# Modeling and Test Results of an Innovative Gyroscope Wave Energy Converter
###### Abstract  
An improved Maximum Power Point Tracking (MPPT) method based on a purely mechanical wave energy converter (WEC) of gyroscope precession is proposed. The method adopts dynamic perturbation step adjustment, which improves the stability of power output and reduces steady-state oscillation. The paper introduces the principle of the device, establishes the mathematical model, and obtains the complete expression of power. The effect of wave frequency, pitch amplitude, power take-off (PTO) damping coefficient, and flywheel rotating speed on power output is analyzed. The output regression equation is established, and the extraction conditions of the maximum power are summarized and predicted. Aiming at the time-varying nature of actual ocean waves, a variable step size modified maximum power point (MPP) tracking control algorithm based on perturbation and observation (P&O) method is proposed. The algorithm has a unique technology to dynamically change the perturbation size, which not only improves the dynamic response but also reduces the oscillation. Besides, the boundary conditions ensure that the algorithm will not deviate from the motion trajectory, and the average filtering method and steady-state judgment can further reduce steady-state oscillation. In various ocean conditions, the proposed method has better output stability compared with other variable step size algorithms. Finally, different wave working conditions are given in the experiment, and the results verify the effectiveness of the proposed MPPT control strategy in experimental equipment. The device will be suitable for distributed power sources in small islands and ports. gyroscopic power take-off; wave energy converter (WEC); wave power; maximum power point (MPP) tracking (MPPT); modified adaptive perturb and observe (P&O)  
14 April 2021 8 May 2021 11 May 2021  
**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. **Key words:** **MQP1**, **MQP1**, **MQP2**, **MQP3**, **MQP4**, **MQP5**, **MQP6**, **MQP7**, **MQP8**, **MQP9**, **MQP10**, **MQP11**, **MQP12**, **MQP13**, **MQP14**, **MQP15**, **MQP16**, **MQP17**, **MQP18**, **MQP19  
based on the relative movement between the components, such as the oscillating water column. The third type uses a high-speed rotating rotor to store a substantial amount of energy as kinetic energy (flywheel effect--the Wells turbine) [11]. In all kinds of WECs, point absorbers [12,13], oscillating water columns [14,15], and flaps [16] have become the most common devices in the wave energy field. However, some issues still need to be resolved, such as the survivability of the equipment, environmental pollution (if a hydraulic conversion system is used), the economics of energy extraction, and power output stability [17,18]. The WECs work in extreme environments, for example, Toftesfallen, Norway, built equipment in 1985, but it was severely damaged in 1991, which means higher technical requirements and a more advanced structure. Since then, researchers have made a lot of attempts, but still cannot avoid the damage of WECs. The most famous is the Aguadoura wave farm in Portugal, the first wave farm in the world that integrated three types of Pelamis equipment, which stopped its operation after two months [19]. Besides, in hydraulically driven WECs, hydraulic oil leakage caused by loss of lubrication, wear, and other factors will cause irreversible damage to the marine environment [20]. According to the global wave energy atlas proposed by [PERSON] [21], deep waters (40\({}^{\circ}\)-60\({}^{\circ}\) N and 40\({}^{\circ}\)-60\({}^{\circ}\) S) have abundant wave energy resources (70 kW/m) [22], and the energy density will decrease as the waves approach the coast, so it is appropriate to install WECs in deep water.