US3744586A - Automatically steered self-propelled vehicle - Google Patents

Abstract

A self-propelled vehicle is automatically reversed and steered to a new path if sensors thereon sense an obstruction surrounding an area, or an obstacle in the area so that the vehicle moves forward, rearward and laterally over the entire unobstructed area for treating the same with a tool, such as a brush or agricultural implement. The forward and rearward movements are maintained along straight paths independently of irregularities prevelant in the area, tolerances in the steering control system of the vehicle or other such influences.

Description

ted States Patent 1191 1111 3,744,586 Leinauer July 10, 1973 [54] AUTOMATICALLY STEERED 2,750,583 6/ I956 McCullough l80/79.I X SELILPROPELLED VEHICLE 2,996,621 8/1961 Barrett 180/791X 3,43l,996 3/1969 Giles et al. l80/98 [75] Inventor: Erich Lelnauer, 3,669,208 6/l972 Brooke 180/98 Ludwigsburg, Germany 3,152,3l7 10/1964 Mayer 340/104 X [73] Assignee: Robert Bosch Gmbll, Stuttgart, FOREIGN PATENTS OR APPLICATIONS 920,881 3/1963 Great Britain l80/79.l

[22] Filed: Oct. 5, 1971 Primary ExammerBen amm Hersh pp N05 186,678 Assistant Examiner-Lcslie J. Paperner Attorney-Michael S. Striker [30] Foreign Application PriorityData 7' '7 0m. 7, 1970 GermanyP 20 49 136.5 [57] ABSTRACT A self-propelled vehicle is automatically reversed and [52] US. Cl 180/79.1, 180/98, 250/202, steered to a new p if Sensors thereon Sense an 340/282 343/7 5]) struction surrounding an area, or an obstacle in the [51] Int. (:1. B6211 1/24 area 89 that the vehicle moves forward, rearward and [58] Field 01 Search ISO/79.1, 98; laterally over th ntir unobstructed area for treating 313 5 7; 340 2 2; 250302; 343 7 5]) the same with a tool, such as a brush or agricultural implement. The forward and rearward movements are 5 References Ci d maintained along straight paths independently of irreg- UNITED STATES PATENTS ularities prevelant in the area, tolerances in the steering 3,513,931 5 1970 Warner et al 180/98 control System of the Vehlcle or other such mfluences' 3,095,939 7/1963 Hine l80/79.l 11 Claims, 7 Drawing Figures SHEEI10F4 PAIENTEUJULIOIQYS PAIENIEUJUL 1 0197s 3 5sum 2 or a Fig. 3 53 48 13 52a 48 35 36 37 38 39 40 41 L2 L3 L4 1.5

PAIENTEUJUUOIQYS sumuom AUTOMATICALLY STEERED SELF-PROPELLED VEHICLE CROSS-REFERENCE TO RELATED APPLICATION The apparatus of the present invention constitutes an improvement over and a further development of apparatus disclosed in the copending application Ser. No. 137,354 filed by Wolfram Miiller on Apr. 26, 1971 and owned by the assignee of the present case.

BACKGROUND OF THE INVENTION The present invention relates to an unmanned vehicle for treating the unobstructed part of an area having obstructions preventing continued movement of the vehicle.

Vehicles of this type are known which move along guiding conductors generating an alternating field. The actual path of the vehicle is determined by the guiding conductors, and the vehicle is incapable of recognizing obstructions which are ocated in the path of movement determined by a conductor, which was placed there after the operation of the vehicle was started. Since the guiding conductors are usually under the floor, a changing of the path is not easily possible. The arrangement of the prior art is unsuitable under conditions where loads are deposited at varying and different places, as may occur in storage areas and warehouses. It may occur, that a truck deposits its load on a conductor, so that the vehicle, moving along the guiding conductor, would ram the load.

An apparatus which solves the above-mentioned problems is disclosed and claimed in US. Pat. application Ser. No. 137,354 filed by Wolfram Mi'iller on Apr. 26, 1971 and assigned to the assignee of the present invention. The apparatus disclosed in this referenced application is not limited or dependent in the provision of guiding conductors which are usually placed under the ground. As described in that application, once that apparatus has selected a straight path to traverse, it proceeds essentially along said straight path. However, because of irregularities in the ground over which the vehicle passes, tolerances in the steering mechanism and- /or other such influences, it is possible that the vehicle deviate off its selected straight path.

SUMMARY OF THE INVENTION It is one object of the invention to provide an automatically steered self-propelled vehicle which does not have the disadvantages of the vehicles known in the prior art.

Another object of the invention is to provide an automatically steered self-propelled vehicle which will in a simple and effective way maintain the course of the vehicle in substantial parallelism with a reference surface.

Another object of the invention is to provide an automatically steered self-propelled vehicle which can maintain its course in substantial parallelism with a reference surface independently of the distance that said vehicle is from said reference surface.

