An output feedback sliding mode control strategy for MIMO systems of arbitrary relative degree

This paper develops an output feedback sliding mode controller for MIMO systems of any relative degree. A minimal set of outputs and output derivatives are identified to determine an augmented system which is relative degree one and a robust sliding mode differentiator is presented as the means to construct the extended output signal. It is shown that the transmission zeros of the original plant appear directly in the reduced order sliding mode dynamics relating to the augmented system. A super twisting control algorithm is shown to provide robust control performance. Nonlinear simulation results for a ninth order nonlinear description of a web-transport system are used to demonstrate the efficacy of the approach.