An approximation algorithm of fractional order pole models based on an optimization process

This paper proposes a new approximation scheme which is an extension of the well-established Charef´s approximation method. The method relaxes the constraints on the locations of pole-zero pairs of the approximation system, which provides more flexibility and space for approximation system to approach the approximated system as possible. The approximation system based on a optimization process perform not only a good gain fit but a good phase fit. The benefits from using the proposed scheme are illustrated by numerical examples in frequency domains.