A new controller design scheme called the reduced order of sliding mode for a class of nonlinear affine systems
is proposed based on sliding mode control theory. Firstly, the sliding mode control theory is used repeatly for a class of n order nonlinear affine systems. n−1 diffeomorphism transformation functions and n−1 sliding manifolds are constructed. And in this way the original system can be put down to one order, and the variable structure control law is given. Then, by using the mapping relation between the current and higher levels of control input, n−1 times backstepping operations are performed, and the original system control input can be achieved. Finally, the simulation example shows the effectiveness and feasibility of this design scheme.