Finite-time dynamic surface antisaturation control for spacecraft terminal approach considering safety

This paper studies the spacecraft terminal approach control problem by considering safety and input saturation. First, the spacecraft relative motion model of the terminal approach and sphere collision-avoidance potential function are given. Second, on the basis of the dynamic surface control and auxiliary system, two novel finite-time antisaturation controllers are proposed for the situations of known and unknown upper bounds of external disturbances, respectively, which make use of the first-order command filter to avoid the differential of the virtual control signals. At the same time, the compensating signals are introduced to eliminate the effects of the errors caused by the command filter. Finally, the Lyapunov stability theory is used to prove that the states of the system under the designed controllers are practical finite-time stable and the chaser spacecraft can approach to the desired position without collision. The numerical simulations are demonstrated to testify that the chaser spacecraft using the designed controllers can approach the target spacecraft safely, which further illustrates the effectiveness of the presented control strategies.