Diagnostic systems for trains

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Faculty of Mechanical Engineering

Summary

This article presents the results obtained during the implementation of a portable diagnostic system in maintenance routines of the vehicles of passengers and permanent track of the Metro de Medellín Ltda. Company, which allowed to evaluate such aspects as: safety, comfort and technical condition of the track-vehicle interphase.

The reports given in this evaluation allowed to identify and to arrange track sec-tions according to their technical condition, associating in this way track condition parameters and the vehicle with the estimators associated with the dynamics of pas-senger vehicles.

Keywords: diagnostic system, technical condition, safety, comfort, dynamic state 1. Introduction

International standards for the railroad determine procedures and tests that must be carried out in order to evaluate different railway components. The Metro de Medellín company and the investigation group GEMI (Group of Studies in industrial Maintenance) of the EAFIT University with COLCIENCIAS's support conducted a study of dynamical behaviour of passenger vehicles, taking as a base the UIC 518 international norm (International Union Of Railways), with a goal to check a current operation condition of the railway system.

This international norm contains all the indications for railway rolling stock tests from the point of view of its dynamical behaviour, with the goal to evaluate safety aspects, track fatigue and running conditions (stability, comfort, etc.). Besides, it establishes measurement conditions of track condition parameters in different test zones (tangent and small and large radius curves), such as horizontal and vertical alignment, cant insufficiency, and others.

Additionally, it considers operation variables such as the speed of a passenger vehicle. Meas-urement points, automatic and data statistics processing conditions, quantities measured in evalua-tion with its respective limit values are specified in the norm.

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Bogdan ĩółtowski

Diagnostic systems for trains 189

2. Portable diagnostic system

To fulfil the requirements of that norm, Portable Diagnostic System was developed (see fig. 1) for the track-vehicle interphase of the Metro de Medellín system.

Fig. 1. Portable diagnostic system

Portable Diagnostic System (SPD) is constituted by modules that allow to evaluate safety as-pects, comfort and track-vehicle interphase state condition (fig.2); besides, it offers recommenda-tions to determine the following diagnosis term.

Fig. 2. Portable diagnostic system – SPD

Portable diagnostic system (SPD) has equipment named MGCplus by the HBM company that acquires and includes physical variables such as forces and accelerations, which are acquired in the railroad at different typical points by means of force transducers, unidirectional and triaxials acelerometers. The sampling frequency of the system is equal to 400Hz. The hardware is config-ured through a specialized software for this application type, which allows to configure capture parameters, register and data processing, as well as to recalibrate instruments, to store measure-ments, to process data (signals filtered and window) and to draw results. Figure 3 shows SPD acquisition system configuration, with force and acceleration transducers, the data processor and the computer to realize the respective configuration from the software.

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Fig. 3. Acquisition system of the SPD

In fig. 4 a force signal measured in the motor vehicle axle top appears. This signal allows to calculate lateral forces that are generated in a vehicle along the track which are necessary for safety evaluation.

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Fig. 4. Force signals measured in a passenger vehicle

In fig. 5 an acceleration signal appears, which is measured in the front part of a vehicle box during a test route; this sign allows the SPD to create necessary estimators to evaluate the running quality or comfort in a passenger vehicle.

Fig. 5. Acceleration signal measured in a passenger vehicle

Difference force and acceleration sensors are located in vehicle load points following the norm guidelines; for this purpose, devices allowing sensor installation, without affecting vehicle normal operation at the time of the tests were made. Fig. 6 illustrates the axle top where the force and acceleration transducers are installed under the UIC 518 norm criteria.

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Fig. 6. Transducer installation in the passenger vehicle axle top

The UIC 518 norm establishes two test methods to evaluate the railway systems rolling stock conditions; simplified and normal method. This last one was the implemented by Sistema Metro.

SPD system registers operation speed and generates train position vector in the track – indis-pensable data to determine section length and location (levels or geographical) that expires along with the norm requirements.

Such s coordinate system is used in the UIC norm. The axle X becomes positive in the run-ning direction; the Z axle becomes positive vertically up, and the Y axle is orthogonal to the other two, that is in a transverse direction (figure 7).

Fig. 7. Coordinate system according to the UIC 518 norm

To implement the norm, it became necessary to recognize different sections in tangent tracks – small and large radius curves, which were checked according to the norm requirements with regards to lengths, contact geometry (cant, alignment, equivalent conicity, etc.) and operation speeds, giving as a result a zone test with its respective speeds and radius, as figure 8 illustrates.

Cant track insufficiency (see figure 9) is reflected in evaluation reports of the curves in the vehicle tests.

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Fig. 8. Track sections according to speed and radius curves

Cant insufficiency in the curves is defined as the balance between the theoretical cant (design) and the real cant according to the relation:

Preal= Pdesign – Pinsufficiency. (1)

Fig. 9. Insufficiency of the cant of the road

In figures 10 and 11 different recommended values in the norm appear, as for cant insuffi-ciency and alignment that must fulfil the tests zones.