According to the present invention, and with these objects in view, the present invention can be utilized with a wheeled vehicle having a frame and motor means on said frame for propeliing the vehicle at least in one direction. Steering means on the frame is provided for steering said vehicle so that the course of the vehicle is normally at least substantially parallel to a reference surface. At least one transmitter is provided for transmitting a signal in the direction of the reference surface and at least one receiver is provided for receiving the reflected signal from the reflecting surface when the vehicle deviates from its normal course. Regulating means are connected to the receiver and to the steering means for generating a control signal in response to said reflected signal for activating said steering means when said reflected signal is received by said receiver means to thereby alter the course of the vehicle and to cause the vehicle to resume its movement in substantial parallelism with said reference surface.

According to a presently preferred embodiment, the receiver includes a plurality of receiver sensors arranged in a determined order with respect to the transmitted signal. Each sensor is positioned to receive the reflected signal for different relative orientations of the vehicle with respect to the reference surface. The sensors are calibrated to generate output sensor signals which are a function of the degree by which said vehicle alters its course from its normal course. The output sensing signals generated by the sensors appear in quantized form and these are converted in a digital-toanalog converter which is connected to said sensors for converting said output sensing signals into an analog output signal. A variable gain amplifier is provided which has means for changing its gain. The amplifier is connected to the digital-to-analog converter and to the steering means for amplifying said analog output signai to yeild a control signal for appropriately activating, at a predetermined distance of said vehicle from said reference surface, said steering means. To make the control signals independent of the distance of the vehicle from the reference surface, the means for changing the gain includes a potentiometer having a movable portion, said analog output signal being applied across the potentiometer and said amplifier input being connected to said movable portion. Position changing means are provided for changing the position of the movable portion as a function of and proportional to the distance between the vehicle and the reference surface, whereby said control signal is substantially independent of the latter distance. In order to change the distance of the vehicle from the reference surface, the wheels of the vehicle are rotatable from the normal position. The position changing means comprise a servo motor operatively connected to the movable portion-to move its position when the servo motor is energized. An AND control switch has an output and two input points and generates an output at said output point only when appropriate signals are applied to both input points to energize said servo motor. One input point of said control switch is connected to the steering control means to sense the presence of the appropriate control signal. The other input point is connected to a control device connected to the wheels to sense when the wheels are rotated 90 from their normal position and the vehicle is changing its distance with respect to the reference surface. In this manner, the movable portion position and the gain of the amplifier is changed only in relation to changes in distance of said vehicle from said reference surface.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic plan view illustrating an area having obstructions, and a vehicle on the unobstructed portion of the area;

F IG. 2 is a schematic view illustrating an area having obstructions surrounded by conductors, and a vehicle on the unobstructed portion of the area;

FIG. 3 is a schematic plan view of an automatically steered self-propelled vehicle;

FIG. 4 is a diagram illustrating an electric circuit for the sensing means with which the vehicle of FIG. 3 is provided;

FIG. 5 is a diagram illustrating schematically the interconnection between elements of the control device of the vehicle;

FIG. 6 is a diagram schematically illustrating the control of the steering means of the vehicle; and

FIG. 7 is a schematic plan view of an automatically steered self-propelled vehicle incorporating the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, anarea 10 has obstructions'll and 12. A self-propelledvehicle 13, shown in greater detail in FIG. 3, may carry rotary-sweeping brushes for cleaning the unobstructed portion of thearea 10. Theobstructions 11 and 12 project above the surface of the area, and would obstruct the movement ofvehicle 13. Thearea 10 is surrounded by a suitable obstruction by whichvehicle 13 is prevented from moving out of and beyond the area.

Thevehicle 13 is placed at theregion 14 of the surrounding obstruction, and is driven by amotor 47driving wheels 48, to move along a substantiallystraight path 14a shown with broken lines and arrowheads, until reaching theregion 15 of the surrounding obstruction or boundary 22, which is recognized by front sensor means 16 ofvehicle 13. The front sensor means generate a reversing signal which causes reversing ofmotor 47 so that thevehicle 13 moves in a rearward direction along thepath 15a back to theregion 14 of the surrounding obstruction 22. Therear sensor 49 senses the position of the vehicle, and causes again reversing ofmotor 48, so that the vehicle is again driven to move in forward direction toward the other end of the area It). Thevehicle 13 includes acontrol device 46 in which the signals generated by the sensing means 16 and 49 are evaluated for initiating required operations. In theregion 14, the steering means of the vehicle are operated under the control of thecontrol device 46 to turn the wheels 48 a suitable angle, for example 90 or 45", to a new path starting atpoint 17. The distance between thefirst paths 14a and 15a and a new path may correspond to the width ofvehicle 13 so that theentire area 10 would be successively swept byvehicle 13, if no obstructions l1 and 12 were found inarea 10. The return ofwheels 48 to the normal position for forward and rearward movement, is effected by resilient means when thesteering motor 50 is de-energized. Thesteering motor 50 drives, when energized, aspindle 51 by which agear 52 is displaced for operating alinkage 52a by which thewheels 48 are angularly displaced, as shown in FIG. 3. Resilient means 94,95 connected withlinkage 91straighten wheels 48 out whensteering motor 50 is de-energized, see FIG. 6.

