Fixed-Time Spacecraft Attitude Control With Unwinding-Free Performance

This note studies the problem of rapid attitude control with high accuracy for rigid spacecraft undergoing unwinding-free performance. By designing a novel non-singular sliding function, fixed-time convergence and unwinding-free performance is rigorously established on the sliding surface. In addition, by introducing a novel potential function to design the controller, unwinding-free performance is also ensured outside of the sliding surface. Furthermore, the chattering problem is tackled by properly modifying the control strategy, with which the attitude tracking error is ensured to converge to an arbitrarily pre-defined residual set and the unwinding-free performance is also preserved. Numerical simulations also verify the effectiveness of the proposed method.