DB Systemtechnik - Digitale Automatische Kupplung (DAK) DB Systemtechnik - Digitale Automatische Kupplung (DAK) | HBM

Rail subsidiary uses rugged mobile measurement technology from HBK for trialling and approving the digital automatic coupling (DAC)

In June 2020, the German Federal Ministry for Digital and Transport (BMDV) launched a national research project in preparation for the Europe-wide introduction of the digital automatic coupling in rail freight transport. Which of the prototypes presented would turn out to be suitable? In the first test phase, rugged and reliable measurement technology from HBK played a large part in finding this out.

The BMDV’s research project, “DAC Demonstrator – Pilot Project for the Demonstration, Testing and Approval of the Digital Automatic Coupling (DAC) for Rail Freight Transport”, is divided into two phases and will end in December 2022. Members of the consortium contracted to carry out the project, DAC4EU, (Digital Automatic Coupling for Europe) include Deutsche Bahn AG and its subsidiary DB Cargo AG. On the German side, DB Systemtechnik GmbH was responsible for putting the various coupling designs to the test in Phase I. Here, the engineers subjected prototypes from four manufacturers to extensive tests to determine their suitability in everyday use. To achieve reliable and precise measurement results despite the harsh environmental conditions, they relied on the rugged SomatXR measurement technology series from HBK.


DB Systemtechnik GmbH was contracted by Deutsche Bahn AG to trial four different digital coupling prototypes. In order to describe their behavior during predefined test runs, they needed a large quantity of measurements of mechanical variables, the signals of which had to be recorded simultaneously. In addition, the measurement results had to be precise and reproducible, despite adverse external conditions.


For the test, DB Systemtechnik used the SomatXR series from HBK. Its perfectly harmonized components – universal measurement module, data recorder and accessories – are ideally suited to mobile use in tough environments.


Thanks to HBK’s SomatXR measurement technology, DB Systemtechnik was able to precisely document the mechanical behavior of the various digital coupling prototypes. The system reliably recorded and processed large volumes of data from numerous different measurement tasks over a long period of time. Based on this evaluated data, a European committee chose the best coupling design for the future launch in Europe. This design is now undergoing further experiments and tests.

In Phase I of the DAC project, the aim was to describe the behavior of the different couplings as accurately as possible, and to evaluate it. First, the teams headed by project manager Dr. Christian Wilmes put together four groups of railroad cars, each with three cars of different designs. The couplings under test were installed between the cars. Steel wire containers or switch boxes of measurement technology attachments were installed in the cars.

At the test facility of TÜV SÜD Rail GmbH in Görlitz, the team then conducted hundreds of tests under varying conditions in terms of velocity, payload, and rail geometry, in order to document the mechanical and electrical behavior of the coupling prototypes and the stability of data communication. Tests were also performed in DB Systemtechnik’s climatic chamber, to simulate different – and also extreme – weather conditions. Further details on the Phase I test can be seen in the test concept in Phase I – DAC4.

In order to accurately record the mechanical behavior of each coupling prototype, the team at DB Systemtechnik had defined a large number of measurement tasks, including coupling tests, test runs, and lateral force tests to determine safety against derailment. An overview of the measurement tasks can be seen in Fig. 1. For the measurements, the sensors were attached directly to the couplings and brake system and connected to the amplifiers via cables. The engineers used WLAN antennas for data exchange between the railcars. Batteries ensured a self-sufficient power supply, to enable measurements independent of location.

