An entropy formula for nonlinear systems

Minimum entropy control theory provides a powerful means of trading off the advantages of optimal H2 and H∞ controllers. In this paper, a framework for the nonlinear minimum entropy control problem is suggested, based on the nonlinear spectral factorization problem. It is also shown that, for a large class of H∞ suboptimal controllers, the central controller minimizes the closed-loop entropy. The techniques used are similar to the time-domain notion of the entropy that was introduced by the authors for time-varying systems.