A novel mechatronic running gear: concept, simulation and scaled roller rig testing

The basic idea of the concept of the novel mechatronic running gear consists of independently rotating wheels with a mechatronic guidance system to overcome the disadvantages which conventional wheelsets show under certain operating conditions. Especially in narrow curves or at very high speed, oscillation problems linked with noise and increased wear can be observed at conventional wheelsets (curve squeal, hunting instability). Otherwise, vehicles with independently rotating wheels often need a higher maintenance effort to ensure low wear at the wheels. The aim of the concept is the development of a running gear which offers a better running performance than a conventional running gear under all operation conditions in combination with a low maintenance effort. This means a lower emission level of vibrations to the ground and the air as well as less friction at curves and therefore a lower need for traction energy. Additionally, the running gear concept enables more comfortable train concepts such as low floor trams or double deck trains with two continuous decks, because of the abdication of the wheelset axle. The principle is applicable to bogies as well as running gears with a single pair of wheels. These ambitious aims require high demands of the sensor and control system. For instance, the sensor must be able to identify the position of the wheels relative to the track and the control system must be fast enough to avoid flange contact even at highly disturbed tracks at high speed. In the first step a scaled 1:5 roller rig is build (picture) and a model of the scaled roller rig is set up as Multi-Body-System (MBS). In the roller rig force-torque-sensors are used as position sensors. The model can be validated by measurements at the test rig. Then the validated model is used for the design process of the control-algorithms which are tested in the roller rig. Only a model-based control system is able to meet the high demands under the different operation conditions of a train. In a second step the developed control algorithms are transferred into a MBS-model of a 1:1 vehicle to demonstrate the functional capability and the advantages of the simulated operation conditions. Currently this work has the function of a demonstrator and to identify the further research emphasis for an implementation in a real vehicle concept. At the end this novel mechatronic running gear will increase the competitiveness and acceptance of the railway by a cost-effective and low emission running gear. This work is integrated in the DLR-Project Next Generation Train

Running dynamics concept with mechatronic guidance

The two-axle intermediate waggons of DLR's Next Generation Train (NGT) have single-axle running gears with independently rotating wheels (IRW) and mechatronic track-guidance. This enables centring in the track and active radial steering for IRW pairs during curve passing. The wheel wear and noise generation can thus be considerably reduced. Multibody simulations are used to verify and optimise the dynamic behaviour. Moreover, detailed approaches for simulating high-frequency wheel-rail dynamics are being introduced in the project

Next Generation Train - Bericht zu den Simulationsrechnungen 2010 (Fahrzeug Systemdynamik)

In diesem Bericht wird der aktuelle Stand der Fahrdynamikauslegung des Next Generation Trains zusammengetragen. Die Auslegung erfolgt mittels Mehr-Körper-System-(MKS)-Simulationen in der Software SIMPACK. Für prinzipielle Vorüberlegungen werden vereinfachte Modelle verelendet. Die Untersuchung der Fahrzeug-Systemdynamik erfolgt an einem Zugmodell bestehend aus vier Mittel- und zwei Endwagen. Ein Ziel dieses Berichts besteht darin, nach zu weisen, dass es mit dem Zugkonzept möglich ist, die im Projektplan vorgegebenen Verschleiß und Komfortziele zu erreichen. Als Ergebnis kann festgestellt werden dass dies prinzipiell – mit entsprechendem Aufwand – möglich ist. Darüber hinaus werden verschiedene Erkenntnisse gewonnen, die für andere Teilprojekte im NGT relevant sind

