Determining the Railway Track Condition

using the INS / GPS System

Emil Yonchev, Rossen Miletiev and Rumen Arnaudov

Technical University – Sofia, Sofia, Bulgaria

Abstract. The paper discusses the development of the “test vehicle” system for

preliminary test of the railroad. The test is accomplished on the basis of the own

developed systems for data storage based on the GPS receiver and inertial

sensors. All data are stored in the external energy independent memory

(FLASH) while the navigation data are sent to the navigation server via GPRS

network. The quality of the railway is determined according to the three axis

acceleration analysis while the GPS receiver defines the event position. The

experimental data are recorded on the selected part of the railroad and

furthermore are analyzed.

Keywords: Railway faults, GPS receiver, Accelerometer.

1 Introduction

Nowadays the railway geometry is measured by the high speed wagon measurement

tools like EM120 or EM250 [1]. These tools control the railway condition and

parameters, which are compared with the regulation technical data. The control is

performed according to the preliminary elaborated schedule while the time period

between two consecutive tests is defined as one year or higher. During this period it is

possible to emerge a digression at the railway geometry, which is a potential source of

an accident. This is the reason to develop a system, which may register the railway

places with increased risk to avoid the accidents during the exploitation time. This

system does not require any additional high – qualified personal or railway

equipment.

The “test vehicle” system is developed at [2]. The dangerous railway places are

recognized according to the effective values of the vehicle accelerations. Another

method is discussed at [3], where the proposed method for defect recognition is based

on wavelet transformations of the acceleration signals. This method requires a perfect

suspension state to guarantee the correct results. Another method for determination of

the railway deflection in the longitudinal direction is proposed at [4], which is based

on the acceleration of the vehicle terminal junction. Such type of test systems are also

proposed at [5] and [6] but their high cost limited their application in the railway

systems.

Yonchev E., Miletiev R. and Arnaudov R.

Determining the Railway Track Condition using the INS / GPS System.

DOI: 10.5220/0004463300710077

In Proceedings of the 3rd International Workshop on Enterprise Systems and Technology (I-WEST 2009), pages 71-77

ISBN: 978-989-674-015-3

2 “Test Vehicle” System Description

The “test vehicle” system is realized with the measuring system, described at our

previous work [7] (Fig.1), which is installed on a locomotive traveled regularly on the

selected route. The measuring system is mounted on the locomotive reduction gear to

ensure the system will measure only accelerations originated from the rails.

Car body

GPS/INS device

Suspension

Wheelset

Rail

Sleeper

Groun

Bogie

Fig. 1. Measuring system details.

The dynamics of the railway – locomotive interaction in the vertical direction may

be explained with the mathematical model shown at Fig.1. The frequency distribution

of the acceleration data vary from one axis to another. The maximum frequency of the

vertical and lateral fluctuations is limited from 0.5 to 1Hz. In the same time the

railway faults generate vibrations with a maximum frequency up to 2000Hz.

The force/translation (F/y) relation is described according to the equation:

.ycF

(1)

The connection between the wheel and the railroad is very tight, so the wheel

translation repeats the railway faults. If the railway quality is very good, the system

vibrations are provoked by the non – parallel rail position or rail defects.

The proposed system measures the accelerations of all three axes. The acceleration

data are recorded with the GPS navigation data as a data block per 1 second. One data

block contains 40 inertial data and 1 GPS message, so the time distance between the

inertial samples are defined as 0.025s. The traveled distance for each data block is

defined as follows:

мин

..2

≥Δ

(2)

where

мин

Δ - traveled distance,

t – time interval and v - vehicle speed. If

the maximum speed is limited to 60km/h, the traveled distance is equal to

мин

Δ =

0.833m.

The normative standards define the lateral acceleration maximum value. For

Bulgarian railway this value is set to 0.85m/s

. The maximum longitudinal

acceleration varies according to the vehicle speed, but its maximum value is set to

0.6m/s

. Esveld [8] defines the safety maximum accelerations of the French railway

company SNCF. These values are summarized at Table 1.

Table 1.

Transverse cart acceleration 6 m/s

Vehicle speed

V<350 km/h

Transverse crate acceleration 2.5 m/s

Vertical crate acceleration 3 m/s

These values may be used as recommended maximum values for inertial data

analysis.

3 Experimentation Results

The experiment is implemented for ten days while the test vehicle is driven on the

same route. The navigation and inertial data are recorded on MMC/SD memory card

and are simultaneously transmitted to the map server via GPRS network. Furthermore

the data are analyzed using MATLAB software tools.

The developed software tool allows to select the desired maximum acceleration

limit and to find the places where the previously defined limit is overcome. This

choice is made through GUI (Graphic User Interface) menu (Fig.2).

Fig. 2. Graphic User Interface menu.

The MATLAB tool also allows to select one or more days using alternative menu

(Fig.3).

Fig. 3. Alternative menu.

The basic criterion of the railway faults is based on the number of acceleration

values which overcome the selected maximum value. The analyzed railway length is

set to 80m. The distribution of the number of points where the acceleration exceeds

the limit is shown at Fig.4 (analyzed acceleration – X axis, maximum acceleration -

0.4m/s

Fig. 4.

Figure 5 also represents the number of points with exceeded acceleration on 3D

map. At this figure the latitude and longitude regions are divided to 100 bars to create

3D map.

When the points of interest are determined the tool may print that points which

acceleration exceeds a given number. Figure 6 represents such distribution when the

number of points of interest for some region exceeds the limit of 110 coincidences.



100

500

1000

1500

2000

Latitude bar

Longitude bar

Hits

X= 0 . 4 m / s s

Fig. 5.

23.3 23.35 23.4 23.45 23.5 23.55 23.6 23.65

42.66

42.68

42.7

42.72

42.74

42.76

42.78

42.8

Longitude

Latitude

Lateral acceleration X=0.4m/ss

Fig. 6.

The Z axis is also analyzed to specify the railroad condition. The limitation

value is set to 4m/s

and the obtained distribution of Z accelerations which exceed the

selected limit is shown at Figure 7.

0 100 200 300 400 500 600

100

120

140

160

180

200

Code of the points with equal coordinates

Number of the matches for a point

Distrbution of the matches when Z=4m/ss

Fig. 7.

The same distribution with shown latitude and longitude bars in 3D graphic is

shown at Figure 8. At this figure the longitude and latitude regions are also divided to

100 bars.

100

150

200

Latitude bar

Longitude bar

Hits

Fig. 8.

The limit number of matched points is set to 45 and the number of points of

interest are estimated from Figure 7 and their position are shown at Figure 9.

23.3 23.35 23.4 23.45 23.5 23.55 23.6 23.65

42.66

42.68

42.7

42.72

42.74

42.76

42.78

42.8

Longitude

Latitude

Vertically acceleration Z=4m/ss

Fig. 9.

4 Conclusions

The proposed “test vehicle” system may be used for preliminary test of the railroad

state to increase the safety level of the railways. As the system is permanently

installed on the locomotive, it constantly gives the actual information and may

warning for railway problems in a real time via GPRS network. When such condition

is found, the railway company may use standard measurement tools to establish the

real railroad state to increase the safety level.

References

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