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Modelling and predictive control of a drum-type boiler

Molloy, Barbara (1997) Modelling and predictive control of a drum-type boiler. PhD thesis, Dublin City University.

Boilers generate steam continuously and on a large scale. Controlling the boiler process is extremely difficult - it is a highly nonlinear process, its dynamics vary with load and it is strongly multivariable. It is also inherently unstable due to the integrator effect of the drum. In addition, boilers are commonly used in situations where the load can change suddenly and without prior warning. Traditionally, boilers have been controlled by Single-Input, Single-Output (SISO) Proportional plus Integral (PI) controllers. This strategy does not take into account the interaction of the controlled variables or the effect of load on boiler dynamics. This work investigates whether boiler control can be improved by applying multivariable or nonlinear predictive control strategies. Predictive control is a model-based control strategy which is chosen for its ability to handle nonlinear, constrained and multivariable systems. Two nonlinear controllers are developed - a fuzzified linear predictive controller which is based upon several linearised models of the plant and and a nonlinear predictive controller, based upon a single nonlinear plant model. These controllers are compared both with each other and with the conventional PI control strategy. A detailed first-principles model of the boiler is developed for this work. This is used to simulate a boiler plant for controller testing. It is also used to derive a linear state-space model for the linear predictive controller. The nonlinear predictive controllers uses a neural network model.
Item Type:Thesis (PhD)
Date of Award:1997
Supervisor(s):Ringwood, John
Uncontrolled Keywords:Steam boilers; Automatic control
Subjects:Engineering > Electronic engineering
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Engineering and Computing > School of Electronic Engineering
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
ID Code:19082
Deposited On:02 Sep 2013 10:53 by Celine Campbell . Last Modified 02 Sep 2013 10:53

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