Contact force control using backlash model for shaft torsion torque estimation of articulated robots with double encoder motor

Abstract

The purpose of this paper is to design a contact force controller for a 2-DOF parallel robot driven by a permanent magnet synchronous motor with a reduction gear. A low-rigidity coupling was inserted between the motor output shaft and the linkage, and the motor side angle and the load side angle could be measured by an encoder. A comparison method that did not use backlash to estimate the shaft torsional torque resulted in a contact force tracking error of about 0.5 N. The backlash model was then used to estimate the contact force tracking error. Simulation results showed that the backlash model reduced the tracking error to less than 0.1 N.