An attempt to control the motion of floating current turbine by the pitch control

Recently, R&D of marine renewable energy becomes very popular all over the world. In this paper, the contra-rotating turbines are adopted as an ocean current power generator. The contra-rotating turbine system is theoretically torque free, since the second blade counters the first blade torque. Therefore, small main body and low cost mooring might be achieved. On the other hand, the motion control of the device may be necessary for a steady power supply, protection from fatigue damage of blade, and so on, because the blade size is larger than that of main body and thus the influence of unknown disturbances in the real sea is supposed to be big. In order to overcome this problem, the blade pitch control is utilized to control the motion of the device. The blade force and equation of motions are formulated and numerical simulation is performed based on these formulas to find theoretically how to change the blade pitch for motion control. A simple experiment with a scale model is also performed as the first step of the motion control. It is confirmed that it is possible to move the model perpendicular to the flow direction by the blade pitch control.