Natural frequency self-tuning energy harvester using a circular Halbach array magnetic disk

A novel natural frequency self-tuning energy harvester is presented, which utilizes the presence of the nonlinearity model and the well-weighted swing disk to maximize the power output and the frequency bandwidth for a wheel rotating at any speed. Kinetic energy harvesters are frequency selective, meaning that they have high power transmission efficiency only when they are excited at their natural frequency. The well-weighted swing disk with nonlinear effects can render the energy harvester more broadband, that is, it has a more steady power generation at various wheel speeds than the ill-weighted swing disk has. We integrate magnets in a novel circular Halbach array and coils into the design to augment the magnetic strength on one side of the array where the coils are placed. Therefore, the gradient of the average magnetic flux density for the circular Halbach array disk is larger than that of the multipolar magnetic disk. The dynamic models with electromechanical couplings have been established and are analyzed. In the experiments, the power output of the prototype at an optimum external resistance was approximately 300–550 µW at about 200–500 rpm and precisely matches the numerical results.