On 11 March 2021, researchers from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) successfully completed a two-week series of tests focusing on the safe, efficient and flexible rail transport of the future. The research conducted at DLR aims to increase the proportion of passenger and freight transport conducted by rail, increase passenger comfort by reducing the number of changeovers during journeys, increase safety at railway crossings, and optimise route capacity by increasing the flexibility of train configurations. In order to achieve this, rail transport requires more automation. DLR is developing the necessary communication and navigation techniques with its cooperation partners to allow for such new approaches. The test journeys were carried out by two project teams from the DLR Institute of Communications and Navigation and ran from Halle to Augsburg via Göttingen, Berlin, Munich and Herrsching. The 'advanced TrainLab', a specially equipped high-speed train operated by Deutsche Bahn, was used as a mobile laboratory, complete with high-frequency communications technologies, special antennas and sensors on board.
In the V2X-DuRail project, the DLR team is paying particular attention to radio systems in the five-gigahertz frequency band, which allow secure communications between trains, parts of trains and carriages of a single train, and intersecting road traffic. In future, it will also be vital for the rail system to be able to reliably determine where a train is located, how long it is and whether it is still intact at any given time. The 'IMPACT' project team is developing a new method of localisation that uses measurements of Earth’s magnetic field and works under conditions that are unfavourable for satellite navigation.
Communication between trains and cars
The measurements recorded in the first week of March concentrated on the vehicle-to-everything radio for digital urban train communications (V2X-DuRail) project. Transport systems are set to become increasingly digitalised and networked in future. This will, for example, make railway crossings safer by enabling car and train drivers to be aware of one another. In rail transport, command and control systems for trains are being enhanced with wireless communication capabilities. Such channels could be set up to make better use of the available infrastructure and avoid collisions with other trains or cars. At the same time, cars are increasingly being fitted with radio-based communication systems that ensure an increase in the efficiency, comfort and safety of road traffic, while reducing environmental pollution. These radio systems are essential for networked and autonomous driving.
However, the radio systems used in road and rail transport today and in future can affect one another. This can lead to malfunctions, especially in urban areas with a high vehicle density. There may also be environments such as urban canyons or bridges that make reliable signal propagation difficult. Yet reliable communication is essential for critical safety-related applications.
Against this backdrop, the first series of tests carried out by the DLR researchers were based on determining which factors have what effect on radio transmissions and which countermeasures are effective. Various radio signals from other transport users were received and surveyed accurately within the test train, which was equipped with high-quality measurement technologies. In addition to the train, the project team also used two cars fitted with measurement equipment and a total of four different radio systems. The data obtained in this way can be used to make communications between trains and other transport users more reliable both now and in the future. The manoeuvres were coordinated using the Railway Collision Avoidance System (RCAS). This radio system, which is designed to prevent train collisions, was originally developed by DLR and is now available on the market via a spin-off company.
Position determination using Earth's magnetic field
Until now, trains have been localised to a section of track using axle counters at transition points. These sections of track can be several kilometres long and the axle counters are costly to set up and maintain. Satellite-based localisation technology is used only to a limited extent, in part because the signals it relies on cannot be received in tunnels. As part of the Intelligent Magnetic Positioning for Avoiding Collisions of Trains (IMPACT) project, DLR researchers are developing an autonomous on-board system that allows trains to precisely locate themselves on the track even under difficult conditions. The system makes use of the local strength of Earth's magnetic field and artificial intelligence.
Earth's magnetic field is altered by the presence of metals. The local pattern that is created, referred to as the 'magnetic field signature', is unique, similar to a fingerprint. It is therefore possible to distinguish between every single section of rail track. The magnetic field is measured with high precision and the unique signature determined allows for very reliable location determination.
In the second week of March, the IMPACT project team was able to test its localisation system in the field and measure real magnetic field signatures. To do this, they conducted measurements along the stretch of railway line between Göttingen and Kassel, which includes a lot of tunnels. The rolling laboratory reached a maximum speed of up to 200 kilometres per hour. The researchers also varied the points at which the measurements were made between the two directions of the reference track several times within a 10-kilometre tunnel. This would present a serious challenge for any train-based position determining technology.
In the future, this localisation system will also utilise machine learning to independently familiarise itself with relevant sensor parameters. This will make it easier to retrofit within existing vehicles. The new technology could not only greatly increase the safety of rail transport, but also its flexibility and efficiency as it would allow trains on a specific route to be operated at higher density.
Optimal route utilisation
Reliable wireless data transmission and high localisation accuracy for trains are also vital prerequisites for virtual coupling. When trains are no longer mechanically linked, they can be configured with a much higher level of flexibility. Carriages or wagons assigned to different routes could be coupled to one train, but transferred to other trains during the journey. Dynamic virtual coupling technology allows a lead vehicle to control one or more follower vehicles electronically. This will also help the rail network be more effectively harnessed through the increased density of train operations.
Now the IMPACT and V2X-DuRail measurement campaigns have been completed, the data will be evaluated by DLR in Oberpfaffenhofen. The knowledge acquired will help advance important technologies, from the development of prototypes, to the application and manufacture of products alongside industrial partners where necessary. In this way, the DLR Institute of Communications and Navigation is continuing to make advances in the digitalisation of rail transport and the harnessing of its potential.