LOOP TRANSFER RECOVERY DESIGN VIA NEW OBSERVER-BASED AND CSS ARCHITECTURE-BASED CONTROLLERS

Two new controller structures, namely the continuous-time current-type observer and current-type CSS (Chen-Saberi-Sannuti) architecture-based controllers, are considered in this paper for loop transfer recovery design for general non-strictly proper non-minimum phase systems. The proposed observer is structurally analogous to the current estimator of discrete-time systems, while the proposed CSS architecture falls into the category of the controller structures developed recently by Chen, Saberi and Sannuti.(2,3) The properties of these new structures are characterized. In particular, sets of necessary and sufficient conditions under which a target loop transfer function can be either exactly and/or asymptotically recovered by the abovementioned controllers are obtained. More importantly, the new current-type observer balances the observer structures for continuous-time and discrete-time linear systems.