Robust H/sub /spl infin// state observer design for a class of nonlinear systems via switching

A robust H/sub /spl infin// hybrid state observer design method for a class of nonlinear systems is put forward. Suppose that there exist finite candidate observers in a given set of observers, and none of the individual observers is robust H/sub /spl infin// observer which makes the error system of nonlinear system stabilizable with H/sub /spl infin// disturbance attenuation. The problem is to design a switching law under which the switched observation process remains robustly stable and the specified upper bound constraint of the L/sub 2/ gain from exogenous disturbances to error state outputs is simultaneously guaranteed. Based on single Lyapunov function technique and multiple Lyapunov function technique, respectively, two sufficient conditions for the switched nonlinear error systems to be stabilizable with H/sub /spl infin// disturbance attenuation are derived and the gain matrices of observers are designed. All results are given by linear matrix inequalities (LMIs). Finally, a simulation example illustrates the main results of this paper.