Downward compatible AGV system and methods

• US 5,281,901 A
• Filed: 12/03/1990
• Issued: 01/25/1994
• Est. Priority Date: 12/03/1990
• Status: Expired due to Term

• Current Assignee: HK Systems Incorporated (KION GROUP AG)
• Original Assignee: Eaton-Kenway Incorporated
• Inventors: Zuercher, Joseph, Whatcott, Gary L., Yardley, James V., Schutten, Herman P., Petersen, John A. M., Mottes, Rick S., Guest, Vaughn W., Bloomfield, Bryan A., Christensen, L. Bruce, Forman, Robert K.
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US07/621,486
• Time in Patent Office: 1,149 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: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• 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. Autonomous vehicle navigation comprises travel over paths marked by update markers which may be spaced well apart, such as fifty feet Redundant measurement capability comprising 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 comprises 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 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 comprises 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. An automatic guided vehicle comprising:

a tri-mode, on-board vehicle navigational and guidance system comprising means for navigating and guiding over one or more of a plurality of distinct and independent pathway defining means;

the tri-mode navigational and guidance system further comprising;

means for detecting signals from a floor fixed update marker as the automated guided vehicle passes each update marker and means by which the floor location and bearing of the automatic guided vehicle is determined from the update marker signals and exclusively used for guidance without receiving signals from a guidewire;

means for detecting signals from an active guidewire along which the automated guided vehicle is displaced and means by which a bearing to be traversed by the automatic guided vehicle is established from the guidewire signals and exclusively used for guidance;

means for detecting signals from a passive guidewire loop when the automated guided vehicle is disposed within detectable range and means by which the automatic guided vehicle is precisely located at a predetermined site.

2. A method of controlling an automatic guided vehicle comprising the steps of:

a. placing the automatic guided vehicle upon a floor comprising a pathway primarily marked by fixed, signal generating update markers, detecting update marker signals without use of signals from a guidewire as the vehicle moves between update markers determining floor coordinates defining the location of the automatic guided vehicle from the update marker signals;

b. placing the same automatic guided vehicle upon a floor comprising a pathway primarily marked by an active guidewire from which guidewire signals emanate, detecting the guidewire signals and determining the bearing to be traversed by the automatic guided vehicle across the floor from detected guidewire signals; and

c. placing the same automatic guided vehicle upon a floor comprising a passive guidewire and a docking site, energizing the passive guidewire by said vehicle and detecting passive guidewire signals at said vehicle and precisely docking the automatic guided vehicle at a docking site using the passive guidewire signals.

3. An automatic guided vehicle system comprising:

at least one floor traversing automatic guided vehicle comprising a top surface permanently affixed atop said vehicle, said surface being free of pathway sensors, and means for detecting signals from floor update markers which define at least in part navigational and guidance information for a vehicle pathway defining active guidewire for another pathway and a vehicle directional sensor comprising tuning fork means;

means for detecting bearing independent of signals from the update markers and the active guidewire, each of said mans being disposed below said top surface;

means disposed on the vehicle beneath said top surface and affixed to said vehicle for guiding and navigating said vehicle based upon signals received from either of said detecting means and said vehicle directional sensor.

4. A system according to claim 3 further comprising Kalman filter means to which a directional output derived from the tuning fork means is communicated to compensate for error due to tuning fork drift.

5. A system according to claim 4 further comprising means communicating a coordinates output to the Kalman filter means to compensate for coordinates error.

6. A system according to claim 3 wherein the top surface of the vehicle comprises means for loading and lifting.

7. A system according to claim 3 further comprising inertial table means which maintains the tuning fork means in an essentially fixed orientation relative to said floor by which high gain is obtained.

