PiezoMEMS Nonlinear Low Acceleration Energy Harvester with an Embedded Permanent Magnet

Abstract

Increasing the power density and bandwidth are two major challenges associated with microelectromechanical systems (MEMS)-based vibration energy harvesting devices. Devices implementing magnetic forces have been used to create nonlinear vibration structures and have demonstrated limited success at widening the bandwidth. However, monolithic integration of a magnetic proof mass and optimizing the magnet configuration have been challenging tasks to date. This paper investigates three different magnetic configurations and their effects on bandwidth and power generation using attractive and repulsive magnetic forces. A piezoMEMS device was developed to harvest vibration energy, while monolithically integrating a thick embedded permanent magnet (NdFeB) film. The results demonstrated that repulsive forces increased the bandwidth for in-plane and out-of-plane magnetic configurations from <1 to >7 Hz bandwidths. In addition, by using attractive forces between the magnets, the power density increased while decreasing the bandwidth. Combining these forces into a single device resulted in increased power and increased bandwidth. The devices created in this paper focused on low acceleration values (<0.1 g) and low-frequency applications.

Wide Bandwidth Vibration Energy Harvester with Embedded Transverse Movable Mass

“…The lightweight PLA was used to reduce the mass of the stationary proof mass to ensure that the wt.% of the movable mass was high. The dimensions of the proof mass and cantilever are scaled up versions of typical microsystem energy harvester devices [1,15,38]. The 3D printed proof mass consisted of three 11 mm diameter hollow chambers along the width of the cantilever, designed to restrict the 10 mm diameter spheres from rolling in the lateral direction.…”

“…Since bandwidth is one of the major challenges associated with vibration energy harvesting, it was extensively investigated. Previous attempts to solve this issue have included developing non-linear cantilevers and spring designs based on duffing resonators [7][8][9][10], impact driven mechanical stoppers [11][12][13], additional magnetic forces [14][15][16], bistable non-linear devices [17][18][19], and the designing of an array of devices with varying frequencies [4]. However, these methods have numerous disadvantages, such as hysteresis effects, which depend on frequency sweep testing protocol, low power density, as decreasing the Q-factor reduces the peak power harvested, a larger footprint, thus decreasing the overall power density, complex manufacturing, especially at the micro-scale, and the need for external power, which reduces the overall efficiency of the system.…”

Theoretical and experiment optimization research of a frequency up-converted piezoelectric energy harvester based on impact and magnetic force

“…Magnetic force is another nonlinear force that is used to widen the frequency band of VEH, Samuel C. Stanton et al [25] is one of the first research groups to propose nonlinear magnet VEH model which can accurately predict the motion characteristics and power generation performance of the magnet VEH, the numerical prediction and experimental verification results show that the traditional cantilever beam can realize the frequency broadening effectively after the introduction of magnetic force. On this basis, a variety of new structures using nonlinear magnetic force to achieve broadband energy harvesting have been proposed and studied, which greatly promoted the practical process of broadband capture energy of VEH [26][27][28][29][30][31][32]. In addition to the introduction of magnetic force to nonlinear broadening of the frequency band, some scholars can also realize the broadening of the frequency band by using variable mass to generate nonlinear dynamics.…”

Passively Tuning the Resonant Frequency of Kinetic Energy Harvesters Using Distributed Loaded Proof Mass

“…MEMS energy harvesters typically have a narrow bandwidth (1-3 Hz) as they need a high Q factor to increase power density, but a narrow bandwidth prevents the device from being used in applications with varying resonant frequencies. Researchers have investigated numerous methods to increase bandwidth using non-linear dynamics [12][13][14], creating an array of devices with different frequencies [6,15] and movable mass [16][17][18][19][20][21][22][23], and using repulsive and attractive forces to slow or accelerate the cantilevers' dynamics [24][25][26][27]. However, most of these methods either significantly decrease the power generated or they only slightly increase bandwidth to cover resonate frequency errors due to manufacturing.…”