Monitoring lateral track irregularity from in-service railway vehicles

Maintaining the alignment of railway track is vitally important for the smooth and safe passage of railway vehicles. Poor track alignment can result in poor ride quality, flange contact, or even flange climb. Accurate horizontal track geometry can be measured using a dedicated track recording vehicle or from a full track geometry recording system mounted on an in-service vehicle. This paper describes the use of sensors mounted on the bogie of an in-service vehicle to estimate the mean track alignment without the use of optical or contact sensors. In principle, either bogie lateral acceleration or yaw rate can be processed to give an estimate of mean lateral track irregularity, but a yaw rate gyro provides consistent estimates down to lower vehicle speeds than does an accelerometer and does not require compensation for the effects of bogie roll. An improved estimate can be obtained by inverting the dynamic relationship between the mean track alignment and the bogie yaw motion. This is demonstrated with results from a Class 175 vehicle. Continually monitoring the lateral response of a bogie on an in-service vehicle, using only a yaw rate gyro, can provide data enabling the prioritization of maintenance operations.