8. A method of providing coordinate and bearing information concerning the location and direction of travel of an automatic guided vehicle traversing a path across a floor, comprising the steps of:

providing a floor-carried coordinate-defining pathway mark over which said vehicle is caused to travel from time to time;

generating a vehicle tuning fork signals and using the tuning fork signal to acquire a first estimate of the bearing of the vehicle;

processing said tuning fork signal to at least correct for tuning fork drift fork and thereby more accurately defining the bearing of the vehicle;

detecting a signal emitted by said floor-carried coordinate-defining pathway mark in the immediate vicinity of the vehicle and using said detected signal to ascertain the floor coordinates and bearing of the vehicle.

9. A method according to claim 8 comprising the step of delivering a signal representative of the more accurately defined bearing and a signal representative of the ascertained floor coordinates to an error compensating site.

10. A method according to claim 8 wherein the generating, processing and detecting steps occur in generating and detecting apparatus disposed within and below, but not at the top of the vehicle.

11. An automatic guided vehicle system comprising:

a floor traversed by automatic guided vehicles;

at least one guidewire-controlled first automatic guided vehicle comprising location and bearing sensing means and guidewire transceiver means;

at least one wireless-controlled second automatic guided vehicle comprising non-guidewire location and bearing sensing means and wireless transceiver means;

floor guidewire means over which at least said first automatic guided vehicle traverses;

control center means comprising control guidewire transceiver means and control wireless transceiver means in communication with both vehicles, in combination the control guidewire transceiver means and control wireless transceiver means comprising means by which control information is communicated, the control information being communicated with compatible data rate transfer characteristics and with identical information content along the floor guidewire means to the guidewire transceiver means of the at least one guidewire controlled first vehicle and wirelessly to the wireless transceiver means of the at least one wireless-controlled second vehicle simultaneously.

12. A system according to claim 11 wherein the means by which the identical control information is communicated comprise means communicating to both vehicles at substantially the same high baud rate.

13. A system according to claim 11 wherein each vehicle comprises means for sensing and calculating bearing and location of the vehicle and means upon receiving control information for changing the bearing traversed by the vehicle to reach a predetermined floor destination.

14. A system according to claim 11 wherein each said at least one first and second vehicle comprises at least one means for determining bearing and floor coordinates from at least one floor based path defining means.

15. A system according to claim 11 wherein each vehicle comprises means for calculating a path whereby the vehicle is guided to reach a predetermined floor destination at a predetermined bearing from a current location of the vehicle.

16. An automatic guided vehicle system comprising:

a floor;

a plurality of pathway defining means associated with the floor and comprising at least two of stationary update markers, active guidewires, and passive guide means each of which is individually and exclusively used to provide guidance signals for the vehicle over at least a portion of the floor;

at least one automatic guided vehicle comprising tri-mode vehicle navigational and guidance means;

the tri-mode navigational and guidance means comprising;

means for detecting the position of the stationary update markers relative to said at least one automatic guided vehicle and determining a floor location at which the automatic guided vehicle is disposed from time to time;

means for detecting the bearing of the automatic guided vehicle relative to the floor disposed active guidewire mans and determining a bearing of the automatic guided vehicle from time to time;

means for detecting the location and bearing of the passive guide means juxtaposed a docking site and thereby precisely guiding the automatic guided vehicle to a desired location at the docking site.

17. A system according to claim 16 wherein said passive guide means comprise means removable from said floor and other stationary objects whereby the passive guide means are moved from one place to another to establish a temporary guidepath.

18. A method of controlling an automatic guided vehicle comprising the steps of:

individually and collectively navigating and guiding the automatic vehicles under the direction of a master controller, across a floor comprising at least two of the following steps;

a. navigating and guiding at least one of the vehicles along a pathway defined by stationary, floor-disposed update markers, by determining the floor coordinates at which the one automatic vehicle is located from time to time by detecting the position of successive update markers, storing said coordinates, determining from said determined and stored floor coordinates the bearing and the error in the bearing of the one vehicle and using the error to correct the bearing of the at least one vehicle;

b. moving at least one of the vehicles along a pathway defined by an active guidewire, by establishing, by guidewire signals, the bearing to be traversed by the one automatic guided vehicle across the floor from time to time; and

c. moving at least one of the vehicles along a pathway defined by a passive guide, by precisely positioning the one automatic guided vehicle, at a desired parking site, using localized passive guide signals.

