Automated dimensional inspection

• US 7,111,783 B2
• Filed: 06/25/2004
• Issued: 09/26/2006
• Est. Priority Date: 06/25/2004
• Status: Expired due to Fees

• Current Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Original Assignee: The Board of Trustees of Michigan State University (Michigan State University)
• Inventors: Shi, Quan, Heping, Chen, Xi, Ning
• Primary Examiner(s): Le, Thien M.
• Assistant Examiner(s): Haupt, Kristy A.
• Application Number:
  US10/877,083
• Publication Number:
  US 20050284937A1
• Time in Patent Office: 823 Days
• Field of Search: 235/437, 364/512, 700/184, 348/43, 356/614
• US Class Current: 235/437
• CPC Class Codes: G05B 19/4083 Adapting programme, configuration
• CPC Class Codes: G05B 2219/37205 Compare measured, vision data with computer model, cad data
• CPC Class Codes: G05B 2219/37441 Use nc machining program, cad data for measuring, inspection
• CPC Class Codes: Y02P 90/02 Total factory control, e.g. smart factories, flexible manufacturing systems [FMS] or integrated manufacturing systems [IMS]

Abstract

An automated dimensional inspection system is provided that modifies sensor planning based on real-time measurement feedback. The dimensional inspection system includes a sensor planner, an error map generator, and a sensor affixed to a movable member. The sensor planner is adapted to receive three dimensional design data for a workpiece to be measured and generate path data in part based on the dimensional design data for the workpiece, where the path data is indicative of a path for moving the sensor in relation to the surface of the workpiece. The error map generator is adapted to receive the dimensional design data and the three dimensional measurement data for the workpiece, and determine error data between the measurement data and the dimensional design data. Based on the error data, the sensor planner is able to further modify the path data for the sensor to increase the measurement accuracy.

Claims

1. An automated dimensional inspection system having a sensor for capturing image data, comprising:

a sensor planner adapted to receive three dimensional design data for a workpiece to be measured and operable to generate path data in part based on the dimensional design data for the workpiece from the sensor, where the path data is indicative of a path for moving the sensor in relation to the surface of the workpiece; and

an error map generator adapted to receive three dimensional measurement data for the workpiece from the sensor and the dimensional design data for the workpiece, the error model generator operable to determine error data between the measurement data and the dimensional design data;

the sensor planner further adapted to receive the error data from the error map generator and operable to modify the path data based in part on the error data.

2. The automated dimensional inspection system of claim 1 wherein the sensor is further defined as having a camera operable to capture image data representative of a portion of the surface of the workpiece and a projector operable to project a light pattern onto the surface of the workpiece.

3. The automated dimensional inspection system of claim 1 wherein the sensor is affixed to a movable member of a robot.

4. The automated dimensional inspection system of claim 1 wherein the sensor planner is adapted to receive performance parameters within which to perform an inspection operation and operable to generate the path data in part based on the performance parameters.

5. The automated dimensional inspection system of claim 1 wherein the sensor planner is adapted to receive attribute data for the sensor and operable to generate the path data in part based on the attribute data.

6. The automated dimensional inspection system of claim 1 wherein the sensor planner is adapted to receive task constraint data for an inspection operation and operable to generate the path data in part based on the task constraint data.

7. The automated dimensional inspection system of claim 1 wherein the sensor planner is operable to determine a plurality of viewpoints at which the sensor captures image data for at least a portion of the surface of the workpiece and translate the plurality of viewpoints into path data for the sensor.

8. The automated dimensional inspection system of claim 7 wherein the workpiece is modeled as a plurality of facets and the sensor planner is operable to identify facets indicative of a potential measurement error, where the identified facets are associated with a given viewpoint.

9. The automated dimensional inspection system of claim 8 wherein the sensor planner determines an angle between a vector projecting in a normal direction from a given facet being inspected and a vector representing an orientation of the sensor at the given viewpoint at which image data is captured for said facet.

10. The automated dimensional inspection system of claim 8 wherein sensor projects light onto the surface of the workpiece and evaluates intensity of captured image data to identify shadow areas on the surface of the workpiece.

11. The automated dimensional inspection system of claim 8 wherein the sensor planner compares the error data for a given facet to a predefined maximum error value.

12. The automated dimensional inspection system of claim 8 wherein the sensor planner is operable to evaluate the given viewpoint based on the identified facets and generate additional viewpoints when the given view point is deemed unacceptable.

13. The automated dimensional inspection system of claim 8 wherein the sensor planner further divides each of the identified facets into smaller facets prior to determining the additional view points.

14. The automated dimensional inspection system of claim 8 wherein the sensor planner evaluates the given viewpoint by calculating an average normal for the identified facets, determine an angle between the average normal and a normal for each of the identified facets, identifying a maximum angle from amongst the determined angles and compare the maximum angle to a predefined threshold angle.

15. The automated dimensional inspection system of claim 1 further comprises a height map generator adapted to receive image data representative of a portion of the surface of the workpiece and operable to generator three-dimensional measurement data for the workpiece, wherein the three-dimensional measurement data serves as an input to the error map generator.

16. The automated dimensional inspection system of claim 1 wherein the height map generator is operable to project a pattern of light having repeatable features onto a surface of a workpiece, correlating the repeatable features of the light pattern to a measure at which image data is captured, and determining a height measure for a given measurement point on the surface of the workpiece based in part on location of the measurement point in relation to the repeatable features of the light pattern.

