Method of calibrating an onboard computer installed in a rail vehicle

Abstract

A data-processing system 10 onboard a rail vehicle receives an input set of rail vehicle characteristics and a dataset comprising an independently verified calibrated wheel radius from which calibrate

Description

The present invention relates to a computer-implemented method of calibrating a distance measurement used by an onboard computer installed on a rail vehicle. Onboard signalling systems are reliant on accurate odometry to allow both the train and signalling system to know the exact location of a train. A rail vehicle's precise location may be established using fixed balises. These balises are in known locations and give both train and signalling system the exact data of where a rail vehicle is at any one time. Between these fixed balises the rail vehicle's location is reliant on the onboard odometry system. Whilst the accuracy of a system can be improved by increasing the number of fixed balises, these can be costly to install, calibrate and maintain. A rail vehicle odometry system is reliant on knowing the exact radius of the rail vehicle's wheels. This is subject to variation due to both wear and wheel maintenance. Wheels are frequently re-profiled using specialist lathes to maintain the correct shape, which can reduce the diameter of the wheel by several millimetres. For example, a difference of 10mm diameter on a typical 600mm wheel can lead to a difference in measured odometry of 17m over 1km. Hence in a railway with fixed balises positioned at every 50km the reported position of a rail vehicle being 1000m from its actual position. Most wheels are significantly bigger than 600mm, so the inaccuracy is even larger. One reason for requiring such detailed rail vehicle information therefore is to enable calibration of the distance measurement used by the onboard computer. Without such calibration, between balises errors may occur that lead to trains appearing to "jump" over each other within the signalling system. Clearly, therefore, any inconsistencies or errors in the input of this information that then affects the distance measurement can have very serious consequences for rail vehicle safety. One method used to mitigate these issues is to have a technician enter wheel data into an onboard computer following re-profiling and maintenance. This relies on accurate wheel measurements during re-profiling and only takes into account the wheel diameter at the moment the rail vehicle re-enters service. As the rail vehicle continues in service until the next maintenance is scheduled, the wheel diameter will change due to wear and possible damage, therefore affecting the accuracy of the distance measurements by the onboard systems. The present invention aims to address these issues, by providing, in a first instance, a computer-implemented method of calibrating a distance measurement used by an onboard computer installed on a rail vehicle, comprising: receiving an input set of rail vehicle characteristics; receiving a set of independently verified rail vehicle characteristics; calibrating the input set of rail vehicle characteristics using the set of independently verified rail vehicle characteristics to produce a calibrated set of rail vehicle characteristics; and calibrating the distance measurement used by the onboard computer based on the calibrated set of rail vehicle characteristics; wherein the set of independently verified rail vehicle characteristics comprises a mean calibrated wheel radius of the rail vehicle. By calibrating an input set of rail vehicle characteristics based on independently verified values even if errors are included in the input of the rail vehicle characteristics these errors are negated in calculations without the need to use parameter ranges or error tolerance. Such calculations result in an accurate calibration of the distance measurement used by the onboard computer provide greater positional accuracy than relying on fixed balises alone. The onboard computer is preferably adapted to receive data from a wheel revolution counter, and wherein the data from the wheel revolution counter and the mean wheel radius of the rail vehicle are used to calculate the distance the rail vehicle has travelled. The calibration of the distance measurement used by the onboard computer may be carried out before the rail vehicle enters service. Alternatively, or additionally, the calibration of the distance measurement used by the onboard computer is carried out periodically whilst the rail vehicle is in service. An alarm may be sounded to a driver of a rail vehicle if the calibration process indicates an issue in the odometry system, or the system may choose to bring the train to a stand. . The input rail vehicle characteristics are preferably received by accessing a data storage device in the rail vehicle. The input rail vehicle characteristics are input using a data input device by technician. The independently verified rail vehicle characteristics are preferably received from a trackside system. The present invention provides, in a second instance, a data-processing system adapted to calibrate a distance measurement used by an onboard computer installed on a rail vehicle, comprising: a processor adapted to receive an input set of rail vehicle characteristics; receive a set of independently verified rail vehicle characteristics; calibrate the input set of rail vehicle characteristics using the set of independently verified rail vehicle characteristics to produce a calibrated set of rail vehicle characteristics; on the basis of the calibrated set of rail vehicle characteristics, calibrate the distance measurement used by the onboard computer based on the calibrated set of rail vehicle characteristics, wherein the set of independently verified rail vehicle characteristics comprises a mean calibrated wheel radius of the rail vehicle; and a receiver adapted to receive the set of independently verified rail vehicle characteristics and to communicate the set of independently verified rail vehicle characteristics to the processor. An alarm may be sounded to a driver of a rail vehicle if the calibration process indicates an issue in an odometry system of the onboard computer. Alternatively, the onboard computer may bring the rail vehicle to a stand if the calibration process indicates an issue with an odometry system of the onboard computer. In