Development of two-degree-of-freedom control for robot manipulator with biarticular muscle torque

This paper suggests control algorithm for a robot manipulator which has biarticular muscle torque input in addition to the conventional two monoarticular muscle torques. Using a modified Jacobian matrix which is based on the absolute angle of two joints, we derive simple relationship between an endpoint force/position and three muscle torques. Based on this relationship a feedback controller is developed to design endpoint stiffness. The proposed control realizes the endpoint stiffness with arbitrary major axis, minor axis, and tilt angle with simple gain decision. As for the feedforward control, the dynamics of three muscles torque are derived and used as inverse dynamics in the control. It is found that with this biarticular muscle torque, the inertia matrix can be decoupled and has only diagonal elements. Simulation result shows the effectiveness of the proposed control.