Mobile vehicle controller utilization of delayed absolute position data for guidance and navigation

• US 4,754,402 A
• Filed: 08/30/1985
• Issued: 06/28/1988
• Est. Priority Date: 08/30/1985
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Wand, Martin A.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US06/771,432
• Time in Patent Office: 1,033 Days
• Field of Search: 364/424, 364/444, 364/449, 364/450, 364/460, 364/513, 180/167-169, 358/103, 358/108
• US Class Current: 701/28
• 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 1/028 using a RF signal
• CPC Class Codes: G05D 2201/0216 Vehicle for transporting goods in a warehouse, factory or similar

Abstract

A mobile vehicle controller for controlling a mobile apparatus that travels along a commanded path. The mobile vehicle controller has a dead reckoning navigation procedure for navigating the controllable mobile apparatus along the commanded path in response to positions data. The mobile apparatus determines its position and provides the position data. A vision system provides the absolute position to the mobile apparatus. The dead reckoning position data is periodically modifying with the absolute position. The dead reckoning procedure is synchronized with the vision system.

Claims

1. A mobile vehicle controller for controlling a mobile apparatus that travels along a commanded path, the mobile vehicle controller comprising:

navigation means for navigating the mobile apparatus along the commanded path in response to factory floor coordinate system X-Y position data;

position means for determining by dead reckoning the factory floor coordinate system X-Y position of the mobile apparatus and to provide the factory floor coordinate system X-Y position data to the navigation means;

absolute means for determining the factory floor coordinate system X-Y absolute position of the mobile apparatus and to provide factory floor coordinate system X-Y absolute position data;

correction means for periodically modifying the factory floor coordinate system X-Y position data with the X-Y absolute position data to correct for accumulated inaccuracies in the factory floor coordinate system X-Y position data; and

synchronization means for synchronizing the position means with the absolute means.

2. The mobile vehicle controller according to claim 1 wherein the navigation means comprises:

a plurality of wheels for providing mobility to the mobile apparatus;

means for rotating the plurality of wheels at a controllable speed of rotation;

means for controlling the trajectory of the mobile apparatus by varying the angle of the direction of rotation that predetermined members of the plurality of wheels make with the mobile apparatus; and

means for controlling the speed of rotation of the plurality of wheels.

3. The mobile vehicle controller according to claim 2 wherein the position means comprises:

means for determining the distance traversed from the number of rotations of the plurality of wheels; and

means for determining the direction traveled from the angle of the direction of rotation of the plurality of wheels.

4. The mobile vehicle controller according to claim 3 wherein the absolute means comprises:

means for comparing the position data with the absolute position data and to modify the position data by the results of the comparison.

5. The mobile vehicle controller according to claim 1 wherein the absolute means comprises:

visual navigation means for obtaining the location of the mobile apparatus in definable coordinates; and

communication means for communicating the definable coordinates to the mobile apparatus.

6. The mobile vehicle controller according to claim 5 wherein the synchronization means comprises:

time means for time stamping the definable coordinates to identify the time at which the mobile apparatus was at the definable coordinates;

time offset means for determining the time offset between the time stamp and the time the correction means modifies the position data and to additionally modify the position data according to the position difference that results from movement of the mobile apparatus during the time offset.

7. The mobile vehicle controller according to claim 5 where the visual navigation means comprises:

means for obtaining an image of the mobile apparatus;

means for converting the image to spatial position;

means for generating absolute position data from the spatial position.

8. The mobile vehicle controller according to claim 7 wherein the means for obtaining an image of the mobile apparatus comprises:

means for providing a predefined pattern of lighted points associated with the mobile apparatus, the lighted points being separated from one another by predefined distances; and

imaging means for obtaining an image of the lighted points.

9. The mobile vehicle controller according to claim 8 wherein the imaging means comprises:

a raster scan camera means for converting light from the lighted points to an electrical signal that represents light intensity in relationship to raster scan position of the raster scan camera means, the raster scan position being identified by frame, row and column coordinates, the raster scan camera means having a spatial plumbed point.

10. The mobile vehicle controller according to claim 9 further comprises:

means for transforming the electrical signal from an analog signal to a digital signal.

11. The mobile vehicle controller according to claim 10 wherein the transformation means comprises:

means for identifying clusters of pixels of light from the electrical signal and providing coordinates of the clusters of pixels of light thereby; and

means for transforming the clusters of pixels representing light intensity into centroids having identifiable coordinates.

12. The mobile vehicle controller according to claim 11 wherein the transformation means comprises:

means for digitizing the electrical signal to obtain a first digital signal;

means for dividing the first digital signal into a row digital signal and a column digital signal that correspond to the raster coordinates;

summation means for performing vector summations of the row and column digital signals to obtain first and second integrated signals respectively; and

comparator means for comparing the first and second integrated signals to a predefined threshold to obtain a first ordinate signal and second ordinate signal thereby.

