WO2007007122A1

WO2007007122A1 - Track monitoring equipment

Info

Publication number: WO2007007122A1
Application number: PCT/GB2006/050162
Authority: WO
Inventors: David Gilbert; Richard Alexander Charles
Original assignee: Deltarail Group Ltd
Priority date: 2005-07-14
Filing date: 2006-06-20
Publication date: 2007-01-18
Also published as: GB0514469D0

Abstract

Four vertical linear displacement transducers (38) monitor the tilt of the bogie (24) relative to each of two wheelsets (27). The tilt of the bogie (24) relative to the horizontal, as regards its low frequency component, Tl, is determined from comparison of the lateral acceleration, Al, with the centrifugal acceleration, the latter being calculated from measurements of vehicle speed, V, and yaw velocity, Gy. Its high frequency component, Ts, is determined by measuring vertical accelerations, Av1 - Av4, of the bogie (24) directly above each end of each wheelset (27), these accelerations being processed so as to deduce the vertical displacements of each side of the bogie above each wheelset. The signals from the linear displacement transducers (38) may be combined with these integrated signals to deduce apparent linear profiles of each rail (35) at the position of each wheelset (27), and discrepancies between such linear profiles deduced from measurements with the different wheelsets provide an indication of a wheel whose flange is climbing onto the rail.

Description

Track Monitoring Equipment

This invention relates to equipment for monitoring railway tracks, in particular for determining their twist.

Track monitoring equipment is described in WO 00/70148 for measuring the profile of a railway track, using an accelerometer measuring the vertical acceleration of a bogie and a linear displacement transducer measuring the vertical displacement of an axle relative to the bogie. Combining these measurements enables the profile of the top surface of the rail along its length to be monitored. Because of the requirement for double integration of the acceleration signals, this approach involves filtering out all variations above a wavelength threshold, typically set at 35 m.

GB 2 400 442 A (AEA Technology) describes track monitoring equipment that enables the cant of a railway track to be monitored. This uses measurements of the yaw of the bogie, combined with measurements of its speed and of its lateral acceleration, to determine the low frequency components of the tilt of the wheelset. The high frequency components of the tilt are obtained using accelerometers, one on each side of the bogie above the ends of a wheelset, these accelerometers being arranged to detect vertical accelerations of the bogie. The signals from the accelerometers are processed so as to deduce the vertical displacements of the bogie, and hence the tilt of the bogie relative to the track. The equipment enables the cant of the tracks to be measured; and from calculation of the differences in cant compared over a set distance, for example of 3 m, it is said to be possible to deduce the twist of the track. Such measurements presume that the treads of the wheels rest on top of the rails, but under some circumstances a wheel of a wheelset may ride up on its flange, and in an extreme case the flange may rest on top of the rail. A more reliable way of measuring twist has now been developed.

According to the present invention there is provided equipment for monitoring a railway track comprising a vehicle with a bogie, the bogie including at least two wheelsets, one of which is a leading wheelset, with four accelerometer transducers to detect vertical accelerations of the bogie, one such accelerometer transducer being mounted on the bogie adjacent to each end of each of the two wheelsets, and with four linear displacement transducers to detect vertical displacements of the wheelsets relative to the bogie, one such linear displacement transducer being mounted on the bogie adjacent to each end of each of the two wheelsets, and with means to monitor the speed of the vehicle along the track, means to process the signals from the said transducers so as to deduce the vertical displacements of the wheels, and hence at least the high frequency components of the apparent longitudinal profile of each rail of the track, means to deduce from all the processed signals the twist of the track, and means to compare an apparent longitudinal profile of a rail, or the cant of the track, as deduced from signals from the transducers adjacent to the leading wheelset with an apparent longitudinal profile of the same rail, or the cant of the track, as deduced from signals from the transducers adjacent to the other wheelset, any significant discrepancy between the two apparent longitudinal profiles or cants indicating that the twist measurement is unreliable and that one of the wheels of the leading wheelset has climbed up on its flange. Such equipment can be installed on a service vehicle, for example a passenger coach, without causing inconvenience to passengers or staff. Operations are totally automatic, so no staff are required to monitor it. Consequently the equipment enables the track along which that service vehicle travels to be monitored on every journey, so the track twist may be monitored several times a day. Because it is installed in a service vehicle, no additional vehicle operating costs are incurred in performing the monitoring. Alternatively this equipment may be installed on a dedicated track monitoring vehicle.