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In order to obtain homogeneous data in different test zones, the norm suggests to classify track state condition; for this purpose, indicators associated with standard deviation of vertical and horizontal track alignment are in use (see figure 11).

Fig. 11. QN1 and QN2 indicators of track alignment state, according to the UIC 518 norm Lateral and vertical alignment recorded in the SPD reports is obtained from records of a machine that performs alignment activities in the permanent track of the Metro system.

Fig. 12. Track alignment for sections where the UIC norm is implemented

For normal approval purpose of the vehicles, geometric quality is based on track maintenance criteria, represented in two quality levels:

- QN1 – It refers to the value that needs observation of the track condition or measurements acquired as a part of usually planned maintenance actions.

- QN2 – It refers to the value for which short term maintenance actions are required. The Metro de Medellín system applies to the values that corresponds to speeds which are minor or equal to 80 km/h.

For the evaluation of safety aspects, running behaviour and track fatigue, serial estimators and previously described acceleration force measurements are calculated. For different tests zones, a maximum estimated value is defined, which represents the railway system state condition once it is compared with its respective limit value. It’s as follows:

s

k

x

ˆ

max

=

+

⋅

(2) where:

x

: arithmetical average, s : standard deviation,

k : confidence level factor selected, like: k = 3 for the safety aspect.

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k=2.2 for the track fatigue and the running behaviour k = 0 for quasi-static quantities.

In the evaluation reports of the Portable System of Diagnosis one finds a value named coefficient λ, which is the relation between the limit value and the maximum estimated value, according to the following relation:

min Valor Limite Valor M aximo Estimado

λ= §¨ ·¸

In figure 13 an example of measured values in small curve test zones is shown; in this figure different variables defined in previous paragraphs are presented.

Fig. 13. Report presentation 3. Results of the portable system of diagnosis – spd implementation

Next, the results obtained of the UIC 518 norm implementation in passenger vehicle fleet of the Metro de Medellín are shown, using a sample of eighteen vehicles.

In figure 14, the RMS maximum value estimated of the guide forces obtained in the different passengers vehicles is presented. It is possible to deduce that this estimator is changeable in different vehicles because of the condition of the track-vehicle interphase properties, such as: thickness and wheel flange height and diameters differences in the same unit and others.

Fig. 14. Safety results compared with UIC 518 norm criteria

In figure 15 and 16 different needed estimators in a three-dimensional way are shown to evaluate the comfort in passenger vehicles and track fatigue. The surface above the values repre-sents the limit value established by the norm. Likewise, due to vehicle exploitation record, it shows different results.

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Fig. 15. Comfort results compared with UIC 518 norm criteria

Fig. 16. Fatigue results compared with UIC 518 norm criteria

In final investigation report, all the estimators concerning safety, comfort and fatigue evalua-tion for passenger vehicles are grouped, as shown in figure 17.

Fig. 17. Grouped results compared with UIC 518 norm criteria 4. Conclusions

1. The implementation of UIC 518 international norm in passenger vehicles took place in real exploitation conditions of Metro trains. The innovation of these norms is principally associ-ated with rolling elements and special conditions of measurement.

2. The sections associated with norm evaluation will allow to establish new political mainte-nance based on the technical condition of the track-vehicle interphase.

3. The results of investigations allow the Metro company to improve safety, comfort and quality service during exploitation.

4. The information recorded in the final investigation report is a way to define new challenges in the maintenance of technical complex systems.

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Bibliography

1. Norma UIC 518: Testing and approval of rail-way vehicles from the point of view of their dynamic behaviour – safety-track fatique – ride quality, UIC code, 2003.

2. Cempel C.: Multi-dimensional condition monitoring of mechanical systems in operation. Mechanical Systems and Signal Processing, Poznan University of Technology, 2003. 3. International Heavy Haul Association, Guidelines to Best Practices for Heavy Haul Railway

Operations: Wheel and Rail Interface Issues, Virginia Beach, Va., May 2001.

SYSTEM DIAGNOSTYCZNY POCIĄGU Streszczenie

W artykule przedstawiono wyniki z badaĔ wdroĪeniowych przenoĞnego systemu diagnostycznego zastosowanego do oceny wagonów pasaĪerskich Metra. Badania te prowadzone były w aspekcie bezpieczeĔstwa i komfortu jazdy oraz oceny zmian sta-nu technicznego. Wyniki badaĔ zawarte w sygnałach drganiowych, odzwierciedlały stan dynamiczny wagonów w czasie jazdy.

Słowa kluczowe: system diagnostyczny, stan techniczny, bezpieczeĔstwo, komfort, stan dyna-miczny

* This paper is a part of WND-POIG.01.03.01-00-212/09 project.

Bogdan ĩółtowski

University of Technology and Life Sciences Faculty of Mechanical Engineering