Abstract
Human assist devices are expected to be developed in the field of welfare, home, factory and so on. The devices are required to not only to assist the human but also to be strictly stable. Impedance control based on position control is often used for the human assist devices because the control system is simpler than that of the devices based on force control. But if the impedance parameters are made to be smaller in order to get good maneuverability, the system becomes unstable because of the delay of the position control system especially when the assisted tools touch high stiffness environment such as a wall. In this paper, we propose an impedance control method based on position control by employing passive elements such as a mass, a spring and a damper. Then we show in a simulation that the system controlled by the proposed method with very low impedance parameters is stable even if the system touches a high stiffness environment.
