A unified approach for proportional-integral-derivative controller design for time delay processes

An analytical design method for PI/PID controller tuning is proposed for several types of processes withtime delay. A single tuning formula gives enhanced disturbance rejection performance. The design method is based onthe IMC approach, which has a single tuning parameter to adjust the performance and robustness of the controller. Asimple tuning formula gives consistently better performance as compared to several well-known methods at the samedegree of robustness for stable and integrating process. The performance of the unstable process has been comparedwith other recently published methods which also show significant improvement in the proposed method. Furthermore,the robustness of the controller is investigated by inserting a perturbation uncertainty in all parameters simultaneously,again showing comparable results with other methods. An analysis has been performed for the uncertaintymargin in the different process parameters for the robust controller design. It gives the guidelines of the Ms setting forthe PI controller design based on the process parameters uncertainty. For the selection of the closed-loop time constant,(τc), a guideline is provided over a broad range of θ/τ ratios on the basis of the peak of maximum uncertainty(Ms). A comparison of the IAE has been conducted for the wide range of θ/τ ratio for the first order time delay process. The proposed method shows minimum IAE in compared to SIMC, while Lee et al. shows poor disturbance rejectionin the lag dominant process. In the simulation study, the controllers were tuned to have the same degree of robustnessby measuring the Ms, to obtain a reasonable comparison.