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 feedback stabilization with L2 disturbance attenuation for nonlinear uncertain systems. A new method of state-dependent scaling is introduced into the output feedback design, which unifies treatment of nonlinear and linear gains. The effect of disturbance on the controlled output, which is allowed to be any function of measurement output, can be attenuated to an arbitrarily small level with global asymptotic stability if the plant belongs to a wide class of interconnected systems whose uncertain components unnecessarily have finite linear-gain. The uncertain dynamics is not limited to input-to-state stable systems either. The approach is not only a natural extension of popular approaches in robust linear control, but also advantageous to numerical computation. The design procedure proposed in this paper consists of novel recursive calculation of robust observer gain as well as feedback gain.