On the control of redundant robots with variable stiffness actuation

In this paper, the control of a redundant robotic manipulator with variable stiffness actuation is addressed. The problem of controlling simultaneously the end-effector position and stiffness exploiting the robot redundancy for the optimization of the robot configuration is considered, and the relation between the manipulator redundancy and the selection of both the joint and end-effector stiffness is discussed. The controller is configured as a cascade system that allows the decoupling of the actuators dynamics from the arm dynamics and the consequent reduction of the order of the manipulator dynamic model. Only the actuator and joint positions are needed by the controller, introducing in this way a significant simplification with respect to previously proposed state feedback techniques. The effectiveness of the proposed approach is verified by simulations of a 3-DOF planar manipulator.