19. A method according to claim 18 wherein the third moving step comprises using power from the at least one automated guided vehicle to provide energy which generates the localized passive guide signals.

20. A method of providing coordinates and bearing information concerning the location of an automatic guided vehicle and causing the vehicle to traverse a path across a floor to a target destination comprising the steps of:

providing within the vehicle a means for calculating a guidepath, based upon the target destination and current floor coordinates and bearing of the vehicle, along which a guidance and navigation system contained within the vehicle causes the vehicle to traverse;

sending the target destination comprising target floor coordinates and a target bearing from an off-vehicle control center to the vehicle;

generating a tuning fork signal at the vehicle defining the bearing of the vehicle, processing the tuning fork signal to correct for drift and delivering the corrected tuning fork signal to the guidance and navigation system;

sensing a floor coordinates signal at the floor in the immediate vicinity of the vehicle, determining the position of the vehicle relative to the floor coordinates and delivering the sensed floor coordinates to the guidance and navigation system;

calculating the guidepath along which the guidance and navigation system causes the vehicle to traverse from the target destination, the position of the vehicle and bearing from the corrected tuning fork signal.

21. A method according to claim 20 further comprising the step of processing and bearing signal in combination with past and current floor coordinates signals to compensate for vehicle location and bearing errors.

22. A method according to claim 20 wherein the generating and creating steps occur in apparatus disposed below and within, and not at the top surface of, the vehicle.

23. A method according to claim 20 further comprising the step of maximizing gain and minimizing error during said generating step by controlling the directional orientation of the tuning fork from which the tuning fork signal is emitted.

24. A method of communicating and controlling vehicle travel in an unmanned automatic guided vehicle system comprising the steps of:

providing a guidewire pathway disposed in a floor over which at least one guidewire controlled first automatic guided vehicle travels and a non-guidewire marked pathway in the floor over which at least one second automated guided vehicle controlled by wireless communications travels;

selectively issuing compatible guidewire and wireless communications control signals comprising identical control information transmitted at a single data rate from a control center to the at least one guidewire controlled first automatic guided vehicle and to the at least one wireless controlled second automatic guided vehicle, respectively;

controlling travel of the first vehicle using communications control signals received by the first vehicle from the control center through the guidewire at the first vehicle;

controlling travel of the second vehicle exclusive of the guidewire by using communications control signals received by the second vehicle through wireless communications and sensing location and bearing of the second vehicle using non-guidewire guidepath marker navigational information derived at the second vehicle.

25. A method according to claim 24 further comprising the steps of using active guidewire signals to correct the bearing of the first vehicle to cause the first vehicle to reach a desired destination.

26. A method according to claim 24 further comprising the steps of correcting the bearing of the second vehicle at the second vehicle to cause the second vehicle to reach a desired destination.

27. A method according to claim 24 further comprising the steps of determining the error in any estimate of location of the first vehicle at the first vehicle and congruently correcting the displacement of the first vehicle under control of a navigation and guidance system disposed at the first vehicle.

28. A method according to claim 24 further comprising the steps of determining the error in any estimate of location of the second vehicle at the second vehicle and congruently correcting the displacement of the second vehicle under control of a navigation and guidance system disposed at the second vehicle.

29. A method according to claim 24 wherein the second controlling step comprises sensing at the second vehicle the bearing of the second vehicle via an angular rate tuning fork sensor disposed on the second vehicle.

30. A method according to claim 29 wherein during a first period, a third unmanned automatic guided vehicle performs as the first vehicle in the first travel controlling step and, during a second period, the third vehicle functions as the second vehicle in the second travel controlling step.

