| With the wide popularization and application of microelectronic technology and communication technology,the energy supply demand of wireless sensors and microelectronic devices is becoming more and more significant.Due to the size and weight,maintenance and replacement,environmental pollution and other problems,the energy supply equipment represented by traditional chemical battery can not effectively meet the long-term and reliable energy supply requirements of wireless sensor networks.In this context,the environmental energy harvesting technology represented by piezoelectric vibration energy harvesting becomes the research focus.On the basis of previous research on piezoelectric vibration energy harvesting technology,aiming at the problem of low energy harvesting efficiency in low frequency range and low excitation level,based on the M-shaped beam vibration energy harvesting device,a new type of nonlinear M-shaped beam piezoelectric energy harvesting device and a new type of buckling M-shaped beam piezoelectric vibration energy harvesting device are proposed,The relevant theoretical and simulation analysis and experimental research are carried out.The main research contents are as follows:1.Based on the basic principle of piezoelectric vibration energy harvesting technology,the lumped parameter model of the original M-shaped beam structure and the equivalent dynamic equation of the system are analyzed.2.Based on the original M-shaped beam,an improved M-shaped beam piezoelectric vibration energy harvesting device is proposed,which introduces nonlinear magnetic force into the original system by adding an external magnet.The dynamic model of the improved M-shaped beam piezoelectric vibration energy harvesting system is established,and the electromechanical coupling equation of the system is derived.MATLAB software is used to simulate the output voltage response under up-sweep excitation.Moreover,an experimental platform is built to test the output performance of the M-shaped beam piezoelectric vibration energy harvesting device and the improved M-shaped beam piezoelectric vibration energy harvesting device.The experimental and simulation results show that the introduction of external nonlinear magnetic force can broaden the working frequency band of M-shaped beam vibration energy harvesting device,and the effect is enhanced with the decrease of magnet spacing.Compared with the system without additional magnet,when the distance between the magnet and the beam is 35 mm and the acceleration is 0.5g,the working frequency band of the additional magnet system is broadened by 32%.3.A new type of buckled M-shaped beam piezoelectric vibration energy harvesting device is proposed.Based on the theory of bistable nonlinear system,the dynamic models of the buckled M-shaped beam and the buckled M-shaped beam with additional magnet are established.The effects of nonlinear external magnetic force on the nonlinear restoring force and potential well of the bistable system are analyzed.MATLAB software is used to simulate the dynamic characteristics of the buckled M-shaped beam,and the output voltage response of the system under up-sweep frequency external excitation is analyzed.In addition,an experimental platform is built to test the dynamic response of the buckled Mshaped beam under up-sweep frequency excitation,and the frequency response of the improved M-shaped beam and the new buckled M-shaped beam under continuous constant excitation is also tested.The experimental and simulation results show that the buckled Mshaped beam piezoelectric vibration energy harvesting device can effectively broaden the working frequency band under low acceleration excitation level,has better low-frequency energy harvesting performance,and improves the amplitude of output voltage.In addition,when the excitation level is 0.15 g,the bistable inter-well oscillation can be excited,so that the system has good output response in the ultra-low frequency range(< 5Hz)and low excitation level(0.3g and 0.5g).When the distance between the magnet and the beam is40 mm,the system bandwidth of the additional magnet is increased by 12.7% and 12.2%compared with that of the flexure M-shaped beam without additional magnetic force. |
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