GB2186398A

GB2186398A - Automatically controlled wagon

Info

Publication number: GB2186398A
Application number: GB08630348A
Authority: GB
Inventors: Masao Yoshikawa; Sotoshi Saito; Yoshiaki Takatsuki
Original assignee: Yoshida Kogyo KK
Current assignee: YKK Corp
Priority date: 1985-12-20
Filing date: 1986-12-19
Publication date: 1987-08-12
Also published as: AU6649286A; FR2593941A1; DE3643631A1; JPS62105508U; GB8630348D0

Abstract

An automatically controlled wagon, e.g. for a warehouse, comprises a camera (17) including a linear CCD or MOS image sensor (16) mounted such as to detect a guide zone (18) such as a reflective white tape provided on the ground surface (G), a circuit for detecting the lateral deviation of the wagon from the guide zone (18), and means for controlling the steering of the wagon according to the detected deviation. The wagon may be steered by differentially driving drive motors (8a, 8b) for a pair of independent drive wheels (4a, 4b), or by steering wheels. Configurations of the guide zone (18) designed to decelerate, stop or control the wagon at a junction are described. <IMAGE>

Description

SPECIFICATION Apparatus and method for controlling automatically controlled wagon Backgroundofthe invention 1. Fieldoftheinvention This invention relates to an apparatus and a method for controlling an automatically controlled wagon for running along a guide installed on the ground surface of the premises of a factory, a warehouse, etc.

2. Description ofthepriorart The operations oftransporting materials or products from a point of reception to a point of start of a production line orfrom a point of end of production line to a point of delivery in a mass production plant orthe like orsupplyofcargoto and from awarehouseortransportofcargo inthe warehouse, were heretofore performed using hoists, running cranes,vehicleswith forks or manually driven wagons.

With the recent industrial progress, however, it is becoming increasingly difficultto secure sufficient manual labor, and there has been a demand for means for automatically transporting cargo from a particular place to another. In the prior art, there is an automatically controlled wagon, which is controlled for running by an optical guidance system. In this system, a line having a different light reflectivity from that of the ground surface is drawn on the ground surface or a tape having a different light reflectivity is applied to the ground surface. The wagon is guided for running through detection ofthe difference in the light reflectivity with respectto light form a light source between the guide zone and ground surface.

In such optical guidance system, however, once the wagon gets out ofthe guide zone so thata photodiode or phototransistor no longer detects light reflected by the guide zone, it is impossibleto determinewhetherthe running wagon is on the right or left side of the guide zone. When this occurs, there is no destination,to which the vehicle is controlled.

The vehicle thus cannot return to the guide zone, so that a grave accident is liable.

A solution to such a problem in the optical guidance system is disclosed in Japanese Patent Publication 55-12,605. More specifically, there is disclosed a control apparatus, in which a plurality of photoelectric elements (i.e., light-receiving elements) are disposed in a row on the bottom of a wagon. These light-receiving elements receive light reflected from a guide zone provided on the ground surface, andtheiroutput "on" or "off" signals are passed through a logic circuitry including OR,AND and NOT circuits to obtain leftturn, rightturn,stop and other control signals. According to these control signals, the steering angle is controlled to reduce the deviation ofthewagon from the guidezoneto be zero.

This control system, however, requires a plurality of light-receiving elements arranged in a row. In addition, an amplifier should be provided for each of the light-receiving elements. Further, the plurality of light-receiving elements are positioned with respect to the wag on deckwhen mounting them, so thatthe mounting operation is very cumbersome.

Furthermore, by increasing the number of light-receiving elements the number of amplifiers is correspondingly increased to increase the cost.

Summary ofthe invention According to a first aspect ofthe invention, there is provided an apparatusforcontrolling an automatically controlled wagon for running along a guide zone provided on the ground surface, comprising: a camera including a linear image sensor mounted on a deck such as to be able to detect a guide zone provided on the ground surface, a position detection circuit for calculating the deviation of the wagon from said guide zone through analysis of a detected signal from said image sensor; and meansforcontrollingthe runningofthewagon according to the calculation data from said position detection circuit.

According to a second aspect of the invention, there is also provided a method of controlling an automatically controlled wagon by detecting the deviation from the center of said guide zone provided on the ground surface ofthe center of a camera provided on said deck such as to face said guide zone and including a linearimagesensor,the deviation detection being done from an output signal from the linear image sensor, and steering said wagon according to the detected deviation.