Vehicle 13 moves now along apath 17a until the sensing means 16 sense theobstruction 11, which causes reversal ofmotor 47 by thecontrol device 46 so thatvehicle 13 moves along thepath 17b in a rearward direction towardpoint 17 whererear sensor 49 recognizes theboundary 24, and causes reversal ofmotor 47. The steering means 50,5l,52,48 are again operated to steer the vehicle to anew path 18a on which the vehicle moves in forward direction toward theobstruction 11. Upon approaching theobstruction 11, the sensing means 16, which includes a row of sensors, recognizes that theobstruction 11 only partially projects into thenew path 18a. Since only a part of the row ofsensors 16 engage the obstruction, the row offront sensors 16 recognizes howfar obstruction 11 projects into thenew path 18a. The motor of thevehicle 47 is reversed, the vehicle moves back in reverse direction along thepath 18b, and is automatically steered, in accordance with the information derived from the row ofsensors 16, a smaller transversedistance to thenew path 19a where the vehicle moves forward to thepoint 19 just bypassing the lateral surface ofobstructionn 11. Alateral sensor 20 having a projectingactuator 53, as shown in FIG. 3, preferably constructed as a microswitch, engages the lateral surface of theobstruction 11 and is closed, but whenvehicle 13 has passed theobstruction 11, thesensor switch 20,53 is again released by the lateral surface ofobstruction 11 and theactuator 53 moves again transversely to openswitch 20. In this manner, information is transmitted to thecontrol device 46 that theobstruction 11 has been passed, and thecontrol device 46 energizes thesteering motor 50 to steer thevehicle 13 to a new path located. between the obstruction l1 and the surrounding obstruction 22, and the steering means is controlled to straighten out thewheels 48 at thepoint 21 so that the vehicle moves in the initial forward direction, until themotor 47 is reversed at the boundary obstruction, andvehicle 13 moves back until the rear sensor, also amicroswitch 49, again senses theobstruction 11 during rearward movement ofvehicle 13.

As described above, motor'47 is again reversed and the steering means operated so thatvehicle 13 moves alongpath 23a to thepoint 23 wheremotor 47 is reversed so that the vehicle moves rearward alongpath 23b until therear sensor 49 senses theobstruction 11, and causes steering ofvehicle 13 back topoint 21, rearward towardobstruction 11, where the vehicle is steered again to move onto the track where it moves forwardly until reversed by the boundary obstruction 22 and moves along thepath 19b to the other end of thearea 10, where the movements of thevehicle 13 are-controlled as described above, and as shown in broken lines provided with arrowheads in FIG. I. Whenvehicle 13 approaches thelateral boundary obstruction 22a, anend sensor 77 senses theobstruction 22a, and causes de-energization ofmotor 47 so that the vehicle stops, when the front sensor means 16 engages the other end of the boundary obstruction.

The embodiment of FIG. 1 operates due to mechanical operation of sensor switches. However, if the obstructions are recesses in the surface of the area, as shown at 26,27, and 28, in FIG. 2,wire loops 29 and 30 are placed on the surface of the area around theobstructions 26,27,28, and are connected to alternatingcurrent generators 31 and 32, as shown in FIG. 2. The correspondingloop 33 of a conductor may form the boundary obstruction around thearea 25, and is supplied by alternatingcurrent generator 34 with a required current, so that the currents flowing in the wire loops create alternating fields. The vehicle 13' is provided withfront sensors 78,lateral sensor 79, stopsensor 81, andrear sensor 80, each of which includes a coil responsive to the alternating fields and controlling the reversing and steering operations of vehicle 13'. The pattern according to which thearea 25 is swept by the vehicle 13', is the same as described with reference to FIG. ll.

Referring now particularly to FIG. 3, the forward end a of the supportingframe 35ofvehicle 13, carriedmicroswitches 36 to 45 arranged in a horizontal row, which either in the actuated condition, or in the normal position, generate a signal for thecontrol device 46, which includes astorage device 76, as shown in the schematic diagram of FIG. 5. Thestorage device 76 may consist of bistable multivibrators which store the width of the portion of thevehicle 13 which is stopped by an obstruction. Eachmicroswitch 36 to 45 is correlated with a certain information which is introduced into thecontrol device 46 and thestorage device 76, so that the width of an obstruction can also be determined by the sensing means 36 to 45 when the obstruction is narrow, so that only onemicroswitch 41, for example, engages the obstruction, while the other microswitches 36-40 and 4245 are free. In accordance with the signals from the sensing means, which indicate that an obstruction or obstacle is located in the path of movement of thevehicle 13, theelectromotor 47, which is the drive motor of thevehicle 13, is reversed. As explained above, thewheels 48 are then driven in a reverse direction of rotation, and the movement of thevehicle 13 takes place opposite to the intial forward direction. This rearward movement is maintained until themicroswitch 49 at the rear end offrame 35 senses an obstruction, and generates a signal which indicates that thevehicle 13 has arrived at the start of the respective path of movement. In accordance with the width of the obstacle determined by thefront sensor microswitches 36 to 45,vehicle 13 is moved laterally the distance determined by themicroswitches 36 to 45.

