Dynamic output feedback variable structure control for system stabilization

Simplex type dynamic output feedback variable structure control for stabilizing multivariable linear time-invariant plants is analysed. Two types of controllers are considered; a compensator type and an observer type. It is shown that while the compensator-type controller stabilizes the plant only if the plant is minimum-phase, the observer-type controller does not face the same restriction. The design of low-order (less than the order of the plant) observer-type controllers is also considered.