive force. Maximum available traction typically is no more than about 40% of robot weight on slick surfaces with a surfactant based (low surface tension) cleaning fluid, perhaps as high as 50% in best case situations, and traction/thrust must exceed drag/parasitic forces. However, in order to successfully navigate autonomously, to have sufficient thrust to overcome minor hazards and obstacles, to climb thresholds which may encounter the scrubbing or brushing member differently from the wheels, and to escape from jams and other panic circumstances, therobot10 can have a thrust/traction, provided mostly by the driven wheels, of about 150% or more of average drag/parasitic force. In implementations including a rotating brush, depending on the direction of rotation, the rotating brush can create drag or thrust.
• In some implementations, therobot10 has a weight of about 1.4 kg fully loaded, with less than about 100 gram-force of drag (on a surface with a static coefficient of friction of about 0.38) caused by the wettingassembly204 and less than about 320 gram-force of drag (on a surface with a static coefficient of friction of about 0.77) caused by thesqueegee208, but more than 1100 gram-force of thrust contributed bywheel modules500,501 to propel therobot10 at a maximum forward rate of about 200 mm/s to about 400 mm/s. In certain implementations, weight is added to therobot10 to improve traction ofwheel modules500,501 by putting more weight on the wheels (e.g., metal handle, clevis-like pivot mount, larger motor than needed, and/or ballast in one embodiment of the present device). With or without added weight, in some implementations, the robot can include a rotating brush and derive a functional percentage of thrust from a forwardly rotating brush (which is turned off generally in reverse), which is not a feature needed in a large industrial cleaner.
• The width of the cleaning head for the mass of a household cleaning robot, under 10 kg (or even under 20 kg), differs from industrial self-propelled cleaners. This is especially true for wet cleaning. In some implementations, therobot10 has at least about 1 cm of (wet) cleaning width for every 1 kg of robot mass (e.g., about 4, 5, or 6 cm of cleaning width for every 1 kg of robot mass), and up to about 20 cm of cleaning width for every kg of robot mass (the higher ratios generally apply to lower masses). For example, therobot10 can weigh approximately 1.5 kg when fully loaded with cleaning liquid and can have a wet cleaning width of about 16.5 cm, such that therobot10 can have about 11 cm of wet cleaning width for every 1 kg of robot mass.
• In implementations in which cleaning liquid is dispensed rear of thesqueegee208 to remain on the cleaning surface as therobot10 moves in the forward direction, larger cleaning widths per kg are possible. In such implementations, the use of mechanical agitation (e.g., wiping or scrubbing force) to remove debris from the cleaning surface is augmented by the increased chemical reactivity between cleaning liquid and the debris on the cleaning surface. For example, the increased time available for the liquid to remain in contact with the debris can increase the amount of chemical reaction that occurs between the cleaning liquid and the debris. Thus, as compared to implementations in which all of the cleaning liquid is dispensed forward of thesqueegee208 and is collected by thesqueegee208, larger cleaning widths for every kg of robot mass can result in effective cleaning of the surface. Thus, in implementations in which at least about 30 percent of the total dispensed volume of the cleaning liquid is dispensed rear of a collection assembly (e.g., rear of the squeegee208), the robot can have up to about 50 cm of cleaning width for every kg of robot mass. For example, by dispensing higher percentages of cleaning fluid rear of the squeegee, higher ratios of cleaning width to robot mass can be used to achieve effective cleaning of the surface.
• Lower cleaning widths per 1 kg of robot mass can lead to either an ineffective cleaning width or a very heavy robot unsuitable for consumer use, i.e., that cannot be carried easily by an ordinary (or frail) person. Self-propelled industrial cleaning machines typically have ⅓ cm of cleaning width or less per kg machine mass.
• Ratios of these dimensions or properties determine whether a robot under 5 kg, and in some cases under 10 kg, will be effective for general household use. Although some such ratios are described explicitly above, such ratios (e.g., cm squared area of wheel contact per kg of robot mass, cm of wheel contact line per kg-force of drag, and the like) are expressly considered to be inherently disclosed herein, albeit limited to the set of different robot configurations discussed herein.
• In certain implementations, therobot10 includes tires having a 3 mm foam tire thickness with 2 mm deep sipes. This configuration performs best when supporting no more than 3 to 4 kg per tire. The ideal combination of sipes, cell structure and absorbency for a tire is affected by robot weight. In some implementations, rubber or vinyl tires are configured with surface features to reduce slippage.
• As indicated above, therobot10 includes the wettingassembly204 and thecollection assembly1300 including, for example, thesqueegee208. In some implementations, a wet vacuum portion can be closely followed by a longitudinal ridge of thesqueegee208 to build up the thickness of a deposited water film for pick-up. Thesqueegee208 can have sufficient flexibility and range of motion to clear any obstacle taller than 2 mm, but ideally to clear the ground clearance of the robot (e.g., about a 4½ mm minimum height or the ground clearance of the robot).
• Any reactionary force exhibited by thesqueegee208 that is directionally opposite to gravity, i.e., up, subtracts from available traction and should be less than about 20% of robot weight (e.g., less than about 10% of robot weight). A certain amount of edge pressure, which has an equal reactionary force, is necessary for thesqueegee208 to wipe and collect fluid. In order to obtain an effective combination of fluid collection, reactionary force, wear, and flexible response to obstacles, the physical parameters of the squeegee are controlled and balanced. In certain implementations, thesqueegee208 includes a working edge radius of 3/10 mm for a squeegee less than 300 mm. In some implementations, thesqueegee208 can have a working edge of about 1/10 to 5/10 mm. Wear, squeegee performance and drag force can be improved with a squeegee of substantially rectangular cross section (optionally trapezoidal) and/or 1 mm (optionally about ½ mm to 1½ mm) thickness, 90 degree corners (optionally about 60 to 120 degrees), parallel to the floor within ½ mm over its working length (optionally within up to ¾ mm), and straight to within 1/500 mm per unit length (optionally within up to 1/100), with a working edge equal to or less than about 3/10 mm as noted above. Deviations from the above parameters can require greater edge pressure (force opposite to gravity) to compensate, thus decreasing available traction.
• The wettingassembly204 and thesqueegee208 are configured to contact the floor over a broad range of surface variations (e.g., in wet cleaning scenarios, including tiled, flat, wood, deep grout floors). In some implementations, the wettingassembly204 and/or thesqueegee208 are mounted using a floating mount (e.g., on springs, elastomers, guides, or the like) to improve contact with the broad range of surface variations. In certain implementations, the wettingassembly204 and thesqueegee208 are mounted to thechassis100 with sufficient flexibility for the designed amount of interference or engagement of the wettingassembly204 and/or thesqueegee208 to the surface. As described above, any reactionary force exhibited by the brushes/scrubbing apparatus that is opposite to gravity (up) subtracts from available fraction and should not exceed 10% of robot weight.
• In certain implementations, the robot includes more than one brush, e.g., two counter-rotating brushes with one or more brush on either fore-aft side of the center line of the robot, or more. The robot can also include a differential rotation brush such that two brushes, each substantially half the width of the robot at the diameter of rotation, are placed on either lateral side of the fore-aftaxis22, each extending along half of the diameter. Each brush can be connected to a separate drive and motor, and can rotate in opposite directions or in the same direction or in the same direction, at different speeds in either direction, which would provide rotational and translational impetus for the robot.
• The center of gravity of therobot10 will tend to move during recovery of fluids unless the cleaner and waste tanks are balanced to continually maintain the same center of gravity location. Maintaining the same center of gravity location (by tank compartment design) can allow a passive suspension system to deliver the maximum available traction. Therobot10 includes a tank design that includes a first compartment having a profile that substantially maintains the position of the compartment center of gravity as it empties, a second compartment having a profile that substantially maintains the position of the compartment center of gravity as it fills, wherein the center of gravity of the combined tanks is maintained substantially within the wheel diameter, as viewed from the top of therobot10, and over the wheels, as viewed from the side of therobot10. In some implementations, therobot10 includes tanks stacked in a substantially vertical direction and configured to maintain the same location of the center of gravity of therobot10.
• In certain implementations, absent perfect fluid recovery or active suspension, superior mobility is achieved either by modeling or assuming a minimum percentage of fluid recovered across all surfaces (70% of fluid put down for example) and designing the profile of the compartments and center of gravity positions according to this assumption/model. In some implementations, superior mobility is achieved by assuming perfect (or near perfect) fluid and dispensing least about 30 percent by volume of cleaning liquid is dispensed rear of thesqueegee208 as the robot moves in the forward direction and designing the profile of the compartments and the center of gravity positions based on this configuration. In the alternative, or in addition, setting spring force equal to the maximum unladen (empty tank) condition can contribute to superior traction and mobility. In some implementations, suspension travel is at least equal the maximum obstacle allowed by the bumper (and other edge barriers) to travel under the robot.
• Maximizing the diameter of the wheels of the robot can decrease the energy and traction requirements for a given obstacle or depression. In certain implementations, maximum designed obstacle climbing capability should be 10% of wheel diameter or less. A 4.5 mm obstacle or depression should be overcome or tackled by a 45 mm diameter wheel. In certain implementations, the clearance of the robot is low for several reasons. The bumper is set low to distinguish between carpet, thresholds, and hard floors such that abumper 3 mm from the ground will prevent the robot from mounting most carpets (2-5 mm bumper ground clearance, 3 mm being preferable). The remainder of the robot working surface, e.g., the collection assembly, also have members extending toward the floor (air guides, squeegees, brushes) that are made more effective by a lower ground clearance. Because the ground clearance of one embodiment is between 3-6 mm, the wheels need only be 30 mm-60 mm. Other wheel sizes can also be used.
• Assembly
• Referring toFIG. 7,chassis100 carries aliquid volume600 substantially along an inner portion of thechassis100. As described in detail below, portions of theliquid volume600 are in fluid communication with liquid delivery and air handling systems carried on thechassis100 to allow cleaning fluid to be pumped from theliquid volume600 and to allow waste to be suctioned into theliquid volume600. To allow the addition of cleaning liquid and the removal of waste,liquid volume600 can be accessed through fill door304 (not shown inFIG. 7) andempty door104.
• Thewheel modules500,501 includerespective drive motors502,503 andwheels504,505. Thedrive motors502,503 releasably connect to thechassis100 on either side of theliquid volume600 with thedrive motors502,503 positioned substantially overrespective wheels504,505. In some implementations, drivemotors502,503 are positioned substantially horizontal torespective wheels504,505 to increase the size of theliquid volume600 carried onchassis100. In some implementations,wheel modules500,501 are releasably connected tochassis100 and can be removed without the use of tools to facilitate, for example, repair, replacement, and cleaning of thewheel modules500,501. Asignal channeler402 is connected to a top portion ofchassis100 and substantially covers theliquid volume600 to allow components to be attached along a substantially top portion of therobot10. Anedge404 of the signal channeler is visible from substantially the entire outer circumference of therobot10 to allow thesignal channeler404 to receive a light signal (e.g., an infrared light signal) from substantially any direction. As described in detail below, thesignal channeler402 receives light from a light source (e.g., a navigation beacon) and internally reflects the light toward a receiver disposed within thesignal channeler402. For example, thesignal channeler402 can be at least partially formed of a material (e.g., polycarbonate resin thermoplastic) having an index of refraction of about 1.4 or greater to allow substantially total internal reflection within the signal channeler. Additionally or alternatively, thesignal channeler402 can include a first mirror disposed along a top surface of thesignal channeler402 and a second mirror disposed along a bottom surface of thesignal channeler402 and facing the first mirror. In this configuration, the first and second mirrors can internally reflect light within thesignal channeler402.
• Thesignal channeler402 includes a recessedportion406 that can support at least a portion of theuser interface400. A user interface printed circuit board (PCB) can be arranged in the recessedportion406 and covered by a membrane and/or a potting material, to form a substantially water-tight user interface400. As described in detail below, a bottom portion ofsignal channeler402 can form a top portion of theliquid volume600.
• Bumper300 connects to thehinges110 arranged substantially along the forward portion of thechassis100. The hinged connection betweenbumper300 andchassis100 can allow the bumper to move a short distance relative to thechassis100 when thebumper300 contacts an obstacle.Bumper300 is flexibly connected to afill port602 of theliquid volume600 such that thebumper300 and thefill port602 can flex relative to one another as thebumper300 moves relative to thechassis100 upon contact with an obstacle.
• Thebumper300 includes a substantiallytransparent section306 near a top portion of the bumper. Thetransparent section306 can extend substantially along the entire perimeter of thebumper300. Thetransparent section306 can be substantially transparent to a signal receivable by an omni-directional receiver disposed substantially near a center portion of thesignal channeler402 such that the omni-directional receiver can receive a signal from a transmitter positioned substantially forward of thebumper300.
• Thebaseplate200 is carried on a substantially bottom portion ofchassis100. Thebaseplate200 includes pivot hinges212 that extend from a forward portion of thebaseplate200 and can allow thebaseplate200 to be snapped into complementary hinge features on thechassis100. In some implementations, a user can unhinge thebaseplate200 from thechassis100 without the use of tools. Thebaseplate200 defines at least a portion of thetrough202balong a rear portion of therobot10. The wettingassembly204 is substantially rearward of thetrough202a. Thebaseplate200 extends around a portion of eachwheel module500,501 to form portion of wheel wells forwheels504,505, substantially rearward of the wettingassembly204. Rearward of thewheels504,505, thebaseplate200 carries a collection assembly including thesqueegee208 configured in slidable contact with the surface to pool waste near the contact edge between thesqueegee208 and the surface. As described in detail below, thesqueegee208 defines a plurality of orifices substantially near the contact edge between thesqueegee208 and the surface. Thecollection assembly1300 can create suction such that waste is lifted from the surface and into therobot10 through the plurality of orifices defined by thesqueegee208.
