Wind Powered Marine Vehicle - A Concept Study
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- Institutt for marin teknikk 
In conventional sailboat design, the heeling momentum introduced by therigid connection of foils in air and water is a limitation on the maximum ve-locity. By removing the hull all together, wetted surface induced drag can beremoved and increase the theoretical maximum velocity of a sailboat. TodayROV s are limited by their attachment to a parent ship through the umbil-ical. AUV s have operational limits due to energy storage capacity. Windis a readably available energy source and is exploited in traditional sailing.By exploiting the wind energy a marine vehicle can increase the operationalspace compared to conventional vehicles. This can be done by incorporat-ing foils for sailing and an energy harvesting system to increase no windperformance. The high vantage point of kites can improve communicationand energy harvesting capabilities. Efficient aerofoils have unstable flightdynamics and high frequency response, and introduce several challenges fora control system. By neglecting higher order dynamics, a simplified modelin combination with experimental data can be used to investigate differentapproaches in control system design regarding a wind powered marine vehi-cle application where a kite is utilized for propulsion. A paravane can reflectthe kite forces in the water with minimum drag and opts for a high speedsailing vehicle that can expand or combine the existing workspace coveredby ROV s and AUV s today. A PID-controller will not be able to control a kite when a random walk pro-cess is introduced on the ambient wind. Different optimization approaches,such as MPC using NLP algorithms and thrust allocation theory, shouldbe considered in future work regarding design of a control system for kites.However, the solution in a thrust allocation approach may not always exist,and specially at critical points in the system response. A feedback lineariza-tion approach may not be trivial to apply, as the control inputs are coupledfor a parawing kite. Errors accumulate quickly, and when approximationsare involved, control on the error dynamics based on the residual from thelinearization may be insufficient.