Output feedback sliding mode control for nonminimum phase systems with nonlinear disturbances

In this paper, robust stabilization for a class of systems with a nonlinear disturbance is considered. The nonlinear disturbance is mismatched with a nonlinear bound and the nominal system is allowed to be nonminimum phase. A dynamical compensator is designed to estimate the system state and a sliding surface, in the augmented space formed by the system output and the estimated state, is proposed. The stability of the corresponding sliding mode is analysed using the equivalent control approach. Based on the estimated state variables and system output, a variable structure control scheme is developed such that the system is driven to the sliding surface and maintained on it thereafter. Finally, a simulation study of a nonminimum phase HIRM aircraft model is presented to illustrate the effectiveness of the results.