If the sensed obstruction is wider than thevehicle 13, which is the case when thefront sensor microswitches 36 to 45 engage the boundary obstruction 22 at the end of a forward movement, thecontrol device 46 controls the steering means to move the vehicle in transverse direction its entire width.

When thelateral sensor 53 senses the end of a passedobstruction 11, it generates a signal to thecontrol device 46, which causes a transverse steering of thevehicle 13 for its entire width in the same transverse direction in whichsensor 53 projects, so that the vehicle can move between the front face ofobstruction 11 and the boundary obstruction 22 so that no part of the surface area is skipped.

FIG. 4 illustrates an electric circuit for thesensor microswitches 36 to 45. Eachmicroswitch 35 to 45 has ashiftable contact 54 to 63. Shiftable contacts of sensor switches, which are not actuated by an obstruction, are connected in series as shown for theshiftable contacts 61,62,63 of the sensor switches 43,44,45. Theseriesconnected contacts 61,62,63 are connected to the positive terminal of acapacitor 74, which is also connected to the base of aninput transistor 73 of thecontrol device 46. The microswitches, which engage an obstruction, for example themicroswitches 37 to 42 in FIG. 4,

V displace the respectiveshiftable contacts 54 to 60 to positions connected with theresistors 64 to 72, respectively, which have different resistances, which differ by the same amount. One free contact ofmicroswitch 45, which is open, is connected to the interconnected ends ofresistors 64 to 72, and to the negative terminal ofcapacitor 74. Consequently, the input electrode of theinput transistor 73 receives an input signal corresponding to the charge ofcapacitor 74, and representing the width of the sensedobstruction 11.

Referring now to the schematic diagram of FIG. 5, the steering means, represented byrefercncenumeral 50, are connected with thestorage device 76 by an ANDgate 75 which permits passage of a signal only when an output signal is generated byrear sensor switch 49 together with a signal from storage means 76 for causing operation of the steering means 50. Thestorage device 76, which may consist of multivibrators respectively correlated with thefront microswitches 37, 35 is constructed so that the multivibrators switch to one or the other position depending on the condition of themicroswitches 36 to 45, and remain in the shifted condition until thevehicle 13 has been steered into the next path.Storage device 76 is connected with the front sensing means 16 for recognizing the obstructions, which include theelectromechanical microswitches 36 to 45.

In accordance with the determined value corresponding to the width of theobstruction 11 or 12, drivemotor 47 is reversed so that the vehicle moves in the opposite direction untilrear sensor switch 53 generates a signal .which causes again reversal ofdrive motor 47 without energization of the same, as will be explained hereinafter. First, thesteering motor 50 is operated so that when drivemotor 47 is again energized, thevehicle 13 is steered laterally to the next following path. After the lateral displacement ofvehicle 13, thewheels 46 are automatically straightened so thatvehicle 13 drives in a substantially forward direction until sensing another obstruction in its path, or'until arriving at the boundary obstruction 22.

By passing of anobstruction 11 or 12, thelateral sensor 53 generates a signal which influences thesteering motor 50 to cause movement of the vehicle in the lat eral direction into the omitted part of the area. Theend switch 77 on the other side of thevehicle 13 is actuated when engaging thelateral portion 22a of the boundary obstruction, and disconnects drivemotor 47 from the voltage source.

Thestorage 76 may be constituted by a capacitor, but it is also possible to provide a counting storage, as shown in FIG. 6. Such astorage 76 counts the actuated front sensor switches 36 to 45, and the counted number of operated front sensing switches in stored, until no longer required. Storage means of this type are well known to those skilled in the art.

Referring now to FIG. 6, threemicroswitches 36,37,38 are shown, respectively connected withresistors 64,65,66,as also shown in FIG. 4.Microswitches 36 to 45 can be connected byresistors 64 to 72 withstorage device 76 of thecontrol device 46.

Switches 36 to 38, for example, are connected by aOR gate 83 with the winding 84 of a relay.Relay 84 operates a reversingswitch 85 which is also operable by therear sensor 49. Reversingswitch 85 is connected withdrive motor 47 for reversing the same, so that themotor 47 is reversed when front sensor switches 36,37,38 simultaneously abut the obstruction during forward movement, or whenrear sensor 49 abuts the boundary obstruction during rearward movement of thevehicle 13. Thestop switch 77 is connected into the circuit of drive motor 4-7, so that the same is disconnected from the voltage source when thelateral boundary obstruction 22a is sensed by thesensor 77.

