M.Ing. (Mechanical Engineering) / This dissertation describes the performance of an Adaptive controller and a Neural Network controller for water level control in a steam drum, and compares them to the performance of a conventional PIO controller in the same application. The control problem is in essence the regulation of the speed of a boiler feed pump in order to maintain a constant level in the drum of a small model of a boiler. As a starting point, the hydraulics and dynamics of the system are analyzed and the system is shown to be nonlinear. A nonlinear computer simulation is created and its response is compared with that of the real plant. The simulation proves to be a close representation of the real plant and it is used as an aid in creating a linear mathematical model. A set of control specifications are drawn up and a PIO controller is designed for the plant. With the aid of a root locus diagram it is shown that the plant cannot be controlled within specifications under PID control. This shortcoming is then demonstrated on both the linear mathematical model and the nonlinear plant. Consequently, advanced control techniques are investigated in an attempt to control the plant within specifications. Different methods of adaptive control are discussed and a direct model reference adaptive controller is designed. The least squares algorithm for parameter adjustment is discarded in favour of the slower gradient algorithm when it becomes apparent that the wave motion inside the drum has an adverse effect on the former algorithm. The control results obtained with both the linear model and the real plant proves adaptive control to be superior to PIO control in this application. Additionally, the application of neural networks in control systems is discussed. An adaptive neural network controller is designed but is discarded due to instability caused by imperfect modelling of the system...
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:10884 |
| Date | 24 April 2014 |
| Creators | Smuts, Jacques Francois |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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