AN ULTRA-LOW FREQUENCY ELECTROMAGNETIC VIBRATION ENERGY HARVESTER WITH WATT-LEVEL OUTPUT DRIVEN BY THE HELICAL CLUTCH FREQUENCY-UPGRADING MECHANISM

At present, most energy harvesters can only collect less energy from low-frequency motion, with low energy collection efficiency. Low power generation under low-frequency excitation is becoming the key issue that currently limits the application of electromagnetic energy harvesters in multiple scenarios. Electromagnetic induction power generation, as a widely used and mature power generation technology, has higher power output and is widely used in the field of energy harvesting, which is expected to solve this technical bottleneck. This paper proposes an electromagnetic vibration energy harvester based on a helical clutch transmission system to systematically solve the problem of low output frequency of the energy harvesting and short conversion time. The mechanical transmission system of the harvester is composed of three parts: a linear-rotation conversion module, a helical clutch module and an energy storage/release module, which can convert external low-frequency and irregular instantaneous excitations (about 0.2 ~ 5 Hz) into high-frequency, continuous unidirectional rotational motions to maximize energy conversion efficiency. An electromechanical coupling dynamics model was established for the proposed energy harvester and verified by experiments. The results show that the energy harvester can realize the output of the open circuit state for up to 30 s under the external pulse excitation; the maximum rotational speed of the inertial rotation motion after connecting the load can reach 750 r/min, and the motion frequency can achieve a nearly 300 times improvement from 0.17 ~ 50 Hz. the peak power of a monolayer power generation module can reach 1.25 W, and that of bilayer power generation modules connected in parallel can be 2.5 W, which can achieve an average power of 134 mW. In addition, its compact and efficient transmission structure design enables the energy harvester to be further integrated into wearable devices, which is of great significance in the field of human energy harvesting and the construction of self-powered IoT sensor nodes.