Observer design typically demands a comprehensive understanding of the system's model, necessitating meticulous parameter tuning for each state. In this paper, we introduce an observer design tailored to a class of linear systems, mitigating the need for extensive tuning and intricate model knowledge. Our proposed observer integrates steady-state behavior estimation with a dynamic state-based estimation, effectively streamlining the design process. To illustrate its effectiveness, we apply this observer design to the control of running gears with inde-pendently rotating and driven wheels within the research project ‘Next Generation Train’. This approach demonstrates a significant reduction in the requisite tuning parameters and model intricacy, offering a more practical and efficient solution for control systems.

Railway running gears with independently rotating wheels (IRW) can significantly improve wear figures, comfort, and safety in railway transportation, but certain measures for wheelset stabilization are required. This is one reason why the application of traditional wheelsets is still common practice in industry. Apart from lateral guidance, the longitudinal control is of crucial importance for railway safety. In the current contribution, an integrated controller for joined lateral and longitudinal control of a high-speed railway running gear with driven IRW is designed. To this end, a novel adhesion-based traction control law is combined with linear time-variant and nonlinear model predictive control (MPC) schemes for lateral guidance. The MPC schemes are able to use tabulated track geometry data and preview information about set points to minimize the lateral displacement error. Co-simulation results with a detailed multi-body simulation show the effectiveness of the approach compared with state-of-the-art techniques in various scenarios, including curving, varying velocities up to 400 km/h and abruptly changing wheel-rail adhesion conditions.

A full-scale prototype of the Next Generation Train (NGT) running gear with a roller rig installation bench will be built as proof of concept of the running gear and its suitability for high-speed traffic.It will be available as the research platform "Forschungsinfrastruktur NGT-Fahrwerk" (FuN) for the German Aerospace Center (DLR) internal and external research activities.This work presents an innovative method and tool chain to develop application software for the automation of a mechatronic running gear (prototype).The methodology, development, and simulation tools that offer a consistent tool chain from model creation to real-time software and measurement data processing are presented.The model and software structures that are necessary for the software environment are described.The software-in-the-loop environment couples the existing multi-body simulations for the development process with signal-based simulation software using a co-simulation interface.The resulting software-in-theloop simulation environment contains a novel interface layer that translates the mechanical states of the multi-body simulation to pseudo-electrical signals that are read or written by the application software.This makes it possible to develop real-time applications and software structures in software-in-the-loop architectures.The real-time software contains a dedicated model structure of input, processing and output submodels, which is based on signal flow and distinct assignment of tasks.On the rapid-control-prototyping hardware, the real-time software is investigated with a virtual installation bench simulation.

The rules and standards that define the requirements and methods for the layout of friction brake systems for railway vehicles still demand extensive experimental surveys since the general confidence in the theoretical predictability of the brake pad friction behaviour is limited. In fact, a review of numerous measurements from dynamometer test rigs exposes a large variation of the friction characteristics. Nevertheless, these measurements could be exploited to develop an elaborate friction modelling approach that includes deterministic and stochastic influences. The comparison of vehicle measurements from field tests with simulation results reveals that a significant improvement of the theoretical predictability of braking distances is within reach. Consequently, this applies as well for a more virtual layout and acceptance procedure for railway vehicle brake systems in the future.

The running gears of DLR’s long-term project Next Generation Train utilize independently rotating wheels with mechatronic track guidance, direct drives close to the wheels and are optimized for low weight. On the basis of encouraging research results so far, DLR decided to design and build a true scale prototype of the NGT running gear and use it as a research facility. It is the intention to improve, validate and demonstrate the mechanical and mechatronic design, sensor and actuator lay-out step by step and finally approach the Technology Readiness Level 6. By the end of 2022, this prototype will be put into operation considering low speed scenarios up to max. 5 m/s at an in-house integration test rig. This is the current task, which is reported on in the paper. However, this work is supposed to prepare advanced performance experiments up to 350 km/h on external roller rigs and at railway test tracks later on.

