Downward compatible AGV system and methods

• US 5,650,703 A
• Filed: 04/25/1996
• Issued: 07/22/1997
• Est. Priority Date: 06/28/1990
• Status: Expired due to Term

• Current Assignee: HK Systems Incorporated (KION GROUP AG)
• Original Assignee: HK Systems Incorporated (KION GROUP AG)
• Inventors: Zuercher, Joseph, Whatcott, Gary L., Petersen, John A. M., Mottes, Rick S., Guest, Vaughn W., Bloomfield, Bryan A., Christensen, L. Bruce, Forman, Robert K., Yardley, James V., Schutten, Herman P.
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US08/637,919
• Time in Patent Office: 453 Days
• Field of Search: 318/587, 318/139, 318/568.1-568.28, 318/586, 180/167-169, 901/1, 901/2, 901/3, 901/5, 901/9, 395/80-89, 364/424.01, 364/424.02, 364/426
• US Class Current: 318/587
• CPC Class Codes: G05D 1/0261 using magnetic plots
• CPC Class Codes: G05D 1/0265 using buried wires
• CPC Class Codes: G05D 1/027 comprising intertial navigation means, e.g. azimuth detector inertial navigation G01C21/16; inertial navigation combined with non-inertial navigation instruments G01C21/165
• CPC Class Codes: G05D 1/0272 comprising means for registering the travel distance, e.g. revolutions of wheels measuring distance traversed on the ground by vehicles, e.g. using odometers G01C22/00
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30

Abstract

An automated guided vehicle (AGV) control system which is downward compatible with existing guidewire systems providing both guidewire navigation and communication and autonomous navigation and guidance and wireless communication between a central controller and each vehicle. FIGS. 90, 91, 92, 93, and 94 provide a map showing relative orientation of the schematic circuits seen in FIGS. 90A-B, 91A-B, 92A-B, 93A-B, and 94A-B, respectively over paths marked by update markers which may be spaced well apart, such as fifty feet. Redundant measurement capability using inputs from linear travel encoders from the vehicle'"'"'s drive wheels, position measurements from the update markers, and bearing measurements from a novel angular rate sensing apparatus, in combination with the use of a Kalman filter, allows correction for navigation and guidance errors caused by such factors as angular rate sensor drift, wear, temperature changes, aging, and early miscalibration during vehicle operation. The control system employs high frequency two-way data transmission and reception capability over the guidewires and via wireless communications. The same data rates and message formats are used in both guidewire and wireless communications systems. Substantially the same communications electronics are used for the central controller and each vehicle. Novel navigation and guidance algorithms are used to select and calculate a non-linear path to each next vehicle waypoint when the vehicle is operating in the autonomous mode. The non-linear path originates with an initial direction equal to the heading of the vehicle as it enters the path and a waypoint heading defined as part of the message received from the central control system which plans and controls travel of each vehicle in the system.

Claims

1. A system for non-guidewire navigation and guidance of an automated guided vehicle across a floor, the system comprising:

a plurality of reference points disposed in said floor;

a wireless receiver disposed on said vehicle which receives a wireless control signal, said wireless control signal including a predetermined destination and being sent from an off-vehicle controller;

a processor which selects and calculates a guidepath from a plurality of possible guidepaths based upon a current vehicle position which comprises an origin for and bearing of the selected guidepath, and based upon said predetermined destination;

a plurality of reference point sensors disposed on said vehicle which generate position information by detecting said plurality of reference points, said position information being used by a vehicle navigation and guidance system to constrain said vehicle to said selected guidepath such that the path actually traversed by said vehicle comprises said predetermined destination.

2. A system according to claim 1, wherein said wireless receiver also receives a desired vehicle exit bearing from said off-vehicle controller.

3. A system according to claim 1, wherein said selected guidepath is also selected and calculated based upon a desired vehicle exit bearing away from said predetermined destination.

4. A system according to claim 1, wherein said guidepath comprises a plurality of guidepath segments separated by a plurality of intermediate destinations, wherein said wireless receiver also receives said plurality of intermediate destinations, and wherein said selecting and calculating means further selects and calculates said plurality of guidepath segments based upon said plurality of intermediate destinations.

5. A system according to claim 1, wherein each of said plurality of reference points comprises a stationary permanent magnet.