Preferably the equipment includes a position locating instrument, and this might use GPS, or might detect the location of objects at known positions along or adjacent to the track such as points or crossings. Dead reckoning methods may also be used, including inertial guidance systems, and measuring distance from known positions.

The invention will now be further and more particularly described, by way of example only, and with reference to the accompanying drawings, in which:

Figure 1 shows a side view, partly diagrammatic, of a vehicle incorporating a track twist monitoring system;

Figure 2 shows a diagrammatic perspective view of the bogie of the vehicle of figure 1, indicating the nature of the measurements.

Referring to figure 1, a track monitoring system 10 includes a base station computer 12 connected to an aerial 13 and to a display screen 14. The system 10 also incorporates instrumentation packages 16 (only one is shown) which are installed in service vehicles, typically no more than one such instrumentation package 16 in any one train. The figure shows a side view, partly diagrammatic, of parts of a vehicle 18 comprising a body 20 supported on air springs 22 on bogies 24 (only one of which is shown) . The bogie 24 includes an H-frame 25 and two wheelsets 27, and, referring also to figure 2, each wheelset 27 comprises two wheels 28 integral with an axle 29. At each end the axle 29 locates in a bearing in an axle box 30, the axle box 30 being connected by rubber springs 32 to the frame 25 so that the axle 29 and the axle box 30 can undergo limited movement relative to the frame 25. The wheels 28 roll along the rails 35 of a railway track.

The instrumentation package 16 includes four vertical accelerometers 36 and four linear displacement transducers 38, two at each side of the bogie 24. Each accelerometer 36 is attached to the frame 25 directly above a respective axle box 30, and each linear displacement transducer 38 is connected between the frame 25 and a respective axle box 30, so as to measure any vertical displacement of the wheel 28 relative to the frame 25. Signals from the accelerometers 36 and transducers 38 are provided to a computer 40 within the body 20. A tachometer 42 on the bogie 24 measures the rate of rotation of the wheel 28 (indicating the vehicle speed, V) , and supplies electrical signals to the computer 40. The computer 40 might for example locate beneath a passenger seat in the vehicle.

Referring now to figure 2, the bogie frame 25 is shown diagrammatically and in perspective, the signals from the accelerometers 36 being marked as AvI, Av2, Av3 and Av4 and the signals from the displacement transducers 38 being marked Dl, D2, D3 and D4. Mounted at the middle of the frame 25 is a lateral accelerometer 46 providing signals Al, and also an angular velocity yaw sensor 48 providing signals Gy. The signals from the lateral accelerometer 46 and the yaw sensor 48 are also provided to the computer 40.

The low frequency (long wavelength) tilt data is calculated in a conventional manner. That is to say the centrifugal acceleration Ac is calculated from the signals from the yaw sensor 48 and the tachometer 42, using :

Ac = V . Gy

The low frequency components of the angle of tilt, Tl (measured in radians) , of the bogie frame 25 relative to the horizontal, is then calculated using:

Tl = (1/g) . (Al + Ac)

The high frequency (short wavelength) data is calculated using the data from the accelerometers 36 and the transducers 38, these signals being sampled (digitised) every 1/8 m, in this case within the computer 40. At low speeds the accelerations are less abrupt and so more difficult to detect, so to ensure accuracy at low speeds the signals are sampled more often (for example at 32 points per 1/8 m) , and then averaged to provide raw data at 1/8 m spacing. This raw data may be stored and downloaded later. The digital data from each accelerometer 36 is processed, corresponding to integration twice with respect to time, but with a low pass filter, so as to determine the vertical displacements of each side of the frame 25. The low pass filter is adjusted in accordance with the vehicle speed, so that the cut-off frequency has a predetermined value. That is to say: DvI = ^ AvI dt dt,

Dv2 = IT Av2 dt dt,

Dv3 = ^ Av3 dt dt, and Dv4 =jT Av4 dt dt .

To determine the apparent longitudinal profile of a rail 35, these integrated values (which represent the vertical displacements of the frame 25) are combined with the signals Dl - D4 representing the displacements of the wheels 28 relative to the frame 25.