The storage means 76 is connected with the first input of an ANDgate 75 whose second input is connected with a contact of the reversingswitch 35. The output of the ANDgate 75 is connected with thesteering motor 50. Storage means 76 is also connected with the first input of an ANDgate 38 at whose second input a voltage is applied, and whose third input receives a signal from thelateral sensor switch 53. Adifferential element 96 connectslateral sensor switch 53 with the ANDgate 88, and has the effect that only when a signal is generated by thelateral sensor switch 53, a pulse opens the ANDgate 88. The output of the ANDgate 88 is connected with thesteering motor 50 which, as explained above, operates aworm spindle 85 and a gear segment 90 for displacing asteering link 91 by which thewheels 48 of thevehicle 13 can be angularly displaced. The two springs 94 and 95 are acting on link- 1age 91 to turnwheels 48 to a straight position whenmotor 50 does not operate.

When thevehicle 13 senses an obstruction during forward movement, at least one of the front switches 36 to is actuated, so that a pulse reaches the winding 84 of the relay of the reversingswitch 83 to theOR gate 83 so thatdrive motor 47 is reversed, causing thevehicle 13 to move along the same path as before in the reverse opposite direction. The width of the obstruction is determined in the storage means 76 by the number and position of the actuated front sensor switches 36 to 45. Whenvehicle 13 has arrived in its initial position, therear sensor 49 is operated by the boundary obstruction, so that the reversingswitch 85 is shifted and thedrive motor 47 is set to forward movement. At the moment in which therear sensor 49 responds, and reversingswitch 85 is shifted, the voltage source ofmotor 47 is connected with the ANDgate 75 so that steering motor 51) is energized during a certain time in accordance with the electric charge stored in storage means 76, for example in a capacitor, the charge representing the width of the obstruction in the path of movement of thevehicle 13. The time during which steering motor 511 is energized and turnwheels 48, is so determined that the wheels are turned 90, and the vehicle moves in a direction transverse to its previous direction of movement until, in accordance with the amount of electricity stored in storage means 76, the ANDgate 75 closes again so that steering motor is reset, and springs 941,95turn wheels 48 back to the initial straight position.

During the following movement ofvehicle 13, thelateral sensor switch 53 is depressed, and nothing happens because the differential element 97 blocks the generated signal. Whenvehicle 13 has passed the obstruction, the actuator of thelateral sensor switch 53 is urged by a spring to move outward again so that a pulse is transmitted through thedifferential element 96 to the AND gate 89 and opens the same so that steeringmotor 50 is then connected with the voltage, but in a different polarity, as compared with the operation whenrear sensor 49 sensed the rear portion of boundary obstructiOn 22. Consequently,wheels 48 are again turned but in the opposite direction, so that thevehicle 13 moves laterally, as viewed in FIG. 1 from thepoint 19 to thepoint 21 of its path. After thevehicle 13 has moved transversely a distance corresponding to the width of theobstruction 11, the ANDgate 88 closes, and steeringmotor 50 is no longer operated, so that springs 94 and 95turn wheels 43 back to a straight position for forward and rearward movement. At the same time when steeringmotor 50 is disconnected, a signal may be transmitted to storage means 76 which causes clearing of storage means 76 since the signal stored in the same is no longer required.

Paths 14a, 15a, 17a and so on have been shown in FIG. 1 to be straight paths. As has been described, referring to FIG. 6, springs 94,95 are provided which act onlinkage 91 to turn thewheels 38 to a straight position whenmotor 50 does not operate. This, at least to a first approximation, steersvehicle 13 in the substantially straight paths shown in FIG. 1. However, as a practical matter, unevenness of the ground over whichvehicle 13 traverses, tolerances in the steering linkages and wheels of the vehicle and other prevailing influences sometimes have the tendency to causevehicle 13 to move off of its predetermined straight course despite the action ofresilient means 94,95.

Accordingly, the present invention is shown embodied onvehicle 13, where some of the details shown in FIG. 3 have been deleted for clarity. It should be noted, however, that the components shown in FIG. 3 are not necessarily replaced by the apparatus to be described in relation to FIG. 7. This latter apparatus merely serves to assist or enhance the operation of thevehicle 13 in substantial parallelism to a reference surface as will hereinafter be described. Referring to FIG. 7, thereference surface 3 is shown from whichvehicle 13 is spaced a predetermined amount, leaving aspace 2 therebetween. Onvehicle 13 is mounted transmitter means 164 and receiver means comprising of sensors through 109. Thetransmitter 104 transmits a signal 4 in the direction of thereference surface 3, the signal reflected 5 being received by one of the sensors 194 through 169. The type of signal transmitted by transmitter 104i is not critical for the purposes of the present invention, any suitable signal commonly used for such purposes being equally suitable. The only requirement, is that thereference surface 3 be at least partially reflecting of the type of signal which is transmitted by 104 so as to give rise to a reflectedsignal 5. Thus, transmittedsignal 41 can consist of electromagnetic radiation, such as a light beam. In such an instance,transmitter 104 would consist of a light source and sensors 1043 through 109 would consist of photodetecting devices. Another possibility is that transmitted signal 4 be an acoustic signal, in which case transmitter 164 can be in the form of a loudspeaker whilesensors 10 1 through 109 can be selected to be a plurality of microphones.

