Method for Controlling Location of End Effector of Robot Using Location Alignment Feedback

• US 20180361595A1
• Filed: 06/14/2017
• Published: 12/20/2018
• Est. Priority Date: 06/14/2017
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Troy, James J., Georgeson, Gary E., Lea, Scott W., Wright, Daniel James
• Granted Patent: US 10,625,427 B2
• Time in Patent Office: Days
• CPC Class Codes: B25J 11/00 Manipulators not otherwise provided for
• CPC Class Codes: B25J 13/088 with position, velocity or acceleration sensors
• CPC Class Codes: B25J 19/023 including video camera means
• CPC Class Codes: B25J 9/162 Mobile manipulator, movable base with manipulator arm mounted on it
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: B25J 9/1694 characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion
• CPC Class Codes: G01B 11/002 for measuring two or more coordinates
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01J 5/04 Casings
• CPC Class Codes: G01J 5/48 Thermography; Techniques using wholly visual means
• CPC Class Codes: G01N 25/72 Investigating presence of flaws
• CPC Class Codes: G05B 2219/39024 Calibration of manipulator
• CPC Class Codes: G05B 2219/40298 Manipulator on vehicle, wheels, mobile
• CPC Class Codes: G05B 2219/45066 Inspection robot
• CPC Class Codes: G05B 2219/45071 Aircraft, airplane, ship cleaning manipulator, paint stripping
• CPC Class Codes: Y10S 901/01 Mobile robot
• CPC Class Codes: Y10S 901/44 inspection

Abstract

Systems and methods for automating robotic end effector alignment using real-time data from multiple distance sensors to control relative translational and rotational motion. In accordance with one embodiment, the alignment process involves computation of offset distance and rotational angles to guide a robotic end effector to a desired location relative to a target object. The relative alignment process enables the development of robotic motion path planning applications that minimize on-line and off-line motion path script creation, resulting in an easier-to-use robotic application. A relative alignment process with an independent (off-board) method for target object coordinate system registration can be used. One example implementation uses a finite-state machine configuration to control a holonomic motion robotic platform with rotational end effector used for grid-based scan acquisition for non-destructive inspection.

Claims

1. A method for controlling a location of an end effector of a robotic mobile platform relative to a target object, comprising:

moving the end effector to a first location; and

enabling a robot controller to execute operations specified by a finite-state machine control application, which operations comprise;

acquiring distance data from first, second and third distance sensors mounted to the end effector while the end effector is at the first location, wherein the acquired distance data represents respective distances separating the first, second and third distance sensors from respective areas on a surface of the target object; and

moving the end effector from the first location to a first grid location by aligning the end effector with the target object using the distance data.

2. The method as recited in claim 1, wherein the aligning comprises rotating the end effector so that an axis of the end effector is perpendicular to the surface of the target object.

3. The method as recited in claim 2, wherein the rotating the end effector comprises rotating the end effector about a pitch axis.

4. The method as recited in claim 3, further comprising rotating a base of the robotic mobile platform about a yaw axis.

5. The method as recited in claim 2, wherein the aligning further comprises displacing the end effector so that the end effector is separated from the surface of the target object by a goal offset distance.

6. The method as recited in claim 1, wherein the aligning comprises displacing the end effector so that the end effector is separated from the surface of the target object by a goal offset distance.

7. The method as recited in claim 1, further comprising calculating coordinates of a location of an external tracking system in a coordinate system of the target object.

8. The method as recited in claim 7, further comprising aiming a laser beam produced by the external tracking system at a specified coordinate position on the surface of the target, thereby forming a laser spot, wherein moving the end effector to the first location comprises driving the robotic mobile platform to align laser spots produced by the first, second and third distance meters around the laser spot produced by the external tracking system.

9. The method as recited in claim 7, further comprising calculating coordinates of a visible feature on a tool mounted to the end effector in the coordinate system of the target object using the external tracking system while the end effector is at the first grid location.

10. The method as recited in claim 1, wherein the operations specified by the finite-state machine control application further comprise:

activating a tool mounted to the end effector while the end effector is at the first grid location;

moving the end effector from the first grid location to a second location using the finite-state machine control application;

moving the end effector from the second location to a second grid location by aligning the end effector with the target object using the finite-state machine control application; and

activating the tool while the end effector is at the second grid location.

11. The method as recited in claim 10, wherein the tool is an infrared thermography scanner and the operations specified by the finite-state machine control application further comprise:

acquiring a first infrared thermography scan while the end effector is at the first grid location; and

acquiring a second infrared thermography scan while the end effector is at the second grid location.

12. The method as recited in claim 11, further comprising stitching together the first and second infrared thermography scans.

13. A robotic mobile platform comprising:

a self-propellable mobile base platform comprising a plurality of rolling elements and a plurality of motors respectively coupled to said plurality of rolling elements;

a vertically extendible mast carried by the base platform;

an arm having a proximal end fixedly coupled to the vertically extendible mast;

an end effector pivotably coupled to a distal end of the arm;

a non-transitory tangible computer-readable storage medium in which a finite-state machine control application is stored;

first, second and third distance sensors mounted to the end effector and configured to acquire distance data representing respective distances separating the first, second and third distance sensors from respective areas on a surface of a target object; and

a controller configured to control operation of the first, second and third distance sensors and move the end effector relative to ground in accordance with commands generated by the finite-state machine control application, wherein the finite-state machine control application comprises methods to generate instructions executable by the controller for moving the end effector using the distance data acquired by the first, second and third distance sensors.

14. The robotic mobile platform as recited in claim 13, wherein the first, second and third distance sensors are laser range meters.

15. The robotic mobile platform as recited in claim 14, further comprising a tool mounted to the end effector.

16. The robotic mobile platform as recited in claim 15, wherein the tool is an infrared thermography scanner.

17. The robotic mobile platform as recited in claim 16, wherein the infrared thermography scanner comprises a shroud.

18. The robotic mobile platform as recited in claim 13, wherein the controller is further configured to move the end effector from a first location to a second location by aligning the end effector with the target object using the finite-state machine control application, wherein the aligning comprises rotating the end effector so that an axis of the end effector is perpendicular to the surface of the target object.

19. The robotic mobile platform as recited in claim 18, wherein the aligning further comprises displacing the end effector so that the end effector is separated from the surface of the target object by a goal offset distance.

20. A method for controlling the location of an end effector of a robotic mobile platform relative to a target object, comprising enabling a robot controller to execute operations specified by a finite-state machine control application, which operations comprise:

(a) moving the end effector to a nominal location not in contact with a surface of the target object in accordance with pre-stored grid pattern data representing a grid pattern;

(b) acquiring distance data from first, second and third distance sensors mounted to the end effector while the end effector is at the unaligned location, wherein the acquired distance data represents respective distances separating the first, second and third distance sensors from respective areas on the surface of the target object;

(c) moving the end effector from the nominal location to an aligned location by aligning the end effector with the target object using the distance data;

(d) activating a tool mounted to the end effector while the end effector is at the aligned location; and

(e) repeating steps (a) through (d) for each one of a multiplicity of aligned locations of the grid pattern.

21. The method as recited in claim 20, wherein the aligning comprises rotating the end effector so that an axis of the end effector is perpendicular to the surface of the target object and displacing the end effector so that the end effector is separated from the surface of the target object by a goal offset distance.

22. The method as recited in claim 20, wherein the tool is an infrared thermography scanner and the operations specified by the finite-state machine control application further comprise acquiring a respective infrared thermography scan while the end effector is at each aligned location, further comprising stitching together the infrared thermography scans.