基于尺度—小波能量谱和神经网络的内燃机故障诊断

为了对内燃机气门及活塞—连杆组故障进行有效地诊断,通过试验测取内燃机在不同故障下的振动信号,利用连续小波变换得到信号在不同尺度上的能量分布,即信号的尺度—小波能量谱。其能量主要分布于尺度范围1~32,且相同故障模式下的尺度—小波能量谱呈现出相似性,不同故障模式之间的尺度—小波能量谱存在很大的差异性,以此作为不同故障模式的信号特征,结合BP神经网络方法,实现了对待检信号的正确识别。     

基于列车用户优先级的频谱共享博弈算法

不同业务优先级高速铁路用户的爆炸式业务需求与稀缺频谱资源的矛盾日益突出。针对运行于不同地形环境、在相同eNB覆盖范围内的高速铁路次用户的频谱共享博弈问题进行研究。基于次用户承载业务的不同优先级,提出模糊综合评判-优先级调度算法,将次用户间的频谱竞争建模为非合作博弈,通过次服务的频谱效用函数、主系统的频谱交易价格函数实现次用户间的差异化动态频谱共享。仿真结果表明,算法较好地反映了真实的频谱共享情形,可以更加准确地对次用户频谱需求进行业务优先级划分,提高频谱利用率的同时保证了其最大效用。     

武广高速铁路轨旁电磁干扰实测及分析

研究了GB/T 24338-2标准中关于分辨率带宽(RBW)的规定。通过实验对比了标准推荐的RBW及实地测试使用的RBW的测试效果,结果证明两者测量干扰峰值效果相同,但后者扫描速度更快,更适宜测试现今高速铁路的电磁干扰。并在武广高速铁路咸宁段电分相处实地测试运行中的CRH3型高速列车的弓网离线电弧电磁干扰,获得其在30 MHz~1 GHz的频谱。通过频谱分析了高速列车弓网离线电弧电磁干扰的幅频特性,为评估弓网离线电弧电磁干扰对高速列车的影响提供依据。     

基于人工神经网络的整流电路故障诊断

提出了一种基于人工神经网络进行整流电路故障诊断的方法.分析了变频器整流电路的故障模式,提出了根据直流母线电压频谱作为神经网络的输入进行故障定位的方法,并进行了仿真研究.     

A real-time impact detection and diagnosis system of catenary using measured strains by fibre Bragg grating sensors

This paper describes an impact detection system using strain signals based on fibre optic sensors(FBG) for the real-time monitoring of the catenary system. The proposed detection system consists of three subsystems: a measuring system, a data processing and analysis system, and a status display and data access system. Because the strain signals obey the normal distribution, to monitor the catenary system in real time, a novel method that combines mobile standard deviation with the mobile Pauta criterion is proposed to distinguish real impact from the strain signal background. The use of this adaptive judging method reduces the misjudgment rate of impacts and improves the impact recognition accuracy. These impacts can be identified by the data analysis system, which provides impact location and their causes using the features of the catenary system. This method can simplify the detection system compared with the traditional location method. An application to a commercial metro line system indicated that the impacts on the catenary system were main caused by overlaps, expansion joints or steady arms, and were verified by correspondence with the floor plan of the catenary and manual inspection results. These results verified the reliability and effectiveness of the proposed impact detection system.     

斜拉索无应力长度计算

对比分析了基于抛物线、悬链线理论的五种斜拉索无应力长度的计算方法,用两座有代表性的实桥算例分析了各种斜拉索无应力长度解的精度。根据计算结果给出了斜拉索无应力长度的计算建议。     

Influence of the aerodynamic forces on the pantograph–catenary system for high-speed trains

Most of the high-speed trains in operation today have the electrical power supply delivered through the pantograph–catenary system. The understanding of the dynamics of this system is fundamental since it contributes to decrease the number of incidents related to these components, to reduce the maintenance and to improve interoperability. From the mechanical point of view, the most important feature of the pantograph–catenary system consists in the quality of the contact between the contact wire of the catenary and the contact strips of the pantograph. The catenary is represented by a finite element model, whereas the pantograph is described by a detailed multibody model, analysed through two independent codes in a co-simulation environment. A computational procedure ensuring the efficient communication between the multibody and finite element codes, through shared computer memory, and suitable contact force models were developed. The models presented here are contributions for the identification of the dynamic behaviour of the pantograph and of the interaction phenomena in the pantograph–catenary system of high-speed trains due to the action of aerodynamics forces. The wind forces are applied on the catenary by distributing them on the finite element mesh. Since the multibody formulation does not include explicitly the geometric information of the bodies, the wind field forces are applied to each body of the pantograph as time-dependent nonlinear external forces. These wind forces can be characterised either by using computational fluid dynamics or experimental testing in a wind tunnel. The proposed methodologies are demonstrated by the application to real operation scenarios for high-speed trains, with the purpose of defining service limitations based on train and wind speed combination.     

转K5型转向架弹簧托板疲劳试验方法研究

对转K5型转向架弹簧托板动应力进行了线路实测,编制了相对疲劳薄弱部位的动应力谱和弹簧托板的动载荷谱,采用无限寿命设计理论,利用线路实测动应力和AAR货车设计制造规范中的有关材料及接头的疲劳极限,评估了弹簧托板的疲劳强度,根据损伤等价原则,提出了实物疲劳试验加载方案.     

基于OFDM的移动蜂窝系统中分布式带宽借复用机制

为了提高未来基于OFDM的移动蜂窝系统的频谱效率,尤其在小区/扇区间流量不均匀的情况下,本文基于两种传统的扇区结构(菱形扇区和五边形扇区)提出一种分布式带宽借复用DBBR(Distributed Bandwidth Borrowing and Reusing)算法。算法利用离基站较近的用户有着较好信道条件的特点,那些带宽不够的扇区以无功率控制的方式借复用相邻扇区中空闲的带宽和离基站较近的用户所使用的带宽,以此提高扇区的吞吐量。理论分析和仿真结果表明相对于传统的三扇区结构,该算法使扇区的平均吞吐量有20%左右的提升,同时说明加入功率控制也不会带来系统吞吐量更多的改善。     

Dynamic assessment of existing soft catenary systems using modal analysis to explore higher train velocities: a case study of a Norwegian contact line system

Significant advances made on the rolling stock have considerably increased the possibility of higher speeds in existing railways. Thus, it is important to explore higher speeds and potential limiting factors of existing soft catenary systems. The present paper investigates procedures to assess the dynamic behaviour of these systems using response sampling and modal analysis. The assessment evaluates and quantifies dynamic response along the section. To verify the approach, a case study is conducted and the following assessment methods are used: lengthwise track correlation estimating dynamic predictability, power spectral density estimations before and after passage and short-time Fourier transforms and spectrograms. The combination provides detailed information on the dynamic behaviour. The first part introduces necessary considerations for suggested modal analysis. The second part describes an existing Norwegian section. The case study is conducted using a finite element model including a straight and a given section between Oslo-Trondheim, providing detailed evaluations and system limitation detections.