QFT-based design of PI+CI reset compensators: Application in process control

This work approaches the problem of robust control for first-order plus time delay plants. The goal is investigate the potentials of a nonlinear/hybrid compensator previously developed by authors, referred to as the PI+CI compensator, in the control of a process with significant parametric uncertainty. To this end, the design of PI+CI has been made in two steps: first, a base robust PI compensator is designed by using QFT (quantitative feedback theory) to satisfy (robust) relative stability and disturbance rejection specifications, and then a reset percentage of the integral term is chosen in order to improve the transitory response. In addition, a simple modification of the PI+CI compensator, consisting of the introduction of a reset band, is investigated regarding the improvement of the previous design.