For the control of runing ofthe automatically controlled wagon, a pulse signal provided from a speed setting circuit according to calculation data from a position detection circuit is fed to a servo amplifier connected to each of drive motors for a pair of independent drive wheels mounted on the wagon deck, so that the revolving rates of the motors are controlled according to said pulse signal through said servo amplifiers.

It is believed possible by means of the present invention to provide an apparatus and a method for controlling an automatically controlled wagon, which can reliably control the direction of running of the wagon according to detected deviation ofthe wagon from a guide zone.

It isfurther believed possible by means of the present invention to provide an apparatus and a method for controlling an automatically controlled wagon, which can control the leftturn, rightturn, stop, speed change, etc. ofthewagon according to a pattern ofguidezone.

It is still further believed possible by means ofthe present invention to provide an apparatus for controlling an automatically controlled wagon, which can be easily mounted on a wagon deck and is economical and inexpensive.

It is still further believed possible by means ofthe present invention to provide an apparatus for controlling an automatically controlled wagon, which can control the wagon such thatthe wagon will nottrespass a guide zone and hence causes neither contamination nor damageto the guide zone and that the wagon can readily enter a narrow passage and can be readilyturned.

The invention will be described by way of example with reference to the accompanying drawings, wherein like references refer to like parts unless the context requires otherwise.

Briefdescription ofthe drawings Figure lisa side view, partly broken away, showing an automatically controlled wagon provided with the control apparatus according to the invention; Figure2is a bottom view showing the automatically controlled wagon shown in Figure 1; Figure3 is a fragmentary plan view showing a guide zone provided on the ground surface; Figure4isaviewshowing a portion oftheguide zone received in a camera field; Figure 5is a block diagram showing the circuitry of the apparatus for controlling the automatically controlled wagon; Figure 6 is a view showing an example of waveform of a COD image sensor output signal; Figure 7(A) and 7(B) are views showing a curved portion of a guide zone received in a camera field at different instances;; Figure 8 is a fragmentary plan view showing a different guide zone; Figure 9 is a view showing a portion of the guide zone shown in Figure 8 received in a camera field; Figure 10 is a fragmentary plan view showing a guide zone having a disconnection portion; Figure 11 is a view showing the disconnection portion ofthe guide zone shown in Figure 10 received in a camera field; Figure 12 is a fragmentary plan view showing a furtherguidezone; and Figure 13 is a view showing a portion of the guide zone shown in Figure 12 received in a camera field.

Detailed description ofthe preferred embodiments Now, a preferred embodiment ofthe invention will be described with reference to the accompanying drawings.

Figures 1 and 2 illustrate an automatically controlled wagon which has excellent manoeuverability and revolving property. A pair of front driven casters 2a and 2b are mounted symmetrically at opposite front corners of the bottom surface of a deck 1. These driven casters are capable of revolution so thatthey can run in all directions. A pair of brackets 5a and 5b are mounted on opposite sides of the bottom surface ofthe deck 1 at positions slightly on the rear side of the center.

Shafts 6a and 6b are mounted in the brackets 5a and 5b such that they extend in the perpendicular direction to the running direction (i.e., in the leftward direction in the Figure). A pair of support members 7a and 7b are pivotably mounted on the respective shafts 6a and 6b. Thesupport members 7a and 7b each consistofa pairofV-shaped elbow-like plate members. Rear driven casters 3a and 3b and drive wheels 4a and 4b are mounted between the support members ofthe respective pairs. The support members, while they are elbow-like in this embodiment, may be straight as well. The drive wheels 4a and 4b are rear driven casters 3a and 3b are provided on front and rear ends, respectively, of the support members 7a and 7b.The rear driven casters 3a and 3b, like the front driven casters 2a and 2b, are capable of revolution for running in all directions. The two shafts 6a and 6b may be replaced with a single shaft to support the support members 7a and 7b. Further, it is possible to provide the support members 7a and 7b such thattheysupport the drive wheels and front driven casters.

Motors 8a and 8b are secured to the lower surface of substantially central portions of the support members 7a and 7b. These motors have their output shafts 9a and 9b coupled tothe drive wheels 4a and 4b via pulleys 1 Oa and 1 Ob secured to theshafts 9a and 9b, belts 11a and 11band pulleys 13a and 13b secured to the axles 1 2a and 1 2b of the drive wheels 4a and 4b. The drivewheels 4a and 4b arethusdriven independently. The belts as the power transmission mechanism may be replaced with any other well-known means, e.g., chains.

