轨检仪弦测法“以小推大”检查轨道轨向不平顺的理论研究

Discussion on Inspection of Track Alignment Irregularities according to Method of Chord Measuring and Its 'Using Small Fetch Big'

弦测法是轨道方向测量的一个基本方法,其主要不足在于它的幅值增益在空间频域内随不平顺波长变化而变化,这使弦测法的应用受到局限。本文讨论了弦测法的基本原理并推导了“以小推大”公式,在此基础上分析了轨检仪利用弦测法检测轨向不平顺时,“以小推大”方法的系统误差与随机误差,并进行了计算机仿真。仿真结果证明:“以小推大”公式对波长为整数倍弦长的线路原始轨向不平顺值能较好地进行拟合。最后,针对波长为非整数倍弦长的轨向不平顺值建议采用牛顿插值解法。

The method of chord measuring is a basic method of measuring track alignment irregularity. Its main disadvantage is that the amplitude gains vary with the irregular wavelengths in the spatial frequency domain, which makes the application of the method have its limitation. This paper mainly discusses the basic principle of the method of chord measuring and consequently concludes the formula of ＂Using small fetch big＂. On this basis, this paper analyses the systematic and random errors in the＂ Using small fetch big＂ formula; the track geometry inspection device uses the method of chord measuring to detect track alignment irregularities, and conducts computer simulation. The result proves that the formula of ＂Using small fetch big＂ can curvefit the original irregularities of tracks where the wavelengths are integral times of chord lengths. In the end, this paper gives the method of Newton interpolation as the solution for inspection of the track alignment irregularities of tracks where the wavelengths are nonintegral times of chord lengths.