Mixed technology for more information
Mixing wisely for real added value: When Distributed Acoustic Sensing (DAS) is linked to axle counters and inductive wheel sensors, valuable information can be generated for railway applications.
In the field of signalling technology, axle counters and wheel detection systems based on inductive wheel sensors are often used for data collection purposes. These provide single-point, yet highly accurate data on train detection, the number of axles, speed or the direction of travel. For solutions based on Distributed Acoustic Sensing (DAS), data is continuously collected and evaluated as real-time information. In 2016, as the market leader in wheel detection and axle counting, Frauscher combined its tried-and-tested products with DAS to form the Frauscher Tracking Solutions FTS. This marked a crucial step forward.
The networking of data from various systems increases the level of efficiency and safety in the rail sector.
Potential draws global interest
The revolutionary potential of the basic physical principle was already apparent during the evaluation of the use of DAS in the railway sector. Since then, together with interested operators, system integrators and research institutes, Frauscher has already developed fundamental concepts and ideas and set up various installations.
From the experience gleaned, new approaches were and continue to be realised for other applications. At the same time, it became apparent that further optimisation would require close cooperation and the open exchange of information, along with a joint analysis and assessment of the results.
A single fibre is sufficient
Installing the FTS is a very efficient way for operators to upgrade their infrastructure. The fibre optic cables needed are already in place along many routes, since they are often used for communication purposes. The fibre bundle only needs a single fibre to integrate the FTS. Vast sections of the route can therefore be expanded economically and efficiently.
Tests have shown that a single DAS unit can optimally cover up to 40 kilometres of glass-fibre. Various signatures of people on the track or travelling trains can be classified within this range. Persons and comparable acoustic sources can be detected within a radius of 5 metres from the fibre optic cable, whilst trains with a considerably higher acoustic energy level can even be detected at a distance of approximately 50 metres. These values are influenced by various factors, including the condition and quality of the cable, the type and site of routing and various surrounding sounds.
Cable quality and condition
Various versions of the fibre optic cables are available, which can effect the sensitivity. Whilst the quality and purity of the glassfibres co-determine the range, the material, strength and condition of the sheath can increase or restrict the sensitivity of the system.
Type and site of routing
Until now, ideal results were obtained with cables laid in a concrete cable tray or directly into the ground, running approximately three to five metres away from the track. Other methods, such as attaching the cable directly to the foot of the rail or to attachments near the track, might make it easier to detect certain acoustic sources. However, they prevent the parallel detection of other influences.
Since the FTS detects and classifies different incidents through its acoustic signatures, all acoustic sources in the vicinity of the track must be taken into consideration. All of these influences combined can lead to overlaying, which in turn must be taken into account in the evaluation. Corresponding filters can, for example, mask firmly located and routinely detected acoustic sources. Depending on the intensity of the acoustic emission, the distance of the acoustic source to the glassfibre also plays a role. This interaction can also cause weaker signatures, for example from steps, to be overlaid by stronger distinct signals, like a train.
A combination equals more output
By combining the inductive sensor and DAS technology, the FTS is able to offer the railway industry numerous new possibilities for data generation. Implementing data from the operator's other systems can improve the quality of the information even further, but also places special demands on interfaces and data formats. In test installations realised up to now, various applications have already been implemented in the fields of train detection, infrastructure monitoring and safety applications.
More information means better safety
The oil and gas industry successfully uses DAS for a range of safety applications. Adapting the corresponding algorithms for the railway sector was therefore one of the first steps to be taken when developing the FTS. This enables people and animals on or in the vicinity of the track to now be detected. It also allows various safety applications to be implemented, such as the detection of activities associated with vandalism or cable theft.
Passing on data and linking it with additional information further increases the potential of the applications. This means that interfaces to safety equipment can be used to provide alarm messages by email or SMS. Work crews can be accurately located and provided with information, for instance about approaching trains, via a direct connection on mobile devices. Even drones can be supplied with data which is then used to directly fly to a section to be controlled.
Safety along the whole line: Information about various activities can be forwarded directly to maintenance personnel via mobile devices, for example.
Condition monitoring: listen to your infrastructure!
When monitoring the condition of infrastructure and train components, the FTS can supplement or even reduce equipment installed trackside. For example, this allows flat spots on wheels or broken rails to be identified based on acoustic signatures. Rock falls can also be located and the corresponding information can be forwarded directly via radio to approaching trains. In accordance with the current state of the art, DAS-based systems do not allow you to assign identified signatures directly to a certain track. A decisive interface is therefore an interface to a wheel detection system which is used in parallel. If data from both systems is overlaid, certain incidents can be localised with even greater accuracy along the route. Integrating information from the operator's different databases can enrich this data pool even further: if train numbers are implemented, flat wheel alarms can be assigned to a specific train, and to a specific axle via the wheel detection system.
All components at a glance: Early detection of damage, caused either by rock fall or broken rails, increases operational safety and supports urgent repair work as well as predictive maintenance.
Real-time train tracking
The FTS make it possible for all trains within a monitored track section to be located in real-time. In non safety-relevant areas, they can also be used as a stand-alone solution, i.e. without integrating an axle counter or wheel detection system. Since no specific equipment has to be fitted to the vehicles, their design and origin are insignificant. The information obtained provides considerable benefits for traffic management. In remote areas, this technology can provide a costeffective and efficient solution to controlling systems.
Integrating an axle counter, for instance the Frauscher Advanced Counter FAdC, makes it possible for the DAS-based realtime tracking of trains to be combined with safety-relevant applications. Associated interfaces enable level crossings to be controlled with even greater precision. Inputs from both systems can be combined in the Traffic Management System (TMS) in order to calculate accurate times of arrival, supply platform displays or to precisely coordinate and compose platform announcements.
Real-time train tracking: Data from the real-time train tracking can be used to optimise traffic management, for example for platform announcements and platform displays.
The knowledge gained so far shows that the chosen path to develop two parallel strategies will continue to hold true. On the one hand, existing components must be optimally linked to the new technology in order to generate additional information for different applications, quickly and at no extra cost.
On the other hand, new architectures need to be developed at the same time. Results from previous installations have contributed to associated concepts being intensified even further. It has become apparent here that, in particular, the networking of data from different sources offers great potential for optimising existing and developing new applications. The possibilities of a pre-evaluation of this data must now be driven forward in order to be able to efficiently extrapolate information and use it in a targeted manner. The requirements for data transmission and storage – as is the case in many other sectors – are therefore once again the topic of discussion in the railway sector.
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