a further instance, the present invention also provides a rail vehicle comprising the data-processing system outlined above. Preferably, the rail vehicle is a train. The invention will now be described by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a data-processing system useful for carrying out methods in accordance with embodiments of the present invention; and Figure 2 is a flowchart illustrating the steps of a method in accordance with an embodiment of the present invention. Rather than using adjustments based on the data input by a technician to a DM I, a computer-implemented method of calibrating a distance measurement used by an onboard computer installed on a rail vehicle that relies on external data may be used instead. Initially, a set of expected rail vehicle characteristics is received. This may be data input via the DMI, or may be accessed from an accessible memory for rail vehicles with fixed formations. Next, a set of independently verified rail vehicle characteristics is received, which do not require any input or confirmation from a driver or technician. The expected set of rail vehicle characteristics is then calibrated using the set of independently verified rail vehicle characteristics to produce a calibrated set of rail vehicle characteristics. These are then used to calibrate the distance measurement used by the onboard computer based on the calibrated set of rail vehicle characteristics. The set of independently verified rail vehicle characteristics comprises a mean calibrated wheel radius of the rail vehicle. A data-processing system is provided as part of the onboard equipment to be able to carry out the method, as described in more detail below. The embodiments of the present invention are described in relation to the European Rail Traffic Management System (ERTMS), which is a signalling and traffic management system. However, they may also be carried out in conjunction with a Communication-Based Train Control (CBTC) system, or other train borne system where the onboard computer requires calibration. ERTMS has two main components: the ETCS and GSM-R (Global System for Mobile Communications - Railway). ETCS includes both trackside and on-board sub-systems. The trackside sub-system typically comprises the following elements: a Transparent Eurobalise (a transmission device that sends telegrams to the on-board sub-system); a Fixed Eurobalise (a transmission device that sends telegrams to the on-board sub-system based on pre-defined telegrams that are transmitted to every train); a Lineside Electronic Unit (LEU) (an electronic device that generates telegrams to be sent by a Eurobalise, based on information received from external track-side systems); Euroloop and Radio infill, which provide signalling information in advance; and Radio Block Centre (RBC) (a computer-based system that elaborates messages to be sent to the rail vehicle, based on information received from external track-side sub-systems and information exchanged with the on-board sub-systems using GSM-R). The onboard sub-system comprises on-board equipment responsible for supervising the movement of the train to which it belongs, on the basis of information exchanged with track-side sub-system by means of a Balise Transmission Unit (BTU) and / or Radio Transmission Unit (RTM), and possibly the on-board part of the GSM-R radio system according to the particular ETCS level. In particular, a European Vital Computer (EVC) is responsible for safety critical functions and is the unit with which many other train functions interact, including for example the odometer. Whilst in the examples below the onboard computer is an EVC, the onboard computer may be any computer suitable for determining the distance travelled by a rail vehicle. The Driver Machine Interface (DMI) is the interface between the driver and the on-board equipment, and is typically located on the driver's desk. The DMI preferably has a display screen that may be touch-sensitive and / or have buttons to permit the driver to input data, request permission to move and acknowledge certain events. A Train Interface Unit (TIU) provides the interface between the onboard equipment and other systems of the train such as the brake interface. A Juridical Recorder Unit provides 'black box' functions, storing the most important data and variables from train journeys to allow later analysis. Figure 1 is a schematic diagram of a data-processing system useful for carrying out methods in accordance with embodiments of the present invention. The data-processing system 10 comprises elements within the ERTMS system outlined above. A processor 11 is provided, which in this is example is in an ERTMS set up and preferably sits within a European Vital Computer (EVC) 12. A radio transmission unit (RTM) 13 acts as a receiver to enable communication of independently verified rail vehicle characteristics to the processor 11, and sits within a GSM-R radio system 14. A location device 15 is adapted to determine the geographical location of the rail vehicle and to provide this to the processor. The location device 15 may be a GSM (Global System for Mobile Communications) device hosted within the GSM-R radio system 14, or a separate GPS (Global Positioning System) device. An accessible memory device 16 is adapted to store details of wheel radii input by a technician during maintenance, and is accessible by the processor 11. This again forms part of an EVC 12 in this example. A display device 17 is provided and adapted to display the recommendation for rail vehicle operation, which in this example forms part of a Driver Machine Interface (DMI) 18. The processor 11, receiver 13, location device 15, accessible memory device 16 and display device 17 are connected via a data bus 19, to allow data communication between each of the elements of the data-processing system 10. The DMI 18 is also provided with a user input device 20 adapted to receive the input set of rail vehicle characteristics from a user. Since the user input device 20 is part of the DMI 18, the user input device 20 is also connected to the data bus 19. The processor 11 is adapted to receive an input set of rail vehicle characteristics from either the accessible memory device 16 or from a technician via the DMI 18, as well as to receive a set of independently verified rail vehicle characteristics, typically via the radio transmission unit 13 from the RBC