Railway Vehicle Model Research Articles

Parameter identification of multi-body railway vehicle models – Application of the adjoint state approach

For the calibration of multi-body models of railway vehicles, the identification of the model parameters from on-track measurement is required. This involves the solution of an inverse problem by minimising the misfit function which describes the distance between model and measurement using optimisation methods. The application of gradient-based optimisation methods is advantageous but necessitates an efficient approach for the computation of the gradients considering the large number of model parameters and the costly evaluation of the forward model.This work shows that the application of the adjoint state approach to the nonlinear vehicle–track multi-body system is suitable, reducing on the one hand the computational cost and increasing on the other hand the precision of the gradients. Gradients from the adjoint state method are computed for vehicle models and validated taking into account measurement noise.

Wear/comfort Pareto optimisation of bogie suspension

ABSTRACTPareto optimisation of bogie suspension components is considered for a 50 degrees of freedom railway vehicle model to reduce wheel/rail contact wear and improve passenger ride comfort. Several operational scenarios including tracks with different curve radii ranging from very small radii up to straight tracks are considered for the analysis. In each case, the maximum admissible speed is applied to the vehicle. Design parameters are categorised into two levels and the wear/comfort Pareto optimisation is accordingly accomplished in a multistep manner to improve the computational efficiency. The genetic algorithm (GA) is employed to perform the multi-objective optimisation. Two suspension system configurations are considered, a symmetric and an asymmetric in which the primary or secondary suspension elements on the right- and left-hand sides of the vehicle are not the same. It is shown that the vehicle performance on curves can be significantly improved using the asymmetric suspension configuration. The Pareto-optimised values of the design parameters achieved here guarantee wear reduction and comfort improvement for railway vehicles and can also be utilised in developing the reference vehicle models for design of bogie active suspension systems.

Evaluation of coupled finite element/meshfree method for a robust full-scale crashworthiness simulation of railway vehicles

The crashworthiness of a railway vehicle relates to its passive safety performance. Due to mesh distortion and difficulty in controlling the hourglass energy, conventional finite element methods face great challenges in crashworthiness simulation of large-scale complex railway vehicle models. Meshfree methods such as element-free Galerkin method offer an alternative approach to overcome those limitations but have proved time-consuming. In this article, a coupled finite element/meshfree method is proposed to study the crashworthiness of railway vehicles. A representative scenario, in which the leading vehicle of a high-speed train impacts to a rigid wall, is simulated with the coupled finite element/element-free Galerkin method in LS-DYNA. We have compared the conventional finite element method and the coupled finite element/element-free Galerkin method with the simulation results of different levels of discretization. Our work showed that coupled finite element/element-free Galerkin method is a suitable alternative of finite element method to handle the nonlinear deformation in full-size railway vehicle crashworthiness simulation. The coupled method can reduce the hourglass energy in finite element simulation, to produce robust simulation.

Vibration control of a semi-active railway vehicle suspension with magneto-rheological dampers

This article presents vibration control performances of a semi-active railway vehicle suspension system using a magneto-rheological damper tested on the roller rig. In order to evaluate control performances, a mathematical railway vehicle model with 15 degrees of freedom is first derived to represent the lateral, yaw and roll motions of the car body, bogie frame, and wheel set, respectively. Based on the formulated model, the design parameters of magneto-rheological damper are determined to undertake a compatible comparison with dynamic performances of conventional (existing) passive railway vehicle suspension system. The designed magneto-rheological damper is manufactured and its field-dependent damping force characteristics are experimentally evaluated. Subsequently, in order to enhance the ride quality of a railway vehicle suspension equipped with magneto-rheological damper, a skyhook controller associated with an extended Kalman filter is designed in a state space representation. The railway suspension system incorporated with the car body and two bogies is then experimentally set up on the roller rig in order to evaluate the ride quality. It is demonstrated from experimental realization of the controller that the ride quality of the suspension system with magneto-rheological damper can be significantly enhanced compared with the existing passive suspension system.

