US20080167753A1 - Area Coverage With An Autonomous Robot - Google Patents

Abstract

There is therefore provided, in accordance with a preferred embodiment of the present invention, a robotic system for systematically moving about an area to be covered. The system includes at least one boundary marker (48) located along the outer edge of the area to be covered, a robot (40) with a navigation system (41) that navigated the robot (40) in generally straight, parallel lines from an initial location and turns the robot (40) when the robot (40) encounters one of the boundary markers (48), thereby to systematically move about the area to be covered. The sensor unit (43) senses proximity to one of the at least one boundary marker (48).

Description

RELATED APPLICATIONS
• This application is a continuation of U.S. patent application Ser. No. 11/644,383, filed Dec. 22, 2006, now U.S. Pat. No. ______, which is a continuation of U.S. patent application Ser. No. 10/987,486, filed Nov. 12, 2004, now U.S. Pat. No. 7,155,309, which is a continuation of U.S. patent application Ser. No. 10/445,658, filed, May 27, 2003, now U.S. Pat. No. 6,885,912, which is a continuation of U.S. patent application Ser. No. 09/700,211, filed Apr. 13, 2001, now U.S. Pat. No. 6,615,108, and is a § 371 of PCT/IL99/00248, filed May, 11, 1999. U.S. patent application Ser. Nos. 11/644,383, 10/987,486, 10/445,658 and Ser. No. 09/700,211, and PCT/IL99/00248, are incorporated by reference herein.
FIELD OF THE INVENTION
• The present invention relates to autonomous robots generally and to autonomous robots which move through an area in particular.
BACKGROUND OF THE INVENTION
• Autonomous robots are known in the art and have been implemented as household appliances, such as a lawnmower or a vacuum cleaner. These household appliances operate by moving about an area to be processed such that the entire area is covered by the end of the operation.
• Reference is now made toFIGS. 1A and 1B which illustrate the operation of one exemplary autonomous robot, described in U.S. patent application Ser. No. 08/554,691, filed 7 Nov. 1995, and assigned to the common assignees of the present invention. U.S. patent application Ser. No. 08/554,691 is incorporated herein by reference.FIG. 1A illustrates the area in which therobot10 operates andFIG. 1B illustrates the elements, in block diagram form, ofrobot10.
• Theautonomous robot10 operates within an area marked withboundary markers12A. If there are fixedobstacles14 in the area, such as flower beds, trees, columns, walls, etc., these obstacles are rimmed withfurther boundary markers12B. The boundary markers12 can be of any suitable type, such as an electrified wire, bar coded posts, radioactive posts, etc. The term “marker” will be used herein for both posts and wires.
• As shown inFIG. 1B, therobot10 includes anavigation system20 which receives data from anedge sensor22 which senses when therobot10 approaches a boundary marker12 where, if the marker is a continuous wire, the term “marker” indicates the section of the wire near the current location of the robot. Thenavigation system20 also receives data from anodometer24 which measures the distance therobot10 has moved and acompass26 which measures the current location of therobot10.
• Initially, therobot10 is placed within the area to be covered. Therobot10 moves toward the boundary (if it did not begin near it) and then, as indicated byarrows32, moves along the boundary, following the boundary markers12. During this process, therobot10 uses the location information from the compass to produce a map28 (FIG. 1B) of the area to be covered.
• Once the map is complete, therobot10 moves about the area to be covered. Whenever it approaches a boundary marker12, as sensed by theedge sensor22, therobot10 changes direction and continues until it reaches another boundary marker12. If the boundary marker12 appeared close to, but not at, its expected position,navigation system20 updates themap28 to match the new information.
• If the boundary marker12 is sensed substantially within the area, as determined by a comparison of the output of thecompass26 and the information in themap28, the boundary marker12 must be one which surrounds theobstacle14. Therobot10 changes direction and continues until it reaches another boundary marker12. Therobot10 moves about the area to be covered until it has determined that all sections of themap28 have been covered.
• However, it will be appreciated that creating themap28 of the shape of the area to be covered is time consuming. Due to the inaccuracies of thecompass26 andodometer24, it is also typically error prone.
SUMMARY OF THE INVENTION
• Applicants have realized that, if the robot works systematically within the area to be covered, there is no need to create the map.
• It is therefore an object of the present invention to provide an autonomous robot, for performing area coverage, which does not create a map of the area to be covered.
• There is therefore provided, in accordance with a preferred embodiment of the present invention, a robotic system for systematically moving about an area to be covered. The system includes at least one boundary marker located along the outer edge of the area to be covered, a robot with a navigation system and a sensor unit. The navigation system navigates the robot in generally straight, parallel lines from an initial location and turns the robot when the robot encounters one of the boundary markers, thereby to systematically move about the area to be covered. The sensor unit senses proximity to one of the at least one boundary marker.
