Measurement Of Railway Irregularities And Signal Processing

As rail transit has advantages of large traffic volume, great convenience, low energy consumption and high efficiency, it brings great benefit to humans. However, it creates additional noise sources as well. Due to the irregularities of rail, the impact load between rail and wheel is generated. This load with excessive amplitude would cause fracture and damage to rail and wheel, and the increased vibration would enlarge the rail-wheel noise and worsen the wear of rails. Therefore, it is important to measuring rail irregularities.In this paper, the types and reasons of the rail irregularities and their effects on the vibration system of rail and wheel are analyzed firstly. The rail irregularities can be seen as a random process. By describing the statistical characteristic of the random process, the general analysis method of the irregularities is proposed.Two methods of measuring the irregularities are analyzed. One of the methods is to fasten a beam as a benchmark on the rail, move a probe on the top surface of rail, and measure the relative position of the probe and the benchmark beam. Another method is to move a vehicle on the top surface of rail, collect the signal of the vertical acceleration of the vehicle by an accelerometer, and transform the acceleration signal into displacement signal. One priority of the later method is that the length of measured rail would not be limited by the measuring device. By refer to and compare several existed rail irregularities measuring methods, a method based on acceleration signal is chosen in this study.The process of transforming acceleration signal into displacement signal is studied in detail. The acceleration signal can be transformed into frequency domain firstly, and then into displacement signal. It can also be transformed into displacement signal directly by integrating twice and then be filtered in low frequency. By comparing the results of these two methods, the method of integrating twice and then filtering in low frequency can lead to more precise results of rail irregularities spectrum.For achieving data acquisition, the communication process between the software and hardware of the data acquisition device is analyzed. A graphical user interface (GUI) of data acquisition which is convenient for users to use is compiled in Visual Basic. The rail irregularities spectrum can be acquired by data acquisition via the measuring vehicle and data process described above.In this work, a model of measuring rail irregularities is analyzed. The method of data process is proposed and verified, and the GUI of data acquisition is designed. A practically usable rail irregularity is acquired at last. This work can provide some experience and instruction for measuring rail irregularities in practice.