31. A navigation and guidance system for an automated guided vehicle comprising:

means disposed on said vehicle for receiving at any point along a vehicle route a target waypoint position and vehicle exit bearing from said waypoint from an off-vehicle controller;

means disposed on said vehicle for selecting and calculating a guidepath to be transversed by said vehicle from a plurality of possible guidepaths based upon a then current vehicle position which comprises an origin for and bearing of the selected guidepath and the target waypoint position and vehicle exit bearing from the target waypoint;

means for constraining said vehicle to the selected guidepath such that the origin of the selected guidepath comprises the existing vehicle bearing and location and the target waypoint position and said vehicle exit bearing away from the target waypoint.

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

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

(b) sending wireless control signals from a central control system to selectively direct the automatic guided vehicle along at least a portion of the pathway toward the predetermined destination;

(c) receiving and utilizing wireless control signals at the automated guided vehicle;

(d) optionally obtaining floor related, vehicle-generated coordinated signals through vehicle detection of information from the update marker;

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

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

(g) repeating steps (b) through (f) until the vehicle reaches the predetermined destination.

33. A method according to claim 32 wherein step (c) comprises the additional step of receiving and utilizing guidewire communication signals in causing the vehicle to reach a predetermined location.

34. A method according to claim 32 wherein the obtaining step (d) further comprises deriving bearing related signals from a vehicle tuning fork gyro for use by the navigation and guidance system.

35. A method according to claim 34 wherein step (d) further comprises the step of controlling the orientation of the tuning fork gyro using an inertial platform.

36. A method according to claim 32 wherein the obtaining step (d) comprises deriving signals from wheel encoders which measure differential in wheel rotations for use by the navigation and guidance system.

37. A method according to claim 32 wherein the obtaining step (d) comprises obtaining signals from stationary update markers along one portion of the pathway and obtaining signals from a guidewire along another portion of the pathway.

38. An automatic guided vehicle system for an autonomously-operating automatic guided vehicle, said system comprising:

means disposed in the autonomously operating automated guided vehicle for nulling navigation and guidance bearing and position errors, said means comprising;

at least two measuring means for redundantly estimating bearing of the vehicle;

for redundantly estimating a position of the vehicle;

at least one of said measuring means comprising means for detecting an update marker disposed in a floor below said vehicle;

means for receiving said estimates of bearing and position from said measuring means and assimilating redundantly measured position and bearing values;

Kalman filter means for processing the redundantly measured position and bearing values to provide error nulling corrections comprising at least one state variable;

means for navigating and guiding the automatic guided vehicle across the floor based upon error-nulling corrections provided by the Kalman filter means.

39. A method for controlling movement of an unmanned vehicle which operates in a self-contained guidance mode whereby the vehicle operates up to a given speed and moves from one path segment to another path segment without slowing down, comprising the following steps:

(a) sending from a non-vehicle source at least one move command comprising at least one vehicle target destination and direction for the unmanned vehicle sent from a non-vehicle source;

(b) receiving the at least one more command by the unmanned vehicle;

(c) decoding, in a background area of a multi-tasking operation in a computer on-board the unmanned vehicle, the at least one move command related to the vehicle target destination and direction of the unmanned vehicle;

(d) transferring the at least one decoded move command to an on-board vehicle controller to cause the unmanned vehicle to move toward a predetermined target destination;

(e) repeating steps (a) through (d) whereby each next move command is received timely such that the vehicle continues without slowing down.

40. A method according to claim 39 wherein the given speed is on the order of 200 feet/second.

41. A method for initially acquiring a signal from a guidewire by a hybrid unmanned vehicle which operates by self-contained navigation and guidance with occasional calibrating updates or, alternatively, by following a guidewire, comprising the following steps:

acquiring a signal emitted by the guidewire when the guidewire is first disposed below the vehicle in a detectable range of guidewire signal detecting antennas on the vehicle, but while the position of the guidewire is at an actual offset position relative to a longitudinal center line of the vehicle;

defining the actual offset position upon guidewire signal acquisition to be a desired relative center line-to-guidewire offset position; and

over a period of time, making small incremental reductions in the magnitude of the desired relative vehicle center line-to-guidewire offset position, thereby driving the vehicle to a position relative to the guidewire where the actual offset is zero.