• Additionally, in accordance with a preferred embodiment of the present invention, the sensor unit includes a unit for indicating proximity to an obstacle within the area to be covered and the navigation system includes a unit for turning the robot when the unit for indicating indicates proximity to an obstacle.
• Moreover, in accordance with a preferred embodiment of the present invention, the unit for indicating is either a contact sensor or a proximity sensor.
• Further, in accordance with a preferred embodiment of the present invention, the navigation system includes a unit for counting the number of laps needed to cover the area between an obstacle and a boundary marker.
• Still further, in accordance with a preferred embodiment of the present invention, the system includes at least one obstacle marker located along the outer edge of the obstacle.
• Moreover, in accordance with a preferred embodiment of the present invention, the at least one boundary marker is an electrified wire receiving a first signal and the at least one obstacle marker is an electrified wire receiving a second signal.
• Alternatively, in accordance with a preferred embodiment of the present invention, the at least one boundary marker is a post having a first bar code and the at least one obstacle marker is a post having a second bar code.
• There is also provided, in accordance with a preferred embodiment of the present invention, a robotic system for systematically moving about an area to be covered. The system includes at least one boundary marker located along the outer edge of the area to be covered, at least one obstacle marker located along the outer edge of an obstacle within the area to be covered, a robot for moving about the area to be covered and a sensor unit for sensing proximity to the boundary and obstacle markers and for differentiating between the boundary and obstacle markers.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the appended drawings in which:
• FIG. 1A is a schematic illustration of an area to be covered and the initial movement of a prior art robot within the area;
• FIG. 1B is a block diagram illustration of the prior art robot;
• FIG. 2A is a schematic illustration of an area to be covered and the movement of a robot of the present invention within the area;
• FIG. 2B is a block diagram illustration of a robot, constructed and operative in accordance with a preferred embodiment of the present invention;
• FIG. 3A is a schematic illustration of one embodiment of boundary and obstacle markers;
• FIG. 3B is a timing diagram operative for the embodiment ofFIG. 3A;
• FIG. 3C is a graphical illustration of the signal strength of a magnetic sensor as a function of distance from the markers ofFIG. 3A; and
• FIG. 4 is a schematic illustration of an alternative embodiment of boundary and obstacle markers.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
• Reference is now made toFIGS. 2A and 2B which illustrate the movement of arobot40 of the present invention and the elements of the robot, respectively. Similar reference numerals refer to similar elements.
• In accordance with a preferred embodiment of the present invention,robot40 does not create a map of the area to be covered. Instead, it systematically scans within the area, moving in a straight direction from one boundary marker to the next. To do so, it must initially be placed relatively close to one extreme edge of the boundary, for example, atstarting point42, and faced in the desired direction of scanning.
• As can be seen inFIG. 2B, therobot40 utilizes theodometer24 andcompass26 but comprises anavigation system41 and asensor system43, shown as twosensors44 and46, for separately sensing the boundary and the obstacles, respectively. Accordingly, there can be two different types of markers,boundary markers48 andobstacle markers50. Theboundary markers48 andobstacle markers50 can be of any suitable types, as detailed hereinbelow.
• Alternatively, for obstacles which stick above the ground, such as trees and furniture, the obstacle sensors can be proximity and/or contact sensors. For this system, there is no need for obstacle markers and only boundary markers are utilized.
• It will be appreciated that, without a map,robot40 does not know its position within the area to be scanned; it only knows its absolute position. Using position information,robot40 scans the area, moving in a generally straight line from one marker to the next, as determined bysensor system43. Using the output ofcompass26, thenavigation system41 then turnsrobot40 generally 180° whenever it encounters a new marker. Thenavigation system41 also ensures that the new “lap” is beside, and possibly slightly overlapping, the previous lap, thereby to ensure full coverage of the area to be covered. This is described in detail in U.S. patent application Ser. No. 08/554,691.
• In general,robot40 moves in generally straight, parallel lines between twoboundary markers48, as indicated byarrows52. However, ifsensor system43 indicates that therobot40 is close to anobstacle marker50, thenavigation system41 causes the scan to occur betweenboundary markers48 andobstacle markers50, as indicated byarrows54, counting the number of laps until the obstacle is passed. The next lap,arrow38, brings therobot40 to aboundary marker48 on the other side of theobstacle14. Therobot40 then performs a scan in the opposite direction, between theboundary markers48 and theobstacle markers50 to cover the area behind theobstacle14. This scan is shown witharrows56 and involves the same number of laps as for the first side of theobstacle14.