• In some implementations, a user can unhinge thebaseplate200 from thechassis100 in order to clean thebaseplate200. In certain implementations, the user can remove thetrough202b, the wettingassembly204, and/or thesqueegee208 from thebaseplate200 to repair or replace these components. Additionally or alternatively, as described below, a portion of thesqueegee208 can be unattached to the baseplate such that the user can move the unattached portion of thesqueegee208 to facilitate cleaning and, during use, negative pressure created by a vacuum holds the unattached portion of thesqueegee208 in place relative to thebaseplate200.
• Liquid Storage
• Referring toFIG. 8, in some implementations,liquid volume600 can function as both a liquid supply volume S and a waste collection volumeW. Liquid volume600 is configured such that liquid moves from the liquid supply volume S to the surface and then is picked up and returned to a waste collection volume W. In some implementations, the supply volume S and the waste collection volume W are configured to maintain a substantially constant center of gravity along the transverse axis24 (seeFIG. 2) while at least 25 percent of the total volume of therobot10 shifts from cleaning liquid in the supply volume S to waste in the collection volume W as cleaning liquid is dispensed from the applicator and waste is collected by the vacuum assembly.
• In some implementations, all or a portion of the supply volume S is a flexible bladder within the waste collection volume W and surrounded by the waste collection volume W such that the bladder compresses as cleaning liquid exits the bladder and waste filling the waste collection volume W takes place of the cleaning liquid that has exited the bladder. Such a system can be a self-regulating system which can keep the center of gravity of therobot10 substantially in place (e.g., over the transverse axis24). For example, at the start of a cleaning routine, the bladder can be full such that the bladder is expanded to substantially fill the waste collection volume W. As cleaning liquid is dispensed from therobot10, the volume of the bladder decreases such that waste entering the waste collection volume W replaces the displaced cleaning fluid that has exited the flexible bladder. Toward the end of the cleaning routine, the flexible bladder is substantially collapsed within the waste collection volume W and the waste collection volume is substantially full of waste.
• In some implementations, the maximum volume of the flexible bladder (e.g., the maximum storage volume of cleaning liquid) is substantially equal to the volume of the waste collection volume W. In certain implementations, the volume of the waste collection volume W is larger (e.g., about 10 percent to about 20 percent larger) than the maximum volume of the flexible bladder. Such a larger waste collection volume W can allow therobot10 to operate in an environment in which the volume of the waste collected is larger than the volume of the cleaning liquid dispensed forward of the collection assembly (e.g., when therobot10 maneuvers over substantial spills).
• While the supply volume S has been described as a flexible bladder substantially surrounded by the waste collection volume W, other configurations are possible. For example, the supply volume S and the waste collection volume W can be compartments that are stacked or partially stacked on top of one another with their compartment-full center of gravity within 10 cm of one another. Additionally or alternatively, the supply volume S and the waste collection volume W can be concentric (concentric such that one is inside the other in the lateral direction); or can be interleaved (e.g., interleaved L shapes or fingers in the lateral direction).
• Liquid Applicator
• Referring toFIGS. 3 and 8, aliquid applicator module1400 applies a first volume of cleaning liquid onto the surface, throughtrough202a, forward of therows205 androw206 and applies a second volume of cleaning liquid onto the surface, throughtrough202b, rear of therows205 androw206 and forward of therow207 as therobot10 moves in the forward direction. In some implementations, the second volume of cleaning liquid is at least about 30 percent (e.g., about 50 percent) of the total volume of cleaning liquid dispensed by theliquid applicator module1400 to the surface, and the first volume of cleaning liquid can be about 30 percent to about 70 percent of the total volume of liquid dispensed by theliquid applicator module1400. For example, the first volume can be about 60 percent of the total volume of liquid dispensed by theliquid applicator module1400 and the second volume can be about 40 percent of the total volume of liquid dispensed by the liquid applicator module. This ratio can result in superior cleaning of the surface by allowing the first volume of cleaning liquid to be mechanically agitated (e.g., byrows205 and/or row206 of bristles) in contact with debris on the surface and the second volume of cleaning liquid can remain on the cleaning surface to react chemically with debris that may remain on the cleaning surface after the first volume of cleaning liquid has been removed from the surface.
• The liquid applicator module can spray the floor directly, spray a fluid-bearing brush or roller, or apply fluid by dripping or capillary action to the floor, brush, roller, or pad. Theliquid applicator module1400 receives a supply of cleaning liquid from a supply volume S within theliquid volume600 carried by thechassis100. In some implementations, the liquid of the composition of the liquid of the first volume of cleaning liquid is the same as the composition of the liquid of the second volume of cleaning liquid. In certain implementations, the liquid of the first volume of cleaning liquid differs in composition from the liquid of the second volume of cleaning liquid. For example, the liquid of the second volume of cleaning liquid can be water.
• A pump240 (e.g., a peristaltic pump) pumps the cleaning fluid through theliquid applicator module1400, through one ormore injection orifices210a,bdefined by thetrough202aand thetrough202b(see, e.g.FIG. 3). In some implementations, thepump240 pumps liquid to thetrough202aand thetrough202band the relative distribution of cleaning liquid between the troughs is achieved by adjusting the total open area of theorifices210a,bdefined by each respective trough. Eachinjection orifice210a,bis oriented to dispense cleaning liquid toward the cleaning surface. For example, at least a portion of theinjection orifices210a,bcan be oriented to dispense cleaning liquid toward the cleaning surface, in a direction substantially toward the forward direction of travel of therobot10. Additionally or alternatively, at least a portion of theinjection orifices210a,bcan be oriented to spray cleaning liquid toward the cleaning surface, in a direction substantially toward the rear of therobot10. The size oforifices210a,band the delivery pressure ofpump240 can be any of various different combinations such that the fluid can be dispensed toward the cleaning surface in a drip (e.g., with substantially large droplets and/or substantially continuous flow) and/or in a spray. For example, theorifices210bcan be sized to be one or more spray nozzles, dispensing substantially atomized droplets of cleaning liquid toward the cleaning surface rear of thesqueegee208. Such atomization facilitate exposure of a large surface area of the cleaning liquid to air, thus facilitating evaporation of the cleaning liquid. Additionally or alternatively, in another example, theorifices210bcan be sized to drip cleaning liquid toward the cleaning surface rear of thesqueegee208.
• The speed of thepump240 can be determined based at least in part on a signal received anencoder605. For example, the encoder can be an optical encoder including an emitter/receiver pair, with the emitter arranged to direct a signal toward thepump240 and the receiver arranged to receive the signal reflected from thepump240. Additionally or alternatively, thecontroller1000 can be in communication with theencoder605 and configured to receive a signal from theencoder605 to determine speed of thepump240 as a function of voltage supplied to the pump.
• Referring toFIGS. 5,7,8, and9, encoderless pumping1002 includes receiving1004asignal from an encoder (e.g., encoder605) directed at a pump, determining1006 the speed of the pump as a function of voltage supplied to the pump during a start-up period, and controlling1008 the speed of the pump based at least in part on controlling voltage supplied to the pump after the start-up period. The start-up period can be greater than about 5 seconds and less than about 300 seconds. In some implementations, thecontroller1000 receives1002 the signal from the encoder at a first rate during the start-up period and receives1002 the signal from the encoder at a second rate after the start-up period (e.g., the first rate is greater than the second rate).
• Theliquid applicator module1400 includes a supply volume S which is a compartment withinliquid volume600. However, in some implementations, supply volume S is a separate volume carried by thechassis100. Supply volume S defines anexit aperture604 in fluid communication with afluid conduit606. During use,fluid conduit606 delivers a supply of cleaning liquid to a pump assembly240 (e.g., a peristaltic pump assembly). Pressure created bypump assembly240 forces liquid totroughs202a,band through therespective injection orifices210a,btoward the surface. In some embodiments,pump assembly240 includes separate pumps to force liquid torespective troughs202a, b.
• Theliquid applicator module1400 applies cleaning liquid to the surface at a volumetric rate ranging from about 0.1 mL per square foot to about 6.0 mL per square foot (e.g., about 3 mL per square foot). However, depending upon the application, theliquid applicator module1400 can apply any desired volume of cleaning liquid onto the surface. For example, theliquid applicator module1400 can adjust the relative volumetric fraction of cleaning liquid dispensed throughtrough202aandtrough202b(e.g., by adjusting the pressure drop along the respective paths between thepump assembly240 and theorifices210a,bof therespective troughs202aand202b). Additionally or alternatively, theliquid applicator module1400 can be used to apply other liquids onto the surface such as water, disinfectant, chemical coatings, and the like.
• Theliquid applicator module1400 can be a closed system (e.g., whenpump240 is a peristaltic pump) such that theliquid applicator module1400 can be used to deliver a wide variety of cleaning solutions, without damaging other components (e.g., seals) of therobot10. For example, as described below, a potting material can be disposed between theliquid applicator module1400 and electrical components carried by the robot to isolate theliquid applicator module1400 from fluid communication with the electrical components.
• A user can fill the supply container S with a measured volume of clean water and a corresponding measured volume of a cleaning agent. The water and cleaning agent can be poured into the supply volume S throughfill port602 accessible throughfill door304 inbumper300. Thefill port602 can include a funnel to allow for easier pouring of the cleaning liquid into the supply volume S. In some implementations, a filter is disposed betweenfill port602 and the supply volume S to inhibit foreign material from entering the supply volume S and potentially damaging theliquid applicator module1400. The supply volume S has a liquid volume capacity of about 500 mL to about 2000 mL.
• FIG. 22 depicts thePCB cover103, which seals the PCB in a hermetically sealed enclosed volume (which is later filled with a potting compound via the shownvalve157, as disclosed herein) and a support for abypass channel155 formed from a T-shapedchannel155ain thePCB cover103 wall and a T-shapedcover assembly155bwhich hermetically seals thechannel155aand provides 3-5 (preferably 5)nozzles155cto dispense liquid therefrom. The seal is ideally air-tight, but may be hermetic or hydraulically sealed.
• As shown inFIG. 23, the T-shapedcover assembly155bis optionally formed separately from thePCB cover103, and is then welded (e.g., shear welded using conventional plastics forming process) to the channel in the PCB cover. The T-shape of thechannel155, divides to cover the cleaning width of the robot and/or rows ofbristles205, and connects both T-arms of thebypass channel155 to thepump240 system. Thenozzles155cand fluid pressure of thepump240 system are arranged to eject fluid (either spraying and/or dripping, depending on factors such as back pressure, viscosity, nozzle diameter, process variation), but in any event dispensing sufficient fluid to fall into or through theorifices210binrear trough202b. Thenozzles155ccan be arranged to face theorifices210bin thetrough202b(to spray, drip, or flow onto the floor surface) and/or face walls of thetrough202b(so as to distribute fluid toorifices210bthat are not facing anozzle155c).
• FIG. 24 shows a bottom view of thePCB cover103 assembled to therobot10, before the T-shapedchannel cover assembly155bis in place. In this view, portions of the robot remain unassembled (e.g., the bumper, wheel drives, peristaltic pump tube, andfront trough202a.
• The leadingtrough202a, as shown inFIGS. 3 and 25, is formed as a substantially actuate (following the bumper profile, therefore flattened if the bumper is also flattened to provide a flat resting surface for the robot10) hermetically sealed trough which directs (again, spraying or dripping depending on various factors) fluid substantially rearwards, ideally spraying onto the wettingassembly204 formed in part by the immediately following row of bristles205 (the leading row of bristles205) so that the row ofbristles205 wicks the sprayed water and evenly dispenses it to the floor. As shown inFIG. 25, each dispensingorifice210ais formed as an arched orifice210a-1 in a channel portion202a-1 of thetrough202amatched to an arched plug210a-2 in a cover portion202a-2 of the trough202s. In this manner, the orifices (nozzles)210acan be formed by welding a channel to a cover. It is sufficient for operation if either spraying or dripping directly onto thebristles205 or floor occurs. The T-shapedbypass channel155 is arranged at abypass end155dto mate to a corresponding receptacle202a-3 in theleading trough202atogether forming a sealed connection controlled to distribute fluid in differing proportions as disclosed herein. The leadingtrough202ais assembled after the T-shapedchannel155 is formed in thePCB cover103 so as to close and mate the receptacle202a-3 to thebypass orifice end155d—these are welded to form a hermetic/hydraulic seal (alternatively, solvent bonded).
• While the T-shapedbypass channel155 has been described as directing a fraction of the total amount of cleaning liquid rear of thesqueegee208, other implementations are possible. For example, in some implementations, thesqueegee208 can be lifted (e.g., through an actuator) from the cleaning surface such that liquid dispensed through theforward trough202aremains distributed on the cleaning surface. Additionally or alternatively, the T-shapedbypass channel155 can allow water to be dispensed forward and rear of thesqueegee208 such that, when all of the clean water is dispensed from therobot10 to the cleaning surface, therobot10 only picks up water.
• In one implementation, a lesser proportion of cleaning liquid is dispensed rear of thesqueegee208. For example, about 50 to about 90 percent of the cleaning liquid is dispensed forward of thesqueegee208 and about 50 to about 10 percent of the cleaning liquid is dispensed rear of thesqueegee208. Therobot10 can clean with a random component such that the robot partially cleans with the fore wetting even if therobot10 never returns to the same spot on the cleaning surface, but will have the significant benefit of the rear wetting if it does return to the same spot. Additionally or alternatively, dispensing a lesser proportion of cleaning fluid rear of thesqueegee208 can be desirable if there is a reason to avoid leaving fluid on the floor (e.g., cultural preference, hardwood floors, etc). In still another example, arobot10 with a navigation approach and a single-pass requirement would also benefit from more wetting in front of thesqueegee208, along with a slow speed.