42. An automatic guided vehicle system comprising:

at least one pathway marked exclusively by one type of pathway defining means derived from a group of different types of pathway-defining means, the different types of pathway-defining means comprising floor disposed update markers defining one type of pathway and active guidewires defining another type of pathway;

an unmanned automatic guided vehicle comprising on-board automated guided vehicle navigational and guidance means comprising means for navigating and guiding over each of said types of pathway defining means;

the navigational and guidance means further comprising;

means for detecting individual update markers as the automated guided vehicle passes across each update marker and by which the floor location and bearing of the automatic guided vehicle is determined to the exclusion of guidewires from time to time;

means for detecting active guidewires as the automated guided vehicle is moving along a pathway marked by active guidewires and by which a bearing to be traversed by the automatic guided vehicle is established.

43. A method of controlling at least one automatic guided vehicle comprising the steps of:

providing at least one pathway marked exclusively by a type of pathway defining means derived from a group of different types of pathway-defining means comprising floor disposed update markers and active guidewires;

providing on-vehicle automated guided vehicle navigation and guidance means for navigating and guiding over each of said pathway-defining means exclusive of other types of pathway-defining means;

navigating the at least one automatic vehicle comprising the navigation and guidance means across a floor by;

a. during a first period while the at least one vehicle is moving along a pathway marked exclusively by update markers, detecting an update marker as the vehicle moves within detectable distance of the marker and thereby determining the floor coordinates of the at least one automatic guided vehicle from time to time;

b. during a second period while the at least one automatic guided vehicle is moving along a pathway marked by an active guidewire, detecting guidewire signals from the active guidewire and thereby establishing the bearing to be traversed by the automatic guided vehicle across the floor.

44. An unmanned automatic guided vehicle system comprising:

at least one pathway marked exclusively by a type of pathway-defining means derived from a group of different types of pathway-defining means comprising floor disposed update markers and passive guidewire loops;

at least one unmanned automatic guided vehicle comprising on-board automated guided vehicle navigational and guidance means comprising means to the exclusion of other types of pathway-defining means;

the navigational and guidance means further comprising;

means for detecting each of said update markers as the automated guided vehicle passes across each update marker and by which the floor location of the automatic guided vehicle is determined from time to time;

means for energizing and detecting a passive guidewire loop when the automated guided vehicle is disposed within energizing and detecting range of a pathway marked by the passive guidewire loop and by which the automatic guided vehicle is precisely located at a predetermined site.

45. A method of controlling at least one automatic guided vehicle comprising the steps of:

providing at least one pathway marked exclusively by a type of pathway-defining means derived from a group of different types of pathway-defining means comprising floor disposed update markers and passive guidewires;

providing on-vehicle automated guided vehicle navigation and guidance means for navigating and guiding said vehicle over each of said pathway-defining means to the exclusion of other types of pathway-defining means;

navigating and guiding an automatic vehicle across a floor by;

a. during a first period while the at least one vehicle is moving along a pathway marked by update markers, detecting an update marker as the vehicle moves within detectable distance of the mark and thereby determining the floor coordinates of the at least one automatic guided vehicle from time to time;

b. during a second period, while the at least one automatic guided vehicle is moving along a pathway at a docking site marked by a passive guidewire, energizing a passive guidewire by said vehicle and detecting a signal from said energized passive guidewire by said vehicle and thereby precisely docking the automatic guided vehicle at the docking site using the localized passive guidewire signal.

46. An unmanned automatic guided vehicle system comprising:

at least one pathway exclusively marked by one type of pathway defining means derived from a group of different types of pathway-defining means comprising floor disposed update markers, active guidewires and passive guidewire loops;

at least one unmanned automatic guided vehicle comprising on-board automated guided vehicle navigational and guidance means comprising means for navigating and guiding over a plurality of said pathway-defining means.