A multirate autotuning PI with improved static performance

Among the performance degradation effects that occur with finite precision implementations of controllers, a seldom addressed one is static imprecision. This paper proposes a multirate realization of a PI controller, relying on the frequency separation between the integral action and the remaining controller dynamics, that improves static precision, while minimally affecting dynamic performance. Suitable feasibility conditions for this approach are discussed, and its integration in existing PI tuning methods is also addressed. Conveniently enough, the proposed multirate realization of the controller can be implemented with standard single rate hardware machinery. Simulation results are reported to illustrate the effectiveness of the proposed methodology applied to a well known and widely used tuning procedure.