Modelling for the effective control of the electric flow heaters - Simulation validation

This paper suggests the possibility of improving the performance of the control system for electric flow heaters by applying the balance-based adaptive control (B-BAC) methodology, in which the synthesis of the control law is always preceded by the nonstationary balance-based modelling according to the general but also strictly defined rules. The resulting simplified model of a heater is derived assuming a large uncertainty on the process nonlinearities and it has the form of the first-order dynamic equation with the only one time-varying parameter that represents the unknown nonlinearities and modelling inaccuracies. The value of this parameter is unknown so we suggest its on-line estimation by the weighted recursive least-squares (WRLS) method. The modelling accuracy is investigated by the simulation in the application to the example nonlinear electric flow heater. It is also shown how to derive the B-BAController on the basis of the suggested model. The generality of the simplified model ensures that the B-BAC methodology can be applied to control a wide variety of electric flow heaters and its application results in more effective control system, which is also verified by simulation in the comparison to the conventional PI controller. (C) 2008 Elsevier B.V. All rights reserved.