Design And Study On Energy Harvesters Using Bridge Vibration

As a kind of infrastructure,bridge is playing an increasingly important role in daily life.The layout of bridge health monitoring system is an important means to ensure the normal operation of bridges,but its power supply is usually faced with more inconvenience.The environmental energy acquisition technology based on bridge vibration can be applied to the bridge,which makes the self-drive of the bridge health monitoring system possible.However,the existing research on environmental energy harvesters is mostly in the theoretical and experimental stage,and the harvesters have not been designed in combination with the actual engineering parameters.In this thesis,the measured data of Hedong Bridge in Guangzhou are analyzed,and the main energetic frequency band,main amplitude,characteristic period and other related engineering parameters of bridge vibration are obtained.Based on the low frequency characteristics of bridge vibration,a set of low frequency vibration test platform system was built,on which the harvesters were experimentally studied.Two kinds of linear harvesters,piezoelectric and electromagnetic,were designed,and the relationship between the power generation efficiency and the key parameters of the system was analyzed.Based on the conversion of vibrational energy into fluid kinetic energy,two kinds of nonlinear harvesters are designed and it is found in the experiment that they can effectively gather the vibration energy of bridge.The measured data of Hedong Bridge during nearly one year were summarized and analyzed,and the acceleration time-history response and the main amplitude range during the operation of Hedong Bridge are obtained.Two methods,Welch and Yule-Walker,were used to carry out spectrum analysis of acceleration.The main energetic frequency band of bridge vibration was determined to be 1Hz-5Hz,and the periodic variation characteristics of bridge vibration were defined.The vibration characteristics of Hedong Bridge under different time periods,different seasons and strong wind conditions are further analyzed.And the relationship between vehicle load,temperature action,wind load and the change of vibration characteristics of Bridges is discussed.The wind speed and wind direction characteristics of the bridge location are analyzed and compared with the wind energy quantification results of the harvester based on vibrational energy-wind energy conversion designed in this thesis.Because the existing shaking tables have some limitations in carrying out low-frequency vibration tests,combining with the servo control theory and the development environment of Lab VIEW program,and using the mechanical principle of ball screw,a set of experimental platform system was built to simulate the low-frequency vibration characteristics.The relation between motor speed and control voltage of the system was calibrated by laser displacement meter and NI equipment.The related research achievements provide engineering parameter basis for the dynamic structure design of the harvesters,and provide a new technology for low-frequency vibration experiment.Four kinds of piezoelectric cantilever harvester,linear electromagnetic harvester,harvester based on vibrational energy-wind energy conversion,and piezoelectric-magnetoelectric composite harvester based on TLCD principle are designed,and experimental research is carried out.For the piezoelectric cantilever harvester,the response characteristics under resonant and non-resonant conditions are analyzed.It is found that resonance does significantly improve the power generation efficiency of the harvester.The positive effect of increasing the coverage area of piezoelectric material on improving the output of the system is explored,and it is found that it can effectively avoid the waste of vibrational energy of the cantilever beam.For the linear electromagnetic harvester,the response output of the harvester under different excitation frequencies and amplitudes is analyzed.It is found that the output power of the harvester is still considerable under the condition of non-resonant frequency and low amplitude.Compared with piezoelectric type,electromagnetic type has lower output voltage and internal resistance.For the harvester based on vibrational energy-wind energy conversion,the wind energy conversion capacity of the harvester under different excitation conditions is quantified by anemometer.It is found that the harvester has a considerable output wind speed range and a good corresponding relationship with the output voltage.In terms of output power,the harvester has a power output range of multiple orders of magnitude from μW to m W,which can better adapt to the periodic vibration characteristics of the bridge and effectively gather the vibration energy of the bridge.For the piezoelectric-magnetoelectric composite harvester based on the TLCD principle,the damper is combined with the energy harvester,and the energy collecting principle of the damper is skillfully utilized to realize the function conversion of dissipating energy to collecting energy.At the same time,the combination of piezoelectric and electromagnetic energy harvesting methods improve the overall working efficiency of the harvester.The related research achievements promote the practical application and research of energy harvesters in bridge engineering.The research contents and related achievements of this master’s thesis improve the related technology of low-frequency vibration experiment and promote the development of energy acquisition technology and its application in bridge engineering.