The “Next Generation Train” (NGT) is a double-deck high speed train concept in light-weight design that has been established as a technical and project framework in which the German Aerospace Center gathers its long-term railway vehicle research. To reduce wheel and rail wear and to enhance the passenger capacity, a mechatronic running gear with independently rotating wheels (IRW) is a key vehicle component under research. This running gear requires an advanced control of the lateral dynamics in order to fully exploit its potential in minimizing wear and noise, but this relies on information on its lateral position relative to the track. In daily railway operation it is difficult to directly measure this displacement of the wheel-pair. However, according to previous work it is possible to design an appropriate observer to estimate the lateral position, but its estimation accuracy highly depends on the chosen sensor configuration. Nevertheless, it was shown that the lateral dynamics of the running were not completely reproduced by the system description especially at suddenly changing directions in the movement of the IRW. In this work the system description is complemented by a nonlinear description of the wheel–rail geometry. Therefore, an observability analysis and an observer synthesis to estimate the lateral position for the nonlinear system of the 1:5 scaled hardware running gear is carried out. For validation purposes an extended Kalman filter with the U-D formalism is implemented at the real-time environment of the testbed and the estimation accuracy of the observer configurations is compared.

Im Rahmen des Next Generation Train (NGT) Projekts entwickelt das Deutsche Zentrum fur Luft- und Raumfahrt e.V. (DLR) das Zugkonzept NGT High Speed Train (HST), ein 400 km/h schneller doppelstockiger Triebwagenzug fur den Hochgeschwindigkeitspersonenverkehr. Ein Teil der Konzeption der NGT HST Mittelwagen ist die Entwicklung eines leichtbauoptimierten, radial einstellbaren, angetriebenen Einzelrad-Einzelfahrwerks. Fur den Aufbau eines ersten Prototypen diese NGT HST Fahrwerks wird eine DLR-Grosinvestition Forschungsinfrastruktur NGT-Fahrwerk (FuN) von mehreren DLR Instituten gemeinsam vorangetrieben. Erster Schritt fur den Aufbau der Strukturen des Fahrwerks ist die Schweisbaugruppe des Radtragers. Die Berechnung, fertigungsgerechte Auslegung und Herstellung dieser Baugruppe ist erfolgt. Die gefertigten und im Rahmen des Artikels beschriebenen Bauteile werden fur Belastungstests und den Zusammenbau in einem Prototypenfahrwerk verwendet.

The development of railway running gears with independently rotating wheels is a focus of research within the Next Generation Train project at DLR. The lateral guidance of this type of running gears represents a challenging problem that relies on active control. The paper introduces results on this research regarding observer and control design that are focused and demonstrated on a scaled experimental running gear hardware that was specifically constructed for this purpose. Additionally, the development of the lateral guidance system is supported by simulation and optimization within a Modelica based virtual simulation environment tailored for the modeling of railway vehicle dynamics in multi-domain engineering tasks.

The proceeding enhancement of sensor technology, data processing and communication opens a broad field to improve the dynamics of railway vehicles by controlled systems targeting e.g. passenger comfort and wear reduction. In terms of an integrated control structure, information of leading bogies can be used for an advanced control of the trailing ones, like it is recently applied in tilting trains. Such an approach has not yet been investigated for the lateral guidance of driven independently rotating wheels (DIRW). To evaluate the potential of a control using preview information, an integrated control structure is introduced in this work. The control is based on the concept of feedback linearization and considers characteristics of track trajectory and irregularity, which are obtained at a leading wheel pair. The control performance is optimized with the help of software-in-the-loop simulations and the results show a significant improvement of the running dynamics.

State observer design turned out to be crucial in several recent railway vehicles projects on active control and condition monitoring at DLR, but may also be useful for emerging technologies like the cyber physical system and the digital twin approach or the realization of predictive maintenance concepts. With this background and motivation the paper presents a process in three steps: (i) an initial analysis results in a physical model, (ii) the subsequent transfer to state space representation facilitates the prove of observability and (iii) the observer synthesis supports the design of the observer feedback law. Results from two projects, one related to longitudinal or traction dynamics, the other associated to the guidance task of independently rotating wheels, demonstrate the application of the observer design process and offers a comparison of observer estimates with measurements.

Das Deutsche Zentrum fur Luft- und Raumfahrt baut im Rahmen des Projektes Next Generation Train einen ersten Prototyp des fur den Hochgeschwindigkeitsverkehr entwickelten, mechatronischen Einzelradfahrwerkes. Bis Ende 2022 wird das Fahrwerk mit einem Integrationsprufstand in Betrieb genommen und anschliesend auf Rollprufstanden und in Versuchsfahrzeugen weiter getestet.

Exploiting several precursor papers on specific railway modeling topics, their models have been collected and reorganized in order to propose a sound modeling framework dedicated to railway dynamics.

The latest extension of the DLR FlexibleBodies Library concerns the field of automotive applications, namely the anti-roll bar.For the particular purposes of NVH and vehicle dynamics, the anti-roll bar module provides two appropriate levels of detail, both being based upon the beam preprocessor.In this paper, the procedure on preparing the models and their application for particular automotive related analyses is presented.

