| In recent decades,the rapid development of infrastructure construction in China has gradually built the world’s leading traffic routes.As society’s needs change,roads,railways and bridges need to be built into harsher natural environments to connect remote areas and boost local economies.The use of green,convenient and low-cost power supply in bridge wireless sensor power system has become a relatively sharp and urgent problem to be solved.Under the background of traffic intelligence,the use of piezoelectric effect through piezoelectric energy harvester to transform structural vibration energy into electrical energy,power supply for the electric system in the bridge,has become a current research focus,the more mature research is beam piezoelectric energy harvester.In order to meet the actual demand of power supply,scholars at home and abroad constantly improve the output performance of the energy harvester.At the same time,it is necessary to consider and solve the problem that the output performance of the energy harvester is reduced due to natural environmental factors in the actual working conditions.As an important part of the environmental factors,environmental temperature load should be paid attention to.In this paper,cantilever beam piezoelectric energy harvester and doubly-clamped piezoelectric energy harvester are studied.Theoretical analysis is used to determine the main influencing factors of the two beam-like piezoelectric energy harvester caused by temperature load.The influence of temperature on the output performance of the beam-like piezoelectric energy harvester was determined by simulation and experiment.The research contents of this paper are as follows:Firstly,the output voltage expressions of two kinds of beam-like piezoelectric energy harvesters are derived by using linear thermo-piezoelectric constitutive equation,and the main influencing factors of temperature on the basic dynamic characteristics and output performance of beam-like piezoelectric energy harvesters are determined.Secondly,ANSYS Workbench software was used to establish the force-thermo-electric coupling finite element analysis model of the beam-like piezoelectric energy harvester using the restart technology,which was used to solve the basic dynamic characteristics and output performance related results of the beam-like piezoelectric energy harvester affected by temperature load.The load resistance of beam-like piezoelectric energy harvester affected by temperature is optimized and the maximum actual output power is calculated.A transient simulation analysis system was constructed to simulate the output performance of beam-like piezoelectric energy harvester under actual temperature load.At the same time,the equipment system for temperature test of beam-like piezoelectric energy harvester and the corresponding test scheme are designed,and two kinds of beam-like piezoelectric energy harvester are made to carry out the experiment.Then,the simulation and test results of the beam-like piezoelectric energy harvester affected by temperature are analyzed to determine the influence mechanism of temperature load.It is found that the temperature variation of the beam-like piezoelectric energy harvester has a greater influence on the vibration mode of the doubly-clamped piezoelectric energy harvester than the cantilever beam piezoelectric energy harvester.The piezoelectric elastic parameterc11.which decreases with the increase of temperature,is the main factor affecting the natural frequency of cantilever beam piezoelectric energy harvester.When the temperature of the piezoelectric cantilever beam rises from-50℃to 50℃,the first natural frequency of the cantilever beam piezoelectric energy harvester changes about 8%.The thermal expansion and cold contraction of the piezoelectric beam is the main factor affecting the change of its natural frequency caused by temperature.The first natural frequency change of the doubly-clamped piezoelectric energy harvester is about 7.8%in the range of 20℃to50℃.In the range of 20℃to-50℃,the first natural frequency variation of the doubly-clamped piezoelectric energy harvester is about 23.4%.Temperature changing piezoelectric stress parametere e31 and relative dielectric parameter εr33S are the main factors that cause the peak output power of beam-like piezoelectric energy harvester to change with temperature.When the temperature of the piezoelectric beam rises from-50℃to 50℃,the output peak power of the cantilever beam piezoelectric energy harvester increases as a whole,while the output peak power of the doubly-clamped piezoelectric energy harvester reaches the minimum at 20℃.When the temperature of the doubly-clamped piezoelectric energy harvester rises or falls from 20℃,the output peak power increases.The temperature change of the piezoelectric beam results in the change of various parameters of PZT-5H piezoelectric material,so the peak value and frequency band width of the output power frequency response function curve of the beam-like piezoelectric energy harvester are changed by temperature.The output performance of the beam-like piezoelectric energy harvester is affected by temperature,which is mainly due to the first natural frequency shift.The actual output power of the cantilever beam piezoelectric energy harvester reaches the maximum at room temperature,and decreases with the increase or decrease of the cantilever beam piezoelectric energy harvester at 20℃,and decreases by 91%and 94%at±50℃,respectively.In a certain temperature range,the actual output power of the doubly-clamped piezoelectric energy harvester will be increased by increasing or decreasing the temperature of room temperature,and the actual output power will be decreased by increasing or decreasing the temperature of the beam beyond the temperature range.The output power of the doubly-clamped piezoelectric energy harvester at 50℃is obviously lower than the actual output power at room temperature,but the actual output power at-50℃is still greater than the actual output power at room temperature.The results of simulation and test show that the temperature stability of the energy capture performance of the doubly-clamped piezoelectric beam is better than that of the cantilever piezoelectric beam.According to the influence mechanism of temperature on the two beam-like piezoelectric energy harvesters,some suggestions are put forward to reduce the influence of temperature.Finally,the influence of transient temperature load is simulated and tested for cantilever and doubly-clamped beam piezoelectric energy harvester.The feasibility of two beam-like piezoelectric energy harvesters to supply power to bridge electrical system under actual temperature load is prospected.The shortcomings in the finite element calculation of the force-thermal-electric coupling of beam-like piezoelectric energy harvesters and the errors in the experiments are presented.In this paper,a simulation calculation system for basic dynamic characteristics and output performance of piezoelectric energy harvester subjected to temperature load is proposed,which is not only applicable to the two beam-like piezoelectric energy harvesters in this paper,but also applicable to other structural forms of piezoelectric energy harvester.In addition,the influence mechanism of temperature load on the two beam-like piezoelectric energy harvesters is analyzed in this paper,which provides theoretical support for finding effective solutions to reduce the influence of temperature load.Through the exploration of this paper,it provides some reference for the practical application of beam piezoelectric energy harvester. |