• Once the scan behind theobstacle14 is finished, therobot40 follows theboundary markers48 until it reaches the point, labeled60, where it began the scan behind theobstacle14, at which point, it continues normal scanning betweenboundary markers48.
• Alternatively, the scan behind theobstacle14 can be performed without counting laps. Instead, the scan continues until theobstacle14 has been passed. This requires noting the location of therobot10 near the boundary when therobot10 begins the scan behind theobstacle14 so that therobot10 can be returned to that location once the scan behind theobstacle14 is finished.
• It will be appreciated that, by scanning systematically between boundary and obstacle markers, the present invention covers the area to be covered without having to produce a map of the area.
• Reference is now made toFIGS. 3A,3B and3C, which respectively illustrate one set of boundary and obstacle markers formed of wires, a timing diagram for the markers and a graph of signal strength as a function of distance from the wire.
• In this embodiment, both theboundary marker48 and themultiple obstacle markers50 are formed of wires connected to apower supply60 via awave generator62. Thewave generator62 provides one type of signal for theboundary marker48 and another type of signal to all of theobstacle markers50.
• For example, the signal formarker48 might be of one frequency while the signal formarkers50 might be of a second frequency. In this embodiment, thewave generator62 includes two separate elements, each of which produces one of the two frequencies and provides it to the appropriate set of wires.
• Alternatively and as shown inFIG. 3B, the signals can be time shared. In this embodiment, ashort synchronization pulse64 is followed by aboundary signal66 formarker48 after which anobstacle signal68 formarkers50 is provided. The sequence repeats. The marker is determined to be a boundary marker or an obstacle marker by the length of time from the mostrecent synchronization pulse64.
• It will be appreciated that, for both embodiments, the robot, labeled70, has a singlemagnetic sensor72 for sensing the signals fromwave generator62 and aprocessor74 for determining if the type of signal based on the frequency of the transmission, in the first embodiment, or based on the timing of the transmission, in the second embodiment. Alternatively, for the second embodiment, therobot70 can have separate receivers, each tuned to the relevant frequency, and separate processors for each receiver to determine if the received signal is strong enough to indicate proximity.
• FIG. 3C schematically illustrates the strength of the signal as a function of distance from the location of the wire. When thesensor72 is on top of the wire, no signal is received (point80). As thesensor72 moves away from the wire, the signal increases sharply, reaching apeak82 within 50 cm. The signal then slowly decays as thesensor72 moves further away from the wire. Thus, as therobot70 approaches the wire, the signal will slowly increase in strength. Acceptable proximity can be defined as once peak82 has been reached or any time afterpeak82 has been reached.
• Reference is now made toFIG. 4 which illustrates an alternative embodiment of the boundary andobstacle markers48 and50, respectively. In this embodiment, the markers are formed of posts, each having a different bar code written thereon.FIG. 4 uses squares to indicate theboundary markers48 and circles to indicateobstacle markers50. In this embodiment, as in the previous embodiment, there is a single sensor. In this case, the sensor is a bar code reader which provides one type of signal when it reads the boundary marker code and another type of signal when it reads the obstacle marker code.
• Alternatively, theboundary markers40 can be formed of a wire and the obstacle markers can be formed of bar coded posts, or vice versa. A further alternative, discussed hereinabove, uses markers only for the boundary and contact or proximity sensors for sensing the proximity of an obstacle.
• It will be appreciated that the markers can be formed of any suitable marking unit and that the robot includes a sensor or sensors capable of recognizing the information which the marking unit provides to determine proximity. Such sensors and marking units are discussed in detail in U.S. patent application Ser. No. 08/554,691. The number of sensors used is of little importance to the present invention; however, the information from the types of sensors must be separable.
• It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein above. Rather the scope of the invention is defined by the claims that follow:

Claims (5)

1. A method for operating a robot comprising:

moving the robot over a surface in accordance with a first scanning pattern;

detecting at least one obstacle; and,

moving the robot over the surface in accordance with a second scanning pattern while following the at least one obstacle along a path corresponding to at least a portion of the periphery of the at least one obstacle in response to the at least one obstacle being detected.

2. The method ofclaim 1, wherein the first scanning pattern is the same as the second scanning pattern.

3. The method ofclaim 1, wherein the first scanning pattern is different from the second scanning pattern.

4. The method ofclaim 2, wherein the first scanning pattern and the second scanning pattern include the robot traveling in substantially straight parallel lines.

5. The method ofclaim 4, wherein the substantially straight parallel lines are substantially free of repetition.

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