Monitoring vertical track irregularity from in-service railway vehicles

Abstract

Condition monitoring of track geometry from sensors mounted on an in-service vehicle offers continual monitoring of track geometry that can aid track maintenance strategies. Mounting and maintaining a full track geometry recording system on an in-service vehicle is an expensive proposition as the commonly used optical sensors are difficult to keep working in the dirty railway environment. A simpler and more cost-effective alternative is to estimate track geometry using a small number of robust sensors such as accelerometers and rate gyroscopes, from which a worthwhile proportion of geometric quality measures and specific irregularities can be identified. This paper describes the theory and practical results of using a bogie-mounted pitchrate gyro to obtain mean vertical alignment, conditional on the secondary vertical damper geometry. Left and right axlebox-mounted accelerometers can be added to provide short wavelength irregularity, if required. Results from trials on Tyne and Wear Metro vehicles and on a Class 175 mainline vehicle demonstrate effective vertical irregularity monitoring, in particular the ability to monitor vertical irregularity over a wide range of vehicle speeds down to about 1 ms-1, where vertically sensing accelerometers combined with displacement transducers are unable to function correctly.

Condition monitoring opportunities using vehicle-based sensors

“…One sensible location is above the centre of a wheelset. A pitch rate gyro attached to a bogie can also measure the vertical trajectory taken by the bogie [10]. A vertical curvature signal is obtained by dividing the pitch rate (measured by the pitch rate gyro) by the vehicle speed, similar to dividing the acceleration by the square of the vehicle speed.…”

“…As the wheelsets encounter an irregularity such as a dipped joint, or a disruption to the heading, the leading and the trailing wheelsets are affected in turn, spatially separated by the bogie wheelbase. Figure 2 shows the vertical 35 m alignment over 100 m of jointed track, obtained as described in reference [10], together with the vertical curvature signal. The vertical alignment shows the presence of dipped joints spaced approximately 18 m apart (consistent with 60 ft rail sections).…”

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

“…Weston et al [6] discuss the merits and compromises associated with various inertial sensor installations, including bogie mounted accelerometers. Their description of the filtering effect of the bogie geometry is particularly relevant to the specification of a trial MEMS accelerometer, as is the information on the behaviour of the primary and secondary suspension.…”

“…Track defects in the vertical profile with mean to peak value of up to 23mm [4] to be measured to a precision of +/-1mm. Geometric filtering due to the bogie wheelbase means that the shortest wavelength feature to be usefully measured can be taken as 10m [6]. Features with wavelength longer than 35m are filtered out by the recording system [2].…”

Track geometry estimation from car-body vibration

“…Waston et al [2,3] demonstrated the track irregularity monitoring using bogie-mounted sensors. Alfi et al [4] proposed a technique for estimating long wavelength track irregularities from on-board measurement.…”