The motivation of this work is to obtain single PI/PID tuning formula for different types of processes with enhanced disturbance rejection performance. © 2008 American Institute of Chemical Engineers AIChE J, 2008 The proposed method illustrates greater robustness against process parameter uncertainty. The robustness of the controller is also investigated by simultaneously inserting a perturbation uncertainty in all parameters in order to obtain the worst-case model mismatch. For a reasonable comparison, the controllers in the simulation study are tuned to have the same degree of robustness by measuring the maximum sensitivity, Ms. The simulation is conducted for a broad class of stable and unstable processes and the results are compared with those of recently published PID type controllers to illustrate the superiority of the proposed controller. An ideal feedback controller equivalent to internal model control (IMC) is obtained through the IMC design principle, and is further simplified to the PID cascaded with a first-order lead-lag compensator. A two-degree-of-freedom control scheme is used to cope with both regulatory and servo problems. A closed-loop time constant λ guideline is also proposed for several process models to cover a wide range of θ/τ ratios.Ī design method for a proportional-integral-derivative (PID) cascaded with a lead-lag compensator is proposed for enhanced disturbance rejection of the second-order stable and unstable processes with time delay. The robustness analysis is conducted by inserting a perturbation in each of the process parameters simultaneously, with the results demonstrating the robustness of the proposed controller design with parameter uncertainty. The simulation studies of several process models show that the proposed design method provides better disturbance rejection for lag-time dominant processes, when the various controllers are all tuned to have the same degree of robustness according to the measure of maximum sensitivity. In this study, an optimal internal model control (IMC) filter structure is proposed for several representative process models to design a proportional-integral-derivative (PID) controller that produces an improved disturbance rejection response. The IMC-PID tuning rules demonstrate good set-point tracking but sluggish disturbance rejection, which becomes severe when a process has a small time-delay/time-constant ratio. The simulation has been conducted for a broad class of stable and integrating processes, and the results are compared with a recently published paper of Shamsuzzoha and Skogestad (2010).1 The proposed tuning method gives consistently better performance and robustness for a broad class of processes. The controller integral and derivative time (τI and τD) is mainly a function of the time to reach the first peak (tp). The controller gain (Kc/Kc0) is only a function of the overshoot observed in the set-point experiment. On the basis of simulations for a range of first-order with time delay processes, simple correlations have been derived to give PI/PID controller settings. The method requires a closed-loop step set-point experiment using a proportional only controller with gain Kc0. This is a simple method to obtain the PI/PID setting which gives the acceptable performance and robustness for a broad range of the processes. The proposed closed-loop tuning method overcomes the shortcoming of the well-known Ziegler-Nichols (1942) continuous cycling method and it can be an alternative for the same. The objective of this study is to develop a new online controller tuning method in closed-loop mode.
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