Global sensitivity analysis of bogie dynamics with respect to suspension components

The effects of bogie primary and secondary suspension stiffness and damping components on the dynamics behavior of a high speed train are scrutinized based on the multiplicative dimensional reduction method (M-DRM). A one-car railway vehicle model is chosen for the analysis at two levels of the bogie suspension system: symmetric and asymmetric configurations. Several operational scenarios including straight and circular curved tracks are considered, and measurement data are used as the track irregularities in different directions. Ride comfort, safety, and wear objective functions are specified to evaluate the vehicle’s dynamics performance on the prescribed operational scenarios. In order to have an appropriate cut center for the sensitivity analysis, the genetic algorithm optimization routine is employed to optimize the primary and secondary suspension components in terms of wear and comfort, respectively. The global sensitivity indices are introduced and the Gaussian quadrature integrals are employed to evaluate the simplified sensitivity indices correlated to the objective functions. In each scenario, the most influential suspension components on bogie dynamics are recognized and a thorough analysis of the results is given. The outcomes of the current research provide informative data that can be beneficial in design and optimization of passive and active suspension components for high speed train bogies.

Flexible vibration analysis for car body of high-speed EMU

The resonance of the flexible vibration of car body, which has not been detected before on a passenger coach, occurred recently on a high-speed Electric multi units (EMU) when the train was running at 300 km/h on Beijing-Shanghai line. In this investigation, the force transmission from track to car body via suspensions is elaborated first with possibly induced factors briefly discussed. Both the measurements and experiments in field and in laboratory were conducted to evaluate the resonances and the excitation as well as transmission. Moreover, a three-dimensional railroad vehicle model was built in a computational non-linear Multibody system (MBS) framework, in which the car body flexibility was modeled using Finite element (FE) method. The model was validated and shows good agreements with measurements. Furthermore, the measured wheel and rail profiles were used to analyze the wheel/rail interaction for both new and worn states. The effects of the wheel-rail contact conditions on stabilities, dynamics and riding comforts were also examined. Feasible solutions were promoted to avoid the resonance and following by validating tests. It shows that the high frequency excitation arises from the hunting motion of bogie that closes to the modals of the car body, leads to the resonance of the structure of the car.

Multiobjective optimisation of bogie suspension to boost speed on curves

To improve safety and maximum admissible speed on different operational scenarios, multiobjective optimisation of bogie suspension components of a one-car railway vehicle model is considered. The vehicle model has 50 degrees of freedom and is developed in multibody dynamics software SIMPACK. Track shift force, running stability, and risk of derailment are selected as safety objective functions. The improved maximum admissible speeds of the vehicle on curves are determined based on the track plane accelerations up to 1.5 m/s2. To attenuate the number of design parameters for optimisation and improve the computational efficiency, a global sensitivity analysis is accomplished using the multiplicative dimensional reduction method (M-DRM). A multistep optimisation routine based on genetic algorithm (GA) and MATLAB/SIMPACK co-simulation is executed at three levels. The bogie conventional secondary and primary suspension components are chosen as the design parameters in the first two steps, respectively. In the last step semi-active suspension is in focus. The input electrical current to magnetorheological yaw dampers is optimised to guarantee an appropriate safety level. Semi-active controllers are also applied and the respective effects on bogie dynamics are explored. The safety Pareto optimised results are compared with those associated with in-service values. The global sensitivity analysis and multistep approach significantly reduced the number of design parameters and improved the computational efficiency of the optimisation. Furthermore, using the optimised values of design parameters give the possibility to run the vehicle up to 13% faster on curves while a satisfactory safety level is guaranteed. The results obtained can be used in Pareto optimisation and active bogie suspension design problems.

A new semi-active safety control strategy for high-speed railway vehicles

This paper focuses on the safety of railway vehicles. A new semi-active control strategy is proposed based on the skyhook control theory. In view of the main railway vehicle safety performance indicators, the new control strategy aims at reducing the derailment coefficient of railway vehicles by restraining the lateral vibrations of the bogie and the wheelset. Furthermore, to evaluate the improvement of the safety performance brought about by the new control strategy, a complete railway vehicle model is established using the ADAMS/Rail software package. In further co-simulations, five conventional control methods are compared with the proposed approach under the same conditions. Co-simulation results indicate that the new control strategy is effective in improving the safety performance of railway vehicles.

