Analytical design of robust multi-loop PI controller for multivariable processes

In this paper, the robust design of the multi-loop PI controller for multivariable processes in the presence of the multiplicative input uncertainty is proposed. The paper deals with two major steps: as a first step, the analytical tuning rules of the multi-loop PI controller are derived from the basis of the generalized IMC-PID approach. Then, in the second step, the robust analysis is utilized for enhancing the robustness of the proposed PI control system. The most important feature of the proposed method is that the tradeoffs between the robust stability and performance can be established by adjusting only one design parameter (i.e., closed-loop time constant) via the structured singular value synthesis. To verify the superiority of the proposed method, two illustrative examples taken from previous works are included. The simulation results demonstrate that the proposed method provides the superior performance over several well-known methods in both nominal and robust cases.