Control of tool/workpiece contact force with application to robotic deburring

Abstract

The design and implementation of a microprocessor-based system to control the interaction forces between a five-axis articulated robot and a workpiece is described. The control system worked in parallel with a robot controller by calculating position corrections that allowed forces to be controlled in the desired manner. These corrections were successfully interfaced to the controller's position control loop on an individual-axis level. Stable force-control algorithms were designed in spite of limitations imposed by flexibility in the robot drive train. For multi-degree-of-freedom force control, it is shown that each axis can be considered autonomous, obviating the need for a multivariable approach. Force control was implemented in both edge following and deburring experiments. In edge following, the commanded normal force ranged from 1 to 15 N, while the root mean square (rms) force errors remained constant. Errors increased from 0.5 to 1.5 N rms as tangential speed was increased from 1 to 9 cm s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . The performance of the force control system during deburring operations was characterized across the full force and speed range of the cutting tools used. The smoothness of cut was shown to be consistent with manual deburring operations in terms of optimal feed and metal removal rates.