This paper proposes an output feedback variable structure control to stabilize a class of uncertain systems in which the state is unavailable and no estimated state is required. The special sliding hyperplane is introduced so that the output of the system is initially on the hyperplane no matter where the initial output is, and the stability of the equivalent reduced-order system in the sliding mode is assured under a certain condition. Further, based on the concept of the equivalent motion and the known bound of the initial state, the constant control gain is derived to guarantee the existence of the sliding mode. Finally, an aircraft model is given to illustrate this design approach.
