The development of a model for the nonlinear AAC system which can infer the characteristic of an actual AAC system is essential for the design of the controller. Detailed dynamic mathematical models have been proposed by He et al. [1] and Rasmussen [2], which consisted of high order of differential equations to describe the complexity of thermo fluid dynamics. The authors have simplified the highly nonlinear AAC model via model linearization, but the linearized model is only accurate at certain operating points.