or via a Balise Transmission Unit (BTU) 21. The processor 11 is also adapted to calibrate the input set of rail vehicle characteristics using the set of independently verified rail vehicle characteristics to produce a calibrated set of rail vehicle characteristics. Figure 2 is a flowchart illustrating the steps of a method in accordance with an embodiment of the present invention. The computer-implemented method 200 begins at step 202 with the processor 11 receiving an input set of rail vehicle characteristics, which contain at least the weight and gauge of the rail vehicle as well as wheel profiles. At step 204, the processor 11 receives a set of independently verified rail vehicle characteristics. These are obtained from a trackside system that is capable of measuring the weight and gauge of a rail vehicle as well as information regarding the profile of the wheels and retrieving data from the RBC. For example, a Weight-in-Motion (WIM) system may be used, comprising an axle weight sensor mounted on each rail of a railway track to measure the relative weight of each wheel of the rail vehicle as it travels along the railway track. A LiDAR scanning system is also suitable for use in determine the radius of the wheels, and may be the preferred implementation in some locations. A wheel impact load detector (commonly referred to as "WILD"), such as a strain gauge system attached to each rail is used to measure the impact each wheel has on the rail in passing. This produces a load profile for each wheel, which is then used to determine the wheel condition. Fibre optic acoustic sensing (also known as FOAS) may also be used, in particular, utilising fibre optic cables that are already present trackside for signalling purposes. A frequency or amplitude spectrum obtained as a rail vehicle passes a measurement point on the fibre optic cable will have a broad curve with smaller peaks superimposed. Alternatively, a laser system may be used, in conjunction with a high speed camera. At step 206 the processor calibrates the input set of rail vehicle characteristics using the set of independently verified rail vehicle characteristics to produce a calibrated set of rail vehicle characteristics. At step 208, on the basis of the calibrated set of rail vehicle characteristics, the processor 11 calibrates the distance measurement used by the EVC 12. The set of independently verified rail vehicle characteristics comprises a mean calibrated wheel radius of the rail vehicle, as described in more detail below. In the case where a LiDAR scanner is used to measure wheel parameters, a map showing the visible portion of each wheel as it passes the LiDAR device is obtained. Since the distance to the wheel is known, it is possible to determine the length of a segment 5 of the wheel and the central angle t? at the centre of the wheel that the segment S makes. Using the formula for the radius of the wheel R, R = dS the diameter of the wheel D can be calculated. If a WILD system is used, the spectrum obtained may be analysed to determine the diameter of the wheels. For FOAS, the smaller peaks of the spectrum represent each axle and therefore wheelset passing the measurement point, and therefore the breadth of each smaller peak represents the circumference of a wheel. For typical bogies two separated sub-peaks will be present, one for each wheelset. This circumference can then be used to calculate the wheel diameter. Where images are captured, the segment method above may be used together with automated image analysis to determine the diameter of the wheel. For all methods, the wheel diameter or radius is determined for at least two wheels, and used to generate a mean calibrated wheel radius, which then becomes a member of the calibrated set of rail vehicle characteristics. It may be preferable to use a single wheelset to determine mean calibrated wheel radius or all of the wheelsets on a rail vehicle. A tolerance factor may be used to create an acceptable range within which the calibrated wheel radii sit if required. In order to determine a calibrated distance, the EVC 12 also receives data from a wheel revolution counter, which enables a calculation of the distance the rail vehicle travels. In the United Kingdom, a new wheel for a passenger train has a diameter of 840mm, but wheel sizes on other rail vehicles including locomotives and freight may be in the range of 600mm to 1100mm. However, the wheel may be reprofiled several times during its lifetime before being discarded. But using wheel revolution data, for every 200 revolutions there may be up to 50m difference in the distance travelled by a wheel with a diameter of 840mm compared with one at 800mm, say. This may easily cause one passenger train to appear to have "jumped" another since actual and calculated distances travelled will differ significantly to a signalling system. The calibration of the distance measurement used by the onboard computer is typically carried out before the rail vehicle enters service, at the point where other vehicle checks take place. However, it may also be desirable to carry out the calibration of the distance measurement used by the onboard computer is carried out periodically whilst the rail vehicle is in service. 5 Indeed, it may be particularly advantageous to use more than one of the wheel diameter and radius measuring options outlined above to generate the mean calibrated wheel radius. Using more than one independent measurement mechanism increases the accuracy of the final distance calculations. However, an alarm may be sounded to a driver of a rail vehicle if the calibration process indicates an issue in an odometry system of the onboard computer. Alternatively, the 10 onboard computer may bring the rail vehicle to a stand if the calibration process indicates an issue with an odometry system of the onboard computer. All of the independently verified rail vehicle characteristics are received from a trackside system. The input rail vehicle characteristics are received by accessing a data storage device in the rail vehicle, with the input rail vehicle characteristics being input from a data input device by a technician. Preferably, in the examples 15 and embodiments outlined above, the rail vehicle is a train. These and other advantages of the embodiments of the present invention falling within the scope of the appended claims will be apparent to the person skilled in the art.

