Robust PID Controller Design for Multivariable Processes

Robust PID controller design for multivariable processes is studied in this paper based on loop-shaping H_infin control. In order to implement the complex H_infin controller, we propose a method to reduce it to a multivariable PID controller, and give a method to choose the pre-compensator which determines the performance of the closed-loop system. The main contribution of the design method is that the PID parameters can be obtained using one design parameter l which reflects the trade-off between stability robustness and time domain performance of the closed-loop system. Simulations show that the designed multivariable PID controllers have good robust stability and performance.