In order to solve the problem that when the piezoelectric cantilever generator captures the lowfrequency vibration, the structural resonance frequency bandwidth is small and the generating capacity cannot be fully developed. A magnetic excitation cantilever-type piezoelectric energy harvester for rotational motion was presented in this paper. Energy harvesting capability of resonant harvesting structures, such as piezoelectric cantilever beams, can be improved by utilizing coupled oscillations that generate favorable strain mode distribution. The theoretical analysis and simulation analysis of the working state of the piezoelectric energy harvester is performed. The power generation performance of magnetic excitation cantilever-type piezoelectric energy harvester under different environmental excitations was tested by experimental methods. The experimental results show that the magnetic excitation cantilevertype piezoelectric energy harvester has the best power generation performance when the rotational speed is 150 r min −1 , the installation angle of the piezoelectric cantilever is 60°, the distance between the mass magnet and the excitation magnet is 8 mm, and the number of excitation magnets is 6. The maximum open-circuit voltage of the magnetic excitation cantilever-type piezoelectric energy harvester is 38.49 V. When the load resistance is 40 KΩ, the magnetic excitation cantilever-type piezoelectric energy harvester has a voltage of 24.84 V and an average power of 15.425 mW. Piezoelectric energy harvesting is an attractive technique for the potential powering of wireless sensors and low power devices.

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In the field of controlled drug delivery system, there are still many problems on those reported micro-valves, such as the small opening height, unsatisfactory particle tolerance and high cost. To solve the above problems, a novel normally-closed piezoelectric micro-valve is presented in this paper. The micro-valve was driven by circular unimorph piezoelectric vibrator and natural rubber membrane with high elasticity was used as the valve stopper. The small axial displacement of piezoelectric vibrator can be converted into a large stroke of valve stopper based on hydraulic amplification mechanism. The experiment indicates that maximum hydraulic amplification ratio is up to 14, and the cut-off pressure of the micro-valve is 39kPa in the case of no working voltage. The presented micro valve has a large flow control range (ranging from 0 to 8.75mL/min).

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Abstract:A piezoelectric vibration feeder with a magnetic spring is discussed in this paper. The feeder can keep resonance frequency relatively stable under changing loading. Through the analysis on the working principle and magnetic spring stiffness characteristic of this feeder, the dynamic model was established and the relationship among system resonance frequency, loading and magnetic spring stiffness was obtained. The analysis showed that, as the loading changed, the magnetic spring stiffness changed accordingly, which maintained a trend of stability in the system resonance frequency. A prototype was made for the experiment, and the relationship among the loading, magnetic spring axial clearance and system resonance frequency was obtained. The result showed that, when the loading changes, the resonance frequency and feeding speed tended to be stable, which matched the theoretical analysis. Through comparison with a traditional vibration feeder, within nominal loading, this new feeder has more stable resonance frequency and feeding speed.