Development of a new time domain-based algorithm for train detection and axle counting

This paper presents an innovative train detection algorithm, able to perform the train localisation and, at the same time, to estimate its speed, the crossing times on a fixed point of the track and the axle number. The proposed solution uses the same approach to evaluate all these quantities, starting from the knowledge of generic track inputs directly measured on the track (for example, the vertical forces on the sleepers, the rail deformation and the rail stress). More particularly, all the inputs are processed through cross-correlation operations to extract the required information in terms of speed, crossing time instants and axle counter. This approach has the advantage to be simple and less invasive than the standard ones (it requires less equipment) and represents a more reliable and robust solution against numerical noise because it exploits the whole shape of the input signal and not only the peak values. A suitable and accurate multibody model of railway vehicle and flexible track has also been developed by the authors to test the algorithm when experimental data are not available and in general, under any operating conditions (fundamental to verify the algorithm accuracy and robustness). The railway vehicle chosen as benchmark is the Manchester Wagon, modelled in the Adams VI-Rail environment. The physical model of the flexible track has been implemented in the Matlab and Comsol Multiphysics environments. A simulation campaign has been performed to verify the performance and the robustness of the proposed algorithm, and the results are quite promising. The research has been carried out in cooperation with Ansaldo STS and ECM Spa.

An approach for the validation of railway vehicle models based on on-track measurements

This paper proposes an approach for the validation of railway vehicle models based on on-track measurements. The validation of simulation models has gained importance with the introduction of new applications of multi-body simulation in railway vehicle dynamics as the assessment of track geometry defects, the investigation of derailments and the analysis of gauging. These applications are not only interested in qualitative predictions of the vehicle behaviour but also in precise quantitative results of the safety and comfort relevant vehicle responses. The validation process aims at guaranteeing that the simulation model represents the dynamic behaviour of the real vehicle with a sufficient good precision. A misfit function is defined which quantifies the distance between the simulated and the measured vehicle response allowing to evaluate different models at different running conditions. The obtained modelling errors are compared to the measurement uncertainty estimated for one vehicle using repeatability analysis.

Efficient and robust implementation of the TLISMNI method

The dynamics of large scale and complex multibody systems (MBS) that include flexible bodies and contact/impact pairs is governed by stiff equations. Because explicit integration methods can be inefficient and often fail in the case of stiff problems, the use of implicit numerical integration methods is recommended in this case. This paper presents a new and efficient implementation of the two-loop implicit sparse matrix numerical integration (TLISMNI) method proposed for the solution of constrained rigid and flexible MBS differential and algebraic equations. The TLISMNI method has desirable features that include avoiding numerical differentiation of the forces, allowing for an efficient sparse matrix implementation, and ensuring that the kinematic constraint equations are satisfied at the position, velocity and acceleration levels. In this method, a sparse Lagrangian augmented form of the equations of motion that ensures that the constraints are satisfied at the acceleration level is used to solve for all the accelerations and Lagrange multipliers. The generalized coordinate partitioning or recursive methods can be used to satisfy the constraint equations at the position and velocity levels. In order to improve the efficiency and robustness of the TLISMNI method, the simple iteration and the Jacobian-Free Newton−Krylov approaches are used in this investigation. The new implementation is tested using several low order formulas that include Hilber–Hughes–Taylor (HHT), L-stable Park, A-stable Trapezoidal, and A-stable BDF methods. The HHT method allows for including numerical damping. Discussion on which method is more appropriate to use for a certain application is provided. The paper also discusses TLISMNI implementation issues including the step size selection, the convergence criteria, the error control, and the effect of the numerical damping. The use of the computer algorithm described in this paper is demonstrated by solving complex rigid and flexible tracked vehicle models, railroad vehicle models, and very stiff structure problems. The results, obtained using these low order formulas, are compared with the results obtained using the explicit Adams–Bashforth predictor-corrector method. Using the TLISMNI method, which does not require numerical differentiation of the forces and allows for an efficient sparse matrix implementation, for solving complex and stiff structure problems leads to significant computational cost saving as demonstrated in this paper. In some problems, it was found that the new TLISMNI implementation is 35 times faster than the explicit Adams–Bashforth method.

