Compensated hybrid PI controllers for sampled-data controlled systems

Abstract

Abstract In this paper we consider sampled-data systems controlled by hybrid PI controllers. In these systems, the sample time may induce some undesirable overshoot due to the postponed reset action on the control integral state, which deteriorates the performance of the closed loop by leading to output overshoot as well as to larger settling time values. We propose a methodology to compute a bounded compensating signal to be added to the control input that minimizes the overshoot and the settling time. The action of the compensating signal synchronizes the reset instants of the hybrid PI controller with the sample-time for a class of systems. The proposed methodology is tested in a laboratory setup system composed of two connected water reservoirs with capacity of 200 liters each, actioned by a variable velocity pump. The control objective is to regulate the level of the first tank and to reject disturbances. We compare the performances achieved by two different hybrid PI schemes with and without the proposed additive compensating signal. The experimental tests illustrate the performance, robustness and disturbance rejection achieved by our approach when applied to uncertain systems.