The Dynamic Elements of the Processes Industry Essay

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Vast majority of processes in industry are formed of dynamic elements which are usually of first order. This leads the process to have a linear model of a very high order. Although these higher order models are very precise they are not to be used for the control purposes. Instead of using high order model, behavior of the process is simply modeled as a linear first order system with the dead time element, in most of the cases [1]. The most widely used controller in the process industries is Proportional integral derivative (PID) controller, as it can assure satisfactory performances with simple algorithm for a wide range of processes. They can compensate the effect of both the delayed and non-delayed process. It is important to note that…show more content…
For most single loop controllers, disturbance rejection is more important than set-point tracking, a controller design that emphasizes the disturbance rejection is an important design goal [7, 8, 11]. The goal can be achieved by designing the controller for disturbance rejection, rather than set-point tracking. PID controller cascaded with a lead/lag filter was suggested in the literature [4, 7-10, 12, 16, 17] for disturbance rejection, the efficiency of the PID controller is based on the structure of the IMC filter. The IMC filter structure was selected to make the IMC controller realizable while satisfying the performance requirements. The efficiency of IMC controller and the close approximation of IMC controller to ideal controller determine the efficiency of the resulting PID controller. Therefore suitable IMC filter structure has to be selected not for the performance of IMC controller but the performance of resulting PID controller. Regarding disturbance rejection of lag time dominant processes, Ziegler and Nichols' (1942) established design method (ZN) shows better performance than IMC-PID design methods based on the IMC filter . Horn et al., (1996), Liu et al., (2010) proposed IMC filter; the resulting controller exhibited the advantages over those based on the conventional IMC filter. We propose a new type of IMC filter structure that includes a lead term to cancel
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