Low Order Continuum-Based Liquid Sloshing Formulation for Vehicle System Dynamics

The objective of this investigation is to develop a low order continuum-based liquid sloshing model that can be successfully integrated with multibody system (MBS) algorithms. The liquid sloshing model proposed in this investigation allows for capturing the effect of the distributed inertia and viscosity of the fluid. The fluid viscous forces are defined using the Navier–Stokes equations. In order to demonstrate the use of the approach presented in this study, the assumption of an incompressible Newtonian fluid is considered with a total Lagrangian approach. Fluid properties such as the incompressibility condition are formulated using a penalty method. The low order model that captures the effect of the distributed fluid inertia on the vehicle dynamics is developed in this investigation using the floating frame reference (FFR) formulation. The use of this approach allows for developing an inertia-variant fluid model that accounts for the dynamic coupling between different modes of the fluid displacements. The matrix of position vector gradients and its derivative are formulated using the FFR kinematic description. The position and velocity gradient tensors are used to define the Navier–Stokes stress forces. The proposed liquid sloshing model is integrated with a MBS railroad vehicle model in which the rail/wheel interaction is formulated using a 3D elastic contact formulation that allows for the wheel/rail separation. Several simulation scenarios are used to examine the effect of the distributed liquid inertia on the motion of the railroad vehicle. The results, obtained using the sloshing model, are compared with the results obtained using a rigid body vehicle model. The comparative numerical study presented in this investigation shows that the effect of the sloshing tends to increase the possibility of wheel/rail separation as the forward velocity increases, thereby increasing the possibility of derailments at these relatively high speeds.

Study of the active radial steering of a railway vehicle using the curvature measuring method

This study assesses the capability of an active steering bogie to run effectively on a curved track. It presents a curvature measuring method that can be implemented in a railway vehicle system to steer a railway vehicle. This method was used to conduct a field test. The angle of attack and lateral force were reduced in a railway vehicle model on a curved track and analyzed. An active steering system was implemented to improve certain states when a railway vehicle runs on this track, such as wear and derailment index. The railway vehicle was also equipped with an active steering bogie to limit lateral contact forces and wear rates between the wheel and the rail. Finally, this paper describes the modeling of this active steering system and of a system to control the performance of a vehicle as it curves. Simulation results with this bogie were better than those obtained with a conventional railway vehicle, including in terms of lateral forces and the wear number of the wheels. Therefore, the proposed model is more effective than conventional systems with respect to operation on a curved track.

The proposal of validation metrics for the assessment of the quality of simulations of the dynamic behaviour of railway vehicles

This paper introduces new validation metrics that may be used for the validation of models of railway vehicles. The proposed validation metrics are based on a comparison between the cumulative distribution functions of selected parameters obtained by simulation and measurements. A model of a freight railway vehicle has been developed and the proposed validation metrics were used in model validation. The results of the validation were compared with the results of validation metrics used in the ‘DynoTRAIN’ project. It was shown that the proposed metric is more severe than the metrics used in the project; a result of it comparing the complete domains of the cumulative distribution functions and not only the selected characteristic values.

Hybrid Skyhook-Stability Augmentation System for Ride Quality Improvement of Railway Vehicle

This paper is aimed to show the improvement of ride quality of railway vehicle with semi-active suspension systems. The dynamics of nine degrees-of-freedom (9-DOF) railway vehicle model is developed consists of a vehicle body, two bogies and four wheel-set. The disturbance considered is track irregularity which is modelled as a sine wave. The control algorithm for the semi-active suspension system is developed based on Stability Augmentation System (SAS) integrated with skyhook controller to reduce the effect of track disturbance. The performances of passive and semi-active suspension are compared by simulation using MATLAB-SIMULINK software. The results of the study show that the proposed controller is able to significantly improve ride quality of railway vehicle body. It is also noted that the additional ride control loop which is skyhook control is able to further improve the performance of SAS controller for the system.

H∞ control of railway vehicle suspension with MR damper using scaled roller rig

In this paper, a magneto-rheological (MR) damper was applied to the secondary suspension to reduce the vibration of a car body. The control performance of the MR damper was verified by numerical analysis with a 1/5 scale railway vehicle model in accordance with the similarity law. The analysis results were then validated in tests. In particular, the objective of the study was to understand how the control performance affected the dynamic characteristics of a railway vehicle and to systematically analyze the relationship between control performance and dynamic characteristics depending on various running speeds. To achieve this, experimental results for the dynamic characteristics of the scaled MR damper designed for the 1/5 scale railway vehicle model were applied to the railway vehicle model. The H∞ control method was applied to the controller. The means of designing the railway vehicle body vibration controller and the effectiveness of its results were studied.

