Search

The temperature of axle box bearing is always one of the indicators used to monitor whether the high-speed train is running safely. In this paper, a thermal model of axle box bearing considering the change of bearing lubrication state and the operating condition of the high-speed train was established. Based on the analysis of the generation mechanism of frictional heat inside the bearing, the influence of proportion of grease involved in lubrication was introduced for the first time and a detailed temperature transfer system of the axle box system was established. At the same time, through the axle box bearing-vehicle system dynamics model, the vertical and lateral loads of the axle box bearing under different operating condition were obtained as input parameters of the axle box bearing thermal model, the temperature distribution curve of the bearing under different operating conditions was obtained. Finally, based on the long-term wireless transmission device system (WTDS) temperature monitoring data, the calculation results of the established model were verified. The verification results showed the reliability of the model established in this paper, and showed the necessity of considering the change of the internal lubrication state of the bearing when evaluating the axle box bearing temperature. [ABSTRACT FROM AUTHOR]

The vibration of high-speed trains induced by track irregularities is a main factor affecting ride comfort. Especially, the long-wavelength track irregularities can reduce the passengers' ride comfort by increasing the vibration of the high-speed trains. A three-dimensional human body model coupled to a vehicle body and tracks is established to form a coupled human-seat-vehicle-track system for investigating the influence of the long-wavelength track irregularities on ride comfort. The parameters of the seated human model are determined by measurement based on the multi-island GA method. The coupled model is then used to evaluate the ride comfort of high-speed trains using ISO 2631 under the excitation of the track longitudinal level irregularities. The effects of primary, secondary suspension, and seat support vertical stiffness and damping on ride comfort are analysed. The results show that the track's longitudinal irregularities lead to high human body vibration levels and large ride comfort indices (lower ride comfort), especially when the irregularity excitation frequency is near the natural frequency of the high-speed train. The passengers' ride comfort is more sensitive to the vertical secondary suspension stiffness than the other suspension parameters. [ABSTRACT FROM AUTHOR]

Research and development of innovative suspension components for rail vehicles have involved huge investments in recent years. Research efforts have focussed on designing and optimising suspension systems to deal with the new challenges introduced in railway dynamics by the continuous increase in vehicle speed. In particular, yaw dampers have been a relevant research topic due to their influence on vehicle stability. In this context, this paper aims to propose a Hardware-In-the-Loop (HIL) methodology for testing yaw dampers under experimental conditions close to real operating scenarios, comparing the influence of different prototypes on the stability of high-speed rail vehicles. A reduced vehicle model is proposed for real-time integration in HIL tests. This model provides a reference stroke to be imposed on the prototype tested, considering the actual damping force provided by the device being analysed. Two yaw damper prototypes are introduced to validate the proposed methodology by means of comparative analysis at different vehicle speeds. The experimental results provided by the HIL test bench are then compared with corresponding analysis done using Multi-Body (MB) simulations. The proposed HIL methodology has proved to be able to test physical prototypes and define guidelines to assist damper manufacturers developing and optimising yaw damper components. [ABSTRACT FROM AUTHOR]

Semi-active primary suspensions are an effective means of improving ride quality in high-speed railway vehicles in relation to the mitigation of car-body bending vibration. In this paper, prototype magnetorheological (MR) dampers are tested and the results are used to define a mathematical model of the dampers. Then, three control schemes for semi-active primary suspensions are proposed: Skyhook, LQG and Mix-1-Sensor, and their performance is assessed by means of Hardware-In-the-Loop (HIL) tests considering a simple quarter-vehicle model which is run on a real-time board and set in interaction with one physical MR damper. The results show that all three considered control strategies lead to a reduction of car-body vibration by around 30% and a very good agreement is found between HIL tests and numerical simulations in which the physical damper is replaced by the mathematical damper model. The damper model is finally interfaced with a flexible multi-body model of the complete vehicle to provide further assessment of semi-active control. The results of the latter simulations show that the semi-active suspension could provide an improvement of the $ {N_{mvz}} $ N mvz ride quality index in the order of 40–45% with respect to the passive vehicle for all three control schemes. [ABSTRACT FROM AUTHOR]

