Method and apparatus for a passive track system for guiding and controlling robotic transport and assembly or installation devices

• US 4,777,601 A
• Filed: 03/03/1986
• Issued: 10/11/1988
• Est. Priority Date: 03/15/1985
• Status: Expired due to Fees

• Current Assignee: Digitron AG Aarau
• Original Assignee: Jd-Technologie AG
• Inventors: Boegli, Peter
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Black, Thomas G.
• Application Number:
  US06/835,248
• Time in Patent Office: 953 Days
• Field of Search: 364/424, 364/443, 364/436, 318/587, 180/167, 180/168, 180/169, 250/202
• US Class Current: 701/23
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70
• CPC Class Codes: G05D 1/0244 using reflecting strips

Abstract

The passive track system comprises a passive track formed as a highly reflective strip adhered to the floor and containing a bar code, vehicle-supported passive track reading devices for forward and reverse travel as well as a bar code reading device. The passive track system can be operated as a passive track guidance system or as a passive track control system or both. The vehicle follows the passive track or guide path by continuously monitoring the travel lane on both sides of the central longitudinal axis of the vehicle using track sensors located in reading heads. In the method, sets of actual values thus measured are cross-correlated with a set of reference values corresponding to the track positions and stored in an electronic evaluation device. The appropriate cross-correlation function is calculated for each "observation" using a special track guidance algorithm and then a track position of the vehicle as well as a quality or system condition factor for the passive track system are derived. Control is also effected by the passive track. The vehicle decodes the bar code using code sensors and processes it as a control signal. The passive track is useful both as a control line for track guidance and as a signal source for functional control. Since the passive track is easily and quickly applicable to and removable from the floor, it renders possible a freely chosen layout of the travel network and thus an optimal utilization of the flexibility of trackless vehicles.

Claims

1. A passive track system for guiding and controlling on a traffic surface robotic transport and assembly vehicles each having a central longitudinal axis, comprising:

a passive track attached to said traffic surface and defining a guide line for said vehicles;

said passive track having a centerline;

said passive track having at least one differentiating characteristic in relation to said traffic surface;

a sensing device mounted at each of said vehicles for following said passive track;

a predetermined number of track sensors of said sensing device mounted at each of said vehicles for producing a set of actual value signals indicative of said at least one differentiating characteristic of said passive track for continuous track guidance of each said vehicle;

said predetermined number of track sensors being attached to the underside of each said vehicle in a transverse direction and substantially symmetrical to said central longitudinal vehicle axis and having a substantially uniform mutual spacing;

a predetermined number of track locations twice as great as said predetermined number of track sensors and having the same substantially uniform mutual spacing as said predetermined number of track sensors and symmetrically arranged with respect to said centerline of said passive track;

said predetermined number of track locations having a set of reference values associated therewith;

a control processor circuit supported on each of said vehicles and operatively connected with said predetermined number of track sensors for cross-correlating said set of actual value signals produced by said predetermined number of track sensors and said set of reference values associated with said predetermined number of track locations for deriving therefrom a vehicle position signal indicative of the transverse position of said vehicle relative to said passive track and a track condition signal indicative of the condition of said passive track;

a predetermined number of bar codes associated with said passive track;

an evaluation circuit supported on each of said vehicles;

a predetermined number of code sensors being attached to said underside of each said vehicle for cooperation with said predetermined number of bar codes; and

said predetermined number of code sensors being operatively connected with said evaluation circuit for generating, in response to each one of said predetermined number of bar codes, control signals controlling the operation of said vehicle.

2. The passive track system as defined in claim 1, wherein:

said passive track system has predetermined nominal data associated therewith; and

said set of reference values being correlated to said predetermined nominal data and having a mean value of zero.

3. The passive track system as defined in claim 1, further including:

said passive track containing travel zones;

an associated track condition signal being determined for each combination of said vehicles and said travel zones; and

said associated track condition signal being assigned by majority decision to a predetermined vehicle of said vehicles.

4. The passive track system as defined in claim 1, further including:

said passive track continuing travel zones;

an associated track condition signal being determined for each combination of said vehicles and said travel zones; and

said associated track condition signal being assigned by majority decision to a predetermined travel zone of said travel zones.

5. The passive track system as defined in claim 1, wherein:

said differentiating characteristic of said passive track comprises an optical coefficient of reflection of said passive track which is different from an optical coefficient of reflection of regions of said surface adjacent to said passive track.

6. The passive track system as defined in claim 5, wherein:

said passive track comprises a brush-painted passive track which has a greater coefficient of reflection than said regions of said surface adjacent to said passive track.

7. The passive track system as defined in claim 5, wherein:

said passive track comprises a spray-painted passive track which has a greater coefficient of reflection than said regions of said surface adjacent to said passive track.

8. The passive track system as defined in claim 5, wherein:

said passive track comprises an adherent reflective metallic tape which has a greater coefficient of reflection than said regions of said surface adjacent to said passive track.

9. The passive track system as defined in claim 5, wherein:

said passive track comprises an adhesive reflecting synthetic tape which has a greater coefficient of reflection than said regions of said surface adjacent to said passive track.

10. The passive track system as defined in claim 1, wherein:

said passive track has a predetermined width which is three times said uniform mutual spacing of said predetermined number of passive track sensors.

11. The passive track system as defined in claim 1, wherein:

said passive track is defined as discrete regions defining gaps therebetween; and

said vehicles including means for extrapolating said passive track in said gaps.

12. The passive track system as defined in claim 11, wherein:

said traffic surface is provided with a contrast-enhancing low reflective background finish.

13. The passive track system as defined in claim 11, wherein:

said predetermined number of bar codes are located in related ones of said gaps formed in said passive track.

