Robust PID controller design for time delay processes with peak of maximum sensitivity criteria

Mohammad Shamsuzzoha

(Department of Chemical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia)

Abstract:The motivation of this work is to obtain single PI/PID tuning formula for different types of processes with enhanced disturbance rejection performance. The proposed tuning formula consistently gives better performance in comparison to several well-known methods at the same degree of robustness for stable, integrating and unstable processes. For the selection of the closed-loop time constant (τ_c), a guideline is provided over a broad range of time-delay/time-constant ratios on the basis of the peak of maximum sensitivity (M_s). An analysis has been performed for the uncertainty margin with the different process parameters for the robust controller design. It gives the guideline of the M_s-value settings for the PI controller designs based on the process parameters uncertainty. Furthermore, a relationship has been developed between M_s-value and uncertainty margin with the different process parameters (k, τ and θ). Simulation study has been conducted for the broad class of processes and the controllers are tuned to have the same degree of robustness by measuring the maximum sensitivity, M_s, in order to obtain a reasonable comparison.

Key words:PI/PID controller tuning; internal model control (IMC) method; unstable delay process; integrating delay process; disturbance rejection