PID Controller Design for the Dead Time Dominant Unstable Process

S. Lee, M. Shamsuzzoha, and M. Lee (Korea)


Unstable process; dead time dominant; IMC-PID; robust analysis


The modified IMC filter has been proposed for the open loop dead time dominant unstable processes. Based on the proposed filter the PID tuning rule has been derived for the FODUP and SODUP models. The result of the searching of the filter structure for the IMC-PID controller design clearly exhibit that the critically damped filter doesn’t gives satisfactory response for the dead time dominant unstable processes. This is due to the large integral time, and performance can be improved by reducing the integral time. The simulation studies show that the proposed design method provides better performance for both disturbance rejection and setpoint. The robustness for the parametric uncertainty of the controller is evaluated theoretically by Kharitonov’s theorem and multiplicative uncertainty bound has been also proposed based on norm-bound uncertainty principle.

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