RekuTrax research project


Sustainable and efficient transport solutions for the commercial vehicle industry make a decisive contribution to reducing global CO2 emissions. This is also the case with the "RekuTrAx" research project funded by the German Federal Ministry of Economics and Climate Protection (BMWK): The aim is to develop a demonstrator for a fully integrated, intelligent recuperation axle for truck trailers - and to prove that it can reduce the CO2 emissions of commercial vehicle fleets. As project sponsor, the German Aerospace Center is supporting the project. Four partners are implementing it together:


What is already standard in hybrid or fully electric vehicles can also be made possible in combustion engines through the use of a recuperation axle: Energy recovery via the drive train. The research project "RekuTrAx" stands for "recuperation carrier axle" and deals with precisely this issue. 



RekuTrAx - BPW Bergische Achsen
The BPW ePower generator axle supplies refrigerated transport vehicles with electricity, with zero power consumption and zero emissions.


The BPW ePower recuperation axle module recovers energy while the trailer is travelling and braking and can therefore supply refrigeration units for temperature-controlled transport with power quietly and without emissions. It makes the lorry trailer capable of recuperation independently of the tractor unit and thus promotes sustainable transport. The "recuperation carrier axle" of the "RekuTrAx" research project should make new utilisation options conceivable: Today, the recuperation axle can be used to power refrigerated trailers - perhaps soon it will also be used to power the tractor unit or other auxiliary units?

News from the research project

Toolbox for an Analytical Determination of a Gearbox-Generator-Combination

Authors: Tobias Zeller, Kühnert Marius, Schmitt Michael, Cujic Patrick, Prof. Martin Doppelbauer (all Elektrotechnisches Institut am Karlsruher Institut für Technologie), Dennis Bank (Institute of Mechatronic Systems)

This paper deals with the concept development of a gearbox design for optimum brake energy recovery of a truck trailer with the use of a synchronous reluctance machine. Planetary and or spur gears are selected on the basis of a utility analysis. Based on this, a computer-aided gearbox design tool is developed, which generates an ideal gearbox concept for brake energy recovery on the basis of a motor/generator characteristic and a drive cycle. The optimal gear ratio as well as possible gearbox topologies and gearing are calculated automatically. The possible gearbox topologies are 1- to 3-stage gears consisting of planetary or spur gear stages, and in the case of multi-stage gearboxes, permutations of them. In addition, the configuration of axle drive (one generator with differential) or wheel drive (two generators) can be specified as a starting condition. A joint integration and design process of the gearbox and generator offers many advantages such as compactness, easier handling and faster calculation. An optimization criterion is used to select the appropriate gear unit. As a result, the user receives the optimum gearbox topology, the distribution of the total gear ratio among the stages and the gear geometry, as well as further information on mass, costs, installation space and energy yield. Finally, the gear concept synthesis is validated using analytical equations and commercial gear design software, such as KISSsys and KISSsoft. For this reason, a combination of real driving data determined in VECTO and the analytical calculation of the gearbox generator system is used.

The authors would like to thank the project leader "Deutsches Zentrum für Luft- und Raumfahrt e.V." (DLR) for leading the "RekuTrAx" project (project number 01MV22018) and the "Federal Ministry for Economic Affairs and Climate Action"(BMWK) for funding.


The recuperation axle of the future:

You can find more information about the research project on the content hub 

Learn more

Find out more about BPW now!

BPW Bergische Achsen Kommanditgesellschaft has been developing and producing complete running gear systems for lorry trailers and semi-trailers at its headquarters in Wiehl since 1898. BPW's technologies include axle systems, brake technology, suspension and bearings. Millions of trailer axles and running gear systems made by BPW are in use worldwide.

In the RekuTrAx project, our task is to optimise the respective axle components so that a generator system can be integrated. Our aim is to reduce the number of components and make transport proportionately greener.


Find out more about the electrotechnical institute now!


At the Institute of Electrical Engineering (ETI) of Karlsruhe Institute of Technology (KIT), experts in power electronics, electrical machines, drive control, and energy storage systems conduct research. With about 70 employees, interdisciplinary cooperation of these neighboring research areas takes place in order to improve the increasing requirements in terms of power density, functionality, and energy efficiency and to create innovations.

The focus of the RekuTrAx project is the development of highly efficient and compact drive solutions with synchronous reluctance machines, as well as the dimensioning and control of power converters with intermediate circuits based on the latest generation of power semiconductors.


Find out more about the Institute of Mechatronic Systems now!

The imes deals with the interplay of mechanics, electrical engineering and information processing. This can be found in many industrial areas such as robotics, production technology, medical technology, warehousing. As part of the RekuTrAx project, it is researching a predictive energy management system that allows the dragging operation of the axis to be minimised and at the same time ensures the permanent cooling of the transported goods. Compared to a reactive refrigerated axle, this allows more CO2 to be saved as well as increasing overall cost savings. In addition, imes is working on minimising vibrations that occur within the axis and monitoring the entire system with condition monitoring. In this way, possible damage to the system can be recognised at an early stage and the service life extended.