Method and apparatus for filtering reflections from direct images for mobile robot navigation

• US 4,789,940 A
• Filed: 08/30/1985
• Issued: 12/06/1988
• Est. Priority Date: 08/30/1985
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Christian, Donald J.
• Primary Examiner(s): Smith, Jerry
• Assistant Examiner(s): MacDonald, Allen
• Application Number:
  US06/771,380
• Time in Patent Office: 1,194 Days
• Field of Search: 364/513, 364/424, 364/468, 358/101, 358/103, 250/221, 250/222.1, 250/578, 901/1, 901/46, 901/47
• US Class Current: 700/113
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70
• 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: Y10S 706/904 Manufacturing or machine, e.g. agricultural machinery, machine tool

Abstract

A visual navigation system that rejects reflected images navigates an electrical controllable apparatus such as a mobile robot. The mobile robot is fitted with a minimum of three navigation beacons which emit a light visible to overhead television cameras. The beacons area arranged so as to form a triangle. The shape and the dimension of the triangular pattern are measured and stored in a memory unit within the visual navigation system, and when a reflected image is received it will be characterized by a different angle and thus the vision navigation system is able to distinguish the reflected image from the primary image of the mobile robot.

Claims

1. A visual navigation system with a reflection filter for obtaining a spatial position of a manufacturing apparatus, comprising:

means for obtaining a visual image of the manufacturing apparatus;

means for filtering of images of the manufacturing apparatus reflected from surfaces in view of the manufacturing apparatus, to obtain a true image thereby; and

means for obtaining the spatial position of the manufacturing apparatus from the true image thereof.

2. The visual navigation system according to claim 1 wherein the means for obtaining a visual image of the manufacturing apparatus comprises:

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

imaging means for obtaining an image of the lighted points.

3. The visual navigation system according to claim 2 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 plumb point.

4. The visual navigation system according to claim 3 including an identifying means comprising:

means for transforming the electrical signal from an analog signal in the temporal domain to a digital signal in the spatial domain.

5. The visual navigation system according to claim 4 wherein 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;

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

6. The visual navigation system according to claim 5 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 a vector summation of the row and column digital signals to obtain a first and second integrated signal; and

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

7. The visual navigation system according to claim 6 wherein further comprising;

means for locating centroids that represent the clusters of pixels of light from t eh first and second ordinates; and

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

8. The visual navigation system according to claim 7 wherein the means for comparing a pattern comprises:

means for obtaining chordal lengths between the centroids;

length means for comparing the chordal lengths to the predetermined distances; and

means for determining if the centriods represent the cluster of lighted points from the chordal lengths.

9. The visual navigation system according to claim 8 wherein the predefined pattern is a triangle and the means determining if the centroids represent the cluster of lighted points comprises:

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

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

means for 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;

means for obtaining the angle between the chordal lengths; and

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

10. The visual navigation system according to claim 9 further comprising:

means for summing the chordal lengths; and

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

11. The visual navigation system according to claim 8 wherein the means for filtering of reflected images comprises:

means for obtaining the distance from each centroid to the spatial plumbed point to obtain plumb distances thereby;

sort means for sorting the plumb distances into a plurality of distances having increasing order;

second means for comparing the centriods having the shortest plumb distances and identifying a group of centroids that have the shortest plumb distances and have a pattern that closely match a pattern in the predefined pattern of lighted points.

12. A method for obtaining a spatial position of a manufacturing apparatus, comprising:

obtaining a visual image of the manufacturing apparatus;

filtering of images of the manufacturing apparatus reflected from surfaces in view of the manufacturing apparatus, to obtain a true image thereby; and

obtaining the spatial position of the manufacturing apparatus from the true image thereof.

13. The method according to claim 12 wherein the step of obtaining an image of the manufacturing apparatus comprises:

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

obtaining an image of the lighted points.

14. The method according to claim 13 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.

15. The method according to claim 14 wherein the step of identifying clusters of light comprises the step of:

transforming the electrical signal from an analog signal in the temporal domain to digital signal in the spatial domain.

16. The method according to claim 15 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.

17. The method according to claim 16 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 correspond to the raster coordinates;

performing a vector summation of the row and column digital signals to obtain a first and second integrated signal; and

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

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

locating centroids that represent the clusters of light from the first and second ordinates; and

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

19. The method system according to claim 18 wherein the step of comparing a pattern comprises:

obtaining chordal lengths between the centroids;

comparing the chordal lengths to the predetermined distances; and

determining if the centroids represent the cluster of lighted points from the chordal lengths.

20. The method according to claim 19 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.

21. The method according to claim 20 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.

22. The method according to claim 18 wherein the step of filtering of reflected images comprises:

obtaining the distance from ech centroid to the spatial plumb point to obtain plumb distances thereby;

sorting the plumb distances into a plurality of distances having increasing order;

comparing the centriods having the shortest plumb distssances and identifying a group of centroids that have the shortest plumb distances and that closely match the predefined pattern of lighted points