Study On Self-powered Power Supply For The On-board Safety Monitoring Of Freight Trains

Railway freight transportation plays an increasingly important role in our country's social-economic life.With the expanding scale of railway freight transportation and increasing pressure of railway transportation safety,more and more attention has been paid to ensuring the safe of freight trains.Due to lack of power supply on carriages,freight trains cannot carry on-board safety monitoring equipment to obtain real-time data of various performance indicators of the freight trains in motion.Aim at the problem of power supply shortage,in this dissertation,some research on piezoelectric energy harvesting technologies to collect rich mechanical vibration energy of freight trains in motion and convert it into electric energy was done.A self-powered power supply was designed to provide power for on-board safety monitoring equipment on railway freight trains.Firstly,power demand of on-board safety monitoring subsystem and vibration characteristics of freight trains were studied.Based on these,the main specifications of self-powered power supply were determined.Then,the mechanism of piezoelectric generator was studied,and the mathematical model of unimorph cantilever beam piezoelectric vibrator was established.Piezoelectric simulation analysis was carried out by ANSYS in order to verify the rationality of the mathematical model.Based on the theoretical model and simulation results,broadband and low resonance frequency piezoelectric energy harvesters were designed for energy harvesting in low frequency vibration environments through structural optimization.Finally,the unimorph cantilever beam piezoelectric vibrator and piezoelectric energy harvester were prepared and experimentally studied by the vibration test bench.The piezoelectric energy harvesting circuit based on LTC3588-1 energy harvesting and management chip was designed,and the experiments of super capacitor energy storage and supply were carried out to verify the effectiveness of broadband and low resonance frequency piezoelectric energy harvester designed before.Through the research,several conclusions were obtained:(1)The main technical indicators and design basis of self-powered power supply were determined.The studies found that the average power consumption of on-board subsystem can be controlled at 6.66 mW,the maximum power consumption at working state was 252 mW,and the voltage was 3.6 V.The vibration energy of freight trains is concentrated in low frequency vibration environment within 20 Hz.(2)The mathematical model of unimorph cantilever beam piezoelectric vibrator was established include its output voltage,electric energy and charge.Besides,the natural frequency and equivalent circuit model were got.Through the theoretical model and results of simulation,relationship between structure sizes and material properties of piezoelectric vibrator and its natural frequency and power generating capacity were discovered.(3)Broadband and low resonance frequency piezoelectric energy harvesters were designed based on the theoretical model and simulation results in this dissertation.Studies have shown that the effective response frequency band of energy harvester was 7.6Hz-15.4Hz which has been expanded by 147%.It has better low-frequency resonance performance and power generation capabilities compared with single piezoelectric vibrator.(4)The power generation performance of piezoelectric energy harvester was studied by simulation and experiment.Results of simulation have shown that the optimal load under standard energy recovery circuit was 120 k? and the maximumoutput power was 0.477mW through Multisim.Piezoelectric energy harvesting circuit based on LTC3588-1 energy harvesting and management chip was designed.The experiments proved that the circuit can effectively collect and reserve electric energy converted by piezoelectric energy harvester and realize intermittent supply energy to external load,which has met the power demand of vehicle subsystems.