• In another implementation, a lesser proportion of cleaning liquid is dispensed forward of thesqueegee208. For example, about 0 to about 40 percent of the cleaning liquid is dispensed forward of thesqueegee208 and about 100 to about 60 percent of the cleaning liquid is dispensed rear of thesqueegee208. Such a distribution of cleaning liquid rear of thesqueegee208 can be coupled with a navigation component mandating two passes such that the robot is highly likely (e.g., greater than about 75 percent likely) to return to each spot twice (once for dispensing the cleaning liquid and once for picking up the cleaning liquid).
• In yet another implementation, the relative proportions of cleaning liquid dispensed forward of thesqueegee208 and rear of thesqueegee208 can be adjusted (e.g., manually or through an actuator) to match the requirements of a particular application. For example, the robot in a single pass approach can be wetter in front and the robot in a double pass mode can be wetter in the rear.
• Referring to FIGS.2 and10A-E, the wettingelement204 can slidably contact the surface such that the movement of therobot10 across the surface causes the wettingassembly204 to spread the cleaning liquid across the surface. At least some ofrows205 are arranged substantially parallel totrough202aand extend past each end of thetrough202ato allow, for example, for suitable smearing near the edges of thetrough202a. Ends215,216 ofrows205 extend substantially in front ofrespective wheels504,505, and the bristles disposed along the ends215,216 are disposed at an angle. By smearing cleaning liquid directly in front ofwheels504,505,rows205 can improve the traction between thewheels504,505 and the surface.
• At least some of therows205 of bristles can have a substantially arcuate shape that extends substantially parallel to the forward perimeter of therobot10. As the substantially arcuate rows make slidable contact with the floor during operation of therobot10, the substantially arcuate shape can facilitate movement of therobot10 across the surface. For example, as compared to a substantially straight row of bristles, the substantially arcuate shape of the forwardmost ofrows205 can gradually engage a grout line (e.g., of a tiled floor) such therobot10 can adjust to the force required to traverse the grout line.
• While the wettingelement204 has been described asrows205,206, and207 of bristles, other implementations are possible. For example, the wettingelement204 can include one or more compliant blades extending in a direction substantially parallel to the cleaning surface. The compliant blade can be in contact with the cleaning surface to smear the cleaning liquid on the surface as the robot moves in the forward direction.
• Referring toFIG. 10B, in some implementations,rows205,206, and207 are disposed on thebaseplate200. Therows205,206, and207 include a plurality ofbristle clusters222 extending from thebaseplate200 toward the cleaning surface. The bristleclusters222 are spaced (e.g., substantially evenly spaced) along eachrow205,206, and207.Bristle clusters222 can each include a plurality of soft compliant bristles. In some implementations, a first end of each bristle is secured in a holder such as a crimped metal channel, or other suitable holding element. In certain implementations, bristleclusters222 are individual plugs press fit into thebaseplate200. A second end of each bristle is free to bend as each bristle makes contact with the cleaning surface. Additionally or alternatively, bristleclusters222 are plugs (e.g., about 1 mm in diameter) with respective ends of each bristlecluster222 disposed toward the cleaning surface and a middle portion of each bristlecluster222 glued and/or stapled to thebaseplate200. These multiple points of contact between the bristles of each bristlecluster222 and the surface can allow therobot10 to traverse smoothly over perturbations in the surface (e.g., grout lines).
• The length and diameter of the bristles ofbristle clusters222, as well as a nominal interference dimension that the smearing bristles make with respect to the cleaning surface can be varied to adjust bristle stiffness and to thereby affect the smearing action and drag. In certain implementations, thebristle clusters222 includes nylon bristles with an average bristle diameter in the range of about 0.05-0.2 mm (0.002-0.008 inches) and an average coefficient of friction on a wet cleaning surface of about 0.1 to about 0.3 (e.g., about 0.2).
• Therows205 and206 of bristles have an angle of incidence of about 90 degrees with the cleaning surface as the robot moves in the forward direction. At least some of therows205 have about zero interference with the cleaning surface and atleast row206 has an interference with the cleaning surface. For example,rows205 closest to the forward portion of thechassis100 can have about zero interference with the cleaning surface while row206 (e.g., the row closest to the squeegee208) has an interference with the cleaning surface. This combination balances the scrubbing action of therows205 and206 with mobility of the robot10 (e.g., reducing drag and/or reducing the likelihood that the robot will attempt to climb an obstacle that it cannot surmount).
• In some implementations, the bristles ofrows205 having about zero interference with the cleaning surface are longer than the bristles ofrow206 having an interference with the cleaning surface. For example,rows205 can be disposed along a recessedportion221 of thebaseplate200 whilerow206 can be disposed along anunrecessed portion223 of thebaseplate200. In this configuration,205 can have a longer effective beam length thanrow206.
• Thebaseplate200 of the robot can be supported about 4 mm above the cleaning surface as therobot10 moves across the cleaning surface in the forward direction. The bristles of therow207 rear of thesqueegee208 have an average length of about 5 mm to about 6 mm (e.g., about 5.4 mm). The bristles ofrow207 also have an angle of incidence of about 45 degrees with the cleaning surface as the robot moves in the forward direction. This angled orientation of the bristles ofrow207 can allow the bristles to act as a spring to assist therobot10 in climbing obstacles. For example, as the bristles ofrow207 move over an obstacle, each bristle has a tendency to return to the angle of about 45 degrees relative to the surface. The tendency to return to this position results in each bristle exerting a force on the obstacle. Additionally or alternatively, the 45 degree orientation of the bristles ofrow207 can facilitate smearing of the cleaning liquid on the surface.
• While wettingassembly204 has been described as havingrows205,206, and207 of bristles, other implementations are additionally or alternatively possible. For example, the wettingassembly204 can include a woven or nonwoven material, e.g., a scrubbing pad or sheet material configured to contact the surface.
• Cleaning liquid can be introduced to therows205,row206, androw207 in any of various different ways. For example, cleaning liquid can be injected or dripped on the surface immediately forward of the scrubbing brush. Additionally or alternatively, cleaning liquid can be introduced through bristleclusters222 such that thebristle clusters222 substantially wick the cleaning liquid toward the surface. Additionally or alternatively, thebaseplate200 can carry other elements configured to spread the cleaning liquid on the surface. For example, thebaseplate200 can carry a sponge or a rolling member in contact with the surface.
• In some implementations, thebaseplate200 carries one or more active scrubbing elements that are movable with respect to the cleaning surface and with respect to the robot chassis. Movement of the active scrubbing elements can increase the work done between the scrubbing element and the cleaning surface. Each active scrubbing element can be driven for movement with respect to thechassis100 by a drive module, also attached to thechassis100. Active scrubbing element can also include a scrubbing pad or sheet material held in contact with the cleaning surface, or a compliant solid element such a sponge or other compliant porous solid foam element held in contact with the surface and vibrated by a vibrated backing element. Additionally or alternatively, active scrubbing elements can include a plurality of scrubbing bristles, and/or any movably supported conventional scrubbing brush, sponge, or scrubbing pad used for scrubbing. In certain implementations, an ultrasound emitter is used to generate scrubbing action. The relative motion between active scrubbing elements and the chassis can include linear and/or rotary motion and the active scrubbing elements can be configured to be replaceable or cleanable by a user.
• Referring toFIG. 11, in some implementations,surface agitation assembly604 includes a rotatable brush assembly disposed across the cleaning width, rearward of injection orifices210, for actively scrubbing the surface after the cleaning fluid has been applied thereon. Thesurface agitation assembly604 includes a cylindricalbristle holder element618 defining alongitudinal axis629. Thebristle holder element618supports scrubbing bristles616 extending radially outward therefrom. Thesurface agitation assembly604 can be supported onchassis100 for rotation about a rotation axis that extends substantially parallel with the cleaning width. The scrubbing bristles616 are long enough to interfere with the cleaning surface during rotation such that the scrubbing bristles616 are bent by the contact with the cleaning surface. Additional bristles can be introduced into receivingholes620. The spacing between adjacent bristle clusters (e.g., bristleclusters622,624) can be reduced to increase scrubbing intensity.
• Scrubbing bristles616 can be installed in the brush assembly in groups or clumps with each clump including a plurality of bristles held by a single attaching device or holder. Clump locations can be disposed along a longitudinal length of thebristle holder element618 in one ormore patterns626,628. The one ormore patterns626,628 place at least one bristle clump in contact with cleaning surface across the cleaning width during each revolution of therotatable brush element604. The rotation of thebrush element604 is clockwise as viewed from the right side such that relative motion between the scrubbing bristles616 and the cleaning surface tends to move loose contaminants and waste liquid toward the rearward direction. Additionally or alternatively, the friction force generated by clockwise rotation of thebrush element604 can drive the robot in the forward direction thereby adding to the forward driving force of the robot transport drive system. The nominal dimension of each scrubbing bristles616 extended from thecylindrical holder618 can cause the bristle to interfere with the cleaning surface and there for bend as it makes contact with the surface. The interference dimension is the length of bristle that is in excess of the length required to make contact with the cleaning surface. Each of these dimensions along with the nominal diameter of the scrubbing bristles616 may be varied to affect bristle stiffness and therefore the resulting scrubbing action. For example, scrubbingbrush element604 can include nylon bristles having a bend dimension of approximately 16-40 mm (0.62-1.6 inches), a bristle diameter of approximately 0.15 mm (0.006 inches), and an interference dimension of approximately 0.75 mm (0.03 inches) to provide scrubbing performance suitable for many household scrubbing applications.
• While thesurface agitation assembly604 has been described as including a rotating brush, other implementations are possible. For example, thesurface agitation assembly604 can be one or more of the following: a stationary brush, a woven cloth, a nonwoven cloth, a sponge, and a compliant blade. Additionally or alternatively, thesensor module1100 can include a humidity sensor and theagitation assembly604 can act on the cleaning surface based at least in part on detection of humidity on the cleaning surface. Details of such a humidity sensor are disclosed in U.S. patent application Ser. No. 11/688,225, entitled “Lawn Care Robot,” the entire contents of which are incorporated herein by reference.
• In some implementations, an autonomous cleaning robot includes an extension element230 carried by the robot along a substantially forward portion of the robot such that the extension element extends beyond the perimeter of the robot. Details of such an extension element are disclosed in U.S. patent application Ser. No. 12/118,250, entitled “Autonomous Coverage Robot Sensing,” the entire contents of which are incorporated herein by reference.
• Air Moving
• Referring toFIG. 12, acollection module1300 is a vacuum assembly including afan112 in fluid communication with the waste collection volume W and thesqueegee208 in contact with the surface. In use, thefan112 creates a low pressure region along the fluid communication path including the waste collection volume W and thesqueegee208. As described in further detail below, thefan112 creates a pressure differential across thesqueegee208, resulting in suction of waste from the surface and through thesqueegee208. The suction force created by thefan112 can further suction the waste through one or more waste intake conduits232 (e.g., conduits disposed on either end of the squeegee208) toward a top portion of the waste collection volume W.
• The top portion of the waste collection volume W defines aplenum608 betweenexit apertures234 ofwaste inlet conduits232 andinlet aperture115 offan intake conduit114. While thefan112 is in operation, the flow of air and waste throughplenum608 generally moves fromexit apertures234 toward theinlet aperture115. In some implementations,plenum608 has a flow area greater than the combined flow area of the one or morewaste intake conduits232 such that, upon expanding in the top portion of the waste collection volume W, the velocity of the moving waste decreases. At this lower velocity, heavier portions of the moving waste (e.g. water and debris) will tend to fall into the waste collection volume W under the force of gravity while lighter portions (e.g., air) of the moving waste will continue to move toward one or morefan inlet conduits114. The flow of air continues through thefan inlet conduit114, through thefan112, and exits therobot10 through afan exit aperture116.
• In some implementations, at least a portion of thefan112 is disposed in thefan inlet conduit114 such that air drawn through the fan inlet conduit can cool the fan. For example, the portion of the fan disposed in thefan inlet conduit114 can be a heat sink (e.g., a finned heat sink). In some implementations, a portion of thefan112 that is not disposed in the fan inlet conduit is disposed in a potting material (e.g., potting material105). The thermal conductivity of the potting material can be greater than the thermal conductivity of air and the potting material can isolate thefan112 and thefan inlet conduit114 from fluid communication with at least a portion of the chassis100 (shown inFIG. 7). Additionally or alternatively, the potting material can substantially isolate thefan112 from fluid communication with theliquid applicator1400. Thecollection module1300 can include an anti-spill system601 (e.g., a passive anti-spill system and/or an active anti-spill system) that substantially prevents waste from exiting waste collection volume W when therobot10 is not in use (e.g., when a user lifts therobot10 from the surface). By reducing the likelihood that waste will spill from the robot, such anti-spill systems can protect the user from coming into contact with the waste during handling. Additionally or alternatively, such anti-spill systems can reduce the likelihood that waste will contact the fan and potentially diminish the performance of the fan over time. Details of theanti-spill system601 are disclosed in U.S. patent application Ser. No. 12/118,250, entitled “Autonomous Coverage Robot Sensing,” the entire contents of which are incorporated herein by reference.
• Details of thefan112 are disclosed in U.S. patent application Ser. No. 12/118,250, entitled “Autonomous Coverage Robot Sensing,” the entire contents of which are incorporate herein by reference.
• The air flow rate of thefan112 may range from about 60-100 CFM in free air and about 60 CFM in the robot. In some implementations, thecollection module1300 includes both a wet vacuum subsystem and a dry vacuum subsystem and the air flow rate of the fan can split (e.g., manually adjusted) between the wet and dry vacuum subsystems. Additionally or alternatively, a multi-stage fan design can produce a similar air flow rate, but higher static pressure and velocity, which can help to maintain flow. Higher velocity also enables the device to entrain dry particles and lift and pull fluids (e.g., debris mixed with cleaning liquid).
