Study On Piezoelectric Vibration Energy Harvester With Doubly Clamped Beams

With the development of microelectronic device,the requirement of energy supply is higher and higher,and the piezoelectric vibration energy harvesting technology has been widely concerned in the wireless sensor network node,the electronic equipment and the portable electronic products.The point of the research on piezoelectric vibration energy harvesting technology is to improve the output of electric power based on matching the vibration frequency of working environment.Among of the piezoelectric energy harvesters produced by MEMS process,increasing the size and using the new structure can improve the output voltage.Based on the above situation,many scholars began to pay attention to the MEMS process,output voltage performance and vibration characteristics of the energy harvester's new structure at centimeter level.In this paper,a kind of energy collector with doubly clamped beams is designed.We studied its mechanical properties and vibration characteristics and derived an optimization method for the stress and the first order natural frequency of doubly clamped beams.The stress and the first order natural frequency of the cantilever beam and the doubly clamped beam structures were analyzed and compared by using ANSYS simulation software,and then the first four order modes of the device were analyzed.The device was fabricated by MEMS process.After that the performance of PZT film,mechanical properties,the static,dynamic and output performances of the device are tested.X ray diffraction(XRD)analysis shows that the PZT film was completely transformed into perovskite structures.The test results of atomic force microscopy(AFM)show that the average diameter of grain is 54.21 nm,and the average height is 0.679 nm.The four probe semiconductor parameter measuring instrument test the films and it's results suggest that the leakage current is always less than 4.18 nA under the influence of voltage from 0 to 30 V.The LCR tests show that the variation range of the capacitance value is from 18.1nF to 21.3nF,the dielectric loss is in the range of 0.02 to 0.06,and the relative dielectric constant is in the range of 1525 to 1793 under the sinusoidal voltage with frequency from 50 to104 Hz and the value of 1V.The ferroelectric properties show that the remanent polarization strength(Pr)is 10.691 ?C/cm2,and the coercive field strength(Ec)is 20.556KV/cm.In the follow-up work,the test result of the static,dynamic and output performances indicate that the vibration can exhibit nonlinear hard property.The damping ratio is 0.0157.In different vibration intensities,the beam's test results of NO.1 show that the greater the vibration intensity lead to the higher the open circuit peak voltage and the wider operating bandwidth of the device.When the actual vibration acceleration is 6.84m/s2,the open circuit peak voltage reach the maximum value94 mV,and-3dB bandwidth is 56 Hz.Moreover,the first order modal simulation value(284.557Hz)of the device is similar to the frequency(from 275 to 300Hz)at which the open circuit peak voltage begins to increase.The closed-loop output performance test results of No.2 beam show that the maximum load power is 182.5nWand the optimum load resistance is 15 Kwhen the actual excitation acceleration peak is 4.91m/s2.