Claims

1. A computer-implemented method of calibrating a distance measurement used by an onboard computer installed on a rail vehicle, comprising:receiving an input set of rail vehicle characteristics;receiving a set of independently verified rail vehicle characteristics;calibrating the input set of rail vehicle characteristics using the set of independently verified rail vehicle characteristics to produce a calibrated set of rail vehicle characteristics; and calibrating the distance measurement used by the onboard computer based on the calibrated set of rail vehicle characteristics;wherein the set of independently verified rail vehicle characteristics comprises a mean calibrated wheel radius of the rail vehicle.

2. Computer-implemented method as claimed in claim 1, wherein the onboard computer is adapted to receive data from a wheel revolution counter, and wherein the data from the wheel revolution counter and the mean wheel radius of the rail vehicle are used to calculate the distance the rail vehicle has travelled.

3. Computer-implemented method as claimed in claim 1 or 2, wherein the calibration of the distance measurement used by the onboard computer is carried out before the rail vehicle enters service.

4. Computer-implemented method as claimed in any of claims 1, 2 or 3, wherein the calibration of the distance measurement used by the onboard computer is carried out periodically whilst the rail vehicle is in service.

5. Computer-implemented method as claimed in any preceding claim, wherein an alarm is sounded to a driver of a rail vehicle if the calibration process indicates an issue with an odometry system of the onboard computer.

6. Computer-implemented method as claimed in any preceding claim, wherein the onboard computer brings the rail vehicle to a stand if the calibration process indicates an issue with an odometry system of the onboard computer.

7. Method as claimed in any preceding claim, wherein the input rail vehicle characteristics are received by accessing a data storage device in the rail vehicle.

8. Method as claimed in claim 7, wherein the input rail vehicle characteristics are input using a data input device by a technician.9 Method as claimed in any preceding claim, wherein the independently verified rail vehicle characteristics are received from a trackside system.

10. A data-processing system adapted to calibrate a distance measurement used by an onboard computer installed on a rail vehicle, comprising:a processor adapted to receive an input set of rail vehicle characteristics; receive a set of independently verified rail vehicle characteristics; calibrate the input set of rail vehicle characteristics using the set of independently verified rail vehicle characteristics to produce a calibrated set of rail vehicle characteristics; on the basis of the calibrated set of rail vehicle characteristics, calibrate the distance measurement used by the onboard computer based on the calibrated set of rail vehicle characteristics, wherein the set of independently verified rail vehicle characteristics comprises a mean calibrated wheel radius of the rail vehicle; anda receiver adapted to receive the set of independently verified rail vehicle characteristics and to communicate the set of independently verified rail vehicle characteristics to the processor.

11. A rail vehicle comprising the data-processing system of claim 10.

12. A rail vehicle as claimed in claim 11, wherein the rail vehicle is a train.

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