Experimental Evaluation of Contact/impact Dynamics between a Space Robot with a Compliant Wrist and a Free-flying Object

This paper presents the experimental evaluation of contact/impact dynamics between a space robot with a compliant wrist and a free-flying object. In capturing a target satellite by a free-flying space robot, a robot must prevent bounce-off of a target satellite from the operational space of the robot due to hard collision. In order to avoid hard collision, the authors propose the use of a stiff manipulator equipped with a compliant wrist because this combination is capable of elongating the contact duration with less contact force peak, and hence, makes the contact control possible. In order to understand contact with a compliant wrist, this paper presents the contact dynamics of a uniaxial compliant wrist, which is modeled by a mass-spring-damper system. Then, simplification is presented so that the dominant contact dynamics parameters can be approximated by the stiffness and damping of the compliant wrist. The collision experiment between a manipulator with a compliant wrist and a free-flying target object is conducted using a two-dimensional microgravity emulator, called the air-floating test bed. The contact duration and the coefficient of restitution were chosen as evaluating parameters, and it was verified that both can be expressed by the stiffness and damping of the compliant wrist.