Authors: ERKAN İMAL
Abstract: Most processes are nonlinear, and their control is a difficult yet important problem. The heat exchanger is an example onesuch nonlinear process. In the present paper, the effect of process nonlinearity on the performance of set point tracking and disturbance rejection in two controller methods is investigated. Initially, afirst order plus dead time (FOPDT) model of the process is obtainedvia a software known as Loop-Pro Trainer. Then, the PI-controller tuning values are computed using the internal model control (IMC) correlations based on truncated (first-order) Taylor series approximation. Next, another controller is designed using the coefficient diagram method (CDM). Finally, the performances of the two controllers are compared. It is concluded that a more consistent performance is achieved with a CDM based controller in the environment of an exchanger process that is nonlinear with varying operating levels.
Keywords: Nonlinear process; Loop-Pro trainer; FOPDT model; PI-control; CDM.
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