Anti-saturation dynamic surface control for spacecraft terminal safe approach based on command filter

This paper studies anti-saturation control schemes of the spacecraft terminal safe approach. Based on the spacecraft relative motion model of terminal approach and spherical collision avoidance potential function, anti-saturation controller and adaptive anti-saturation controller are designed for the situations of known and unknown upper bound of external disturbances respectively using dynamic surface control (DSC) and auxiliary system. The designed controllers not only take advantage of the first-order command filter to avoid the differential of the virtual control signals, but also introduce the compensating signals to remove the effect of the error caused by the command filter. Under the proposed control strategies, the bounded and uniformly ultimate bounded of the system states are proved via Lyapunov stability theory, and the chaser can approach the desired position without collision with the target. The numerical simulations are conducted to demonstrate that the chaser spacecraft using the designed controllers can realize the terminal approach to the target safely, which further illustrate the effectiveness of the proposed controllers.