Research On Efficient Energy Harvesting Technology Of Piezoelectric Wideband Vibration

In response to the defects of traditional chemical battery power supply,it is possible to recover energy from the environment instead of traditional batteries to power low-power devices.The vibration energy in the environment has the characteristics of universality and easy conversion.Piezoelectric vibration energy collection method is suitable for the collection process of vibration energy in different environments because of its distinguished feature of simple structure and high conversion efficiency.This paper studies the efficient collection technology of piezoelectric wideband vibration energy.A sensor-less wideband active self-tuning piezoelectric energy harvester(AST-PEH)is proposed in this thesis,which is composed of a piezoelectric cantilever beam,a screw rod,a miniature stepper motor,a T-section mass and an energy harvesting and control circuit(EHCC).The miniature motor is applied to actively shift the position of the T-section mass according to the detecting of the resonant state of AST-PEH,making a match between the resonant frequency of AST-PEH and the ambient vibration frequency,widening the operation frequency range of the AST-PEH.After the dynamic analysis to the AST-PEH structure,the expression of the AST-PEH’s resonant frequency function is constructed.Then the simulation verification is completed by the use of software ANSYS and MATLAB.Wideband characteristics of two different substrate material prototypes of steel and polylactic acid are tested,and the former is also tested for load power characteristics.The experimental results show that the operation frequency range of the two type AST-PEH are 4.8Hz-6.3Hz and 8.17Hz-14.3Hz,respectively,and the widening rate of the operation frequency are 31.25% and 75% respectively.The maximum output power tested of steel type AST-PEH is 0.32 m W at 6.3Hz under 0.32 g acceleration with a 100 KΩ load resistance.Designed the energy harvesting and control circuit(EHCC).A new method and circuit are proposed for on-line dynamic detection of the piezoelectric transducer(PZT)without any additional sensors.Based on the theoretical analysis,the expression of the phase difference relationship between Open Circuit Voltage Signal(OCVS)and Short Circuit Current Signal(SCCS)is derived.Just by detecting the phase difference between OCVS and SCCS,the resonant state of AST-PEH and frequency deviation between the resonant frequency and the current ambient vibration excitation frequency can be obtained.The experimental result shows that the EHCC can realize the goal of self-tuning and energy harvesting.When the AST-PEH is in the resonant state of 5.2Hz and the PZT open circuit voltage is 9.5V,the extraction power is 0.36 m W,and the extraction efficiency is 84.8%.Energy supply characteristic test of AST-PEH is carried out,taking the detection and transmission of ambient temperature and humidity data as an example.The test results present that the minimum standby power consumption of the system is 2.64μW,and when the working time of miniature stepper motor is 0.2%,the power consumption is 8.5m W and the power dissipation is 0.3μW while shift the position of T-section mass.Based on the analysis of the maximum extraction power of 0.36 m W during the test,it can be concluded that the energy collection efficiency of this system is highly efficient and the energy harvested by AST-PEH can meet the power supply demands of the low-power Wireless Sensor Networks(WSN)modules.