Study On Piezoelectric Generators For Low-frequency Vibration Harvesting

As people pay more attention to environmental problems and the new energyresource, eco-friendly energy harvesting technology has becoming more and morepopular; meanwhile, with the development of integration for semiconductordevices as well as the progress of MEMS technology, it is possible to convert thevibrational energy into electrical energy which is the power supply formicroelectromechanical system. But because the frequency of vibration energy inthe natural environment and human life is low, and the bandwidth is wide, thetraditional technology of piezoelectric vibration energy harvesting is inefficient.Because of this, this paper is based on the piezoelectric effect, presents a vibrationgenerator with impact load, deduces the theoretical formula and simulates thisdevice via MATLAB; this paper also presents a piezoelectric frequency increasedstructure with variable stiffness, because this structure is able to amplify theamplitude of the piezoelectric ceramic, and then to gain maximum power output.In this paper, the main research contents and conclusions are as follows:1) According to the mechanical vibration theory and collision theory, thetraditional vibration energy scavenging device is modified, and a piezoelectric impact vibration generator in low frequency vibration environment is designed.The first collision calculation model is established, and on the basis of this, theanalytical expressions of output voltage and power are deduced and the pick-upis optimized by using the MATLAB, after that, the corresponding structureparameters are obtained. Then based on these structure parameters, the simulationmodel of this piezoelectric vibration generator is established in the AMESimsimulation platform, and the performance of this generator is analyzed based onsome influence factors such as the excitation frequency, the mass of oscillator,and the number of piezoelectric patches.2) The structure of a piezoelectric frequency up-conversion generator withvariable stiffness is designed, and the differential equation of motion of thismechanism is established, then using the AMESim simulation platform tosimulate this model. This model is analyzed by using different variable stiffnesssprings with two different stiffness curves. The performance of the linear system,the constant stiffness up-conversion system, and the variable stiffness up-conversion system are compared. As a result, compared with other two kinds ofconventional generators, the frequency up-conversion generator with variablestiffness performs better in low frequency vibration environment, it broadens thefrequency response band and increases generated output.In order to improve the capture ability of low-frequency vibration energy, apiezoelectric vibration generator with impact force is presented, and the peakpower of this optimized generator is4.4mW, and the power generated in10s is 68.25mJ. Meanwhile, based on a piezoelectric frequency up-conversion generator,a piezoelectric frequency up-conversion generator with variable stiffness ispresented, the frequency range of this modified vibration harvester is widened by15％for the generator with constant stiffness springs and the peak power of thisgenerator is7mW.