• Referring again toFIGS. 3 and 7, thesqueegee208 is configured in slidable contact with the surface while therobot10 is in motion. The positioning of thesqueegee208 androw207 substantially rearward of thewheels504,505 can stabilize the motion of therobot10. For example, during sudden acceleration of therobot10, thesqueegee208 androw207 can prevent the robot from substantially rotating about thetransverse axis24. By providing such stabilization, thesqueegee208 and/orrow207 can prevent therows205 carried on a forward portion of therobot10 from substantially lifting from the surface. When the overall weight of therobot10 is less than 3.6 kg, for example, such positioning of thesqueegee208 and/orrow207 can be particularly useful for providing stabilization. For such lightweight robots, the center of gravity of therobot10 can be positioned substantially over thetransverse axis24 of the robot such that substantial weight is placed over thewheels504,505 for traction while thesqueegee208 and/orrow207 provide stabilization for the forward direction of travel and therows205 and/orrow206 provide stabilization for the reverse direction of travel. For example, the center of gravity of therobot10 can be positioned substantially at the center of the robot as viewed from the above the robot as the robot moves across the cleaning surface and the robot is full of cleaning liquid.
• Referring to FIGS.3 and13-15, thesqueegee208 includes a base250 extending substantially the entire width of thebaseplate200. A substantially horizontallower section252 extends downwardly from the base250 toward the surface. Edge guides253,254 are disposed near each transverse end of thebase250 and extend downwardly from thebase250. A plurality offastener elements256 extend upwardly from thebase250 and are configured to fit (e.g., interference fit) within corresponding apertures defined bybaseplate200 to hold aforward edge portion257 of thesqueegee208 securely in place as therobot10 moves in the forward direction about the surface. Arear edge portion259 of thesqueegee208 is unattached to thebaseplate200 such that a user can move therear edge portion259 of the squeegee away from thebaseplate200 to clean thesqueegee208 and/or thebaseplate200. During use, therear edge portion259 of the vacuum created by thefan112 holds therear edge259 of thesqueegee208 in place relative to thebase plate200.
• The horizontallower section252 includes ascraper section258 extending substantially downwardly from anintake section260. Thescraper section258 defines a substantially rearward edge of the horizontallower section252. During use, thescraper section258 forms a slidable contact edge between thesqueegee208 and the surface. Thescraper section258 is a substantially longitudinal ridge disposed between theforward edge portion257 and therear edge portion259. Thescraper section258 is substantially thin and formed of a substantially compliant material to allow thescraper section258 to flex during slidable contact with the surface. In some implementations, thescraper section258 is angled slightly forward to improve collection of waste from the surface. In certain implementations, thescraper section258 is angled slightly rearward to reduce the frictional force required to propel therobot10 in the forward direction.
• Theintake section260 defines a plurality ofsuction ports262 substantially evenly spaced in the direction of thetransverse axis24 to allow, for example, substantially uniform suction in the direction of thetransverse axis24 as therobot10 moves in the forward direction to perform cleaning operations. Thesuction ports262 each extend through the squeegee208 (e.g., from a lower portion of the horizontallower section252 to a top portion of the base250). Thesuction ports262 extend through the base such that a lower portion of eachsuction port262 is substantially near the forward edge of thescraper section258. When negative air pressure (e.g., a vacuum) is generated by thefan112, waste is suctioned from the forward edge of thescraper section258, through thesuction ports262, and toward the waste collection volume W (e.g., as described above).
• Edge guides253,254 are arranged on respective ends ofsqueegee208 and extend downwardly from the base250 to contact the surface during a cleaning operation. The edge guides253,254 can be configured to push waste toward the fore-aftaxis22 of therobot10. By guiding waste toward a center portion of thesqueegee208, the edge guides253,254 can improve the efficiency of waste collection at the transverse edges of therobot10. For example, as compared to robots without edge guides253,254, the edge guides253,254 can reduce streaks left behind by therobot10.
• Edge guides253,254 includerespective fasteners263,264 extending upward from the edge guides253,254 and through thebase250. Theedge guide fasteners263,264 extend further from the base250 thanfastener elements256 and, in some implementations, fasten into thebaseplate200 to reduce the likelihood that thesqueegee250 will become detached from therobot10 during a cleaning operation. In some implementations,fasteners263,264 are pressed into thebaseplate200 and held in place through an interference fit. Incertain implementations fasteners263,264 are screwed into thechassis100. Additionally or alternatively, theedge guide fasteners263 can be fastened to thechassis100.
• Fastener elements256 extend upwardly from thebase250, along theforward edge portion257 of thebase250. Eachfastener element256 is substantially elongate along thetransverse axis24 and includes astem portion265 and ahead portion266. Thesqueegee208 is secured to thebaseplate200 by pushingfastener elements256 into corresponding apertures on thebaseplate200. As thefastener elements256 are pushed into apertures on thebaseplate200, thehead portions266 deform to pass through the apertures. Upon passing through the apertures, eachhead portion266 expands to its substantially original shape and thehead portion266 substantially resists passing through the aperture in the opposite direction. Accordingly,fastener elements256 substantially secure theforward edge portion257 of thesqueegee208 to thebaseplate200. As described above, therear edge portion259 of thesqueegee208 can be unattached to thebaseplate200 such that a user can move therear edge portion259 away from the baseplate200 (e.g., pivoting away from thebaseplate200 about the forward edge portion257) to access the portion of thesqueegee208 in contact with thebaseplate200 and, during use, suction created by the fan112 (seeFIG. 12) can hold therear edge portion259 of thesqueegee208 in place.
• While thesqueegee208 has been described as being fixed relative to thebaseplate200, other implementations are possible. In some implementations, the squeegee can pivot relative to thebaseplate200. For example, the squeegee can pivot about the central vertical axis20 (FIG. 7) when a lower edge of the squeegee encounters a bump or discontinuity in the cleaning surface. When the lower edge of the squeegee is free of the bump or discontinuity, the squeegee can return to its normal operating position.
• As shown inFIG. 14, thesqueegee208 is a split squeegee such that thescraper section258 and theintake section260 define achannel261 extending across the width of thesqueegee208. In some implementations, the squeegee can include a forward portion and a rearward portion as two separate pieces that can be separately removed from the baseplate for repair and replacement.
• In certain implementations, the squeegee is split into a left portion and a right portion. As the robot spins in place or turns, the squeegee can assume a configuration in which one side is bent backward and one side is bent forward. For non-split squeegees, the point at which the bend switches from backward to forward can act as a more or less solid column under the robot, tending to high center it and interfere with mobility. By providing a split in the center of the squeegee, this tendency can be mitigated or eliminated, increasing mobility.
• Transport Drive System
• Referring again toFIGS. 1-7, therobot10 is supported for transport over the surface by atransport system1600. Thetransport system1600 includes a pair ofindependent wheel modules500,501 respectively arranged on the right side and the left side of the chassis. The wettingassembly204 and thesqueegee208 are in slidable contact with the surface and form part of thetransport system1600. In some implementations, thetransport system1600 can include a caster positioned substantially forward and/or substantially rearward of thewheel modules500,501. Thewheel modules500,501 are rotatable about and aligned along thetransverse axis24 of therobot10. Thewheel modules500,501 are independently driven and controlled by thecontroller1000 to advance therobot10 in any direction along the surface. Thewheel modules500,501 each include arespective motor502,503 and each is coupled to a gear assembly. Outputs of the respective gear assemblies drive therespective wheel504,505.
• Thecontroller1000 measures the voltage and current to each motor and calculates the derivative of the measured current to each motor. Thecontroller1000 uses the measured voltage, measured current, and the calculated derivative of the measured current to determine the speed of the motor. For example, thecontroller1000 can use a mathematical model (e.g., a DC motor equation) to determine motor speed from the measured voltage, measured current, and the calculated derivative. In certain implementations, the same mathematical model can be used for each drive motor. The mathematical model can include one or more constants (e.g., mechanical constants) are calibrated for a given motor. The one or more constants can be calibrated using any of various different methods. For example,motors502,503 can be matched at the factory to have the same constant. As another example, the constants can be calibrated at the factory and stored onboard the robot10 (e.g. on the controller1000). As another example, thecontroller1000 can include code that learns (e.g., using a neural network) the motor constants over time.
• As yet another example, referring toFIGS. 1,7, and16, binning800 includestesting802 performance of a plurality of motors on an encoder station (e.g., at a factory), classifying804 each motor based at least in part on the performance test results, selecting806 a first and a second motor (e.g.,motors502,503) from the same class, and mounting808 the first and second motors on a robot body (e.g., chassis100) of an autonomous coverage robot (e.g., robot10) such that the first motor drives a right wheel of the robot and the second motor drives a left wheel of the robot. Testing802 performance of the plurality of motors on the encoder station includes providing power to each motor and determining the speed of the output shaft of each respective motor. In some implementations, based on thistesting802, a relationship between motor voltage and speed can be determined. Classifying804 each motor can include identifying motors with output speed varying by less than about ten percent from one another as a function of power to each motor. By selecting motors from the same class, the robot can be driven in a substantially straight line by providing substantially the same amount of power to the first and second drive motors disposed on respective sides of the robot. Selection of motors based on binning800 can allow the robot to be driven in a substantially straight line without the use of an encoder.
• Thewheel modules500,501 are releasably attached to thechassis100 and forced into engagement with the surface by respective springs. Thewheel modules500,501 are substantially sealed from contact with water using one or more the following: epoxy, ultrasonic welding, potting welds, welded interfaces, plugs, and membranes.
• The springs are calibrated to apply substantially uniform force to the wheels along the entire distance of travel of the suspension. Thewheel modules500,501 can each move independently in a vertical direction to act as a suspension system. For example, thewheel modules500,501 can allow about 4 mm of suspension travel to about 8 mm of suspension travel (e.g., about 5 mm of suspension travel) to allow therobot10 to navigate over obstacles on the surface, but to prevent therobot10 from crossing larger thresholds that mark the separation of cleaning areas (e.g., marking the separation between a kitchen floor and a living room floor). When therobot10 is lifted from the surface, the respective suspension systems ofwheel modules500,501 drop thewheel modules500,501 to the lowest point of travel of the respective suspension system. This configuration is sometimes referred to as a biased-to-drop suspension system. In some implementations, thewheel modules500,501 can include a wheel drop sensor that senses when awheel504,505 ofwheel modules500,501 moves down and sends a signal to thecontroller1000. Additionally or alternatively, thecontroller1000 can initiate behaviors that can allow therobot10 to navigate toward a more stable position on the surface.
• The biased-to-drop suspension system of therobot10 includes a pivoted wheel assembly including resilience and/or damping, having a ride height designed considering up and down force. In some implementations, the suspension system delivers within 1-5% (e.g., about 2%) of the minimum downward force of the robot10 (i.e., robot mass or weight minus upward forces from the resilient or compliant contacting members such as brushes/squeegees, etc). That is, the suspension is resting against “hard stops” with only 2% of the available downward force applied (spring stops having the other 98%, optionally 99%-95%), such that almost any obstacle or perturbation capable of generating an upward force will result in the suspension lifting or floating the robot over the obstacle while maintaining maximum available force on the tire contact patch. This spring force (and in corollary, robot traction) can be maximized by having an active system that varies its force relative to the changing robot payload (relative clean and dirty tank level). In some implementations, actuation for an active suspension is provided by electrical actuators or solenoids, fluid power, or the like, with appropriate damping and spring resistance. While a pivoted wheel assembly has been described, other implementations are possible. For example, the biased-to-drop suspension system can include a vertically traveling wheel module including conical springs to produce a biased-to-drop suspension system.
• Wheels504,505 are configured to propel therobot10 across a wet soapy surface. Referring to FIGS.17 and18A-B,wheel504 includes arim512,snaps513 slidable into a recesses defined by therim512 to couple to therim512 to thewheel module500, and anannular tire516. For the sake of clarity of explanation,wheel504 is explained. However, it should be appreciated thatwheel505 is analogous towheel504. The drive wheel module includes a drive motor and a drive train transmission for driving the wheel for transport. The drive wheel module can also include a sensor for detecting wheel slip with respect to the surface.
• Therim512 is formed from a stiff material such as a hard molded plastic to maintain the wheel shape and to provide stiffness. Therim512 provides an outer diameter sized to receive anannular tire516 thereon. Theannular tire516 is configured to provide a non-slip, high friction drive surface for contacting the surface and for maintaining traction on the soapy surface.
• In one implementation, theannular tire516 has an internal diameter of approximately 37 mm and is sized to fit appropriately over theouter diameter514 ofrim512. Therim516 includes aridge517 extending radially outward from theouter diameter514 of the rim and extending around the circumference of the rim. Theannular tire516 defines acircumferential channel518 that is engageable with theridge517 such that theridge517 can serve as an alignment feature for mounting theannular tire516 and can hold theannular tire516 in place. In certain implementations, theannular tire516 can be removed from therim512, and theannular tire516 can be reversed such that the inner diameter of theannular tire516 becomes the outer diameter of theannular tire516. For example, as discussed below, theannular tire516 can have a tread pattern on the outer diameter and a treat pattern on the inner diameter. As the tread pattern on the outer diameter of theannular tire516 wears down over time, theannular tire516 can be reversed such that the tread pattern on the inner diameter becomes exposed toward the cleaning surface. In some implementations, theannular tire516 can be additionally or alternatively bonded, taped or otherwise interference fit to theouter diameter514 to prevent slipping between an inside diameter of theannular tire516 and theouter diameter514 of therim512.
