A multi-directional broadband piezoelectric-electromagnetic-magnetic coupling compound energy harvester for vibration energy harvesting applications

Currently, common vibration energy harvesters can only capture vibration energy in a unidirectional or fixed plane, posing issues such as high collection frequency, limited frequency range, and low output power. This paper proposes a multi-directional broadband piezoelectric-electromagnetic-magnetic coupling composite vibration energy harvester. It achieves three-directional energy harvesting while broadening the harvesting frequency and having a higher power density compared to current state-of-the-art research. Comprising a piezoelectric system and an electromagnetic system, the harvester leverages theoretical analysis to design the piezoelectric cantilever beam with a branching structure, enhancing its broad frequency characteristics. In addition, the magnetic coupling effect is added to the device so that the cantilever beam in three directions can work when the device receives unidirectional vibration excitation. Building on theoretical analysis, the COMSOL 5.6 software is utilized to conduct simulation analysis and optimize the size of the designed piezoelectric cantilever beam structure. This process validates theoretical analysis accuracy and improves energy capture capability. To confirm device viability and simulation accuracy, a physical model is fabricated, and vibration tests are executed. The energy harvester generates two peaks (10 Hz, 27 Hz) when vibration excitation is applied, which effectively broadens the collection frequency. Under the vibration frequency excitation in the X and Y directions, the total composite output power of the multidirectional broadband piezoelectric-electromagnetic-magnetic coupling composite vibration energy harvester is 17.72 mW and 30.22 mW, and the power density can reach 32.85 mW·cm⁻³, which significantly strengthened the captured energy efficiency of the energy harvester compared with the energy harvester without magnetic coupling, with the total composite output power increased by 352.0% and 165.8%, respectively; under the excitation of the Z-direction vibration frequency, the total composite output power was 42.42 mW and 44.80 mW, and the power density could reach 48.70 mW·cm⁻³.