Methods for Locating and Sensing the Position, Orientation, and Contour of A Work Object in A Robotic System

• US 20130211766A1
• Filed: 03/06/2013
• Published: 08/15/2013
• Est. Priority Date: 02/10/2012
• Status: Active Grant

• Current Assignee: Ascent Ventures, LLC
• Original Assignee: Ascent Ventures, LLC
• Inventors: Jackson, Todd, Rosenberg, Samuel
• Granted Patent: US 9,310,482 B2
• Time in Patent Office: Days
• US Class Current: 702/97
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01B 21/16 for measuring distance of clearance between spaced objects
• CPC Class Codes: G01S 15/06 Systems determining the position data of a target
• CPC Class Codes: Y10S 901/09 Closed loop, sensor feedback controls arm movement

Abstract

Methods and apparatus enable a robotic system to detect and determine the location, orientation, surface contours, and features of an object that are not otherwise accurately known in order to allow the robotic system to accurately place a pulse/echo layer thickness-gauge ultrasonic transducer gauge onto the surface of the object. The robotic system uses one or more distance measurement sensors to determine the position, orientation, local contour, and other features of the surface in relation to the robot. Another method calibrates an inaccurate distance sensor. Yet another method maintains overall system functionality in a system with multiple distance sensors in the event that one or more of the distance sensors fails. The robotic system may also determine when maintenance is required.

Claims

1. A method of locating a position and at least one additional feature of an object surface using at least one distance sensor positioned by a robot of a robotic system, the method comprising the steps of:

a) the robotic system iteratively translating the distance sensor of the robotic system along a sensor measurement axis of the distance sensor across a range of motion of the distance sensor along the sensor measurement axis and incrementally moving the distance sensor, until the object surface lies along the sensor measurement axis, and within a measurement range, of the distance sensor for the robotic system in a first position;

b) the robotic system obtaining a first distance measurement between the distance sensor and a first point on the object surface with the robotic system in the first position and storing the first distance measurement in a repository;

c) the robotic system collecting a plurality of first robot positional data for the robotic system in the first position from a robot position-determining mechanism of the robotic system and storing the first robot positional data in the repository;

d) the robotic system moving the distance sensor to a second position, obtaining a second distance measurement between the distance sensor and a second point adjacent the first point on the object surface with the robotic system in the second position, storing the second distance measurement in the repository, collecting a plurality of second robot positional data for the robotic system in the second position from the robot position-determining mechanism of the robotic system and storing the second robot positional data in the repository;

e) the robotic system moving the distance sensor to a third position, obtaining a third distance measurement between the distance sensor and a third point adjacent the first point and the second point on the object surface with the robotic system in the third position, storing the third distance measurement in the repository, collecting a plurality of third robot positional data for the robotic system in the third position from the robot position-determining mechanism of the robotic system and storing the third robot positional data in the repository;

f) the robotic system computing a first location in three-dimensional space for the first point on the object surface by using the first distance measurement and the first robot positional data, a second location in three-dimensional space for the second point on the object surface by using the second distance measurement and the second robot positional data, and a third location in three-dimensional space for the third point on the object surface by using the third distance measurement and the third robot positional data; and

g) the robotic system computing the at least one additional feature of the object surface using the first location, the second location, and the third location.

2. The method of claim 1, wherein in step a), the substep of incrementally moving the distance sensor comprises incrementally translating the distance sensor in a plane substantially perpendicular to the sensor measurement axis.

3. The method of claim 1, wherein:

in step d), the substep of moving the distance sensor to a second position comprises translating the distance sensor in the plane substantially perpendicular to the sensor measurement axis to the second position; and

in step e), the substep of moving the distance sensor to a third position comprises translating the distance sensor in the plane substantially perpendicular to the sensor measurement axis to the third position.

4. The method of claim 1, wherein in step a), the substep of incrementally moving the distance sensor comprises incrementally rotating the distance sensor with respect to the sensor measurement axis.

5. The method of claim 1, wherein:

in step d), the substep of moving the distance sensor to a second position comprises rotating the distance sensor with respect to the sensor measurement axis to the second position; and

in step e), the substep of moving the distance sensor to a third position comprises rotating the distance sensor with respect to the sensor measurement axis to the third position.

6. The method of claim 1, wherein the at least one additional feature comprises an orientation of the object surface.

7. The method of claim 6, wherein the object surface is a panel of an automotive body.

8. The method of claim 1, wherein the at least one additional feature comprises a contour of the object surface, and in step g), the robotic system computing the at least one additional feature comprises the robotic system interpolating the contour of the object surface by comparing the first location relative to the second location and the third location.

9. The method of claim 8, wherein the object surface is a panel of an automotive body and wherein the robotic system determines whether the contour is convex or concave.

10. The method of claim 1, wherein the at least one distance sensor comprises a first distance sensor, a second distance sensor, and a third distance sensor, the first distance sensor being located at the first position, the second distance sensor being located at the second position, and the third distance sensor being located at the third position simultaneously.

11. The method of claim 1 further comprising:

the robotic system moving the distance sensor to at least one additional position, obtaining at least one additional distance measurement between the distance sensor and at least one additional point adjacent the first point, the second point, and the third point on the object surface with the robotic system in the at least one additional position, storing the at least one additional distance measurement in the repository, collecting a plurality of at least one additional robot positional data for the robotic system in the at least one additional position from the robot position-determining mechanism of the robotic system and storing the at least one additional robot positional data in the repository; and

the robotic system computing at least one additional location in three-dimensional space for the at least one additional point on the object surface by using the at least one additional distance measurement and at least one additional robot positional data.

