Controller design for integrating processes using user-specified gain and phase margin specifications and two degree-of-freedom IMC structure

In real industrial practice, controller designs are usually performed based on an approximate model. Furthermore, the parameters of the physical systems can vary with operating conditions and time. Therefore, it is essential to design a control system which will show a robust performance in the case of aforementioned situations. Gain and phase margins are well known measures for maintaining the robustness of a control system. In the literature, there are many publications considering controller designs for stable processes based on gain and phase margins specifications. However, for integrating processes, controller designs with user-specified gain and phase margins are very rare. This paper presents a new two degree-of-freedom Internal Model Control (IMC) structure and simple tuning rules to tune/design PD controllers for integrating processes with a small dead time to meet specified gain and phase margins. Simulation examples are given to illustrate that the proposed design method can give better closed loop system performances than existing design methods which is also designed based on user-specified gain and phase margins.