High gain disturbance observer and its application in robust control attenuation

High gain observer (HGO) has been proved to be a good method to estimate states of Lipschitz nonlinear systems. In this paper, we focus on the HGO based external input (disturbance) estimator and disturbance attenuation control scheme. Firstly, a robust control scheme is proposed to attenuate the disturbance with the assumption that it is obtainable; subsequently, HGO is designed to estimate both the states and the disturbances, and the convergence is ensured under some conditions; then, it is shown that if the gain of the HGO is selected properly, the BIBO stability of the whole system (nonlinear closed system with observer) can be guaranteed; finally, simulation with respect to an inverted pendulum is carried out and the results verify the validity of the proposed scheme.