On the Design of Coordinated Impedance Control Laws for De-orbiting and De-Spinning of Cooperative Satellites

In several on-orbit applications, such as deorbiting, continuous contact between a servicing robot (chaser) and a serviced satellite (target) is needed. The task includes chaser free-space motion and subsequent contact interaction with a floating target. To achieve this, usually grasping of the satellite is proposed. However, most of the existing satellites on orbit have no dedicated grapple fixtures. In this paper, a coordinated impedance control law is proposed for the de-orbiting of a target via continuous contact and without grasping between the chaser end-effector and the target. Since both the manipulator’s end-effector and the spacecraft base are controlled, the developed controller guarantees singularity avoidance in addition to maintaining continuous contact between the two bodies. Also, this controller is adapted to be employed in the de-spinning of a rotating satellite with known angular velocity via continuous contact. The developed control laws apply to spatial systems and are illustrated by planar examples.