Railway Systems

The application of methods and tools from aerospace and robotics to railway vehicles has a tradition of more than 25 years at the institute and has even reached the industrial level in the meantime. In fact the virtual design of today’s high-speed-trains such as the ICE relies on the multibody simulation environment Simpack, that has originally been developed at the institute and nowa­days represents the technological and eco­nomical basis of the spin-off company Intec.

The present-day research activities in railway vehicles are focussed on 2 areas, namely on vehicle dynamics and on energy systems, and are embedded in the DLR-Project “Next Generation Train” (NGT), see figure below. These 2 topics are key technologies that are interrelated to many other disciplines of cooperating DLR institutes, e.g. as follows:

• Economic efficiency likewise concerns aerodynamic resistance, drive train and auxiliary energy management and main­tenance costs due to wheel/rail wear.
• Aerodynamics and running safety are 2 related topics of the crosswind stability prob­lem.
• Lightweight construction is a key to energy efficient design but has to takethe dynamic loads from vehicle dynamics into account.

An impor­tant part of the current work deals with improvements of the dy­namic simulation methodologies in order to prepare ready-to-use technologies for a target-oriented vehi­cle design and is designated to the specific topics Wheel/Rail Interface, Acoustics, Wear and Crosswind Stability.

Another pillar of the activities is a novel concept of a mechatronic running gear that will be quali­fied at our scaled M 1:5 roller rig.

Last but not least, we are transferring and applying methods from aeronautics that are based on the modelling language Modelica and are capable to model and design multi-domain energy systems in railway vehicles.

DLR-Project Next Generation Train: side view of the high-speed multiple unit vehicle concept: double deck, high-speed-low-floor running gear with single wheel pairs, two axle configuration at the train head, single axle configuration at the intermediate coaches, an optimized aerodynamics, lightweight design.

Wheel/Rail Interface The wheel-rail contact is the essential element of a railway vehicle. The processes in the contact strongly depend on the relative motions of the wheel rim and the rail head. These motions are influenced also by the deformations of the wheelset and the rail, in addition to the displacements of the entire wheelset. Therefore, the structural dynamics of the wheelset and the rail have to be taken into account. In return, an accurate modelling of the structural dynamics requires a refined modelling of the contact, since these forces are responsible for the excitation of the structural dynamics. A refined modelling of the wheelset, of the rail and of the wheel-rail contact is an essential basis for further investigations, dealing e.g. with wear or noise. Mehr

Acoustics A key environmental concern of modern railway transportation systems is the noise disturbance induced by the driving vehicles on the areas surrounding the track. The first step for its prevention is the development of efficient analysis and prediction tools. In particular, the rolling noise (noise radiated by the wheels and the rails), which is the main source in the middle driving velocity range, is addressed. Mehr

Wear In a railway system the wear on rails and wheels causes high maintenance costs. In addition non uniform wear in longitudinal direction such as as rail corrugation or wheel polygons may lead to undesirable vibrations and noise. Therefore, we are developing accurate wear prediction methods, which will essentially support the design of new low-wear railway vehicles. Mehr

Crosswind Stability The term crosswind stability denotes the driving safety of railway vehicles under very strong crosswinds, for example during gales. Because of the increasing driving velocities and the lightweight construction techniques of modern trains, this problem has advanced in the last year to a key issue for the development and the homologation of new vehicles. It follows that the availability of computational methods and tools for an exact prediction of the vehicle behaviour under such extreme conditions is essential. Mehr

Thermoelastic Brake Models The incorporation of multibody simulation tools is now a days one of the most efficient techniques in order to find and solve problems for the railway industry in direction braking systems. The ongoing project has the aim to develop a brake model able to consider not only the mechanical but also the thermal effects during the braking process of high-speed trains. Mehr

Mechatronics The introduction of active systems in railway running gears leads to a new field with many interesting challenges. Our department is developing a bogie with driven independently rotating wheels (DIRW) using practical sensors for feedback control, that reduces wear and roll noise and increases ride comfort. Mehr

Energy Systems The reduction of energy consumption and CO2-emmission will attract more and more attention in the future. Both the design of vehicle concepts and the management of the on-board energy systems in operation rely on an appropriate modelling environment. The multi-physical simulation language Modelica is tailored for these applications. Mehr