Finite-time antisaturation control for spacecraft rendezvous and docking with safe constraint

This thesis studies control schemes for spacecraft safe rendezvous and docking considering input saturation. Based on the spacecraft attitude and orbit coupled model, by using fast terminal sliding mode method, a finite-time antisaturation controller and an adaptive finite-time antisaturation controller are designed for the situations of known and unknown upper bound of external disturbances, respectively. In controller design, a novel continuous and differentiable collision avoidance potential function is presented to restrict motion area and guarantee the safety of the spacecrafts. Meanwhile, the saturation function and auxiliary system are introduced to deal with the input saturation. Lyapunov theory is utilized to prove that the error states of the system under the proposed controllers are finite-time convergent, and the rendezvous and docking without collision can be accomplished. The numerical simulation results indicate that the chaser can realize the rendezvous and docking with input saturation and safe constraint, which can further illustrate the effectiveness of the designed controllers.