Sliding Mode Output Feedback Control of Time-Varying Mismatched Uncertain Systems

This paper presents an output feedback sliding mode control method for a class of time-varying mismatched uncertain systems in which all states are unavailable and estimated states are not required. Using a simple adaptation law, a modified variable structure controller is derived to guarantee the existence of the sliding mode by using output feedback only. The stability of the uncertain system in the sliding mode is assured under certain conditions. Furthermore, the asymptotic behavior of the closed-loop system with mismatched time-varying uncertainties inside boundary layers is analyzed. The validity of the proposed control methodology is demonstrated by simulation results.