Estimation of stability regions of SDRE controlled systems using vector norms

The origin of a state-dependent Riccati equation (SDRE) controlled system is an asymptotically stable equilibrium point. However, knowledge of its region of stability is also of practical importance. Obtaining a good estimate of the ROA for general nonlinear systems-especially of higher order-is a challenging task in itself. For SDRE controlled systems, the task becomes even more difficult since the closed-loop matrix is usually not available in closed form. Borne et al. (1996) and Richard et. al. (1988) proposed a new method for determining the stability of nonlinear systems. The method is based on defining an overvaluing comparison system for the original one by using vector norms. In this paper, an approach to estimate stability regions of SDRE controlled systems using this method is developed. Examples are given to illustrate the procedure.