Cartesian impedance control techniques for torque controlled light-weight robots

The paper compares various approaches to implementing a compliant Cartesian behavior for robotic manipulators: impedance, admittance and stiffness control. A new controller structure is proposed, which consists of an impedance controller enhanced by local stiffness control. This structure consistently takes into account the two time scale property of the joint and Cartesian control loops. The DLR light-weight robot, with its position, torque and impedance interfaces on joint level, is an adequate platform for the implementation of the presented methods. The experimental results are discussed and a critical comparison of the performance with different controllers is made. As an application for the new control structure, the fast and intuitive teaching of an insertion task (piston into a motor block) is described.