A compliant motion control of planar redundant manipulator by amplifying joint torsional deflections

The paper describes a compliance control strategy using null space motion of the redundant manipulator. In many robotic systems, the compliance or elasticity such as harmonic drive gears , deflection of links, flexibility of joint shafts and so on, is present. In the proposed approach, such torsional deformation due to naturally existing compliance or elasticity are positively utilized into the null space motion of the redundant manipulator. The total deformation at the end-effector can be precisely estimated in real-time by comparing internal position sensor with real position which is measured by optical sensing. By using this measured deviation, the natural compliance can be virtually amplified to realize a compliant null space motion. The validity of the proposed method is confirmed by several experimental results.