Passive impedance control with time-varying impedance center

Humans can perform skillful tasks adaptively and safely while interacting with uncertain dynamic environment. With respect to the adaptation ability, it was pointed out that impedance control could play a center role in the human motor control mechanism. Related with safety, it was reported in robotics that the arm's passivity as seen from its environment or manipulated object is very important. In this paper, we study the passivity of impedance control with time varying impedance center. We propose a novel energy-based control method to adjust the impedance center so that the robot arm can realize passive impedance. We verify the effectiveness of our approach by computer simulations.