In this paper, we discuss an inherent problem occurring in 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 thatfor 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 structureswhich 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 former compliance control schemes does not guaranteemodulation of the required operational compliance matrix, while performance of the proposed compliance modulation method has been satisfactory. We also consider an additional stiffness effect due to the antagonistic fighting between thecontrolled-operational force and the equilibriumed joint torque vector. It is also experimentally shown that consideration of this additional term notably improves the force tracking performance of the given mechanism.
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