A frequency domain model-order-deduction algorithm for linear systems

Physical system modeling, whether automated or manual, requires a systematic procedure to choose the appropriate order of a system model. This can be most readily accomplished by determining the appropriate order of the component submodels. With previous schemes, the primary means to determine the required order of component submodels has been to focus on the eigenvalues of the model, specifically, the behavior of the eigenvalues inside of a circle in the complex plane defining a given spectral radius. In this paper we develop a new algorithm, FD-MODA, that uses changes in a model frequency response as an algorithm-stopping-criterion. The model's frequency response provides a more comprehensive indication of model performance and adequacy than just the eigenvalues, and is more meaningful in the context of frequency-domain controller design methods.