6. A system according to claim 1,

wherein each of said plurality of reference points comprises a stationary magnet which provides a sensible magnetic field that diminishes with increasing distance from the center of said magnetic field;

wherein said plurality of reference point sensors comprises a plurality of magnetic-field sensors, and wherein each of said plurality of magnetic-field sensors produce a search variable representing sensed magnetic field strength;

and wherein said vehicle navigation and guidance system further includes

a memory disposed on said vehicle, said memory having a plurality of predetermined patterns of magnetic field strength stored therein as a function of distance from the center of a magnetic field to a sensor on said vehicle, and

a sensor processor disposed on said vehicle and coupled to said memory, said sensor processor processing said search variables and computing a mean estimated lateral position of said magnetic field center relative to said vehicle based upon an interpolation of each search variable within said stored predetermined pattern.

7. A system according to claim 1, wherein said plurality of reference point sensors are dynamically calibrated as said vehicle travels between each of said plurality of floor disposed reference points.

8. A system according to claim 1, wherein said plurality of reference points each comprise a magnet which emits a detectable field which is unipolar in character.

9. A system according to claim 1,

wherein said plurality of reference point sensors include first and second reference point sensors, said first and second reference point sensors having a center-to-center separation distance;

and wherein said first and second reference point sensors are used to measure the position of said traversed reference point relative to said vehicle more precisely than one-half said center-to-center separation distance.

10. A system according to claim 1, wherein said vehicle further includes

a digital-to-analog (D/A) converter, said D/A converter digitizing an output of one of said plurality of reference point sensors, said output being digitized so as to be assigned one of a plurality of possible values, said plurality of possible values including

a first value, said first value corresponding to a minimum distance measurement between said one reference point sensor and said one reference point,

a second value, said second value corresponding to a maximum distance measurement between said one reference point sensor and said one reference point,

a range of intermediate values, said range of intermediate values corresponding to a range of distance measurements in between said maximum distance measurement and said minimum distance measurement;

and wherein said navigation and guidance system measures the position of said traversed reference point relative to said vehicle based on said digitized output.

11. A system according to claim 1, wherein each of said plurality of reference points comprises a magnet, wherein said plurality of reference point sensors are hall effect sensors disposed in a single transverse array, and wherein said single transverse array of hall effect sensors senses only a single reference point at each measurement site.

12. A method of causing an automated guided vehicle to reach a predetermined destination comprising the steps of:

(a) providing a floor comprising a pathway marked by at least one floor disposed reference point for non-guidewire navigation and guidance of said vehicle, said pathway comprising said predetermined destination;

(b) sending a wireless control signal from a central control system, said wireless control signal including information pertaining to a location of said predetermined destination;

(c) receiving and utilizing said wireless control signal at said automated guided vehicle;

(d) optionally obtaining floor related, vehicle-generated coordinate signals through vehicle detection of information from said floor disposed reference point;

(e) communicating said vehicle-generated coordinate signals and said control signal to a vehicle-borne navigation and guidance system; and

(f) calculating, in said navigation and guidance system, a guide path comprising exit target coordinates and an exit bearing for said vehicle from said pathway along which said vehicle is to be navigated and guided.

13. A method according to claim 12, further comprising the step of sending additional wireless control signals from said central control system so as to selectively direct the automatic guided vehicle along at least a portion of the pathway toward said predetermined destination.

14. A method according to claim 12, wherein it is necessary to repeat the steps (b) through (e) to cause said vehicle to reach said predetermined destination, and further comprising the step of repeating the steps (b) through (e) until said vehicle reaches said predetermined destination.

15. A method according to claim 12, wherein said guidepath comprises a plurality of guidepath segments separated by a plurality of intermediate destinations, and further comprising the steps of

sending a plurality of additional wireless control signals having information pertaining to locations of said plurality of intermediate destinations;

and

calculating said plurality of guidepath segments based on said information pertaining to said locations of said plurality of intermediate destinations.

16. A method according to claim 12, wherein said reference point is a stationary permanent magnet, and wherein said reference point provides said navigation and guidance system with positional reference information.

17. A method according to claim 16, wherein the obtaining step further comprises the steps of

(a) mounting said permanent magnet in said floor to provide a sensible magnetic field;

(b) providing an array of magnetic-field sensors on said vehicle;

(c) storing a plurality of predetermined patterns of magnetic field strength as a function of distance from the center of a magnetic field to one of said sensors on said vehicle;

(d) sensing said magnetic field emanating from said magnet with said sensors thereby producing a plurality of voltages representative of sensed magnetic field strength, each of said sensors producing one of said plurality of voltages;

(e) converting said plurality of voltages into a plurality of distance values, said converting step including the step of accessing said stored plurality of predetermined patterns of magnetic field strength; and

(f) estimating the position of said vehicle based upon said converting step.

