Practical L-2 disturbance attenuation for nonlinear systems

In this work, a notion of generalized L-2-gain for nonlinear systems, where the gain is considered as a function of the state instead of a (global) co nstant, is presented. This new notion seems to be adequate to characterize the gain properties of several nonlinear systems which do not possess a uni form L-2-gain property (i.e. the L-2-gain depends on the operating point). Moreover, a notion of practical L-2-gain attenuation, which extends the sta ndard definition and parallels (mutatae mutandis) the concepts of practical stability, is also proposed. (C) 2001 Elsevier Science Ltd. All rights res erved.