Model order selection criterion with application to physical systems

In this paper, it is shown that poles of the discrete-time equivalent of continuous system will lie in the right-half of the complex plane if the sampling rate is chosen to be more than twice the Nyquist rate. This new criterion allows for a quick and reliable separation between the system´s poles and any extraneous poles emanating from a variety of artifacts such as high frequency noise and nonlinearities in the system. The system is identified for different model orders and only those for which the poles lie in the right-half plane are chosen. Then using a conventional scheme such as Akaike Information Criterion (AIC), the correct order is chosen from the selected model set. The proposed model order selection criterion has been evaluated on a physical system.