18. A method according to claim 12, wherein the obtaining step (d) further comprises the step of deriving bearing related signals from a vehicle tuning fork gyro for use by said navigation and guidance system.

19. A method according to claim 18, wherein the obtaining step (d) further comprises the step of controlling the orientation of said tuning fork gyro using an inertial platform.

20. A method according to claim 12, wherein the obtaining step (d) further comprises the step of deriving signals from wheel encoders which measure differential in wheel rotations for use by said navigation and guidance system.

21. A method according to claim 12, wherein the obtaining step (d) further comprises the step of obtaining signals from stationary update markers along one portion of said pathway and obtaining signals from a guidewire along another portion of said pathway.

22. A method according to claim 12, wherein during said guidepath calculating step (f), said guidepath is calculated based upon a then current vehicle position which comprises an origin for and bearing of said selected guidepath, and based upon said predetermined destination and a desired vehicle exit bearing from said predetermined destination.

23. A method for controlling movement of an automated guided vehicle which operates in a self-contained guidance mode whereby said vehicle operates up to a given speed and moves from one path segment to another path segment, comprising the following steps:

(a) providing a floor comprising a pathway, said pathway comprising a vehicle target destination;

(b) sending from a non-vehicle source a move command comprising said vehicle target destination for said vehicle;

(c) receiving said move command by said automated guided vehicle;

(d) decoding said move command related to said vehicle target destination of said vehicle;

(e) transferring said decoded move command to an on-board vehicle controller; and

(f) calculating, in said on-board vehicle controller, a guide path for said vehicle to cause said vehicle to move toward said vehicle target destination.

24. A method according to claim 23, wherein said move command sent during the step (a) also comprises a direction for said vehicle at said vehicle target destination.

25. A method according to claim 23, wherein the step (c) is performed in a background area of a multi-tasking operation in a computer on-board said vehicle.

26. A method according to claim 23, wherein it is necessary to repeat the steps (b) through (e) to enable said vehicle to reach said target destination, and further comprising the step of repeating steps (b) through (e) whereby subsequent move commands are received timely such that said vehicle continues without slowing down.

27. A method according to claim 23, wherein said guidepath comprises a plurality of guidepath segments separated by a plurality of intermediate destinations, and further comprising the steps of

sending a plurality of additional move commands comprising said plurality of intermediate destinations for said vehicle;

selecting and calculating said plurality of guidepath segments based on said plurality of intermediate destinations.

28. A method according to claim 23, further comprising the step of providing said on-board vehicle controller with positional reference information, said information providing step being performed by a reference point.

29. A method according to claim 28, wherein said reference point is a stationary permanent magnet disposed in said floor along which said vehicle moves.

30. A method according to claim 29, further comprising the steps of

(a) mounting said magnet in said floor to provide a sensible magnetic field;

(b) providing an array of magnetic-field sensors on said vehicle;

(c) storing a plurality of predetermined patterns of magnetic field strength as a function of distance from the center of a magnetic field to one of said sensors on said vehicle;

(d) sensing said magnetic field emanating from said magnet with said sensors, said sensing step producing a plurality of voltages representative of sensed magnetic field strength;

(e) converting said plurality of voltages into a plurality of distance values, said converting step including the step of accessing said stored plurality of predetermined patterns of magnetic field strength; and

(f) estimating the position of said vehicle based upon said converting step.

31. A method according to claim 23, wherein during said guidepath calculating step said guidepath is calculated based upon a then current vehicle position which comprises an origin for and bearing of the selected guidepath, and based upon said vehicle target destination and a desired vehicle exit bearing from said target destination.

32. An automated guided vehicle system for autonomous navigation of an automated guided vehicle along a pathway on a floor to a predetermined destination, the system comprising:

a plurality of widely-spaced, floor-disposed reference points which mark said pathway for non-guidewire navigation and guidance of said vehicle;

a guide path comprising exit target coordinates for said vehicle from said pathway along which said vehicle is to be navigated and guided, said guide path enabling said vehicle to navigate said pathway;

a vehicle controller having a vehicle controller transceiver, said vehicle controller transceiver sending a wireless control signal to said vehicle which includes information pertaining to a location of said predetermined destination; and

said vehicle, said vehicle further including

a vehicle transceiver which receives said wireless control signal from said vehicle controller, said vehicle transceiver in conjunction with said vehicle controller transceiver forming a wireless communication link,

a navigation and guidance system which utilizes said wireless control signal from said vehicle controller transceiver, said navigation and guidance system including

an encoder which measures distance traveled by said vehicle,

a gyro which measures bearing of vehicle travel,

a reference point sensor system including a plurality of sensors which generates position information by detecting said floor disposed reference points, and

a processor which processes said position information from said reference point sensor system and information from said encoder and said gyro to enable said automatic guided vehicle to follow said guide path autonomously.

