Motion analysis of a free-tumbling satellite and experimentation of the grasping task with two fixed-base LWR robots

Abstract

On-orbit servicing missions are a new class of space missions where a servicer is launched in the orbit of another spacecraft, the client. The servicer navigates to the client with the intention of manipulating it using a robotic arm. The function is to repair, refuelling, de-orbiting or grasping the client that could be a satellite or a space debris left in orbit by previous missions and growing in recent years. Both approach and docking of the two spacecrafts in orbit lead to various challenges in the area of space flight dynamics. This work intends to analyze some phases of the German on-orbit servicing mission DEOS, like the motion of the free client satellite, where particular motions are shown, and its grasping by a servicer in an experimental way using two Light Weight Robot provided by DLR. Moreover the effects of the energy dissipation are presented among which environmental torques and sloshing that could bring the satellite in a flat-spin motion. Controls of approach, grasping and stabilization are developed on the chaser robot arm to approach a moving satellite whose dynamics are implemented on the second LWR that can be manipulated using the force sensors integrated on the robot.