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Modeling, Control and Improvement of High-Speed Crafts Behavior in Calm Water and Waves

Karimi, Mohammad Hossein | 2013

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 45140 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Abbaspour Fard Tehrani, Majed; Seif, Mohammad Saeed
  7. Abstract:
  8. In recent years, planing boats have been used in more exposed areas, for instance as patrol boats, pilot boats, coast guard and small naval vessels. When such a small vessel operating in a rough-water environment, frequently experiences violent motions and vertical acceleration. Even on calm water, porpoising may occur and may be severe as the speed is increased. Operation of the crew, equipments and overall operability of the vessel always suffer from mentioned motions. In the present study, the impact of fixed and controlled interceptors on a planing crafts hydrodynamic and seakeeping quality is investigated through application of an experimental and theoretical methods. Two scaled-down models of high-speed planing monohull and catamaran are tested with and without interceptors in calm water at different heights of the interceptors to investigate the effect of interceptors on drag reduction of the models. In addition, a scaled-down model of a high-speed planing catamaran is tested with and without controllable interceptors in regular head waves, to investigate the effect of automatically controlled interceptors on vertical motion reduction of the model. Through application of modern optimal control theory and Savitsky’s method, a new analytical model is developed for the prediction of the high speed planing boats performance in calm water with interceptors. In addition, a control-oriented nonlinear model of the vertical motions of the planing boats with interceptors in head regular waves is developed. A Linear Quadratic Regulator (LQR) feedback controller is then adopted to stabilize the vertical motions. A simulation environment has been developed in MATLAB and SIMULINK. MATLAB has been used to formulate the model, to provide a suitable environment for control studies. The results obtained, the model, shows good agreement between the experimental and simulated data. Both the experimental and simulated results show that interceptors can be used not only for minimizing resistance, but also for reducing the vertical motions, especially at or near the resonant frequency. The results also proved that in automatic control system for controlling interceptors, a states feedback (heave, pitch and related velocities feedback) to the interceptors are effective for vertical motions damping of planing boat in calm water and head waves
  9. Keywords:
  10. Interceptor ; Optimal Control ; Heave Boat ; High Speed Craft ; State Space ; Resistance

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