Controllability and Observability Functions for Model Reduction of Nonlinear Systems

is zero during this interval. Clearly in most applications, this is not the case. Hence, a class of model In this paper we consider the problem of model rereduction techniques has emerged based on viewing duction for a nonlinear plant under the in°uence of a the plant as part of a larger closed-loop system. The control system. We relate this problem to the notion usual assumption is that the system is in closed-loop of balance realizations by extending an existing defwith an LQG optimal controller[3, 5, 8, 9]. In which inition of a nonlinear observability function. In the case, the model reduction is performed using so-called special case of linear systems connections to LQGLQG-balanced realizations. The mechanics for synbalancing are presented. thesizing an LQG-balanced realizations are similar to those used for open-loop balancing except that the controllability and observability functions are deter