Publication

We discuss an inherent problem occurring in the former operational-based compliance control scheme. In order to obviate this problem, an independent joint-based compliance control scheme is proposed. This control method requires that for the adjustment of the operational compliance matrix, a manipulator should have at least the same number of joints as the number of independent components of the desired compliance matrix specified in the operational space. Types of robot structures which are appropriate to independent joint-based compliance scheme are addressed. A five-bar finger with redundant actuators is treated as an illustrative example. Our experimental results show that the proposed compliance modulation method gave satisfactory performance. We also consider an additional stiffness effect due to the antagonistic conflict between the controlled-operational force and the equilibrium joint torque vector. It is also experimentally shown that this additional term notably improved the force tracking performance of the given mechanism.