A dynamic output feedback controllers for mismatched uncertain variable structure systems

This paper proposes a dynamic output feedback controllers for variable structure systems. It is based on the concept of output feedback controllers, introduced by Z ak and Hui (IEEE Trans. Automat. Control AC-38 (1993) 1509) and Kwan (IEEE Trans. Automat. Control AC-41 (1996) 1691) for matched uncertain variable structure systems in which the state is unavailable and no estimated state is required. In this paper, we extend this idea to a class of mismatched uncertain variable structure systems. A modi"ed variable structure controllers is derived to guarantee the existence of the sliding mode by using output feedback only. The stability of the equivalent reduced-order system in the sliding mode is assured under certain conditions. 2001 Elsevier Science Ltd. All rights reserved.