**A Piezo-Electromagnetic Coupling Multi-Directional Vibration Energy Harvester Based on Frequency Up-Conversion Technique**

**Ge Shi 1,\*, Junfu Chen 1, Yansheng Peng 1, Mang Shi 1, Huakang Xia 2, Xiudeng Wang 2, Yidie Ye 2 and Yinshui Xia 2**


Received: 16 December 2019; Accepted: 8 January 2020; Published: 11 January 2020

**Abstract:** Harvesting vibration energy to power wearable devices has become a hot research topic, while the output power and conversion e fficiency of a vibration energy harvester with a single electromechanical conversion mechanism is low and the working frequency band and load range are narrow. In this paper, a new structure of piezoelectric electromagnetic coupling up-conversion multi-directional vibration energy harvester is proposed. Four piezoelectric electromagnetic coupling cantilever beams are installed on the axis of the base along the circumferential direction. Piezoelectric plates are set on the surface of each cantilever beam to harvest energy. The permanent magne<sup>t</sup> on the beam is placed on the free end of the cantilever beam as a mass block. Four coils for collecting energy are arranged on the base under the permanent magnets on the cantilever beams. A bearing is installed on the central shaft of the base and a rotating mass block is arranged on the outer ring of the bearing. Four permanent magnets are arranged on the rotating mass block and their positions correspond to the permanent magnets on the cantilever beams. The piezoelectric cantilever is induced to vibrate at its natural frequency by the interaction between the magne<sup>t</sup> on cantilever and the magnets on the rotating mass block. It can collect the nonlinear impact vibration energy of low-frequency motion to meet the energy harvesting of human motion.

**Keywords:** piezo-electromagnetic coupling; up-conversion; vibration energy harvester; multi-directional vibration; low frequency vibration
