Optimal sliding mode control for spacecraft rendezvous with collision avoidance

Abstract

In this paper, the problem of relative motion control of spacecraft close-range rendezvous without collision on elliptical orbit is considered. An autonomous amalgamated control algorithm is presented to deal with the nonlinear dynamics problem with external disturbances. This new control scheme combines the efficiency of the optimal sliding mode control (OSMC) (used for attraction towards goal position) and the collision avoidance capability of the artificial potential function (APF) method (used for repulsion from moving obstacle). The nonlinear optimal control strategy is based on infinite-horizon state-dependent Riccatic equation (SDRE). For ensuring robustness of the optimal controller in presence of parametric uncertainty and external disturbances, a sliding mode control scheme is realized by combining an integral and a terminal sliding surface. The APF controller takes velocity of both the chaser and obstacle into consideration. Using the Lyapunov stable theory, the stability of the closed-loop system is guaranteed. Numerical simulation results are presented to verify the effectiveness and capability of the proposed control scheme.