Method and apparatus for determining the position of a body

• US 4,017,721 A
• Filed: 05/16/1974
• Issued: 04/12/1977
• Est. Priority Date: 05/16/1974
• Status: Expired due to Term

• Current Assignee: Roberts Sinto Corp. (Sintokogio Limited)
• Original Assignee: The Bendix Corporation (Honeywell International Inc.)
• Inventors: Michaud, Jimmie A.
• Primary Examiner(s): Ruggiero, Joseph F.
• Application Number:
  US05/470,345
• Time in Patent Office: 1,062 Days
• Field of Search: 235/151.3, 235/151.1, 235/151, 235/151.11, 178/6.8, 178/DIG. 1, 178/DIG. 22, 178/DIG. 36, 340/146.3 H, 356/165, 356/167, 356/168, 250/557, 250/567, 350/6, 198/257, 198/261, 198/262, 198/268, 214/1 CM
• US Class Current: 700/259
• CPC Class Codes: B25J 9/00 Programme-controlled manipulators
• CPC Class Codes: G01B 7/00 Measuring arrangements characterised by the use of electric or magnetic techniques
• CPC Class Codes: G01B 7/28 for measuring contours or curvatures
• CPC Class Codes: G01B 7/32 for measuring areas
• CPC Class Codes: G06F 18/21 Design or setup of recognition systems or techniques; Extraction of features in feature space; Blind source separation
• CPC Class Codes: G06T 1/0014 Image feed-back for automatic industrial control, e.g. robot with camera robots B25J19/023
• CPC Class Codes: G06T 7/74 involving reference images or patches
• CPC Class Codes: G06V 10/20 Image preprocessing
• CPC Class Codes: G06V 10/24 Aligning, centring, orientation detection or correction of the image
• CPC Class Codes: G06V 10/40 Extraction of image or video features
• CPC Class Codes: G06V 10/42 Global feature extraction by analysis of the whole pattern, e.g. using frequency domain transformations or autocorrelation
• CPC Class Codes: G06V 10/421 by analysing segments intersecting the pattern

Abstract

A system for generating electrical signals relating to the position and orientation of a part supported on a reference surface for use by manipulating devices includes an image converter tube which receives the light information from a test part and the surface. The scanned output of the tube is digitized and provided to a digital unit which isolates data representing the outline of the part in the direction of viewing. The system then calculates the centroid of the outlined area and a signature radius identifying the orientation of distinctive boundary transitions of the part relative to the centroid. Subsequently, similar parts supported on the reference surface are scanned by the video system and the digitized outputs are analyzed to calculate the position of the centroid of these parts relative to a reference location and the angular displacements of the parts relative to the rotational orientation of the test part.

Claims

1. A system for generating electrical signals representative of the position of a three-dimensional body relative to a supporting surface, comprising:

means for creating an optical image of the silhouette of said body in a first direction;

means for receiving the optical image and for generating electrical signals representative of the outline of the body;

means for receiving said electrical signals representative of the outline of the body and for generating electrical signals representative of the location of the centroid of the area of the object as viewed from said direction relative to the supporting surface; and

means for receiving said electrical signals representative of the outline of the body as viewed from said direction and for generating a signature signal said signature signal being representative of the positions relative to one another of a plurality of positions on the outline of the body, all of said positions having equal displacement from the controid of the body.

2. The system of claim 1 wherein said means for receiving said electrical signals representative of the outline of the body as viewed from said direction and for generating said signature signal includes means for generating a plurality of sets of electrical signals, each set containing signals representative of positions relative to one another of a plurality of positions on the outline of the body all having equal displacement from the centroid of the body, said sets differing from one another in the magnitude of said displacement, and means for selecting one of said sets as the signature signal.

3. The system of claim 2 wherein said means for selecting one of said sets of electrical signals representative of a position relative to one another of a plurality of positions on the outline of the body, all having equal displacement from the centroid of the body, includes means for segregating said sets of signals into bands of signals having closely related displacements from the centroid of the body and having a high degree of correlation with one another and selecting said signature signal from one of said bands.

4. A system for generating electrical signals representative of the position of a part relative to a reference position and to the rotational orientation of the part relative to that of a similar test part, comprising:

an image converter operative to receive radiation emanating from the part and the surface supporting the part and to generate electrical signals representative of the radiation values received;

means for receiving said electrical signals and for generating signals representative of the primary outline of the part relative to the supporting surface;

means for calculating the centroid of the area bounded by said primary outline and the position of the centroid relative to the reference position;

means for generating an electrical signal representative of the positions relative to one another of a group of selected points on the outline of the test part;

means for generating an electrical signal representative of the positions relative to one another of a number of similar points on the outline of the part; and

means for comparing the first and second electrical signals to determine the rotation of the part relative to the test part.

