Research On Vibration Energy Harvester Using Composite Magnetoelectric Transducer

Using Terfenol-D/PZT/Terfenol-D composite magnetoelectric transducer, a vibration energy harvester is presented. The harvester comprises a cantilever, magnetoelectric transducer and magnets. The magnetic circuit consists of magnets (NbFeB) and magnetic yokes (iron). Magnets (NbFeB) are installed in the free end of the cantilever (beryllium bronze).The magnetoelectric transducer consists of two Terfenol-D layers and a PZT layer. Terfenol-D layers are designated to be magnetized in their longitudinal direction, while the PZT layer is designated to be polarized in its thickness direction. Both Terfenol-D layers and the PZT layer vibrate along the longitudinal direction. The magnetoelectric transducer is located in the gap of magnets to induce the changing magnetic field. The middle of the magnetoelectric transducer is fixed in the frame.External vibration induces relative motion between magnets and the magnetoelectric transducer. The relative motion causes the magnetic field to change in Terfenol-D layers. The changing magnetic field will generate stress in Terfenol-D layers. Then the stress is transmitted to the PZT layer, which responses with a voltage.As such, the magnetoelectric effect provides a transduction method between magnetic and electric energy. The magnetic force between the magnetoelectric transducer and magnets is calculated based on the theory of equivalent magnetic charge, and the motion of magnets is researched using linzted-poincar method. According to the mean magnetic intensity in the gap of magnets, the output voltage of the harvester is analyzed.To verify the theoretical results, a ME response measure system and a harvester measure system are built up. The making procedure of Terfenol-D/PZT/Terfenol-D sample and cautions to test systems are introduced respectively. The magneticelectric voltage coefficient of the transducer is measured, and the mean magnetoelectric voltage coefficient is 64.2mV/Oe in low frequency (10-100Hz). The output voltage experiment is processed when the harvester is excited at resonant frequency. Experiment result shows an output voltage of 45.1V and an average power of 112.1μW are achieved for vibration of 5g acceleration at 33Hz. The testing result is close to the theoretical calculation. Besides, the hysteresis curve between the output voltage and the acceleration motivation is obtained because of the non-linear system and the magnetic hysteresis characteristic of magnetoelectric material. The response bandwidth of the harvester locates in low frenquency. The harvester is valued in the low-frequency vibration energy acquisition in the circumstance.