Antisaturation Attitude and Orbit-Coupled Control for Spacecraft Final Safe Approach Based on Fast Nonsingular Terminal Sliding Mode

Abstract

The problem of spacecraft final approach subject to input saturation and a safe constraint is studied in this paper. First, an attitude and orbit-coupling model with input saturation was established for spacecraft final approach. Second, in order to restrict the safe range of motion, a new continuously differentiable collision avoidance safe constraint function was constructed. Combined with the constraint function, an improved fast nonsingular terminal sliding mode manifold was presented. Further, two antisaturation sliding mode control schemes that adopt auxiliary systems to settle the problem of input saturation were proposed. Finally, Lyapunov stability theory was employed to prove that the error states of the closed-loop system under the presented control schemes are finite-time convergent and there are no collisions during the motion process. Meanwhile, simulations were conducted to verify that the chaser can realize the final safe approach with input saturation, which further indicates the effectiveness of the designed control schemes.