Trajectory Tracking Control of Morphing Space Robot for Space Debris Capture

Space robots have always been a primary choice for outer space missions including debris capturing and removal and on-orbit servicing. Modeling and control of a space robot is quite challenging as compared to its terrestrial counterpart, because of the dynamic coupling effects. The dynamic equations of motion of the chaser spacecraft are derived in the target frame. The relative motion between the two spacecraft is given by the Hills equations. The along-track formation is used to perform the close-range maneuver. A span morphing arm is used for the debris capturing to ensure a safe distance between the chaser and the target. Arm joints follow a quintic polynomial trajectory. Spacecraft has two operating modes, controlled floating mode and free-flying mode during close-range maneuvering and debris-capturing processes, respectively. Two separate PD controllers are used for both the chaser and the robotic arm. The controller is able to get the desired results by following the reference trajectory while the error is contained within the specified limits.