Sliding Mode Techniques and Dynamic Obstacle Avoidance for Rendezvous Maneuver

The purpose of this thesis is to demonstrate the effectiveness of the artificial potential field (APF) method to bypass obstacles in orbital maneuvers. In particular, the study is applied to a rendezvous maneuver, in which a moving satellite (chaser) is trying to reach a second satellite (target). In this thesis, a fixed target is considered, instead the chaser is modeled in details, including actuator and parameter uncertainties. The APF method has the task of attracting the chaser towards the target while ensuring collision avoidance of moving obstacles. They are considered to be spherical and with known radius. Moreover, the position of the obstacles is measured by LiDAR (Light Detection And Ranging) technology. This scenario is simulated by Matlab software, in which the nonlinear dynamics and guidance and control algorithms are implemented. As briefly described above, the guidance function is based on the APF, while a first-order sliding mode technique for the position control and a super-twisting for the attitude dynamics are used to track the gradient of the artificial potential field. The actuation system consists of thrusters to provide forces for position tracking and reaction wheels for the attitude control by variations of the moment. Extensive simulations guarantee the effectiveness of the proposed approach. Finally, the results show that the chaser is able to overcome obstacles and to approach the target.