External system for robotic accuracy enhancement

• US 8,509,949 B2
• Filed: 03/23/2009
• Issued: 08/13/2013
• Est. Priority Date: 03/21/2008
• Status: Expired due to Fees

• Current Assignee: Variation Reduction Solutions, Inc.
• Original Assignee: Variation Reduction Solutions, Inc.
• Inventors: Bordyn, Brett Alan, Markey, Myles Daniel, Kleeman, Michael John
• Primary Examiner(s): Tran, Khoi
• Assistant Examiner(s): Nguyen, Bao Long T
• Application Number:
  US12/408,958
• Publication Number:
  US 20090240372A1
• Time in Patent Office: 1,604 Days
• Field of Search: None
• US Class Current: 700/254
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: G05B 2219/36439 Guide arm in path by slaving arm to projected path, beam riding
• CPC Class Codes: G05B 2219/40623 Track position of end effector by laser beam

Abstract

The inventive concept of the metrology system (the system) actively determines the 6 Degree of Freedom (6-DOF) pose of a motion device such as, but not limited to, an industrial robot employing an end of arm tool (EOAT). A concept of the system includes using laser pointing devices without any inherent ranging capability in conjunction with the EOAT-mounted targets to actively determine the pose of the EOAT at distinct work positions of at least one motion device.

Claims

1. A method of determining robotic accuracy enhancement for a plurality of robotic devices performing operations of parts, said method comprising the steps of;

positioning at least one robotic device having an end of arm tool (the EOAT) relative to at least one part with the EOAT adaptable for multiaxial movement relative to the robotic device and the at least one part;

positioning a calibration stand with a plurality of laser emitting devices and a plurality of active target plates being clamped and powered on the calibration stand and install a stop device onto the calibration stand;

move the plurality of the active target plates positioned on a slide device until the stop device contacts a photosensitive array of the active target thereby locking position of the slide device;

connecting a controller to the active target plates, the calibration stand, and the at least one robotic device;

installing a metrology system relative the at least one robotic device and the at least one part wherein the metrology system includes at least one of theodolites, photometric system, and laser tracking device to measure at least three benchmark positions of the calibration stand to report to the controller coordinate data of the calibration stand;

powering the laser devices on the calibration stand wherein the initial certification of the calibration stand through X and Y position of each laser beams emitting from the laser devices is predetermined in order to determine values of X and Y positions of each laser spot on a photosensitive array;

determining an array-to-calibration stand matrix relationship by processing an image from the photosensitive array from the center of each laser spots in pixel space of at least three points; and

measuring calibration stand coordinates through measurement of active targets placed on each dowel hole defined in the active target plates whereby three dimensional values are stored in the controller with the array-to-calibration stand matrix.

2. A method as set forth in claim 1, including the step of distributing the active target plates with the active targets around a cell where the calibration stand, the at least one robotic device, and the part are located to establish communication between the active target plates.

3. A method as set forth in claim 1, including the step of measuring and recording a world position of each of the active targets attached to the active target plates in a world coordinates system to generate identification code for each of the active targets.

4. A method as set forth in claim 1, including the step of assigning positioning the active targets of the part and transforming the laser spot coordinated to the world position as the center of the laser spot is calculated since the active target positions are measured and known in the world coordinates system.

5. A method as set forth in claim 1, including the steps of measuring at least three control points on the part in the world coordinates system to determine a part-to-world location.

6. A method as set forth in claim 1, including the step of determining the pose of the photosensitive array in the world coordination system and determining correlation between position of the active targets located around the cell, placed on the part and located on the at least one robotic device.

7. A method as set forth in claim 1, including the step of registering the metrology system in the world coordinates system.

8. A method as set forth in claim 1, including the step of placing a beacon in the work cell and certifying the beacon in the world coordinates system.

9. A system for robotic accuracy enhancement (the system) comprising:

a plurality of robotic devices adaptable for multi-axial movement with each of, said robotic devices including an arm having an end of arm tool (EOAT) presenting at least one axis for performing at least one operation on a workpiece;

a plurality of multi-axial devices projecting laser beams oriented relative to said robotic device;

a plurality of removable target elements connected to the EOAT of each said robotic device with each of said target elements being pre-certified in the EOAT coordinate frame, allowing said robotic devices to orient the EOAT relative to the workpiece before performing an operation on the workpiece as each of said target elements are illuminated by said multi-axial devices;

a controller is operably communicated with said target elements, said plurality of multi-axial devices, and said plurality of robotic devices for manipulating at least one of said multi-axial device to activate at least one target element to determine the 6-DOF (Degree of Freedom) pose of said robotic devices wherein said multi-axial devices for projecting lasers connected to the removable target element positioned on the EOAT adaptable to determine the pose of the EOAT at distinct work positions of at least one motion device without the use of any range detection hardware; and

wherein pre-certifying each of said target elements in the EOAT coordinates frame includes setting UP an external metrology system in the EOAT coordinate frame, measuring at least three target positions on the target element, and generates an active target-to-EOAT coordinate frame matrix based on a calibration file of the target element.

10. A system as set forth in claim 9, wherein each target element comprises a base formed from at least one of metallic and non-metallic materials and presents a plurality of openings defined therein.

11. A system as set forth in claim 9, wherein said base presents a plurality of removable nest elements attachable to the respective openings defined in said and a plurality of calibration targets magnetically supported by the respective nest elements.

12. A system as set forth in claim 9, wherein said base further includes a photosensitive array defined in the plate.