12. A method of locating a position and at least one additional feature of an object surface using at least one distance sensor positioned by a robot of a robotic system, the method comprising the steps of:

a) the robotic system iteratively translating the distance sensor of the robotic system along a sensor measurement axis of the distance sensor across a range of motion of the distance sensor along the sensor measurement axis and incrementally moving the distance sensor, until the object surface lies along the sensor measurement axis, and within a measurement range, of the distance sensor for the robotic system in a first position;

b) the robotic system obtaining a first distance measurement between the distance sensor and a first point on the object surface with the robotic system in the first position and storing the first distance measurement in a repository;

c) the robotic system collecting a plurality of first robot positional data for the robotic system in the first position from a robot position-determining mechanism of the robotic system and storing the first robot positional data in the repository;

d) the robotic system computing a first location in three-dimensional Cartesian space for the first point on the object surface by using the first distance measurement and the first robot positional data;

e) the robotic system incrementally adjusting the distance sensor to a plurality of additional positions along a path, the robotic system repeating steps b) through

d) for each additional position;

f) the robotic system plotting the additional positions as Cartesian Z-axis values along the path; and

g) the robotic system analyzing the Cartesian Z-axis values to locate any inflection points, maxima, minima, and discontinuities as additional features of the object surface.

13. The method of claim 12, wherein the path is a line, and in step e), the substep of the robotic system incrementally adjusting the distance sensor comprises the robotic system incrementally translating the distance sensor in the plane substantially perpendicular to the sensor measurement axis.

14. The method of claim 12, wherein the path is an arc, and in step e) the substep of the robotic system incrementally adjusting the distance sensor comprises the robotic system incrementally rotating the distance sensor with respect to the sensor measurement axis.

15. The method of claim 12, wherein the object surface is a flange for an automotive windshield.

16. The method of claim 12, wherein the at least one distance sensor comprises a plurality of distance sensors, the distance sensors being simultaneously located at the positions.

17. A method of verifying an accuracy of a distance sensor controlled by a robot in a robotic system, the method comprising the steps of:

a) the robotic system locating a test surface using the distance sensor;

b) the robotic system moving the distance sensor along a measurement axis of the distance sensor, until the test surface lies along the sensor measurement axis, and within a measurement range, of the distance sensor for the robotic system in a first position;

c) the robotic system measuring a first distance to the test surface using the distance sensor with the distance sensor at the first position and collecting a plurality of first robot positional data for the distance sensor in the first position from a robot position-determining mechanism of the robotic system and storing the first distance and the first robot positional data in a repository;

d) the robotic system repeating steps b) and c) for a plurality of additional positions within the measurement range of the distance sensor; and

e) the robotic system comparing a measured change in distances by the distance sensor between at least one pair of the positions of the distance sensor and a calculated change in distances based on the positional data for the at least one pair of the positions to determine whether a difference between the measured change and the calculated change is within a predetermined tolerance for the distance sensor.

18. The method of claim 17, wherein step b) comprises the substeps of the robotic system transmitting a primary ultrasonic signal from the distance sensor to the test surface, receiving a reflected ultrasonic signal reflected from the test surface back to the distance sensor, and calculating the distance based on a time difference between when the primary ultrasonic signal was sent and when the reflected ultrasonic signal was received.

19. A method of verifying an accuracy of a plurality of distance sensors controlled by a robot in a robotic system, the method comprising the steps of:

a) the robotic system moving a first distance sensor of the plurality of distance sensors along a measurement axis of the first distance sensor, until the test surface lies along the sensor measurement axis, and within a measurement range, of the first distance sensor in a first position;

b) the robotic system obtaining a first distance measurement between the first distance sensor and test surface and collecting a plurality of first robot positional data for the first distance sensor in the first position from a robot position-determining mechanism of the robotic system and storing the first distance and the first robot positional data in a repository;

c) the robotic system sequentially moving each additional distance sensor of the plurality of distance sensors to the first position using the first robot positional data and measuring additional distances to the test surface using each additional distance sensor with each additional distance sensor at the first position and storing the additional distance measurements in the repository; and

d) the robotic system comparing the first distance and each additional distance to determine whether a difference between the first distance and each additional distance is within a predetermined tolerance for the plurality of distance sensors.

20. The method of claim 19, wherein step b) comprises the substeps of the robotic system transmitting a primary ultrasonic signal from the first distance sensor to the test surface, receiving a reflected ultrasonic signal reflected from the test surface back to the first distance sensor, and calculating the first distance based on a time difference between when the primary ultrasonic signal was sent and when the reflected ultrasonic signal was received.

21. A method of autonomously calibrating a plurality of distances sensors controlled by a robot in a robotic system, the method comprising the substeps of:

a) the robotic system sequentially moving each of the plurality of distance sensors to a previously-programmed first reference position lying in front of a fixed reference surface;

b) the robotic system sequentially activating a first distance sensor calibration signal to calibrate a first distance sensor range limit for each of the plurality of distance sensors;

c) the robotic system sequentially moving each of the plurality of distance sensors to a previously-programmed second reference position lying in front of the fixed reference surface; and

d) the robotic system activating a second distance sensor calibration signal to calibrate a second distance sensor range limit for each of the plurality of distance sensors.

22. A method of autonomously compensating for an out-of-calibration or failed distance sensor in a robotic system comprising at least two distance sensors comprising the out-of-calibration or failed distance sensor and a functioning distance sensor, the method comprising the substeps of:

a) the robotic system substituting the out-of-calibration or failed distance sensor by moving the functioning distance sensor to occupy measurement positions that would have been occupied by the out-of-calibration or failed distance sensor;

b) the robotic system obtaining distance measurements from the functioning distance sensor and storing the distance measurements in a repository; and

c) the robotic system utilizing the distance measurements from the functioning distance sensor in place of other measurements that would have been obtained from the out-of-calibration or failed distance sensor.