【作者】 王刚；

【导师】 黄玲； 苗葳；

【作者基本信息】 兰州理工大学 ， 控制工程（专业学位）， 2023， 硕士

【摘要】 伴随着我国铁路运营里程、行车密度、列车运量的提高,对于钢轨状态实时监测技术的优化与升级迫在眉睫。压电超声换能器作为监测系统的核心部件,其工作性能将直接影响监测结果。本文立足于提高钢轨状态监测技术水平,从超声换能器“拖尾”信号抑制、宽频阻抗匹配以及高压脉冲驱动三个方面展开研究,力求实现在役钢轨状态监测中压电超声换能器性能的优化。1.为了抑制超声换能器因自身特性而产生的“拖尾”信号,论文首先探索了一种拟合优化超声换能器BVD模型参数的新方法,建立了精确的BVD等效模型。其次,研究了超声换能器在不同信号激励下的发射响应,获得了最佳激励信号。依据波的叠加原理,提出了一种幅值倍增的“拖尾”抑制异相信号,并明确了信号的最佳叠加周期数,进而设计了一种激励信号与异相信号相结合的五电平激励信号。仿真与实验结果表明,采用五电平组合激励信号可以更好地抑制超声换能器的“拖尾”效应,提升超声换能器损伤检测性能。2.针对监测系统中超声换能器与激励源存在阻抗失配,以及带载后谐振频率偏移等问题,论文对宽频阻抗匹配网络进行研究。基于阻抗匹配原理设计了四种匹配网络,通过分析不同网络性能,明确了二阶L型网络为最优网络。在建立匹配网络传递函数的基础上,研究了宽频匹配的实现过程并确定了网络的最佳参数组合。钢轨一发一收平台实验结果显示,论文设计的宽频阻抗匹配网络使发射端超声换能器的有功功率、工作带宽和发射强度显著提高,超声换能器在工作带宽内均可达到良好的发射状态。3.为了实现本文设计的五电平激励信号的发射,提升超声换能器对于长距离钢轨的监测性能,论文制定了高压驱动电路设计方案。逆变电路的设计借鉴了工业领域中的多电平逆变技术,选取级联H桥拓扑结构实现五电平输出。高压输出则摒弃了脉冲变压器的设计方案,直接对高压电源进行逆变实现高压输出,使得驱动电路易于与阻抗匹配电路相结合。此外,对其他外围电路的设计过程也进行详细阐述。最终通过仿真验证了设计方案的可行性,并试制了驱动电路PCB电路板,为后续的工作奠定了硬件基础。更多还原

【Abstract】 With the improvement of railway mileage,traffic density and train volume in China,it is urgent to optimize and upgrade the real-time rail condition monitoring technology.Piezoelectric ultrasonic transducer is the core component of the monitoring system,and its performance will directly affect the monitoring results.This paper aims to improve the technical level of rail condition monitoring,and studies on three aspects of ultrasonic transducer’s "trailing" signal suppression,broadband impedance matching and high-voltage pulse driving,and strives to optimize the performance of piezoelectric ultrasonic transducer in rail condition monitoring in service.1.In order to suppress the "trailing" signal caused by the characteristics of the ultrasonic transducer,a new method of fitting and optimizing the BVD model parameters of ultrasonic transducer is explored,and the accurate BVD equivalent mode is established.Secondly,the transmitting response of ultrasonic transducer under different excitation signals is studied,and the optimal excitation signal is obtained.Based on the principle of wave superposition,a phase-locked amplification method that doubles the amplitude of the "trailing" suppression out-of-phase signal is proposed,and the optimal number of signal superposition periods is determined.and then a fivelevel excitation signal combining excitation signal and out-of-phase signal is designed.The simulation and experimental results show that the five-level combined excitation signal can better suppress the "tailing" effect of ultrasonic transducer and improve the damage detection performance of ultrasonic transducer.2.In response to impedance mismatch between the ultrasonic transducer and excitation source,as well as frequency deviation caused by loading,the broadband impedance matching network is studied in this paper.Four matching networks are designed based on the impedance matching principle,and by analyzing the performance of different networks,the second-order L-type network is determined to be the optimal network.Based on the transfer function of the matching network,the realization process of broadband matching is studied and the optimal parameters of the network are determined.The results from experimental platform of pitch-catch show that the broadband impedance matching network designed in this paper can significantly improve the active power,working bandwidth and transmitting intensity of the ultrasonic transducer at the transmitting end,and the ultrasonic transducer can achieve good transmitting state within the working bandwidth.3.In order to realize the emission of the five-level excitation signal designed in this paper and improve the performance of ultrasonic transducer for long-distance rail monitoring,a high-voltage driving circuit is designed.The design of inverter circuit refers to the multilevel inverter technology in the industrial field,and selects cascaded H-bridge topology to achieve five-level output.High-voltage output abandons the design scheme of pulse transformer,and directly inverts the high-voltage power supply to realize high-voltage output,so that the driving circuit is easy to combine with the impedance matching circuit.In addition,the design process of other peripheral circuits is also described in detail.Finally,the feasibility of the design scheme is verified through simulation,and the PCB circuit board of the driving circuit is trial-produced,which lays the hardware foundation for the follow-up work.更多还原