Abstract
In this paper, motion performance of a miniaturized spar-buoy with a ring-fin motion stabilizer comparing with the previous studied the same type spar-buoy is experimentally investigated and compared with the performance of the previous studied large size spar-buoy[2], and they are confirmed that its pitch amplitude increases at the same wave period or the same wave height, and its maximum pitch amplitude may not change much, moreover, the tendency is not related to the mooring system or water depth.
Moreover, it is investigated to reduce its pitch amplitude further. By placing the Doppler Lidar on a rigid body swing as a motion stabilized platform and constructing an active control that keeps the Doppler Lidar upright using a reinforcement learning, the motion of the sensor itself is reduced and the accuracy of measurement is improved.
Numerical simulations are conducted using the motion data of the spar-buoy in regular and irregular waves measured by scale model tests, and it is confirmed that it is possible to reduce the motion of the Doppler Lidar itself by adjusting the control gain of the motion stabilized platform by using a constant damping coefficient or the variable damping coefficients decided by the skyhook damper theory In order to reduce the motion further, an external force cancellation control using the motion of the spar-buoy in irregular waves simulated by the supervised machine learning is also applied.
