Adaptive output feedback disturbance attenuation control for nonlinear systems with non-harmonic multisource disturbances

This paper focuses on the output feedback regulation for a class nonlinear systems with dynamic non-harmonic multisource disturbances. The key point of this paper is that a kind of non-harmonic disturbances, which have complex nonlinear features, are investigated by using a nonlinear exogenous system. By introducing a nonlinear damping term, a novel adaptive augmented state observer is constructed to estimate the system states, the harmonic disturbances and the non-harmonic disturbances. By integrating the output of the observer with an anti-disturbance controller, an output feedback disturbance attenuation control structure is synthesized such that the closed-loop stability can be guaranteed. Moreover, the results are extended to the disturbances which have intense non-harmonic characteristics. Several illustrative examples are employed to demonstrate the effectiveness of the proposed control structure.