14. The passive track system as defined in claim 1, wherein:

said passive track having a predetermined width;

said vehicles defining, during travel along said passive track, a maximum deviation of said vehicles in relation to said guide line; and

said predetermined number of bar codes having a width greater than said predetermined width of said passive track in order to account for said maximum vehicle deviation from said guide line.

15. The passive track system as defined in claim 14, wherein:

said traffic surface being provided with a contrast-enhancing low reflective background finish in the region of said predetermined number of bar codes.

16. The passive track system as defined in claim 1, wherein:

said predetermined number of bar codes are located in regions of said traffic surface adjacent to said passive track.

17. The passive track system as defined in claim 1, wherein:

said evaluation circuit operatively connected with said code sensors, is integrated into said control processor circuit.

18. The passive track system as defined in claim 1, wherein:

each one of said predetermined number of bar codes comprises a self-correcting code and is capable of tolerating lateral motion of up to 5 mm during the reading operation.

19. The passive track system as defined in claim 1, wherein:

said predetermined number of track sensors defines an integral optical unit; and

said integral optical unit comprising reading heads as components thereof for reading said passive track.

20. The passive track system as defined in claim 1, wherein:

said predetermined number of code sensors defines an integral optical unit; and

said integral optical unit comprising reading heads as components thereof for reading said bar code.

21. A passive track guidance and control system for a traffic surface for robotic vehicles, comprising:

a passive track attached to said traffic surface as a guide marker for guiding said robotic vehicles;

said traffic surface having at least one identifying characteristic;

said passive track having a centerline and exhibiting at least one identifying characteristic optically distinguishable from said at least one identifying characteristic of said traffic surface;

an optical sensing device mounted on each vehicle of said robotic vehicles for optically tracking said passive track;

each said vehicle having an underside and a central longitudinal axis;

said optical sensing device comprising a plurality of track sensors transversely arrayed in a predetermined spacing on said underside of each said vehicle;

said passive track comprising a number of track stripes in a predetermined relation to said plurality of track sensors;

said stripes being arrayed on said traffic surface;

a control processor mounted in each said vehicle for correlating a set of actual values sensed by said plurality of track sensors in response to said identifying characteristics of said number of track stripes of said passive track and adjacent regions of said traffic surface with a set of reference values associated with said track stripes and said adjacent passive track regions for deriving from said correlation a vehicle position signal indicative of the transverse position of said vehicle relative to said passive track and a track condition signal indicative of the optical condition of said passive track;

said passive track comprising discrete track marks defining track spaces therebetween;

said discrete track marks and said track spaces conjointly defining a bar code;

said optical sensing device further comprising a plurality of code sensors attached to said underside of said vehicle for cooperation with said bar code;

an evaluation circuit; and

said plurality of code sensors being operatively connected with said evaluation circuit for generating in response to said bar code, control signals controlling the operation of said vehicle.

22. A method of operating a passive track guidance and control system on a traffic surface for robotic vehicles, comprising the steps of:

employing an optical sensing device mounted on at least one vehicle of said robotic vehicles and comprising a plurality of track sensors to monitor, during travel of said at least one vehicle on said traffic surface, a passive track applied to said traffic surface;

directionally guiding said at least one vehicle in relation to information gained by said optical sensing device when monitoring said passive track;

employing a control processor mounted on said at least one vehicle to perform statistical correlation of said information gained by said optical sensing device with reference data relative to said passive track;

deriving from said statistical correlation an optical condition coefficient of said passive track;

employing said control processor to decode control information incorporated into said passive track in the form of a bar code; and

controlling operational functions of said vehicle in relation to said control information.

23. The method as defined in claim 22, wherein:

said step of employing a control processor to perform said statistical cross-correlation entails employing a discrete cross-correlation function having a maximum; and

employing a track guidance algorithm to complement said discrete cross-correlation function in the region of said maximum to obtain a continuous function.

24. The method as defined in claim 23, wherein:

said step of employing said track guidance algorithm entails employing an interpolation procedure to determine continuous function values between discrete function values.

25. A passive track system for guiding and controlling robotic transport and assembly vehicles on a traffic surface, said vehicles having a predetermined longitudinal axis, comprising:

a passive track located on said traffic surface and defining a guide line for said vehicles;

said passive track having a centerline;

said passive track further having at least one differentiating characteristic in relation to said traffic surface;

a predetermined number of bar code data associated with said passive track and located at defined places along said passive track;

a sensing device mounted on each of said vehicles for following said passive track;

said sensing device containing a predetermined number of track sensors being attached to the underside of each said vehicle in a transverse direction and substantially symmetrical to said longitudinal vehicle axis and having a substantially uniform mutual spacing;

each one of said track sensors being responsive to said differentiating characteristic of said passive track and generating a set of sensor signals representing a set of actual value signals indicative of the transverse position of said vehicle relative to said passive track;

an evaluation circuit connected to said track sensors for receiving said set of sensor signal;

said evaluation circuit storing a set of a predetermined number of reference values, which number is greater than said predetermined number of track sensors;

said reference values being related to a predetermined number of respective track locations symmetrically distributed with respect to said track centerline and having the same mutual distance as the track sensors;

said evaluation circuit containing a control processor circuit for statistically combining said set of actual value signals and said set of reference values for deriving therefrom at least one position signal indicative of the position of said longitudinal axis of each vehicle relative to said track centerline;

a reading device supported on each said vehicle and for detecting each one of said predetermined number of bar code informations; and

said reading device being connected to said evaluation circuit for generating control signals for controlling the operation of the vehicle.

26. The passive track system as defined in claim 25, wherein:

said predetermined number of reference values is twice as great as said predetermined number of track sensors; and

said control processor circuit carrying out, as said statistical combination, a cross-correlation between said track sensor generated actual value signals and said stored reference values