A new approach to the discretization of continuous-time controllers

A new method for discretising continuous-time controllers is derived, using principles of controller approximation (Anderson & Yi [1]). It focuses on the closed-loop use of the discrete-time controller. The resulting approximation criterion is a measure for stability of the control system, provides an upper bound on the sampling time for which stability can be guaranteed and because it is based on continuous-time controller approximation it indicates the cost of discretization in terms of performance degradation. The discrete-time controller is obtained through minimization of this criterion, which can be performed with standard software used in H
_∞
controller design.