Disturbance observer based fixed time sliding mode control for spacecraft proximity operations with coupled dynamics

Abstract

This paper proposes a fixed time disturbance observer (FTDO) based fixed time sliding mode control scheme for spacecraft proximity operations in the presence of parameter uncertainties and disturbances. The FTDO is designed to estimate the lumped disturbance which includes kinematic couplings, parameter uncertainties, and disturbances. Based on the observation of lumped disturbance, the fixed time sliding mode control is developed to achieve fixed time convergence, where the FTDO is employed to counteract the lumped disturbances and eliminate the chattering phenomenon. What’s more, the proposed control method can speed up the convergence and improve the control accuracy. Finally, the stability of the closed-loop system is proved via the Lyapunov analysis. Numerical simulations demonstrate the effectiveness of the proposed control method.