Suboptimal Control of a Rack and Pinion Based Wave Energy Converter Power Take-off System

In this paper, an effective control method of using a rack and pinion type power take-off system is discussed, and the performance of the whole system is analyzed. The bidirectional motion of the pinion is converted into unidirectional motion by applying the ratcheting method. This increases the overall efficiency of the system. A wave energy converter containing a buoy and a mechanical motion rectifier (MMR) based rack and pinion mechanism are designed and simulated in MATLAB Simulink environment. This system consists of a buoy that is semi-submerged into the water. The ocean waves exert force on the submerged buoy. The up and down movement of the buoy is then converted into unidirectional rotation by rack and pinion mechanism. Through a gearbox, this rotational motion drives the generator to produce electricity. The control strategy keeps the generator's velocity and waves excitation force in resonance. Time-domain system analysis is applied for solving the equation of motion that describes the relationship between the buoy motion and hydrodynamic forces with regular waves. The simulation results for the regular ocean waves are presented and compared with another state-of-the-art power take-off system.