A robust backstepping sliding mode control is proposed for a class of uncertain nonlinear systems in semi-strict
feedback form. The backstepping method is employed to design the virtual controller to guarantee the stabilization of the
preceding ?? − 1 steps subsystem and restrain unmatched uncertainties. In the ??-th step, a continuous and differentiable
sliding mode variable structure control law is designed to eliminate the chattering and achieve robust output tracking in the
presence of unknown uncertainties and disturbances. Using Lyapunov approach, it is proved that all signals in the closed
loop systems are ultimately bounded. Finally, the simulation results show the effectiveness of the proposed method.