• Theannular tire516 includes a base520 having afirst side522 and asecond side524 substantially opposite the first side. The base520 can have a radial thickness sufficient to allow theannular tire516 to be easily reversed by the user while resisting tearing. For example, the base520 can have a radial thickness of about 3 mm.
• Theannular tire516 also includes a first set oftreads526 and a second set oftreads528. Eachtread530 of the first and second set oftreads526,528 extends radially from thefirst side522 of the base520 toward the cleaning surface and is an elongate rib extending in a direction substantially parallel to the transverse axis. In this transverse orientation, eachtread530 can grip an obstacle (e.g., a tile edge and/or a discontinuity in the cleaning surface) to move a wet cleaning robot under about 3 kg over the obstacle, which may be wet.
• Eachtread530 of the first set oftreads526 is circumferentially offset from each of the treads of the second set oftreads528 such that, as viewed along the transverse axis, treads530 of the first set oftreads526 are not aligned with thetreads530 of the second set oftreads530. This offset configuration of the treads can facilitate movement of therobot10 over an uneven surface. Eachtread530 can have at least one substantially square edge disposed toward the cleaning surface. Such a substantially square edge can reduce the likelihood that thetread530 will become disengaged from an obstacle once the tread engages the obstacle.
• Eachtread530 of each of the first and second set oftreads526,528 can be substantially identical to facilitate smooth movement of therobot10 over the surface. For example, eachtread530 can have substantially the same width in the circumferential direction. Additionally or alternatively, eachtread530 of a given set oftreads526,528 can be circumferentially spaced from a preceding tread of the respective set oftreads526,528 by a distance about three times the circumferential width of the tread. This circumferential spacing of thetreads530 can provide spacing that allows theannular tire516 to engage an obstacle between thetreads530 such that eachtread530 can come into contact with the obstacle and act as a lever to move therobot10 over the obstacle. To achieve sufficient leverage while maintaining a smooth ride for efficient cleaning, eachtread530 can extend radially from the base520 by a distance between about ⅕ to about ½ the radial thickness of the base.
• Theannular tire516 also includes a third set oftreads532 and a fourth set oftreads534. The third set oftreads532 extends radially inward from thesecond side524 of thebase520, substantially opposite the first set oftreads526. Similarly, the fourth set oftreads534 extends radially inward from thesecond side524 of thebase520, substantially opposite the second set oftreads528. Eachtread530 of the third set oftreads532 is circumferentially offset from each tread of the first set oftreads526, and eachtread530 of the fourth set oftreads534 is circumferentially offset from each tread of the second set oftreads528. In some implementations, this offset allows the base to move toward the wheel when atread530 of the first or second set oftreads526,528 contacts the cleaning surface. Such movement of the base can provide some cushioning to the ride of therobot10 to reduce the likelihood that cleaning functions of therobot10 will be adversely impacted as the robot moves over a rough surface.
• The relative orientation of the third set oftreads532 relative to the fourth set oftreads534 is analogous to the relative orientation of the first set oftreads526 relative to the second set oftreads528. For example, each tread of the third set oftreads532 is circumferentially offset from each tread of the fourth set oftreads534.
• The third set oftreads532 is spaced from the fourth set oftreads534 in the transverse direction to define at least a portion of thecircumferential channel518. As indicated above, thecircumferential channel518 can be disengaged from theridge517 and theannular tire516 can be reversed. For example, the annular tire can be reversed such that the third and fourth sets oftreads532,534 extend radially outward and toward the cleaning surface while the first and second sets oftreads526,528 extend radially inward toward therim512.
• The tire material includes particulate matter suspended in rubber (e.g., natural rubber). At least some of the particulate matter is disposed toward the portion of theannular tire516 in contact with the cleaning surface such that the particulate matter penetrates the surface tension of liquid disposed on the cleaning surface. Thus, as compared to natural rubber without particulate matter, the particulate matter disposed in the natural rubber can improve traction of theannular tire516. In some implementations, the tire material is about 20 percent to about 30 percent particulate matter (e.g., about 25 percent particulate matter). Examples of the particulate matter disposed in the natural rubber can include one or more of the following: kaolin clay and calcium carbonate. These materials improve traction of the annular tire to propel a wet-cleaning robot under about 3 kg across a wet surface without creating a surface roughness that can damage (e.g., scratch) the cleaning surface.
• Other tire materials are contemplated, depending on the particular application. For example, the tire material can include a chloroprene homopolymer stabilized with thiuram disulfide black with a density of 14-16 pounds per cubic foot, or approximately 15 pounds per cubic foot foamed to a cell size of 0.1 mm plus or minus 0.02 mm. The tire has a post-foamed hardness of about 69 to 75Shore 00. The tire material is sold by Monmouth Rubber and Plastics Corporation under the trade name DURAFOAM DK5151HD.
• Still other tire materials are contemplated, depending on the particular application, including, for example, those made of neoprene and chloroprene, and other closed cell rubber sponge materials. Tires made of polyvinyl chloride (PVC) (e.g., injection molded, extruded) and acrylonitrile-butadiene (ABS) (with or without other extractables, hydrocarbons, carbon black, and ash) may also be used. Additionally, tires of shredded foam construction may provide some squeegee-like functionality, as the tires drive over the wet surface being cleaned. Tires made from materials marketed under the trade names RUBATEX R411, R421, R428, R451, and R4261 (manufactured and sold by Rubatex International, LLC); ENSOLITE (manufactured and sold by Armacell LLC); and products manufactured and sold by American Converters/VAS, Inc.; are also functional substitutions for the DURAFOAM DK5151 HD identified above.
• In certain embodiments, the tire material may contain natural rubber(s) and/or synthetic rubber(s), for example, nitrile rubber (acrylonitrile), styrene-butadiene rubber (SBR), ethylene-propylene rubber (EPDM), silicone rubber, fluorocarbon rubber, latex rubber, silicone rubber, butyl rubber, styrene rubber, polybutadiene rubber, hydrogenated nitrile rubber (HNBR), neoprene (polychloroprene), and mixtures thereof.
• In certain embodiments, the tire material may contain one or more elastomers, for example, polyacrylics (i.e. polyacrylonitrile and polymethylmethacrylate (PMMA)), polychlorocarbons (i.e. PVC), polyfluorocarbons (i.e. polytetrafluoromethylene), polyolefins (i.e. polyethylene, polypropylene, and polybutylene), polyesters (i.e. polyetheylene terephthalate and polybutylene terephthalate), polycarbonates, polyamides, polyimides, polysulfones, and mixtures and/or copolymers thereof. The elastomers may include homopolymers, copolymers, polymer blends, interpenetrating networks, chemically modified polymers, grafted polymers, surface-coated polymers, and/or surface-treated polymers.
• In certain embodiments, the tire material may contain one or more fillers, for example, reinforcing agents such as carbon black and silica, non-reinforcing fillers, sulfur, cross linking agents, coupling agents, clays, silicates, calcium carbonate, waxes, oils, antioxidants (i.e. para-phenylene diamine antiozonant (PPDA), octylated diphenylamine, andpolymeric 1,2-dihydro-2,2,4-trimethylquinoline), and other additives.
• In certain embodiments, the tire material may be formulated to have advantageous properties, for example, desired traction, stiffness, modulus, hardness, tensile strength, impact strength, density, tear strength, rupture energy, cracking resistance, resilience, dynamic properties, flex life, abrasion resistance, wear resistance, color retention, and/or chemical resistance (i.e. resistance to substances present in the cleaning solution and the surface being cleaned, for example, dilute acids, dilute alkalis, oils and greases, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, and/or alcohols).
• It is noted that cell size of the closed cell foam tires may impact functionality, in terms of traction, resistance to contaminants, durability, and other factors. Cell sizes ranging from approximately 20 μm to approximately 400 μm may provide acceptable performance, depending on the weight of the robot and the condition of the surface being cleaned. Particular ranges include approximately 20 μm to approximately 120 μm, with a mean cell size of 60 μm, and more particularly approximately 20 μm to approximately 40 μm, for acceptable traction across a variety of surface and contaminant conditions.
• In certain embodiments, the tires are approximately 13 mm wide, although wider tires may provide additional traction. As indicated above, tires may be approximately 3 mm thick, although tires of 4 mm-5 mm in thickness or more may be utilized for increased traction. Thinner tires of approximately 1.5 mm and thicker tires of approximately 4.5 mm may be beneficial, depending on the weight of the robot, operating speed, movement patterns, and surface textures. Thicker tires may be subject to compression set. If the cleaning robot is heavier, larger tires may be desirable nonetheless. Tires with outer rounded or square edges may also be employed.
• To increase traction, the outside diameter of the tire can be siped. Siping generally provides traction by (a) reducing the transport distance for fluid removal from the contact patch by providing a void for the fluid to move into, (b) allowing more of the tire to conform to the floor, thereby increasing tread mobility, and (c) providing a wiping mechanism that aids in fluid removal. In at least one instance, the term “siped” refers to slicing the tire material to provide a pattern of thin grooves1110 in the tire outside diameter. In one embodiment, each groove has a depth of approximately 1.5 mm and a width or approximately 20 to 300 microns. The siping may leave as little as ½ mm or less of tire base, for example, 3.5 mm deep siping on a 4 mm thick tire. The groove pattern can provide grooves that are substantially evenly spaced apart, with approximately 2 to 200 mm spaces between adjacent grooves. “Evenly spaced” may mean, in one instance, spaced apart and with a repeating pattern, not necessarily that every siped cut is the same distance from the next. The groove cut axis makes an angle G with the tire longitudinal axis. The angle G ranges from about 10-50 degrees, in certain embodiments.
• In other embodiments, the siping pattern is a diamond-shaped cross hatch at 3.5 mm intervals, which may be cut at alternating 45 degree angles (.+.−.10 degrees) from the rotational axis. Substantially circumferential siping, siping that forces away liquid via channels, and other siping patterns are also contemplated. Depth and angle of siping may be modified, depending on particular applications. Moreover, while increased depth or width of siping may increase traction, this benefit should be balanced against impacting the structural integrity of the tire foam. In certain embodiments, for example, it has been determined that 3 mm-4 mm thick tires with diamond crossed siping at 7 mm intervals provides good tire traction. Larger tires may accommodate a finer pattern, deeper siping, and/or wider siping. Additionally, particularly wide tires or tires made from certain materials may not require any siping for effective traction. While certain siping patterns may be more useful on wet or dry surfaces, or on different types of surfaces, siping that provides consistent traction across a variety of applications may be the most desirable for a general purpose robot cleaner.
• While the tires have been described as including a siped outside diameter and/or elongate ribs, other implementations are possible. For example, the tires can be Natural Rubber tires with an aggressive diagonal V-rib pattern.
• The various tire materials, sizes, configurations, siping, etc., impact the traction of the robot during use. In certain embodiments, the robot's wheels roll directly through the spray of cleaning solution, which affects the traction, as do the contaminants encountered during cleaning. A loss of fraction of the wheels may cause operating inefficiencies in the form of wheel slippage, which can lead to the robot deviating from its projected path. This deviation can increase cleaning time and reduce battery life. Accordingly, the robot's wheels should be of a configuration that provides good to excellent fraction on all surfaces, with the smallest corresponding motor size.
• Typical contaminants encountered during cleaning include chemicals, either discharged by the robot or otherwise. Whether in a liquid state (e.g., pine oil, hand soap, ammonium chloride, etc.) or a dry state (e.g., laundry powder, talcum powder, etc.), these chemicals may break down the tire material. Additionally, the robot tires may encounter moist or wet food-type contaminants (e.g., soda, milk, honey, mustard, egg, etc.), dry contaminants (e.g., crumbs, rice, flour, sugar, etc.), and oils (e.g., corn oil, butter, mayonnaise, etc.). All of these contaminants may be encountered as residues, pools or slicks, or dried patches. The tire materials described above have proven effective in resisting the material breakdown caused by these various chemicals and oils. Additionally, the cell size and tire siping described has proven beneficial in maintaining traction while encountering both wet and dry contaminants, chemical or otherwise. Dry contaminants at certain concentrations, however, may become lodged within the siping. The chemical cleaner used in the device, described below, also helps emulsify certain of the contaminants, which may reduce the possible damage caused by other chemical contaminants by diluting those chemicals.
• In addition to contaminants that may be encountered during use, the various cleaning accessories (e.g., brushes, squeegees, etc.) of the device affect the traction of the device. The drag created by these devices, the character of contact (i.e., round, sharp, smooth, flexible, rough, etc.) of the devices, as well as the possibility of slippage caused by contaminants, varies depending on the surface being cleaned. Limiting the areas of contact between the robot and the surface being cleaned reduces attendant friction, which improves tracking and motion. One and one-half pounds of drag force versus three to five pounds of thrust has proven effective in robots weighing approximately 5-15 pounds. Depending on the weight of the robot cleaner, these numbers may vary, but it is noted that acceptable performance occurs at less than about 50% drag, and is improved with less than about 30% drag.
• The tire materials (and corresponding cell size, density, hardness, etc.), siping, robot weight, contaminants encountered, degree of robot autonomy, floor material, and so forth, all impact the total traction coefficients of the robot tires. For certain robot cleaners, the coefficient of traction (COT) for the minimum mobility threshold has been established by dividing a 0.9 kg-force drag (as measured during squeegee testing) by 2.7 kg-force of normal force, as applied to the tires. Thus, this minimum mobility threshold is approximately 0.33. A target threshold of 0.50 was determined by measuring the performance of shredded black foam tires. Traction coefficients of many of the materials described above fell within a COT range of 0.25 to 0.47, thus within the acceptable range between the mobility threshold and the target threshold. Additionally, tires that exhibit little variability in traction coefficients between wet and dry surfaces are desirable, given the variety of working conditions to which a cleaning robot is exposed.
