Wiener model based real-ime identification and control of heat exchanger process

الملخص EN

The control of heat exchanger is complex due to its nonlinear dynamic, particularly the variable steady-state gain and the time constant of the process fluid.

In this paper, two relay feedback tests (RFT) method for the wiener model are discussed to implement in a real-time heat exchanger process.

Wiener model consists of linear subsystem followed by static nonlinearity.

In the first method, symmetric and asymmetric RTF data are used to identify wiener process.

The identification procedure consists of two steps discussed as following first, the symmetric RFT output data is used to obtain the static nonlinearity.

An objective function that aims to change the asymmetry to symmetry, in the system output is formulated.

A standard optimization procedure is used to minimize this objective function by adjusting the polynomial parameters that is used to represent the nonlinear gain of the wiener model.

In the second step, asymmetric RFT output is used to obtain a linear subsystem as first order plus dead time (FOPDT).

By way of this approach, the identifications of linear and nonlinear subsystem in the wiener model are fully separate.

In the second method, an on-line procedure is used to obtain the static nonlinearity.

The linear subsystem is identifying as FOPDT.

Different degrees of system are illustrated to facilitate the understanding of these two RFT methods.

The performance of the wiener model based control strategy is evaluated in real and the results are computed with those of a convention PI controller.