Discretization method of continuous-time controllers based on frequency response fitting

In the present paper, a digital redesign problem that converts continuous-time controllers into digital controllers is considered. A new discretization method based on matching of the frequency response of a continuous-time control system is proposed. The frequency response is matched using the least squares method based on data of discrete frequency points. The matching problem is described using an LMI, and the stability condition of the closed-loop system and the redesigned controller are described as additional conditions of LMIs. An optimizing problem described by some LMI conditions is solved by an iterative procedure. Examples are presented that prove the superior performance of the proposed method.