To enhance the lateral stability of a certain type of high-speed train under bogie's active control, characteristics of inertial actuators that generate control force in the active control system are studied, the control delay of the whole Hardware-in-the-Loop (HIL) system is measured, and multi-objective optimisation for feedback parameters with or without the control delay is achieved in this study. A linear model of bogie lateral dynamics, with two inertial actuators, acting on the front and rear end beams, is established for the optimisation. Correspondingly, a nonlinear vehicle model is established in the Simpack platform for both mathematical simulation and HIL simulation to verify the control effects. As the force source of active control, dynamic characteristics of the inertial actuator with different control strategies are examined. Multi-objective optimal control is carried out on the linear active bogie models with and without the delay measured in the experiment to improve the bogie hunting stability. The control method is then evaluated in a nonlinear vehicle model and HIL simulation. Simulation results show that the lateral dynamic performance of the high-speed train can be effectively improved with the active stability system even with a large time delay. [ABSTRACT FROM AUTHOR]

Semi-active suspensions are seen as a promising technology to improve ride quality in high-speed railway vehicles as they provide substantial benefits not achievable through an optimisation of the passive suspension while avoiding some drawbacks of full-active control. Previous works showed that semi-active primary suspensions (SAPS) offer significant improvement of ride quality. However, published implementations of this concept did not consider the coupling effects between car-body and bogie vibrations, which play a decisive role in the success of control strategies for SAPS. This paper provides a comprehensive analysis of SAPS to improve vehicle ride comfort, with special attention to the mitigation of car-body bending vibration. A vehicle model considering the coupling of car-body bending and bogie pitch is proposed and used for the synthesis of an LQG controller. The performance of the semi-active suspension and controller is assessed using a detailed flexible multibody system of a high-speed vehicle. The proposed control scheme is shown to be highly effective in reducing car-body vibration in the entire frequency range of interest from 1 Hz to20Hz. A remarkable ride comfort improvement is found in the entire speed range from 150 km/h to 350 km/h. [ABSTRACT FROM AUTHOR]

This investigation integrates an alternative fully-parameterized approximation of nonlinear wheel/rail interaction into a simplified vehicle model, and a two-parameter Hopf bifurcation analysis is conducted to reveal the influence of the wheel/rail contact geometry and secondary suspension parameters for high-speed rail vehicles. The bifurcation diagram is compared among the 6 DOFs bogie model, linear and nonlinear 7 DOFs vehicle model, nonlinear 17 DOFs vehicle model, and 3D full DOFs vehicle model. It shows that the nonlinear 7 DOFs vehicle model can meet the requirement of both carbody hunting and bogie hunting simulations. 6 DOFs bogie model can only be used in bogie hunting bifurcation analysis. Linear vehicle model would bring errors in either critical speed or limit circle magnitude. The divergences in the linear terms of rolling radius and contact angle polynomials are significant enough in field operation to cause a noticeable difference in Hopf bifurcation speed. Attention shall be paid to the shape of equivalent conicity and contact angle curve. The crucial parameters to the Hopf bifurcation include the series stiffness and damping coefficient of the yaw damper and the lateral damper damping. However, the requirement of suspension parameters for stability can conflict in carbody hunting and bogie hunting cases. [ABSTRACT FROM AUTHOR]

The superconducting electrodynamic suspension (EDS) train, which has reached a manned speed of 603 km/h in 2015, and is therefore regarded as one of the most attractive technologies for the higher speed train. In the superconducting EDS train, the discrete layout of ground null-flux coils causes the additional electromagnetic ripples towards the bogies, making the vibration control more essential to ensure the running performance. In this work, a fourteen-degree-of-freedom dynamics model of superconducting EDS train, was established to explore the effective strategy for vibration reduction. This model uses the time domain wave of track irregularity spectrum as the input of vehicle system. MATLAB/Simulink and "Zhai's method" are both adopted to solve the vehicle dynamic model and validate the model. Using these models, the effectiveness of the proportional force and maximum force for the primary suspension was examined. The results show that the maximum force strategy has advantage over the proportional force strategy in terms of energy consumption and vibration sensitiveness. However, the electromagnetic damping control can only suppress the vibration of bogie. To achieve an overall vibration control, the "ON-OFF" sky-hook damping was further introduced to the secondary suspension to suppress the vibration of car body. We find that, the control effect is preferable with the damping value being between 5 kN·s/m and 10 kN·s/m. Therefore, the cooperative control, considering both the primary and secondary suspensions, is necessary to meet the Urban Tracked Aircushion Vehicle Standard and provide theoretical supports for the suspension design of superconducting EDS train. [ABSTRACT FROM AUTHOR]

