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

Abstract

The design and implementation of a microprocessor based control system to control the interaction forces between a five axis articulated robot and a workpiece is described. The control system works in parallel with a robot controller by calculating position corrections that allow force to be controlled in the desired manner. The corrections were successfully interfaced to the 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. In the multi-degree of freedom control case it is shown that each axis can be considered autonomous, obviating the need for a multivariable approach. Control was implemented in edge following experiments. Across levels of commanded normal force ranging from 0 to 15 N, the RMS force errors remain constant. Errors increased from 0.5 N to 1.5 N RMS as tangential speed was increased from 0 to 9 cm/sec. The performance of the force control system during deburring operations is characterized across the full force and speed range of the cutting tools used. Smoothness of cut is shown to be consistent with standard deburring operations in terms of optimal feed and metal removal rates.