• The robot cleaning device may also benefit by utilizing sheaths or booties that at least partially or fully surround the tires. Absorbent materials, such as cotton, linen, paper, silk, porous leather, chamois, etc., may be used in conjunction with the tires to increase traction. Alternatively, these sheaths may replace rubberized wheels entirely, by simply mounting them to the outer diameter of the cup shaped wheel element. Whether used as sheaths for rubber tires or as complete replacements for the rubber tires, the materials may be interchangeable by the user or may be removed and replaced via automation at a base or charging station. Additionally, the robot may be provided to the end user with sets of tires of different material, with instructions to use particular tires on particular floor surfaces.
• The cleaning solution utilized in the robot cleaner should be able to readily emulsify contaminants and debond dried waste from surfaces, without damaging the robot or surface itself. Given the adverse effects described above with regard to robot tires and certain chemicals, the aggressiveness of the cleaning solution should be balanced against the short and long-term negative impacts on the tires and other robot components. In view of these issues, virtually any cleaning material that meets the particular cleaning requirements may be utilized with the cleaning robot. In general, for example, a solution that includes both a surfactant and a chelating agent may be utilized. Additionally, a pH balancing agent such as citric acid may be added. Adding a scent agent, such as eucalyptus, lavender, and/or lime, for example, may improve the marketability of such a cleaner, contributing to the perception on the part of the consumer that the device is cleaning effectively. A blue, green, or other noticeable color may also help distinguish the cleaner for safety or other reasons. The solution may also be diluted and still effectively clean when used in conjunction with the robot cleaner. During operation, there is a high likelihood that the robot cleaner may pass over a particular floor area several times, thus reducing the need to use a full strength cleaner. Also, diluted cleaner reduces the wear issues on the tires and other components, as described above. One such cleaner that has proven effective in cleaning, without causing damage to the robot components, includes alkyl polyglucoside (for example, at 1-3% concentration) and tetrapotassium ethylenediamine-tetraacetate (tetrapotassium EDTA) (for example, at 0.5-1.5% concentration). During use, this cleaning solution is diluted with water to produce a cleaning solution having, for example, approximately 3-6% cleaner and approximately 94-97% water. Accordingly, in this case, the cleaning solution actually applied to the floor may be as little as 0.03% to 0.18% surfactant and 0.01 to 0.1% chelating agent. Of course, other cleaners and concentrations thereof may be used with the disclosed robot cleaner. In certain embodiments, the cleaning solution utilized in the robot cleaner includes (or is) one or more embodiments of the hard surface cleaners described in U.S. Pat. Nos. 5,573,710, 5,814,591, 5,972,876, 6,004,916, 6,200,941, and 6,214,784, and 6,774,098, and U.S. patent application Ser. No. 12/118,250, entitled “Autonomous Coverage Robot Sensing,” all of which are incorporated herein by reference.
• Controller Module
• Referring toFIGS. 1-7,control module1000 is interconnected for two-way communication with each of a plurality of other robot subsystems. The interconnection of the robot subsystems is provided via network of interconnected wires and or conductive elements, e.g. conductive paths formed on an integrated printed circuit board or the like, as is well known. In some implementations, the two-way communication between thecontrol module1000 one or more of the robot subsystems occurs through a wireless communication path. Thecontrol module1000 at least includes a programmable or preprogrammed digital data processor, e.g. a microprocessor, for performing program steps, algorithms and or mathematical and logical operations as may be required. Thecontrol module1000 also includes a digital data memory in communication with the data processor for storing program steps and other digital data therein. Thecontrol module1000 also includes one or more clock elements for generating timing signals as may be required.
• In general, therobot10 is configured to clean uncarpeted indoor hard floor surface, e.g. floors covered with tiles, wood, vinyl, linoleum, smooth stone or concrete and other manufactured floor covering layers that are not overly abrasive and that do not readily absorb liquid. Other implementations, however, can be adapted to clean, process, treat, or otherwise traverse abrasive, liquid-absorbing, and other surfaces. Additionally or alternatively, therobot10 can be configured to autonomously transport over the floors of small enclosed furnished rooms such as are typical of residential homes and smaller commercial establishments. Therobot10 is not required to operate over predefined cleaning paths but may move over substantially all of the cleaning surface area under the control of various transport algorithms designed to operate irrespective of the enclosure shape or obstacle distribution. For example, therobot10 can move over cleaning paths in accordance with preprogrammed procedures implemented in hardware, software, firmware, or combinations thereof to implement a variety of modes, such as three basic operational modes, i.e., movement patterns, that can be categorized as: (1) a “spot-coverage” mode; (2) a “wall/obstacle following” mode; and (3) a “bounce” mode. In addition, therobot10 is preprogrammed to initiate actions based upon signals received from sensors incorporated therein, where such actions include, but are not limited to, implementing one of the movement patterns above, an emergency stop of therobot10, or issuing an audible alert. These operational modes of the robot are specifically described in U.S. Pat. No. 6,809,490, by Jones et al., entitled, Method and System for Multi-Mode Coverage for an Autonomous Robot, the entire disclosure of which is herein incorporated by reference it its entirety. However, the present disclosure also describes alternative operational modes.
• Therobot10 also includes theuser interface400. Theuser interface400 provides one or more user input interfaces that generate an electrical signal in response to a user input and communicate the signal to thecontroller1000. A user can input user commands to initiate actions such as power on/off, start, stop or to change a cleaning mode, set a cleaning duration, program cleaning parameters such as start time and duration, and or many other user initiated commands. While theuser interface400 has been described as a user interface carried on therobot10, other implementations are additionally or alternatively possible. For example, a user interface can include a remote control device (e.g., a hand held device) configured to transmit instructions to therobot10. Additionally or alternatively, a user interface can include a programmable computer or other programmable device configured to transmit instructions to therobot10. In some implementations, the robot can include a voice recognition module and can respond to voice commands provided by the user. User input commands, functions, and components contemplated for use with the present invention are specifically described in U.S. patent application Ser. No. 11/166,891, by Dubrovsky et al., filed on Jun. 24, 2005, entitled Remote Control Scheduler and Method for Autonomous Robotic Device, the entire disclosure of which is herein incorporated by reference it its entirety. Specific modes of user interaction are also described herein.
• Sensor Module
• Therobot10 includes asensor module1100. Thesensor module1100 includes a plurality of sensors attached to the chassis and integrated with the robot subsystems for sensing external conditions and for sensing internal conditions. In response to sensing various conditions, thesensor module1100 can generate electrical signals and communicate the electrical signals to thecontroller1100. Individual sensors can perform any of various different functions including, but not limited to, detecting walls and other obstacles, detecting drop offs in the surface (sometimes referred to as cliffs), detecting debris on the surface, detecting low battery power, detecting an empty cleaning fluid container, detecting a full waste container, measuring or detecting drive wheel velocity distance traveled or slippage, detecting cliff drop off, detecting cleaning system problems such rotating brush stalls or vacuum system clogs or pump malfunctions, detecting inefficient cleaning, cleaning surface type, system status, temperature, and many other conditions. In particular, several aspects of thesensor module1100 as well as its operation, especially as it relates to sensing external elements and conditions are specifically described in U.S. Pat. No. 6,594,844, by Jones, entitled Robot Obstacle Detection System, and U.S. patent application Ser. No. 11/166,986, by Casey et al., filed on Jun. 24, 2005, entitled Obstacle Following Sensor Scheme for a Mobile Robot, the entire disclosures of which are herein incorporated by reference it their entireties.
• Therobot10 includes control and sensor components in close proximity to the wet cleaning components. As described above, therobot10 can be sized to fit within any of various different confined spaces typically encountered in household cleaning applications. Accordingly, much of the volume ofrobot10 is occupied by theliquid storage1500,liquid applicator1400, andcollection subsystems1300, each of which can include the transport of water, solvents, and/or waste throughout therobot10. As distinguished from many dry vacuuming robots that do not use wet cleaners and do not generate waste, some of the sensors and control elements of therobot10 are sealed and/or positioned to minimize exposure to water or more damaging cleaning fluids or solvents. As distinguished from many industrial cleaners, some of the sensors and control elements of therobot10 are packaged in close proximity to (e.g., within less than about an inch of) cleaning elements, cleaning fluids, and/or waste.
• Referring toFIGS. 7,20, and21A-C, thecontroller1000 can be implemented using a printed circuit board (PCB)101 carried by thechassis100 and secured in any of various different positions along the chassis. For example, the PCB can be carried between a bottom portion of thechassis100 and aPCB cover103 such that, as described below, a potting material can be introduced around thePCB101 and the weight of the potting material can act as a ballast to lower the center of gravity of therobot10. Theentire PCB101 can be fluid sealed, either in a water resistant or waterproof housing having at least JIS grade 3 (mild spray) water/fluid resistance, but grade 5 (strong spray), grade 7 (temporary immersion), and ANSI/IEC 60529-2004 standards for equivalent water ingress protection are also desirable. In some implementations, the main control PCB is sealed in a JIS grade 3-7 housing (1) by a screwed-down and gasketed cover over the main housing; (2) by a welded, caulked, sealed, or glued cover secured to the main housing; (3) by being pre-assembled in a water resistant, water-tight, water-proof, or hermetically sealed compartment or module; or (4) by being positioned in a volume suitable for potting or pre-potted in resin or the like.
• Referring to FIGS.20-21A-C, in one implementation, thePCB101 is disposed between the chassis100 (e.g., a bottom portion of the chassis) and thePCB cover103, which is engageable with the baseplate200 (seeFIG. 7). The space defined between thechassis100 and thePCB cover103 is filled with apotting material105 such that the potting material substantially surrounds thePCB101 to isolate the PCB from fluid communication with theliquid applicator1400 and/or from fluid communication with thecollection assembly1300. In some implementations, thecontroller1000 includes components in addition or to the PCB. For example, the controller can include a plurality of proximity sensors and/or a plurality cliff sensors, and thepotting material105 can be disposed about these components as well.
• The potting material is a surface mount component grade potting material which, as used herein, is a potting material that having a low coefficient of linear thermal expansion (e.g., a coefficient of linear thermal expansion of less than about 250 ppm/° C.) and/or a low glass transition temperature (e.g., a glass transition temperature of less than about −40° C.). The expansion and contraction of such potting material through temperature extremes spanning −40° C. to 150° C. places an acceptable amount of stress on surface mount components embedded in the potting material such that the surface mount components do not become dislodged.
• Thepotting material105 is a two-component urethane with a set time of less than about ten minutes. Such a ratio can be useful, for example, for simplifying the mixing process used during manufacturing.
• As indicated above, thepotting material105 can be added to therobot10 in a quantity sufficient to act as a ballast to lower the center of gravity of the robot. In some implementations, the potting material is between about 5 percent and about 20 percent of the overall mass of therobot10. For example, thepotting material105 can have a mass of between about 110 g and about 140 g. Given the volume available for the addition of thepotting material105, a potting material with a specific gravity of between about 1.2 and about 1.6 can be used to add this range of mass to therobot10.
• In addition to isolating thePCB101 from fluid communication with theliquid applicator1400, thepotting material105 has a higher thermal conductivity than air and can, thus, facilitate dissipation of heat generated by thePCB101 during operation of therobot10. For example, the potting material can have a thermal conductivity of about 0.15 W/(m·K) to about 0.40 W/(m·K).
• Thepotting material105 is disposed around thePCB105 by placing thechassis100 in a substantially vertical orientation, with a substantially flatrear portion102 of the chassis below aforward portion111 of the chassis100 (e.g., by placing the substantially flatrear portion102 of the chassis on a table). With thechassis100 in this vertical orientation, thepotting material105 is introduced into the space between thechassis100 and thePCB cover103 by introducing the potting material through avalve107 defined by thePCB cover103. Thevalve107 is defined through the portion of thePCB cover103 disposed toward therear portion102 of the chassis. Accordingly, thepotting material105 is moved in a vertical direction over thePCB100 disposed between thechassis100 and thePCB cover103. Through such vertical movement, thepotting material105 displaces air from the space between thechassis100 and thePCB cover103 such that the air exits through theforward portion111 of thechassis100.
• Thepotting material105 has an uncured viscosity at room temperature between about 8000 centipoise and about 10000 centipoise for curing in a short period of time (e.g., less than an hour). However, in some implementations, thepotting material105 is heated to an uncured viscosity of between about 3000 centipoise to about 5000 centipoise before the potting material is introduced through thevalve107. Such heating can facilitate flow of thepotting material105 aroundwires115 while reducing the likelihood of formation of air pockets around thewires115. After a predetermined mass ofpotting material105 is introduced into the volume in which thePCB101 is disposed, the potting material cures around thePCB101. In some implementations, thepotting material105 seals theorifice107. For example, the orifice can be an x-shape and the curedpotting material105 seals together the portions of material forming the x-shape.
