Research On The Vibration Energy Harvester Of Bridge Based On Nonlinear Energy Sink

Establishing automatic monitoring system of wireless sensor network has become an inevitable development trend of the intelligent safe operation and maintenance of modern traffic.Rational utilization of the vibration energy of bridge structure has a sound engineering application value to solve the power supply problem of bridge health monitoring and sensing equipment especially in remote areas.As a classical vibration control technology,nonlinear energy sink(NES)has been innovatively combined with approaches to harvest vibration energy in recent years,and a series of research efforts had been made.For health monitoring system of bridges,energy supplying of the sensors has always been a problem needed improving.Exploring the applicability of vibration energy harvester based on nonlinear energy sink to bridges is of great theoretical and practical significance.In this thesis,the author investigates a device based on nonlinear energy sink being used to harvest the vibration energy of bridge,which can make use of its unique characteristics of targeted energy transfer to transmit the vibration energy of bridge caused by instantaneous impact to the nonlinear energy sink.Then the vibration energy can be converted into electricity by the piezoelectric materials to power wireless sensors.Based on the above ideas,the thesis aims to provide theoretical and experimental basis for the design and research of the nonlinear vibration energy harvesting device for the bridge structure.Taking a simply supported railway girder bridge as example,this work investigated the applicability of vibration energy harvester based on the nonlinear energy sink to the bridge.Firstly,mechanical properties and parameters of the NES were characterized.Then,the vertical coupling dynamics theory of vehicle-track-bridge was used to solve the mid-span displacement under different vehicle condition.Subsequently,dynamic responses and energy harvesting effect of the NES under different initial excitation conditions were evaluated using the dynamic model of NES-bridge coupling system.Finally,the applicability of NES to the bridge structure was analyzed and verified by the experiment of wood beam.The results show that the NES has a weak linear stiffness and a strong nonlinear stiffness.The device installed on the bridge is sensitive to initial displacement,and targeted energy transfer(TET)is excited only if initial displacement reaches a certain threshold.Moreover,TET cannot be excited when initial energy input cannot surpass the critical threshold,so the energy harvesting efficiency is poor.In this work,the frequency range of NES was controlled to be close to the natural frequency of the bridge.The proposed NES can take full advantage of the characteristics of targeted energy transfer under appropriate vibration excitation of the bridge.In this way,energy harvesting can be realized in a wide frequency range and good energy harvesting efficiency can be obtained.