AUTOMATIC GUIDANCE SYSTEM FOR WAREHOUSE TRUCKS AND THE LIKE

• US 3,612,206 A
• Filed: 07/07/1969
• Issued: 10/12/1971
• Est. Priority Date: 07/07/1969
• Status: Expired due to Term

• Current Assignee: Yale Materials Handling Corporation Route 523 and 31 Flemington New Jersey 08822
• Original Assignee: Frederick F. Ohntrup
• Inventors: Ohntrup, Frederick F.
• Primary Examiner(s): Betts, Kenneth H.
• Application Number:
  US04/839,417
• Time in Patent Office: 827 Days
• Field of Search: 180/98,79.1,79,2 340/32 318/20.220 191/1
• US Class Current: 180/168
• CPC Class Codes: G05D 1/0265 using buried wires

Abstract

A self-steering vehicle such as a warehouse truck is guided over a preprogrammed path by guidance wires which are arranged to form an x-y coordinate grid. The vehicle navigates by following a first coordinate guidance wire while counting the number of second coordinate guidance wires which it crosses. When the number of crossings counted indicates arrival at a particular grid intersection where a 90* course change is required, the vehicle executes a right angle turn. Thereafter it follows one of the second coordinate wires while counting first coordinate wire crossings. A series-connected sinuous wire configuration simplifies the problems of energizing the wires, to make them detectable by inductive sensors on board the vehicle. The excitations applied to the two coordinate wires are 90* out of phase with each other, so as to cancel steering errors which would otherwise be caused by a distortion of the guidance wire fields which occurs when permeable material is in, on, or adjacent to the vehicle. The 90* course changes are accomplished by a pivotal maneuver; a special type of in-place turn which avoids losing the orientation of the vehicle relative to the guidance wires. A perpendicularity sensing circuit detects when the pivotal turn has been completed and the vehicle has been rotated into proper alignment with the next coordinate wire to be followed.

Claims

1. An automatic vehicle guidance system comprising:

a vehicular traffic field having a grid of at least two guidance wires crossing said fieLd and intersecting to define respective coordinates in said field;

a vehicle having means for following a first one of said guidance wires defining a first one of said grid coordinates, and means for counting each intersection with a second one of said guidance wires defining a second one of said grid coordinates whereby to detect the arrival of said vehicle at a predetermined grid intersection; and

means for executing a turn from said first coordinate wire to follow said second coordinate wire at said predetermined grid intersection, said turning means being arranged to perform an in-place turn about an axis of rotation passing substantially through said grid intersection.

2. A system as in claim 1 wherein:

said grid comprises x and y conductors defining a rectangular coordinate system; and

said turning means is arranged to turn said vehicle through a right angle from a conductor defining one of said coordinates to follow a conductor defining another of said coordinates.

3. A system as in claim 1 further comprising:

means for detecting when said turn has been completed.

4. A system as in claim 3 wherein:

said completion detection means is arranged to detect when the axis of said vehicle is substantially perpendicular to said first coordinate wire.

5. A vehicle adapted to be automatically guided through a coordinate grid defined by at least two intersecting guidance wires, said vehicle comprising:

means for following a first coordinate guidance wire;

means for counting each intersection with a second coordinate guidance wire whereby to detect the arrival of said vehicle at a predetermined grid intersection;

sensors positioned to be on opposite sides of the followed wire when said vehicle is centered thereover; and

vehicle steering means including a phase-insensitive balanced network which has an output terminal and is connected across said sensors so that the potential of said output terminal varies in one direction or the other when the relationship between the magnitudes of the outputs of the left and right sensors is tipped in one direction or the other respectively, and a steering mechanism which is connected to said output terminal and responsive to the direction of variation of said potential to determine the direction of variation of said potential to determine the direction in which said vehicle is steered.

6. A vehicle as in claim 5 further comprising:

means for executing a turn from said first coordinate wire to follow said second coordinate wire at said predetermined grid intersection.