• Many sensor elements have a local small circuit board, sometimes with a local microprocessor and/or A/D converter and the like, and these components are often sensitive to fluids and corrosion. In some implementations, sensor circuit boards distributed throughout the body of therobot10 are sealed in a JIS grade 3-7 housing in a similar manner. In some implementations, multiple circuit boards, including at least the main circuit board and one remote circuit board (e.g., a user interface circuit board) several centimeters from the main board, may be sealed by a single matching housing or cover. For example, all or some of the circuit boards can be arranged in a single plastic or resin module having extensions which reach to local sensor sites. Additionally or alternatively, a distributed cover can be secured over all of the circuit boards. Exposed electrical connections and terminals of sensors, motors, or communication lines can be sealed in a similar manner, with covers, modules, potting, shrink fit, gaskets, or the like. In this manner, substantially the entire electrical system is fluid-sealed and/or isolated from cleaning liquid and/or waste. Any and all electrical or electronic elements defined herein as a circuit board, PCB, detector, sensor, etc., are candidates for such sealing.
• In some implementations, electrical components (e.g., a PCB, the fan112) of therobot10 can be substantially isolated from moisture and/or waste using a wire seal. Details of such a wire seal are disclosed in U.S. patent application Ser. No. 12/118,250, entitled “Autonomous Coverage Robot Sensing,” the entire contents of which are incorporated herein by reference.
• Omni-Directional Receiver
• Referring toFIGS. 7,12, and19, therobot10 includes an omni-directional receiver410 disposed along a bottom portion ofsignal channeler402. For the purpose of illustration,FIG. 19 shows thesignal channeler402 withoutwaste intake conduits234 and withoutfan intake conduit114 attached. Several aspects of the omni-directional sensor410 as well as its operation, especially as it relates to the navigation and direction of therobot10 are specifically described in U.S. patent application Ser. No. 11/633,869, by Ozick et al., entitled “AUTONOMOUS COVERAGE ROBOT NAVIGATION SYSTEM,” the entire disclosure of which is herein incorporated by reference in its entirety.
• The omni-directional receiver410 is positioned on thesignal channeler402, substantially off-center from (e.g., substantially forward of) the centralvertical axis20 of therobot10. The off-center positioning of omni-directional receiver410 can allow thecontrol module1000 to be more sensitive in one direction. In some implementations, such sensitivity allows therobot10 to discern directionality during maneuvers. For example, if the omni-directional receiver410 receives a signal, thecontrol module1000 can direct therobot10 to turn in place until the signal received by the omni-directional receiver410 weakens and/or disappears. In some implementations, thecontrol module1000 directs therobot10 to drive in the direction in which a weakened signal and/or no signal is detected (e.g., away from the source of the signal) and, if therobot10 turns 360 degrees and is still stuck in the beam, therobot10 will turn 180 degrees and drive forward in a last attempt to get free.
• As shown inFIG. 19, the omni-directional receiver410 can be disposed substantially along abottom portion403 of thesignal channeler402, facing toward thechassis100. As compared to a configuration in which an omni-directional receiver extends from a top surface of the signal channeler (e.g., forming the highest point of the robot), disposing the omni-directional receiver410 along thebottom portion403 of thesignal channeler402 can lower the overall height profile of therobot10. Additionally or alternatively, this configuration can protect the omni-directional receiver410 from damage as therobot10 maneuvers through tight spaces and/or bumps into an overhead obstruction.
• In some implementations, the omni-directional receiver410 can be configured to receive transmissions of infrared light (IR). In such implementations, a guide (e.g. a light pipe) can guide emissions reflected off a conical reflector and channel them to an emission receiver.
• The omni-directional receiver410 is disposed substantially within acavity414 defined by ahousing412. Acover416 extends over thecavity414 and forms a substantially water-tight seal with thehousing412 to enclose the omni-directional receiver410. In some implementations, thecover416 is releasably attached to thehousing412 to allow, for example, replacement and/or repair of the omni-directional receiver410. The substantially water-tight seal between thehousing412 and thecover414 can include any of various different seals. Examples of seals include epoxy, ultrasonic welding, potting wells, welded interfaces, plugs, gaskets, and polymeric membranes.
• During use, an active external device (e.g., a navigation beacon) can send a signal toward thesignal channeler402. Thesignal channeler402 is configured for total internal reflection of the incident signal such that the signal moves substantially unattenuated within the signal channeler402 (e.g., within the material forming the signal channeler). In some implementations, thesignal channeler402 is a substantially uniform layer of polished polycarbonate resin thermoplastic. The signal moving through thesignal channeler402 is internally reflected through thesignal channeler402. The omni-directional receiver410 is arranged to detect signal reflected through the signal channeler. The omni-directional receiver416 is in communication (e.g., electrical communication) with thecontrol module1000. Upon detecting a signal traveling through thesignal channeler402, the omni-directional receiver416 sends a signal to thecontrol module1000.
• In some implementations, thecontrol module1000 responds to the signal from the omni-directional receiver416 by controlling thewheel modules500,501 to navigate therobot10 away from the source of the signal. For example, as an initial escape procedure, thecontrol module1000 can direct thewheel modules500,501 to move therobot10 in a rearward direction. Such movement in the rearward direction, can position therobot10 further away from the beam such thatrobot10 can determine directionality (e.g., spin out of the beam) by rotating substantially in place. In a subsequent escape procedure, thecontroller1000 can direct therobot10 in a direction away from the signal.
• In some implementations, therobot10 is configured to detect the virtual wall pattern and is programmed to treat the virtual wall pattern as a room wall so that the robot does not pass through the virtual wall pattern.
• In some implementations, therobot10 includes a radio to control the state of the navigation beams through commands transmitted over a packet radio network.
• Control module1000 can be configured to maneuver therobot10 about a first area while therobot10 is in a cleaning mode. In the cleaning mode, therobot10 can be redirected in response to detecting a gateway marking emission (e.g., from a beacon). In addition, thecontrol module1000 can be configured to maneuver therobot10 through a gateway into the second bounded area while in a migration mode.
• In some implementations, thecontrol module1000 is configured to move therobot10 in a first bounded area in the cleaning mode for a preset time interval. When the present time interval elapses, thecontrol module1000 can move therobot10 in a migration mode. While in migration mode, thecontroller1000 can direct thewheel modules500,501 to maneuver the robot while substantially suspending the wet cleaning process. In some implementations, the migration mode can be initiated when the omni-directional receiver410 encounters the gateway marking emission a preset number of times.
• Wall Follower
• Dust and dirt tend to accumulate at room edges. To improve cleaning thoroughness and navigation, therobot10 can follow walls. Additionally or alternatively, therobot10 can follow walls as part of a navigation strategy (e.g., a strategy to promote full coverage). Using such a strategy, the robot can be less prone to becoming trapped in small areas. Such entrapments could otherwise cause the robot to neglect other, possibly larger, areas.
• Using a wall follower, the distance between the robot and the wall is substantially independent of the reflectivity of the wall. Such consistent positioning can allow therobot10 to clean with substantially equal effectiveness near dark and light colored walls alike. The wall follower includes a dual collimination system including an infrared emitter and detector. In such a collimination system, the field of view of the infrared emitter and detector can be restricted such that there is a limited, selectable volume where the cones of visibility intersect. Geometrically, the sensor can be arranged so that it can detect both diffuse and specular reflection. This arrangement can allow the wall following distance of therobot10 to be precisely controlled, substantially independently of the reflectivity of the wall. The distance that therobot10 maintains between the robot and the wall is independent of the reflectivity of the wall.
• Referring toFIG. 4, therobot10 includes awall follower sensor310 disposed substantially along the right side of thebumper300. Thewall follower sensor310 includes anoptical emitter312 substantially forward of aphoton detector314. In some implementations, the position of thewall follower sensor310 and theoptical emitter312 can be reversed such that thewall follower sensor310 is substantially forward of theoptical emitter312. Details of thewall follower sensor310 are disclosed in U.S. patent application Ser. No. 12/118,250, entitled “Autonomous Coverage Robot Sensing,” the entire contents of which are incorporated herein by reference.
• Bump Sensors
• Bump sensors can be used to detect if the robot physically encounters an obstacle. Bump sensors can use a physical property such as capacitance or physical displacement within the robot to determine the robot has encountered an obstacle.
• Referring toFIG. 7, thechassis100 carries at least onebump sensor330 along a forward portion of thechassis100. In some implementations, bumpsensors330 are substantially uniformly positioned on either side of the fore-aftaxis22 and are positioned at substantially the same height along the centervertical axis20. As described above,bumper300 is attached tochassis100 byhinges110 such that thebumper300 can move a distance rearward along the fore-aftaxis22 if thebumper300 encounters an obstacle. In the absence of a bump, thebumper300 is hingedly supported on thechassis100 at a short distance substantially forward of the at least onebump sensor330. If thebumper300 is moved rearward (e.g., through an encounter with an obstacle), thebumper300 can press on one or more of the at least onebump sensors330 to create a bump signal detectable by thecontrol module1000.
• Details of the at least onebump sensor330 are disclosed in U.S. patent application Ser. No. 12/118,250, entitled “Autonomous Coverage Robot Sensing,” the entire contents of which are incorporated herein by reference.
• Cliff Sensor
• Cliff sensors can be used to detect if a portion (e.g., a forward portion) of the robot has encountered an edge (e.g., a cliff). Cliff sensors can use an optical emitter and photon detector pair to detect the presence of a cliff. In response to a signal from a cliff detector, the robot can initiate any of various different cliff avoidance behaviors. Details of cliff sensors carried onbumper300 are disclosed in U.S. patent application Ser. No. 12/118,250, entitled “Autonomous Coverage Robot Sensing,” the entire contents of which are incorporated herein by reference.
• Stasis Sensor
• A stasis sensor can be used to detect whether or not the robot is in fact moving. For example, a stasis sensor can be used to detect if the robot is jammed against an obstacle or if the drive wheels are disengaged from the floor, as when the robot is tilted or becomes stranded on an object. In a wet cleaning application, a stasis sensor can detect whether the wheels are slipping on a cleaning liquid applied to the surface. In such circumstances, the drive wheels may spin when the mobile robot applies power to them, but the robot is not moving. Details of stasis sensors for detecting whether the robot is moving are disclosed in U.S. patent application Ser. No. 12/118,250, entitled “Autonomous Coverage Robot Sensing,” the entire contents of which are incorporated herein by reference.
• Power Module/Interface Module
• Referring toFIGS. 1-7, thepower module1200 delivers electrical power to all of the major robot subsystems. Thepower module1200 includes a self-contained power source releasably attached to thechassis100, e.g., a rechargeable battery, such as a nickel metal hydride battery, or the like. In addition, the power source is configured to be recharged by any of various different recharging elements and/or recharging modes. In some implementations, the battery can be replaced by a user when the battery becomes discharged or unusable. Thecontroller1000 can also interface with thepower module1200 to control the distribution of power, to monitor power use and to initiate power conservation modes as required.
• Therobot10 can include one ormore interface modules1700. Eachinterface module1700 is attached to thechassis100 and can provide an interconnecting element or port for interconnecting with one or more external devices. Interconnecting elements are ports can be accessible on an external surface of therobot10. Thecontroller1000 can also interface with theinterface modules1700 to control the interaction of therobot10 with an external device. In particular, one interface module element can be provide for charging the rechargeable battery via an external power supply or power source such as a conventional AC or DC power outlet. The interface module for charging the rechargeable battery can include a short-circuit loop that will prevent the rechargeable battery from taking charge if there is water in the charge port of therobot10. In some implementations, the rechargeable battery includes a fuse that will trip if there is water in the battery recharging path.
• Another interface module element can be configured for one or two way communications over a wireless network and further interface module elements can be configured to interface with one or more mechanical devices to exchange liquids and loose particles therewith, e.g., for filling a cleaning fluid reservoir.
• Active external devices for interfacing with therobot10 can include, but are not limited to, a floor standing docking station, a hand held remote control device, a local or remote computer, a modem, a portable memory device for exchanging code and/or date with therobot10 and a network interface for interfacing therobot10 with any device connected to the network. In addition, theinterface modules1700 can include passive elements such as hooks or latching mechanisms for attaching therobot100 to a wall for storage or for attaching the robot to a carrying case or the like.
• In some implementations, an active external device can confine therobot10 in a cleaning space such as a room by emitting a signal in a virtual wall pattern. Therobot10 can be configured to detect the virtual wall pattern (e.g., using an omni-directional receiver as described above) and is programmed to treat the virtual wall pattern as a room wall so that the robot does not pass through the virtual wall pattern. Such a configuration is described in U.S. Pat. No. 6,690,134 by Jones et al., entitled Method and System for Robot Localization and Confinement, the entire disclosure of which is herein incorporated in its entirety.
• In some implementations, an active external device includes a base station used to interface with therobot10. The base station can include a fixed unit connected with a household power supply, e.g., an AC power wall outlet and/or other household facilities such as a water supply pipe, a waste drain pipe and a network interface. Therobot10 and the base station can each be configured for autonomous docking and the base station can be further configured to charge therobot power module1200 and to service the robot in other ways. A base station and autonomous robot configured for autonomous docking and for recharging the robot power module are described in U.S. patent application Ser. No. 10/762,219, by Cohen, et al., filed on Jan. 21, 2004, entitled Autonomous Robot Auto-Docking and Energy Management Systems and Methods, the entire disclosure of which is herein incorporated by reference in its entirety.
• Other robot details and features combinable with those described herein may be found in U.S. patent application Ser. No. 12/118,117, entitled “COMPACT AUTONOMOUS COVERAGE ROBOT”, U.S. Pre-grant Publications 2008/00652565, 2007/0244610, and 2007/0016328, 2006/0200281, and 2003/0192144, and also U.S. Pat. Nos. 6,748,297 and 6,883,201. The disclosures of these prior applications, publications, and patents are considered part of the disclosure of this application and are hereby incorporated by reference in their entireties.

