Theoretical Modeling of Magnetic Spring-Based Electromagnetic Energy Harvesters for Electrified Transportation Sensors: Analysis, Optimization, and Experimental Verification

Traditional electromagnetic vibration energy harvesters (EMVEHs) typically exhibit a low output power and operate at a single frequency. As a result, they are only capable of harvesting energy at a specific frequency from the environment, which hinders further application of EMVEHs in practice. To address this vital problem, this article proposes an enhanced magnetic spring-based EMVEH, which uses the multi-magnet structure with repelling magnetic poles to significantly improve the output power of the harvester. Complete theoretical models of the designed EMVEH are developed, which can accurately characterize the magnetic force and coil magnetic flux. In addition, magnetic field characteristics and kinematic properties of multi-magnet structures are fully analyzed. The magnets and coils are optimized based on the developed model and analysis. Meanwhile, the optimal configuration of magnets and coils is obtained by theoretical results in different cases. Experiments validate the effectiveness of the theoretical model and the optimization method. The results show that the EMF and output power have improved by 2.4 times and 5 times after optimization in case I. The EMF and output power of the optimal configuration of magnets and coils in case II have increased by 1.3 times and 2.07 times, respectively. The model developed in this article serves as a guideline to design and optimize the EMVEH with a multi-magnet structure of any volume.