The Principle of a Three-DOF Mechanism for Wave Energy Absorption

As we all know, oceans have great wave power, and many types of wave energy converters (WECs) have been invented so far. Oscillating body systems are a major class of WECs which almost only have one degree of freedom (DOF). This paper presents a three-DOF mechanism which can extract the wave power from any wave directions. The three-DOF mechanism mainly consists of a four-bar linkage and a spherical joint, which are used to capture the heave motion and the pitch and roll motions of the oscillating body respectively. The power conversion principle of the WEC is proposed and the kinematics of the mechanism is derived. Hydraulic power take-off (PTO) systems are used, which are simplified as constant torques in this study. In the end, the power absorption performance of the WEC is presented based on the system dynamics. The results show that the rated power output of the WEC is 4.3MW, and the power output of the WEC is dependent on the wave directions.