High-speed rail vehicles: State of the art and further developments

Worldwide a lot of high speed railways are successfully operating. Until the 1970s, the market share of the European railways in passenger transport decreased strongly due to the fierce competition of individual motor car traffic and of civil aeronautics. The development of high-speed trains and the construction of new high-speed lines, which started in Europe at the end of the 1960s, helped the railway companies a lot to regain lost market shares based on the developments in Japan, France, Italy and Germany. Currently, high-speed trains provide a short and comfortable travelling at maximum operating speeds up to 380 km/h: New lines are planned or built in many countries. Major developing goals for future high speed trains are focused on higher acceptance by offering higher travelling speeds, improved passenger comfort and a high level of safety as well as on better economic efficiency by a reduced energy consumption per seat and lower life cycle costs. The challenge is especially the goal conflict between the increasing of the speed and the reduction of the energy consumption, because the air resistance is proportional to the square of the speed. For instance, the German ICE 3 high-speed train needs a traction power of 7500 kW for travelling with constant speed of 330 km/h on an even and straight track. More than 90% of this power is needed for negotiation of the air resistance. Therefore the optimisation of the aerodynamic design is one of the key issues for an environment friendly train. The internal DLR research project “Next Generation Train“ (NGT) represents a lot of innovative developments. Nine DLR institutes are engaged in different rail specific topics such as aerodynamics, structural design, energy systems, new materials, passenger comfort, running dynamics and vehicle concepts. The most important target of this project is an energy reduction per seat of 50 % compared to the ICE 3. However, the potential of energy reduction by aerodynamic optimisation is not sufficient for this target. Therefore, the concept of the NGT consists of a high speed double-deck trainset in order to obtain a higher increasing of the capacity (i.e. number of seats) than of the air resistance. The passenger comfort of a double-deck train can be significantly increased by continuous floors on both levels. However, the arrangement of two decks for passengers above a conventional running gear would exceed the admissible height given by the European loading gauge. Therefore, the operation of such a train is impossible in Europe. This requires a novel concept for the running gears to avoid this problem. The axle shaft connecting both wheels of a conventional wheelset is an essential element which enables a passive control system for the running dynamics. Since the wheels need a certain minimum diameter of about 1 m, the space for the axle is no longer available in a double-deck train with continuous floors. Therefore, the mechanical component of the axle is replaced by a mechatronic system. In addition, this mechatronic system offers further benefits by improving the running dynamics and the wear behaviour of the running gears. This example demonstrates how an innovative running gear concept can contribute to an integrated and environment friendly train concept

Considerations on Active Control of Crosswind Stability of Railway Vehicles

The DLR research project Next Generation Train deals with concepts, methods and technologies for a very high-speed train in double deck configuration and light-weight design. Due to these three key features crosswind stability is a particular subject of study. It is shown that conventional approaches here fall short of guaranteeing safety in high-wind occurrences according to the given homologation standards. Therefore this paper discusses the feasibility of different approaches to ensure crosswind stability by means of active control. Four different concepts are overviewed, the most promising one is then chosen und examined in detailed multibody simulations that are based on data from wind tunnel measurements of the Next Generation Train

Combined friction induced oscillations of wheelset and track during the curving of metros and their influence on corrugation

Curving of rail vehicles is often connected with vibrations, which can be caused by rail corrugation or friction induced oscillation in the wheel/rail-contact. This paper deals with heavy vibrations at the running gear of a metro vehicle with a typical frequency of 80 Hz on curves with a radius between 50 and 200 m. Specific characteristics of the vibrations are the occurrence by passing over rails without an initial corrugation and the disappearance if the rails are wet. In the curves of the concerned network, corrugation can also be found with a corresponding wavelength on the outer rails, but the inner rails show shorter wavelengths. For a better understanding of the originating process a simulation model is set up using the commercial Multi-Body-Simulation-Software SIMPACK. The model includes the vehicle and the track. After an identification of the undetermined parameters the model shows the same behaviour as the real system. The vibration is characterized by large amplitudes of the normal force in the wheel/rail-contact. The originating mechanism and the determining parameters of the oscillation are identified. Using a simple wear law the possibility of rail corrugation originated by these vibrations can be shown with different wavelengths on the inner and outer rail as observed in the measurements