5. The system of claim 4 wherein said means for comparing the first and second electrical signals to determine the rotation of the subsequent part relative to the test part includes means for determining the correlation between the first and second electrical signals at various phase shifts relative to one another, and means for selecting the phase shift at which the first and second electrical signals have the highest degree of correlation.

6. The system of claim 4 wherein the group of selected points on the outline of the test part all have a common distance from the centroid of the test part and the similar points on the outline of the part all have a common distance from the centroid of the part.

7. The system of claim 4 wherein said image convertor scans the received radiation within a raster consisting of a series of parallel lines displaced from one another and said means for receiving the electrical signals and for generating signals representative of the primary outline of the part relative to the support surface includes means for determining the occurrence of threshold values of radiation intensity.

8. A system for generating electrical signals representative of the rotation of a subsequently analyzed part supported on a reference surface with respect to a previous test part positioned on the test surface, comprising:

means for generating electrical signals representative of the positions relative to one another of a plurality of positions on the outline of the test part;

means for generating a second electrical signal representative of the positions relative to one another of a plurality of similar points on a subsequent part;

said plurality of positions on the outline of the test part all having equal displacement from the centroid of the test part and said plurality of similar points on a subsequent part all having an equal displacement from the centroid of that subsequent part, and means for comparing said first and second signals to develop a third signal proportional to the phase shift between said first and second signals.

9. The system of claim 8 wherein said means for comparing said first and second signals to develop a third signal proportional to the phase shift between said first and second signals comprises means for cross-correlating said first and second signals at a plurality of phase shifts, one relative to the other, and means for determining the phase shift of the signal at which a maximum cross-correlation occurs.

10. The system of claim 8 wherein means for generating electrical signals representative of positions relative to one another of a plurality of positions on the outline of a test part includes an image convertor operative to receive radiation from said test part and said reference surface and means for analyzing the output of the image convertor to detect passage of the output signals across a threshold value.

11. The system of claim 8 wherein said reference surface is illuminated and said means for generating electrical signals receives radiation from said reference surface and from said part.

12. A system for optically inspecting a sample part and a plurality of similar run parts all supported on the same surface to determine the positions of the sample and run parts and the orientations of the run parts relative to the sample part, comprising:

optical means for generating signals representative of the outline of the sample and run parts;

means for operating on the signals representative of the sample part to determine the coordinates of the centroid of the sample part relative to an absolute position, and to generate a sample signature signal containing information representative of the intersection of a circle generated about the centroid of the sample part with the outline of the sample part;

means for analyzing the signals representative of the outline of a run part to determine the centroid of the run part;

means for generating a run signature signal representative of the locations of the intersections of a circle generated about the centroid of the run part with the outline of the run part; and

means for determining the phase shift of the sample signature signal relative to the run signature signal.

13. The system of claim 12 wherein said means for determining the phase shift of the run signature signal relative to the sample signature signal comprises a cross-correlator including means for generating the cross-correlation function of the sample signature signal and the run signature signal and for determining the location of the peak value of that function.

14. The system of claim 12 wherein the radius of the circle used to generate the sample and run signature signals is identical and is determined by generating a plurality of run signature signals at varying radii on the sample part and evaluating the information content of each of these signals.

15. The system of claim 12 wherein said optical means comprises an optical to electrical convertor device capable of determining the illumination value at one point in its field of view at an instant, and means for causing the field of view of the device to be scanned in a rectangular manner to generate electrical signals representative of the outline of the sample and run parts and in a circular manner to generate signals representative of the signatures of said sample and run parts.

16. The system of claim 15 including means for causing the optical to electrical convertor device to undergo a plurality of scans of its field along circles of varying radius about the point identified as the centroid of a sample part, and means for comparing the signals representative of the locations of the intersections of said circular scans with the outline of the sample part to control the selection of the scan radius used to generate the sample and run part signatures.

17. The system of claim 16 including means for classifying the signals representative of the intersections of a circular scan with the outline of the part in groups containing signals having a high degree of correlation relative to one another, and means for selecting as the signature radius the radius of an intermediate signal in one of said groups.

18. The system of claim 17 further including means for comparing the properties of said groups of signals, one with another, to determine the group having the properties most suitable for use in selection of the signature radius.