Determination of Rail Vertical Profile through Inertial Methods

Abstract

Undergrounds and other metropolitan railway systems are characterized by their intense traffic, lasting up to 20 h per day, and so they need their maintenance work programmes to be optimized, implying an optimization of the monitoring processes. This article proposes an alternative to the traditional optical methods for monitoring rail profiles which can only be carried out by special vehicles. This is a new procedure that obtains the rail profile by means of inertial methods. The model this work is based on takes its input from the vertical accelerations produced in railway axles measured in trains running on regular services and calculates the rail irregularities that have originated them. The model uses the Fourier transform in order to solve the equations and find the transfer function that relates the input function and the output function in the frequency domain. The solution is then reverted into the time domain by applying the inverse Fourier transform. Data input comes from real measurements taken on line 9 of the Madrid underground, and the model's effectiveness was then analysed by comparing the output data with the rail profile taken using optical methods.

Road and track irregularities: measurement, assessment and simulation

“…[48] A 'simple' inertial measurement system uses accelerometers on axle boxes to calculate the rails longitudinal level by double integration and filtering. [50][51][52][53][54] Difficulties with such systems are the very wide dynamic range of the signals and the fact that track geometry is determined by rather low frequencies. It is often stated that for inertial systems to operate effectively, the dynamic range has to be restricted by mounting the accelerometer on a sprung platform (best on the car body).…”

Investigating inertial measurements using MEMS devices in trainborne automatic track condition monitoring applications

“…Real et al [3] also use axle-end mounted accelerometers but employ a method which is similar to that described by Lewis and therefore more directly relevant here than Boronakhin et al Although they do not describe which technology family their accelerometers belong to, Real et al do provide information on dynamic range and bandwidth for their various positions and orientations. Their paper also provides detail on range, resolution and precision for the various track geometry parameters produced by their system.…”

Identification of the power spectral density of vertical track irregularities based on inverse pseudo-excitation method and symplectic mathematical method

“…The axle box acceleration measurement method [1][2][3][4][5][6][7][8] is widely applied to identify the track irregularity status. The advantages of this method [1,2] include the following: the measurement device is mounted on an in-service vehicle, the device is cheaper than an optical sensor and the rail irregularities are measured at the line speed.…”

“…The advantages of this method [1,2] include the following: the measurement device is mounted on an in-service vehicle, the device is cheaper than an optical sensor and the rail irregularities are measured at the line speed. Grassie [1] appropriately established the relationship between the measured displacement of the axle box accelerometer and the actual displacement of the track irregularities using a linearized model of the single wheelset-rail interaction.…”

“…However, the optical sensor was introduced to detect the rail displacement. Real et al [2] transformed the axle box acceleration into its displacement using the Fourier transform, and a vehicle model with two degrees of freedom was established to identify the vertical irregularities of the rail, in which the wheel-rail contact and track models were represented by equivalent stiffness and damping. Berggren et al [5] established the relationship between axle box acceleration and track roughness level using the speed-dependent transfer function.…”