New class of discrete-time models for non-linear systems through discretisation of integration gains

A new approach is proposed for obtaining discrete-time models of a non-linear autonomous continuous-time system based on classification of, what is called in this study, a discrete-time integration gain. The models are expressed as a product of this gain and the system function that has the same structure as that of the continuous-time system. Sufficient conditions on this gain to make the model exact, in the sense defined in this study, are presented. A new discrete-time model is proposed for non-linear systems, which is approximate in general, but exact for linear systems. The method is applicable to any system that has a Jacobian matrix. As examples, van der Pol and Lorenz oscillators are examined and simulated to show that the proposed discrete-time models perform better than other discrete-time models that are known to the authors to be on-line computable, and tends to retain such key features as limit cycles and chaos, even for relatively large sampling periods.