Due to local resonances, high vibration levels occur frequently in high-speed train floor, which impact on the ride comfort negatively. A method to control excessive local vibration with multiple dynamic vibration absorbers (DVAs) is presented. Firstly, possible causes of the high vibration levels are investigated with operational and modal tests. Then a model of the vehicle body with multiple DVAs is established based on the modal superposition method. It is found that a strong peak at the low frequency is dominated by a single mode, which can be attenuated with under-frame equipment as a single DVA. In the frequency region between 30 and 35 Hz several local modes contribute, and are controlled with multiple DVAs. Methods are studied to determine the optimal parameters for these DVAs, including location, natural frequency and mass. For a single DVA conventional fixed-point theory is used, whereas for multiple absorbers an optimization method is proposed. Finally, the effect of the optimization is verified in a full vehicle model with frequency responses analysis. The results indicate that the proposed method can reduce the vibration of targeted modes and improve the ride quality considerably in terms of the vertical motion. [ABSTRACT FROM AUTHOR]

The aim of this work is to introduce a new concept for a hydraulic semi-active yaw damper (SAYD) for the improvement of the stability of a high-speed rail vehicle. This concept represents a further elaboration of Secondary Yaw Control but envisages the use of semi-active hydraulic dampers instead of full-active electromechanical dampers, simplifying the design of the system and facilitating the design of a safe and fault tolerant device. Two control algorithms are proposed for the semi-active damper: maximum power point tracking and skyhook with Karnopp approximation. A multi-physics model of the SAYD is introduced and used in co-simulation with a multi-body model of a high-speed vehicle. Using these models, numerical simulations are performed to assess the behaviour of the semi-active damper in terms of improving the running stability of the rail vehicle at very high speed, showing that the use of the SAYD in combination with any of the two control strategies considered allows to improve substantially the stability of the vehicle. The results of experimental investigations performed in the project will be reported in a companion paper. [ABSTRACT FROM AUTHOR]

This paper modelled the vehicles in conventional Longitudinal Train Dynamics (LTD) as 2D models that considers suspensions and wheel-rail contact. The Polach model was used as the adhesion model for faster computing speeds. A 2D train model was developed and solved using a parallel computing technique called Message Passing Interface. A train with the configuration of 1 locomotive + 120 wagons + 1 locomotive + 120 wagons was simulated in three different braking scenarios: emergency brake, full-service brake and minimum service brake. The same simulations were also conducted using a LTD model and the results are compared with those of the 2D train model. The comparisons indicate that: (1) wheelset rotational inertia needs to be considered in LTD models to achieve matched results with the 2D train model; (2) in most cases, simulated coupler forces from the 2D train model are slightly lower than those from the LTD model; (3) during minimum service brake and full-service brake, the differences of simulated coupler forces between the two models are lower than 100 kN; and (4) during emergency brake, a maximum difference of 266 kN was simulated, which accounts for 35% of the maximum force simulated by the LTD model. [ABSTRACT FROM AUTHOR]

Abstract: The dynamics of a new concept of a high-speed cable car developed for fast urban transport have been analysed and improved via active control. A mathematical model, which takes into account all the mechanical complexities of a coupled cable-vehicle dynamic system, has been built. From the complete FE cable model, a simpler model has been derived to be used with the vehicle model in the design of control strategies of the active suspension. In order to validate the results experimentally, a reduced scale quarter vehicle test rig has been built simulating the real time cable behaviour by means of a stiffness controlled hydraulic actuator [ABSTRACT FROM AUTHOR]

An existing state—space based numerical method (see Reference [1]) to simulate vertical dynamic interaction between a rolling train and a railway track has been improved and extended. The modified method allows for non—linear track model properties and flexible vehicle model components. Track model properties are separated into linear contributions corresponding to a non—loaded track configuration and increments which are state—dependent. Linear finite element models represent the train and the track modelled as separate components. Model reduction techniques are employed for computational efficiency. State—dependent track model properties tire accounted for by applying counter—acting state—dependent forces to the corresponding nodes of the linear track model. The train/track simulations are carried out in the time—domain. The need for a state—dependent track model is discussed with respect to laboratory and field measurements. [ABSTRACT FROM AUTHOR]