Vinnicombe metric as a closed-loop nonlinearity measure

The focal point of this paper is to develop a measure of closed-loop nonlinearity. In this work, the Vinnicombe metric and the quasi-linear parameter varying (quasi-LPV) representation of nonlinear systems are exploited for this purpose. The proposed measure can serve as a decision making tool for control engineers when deciding whether a linear or nonlinear control strategy should be employed to solve their control problems. A continuous stirred tank reactor (CSTR) simulation example is used to illustrate the proposed measure.