(tensile and compressive force in the train’s longitudinal (x) direction)

(of both the mechanical and electrical coupling; direction of measurement x, y, z)

(determining the pressure compensation after coupling and the pressure loss after a test run; also brake cylinder pressure)

(x, y, z direction)

(of both end cars when pushed onto the central car during coupling)

Fig. 1: Overview of measurement tasks

Fig. 2: Layout of measurement technology                                                                                                   

(Source: DB Systemtechnik/60226-02-DAK-Phase I - Messtechnik [DAC Phase I - Measurement Technology]; p. 10)

Optimum measurement technology for mobile use

It was no coincidence that HBK was chosen to supply the measurement technology for the mechanical tests. Back in 2017, DB Systemtechnik and HBK had successfully collaborated on a freight train project. The measuring instruments from the SomatXR series – still in use today – could be added to and upgraded without problem (see Fig. 3). For the client, the advantages of this system were obvious:

  • The rugged design guarantees precise measurement results even under harsh ambient conditions.

  • The decentralized, modular setup enabled the wiring on each coupling to be isolated so that separate measurements could be performed for each railcar.

  • All measurement signals were recorded synchronously at the desired data rate.

  • The measured data was transmitted wirelessly to the data recorder.

  • The sensor signals underwent optimum processing thanks to the 8 universal channels of the MX840B-R and the 16 channels of the MX1615B-R.

  • The measurement results could be reproduced at any time and were therefore suitable for accreditation.

  • The plug-and-measure configuration ensured intuitive operation.

  • HBK Service and Support was on standby for immediate assistance when needed.

Thanks to these good experiences, the specialists at DB Systemtechnik were convinced that HBK technology would overcome the challenging requirements of the DAC pilot project. For project manager Dr. Christian Wilmes, HBK is simply standard: “I’ve been working with these measuring instruments since college. It’s like MS Office. I just know how it works,” he says, emphasizing the user friendliness of the technology. And he doesn’t hold back on praise for support, either: “A cell phone in one hand, an instrument in the other; that’s how we quickly resolved any problems, including late at night, with HBK’s help.”

SomatXR components used in the DAC project

Amplifier (here: modules MX840BR and MX1615B-R)

Rugged universal amplifier for a variety of measurement tasks

Data recorder CX22B-R

Interactive, rugged recorder for stand-alone field operation without PC.

Switch EX23R

Rugged Ethernet switch with 10 GB Ethernet ports for connecting SomatXR measurement modules and accessories.




Data acquisition, visualization and analysis


Fig. 3: HBK measurement technology used in the DAC project

Fig. 4: Measurement chain block diagram                                                                                           

 (Source: DB Systemtechnik/60226-02-DAK-Phase I - Messtechnik; p.13)

Table: Key to Fig. 4: Measurement chain block diagram                                                           

 (Source: DB Systemtechnik/60226-02-DAK-Phase I - Messtechnik; p.13)

Rugged and reliable: For mobile measurement tasks, HBK is the only way

When the Phase I testing and evaluation of measured data was complete, a European committee selected one of the prototype designs as the future DAC design for Europe. Prototypes of this design are currently undergoing field tests in Phase II of the project in Germany, Switzerland and Austria. Further EU countries will follow. The aim is to get the chosen coupling design ready for production.

Further information on project progress can be found at https://www.dac4.eu/

Rugged and ever-reliable measurement technology from HBK made a vital contribution to the qualification of digital couplings in Phase I of the DAC pilot project. This was just a first but very significant step toward the digitalization and automation of rail freight transport. Here and wherever reliable mobile data acquisition is needed on-road, off-road or on the railroad track, HBK offers the perfect solution.

Fig. 5: Measuring instrument setup in the measurement technology container                                               

(Source: DB Systemtechnik/60226-02-DAK-Phase I - Messtechnik; p.11)

About DB Systemtechnik

DB Systemtechnik is Europe’s leading competence center for rail technology and the consulting engineer office for DB AG. As the provider of a complete range of services, DB Systemtechnik not only provides the parent company with technical support – it also offers customers around the world customized solutions for safe, reliable, and customer-oriented rail operations. The company, with business units “Engineering services” and “Approval management, testing and certification”, has around 1,100 employees at 15 sites in Germany and at four sites elsewhere, and boasts 13 accredited test laboratories.