Centralized PID Controllers for Unstable System
This chapter presents a method of designing the centralized control system for the unstable system using the relay auto-tune method incorporating the effect of higher-order harmonics. The method of simultaneous auto-tuning of the four controllers is proposed for designing the TITO centralized control system. The limit cycles are obtained in the outputs with the same frequency but with different amplitude and time shift. The simulation studies on two TITO examples to evaluate the improved performances are presented. The robust behaviour of the proposed controller is analysed by using the inverse maximum singular value versus frequency plot.