17. An automated dimensional inspection system having a sensor for capturing image data, comprising:

a sensor planner adapted to receive three dimensional design data for a workpiece to be measured and operable to determine a plurality of viewpoints at which the sensor captures image data for at least a portion of the surface of the workpiece and translate the plurality of viewpoints into path data for the sensor, where the workpiece is modeled as a plurality of facets and the path data is indicative of a path for moving the sensor in relation to the surface of the workpiece; and

an error map generator adapted to receive three dimensional measurement data for the workpiece and the dimensional design data for the workpiece, the error model generator operable to determine error data between the measurement data and the dimensional design data;

the sensor planner further adapted to receive the error data from the error map generator and operable to identify facets indicative of a potential measurement error which are associated with a given viewpoint, evaluatethe given view point based on the identified facets and generate additional view points encompassing the identified facts, thereby modifying the path data.

18. An automated dimensional inspection system having a sensor for capturing image data, comprising:

a sensor planner adapted to receive three dimensional design data for a workpiece to be measured and operable to generate path data in part based on the dimensional design data for the workpiece, where the path data is indicative of a path for moving the sensor in relation to the surface of the workpiece;

a height map generator adapted to receive image data representative of a portion of the surface of the workpiece and operable to generator three-dimensional measurement data for the workpiece, wherein the three-dimensional measurement data serves as an input to the error map generator; and

an error map generator adapted to receive the three dimensional measurement data for the workpiece and the dimensional design data for the workpiece, the error model generator operable to determine error data between the measurement data and the dimensional design data;

the sensor planner further adapted to receive the error data from the error map generator and operable to modify the path data based in part on the error data.

19. The automated dimensional inspection system of claim 18 wherein the height map generator is operable to project a pattern of light having repeatable features onto a surface of a workpiece, correlating the repeatabie features of the light pattern to a measure at which image data is captured, and determining a height measure for a given measurement point on the surface of the workpiece based in part on location of the measurement point in relation to the repeatable features of the light pattern.

20. A method for determining height information of a workpiece using a non-contact sensor, comprising:

projecting a pattern of light having repeatable features onto a surface of the workpiece;

increasing frequency of the stripes in the light pattern and decreasing width of each strip in the light pattern until the width of each strip substantially correlates to a width dimension of a pixel in the imaging device;

correlating the repeatable features of the light pattern to a measure at which image data for the surface of the workpiece is captured; and

determining a height measure for a given measurement point on the surface of the workpiece based in part on location of the measurement point in relation to the light pattern.

21. The method of claim 20 further comprises using an imaging device having a plurality of pixels to capture image data, such that the repeatable features of the light pattern are correlated to dimensions of the pixels of the imaging device.

22. The method of claim 20 wherein the light pattern is further defined as a plurality of stripes projected by a light projector, such that each strip having a given width.

23. The method of claim 20 wherein the step of correlating the repeatable features further comprises projecting different light patterns on the surface of the workpiece and capturing image data indicative of the surface of the workpiece for each of the different light patterns using an imaging device.

24. The method of claim 20 further comprises projecting a pattern of light having a repeatable feature onto a reference plane oriented perpendicular to the light source projecting the light pattern, and correlating the repeatable features of the light pattern to a measure at which the image data is captured.

25. The method of claim 20 wherein the step of determining a height measure for a given measurement point further comprises determining a distance measure between two points on the reference plane, where a first point corresponds to the given measurement point projected along an image plane of the imaging device onto the reference plane and a second point corresponds to the given measurement point projected along a projection plane of the light pattern onto the reference plane.

26. The method of claim 25 wherein the distance measure is expressed as AC=AB+BC, where A is the first point, C is the second point and B is a point interposed between the first and second points at a location that corresponds to the location of the second point within a given strip, such that a distance measure for BC is determined by counting a number of strips between points B and C.

27. The method of claim 26 wherein a distance measure for AB is determined by counting a number of pixels between points A and B.

28. The method of claim 26 wherein the height measure is computed in accordance with

$h$

( x , y ) = L A ⁢

⁢

C ⁢

S d + L A ⁢

⁢

C

where, AC is the distance measure between the two points on the reference plane, S is the distance from the imaging device and the reference plane, and d is the distance between the light source and the imaging device.

29. A method for determining height information of a workpiece using a non-contact sensor, comprising:

projecting a pattern of light having a repeatable feature onto a reference plane oriented perpendicular to the light source projecting the light pattern;

correlating the repeatable features of the light pattern to a measure at which the image data is captured; and

determining a height measure for a given measurement point on the surface of the workpiece by determining a distance measure between two points on the reference plane, where a first point corresponds to the given measurement point projected along an image plane of the imaging device onto the reference plane and a second point corresponds to the given measurement point projected along a projection plane of the light pattern onto the reference plane.

30. The method of claim 29 wherein the distance measure is expressed as AC=AB+BC, where A is the first point, C is the second point and B is a point interposed between the first and second points at a location that corresponds to the location of the second point within a given strip, such that a distance measure for BC is determined by counting a number of strips between points B and C.

31. The method of claim 30 wherein a distance measure for AB is determined by counting a number of pixels between points A and B.

32. The method of claim 30 wherein the height measure is computed in accordance with

$h$

( x , y ) = L A ⁢

⁢

C ⁢

S d + L A ⁢

⁢

C

where, AC is the distance measure between the two points on the reference plane, S is the distance from the imaging device and the reference plane, and d is the distance between the light source and the imaging device.