Design and construction of high efficiency magnetostrictive energy harvester for huge and short-time impact vibration systems

Abstract

Vibration energy harvester can turn the mechanical energy into electric energy, always used to supply sufficient power for wireless devices. Self-powered sensor nodes with smart structure (piezoelectric and piezomagnetic harvester) that utilize environmental vibration energy to meet the dynamic power requirement, have abroad application in structural health monitoring. Today, piezoelectric mechanism is using popular in vibration energy harvesting technology, various structures of piezoelectric energy harvesters are proposed for Self-powered systems, but it is still lack of piezoelectric vibration energy harvester can be using in the situation of huge and short-time impact systems, such as huge instantaneous impact vibration of human or vehicle activities on walking platform, highway and bridge, railway rail, etc. Consider its piezomagnetic effects, Mag-netostrictive materials, such as TbDyFe alloy and FeGa alloy, are more suitable to design vibration energy harvester in application of huge and short-time impact with high electric power output. Using magnetostrictive materials to develop power generating floor systems have received more attention, but still under development, its harvesters are accompanied by low power density. Mag-netostrictive/electromagnetic hybrid configuration shows relatively high power density and efficiency, especially in the huge transient impact situation. Furthermore, structure of magnetostrictive/ electromagnetic combination can leads to both stress load and magnetic field changes in magneto-strictive materials with environmental impact, and its harvester will generate more electric power. This paper presented the design and construction of a vibration energy harvester based on magne-tostrictive material, which consists of one coil-wound Terfenol-D rod with a PM and air-gap in its each magnetic circuit, and the PM array on the part of cap amplifier, its structure shows in Fig.1. In this structure, the axial height of cap amplifiers changes in the action of environmental impact, leads to width of air-gap increase, induces the magnetic field in Terfenol-D declines, which can help to enlarge changes of magnetic induction in Terfenol-D rod, and its harvesting effect introduced in Fig.2. Modeling and simulation are used to validate and optimize the concept. Relation of magnetic field in Terfenol-D rod with differ principal design parameters is derived, its uniformity and intensity are analyzed, magnetic circuit configuration is optimized. Then, principal design parameters of the harvester, width of air-gap and cap amplifiers are optimally determined, and its static analysis of harvesting effect is undertaken. Last, a prototype has been constructed and tested. The magnetostrictive-based vibration energy harvester can generate V/W magnitude induced voltage and power generation, larger than conventional smart harvester, can be safely used in the transient impact up to 20–30MPa.