33. An automated guided vehicle system according to claim 32, wherein said plurality of reference point sensors are dynamically calibrated as said vehicle travels between each of said plurality of floor disposed reference points.

34. An automated guided vehicle system according to claim 32, wherein said plurality of reference points each comprise a magnet which emits a detectable field which is unipolar in character.

35. An automated guided vehicle system according to claim 32,

wherein said plurality of reference point sensors include first and second reference point sensors, said first and second reference point sensors having a center-to-center separation distance;

and wherein said first and second reference point sensors are used to measure the position of said traversed reference point relative to said vehicle more precisely than one-half said center-to-center separation distance.

36. An automated guided vehicle system according to claim 32, wherein said vehicle further includes

a digital-to-analog (D/A) converter, said D/A converter digitizing an output of one of said plurality of reference point sensors, said output being digitized so as to be assigned one of a plurality of possible values, said plurality of possible values including

a first value, said first value corresponding to a minimum distance measurement between said one reference point sensor and said one reference point,

a second value, said second value corresponding to a maximum distance measurement between said one reference point sensor and said one reference point,

a range of intermediate values, said range of intermediate values corresponding to a range of distance measurements in between said maximum distance measurement and said minimum distance measurement;

and wherein said navigation and guidance system measures the position of said traversed reference point relative to said vehicle based on said digitized output.

37. An automated guided vehicle system according to claim 32, wherein each of said plurality of reference points comprises a magnet, wherein said plurality of reference point sensors are hall effect sensors disposed in a single transverse array, and wherein said single transverse array of hall effect sensors senses only a single reference point at each measurement site.

38. A method of causing an automated guided vehicle to reach a predetermined destination comprising the steps of:

(a) disposing a plurality of reference points in a floor for non-guidewire navigation and guidance of said vehicle, said reference points marking a pathway, said pathway extending from a vehicle origin to said predetermined destination;

(b) determining a guide path comprising exit target coordinates and an exit bearing for said vehicle from said pathway along which said vehicle is to be navigated and guided;

(c) sending a wireless control signal from an off-vehicle controller, said wireless control signal including information pertaining to a location of said predetermined destination;

(d) receiving and utilizing said wireless control signal at said automated guided vehicle; and

(e) autonomously traversing said guide path, said traversing step including the step of constraining said vehicle to said guide path such that the path actually traversed by said vehicle is substantially the same as said guide path, said constraining step including the steps of

(1) generating information pertaining to a linear distance traveled by said vehicle and communicating said linear distance information to a vehicle-borne navigation and guidance system,

(2) generating information pertaining to bearing of said vehicle and communicating said bearing information to said vehicle-borne navigation and guidance system, and

(3) generating floor-related position information by detecting said floor disposed reference points, and communicating said floor-related position information to said vehicle-borne navigation and guidance system.

39. A method according to claim 38, wherein said guide path is determined after said automated guided vehicle is put into operation, and wherein the combination of the determining and traversing steps further comprises the following substeps:

determining a sequence of reference points which extend non-colinearly from said vehicle origin to said predetermined destination, said sequence of reference points including first, second, and third reference points,

providing said automated guided vehicle with the coordinates of said first, second and third reference points,

calculating a first calculated path segment, said first calculated path segment extending from said vehicle origin to said first reference point, said first calculated path segment being calculated based upon said vehicle origin, a bearing away from said vehicle origin, said coordinates of said first reference point, and a desired vehicle bearing at said first reference point,

traversing a first traversed path segment to said first reference point, wherein said first traversed path segment is substantially the same as said first calculated path segment, and wherein differences between said first traversed path segment and said first calculated path segment are attributable at least in part to vehicle travel error,

obtaining a first vehicle position measurement from said first reference point, said first vehicle position measurement indicating the coordinates of said vehicle when said vehicle reaches said first reference point,

calculating a second calculated path segment, said second calculated path segment extending from said coordinates of said vehicle when said vehicle reaches said first reference point to said coordinates of said second reference point, said second calculated path segment being calculated based upon said coordinates of said vehicle obtained from said first reference point, a bearing of said vehicle when said vehicle reaches said first reference point, said coordinates of said second reference point and a desired vehicle bearing at said second reference point,

