The sliding mode control with unidirectional auxiliary surfaces(UAS-SMC) is proposed for a class of nonlinear
systems with state constraints. And the unidirectional auxiliary surfaces(UAS) are designed by the state constraints. By
using the UAS to constitute the boundaries of the positive invariant sets, the constraints of the system states are guaranteed.
The stability of the system and the invariant sets which consist of the UAS are proved. The simulation results show the
effectiveness of the proposed method.