Increased efficiency of train operations
The efficiency of a traffic management system is dependent on the reliability of the train detection system, as well as other connected functions, such as level crossing systems
Inductive wheel sensors and axle counters use state-of-the-art technology to provide train position information to traffic management systems and level crossings alike.
As these components form the base for a broad range of relevant applications, robustness and high availability must be guaranteed even under changing conditions. Based on global experience, Frauscher Sensor Technology is continuously developing its portfolio to optimise existing and develop new products which can meet specific requirements all over the globe.
In this article several specific requirements and appropriate solutions will be introduced.
Built to withstand
The main task of a wheel sensor lies in the reliable and precise detection of each passing train axle. Mounted to the track these sensors are working in an environment which is sometimes exposed to extreme conditions: very low or high temperatures, natural events, such as lightning strikes or floods, as well as mechanical and electromagnetic influences.
The reliability of inductive wheel sensors is largely dependent upon the ability of the wheel sensor to handle these conditions.
Improving temperature stability
Over the years the experts at Frauscher became convinced that sensors installed worldwide must function at temperatures ranging from -60 °C to +85 °C. It must be guaranteed that the functionality of the sensor is not affected even by swift changes, for example when the weather changes from sunshine to heavy rain.
A solution for this can be seen in the development of intelligent algorithms, such as those which have been implemented in the improved version of the Frauscher Wheel Sensor RSR123.
Ruggedness in all parts
To optimise its sensor’s stability against mechanical influences, Frauscher arranged testing stations at its laboratories to simulate even extreme impacts. To increase a sensor’s resilience, it also has to be guaranteed that it continues to work when completely set under water. Combining the experience gained from international projects and innovative development processes which included such tests has, for example, led to an optimisation of the tried-and-tested Wheel Sensor RSR180.
This sensor’s potting compound has been enhanced in order to further improve its robustness and the electronic components and their inner workings have also been optimised. The new version of the RSR180 will be presented towards the end of this year.
The challenges arising from mechanical influences do also concern the mounting assembly, which must ensure that the position of the sensor does not change under extreme stress. These include vibrations caused by flat spots on wheels, defective rail joints, broken rails or metal parts hanging from a train.
Appropriate developments have for example been made to the Frauscher SK150 rail claw, the components of which were designed to withstand peak stress levels of 2,500 m/s². However, during an evaluation carried out prior to the installation of this model in other markets, stress measurements of over 50,000 m/s² were recorded.
In order to ensure that the sensor remains in the correct position on the track when subjected to these extremely high forces, the clamping bolt material has been changed to increase the robustness of the bolts and to allow them to withstand the given impacts.
Defy electromagnetic influences
Wheel sensors used in the rail sector work on the highly sensitive evaluation of changes to inductive parameters. On the one hand, this allows for the precise detection of passing train axles, but it also requires the intelligent handling of the various electromagnetic influences present in the field.
These can be caused by equipment and infrastructure, such as eddy current brakes and neutral sections or by natural events, such as lightning strikes.
As international projects have revealed individual cases which required further adaptation, Frauscher is continuously developing its sensors in terms of their resilience against such influences.
Fundamental data for the optimisation of products with regard to new requirements is frequently determined using the Frauscher Magnetic Noise Receiver MNR – a mobile measuring system for analysing magnetic fields generated by vehicles. The MNR makes it possible to detect, record and evaluate magnetic fields on the track in real time.
Valuable information regarding the approaches to optimisation can be obtained as a result, both at the project-planning phase and throughout the course of the project. In some places, opportunities can be identified for adapting rolling stock to bring about uniform frequency management in the sensor application area.
Maximising the system’s availability by intelligent fault tolerance
In addition to ensuring the maximum quality of wheel sensors, intelligent, fault-tolerant functions, provided by modern axle counters such as the Frauscher Advanced Counter FAdC, can ensure smooth operation even in the event of a fault – particularly if caused by external influences.
With the aid of these functions, the availability of the complete system can be further increased in a cost-effective manner.
Suppression of faults
The counting head control principle (CHC) is used to avoid error messages caused by inevitable influences. If the adjacent track sections are clear, the counting head is switched to a stand-by mode.
In this idle state, a freely configurable number of undesirable instances of damping can be suppressed. This means that no fault or occupied indication is generated by a short-term influence; no reset is required.
Approaching vehicles deactivate the stand-by mode, meaning that they are detected and the occupied status output is issued in a failsafe manner. When used correctly, the patented functionality satisfies the safety requirements according to SIL4.
Automated fault correction process
The intelligent supervisor track section process (STS) corrects inevitable external interference in a fully automated manner. By observing the general reset conditions, it is possible to further optimise availability without any negative effect on safety. Every two track sections are overlaid by a supervisor section.
Consequently, it is possible for a faulty track section to be reset automatically, without manual intervention, if the corresponding supervisor section is clear. Similarly, a faulty supervisor section is reset if the two corresponding track sections are clear.
As an expert in inductive sensor technology, Frauscher has been conducting fundamental research in this area for 30 years and it has combined its practical experience, gained from various projects, with the analysis and evaluation of faulty devices.
A total of 140,000 sensors in use in more than 80 countries around the world form the basis of a knowledge database for continuous optimisation.
By combining experience-based optimisation with tailored services, by staff in railway markets all over the globe, Frauscher is able to provide its customers with solutions that meet their requirements in an optimum way – which really allows them to track more with less.
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