Investigation On Flapping-hydrofoil Wave Energy Harvest Technology For Small Ocean Vehicles

Small ocean vehicles like AUVs,as mobile platforms in the ocean,have a broad application prospect in marine-related areas.The power source mainly relys on batteries,which limit the endurance and seriously restrict the operating radius,so the problem of energy supply is one of the hotspots in the research of AUVs.Wave energy has a great potential,without time and space constraints,different from other existing new energy applications.But the research on wave power technology of small ocean vehicles is not mature.Traditional study assembles wave energy converter inside of the vehicle's hull,in which way the power generated is limited.To solve the issue of energy supply for small ocean vehicles,this paper proposes a novel flapping-hydrofoil method,harnessing the ocean wave energy to generate power,expected to satisfied the requirements of long-time navigation,long-distance voyage,and multi-task operation,to extend the time of autonomous operation.Based on the theory of mechanical vibration,wave power technology of the flapping-hydrofoil method is analyzed from the perspective of the vibration energy harvest.The 3-DOF forced vibration model of the flapping-hydrofoil wave conversion system is established,including the power generation mass and the vehicle.Considering the spatial distribution of the wave force,numerical computation method is adopted to study the dynamics process and compute the theoretical maximum power.The results show that the flapping-hydrofoil method has a greater potential in power conversion,compared with the traditional inertial driven wave energy vibration harvest method.Then the concrete structure of the flapping-hydrofoil wave energy conversion system is designed and the mock-up is built.Torpedo shape is adopted for the ocean vehicle's body,on both sides of which,mounted hydrofoils like two wings,which is respectively fixed connected with a transmission shaft.Utilizing the difference of the hydrodynamic response of the wings and the hull,the wings flap along with the undulations of waves up and down to capture the wave energy which is then transmitted into the internal rotational power converter.The electricity generated will be stored into storage battery cells.SolidWorks as a three-dimensional modeling software is used to design the whole structure of the flapping-hydrofoil wave energy conversion system.Based on the structure designed,a mock-up of the wave energy converter is built for the experiment research followed.Experimental research is done for the flapping-hydrofoil wave harvest method based on the mock-up built.A dry-type experimental platform is established for the test of wave conversion,including a motor motion control system which controls a servo motor and a belt drive mechanism to drive the wings up and down to simulate the wave conversion state,and a data acquisition system in which,a sensor and an analog input module are used to collect power parameters.Also,a matched testing system software is developped based on C # language to control the motor and record the experiment results.Then power conversion experiment of the flapping-hydrofoil wave energy converter is done under the condition of sea state 2,utilizing the dry-type experimental platform.Results show that the average power generated is consistent with the range of the theoretical calculation,but the overall power is relatively lower due to many factors.