Sliding controller for output feedback of a class of state dependent nonlinear systems

This paper considers the output feedback control of single input single output uncertain nonlinear systems without the matching condition. The approach is based on the control parametrization employed in classical model reference adaptive control (MRAC). The nonlinearities are allowed to depend not only on the plant output but also on the plant unmeasurable state. The variable structure model reference adaptive control (VS-MRAC) is redesigned with an appropriate state upper bound for the rejection of state dependent input disturbance. Global or semi-global exponential stability of the closed loop system with respect to a small residual set is achieved. A simplified version of VS-MRAC with constant modulation functions is applied to the nonlinear longitudinal dynamics of a Twin Otter aircraft for pitch pointing manoeuvre.