High-performance conversions between continuous- and discrete-time systems

In this paper, a new algorithm for converting an S-domain model to a Z-domain model is proposed. The resultant Z-domain model is much closer to the original S-domain model than that obtained from conventional conversion schemes such as Tustin approximation with or without frequency pre-warping, zero-pole mapping equivalent, and Triangle hold equivalent. The proposed algorithm adopts the standard recursive least squares approach, and it has the following advantages. First, the computation is trivial and can be easily implemented online. Second, it can handle both parametric and non-parametric models, while conventional conversion methods can only handle parametric models. Third, it is very flexible and applicable to Z- to S-domain model conversion, sampling rate selection, re-sampling, time delay system conversion, and model order selection. The superior performance of the method is demonstrated with several simulation examples in this paper.