It will be appreciated that the longitudinal profile of a rail 35 as determined by the transducers 36 and 38 adjacent to the leading wheelset 27 should be the same as the longitudinal profile determined using data from the transducers 36 and 38 adjacent to the following wheelset 27 (taking into account the time delay between passage of the two wheelsets 27 over a point on the rail 35, which can be calculated from the separation of the axles 29 and the vehicle speed as determined from the tachometer 42) . If there is a significant discrepancy between these two longitudinal profiles, with the data from the leading wheelset 27 indicating an elevated portion of rail which is not observed with the data from the following wheelset 27, this suggests that the wheel 28 of the leading wheelset 27 has at least partly climbed up on its flange. Since the longitudinal profile can be determined in this manner to an accuracy of +/- 1.0 mm, a discrepancy greater than say 2.0 mm would be significant.

If there is no such discrepancy then the measurements may be taken to be accurate. The high frequency (short wavelength) components of the angle of tilt, Ts, of the bogie frame can then be calculated from:

Ts = (DvI - Dv2) /gauge

at the position of one wheelset 27, and Ts at the position of the other wheelset 27 can be calculated from:

Ts = (Dv3 - Dv4) /gauge

The full bandwidth tilt signals T at the positions of the wheelsets 27 can then be obtained by combining the low frequency tilt, Tl (which is taken as being the same for both wheelsets 27), with the high frequency tilt values, Ts, such that in each case:

T = Tl + Ts

The tilt signals T at the positions of the wheelsets 27, combined with data Dl and D2 (or D3 and D4) from the respective transducers 38 enable the cant the track to be determined at each position. These may be combined to determine the twist of the track. For example, the computer 40 may be arranged to determine the cant and twist at regular intervals (e.g. 1/8 of a metre) along the track.

Hence, at intervals of say every ten minutes, stored data concerning calculated values of the cant and twist along the track may be transmitted by the computer 40 back to the base station computer 12. If the instrumentation package 16 is installed on a service train, this avoids the necessity to store large quantities of data. If the instrumentation package 16 is instead installed on a dedicated track monitoring train, such downloading of the data may not be necessary, and all the data may be stored on board to the end of the journey. Furthermore it may only be necessary to store (or transmit) data concerning the locations at which cant, twist, or flange climb exceed predetermined thresholds; those locations would require track maintenance. The location may be determined simply by integrating the signals from the tachometer 42 (so as to ascertain the distance travelled) , if the starting position and route are known.

It will be appreciated that the system 10 might differ from that described above. It is applicable to railway vehicles with different suspensions, for example the primary suspension might be a helical spring in place of the rubber springs 32, and the secondary suspension might also be a helical spring, in place of the air springs 22. Furthermore the computer 40 might be mounted on the underside of the body 20, rather than within it. It will also be appreciated that the signals might be processed differently, for example being digitized at a fixed frequency preferably in the range 500 Hz to 3000 Hz, for example at 2 kHz. It will also be appreciated that the base station computer 12 and display 14 may not be required, if the data is instead stored in the vehicle 18.

Claims

1. Equipment for monitoring a railway track comprising a vehicle with a bogie, the bogie including at least two wheelsets, one of which is a leading wheelset, with four accelerometer transducers to detect vertical accelerations of the bogie, one such accelerometer transducer being mounted on the bogie adjacent to each end of each of the two wheelsets, and with four linear displacement transducers to detect vertical displacements of the wheelsets relative to the bogie, one such linear displacement transducer being mounted on the bogie adjacent to each end of each of the two wheelsets, and with means to monitor the speed of the vehicle along the track, means to process the signals from the said transducers so as to deduce the vertical displacements of the wheels, and hence at least the high frequency components of the apparent longitudinal profile of each rail of the track, means to deduce from all the processed signals the twist of the track, and means to compare an apparent longitudinal profile of a rail, or the cant of the track, as deduced from signals from the transducers adjacent to the leading wheelset with an apparent longitudinal profile of the same rail, or the cant of the track, as deduced from signals from the transducers adjacent to the other wheelset, any significant discrepancy between the two apparent longitudinal profiles or cants indicating that the twist measurement is unreliable and that one of the wheels of the leading wheelset has climbed up on its flange.

2. Equipment as claimed in claim 1 also comprising a single sensor for yaw velocity, and a single lateral accelerometer .

3. Equipment as claimed in claim 1 or claim 2 also comprising means to provide position information as to the location of the vehicle along the track.