The project Next Generation Train (NGT) is an interdisciplinary approach of researchers from several institutes of the German Aerospace Center (DLR) to face the changing demands for railway vehicles and design a prospective train concept. To reach a travel speed of up to 400 km/h while reducing energy consumption, noise and wear is a challenging high level goal of the project. To achieve this, a novel mechatronic bogie with independently rotating wheels is designed aiming for enhanced running dynamics and continued floors on both levels of the double deck car body. An active guidance guarantees lateral stability and the enhanced running dynamics of this approach are already shown in simulations and on a 1:5 scale roller rig. In order to advance the research process, the running gear will be built up in 1:1 scale for a further verification of the advantages. This true scale prototype will brought into service in several intermediate steps that inter alia include pure virtual simulations, hardware-in-the-loop tests, preliminary hard- and software checks on an auxiliary low-budget test bench until experimental campaigns on external high-fidelity wheelset roller rigs will be launched. With this motivation a multi-physical simulation environment for the virtual commissioning of the 1:1 scale running gear is developed in this work Therefore, elaborate multibody models are established using the Modelica RailwayDynamics Library including the multibody dynamics in combination with mechatronic components and control algorithms. In an exemplary load scenario it is shown, how the performance of the lateral guidance control in case of excitations by lateral rail irregularities may be investigated on available wheelset roller rigs. In addition, the visualization of CAD data in the multibody simulation can be used for a vivid explanation of the running gear concept under realistic conditions. Overall, this work can be embedded in the progress pointing towards virtual homologation and digital twins.

Das Deutsche Zentrum fur Luft- und Raumfahrt (DLR) konzentriert einen grosen Teil der Schienenfahrzeugforschung im Langzeitprojekt Next Generation Train (NGT). Dabei ist das Ziel, einen doppelstockigen Ultra-Hochgeschwindigkeitszug zu konzipieren. Um die Passagierkapazitat zu erhohen und somit den Energieverbrauch pro Kopf zu reduzieren, werden Einzelrad-Einzelachs-Fahrwerke (EEF) vorgesehen. Im Gegensatz zu konventionellen Fahrwerken benotigen EEF bei hohen Geschwindigkeiten eine geregelte Spurfuhrung, um einen sicheren Betrieb zu gewahrleisten. Daruber hinaus ermoglicht die aktive Spurfuhrung eine nahezu ideale radiale Einstellung der Fahrwerke bei Kurvenfahrten, was eine signifikante Reduktion von Verschleis und Gerauschemission impliziert. Das theoretische Potential des Einsatzes der EEF konnte bereits in Mehrkorpersimulationen und einer Optimierungsstudie nachgewiesen werden . Allerdings werden sowohl in den Simulationen als auch am Prufstand alle Zustande direkt uber Sensoren gemessen, was auf offener Strecke weder aus wirtschaftlicher noch aus technischer Sicht moglich ist. Um eine kontrollierte Umgebung fur die Entwicklung der aktiven Spurfuhrung zu schaffen, wurde ein Experimentalfahrwerk (EFW) des NGT-Mittelwagens gebaut . Dieses Fahrwerk ist im Masstab 1:5 nach Ahnlichkeitsgesetzen konstruiert und wird auf einem Rollprufstand uber einen Echtzeitrechner betrieben. Dieser Beitrag zeigt auf, welche Sensorkonfiguration erforderlich ist, um auch im realen Betrieb die lateralen Position y des EFW durch einen nichtlinearen Beobachter schatzen zu konnen. Ein wichtiger Aspekt der Beobachterentwicklung ist die Betrachtung der nichtlinearen Rad/Schiene-Schnittstelle, in der Kontaktgeometrie und Reibcharakteristiken zusammenwirken. Robustheit gegenuber Parameteranderungen im Rad/Schiene-Kontakt ist das Hauptziel der aktiven Spurfuhrung. Unter dieser Voraussetzung wurde ein vorlaufiger Regler fur die Spurfuhrung entwickelt. Fur die aktive Spurfuhrung ist die Kenntnis des lateralen Versatzes des Fahrwerksmittelpunktes relativ zum Gleiskanal essentiell. Aufgrund der hohen Reisegeschwindigkeiten und Gleislagefehlern entstehen hochdynamische Anregungen, welche direkt auf das Fahrwerk wirken. Da unter realen Bedingungen die direkte sensorische Erfassung der Position nicht moglich ist sind im EFW eine Reihe von Sensoren zur indirekten Ermittlung des lateralen Versatzes verbaut. Zur Ermittlung der lateralen Position des Fahrwerks werden drei Sensorkonfigurationen untersucht. Die Messgrosen beinhalten Gierwinkel , Gierrate , Querbeschleunigung und die Winkelgeschwindigkeiten der Rader. Im Fahrwerksrad verbaute Kraft-Momenten-Sensoren messen die Krafte Fz und Fy in vertikaler und lateraler Richtung sowie das Moment Mx um die Langsachse. Das nichtlineare System EFW wird in Abhangigkeit der Sensorkonfigurationen auf Beobachtbarkeit untersucht. Auf Basis dieser Analyse wird ein Erweitertes Kalman-Filter (EKF) zur Schatzung der lateralen Position entworfen. Das EKF eignet sich hier aufgrund seiner Umsetzbarkeit und Echtzeitfahigkeit auf dem Echtzeitrechner. Die Auslegung des EKF erfolgt durch Optimierung in der Simulationsumgebung Dymola. Abschliesend wird die Schatzung der lateralen Position anhand von realen Messdaten am Prufstand validiert und diskutiert.

