Switch-based adaptive nonsingular sliding mode control for spacecraft formation flying

This paper investigates the relative position control problem for a two-agent spacecraft formation. The modified nonlinear dynamic based on C-W equation is adopted to describe relative position between the leader and follower. Considering the system uncertainty and external disturbance, adaptive sliding mode control laws based on linear and terminal sliding surface are proposed respectively. In addition, a switching mechanism is employed to make a selection between the general and terminal surfaces so as to avoid singularity. The convergence of closed-loop system is proved by Lyapunov stability theory. Numerical simulations illustrates the validity of the control law proposed.