7. A vehicle as in claim 6 further comprising:

programmable means responsive to said counting means for actuating said turning means when the number of intersections counted equals a predetermined quantity.

8. A vehicle as in claim 5 wherein:

said sensors are connected together with their outputs in series aiding relationship; and

said balanced network comprises a voltage divider coupled across both said sensors, an output capacitor one side of which is connected to the center potential point of said divider and the other side of which is connected to said network output terminal, providing a first unidirectional conduction path from the high potential end of said divider to said output side of said capacitor and a second unidirectional conduction path from said output side of said capacitor to the low potential end of said divider.

9. A vehicle as in claim 8 wherein:

said turning means is arranged to pivot said vehicle substantially in place whereby to remain at said grid intersection while turning.

10. A vehicle as in claim 9 further comprising:

a pair of nonsteerable wheels for rollably supporting said vehicle; and

at least one additional wheel which is pivotable for steering and rollably supporting said vehicle; and

at least one additional wheel which is pivotable for steering and rollably supporting said vehicle;

said wire-followinG means being arranged to drive said vehicle forward along a followed guidance wire, to sense displacement of said vehicle from said followed wire, and to pivot said steering wheel to perform a moving turn while driving forward along said wire whereby to steer said vehicle closer to said followed wire when said vehicle is diverted therefrom; and

said turning means being arranged to pivot said wheel in a manner to perform said in-place turn about an axis of rotation passing through said vehicle.

11. A vehicle as in claim 10 wherein:

there are two of said pivotable wheels for steering and rollably supporting said vehicle, and located at opposite corners at one end thereof; and

said turning means is arranged to pivot said steering wheels at different rates until both said wheels are positioned to roll about a common axis of vehicle rotation.

12. A system as in claim 10 wherein said vehicle further comprises:

means for terminating the forward drive of said vehicle during said in-place turn.

13. A vehicle as in claim 12 further comprising:

means for detecting the completion of said turn.

14. A vehicle as in claim 13 further comprising:

means responsive to said completion detector for resuming the forward drive of said vehicle after completion of said turn.

15. A vehicle as in claim 13 wherein said completion detector comprises:

means for detecting when the axis of said vehicle becomes substantially perpendicular to said first coordinate wire at the completion of said turn.

16. A vehicle as in claim 15 wherein said perpendicularity detector comprises:

means aboard said vehicle for sensing degree of proximity to said first coordinate wire, and positioned on said vehicle so as to approach closest to said first coordinate wire in the course of said in-place turn when said vehicle axis is perpendicular thereto; and

means for detecting the positive peak of the output of said proximity sensor.

17. A vehicle as in claim 16 wherein said positive peak detecting means includes:

a peak detector circuit; and

polarity-sensitive means responsive to said peak detector circuit for distinguishing a decrease from an increase.

18. A vehicle as in claim 16 wherein:

said proximity detector means also provides the input to said intersection counting means during forward drive of said vehicle.

19. An automatic vehicle guidance system comprising:

a vehicular traffic field having a grid of at least two guidance wires crossing said field and intersecting to define respective coordinates in said field;

a vehicle having means for following at times a first one of said guidance wires defining a first one of said grid coordinates, and means using the second wire for counting each intersection, with a second one of said guidance wires defining a second one of said grid coordinates whereby to detect the arrival of said vehicle at a predetermined grid intersection;

means for electrically energizing said first and second coordinate wires; and

means for rendering said first coordinate wire following means immune to the influence of the field of said second coordinate wire.

20. A system as in claim 19 wherein:

said guidance wire following means on said vehicle includes a pair of inductive sensors laterally spaced from each other on said vehicle, and vehicle steering means which are responsive to the magnitude relationship but not to the phase relationship between the outputs of said sensors when said vehicle is not centered over the followed wire to steer said vehicle in the direction to center it thereover; and

said guidance wire energizing means applies respective AC components to said first and second coordinate wires of substantially the same frequency and substantially 90* out of phase with each other and thereby rendering said first coordinate wire following means immune to the influence of the field of said second coordinate wire.