DESIGN, ANALYSIS AND EXPERIMENTAL VERIFICATION OF A NOVEL NONLINEAR PI CONTROLLER

In this study, a novel variable gain PI controller structure is introduced. The proposed controller structure consists of a sector-bounded nonlinear function of the relative error value in cascade with a linear fixed-gain PI controller. The stability analysis of the closed loop system is examined through Popov stability criterion, Routh-Hurwitz stability method and stability boundary locus method for both second-order and higher-order systems. In addition, the performance of the controller against parameter variations and disturbances is investigated through some simulations for second order systems. An experimental study, an active suspension system, is conducted to examine the performance of the controller for higher order systems. In the literature, there are similar controllers, but the proposed one is superb in terms of effectiveness and stability. The new controller prevents the saturation of the controller signal. Simulation results and experimental studies reveal that proposed controller structure is quite effective for both lower and higher order systems.