Sliding mode control using method of stable system centre for nonlinear systems with output delay

Output tracking in causal nonlinear systems with an output delay is considered using sliding mode control. The challenge is that sliding mode control in such systems often yields large low frequency oscillations. The problem is reduced to that of the tracking of the output reference profile given by an exogenous system in a causal nonminimum phase system without delay, where the delay is being replaced by its Pade´ approximation. The nonminimum phase output-tracking problem is transformed to a corresponding state-tracking problem. Bounded state tracking profiles are generated by equations of the stable system centre. A sliding mode control algorithm is developed. A numerical example is considered.