Nonlinear adaptive control via sliding-mode state and perturbation observer

The paper presents a nonlinear adaptive controller (NAC) for single-input single-output feedback linearisable nonlinear systems. A sliding-mode state and perturbation observer is designed to estimate the system states and perturbation which includes the combined effect of system nonlinearities, uncertainties and external disturbances. The NAC design does not require the details of the nonlinear system model and full system states. It possesses an adaptation capability to deal with system parameter uncertainties, unmodelled system dynamics and external disturbances. The convergence of the observer and the stability analysis of the controller/observer system are given. The proposed control scheme is applied for control of a synchronous generator, in comparison with a state-feedback linearising controller (FLC). Simulation study is carried out based on a single-generator infinite-bus power system to show the performance of the controller/observer system.