Adaptive control of robot manipulators with anti-backlash gears

Abstract

This paper proposes a control method for robot manipulators that have anti-backlash gears in the joints. The anti-backlash gear is modeled as a three segment flexible joint characteristic. A controller consists of a PD feedback part and a full dynamics feedforward part. This control method employs the sliding control scheme. In order to make the tip of the manipulator track desired trajectories and to eliminate steady state errors, this method utilizes two sliding surfaces for both links and actuators. For this purpose, positions and velocities of both links and actuators are fedback. An anti-backlash inverse characteristic is introduced to obtain the desired trajectories for the actuators from the desired trajectories of the links. An adaptation scheme to the variation of payloads is also investigated.