Piezoelectric Energy Harvester Array With Magnetic Tip Mass

Energy harvesting using piezoelectric materials is an alternative method for low power electronics, such as MEMS, wireless sensor network, portable devices, and nano structures, from extracting the ambient energy. Most piezoelectric energy harvesters are based on cantilever beams with laminated piezoelectric patches. To generate higher dynamic response of piezoelectric energy harvesters, tip mass is attached at the free end of the cantilever beams. Piezoelectric energy harvester array is another way to improve the power, i.e., installing a set of cantilever piezoelectric energy harvesters in close distance. In this research, a new design of piezoelectric energy harvester is proposed. The present design consists of an array of cantilever beams with permanent magnets at the free ends. The permanent magnets are introduced to transfer the excitation force to every cantilever beams. An experimental model is manufactured and experimental energy harvesting is carried out. Piezoelectric patches are laminated on clamped end of cantilever beams, and the permanent magnets are fixed at the free ends. All the magnets have opposite poles with each other to generate repelling force. Then these piezoelectric electric energy harvesters were connected to an AC/DC circuit and the power was measured. Also, the power of proposed piezoelectric energy harvester was compared with the piezoelectric harvesters without permanent magnets. The results show that, present design can generate higher power at the same excitation. Under the base excitation at the first natural frequency, the array of the cantilever beam show similar motion pattern, i.e., there is no phase difference between each other. At higher frequencies, the beams have a phase difference of π. Thus the crash between the cantilever beams can be effectively avoided. At lower excitation frequencies, the presented piezoelectric energy harvester vibration likes the first mode of a simple multi-degree-of-freedom system; and at higher excitation frequencies, the vibration of the presented piezoelectric vibrates like a second mode of a MDOF system.