The deck 1 has a peep hole 14formed in a front central portion. A control console 15 is provided atop the front central portion noted above of the deck 1 such asto cover the peep hole 14, and it accommodates a control unit for controlling the drive system. A camera 17 including a linear image sensor, e.g., a COD image sensor 16, is provided in the control console 15 such that it can photograph a guidezone 18 provided onthe ground surface G through the peep hole 14. As the linear image sensor noted above may be used a COD (charge coupled device) image sensor or a MOS (metal oxide semi-conductor) image sensor or any other kind of linear image sensor so long as it can discriminate brightness and darkness.

Figure3 shows an example ofthe guide zone 18. It comprises a wide black tape 19 and a narrowwhite tape 20 applied to a central portion of the blacktape 19 in the width direction thereof. It is provided continuously along a predetermined running path on the ground surface G. The above guide zone consisting of tape may be replaced with one consisting of a metal strip having high reflectivity.

The blacktape 19 and white tape 20 in this embodiment appears in the field A of the camera 17, as shown in Figure 4. The range of field ofthe camera is determined by the lenses used therein, and it can be increased by using wide angle lenses. The COD image sensor 16 detects the deviation e ofthe center ofthe white tape 20 from the center Yof the field A of the camera 17 in the running direction of the wagon and produces control signals according to the detected deviation. These control signals are fed to the left and right motors 8a and 8b to varythe revolving rates thereof so as to produce a difference in the revolving rate between the left and right drive wheels 4a and 4b. Thus, the wagon is automatically steered to the left or right so that the center ofthe white tape 20 coincides with the center Yofthefield A ofthe camera 17.

Figure 5 shows a control circuit ofthe automatically controlled wagon. The CCD image sensor 16 has a plurality of bits corresponding to respective divisions of the field A of the camera 17 divided in a directionXperpendiculartothe running direction of the wagon. These bits can judge whether the respective minute field divisions are bright or dark, and their output signals are fed to a position detection circuit 21.When the center of the white tape 20 is deviated byt1 to the right from the center Yoffield ofthe camera 17 as shown in Figure 5, for instance, bits from the one corresponding to an end X1 of the field A to the one corresponding to a dark field division preceding a bright field division provide a darkness signal or Lsignal, as shown in Figure 6, those corresponding to bright field divisions due to the white tape 20 provide a brightness signal or H signal, and those form the one corresponding to a darkfield division succeeding a bright field division till the one corresponding to the other end X2 of the field A provide a darkness signal or Lsignal.

The position detection circuit analyzes the output signal noted above and detects the deviation t1 between the center Yof the field A and the center of the white tape 20. More specifically, the circuit 21 calculates the deviation t1 in terms ofthe number of bits on the left or right side from the one corresponding to the field center Y, and it feds the calculation data to a speed setting circuit 22.

To the speed setting circuit 22 a speed signal from a running speed alteration device (not shown) is fed, and a pulse having a pulse duration corresponding to this speed signal is read outfrom a speed setting map 23 and fed to leftand right servo amplifiers 24 and 25to cause rotation ofthe leftand right motors 8a and 8b at a revolving rate corresponding to the supplied pulse. In this way, the wagon is run straight.

The revolving rate is increased with reducing pulse width.

The speed setting circuit 22, when supplied with the deviation e noted above, feeds data aboutthe direction of deviation (to the right or left) and number of deviation bits to the speed setting map 23 for comparison with respect to the prevailing running speed. According to the deviation, data of a corresponding increase or reduction of pulse frequency is fed to the servo amplifiers 24 and 25 through the speed setting circuit 22to cause deceleration ofthe motor 8a or8b on the opposite side to the direction of the deviation or acceleration of the motor 8b and 8a in the direction ofthe deviation. In this way, thewagon is steered inthe direction opposite to the deviation to thereby bring the center of the white tape 20 into coincidence with the field center Y.

Where the guide zone with the white tape thereof is curved as shown i n in Figure7,theleftwardor rightward deviation e is detected in the manner as described aboveto produce a difference in the revolving rate between the left and right motors 8a and 8b according to the detected deviation so as to steerthewagon along the curved guide zone.

In the above embodiment, the left and right motors 8a and 8b are controlled independentlytovarythe revolving speeds ofthe left and right drive wheels 4a and 4b. It is possible, however, to provide steering wheels on the deck 1 and control these steering wheels according to the deviation signal from the position detection circuit 21.

