Study Of Longitudinal Motion And Control Of High Speed Catamaran

With the rapid development of the high performance ships, high speed catamaranhas attracted more and more attention because of its high speed, good stability and anopen deck. All these advantages make the high speed catamaran has a broad prospectin the military and civil fields. But as the platform of transportation on the sea,compare with normal catamaran, high speed catamaran not only has the torsionalshaking and seasick phenomenon caused by coupling rolling and pitching in obliquewaves, but also produce more severe longitudinal motions(heaving and pitching) andgreater vertical acceleration because of the high speed or larger encounter frequency.Therefore, built-up necessary and applicable control device to decelerate thelongitudinal motion must be considered. Besides, in order to slow down thelongitudinal movement, the best control strategy and model must be provided.This paper introduces a control device, assembling T-foil and interceptor, whichhas the practical value. Controllable hydrofoil on the bow while interceptor on thestern, using lift effect of the T-foil and drag-lift effect of the interceptor to resist theheaving and pitching. So the CFD software FLUENT has been used to take somecalculations and investigations on the ship hydrodynamic performances, includingbuilt-up T-foil on the catamaran, built-up interceptor on the catamaran and built-uptogether T-foil with interceptor on the catamaran. At the same time, a concept of thestatic characteristics is proposed to measure the maximum anti-pitching andanti-heaving capacity of the control device.On the basis of the simulation and prediction of the static characteristics, thetheory of the ship motion and numerical calculation method should be further applied,using the commercial software AQWA to calculate the response characteristics of thecatamaran’s longitudinal movement, hydrodynamic coefficient and wave force whichcan provide necessary input to the design of the combination control strategy, controlmodel and control parameter of the T-foil and interceptor.After getting the response characteristics of the catamaran’s longitudinalmovement, hydrodynamic coefficient and wave force, automatic control simulationmodel of catamaran’s pitching and heaving must be established in the Simulink environment of the Matlab from which we can obtain the combination control strategy,control model and PID of the T-foil and interceptor. Next, automatic controlsimulation test of pitching and heaving should be conduct so as to observe theeffectiveness of anti-pitching and anti-heaving. Finally, take activated control of T-foiland interceptor, give the relationship between amplitude and frequency of heaving andpitching and statistical characteristic values of heaving and pitching under thedifferent sea conditions and then compare the simulation results with the result of thebare hull and the result of the passive control of hull with the T-foil and interceptor.