A framework for the discrete-time, design of intelligent controllers using "state-strict passivity"

This paper presents a framework for the robust discrete-time design of intelligent controllers for a class of nonlinear systems. The closed-loop system is treated as an interconnection of the controller and the tracking error system and the stability of the closed-loop system is explored from an input-output point-of-view. It is shown that a stronger form of passivity, namely state strict passivity, is required to prove guaranteed tracking performance and internal stability for this class of nonlinear systems without standard observability (i.e. "persistence of excitation") conditions.