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Evaluation of 7-degree-of-freedom robotic arm precision and effects of calibration methods
Author(s): Arnon Hurwitz; Marshal Childers; Kristi Davis; Michael DiBlasi; Jim Dotterweich; Matt Kaplan; Chad Kessens; Trevor Rocks
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Paper Abstract

This paper presents results from an experiment performed at the Combat Capabilities Development Command, Army Research Laboratory, Autonomous Systems Division (ASD) on the precision of a 7-degree-of-freedom robotic manipulator used on the RoMan robotic platform. We quantified the imprecision in the arm end-effector final position after arm movements ranging over distances from 362 mm to 1300 mm. In theory, for open-loop grasping, one should be able to compute the final X-Y-Z position of the gripper using forward kinematics. In practice, uncertainty in the arm calibration induces uncertainty in the forward kinematics so that it is desirable to measure this imprecision after different arm calibrations. Forty-one runs were performed under different calibration regimes. Ground truth was provided by measuring arm motions with a Vicon motion capture system while the chassis of the platform remained stationary during the experiment. Using a digital protractor to align the arm joints to the ground plane for a “Level” type calibration, the average total offset of the gripper in 3D space was 19.6 mm with a maximum of about 30 mm. After a “Field” (i.e. Hand-Eye) calibration, which aligned fiducials on the joints, the average total offset came to 37.8 mm with a maximum of about 80 mm. Distance travelled by the arm was found to be uncorrelated with total offset. The experiment demonstrated that Total (X, Y, Z) Offset in the gripper final position is reduced significantly if the robot arm is first calibrated using a standard “Level” calibration. The “Field” calibration method results in a significant increase in Offset variation.

Paper Details

Date Published: 13 May 2019
PDF: 15 pages
Proc. SPIE 11021, Unmanned Systems Technology XXI, 110210E (13 May 2019); doi: 10.1117/12.2518630
Show Author Affiliations
Arnon Hurwitz, Army Research Lab. (United States)
Marshal Childers, Army Research Lab. (United States)
Kristi Davis, Army Research Lab. (United States)
Michael DiBlasi, General Dynamics Land Systems (United States)
Jim Dotterweich, Army Research Lab. (United States)
Matt Kaplan, Army Research Lab. (United States)
Chad Kessens, Army Research Lab. (United States)
Trevor Rocks, Army Research Lab. (United States)


Published in SPIE Proceedings Vol. 11021:
Unmanned Systems Technology XXI
Charles M. Shoemaker; Hoa G. Nguyen; Paul L. Muench, Editor(s)

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