Functional observability

A simple theorem for <i>Functional Observability</i> is presented considering the observable and unobservable states of a system based on Kalman decomposition. The proposed theorem is also consistent with two other theorems on <i>Functional Observability </i>which was based on eigen decomposition [6]. The paper also reports a new definition for Functional Observability which is consistent with previously reported definitions and theorems [4], [5], [6].