Roll reduction of ships at slow or zero speeds still remains a challenge in marine engineering. This thesis revisits tank stabilization systems, and starts with a critical review of their development since 1883 to the present. It goes on to investigate the application of modem control techniques, power consumption, and different tank configuration to monohulls and trimarans. It is shown that during the development of tank stabilizing systems the weak link in most cases was the control system, the technology to implement them was not available. Only now with advanced control theory and high speed computing power can the potential of some of these systems be exploited. This thesis applies the current advanced technological and computational techniques to some older ideas that could not be practically realized before. It is shown that the lack of an effective control system of anti-roll tanks is due to the philosophy of trying to control the system with feedback control while a much more suitable approach for this particular application is feedforward control. The thesis develops two strategies (both feedforward) to control the pumps used in active tanks: 1) Auto regression is used to predict the incident wave motion. The predicted wave motion is used as the input to the tank/pump system. 2) Control of the actuating pumps of an active U-tank with an adaptive inverse controller using a filtered-x least mean square algorithm. Both the methods are shown to provide excellent roll stabilization in different sea conditions for monohull and trimaran vessels. Historically tank stabilization systems have only been fitted to monohulls. The application of tank stabilization systems is extended to multihulls, the performance of U-tanks and free flooding (or n-tanks) is compared. The n-tanks can be located in the low value volume of the side hulls with minimum impact on the box structure, thus providing good ship stabilization at low speed with low ship impact.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:689433 |
| Date | January 2007 |
| Creators | Moaleji, R. |
| Publisher | University College London (University of London) |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://discovery.ucl.ac.uk/1445028/ |
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