The paper presents the progress of control development for mechatronic guidance within the DLR-internal project Next Generation Train. It reports on the implementation of the control on the experimental running gear hardware operated at the scale 1: 5 roller rig at DLR. The state feedback control synthesis utilizes the parameter space approach in order to explicitly consider varying conicities. A feed-forward controller is introduced by model inversion. The resulting control performance is demonstrated by measurements. Then, the approach is transferred and applied to a full scale multibody model of the NGT train set. Specific measures are required to account for gyroscopic effects in transition curves, where the superelevation of the track is inor decreasing. Simulation results document the achievements of the control design and validate the underlying considerations.

A main aspiration of the DLR project Next Generation train (NGT) is to include mechatronic systems in railway vehicles, because this opens a broad field to improve the running dynamics. Mechatronic systems enable the use of independently rotating wheels (IRW), which can crucially reduce wear due to the different wheel speeds, but afford an active guidance control to stabilize the lateral movement. However, the control design is challenging due to the complex non-linear system, mainly caused by the non-linear wheel-rail profile. Beyond that the guidance has to be robust to cover various scenarios regarding e.g. different velocities, track irregularities, curving and wear profiles. In this survey, a control design via feed-back linearization is presented, offering the possibility to explicitly address non-linearities in design. In this way, elaborate gain scheduling between linear designs in various operating points can be avoided. To enable the control synthesis an analytical model is established, analyzed and leads to a control structure, based on the feedback of different wheel speeds. Therefore, the advantage of IRW, allowing for low creepage and wear in every lateral position of the wheel pair is beneficially utilized. The control is implemented in Modelica, because it allows for automatically inverting models and using them conveniently in the control layout. In addition the gains of the established controller are adjusted in terms of stability and performance using multibody models of the DLR Railway Dynamics Library. The control is then transferred to a Simpack full scale multibody model via FMI and the performance is increased by control parameter optimization. Preliminary simulation results for a coach running on tracks with irregularities depict that a sufficient performance of the controller and a significant wear reduction compared to a conventional high speed train is attained. Beyond that, the usage of advanced inverse models in the control layout facilitates further refinement and the controller is to be tested on the 1:5 scaled roller rig.

Noise for continuous-time system simulation is relevant for many applications, where time-domain results are required.Simulating such noise raises the need to consistently shape the frequency content of the signal.However, the methods for this task are not obvious and often form filters are approximated by state space implementations.In this paper, we address the problem with a new method relying on directly using the specified power spectral density for a convolution filter.For the example of railway track irregularities, we explain how to derive the required filters, implement them in the open-source Noise library, and verify the results.The new method produces correct results, is very simple to use, and enables new features for time simulation of physical systems.

High crosswinds affect the stability of railway vehicles, in particular if they run on very high speed to reduce traveling time, if they are configured as double-deck cars to increase the number of passenger seats and if they use lightweight design in order to reduce life-cycle costs.This is why crosswind stability is an active field of research within the project Next Generation Train.However, this field relies on the cooperation of two different domains, namely aerodynamics and vehicle dynamics.With this background a crosswind stability tool was implemented in Modelica as a part of the DLR RailwayDynamics Library.This tool gathers data from scaled wind tunnel measurements and multibody data on the railway vehicle in order to rapidly analyze and assess the risk of overturning due to high crosswinds.To a large extent the tool is oriented towards the associated homologation rules and standards.However, the tool is as well supposed to support future advancements of these standards by providing capabilities for the stochastic analysis of the crosswind stability problem.