Robust Output Feedback Disturbance Attenuation of Nonlinear Uncertain Dynamic Systems via State-Dependent Scaling

This paper presents a novel approach to the problem of output feedbackstabilization with L2 disturbance attenuation for nonlinear uncertain systems. A newmethod of state-dependent scaling is introduced into the output feedback design, whichunifies treatment of nonlinear and linear gains. The effect of disturbance on the controlledoutput, which is allowed to be any function of measurement output, can beattenuated to an arbitrarily small level with global asymptotic stability if the plantbelongs to a wide class of interconnected systems whose uncertain components unnecessarilyhave finite linear-gain. The uncertain dynamics is not limited to input-to-statestable systems either. The approach is not only a natural extension of popular approachesin robust linear control, but also advantageous to numerical computation.The design procedure proposed in this paper consists of novel recursive calculation ofrobust observer gain as well as feedback gain