Post-filtering output feedback variable structure control

A full state constructed sliding mode is popularly used in a variable structure control system. To encounter with the insufficient measurement problem of the system state, a post-filtering approach to variable structure output feedback control is proposed. The proposed post-filter is used to convert the linear time invariant SISO system output into a pseudo-state sliding mode dynamics which is suitable for conventional VSS control law. It is a dynamic variable structure output feedback approach without a state observer. Stability of the digital post-filter is studied judiciously. The noncausal problem, due to the system with relative degree higher than one, discretization for inverse transfer function of the post-filter is recommended and concluded with the stable zeros conditions proposed by Astrom et. al.