Design of guidance algorithm for a space manipulator

In the past decades, due to the growing complexity of space missions, the need for operations such as maintenance, refueling, de-orbiting and re-orbiting has increased. Missions with such goals, the so called In Orbit Servicing (IOS) missions, can be accomplished with the help of space robotics systems (or space manipulators). The use of such systems has been proven to be a promising approach to IOS in several occasions. For instance space manipulators have been used during the Space Shuttle missions, on the ISS, and played a key role in the maintenance of the Hubble Space Telescope. In addition, IOS missions could be a good solution removing the growing amountof space debris and inactive satellites orbiting around the Earth, which represent a hazard due to the risk of collision with new constellation of satellites. Motivated by the previous considerations, the work of this thesis is to design an optimal guidance algorithm for a space manipulator. The trajectory planning was treated as an optimization problem, which gives the advantage of handling constraints on joint angles and angular velocity. A heuristic optimization algorithm based on searching methods, the so called Particle Swarm Optimization (PSO) algorithm, was used to solve such problem. The reference space manipulator is the one designed for the active debris removal ESA mission e.Deorbit. A simulator in MATLAB/SIMULINK environment was developed, modeling the dynamics and kinematics of the robot manipulator and of the base satellite. The designed guidance algorithm was tested together with two different type of controllers (a second-order sliding mode controller and a Linear Time-Varying MPC). A Linear MPC was also developed to control the spacecraft attitude during the movement of the manipulator. A simulation was performed to analyse the effect of the manipulator’s torque disturbances on the base satellite to ensure that the attitude was kept constant during the whole maneuver.