Claims (17)

1. A surface treatment robot comprising:

a robot body having a forward portion, a rear portion, the forward portion preceding the rear portion as the robot moves in a forward direction over a cleaning surface;

a cleaning assembly carried by the robot body and configured to remove debris from the cleaning surface; and

a right drive wheel and a left drive wheel, each drive wheel rotatable about an axis parallel to the cleaning surface and transverse to the forward direction of movement of the robot over the cleaning surface, each drive wheel comprising

a rim

a tire disposed about a circumference of a respective drive wheel, the tire comprising

a base having a first side and a second side substantially opposite the first side,

a first and second set of treads, each tread of the first and second set of treads extending radially from the first side of the base toward the cleaning surface, each tread of the first and second set of treads being elongate in a direction substantially parallel to the transverse axis, and each tread of the first set of treads circumferentially offset from each of the treads of the second set of treads.

2. The surface treatment robot ofclaim 1 wherein each tread of the first and second set of treads has at least one substantially square edge disposed toward the cleaning surface.

3. The surface treatment robot ofclaim 1 wherein each tread of the first and second set of treads has substantially the same width in the circumferential direction of the tire.

4. The surface treatment robot ofclaim 3 wherein each tread of the first and second set of treads is circumferentially spaced from a preceding tread of the respective set of treads by a distance about three times the circumferential width of the tread.

5. The surface treatment robot ofclaim 1 wherein each tread extends radially from the base by a distance between about ⅕ to about ½ of a radial thickness of the base.

6. The surface treatment robot ofclaim 1 wherein the tire comprises natural rubber and between about 20 percent and about 30 percent particulate matter.

7. The surface treatment robot ofclaim 6 wherein the particulate matter includes one or more of the following: kaolin clay and calcium carbonate.

8. The surface treatment robot ofclaim 1 wherein each wheel is disposed rear of at least a portion of the cleaning assembly as the robot moves in the forward direction over the cleaning surface.

9. The surface treatment robot ofclaim 8 wherein the cleaning assembly comprises a liquid applicator, and at least a portion of the liquid applicator is disposed forward of each wheel as the robot moves in the forward direction over the cleaning surface.

10. The surface treatment robot ofclaim 9 wherein the cleaning assembly comprises a vacuum assembly, and at least a portion of the vacuum assembly is disposed rear of each wheel as the robot moves in the forward direction over the cleaning surface.

11. The surface treatment robot ofclaim 1 wherein each tire comprises a third and fourth set of treads extending radially from the second side of the base toward the respective rim.

12. The surface treatment robot ofclaim 11 wherein the third set of treads is substantially opposite the first set of treads and the fourth set of treads is substantially opposite the second set of treads.

13. The surface treatment robot ofclaim 12 wherein each tread of third set of treads is circumferentially offset from each tread of the first set of treads and each tread of the fourth set of treads is circumferentially offset from each tread of the second set of treads.

14. The surface treatment robot ofclaim 13 wherein at least a portion of the base is movable toward the wheel when a tread of the first or second set of treads contacts the cleaning surface.

15. The surface treatment robot ofclaim 11 wherein the third set of treads and the fourth set of treads define at least a portion of channel extending circumferentially around the tire, along the second surface of the base.

16. The surface treatment robot ofclaim 15 wherein each wheel includes a circumferential ridge extending radially outward, toward the cleaning surface, the circumferential ridge engageable with the channel at least partially defined by the third and fourth set of treads.

17. The surface treatment robot ofclaim 11 wherein the tire is reversible such that the third and fourth sets of treads extend toward the cleaning surface and the first and second sets of treads extend toward the respective rim.

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