As shown in FIG. '7, thetransmitter 104 and thereceiver sensors 105 through 109 are mounted on a rotatable deck 1 10. By such mounting, it is possible to rotate the direction of transmission of thetransmitter 104 and the receiver sensors 165 through 109 in such a way as to utilize anysurface surrounding vehicle 13 as a reference surface. As described above,space 2 can contain obstacles and as such, where appropriate, the elevation of thetransmitter 104 and thesensors 105 through 109, should be such that these obstacles would not interfere or obstruct the transmitted signal 1 or the reflectedsignal 5.

Thesensors 105 through 109 are arranged in a predetermined order with respect to the transmitted signal, each sensor being positioned to receive the reflected signal for a different relative orientation of the vehicle with respect to the reference surface. Normally, when thevehicle 13 is progressing along one of the straight paths depicted in F 1G. 1 and substantially parallel to a reference surface such as surface 22, the transmitted signal 4 is transmitted perpendicularly to the reference surface 4 and, therefore, the angle of incidence is zero. Since the angle of incidence is zero, the reflected signal returns along the same path as the transmitted signal traversed, and the reflected signal is detected by a neutral sensor, such assensor 107. The effect of this will hereinafter be described. Now, should thevehicle 13 deviate off its course of substantial parallelism with thesurface 3, then,transmitter 104 being fixed to the frame of thevehicle 13, the transmitted signal 4 will now impinge on thereference surface 3 at a predetermined incidence angle. Accordingly, the reflectedsignal 5 will no longer impinge onsensor 107 but on another sensor, such assensor 105, as shown in FIG. 7. The more thevehicle 13 deviates off its course of substantial parallelism with thesurface 3, the greater is the angle of incidence and said beam accordingly impinges on sensors further fromsensor 107. If the deviation of thevehicle 13 is in opposite direction, then the reflectedsignal 5 will impinge on a sensor on the other side ofneutral sensor 107, such asensor 108 or 109. Thesensors 105 through 109 are calibrated to generate output sensing signals which are a function of the relative position of the individual sensors in relation tosensor 107. Thus, according to one arrangement, the output sensing signals ofsensors 105 through 109 could increase in ascending order. However, the specific nature of the output sensing signals is not critical as long as they contain the information regarding the deviation of the vehicle.

Since thesensor 105 through 109 are shown to be individual sensors, each sensor will, in response to impingement of the reflectedsignal 5 on said sensor, generate a discrete output sensing signal. Stated another way, the outputs ofsensors 105 through 109 are quantized in amplitude, phase, or some other variable. According to the embodiment presently shown in FIG. 7, the output sensing signals are quantized in amplitude and the quantized output sensing signals are fed to a digital-to-analog converter 100 for converting the output signals from a quantized signal to an analog signal. The analog output signal from digital-to-analog converter 100 is placed acrosspotentiometer 111. Thepotentiometer 111 has a movable portion or a slidable contact which is mechanically connected to servomotor 11.3. The sliding contact of thepotentiometer 111 is electrically connected to the input of avariable gain amplifier 112, whose output is connected to thesteering motor 50.

When thevehicle 13 is travelling at a predetermined distance from thereference surface 3, thetransmitter 104 is intermittently or continuously transmitting the signal 4 at thereference surface 3. As long as thevehicle 13 progresses in substantial parallelism with thereference surface 3, the reflectedsignal 5 impinges on thesensor 107. The output sensing signal of thesensor 107 and the digital-to-analog converter are so adjusted that when the reflectedsignal 5 impinges on theneutral sensor 107, no control signal is supplied at the output ofamplifier 112 which energizes steering motor means 50 to modify the course ofvehicle 13. However, should thevehicle 13 now deviate from its course of substantial parallelism with thesurface 3, the reflected signal will now impinge on a sensor other than theneutral sensor 107. Assuming that the reflected signal impinges on thesensor 106, a control signal will be generated at the output of theamplifier 112 to correct the course of thevehicle 13. The amplitude of the control signal is a function of the angle of incidence of the reflected signal, and therefore upon which sensor the reflected signal impinges on. For example, should the reflectedsignal 5 impinge on the sensor instead of thesensor 106, then the control signal which energizes thesteering motor 50 would be correspondingly greater, since the course of thevehicle 13 must be modified to a greater extent in order to maintain its normally defined course.