13. A method for controlling a mobile apparatus that travels along a commanded path, the method comprising:

navigating the mobile apparatus along the commanded path in response to factory floor coordinate system X-Y position data;

determining by dead reckoning the factory floor coordinate system X-Y position of the mobile apparatus and to provide the factory floor coordinate system X-Y position data;

determining the factory floor coordinate system X-Y absolute position of the mobile apparatus and providing factory floor coordinate system X-Y absolute position data;

periodically modifying the factory floor coordinate system X-Y position data with the factory floor coordinate system X-Y absolute position data to correct for accumulated inaccuracies in the factory floor coordinate system X-Y position data; and

synchronizing the position step with the absolute step.

14. The method according to claim 13 wherein the navigation step comprises:

providing mobility to the mobile apparatus with a plurality of wheels;

rotating the plurality of wheels at a controllable speed of rotation;

controlling the trajectory of the mobile by varying the angle of the direction of rotation that predetermined members of the plurality of wheels make with the mobile apparatus; and

controlling the speed of rotation of the plurality of wheels.

15. The method according to claim 14 wherein the step of determing the position comprises:

determining the distance traversed from the number of rotations of the plurality of wheels; and

determining the direction traveled from the angle of the direction of rotation of the plurality of wheels.

16. The method according to claim 15 wherein the step of determing the absolute position comprises:

comparing the position data with the absolute position data and to modify the position data by the results of the comparison.

17. The method according to claim 16 wherein the step of determing the absolute position comprises:

obtaining the location of the mobile apparatus in definable coordinates; and

communicating the definable coordinates to the mobile apparatus.

18. The method according to claim 17 wherein the synchronizing step comprises:

time stamping the definable coordinates to identify the time at which the mobile apparatus was at the definable coordinates;

determining the time offset between the time stamp and the time the correction step modifies the position data and to additionally modify the position data according to the position difference that results from movement of the mobile apparatus during the time offset.

19. The method according to claim 18 wherein the step of obtaining the location comprises:

obtaining an image of the mobile apparatus;

converting the image to spatial position;

generating absolute position data from the spatial position.

20. The method according to claim 19 wherein the step of obtaining an image of the mobile apparatus comprises:

providing a predefined pattern of lighted points associated with the mobile appratus, with the lighted points being separated from one another by predefined distances; and

obtaining an image of the lighted points.

21. The method according to claim 20 the step of obtaining an image of the lighted points comprises the steps of:

identifying clusters of light that represent the lighted points which includes the step of;

converting light with a raster scan camera from the lighted points to an electrical signal that represents light intensity in relationship to raster scan position of the raster scan camera, the raster scan position being identified by frame, row and column coordinates, the raster scan camera having a spatial plumb point.

22. The method according to claim 21 wherein the step of identifying clusters of light comprises the step of:

transforming the electrical signal from an analog signal to a digital signal.

23. The method according to claim 22 wherein the step of transforming comprises the steps of:

identifying clusters of pixels of light from the electrical signal and providing coordinates of the clusters of pixels of light thereby; and

transforming the clusters of pixels representing light intensity into centroids having identifiable coordinates.

24. The method according to claim 23 wherein the step of transforming comprises:

digitizing the electrical signal to obtain a first digital signal;

dividing the first digital signal into a row digital signal and a column digital signal that corresponds to the raster coordinates;

performing vector summations of the row and column digital signals to obtain first and second integrated signals respectively; and

comparing the first and second integrated signals to a predefined threshold to obtain a first ordinate signal and second ordinate signal thereby.

25. The method according to claim 24 wherein the identifying step comprises:

locating centroids with a window that represents the clusters of light, the window being bounded by the first and second ordinates; and

comparing a pattern created by the centroids to the predefined pattern of the lighted points.

26. The method system according to claim 25 wherein the step of comparing a pattern comprises:

obtaining chordal lengths between the centroids;

comparing the chordal lengths to the predefined distances; and

determining from the comparisons of the chordal lengths to the predefined distances, whether the centroids represent the lighted points on the mobile apparatus.

27. The method according to claim 26 wherein the predefined pattern is a triangle and the step of determining if the centroids represent the cluster of lighted points comprises the steps of:

identifying a chordal length having the same length as the predefined distance that represents the length of the hypotenuse of the triangle;

ordering the chordal lengths in a first direction from the identified chordal length;

determining if the order of chordal lengths are ordered so as to have a length that has a predefined relationship to the lengths of the adjoining chordal lengths;

obtaining the angle between the chordal lengths; and

comparing the angles between the chordal lengths to the angles of the triangle.

28. The method according to claim 27 further comprising the steps of:

summing the chordal lengths; and

comparing the summation of the chordal lengths to the length of the perimeter of the triangle.