On approximate pulse transfer functions

In the paper a systematic approach to a class of approximations to the pulse transfer function of a system consisting of a zero-order hold and a linear continuous-time plant is presented. It is based on the asymptotic result of Astrom-Hagander-Sternby (1984) on zeros of sampled functions for high sampling rates, and on the bilinear transformation. Relationships with a δ-operator based approximation are found. Due to a particular structure of the approximations considered, robust control and identification are suggested as possible areas of their application. The results are illustrated by an example showing the superiority of new approximations over the known ones