Figures 8 and 9 show a different arrangement of the guide zone. In this case, the white tape 20 is provided with an increased width portion 20b, and deceleration is caused when this increased width portion 20b is detected.

Figures 10 and 11 show a further arrangement of the guide zone. In this case, the white tape 20 ofthe guide zone 18 has a discontinuous portion 20c, and the wagon is stopped when this discontinuous portion 20c is detected. At this time, the wagon may be started again accordance to an externally supplied signal or a signal produced in accordance with the detection of the end of a loading/unloading operation. Atthe time of the re-start, the wagon is accelerated. Therefore, it is preferred to provide control such as to cause acceleration while accelerating a deviation side motor according to deviation to bring the center ofthewhite tape into coincidence with the center of the field of camera.

Figures 12 and 13 show a further arrangement of the guide zone. In this case, there are two distinct, i.e., first and second, white tapes 20 of guide zone 18.

The first white tape 20 has a corner portion 20a,while the second white tape 20 has a bent end portion 20d.

There is a cap S between aligned straight portions of the first and second white tapes 20. In this case, the wagon may be transferred from the second white tape 20 to the first one by causing straight running of the wagon for a predetermined period of time from the instant of detection of the bent end portion 20d.

Where the space below the wagon is too darkto detect the guide zone, a light source may be provided on the bottom surface of the wagon.

While the foregoing description has concerned with the application ofthe invention to a method of controlling the wagon with casters having excellent manoeuverability and revolving property, itwill be obvious that the method of control according to the invention is applicable to an automatically controlled vehicle having ordinary drive wheels and steering wheels, drive means including drive motors for driving the drive wheels and steering means having steering motors for the steering ofthe steering wheels.

While certain representative embodiments and details have been shown for the purpose of illustrating the prevent invention, it will be apparent tothose skilled in theartthatvarious changes and modifications may be madethereinwithout departing from the spirit and scope ofthe invention.

Claims

1. An apparatus for controlling an automatically controlled wagon for running along a guide zone provided on the ground surface, which comprises: a camera including a linear image sensor mounted on a deck such as to be able to detect a guide zone provided on the ground surface; a position detection circuitfor calculating the deviation ofthe wagon from said guide zone through analysis of a detection signal from said image sensor; and means for controlling the running of the wagon according to the calculation data from said position detection circuit.

2. An apparatus according to claim 1,wherein said means for controlling the running ofthe wagon includes a pairof servo amplifiersforcontrolling the revolving rate of drive motors for a pair of independent drive wheels mounted on said deck, a speed setting circuitfor providing a pulse signal determined according to the calculation data from said position detection circuit to said servo amplifiers, and a speed setting map for comparing a signal fed from said position detection circuit to said speed setting circuit and representing the deviation of the wagon from said guide zone with a speed signal fed to said speed setting circuit.

3. An apparatus according to claim 1 or2, wherein said linear image sensor is a CCD image sensor or an MOD image sensor.

4. Amethodofcontrollingtherunningofan automatically controlled wagon, which comprises: detecting the deviation from the center of said guide zone provided on the ground surface of the center of acamera provided on said decksuch astofacesaid guide zone and including a linear image sensor, the deviation detection being done from an output signal from the linear image sensor, and steering said wagon according to the detected deviation.

5. A method according to claim 4, wherein motors for each of a pair of independent drive wheels mounted on said deck are controlled according to the deviation between said guide zone and the center of the camera field such as to decelerate the motorforthe drive wheel on the opposite side to the direction of the deviation and accelerate the motorforthe drive wheel on the side ofthe direction of the deviation, thereby steering said wagon in the direction opposite to the direction of deviation.

6. A method according to claim 4, wherein said wagon is accelerated while one of a pair of motors for respective independent drive wheels mounted on said deck is accelerated according to the deviation between said guide zone and the center ofthe camera field,thereby steering said wagon in the opposite direction to the direction of deviation.

7. A method according to claim 4, wherein said guide zone has an increased width portion or a discontinuous portion, said wagon being decelerated or stopped when said increased width portion or discontinuous portion is detected.

8. A method according to claim 4,wherein said guide zone includes two distinct, i.e., first and second, guide zones, said first guide zone having a curved portion, said second guide zone having a straight portion aligned to a straight portion of said first guide zone and an end portion having a predetermined shape and facing said first guide zone, said wagon being run straightfor a predetermined period oftime upon detection of said end having the predetermined shape, thereby causing transfer of said wagon from said second guide zoneto said first guide zone.