The calibration of thesensors 104 through 109 results in a set of control signals which are most appropriate for a predetermined distance between thevehicle 13 and thereference surface 3. It is clear from the geometry that even for equal angles of incidence of the transmitted and reflected signals, the reflectedsignal 5 may impinge on a sensor closer or further from theneutral sensor 107 depending on the distance of thevehicle 13 from thereference surface 3. In order to maintain the control signals only a function of the angle of incidence of the reflectedsignal 5 and not a function of the absolute distance of thevehicle 13 from thereference surface 3, means are provided for adjusting the gain of theamplifier 112 as a function of the distance of thevehicle 13 from thereference surface 3, so as to compensate for the above-described fact. Thus, an AND control device, here shown as an ANDgate 120, is shown to have one output and two input points. The output point of AND gate is connected to the servomotor 1 13 for energizing the same under specified conditions. One input point of the ANDgate 120 is connected to the output ofamplifier 112 to sense the presence of a control signal. The other input point of the ANDgate 120 is connected to the junction point between themotor 17 and thecontrol device 46. With this arrangement, the output of ANDgate 120 will energizeservomotor 113 only when both the wheels of the vehicle have turned 90 to their normal direction and they are in fact turning. This condition signifies that thevehicle 13 is moving in a direction perpendicular to thereference surface 3 in a way as to modify the distance between thereference surface 3 and thevehicle 13. For the duration of time that the wheels of thevehicle 13 are 90 from their normal position and these wheels are turning, the output of ANDgate 120 energizes theservomotor 113 which is operatively connected to the movable portion or sliding contact of thepotentiometer 111. Thus, by ensuring that thevehicle 13 moves towards or away from thereference surface 3 at a constant velocity, and by ensuring that theservomotor 113 moves the sliding contact at a correspondingly constant velocity, the position of a sliding contact, and, there fore, the effective gain ofamplifier 112 can be proportionally changed. Now, the impingement of the re flected signal on one of thesensors 105 through 109,

llil

may not produce a control signal as large or as significant as they did at another prior distance. Although the output sensing signals of thesensors 105 through we in response to impingement thereon of the reflected signal remains substantially constant, a greater or lesser portion of the converted analog output signal is fed to the amplifier 1112. In a sense, the gain adjusting means above described is not unlike a weighing factor which weighs the output sensing signals from the respective sensors to take into account the distance of thevehicle 13 from thereference surface 3. By using such an arrangement, the control signals which energize the steering motor to modify slight deviations of the vehicle off its course of substantial parallelism, is substantially independent of the distance of thevehicle 13 from thereference surface 3 and almost entirely dependent on the degree of deviation from the desired course.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of vehicles for automatically following an obstructed surface differing from the types described above.

While the invention has been described as embodied in an automatically steered self-propelled vehicle following its direction of movement automatically in substantial parallelism with a reference surface, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

I claim:

1. An apparatus for maintaining a substantially fixed relative orientation between at least one partially reflecting reference surface and a steered self-propelled vehicle, particularly a vehicle for movement over the unobstructed portion of an area having obstructions, comprising a vehicle frame; motor means on said frame for propelling said vehicle at least in one direction; steering means on said frame for steering said vehicle so that the course of the vehicle is normally at least substantially parallel to said reference surface; at least one transmitter means for transmitting a signal in the direction of said reference surface; at least one receiver means for receiving the reflected signal from said refleeting surface when said vehicle deviates from said course; and regulating means connected to said receiver means and to said steering means for generating a control signal in response to said reflected signal for activating said steering means when said reflected signal is received by said receiver means to alter the course of the vehicle and cause the vehicle to resume its movement in substantial parallelism with said reference surface, wherein said receiver means includes a plurality of receiver sensors arranged in a predetermined order with respect to the transmitted signal, each sensor of said receiver means being positioned to receive said reflected signal for different relative orientations of said vehicle with respect to said reference surface and being calibrated to generate output sensing signals which are a function of the degree by which said vehicle deviates from its normal course.

2. An apparatus as defined in claim 1, further comprising sensing means on said frame for generating a signal when sensing an obstruction during movement in said direction; and a control device including steering control means responsive to said latter signal of said sensing means to operate said steering means to change the direction of movement of said vehicle so that said vehicle continues to move on said unobstructed portion of said area.

3. An apparatus as defined inclaim 11, further including rotatable means for supporting said transmitter and receiver means and for rotating said transmitter and receiver means in equal amounts in relation to said vehi cle frame, whereby any surface surrounding said vehicle can be chosen to be said reference surface.

4. An apparatus as defined in claim 1, wherein two transmitter means and two corresponding receiver means are arranged on said frame, each transmitter means transmitting a signal towards a corresponding reference surface.

5. An apparatus as defined in claim 1, wherein said transmitter and receiver means comprise a light source and photo-electric means respectively, and said transmitter and reflected signals comprise light beams.

6. An apparatus as defined in claim 1, wherein said transmitter and receiver means comprise acoustic transmitter and acoustic receiver means respectively, and said transmitted and reflected signals comprise acoustic signals.

7. An apparatus as defined in claim 1, wherein said output sensing signals generated by said sensors appear in quantized form, and wherein said regulating means includes a digital-to-analog converter which is connected to said sensors for converting said output sensing signals into an analog output signal.

8. An apparatus as defined in claim 7, wherein said regulating means includes a variable gain amplifier, having means for changing its gain, which is connected to said digital-to-analog converter and to said steering means for amplifying said analog output signal to yield said control signal for appropriately activating, at a predetermined distance of said vehicle from said reference surface, said steering means.

