Output feedback tracking in causal nonminimum-phase nonlinear systems using HOSM techniques

Asymptotic output feedback tracking in a class of causal nonminimum phase uncertain nonlinear systems is addressed via sliding mode techniques. Local asymptotic stability of the output tracking error dynamics along with boundedness of the internal state are proven. Unstable internal states are estimated via proposed multistage observer. Integral sliding mode control is proposed for robust stabilization of the tracking errors and direct estimation/compensation of the unknown inputs, which is treated as an external disturbance. A numerical example illustrates the efficiency of the developed output feedback tracking approach.