A structured sliding mode controller for a class of underactuated mechanical systems

Based on sliding mode control, a new Structured Sliding Mode Controller (SSMC) for a class of underactuated mechanical systems (UMSs) with three degrees of freedom (DOF) is presented in this paper. Mainly, this class of UMSs presents three DOF and includes three different subsystems. Moreover, three sliding surfaces are constructed and in order to guarantee the convergence to zero of each sliding surface, a new control strategy is proposed. By using theoretical analysis, the SSMC is proved to let all states converge asymptotically to zero. Simulation results applied on a double inverted pendulum on cart show the validity of the proposed method.