Q. An apparatus as defined in claim 8, wherein said means for changing the gain includes a potentiometer having a movable portion, said analog output signal being applied across the potentiometer and said amplifier input being connected to said movable portion.

10. An apparatus as defined in claim 9, further comprising position changing means for changing the position of said movable portion as a function of and proportional to the distance between said vehicle and said reference surface, whereby said control signal is substantially independent of the latter distance.

ll 1. An apparatus as defined inclaim 10, wherein said wheels of said vehicle are rotatable from their normal position in response to an appropriate control signal to thereby enable the vehicle to move in a direction perpendicular to said reference surface to thereby change its distance relative to said surface, and wherein said position changing means comprises a servomotor operatively connected to said movable portion to move a control device and said motor means to sense when the wheels are energized to thereby detect when the vehicle is changing its distance with respect to said reference surface, whereby said movable portion position and the gain of the amplifier is changed only in relation to changes in distance of said vehicle from said reference surface.

Claims (11)

1. An apparatus for maintaining a substantially fixed relative orientation between at least one partially reflecting reference surface and a steered self-propelled vehicle, particularly a vehicle for movement over the unobstructed portion of an area having obstructions, comprising a vehicle frame; motor means on said frame for propelling said vehicle at least in one direction; steering means on said frame for steering said vehicle so that the course of the vehicle is normally at least substantially parallel to said reference surface; at least one transmitter means for transmitting a signal in the direction of said reference surface; at least one receiver means for receiving the reflected signal from said reflecting surface when said vehicle deviates from said course; and regulating means connected to said receiver means and to said steering means for generating a control signal in response to said reflected signal for activating said steering means when said reflected signal is received by said receiver means to alter the course of the vehicle and cause the vehicle to resume its movement in substantial parallelism with said reference surface, wherein said receiver means includes a plurality of receiver sensors arranged in a predetermined order with respect to the transmitted signal, each sensor of said receiver means bEing positioned to receive said reflected signal for different relative orientations of said vehicle with respect to said reference surface and being calibrated to generate output sensing signals which are a function of the degree by which said vehicle deviates from its normal course.

2. An apparatus as defined in claim 1, further comprising sensing means on said frame for generating a signal when sensing an obstruction during movement in said direction; and a control device including steering control means responsive to said latter signal of said sensing means to operate said steering means to change the direction of movement of said vehicle so that said vehicle continues to move on said unobstructed portion of said area.

3. An apparatus as defined in claim 1, further including rotatable means for supporting said transmitter and receiver means and for rotating said transmitter and receiver means in equal amounts in relation to said vehicle frame, whereby any surface surrounding said vehicle can be chosen to be said reference surface.

4. An apparatus as defined in claim 1, wherein two transmitter means and two corresponding receiver means are arranged on said frame, each transmitter means transmitting a signal towards a corresponding reference surface.

5. An apparatus as defined in claim 1, wherein said transmitter and receiver means comprise a light source and photo-electric means respectively, and said transmitter and reflected signals comprise light beams.

6. An apparatus as defined in claim 1, wherein said transmitter and receiver means comprise acoustic transmitter and acoustic receiver means respectively, and said transmitted and reflected signals comprise acoustic signals.

7. An apparatus as defined in claim 1, wherein said output sensing signals generated by said sensors appear in quantized form, and wherein said regulating means includes a digital-to-analog converter which is connected to said sensors for converting said output sensing signals into an analog output signal.

8. An apparatus as defined in claim 7, wherein said regulating means includes a variable gain amplifier, having means for changing its gain, which is connected to said digital-to-analog converter and to said steering means for amplifying said analog output signal to yield said control signal for appropriately activating, at a predetermined distance of said vehicle from said reference surface, said steering means.

9. An apparatus as defined in claim 8, wherein said means for changing the gain includes a potentiometer having a movable portion, said analog output signal being applied across the potentiometer and said amplifier input being connected to said movable portion.

10. An apparatus as defined in claim 9, further comprising position changing means for changing the position of said movable portion as a function of and proportional to the distance between said vehicle and said reference surface, whereby said control signal is substantially independent of the latter distance.

11. An apparatus as defined in claim 10, wherein said wheels of said vehicle are rotatable 90* from their normal position in response to an appropriate control signal to thereby enable the vehicle to move in a direction perpendicular to said reference surface to thereby change its distance relative to said surface, and wherein said position changing means comprises a servomotor operatively connected to said movable portion to move its position when said servomotor is energized; an AND control switch having an output and two input points and which generates an output at said output point only when appropriate signals are applied to both input points to energize said servomotor, one input point of said control switch being connected to said steering control means to sense the presence of said appropriate control signal, the other input point being connected to a control device and said motor means to sense when the wheels are energized to thereby detect when the vEhicle is changing its distance with respect to said reference surface, whereby said movable portion position and the gain of the amplifier is changed only in relation to changes in distance of said vehicle from said reference surface.

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