traversing a second traversed path segment to said second reference point, wherein said second traversed path segment is substantially the same as said second calculated path segment, and wherein differences between said second traversed path segment and said second calculated path segment are attributable at least in part to vehicle travel error,

obtaining a second vehicle position measurement from said second reference point, said second vehicle position measurement indicating the coordinates of said vehicle when said vehicle reaches said second reference point,

calculating a third calculated path segment, said third calculated path segment extending from said coordinates of said vehicle when said vehicle reaches said second reference point to said coordinates of said third reference point, said third calculated path segment being calculated based upon said coordinates of said vehicle obtained from said second reference point, a bearing of said vehicle when said vehicle reaches said second reference point, said coordinates of said third reference point and a desired vehicle bearing at said third reference point, and

traversing a third traversed path segment to said third reference point, wherein said third traversed path segment is substantially the same as said third calculated path segment, and wherein differences between said third traversed path segment and said third calculated path segment are attributable at least in part to vehicle travel error,

and wherein said first, second and third traversed path segments, and additional traversed path segments if necessary, extend from said vehicle origin to said predetermined destination.

40. A method according to claim 38, wherein said guide path comprises a plurality of guide path segments, each guide path segment being calculated based upon an actual vehicle position at an origin of the guide path segment, an actual bearing away from said origin, an endpoint of said guide path segment, and a desired vehicle bearing at said endpoint.

41. A method according to claim 38, wherein said guide path is formed of a sequence of reference points which are disposed non-colinearly with respect to each other, said sequence of reference points being a subset of said plurality of reference points.

42. A method according to claim 38, wherein said guide path is formed of at least one straight path segment and at least one curved path segment, the combination of said at least one straight path segment and at least one curved path segment being disposed between two consecutive reference points, and wherein said at least one straight path segment and said at least one curved path segment are separately calculated.

43. A method according to claim 38, wherein said guide path determining step further includes the step of calculating a guidepath, and wherein said guide path calculating step further includes the steps of

(1) generating a coefficient which at least partially defines a curved path segment,

(2) calculating said curved path segment based on said coefficient,

(3) sequentially combining said curved path segment with a straight line segment, and

(4) repeating said (1) generating, (2) calculating and (3) combining steps as necessary until said guide path has been determined.

44. A method according to claim 38, wherein said guide path determining step further includes the steps of

(1) determining a sequence of reference points which extend non-colinearly from said vehicle origin to said desired vehicle destination,

(2) providing said vehicle with the coordinates of said sequence of reference points, and

(3) calculating a sequence of guide path segments based on said coordinates of said sequence of reference points, wherein said individual reference points mark entry ends and departure ends of at least some individual guide path segments.

45. A method according to claim 38, further comprising the step of dynamically calibrating a plurality of reference point sensors which detect said floor disposed reference points, said plurality of reference point sensors being dynamically calibrated such that calibration occurs as said vehicle travels between each of said plurality of floor disposed reference points.

46. A method according to claim 38, wherein said plurality reference points each comprise a magnet which emits a detectable field which is unipolar in character.

47. A method according to claim 38,

further comprising the step of providing said vehicle with a plurality of reference point sensors including at least first and second reference point sensors, said first and second reference point sensors having a center-to-center separation distance;

and wherein the step of generating floor-related position information further includes the step of making a position measurement, the position measurement representing the position of said vehicle with respect to one of said floor disposed reference points, said position measurement being substantially more precise than one-half the center-to-center separation distance.

48. A method according to claim 47,

and wherein the step of generating floor-related position information further comprises the steps of

sensing one of said plurality of reference points with said plurality of reference point sensors,

digitizing an output of one of said plurality of reference point sensors, said output being digitized so as to be assigned one of a plurality of possible values, said plurality of possible values including

a first value, said first value corresponding to a minimum distance measurement between said one reference point sensor and said one reference point,

a second value, said second value corresponding to a maximum distance measurement between said one reference point sensor and said one reference point,

a range of intermediate values, said range of intermediate values corresponding to a range of distance measurements in between said maximum distance measurement and said minimum distance measurement, and determining the position of said vehicle based on said digitized output.

49. A method according to claim 48, wherein each of said plurality of reference points comprises a magnet, wherein said step of generating floor-related position information is performed by a single transverse array of hall effect sensors, and wherein said single transverse array of hall effect sensors senses only a single reference point at each measurement site.