Relative Motion Estimation and Control Strategy for a Spacecraft to an Uncooperative Object

Abstract

In this paper, a control strategy for a spacecraft (“Pursuer”) to rendezvous with an uncooperative object (“Target”) is dealt with. This strategy consists of a feedforward optimal control phase (phase 1) and a feedback control phases (phase 2 and 3). In the feedforward optimal control phase, the target's future attitude motion is predicted from the result of motion estimation using image data in order to determine the final state for the maneuver. It is expected that there will be errors in the result of motion estimation for the target and error compensation is expected to be necessary. For this purpose, the pursuer estimates and predicts target's motion during maneuver, and recomputes the optimal control input using it. A quasi-optimal control input is proposed and named “Adjusted Control Input” in order to adapt this error compensation. And its performance is investigated through a numerical simulation of the pursuer's position control.