Design of a piezoelectric energy harvester based on the liquid-solid-magnetic multifield coupling effect

With the development and application of microelectromechanical systems (MEMS), their need for environmentally friendly and reliable energy supply is becoming increasingly prominent. Environmental vibration as a common energy source in life is highly consistent with the energy supply needs of MEMS. Among them, piezoelectric vibration energy harvesters have been studied by a large number of scholars because of their simple conversion structure, high efficiency, low heat generation, and easy processing and integration. At present, how to make piezoelectric vibration energy harvesters having a higher energy harvesting efficiency and a wider energy harvesting frequency band is one of the research hotspots of scholars.

In this paper, we take a liquid-solid-magnetic multifield coupled piezoelectric vibration energy harvester as the research object and establish its mechanical model. Through experimental test and parameter analysis, the output characteristics of the energy harvester and the influence of each parameter on the energy harvesting efficiency are obtained, verifying the feasibility of the energy harvester and providing a reference for the design of new types of energy harvesters.

A new liquid-solid-magnetic multifield coupled piezoelectric vibration energy harvesting structure is proposed, in which the proof mass of a traditional cantilever energy harvester is replaced by a liquid-filled container with ferromagnetic fluid and permanent magnets of different positions and distances are arranged around it. Based on the energy method, the lumped parameter model of the liquid-solid-magnetic multifield coupled piezoelectric vibration energy harvester is established. Subsequently, the expressions for the nonlinear magnetic force and the sloshing force are deduced using the magnetic dipole method and the potential flow method, and the mechanical model of the liquid-solid-magnetic multifield coupled piezoelectric vibration energy harvester is obtained. Then, a liquid-solid-magnetic multifield coupled piezoelectric vibration energy harvester is designed and manufactured, and the related experimental test system is built. The output of the energy harvester is tested under harmonic excitation and random excitation for sloshing and magnetic force variables. Experimental results show that sloshing can make the energy harvester exhibit a multipeak response and that the addition of a nonlinear magnetic force changes the resonant frequency of the energy harvester and affects the sloshing in the container-based energy harvester, which will change the output characteristics of the energy harvester. By choosing the appropriate liquid, the height-to-diameter ratio, and the appropriate magnet position and distance, the energy harvesting efficiency of the energy harvester will be effectively enhanced and the feasibility of the liquid-solid-magnetic multifield coupled energy harvester is verified.

Based on the theoretical model and experimental tests, the parameters of the liquid-solid-magnetic multifield coupled piezoelectric vibration energy harvester are investigated. The effects of the structural parameters of the energy harvester, sloshing parameters, and magnetic parameters on the output characteristics of the energy harvester are further investigated, which provides a reference for the design optimization of the liquid–solid–magnetic multifield coupled piezoelectric vibration energy harvester.