Modeling and Simulation of Railway Vehicle Using ADAMS/Rail

The aim of this paper is to develop computer simulation model of railway vehicle using multibody system (MBS) package. ADAMS/Rail was used in modeling and simulating complex realistic railway vehicle system to study their dynamics response to curve and straight track inputs. The Malaya Railway Limited or Keretapi Tanah Melayu Berhad (KTMB) railway vehicle is used as reference model to develop computer simulation model in ADAMS/rail. Curve track input was based on KTMB rail network with maximum curve radius of 1000 m. Straight track input with random vertical irregularity was applied to the 1000 m track to evaluate the vehicle behavior response to track vertical roughness. The results show the roll angle, lateral and vertical acceleration of the carbody was increases with the increases of vehicle speed.

급곡선 주행 안정화를 위한 주행방향 크리피지 특성 최적화 연구

도시철도는 도심내를 운행하는 철도차량으로써, 도시철도 이용이 활발해지고 운행 계획에 따라 급곡선 구간의 운용이 필요할 것으로 예상된다. 하지만 이러한 급곡선 선로에서는 철도차량의 주행 안정성이 현저히 감소하며 크리피지가 증가하게 된다. 크리피지는 차륜이 레일 위를 구를 때 접촉면에서의 속도차에 의한 미끄러짐 량으로 차륜 마모, 진동 등의 원인이 된다. 따라서 크리피지를 줄이는 것은 주행 안정성 확보 및 환경 문제, 비용 저감에 도움을 줄 수 있다. 본 논문에서는 급곡선 선로 주행에 의한 주행방향 크리피지 발생 정도를 전동차를 모델링하여 분석하고 나아가서 급곡선 선로 주행 시 발생할 수 있는 문제점을 최소화하기 위한 대차 특성을 최적화한다. Urban railway vehicles operate in downtown areas. Due to increases in the number of passengers and changes in the service plans, railway vehicles are expected to operate on sharp curved tracks. However, on these tracks, the running stability of the railway vehicles is significantly decreased and the creepage is increased. Creepage causes the wheel/rail to wear and vibration. Therefore, reducing the creepage helps ensure the running stability and can be beneficial for the environment and cost. In this paper, the longitudinal creepage is analyzed using a railway vehicle model on a sharp curved track. Furthermore, in order to minimize the problems when a railway vehicle runs on a sharp curved track, the characteristics of a bogie are optimized using response optimization.

Estimation of the parameters of a railway vehicle suspension using model-based filters with uncertainties

This paper presents two types of extended Kalman filter (EKF) and two types of unscented Kalman filter (UKF) based on vertical railway vehicle models for parameters estimation of secondary suspensions. Due to track irregularities, the random vertical velocity of the track can be approximated as a zero-mean Gaussian white noise and it is used to excite the dynamic model of the railway vehicle. Under this approximation, the variance of the vertical velocity of the track, which is affected by the track roughness level and vehicle velocity, can introduce uncertainty into the system. Based on the random track irregularity, two cases are proposed to determine how the track irregularities enter the system. One case uses the vertical velocity and displacement of the track as inputs of the system and assumes that the state variables are corrupted by the Gaussian noises. The other case assumes that the vertical velocity of the track is the process noise of the system. Based on these two cases, two types of EKF and UKF are developed to estimate the parameters of the secondary suspensions. In order to study the performances of the proposed EKFs and UKFs, several simulation experiments using linear and nonlinear model are carried out that consider the uncertainties of the random track.

A new approach to define criteria for rail vehicle model validation

Validation of railway vehicle models is an important condition for the application of multi-body system simulations in the context of vehicle authorisation. Validation investigations carried out in the DynoTRAIN project represent a unique investigation. The measurements, received from a set of vehicles running through four European countries equipped with a simultaneous recording of track irregularities and rail profiles, were compared with simulations using vehicle models built in different simulation tools by several partners. The presented analyses resulted in a proposal of model validation based on 12 quantities covering the quasi-static and dynamic wheel/rail force measurements and vertical as well as lateral vehicle body accelerations. For each quantity, a set of at least 24 comparisons between simulations and measurements are evaluated using values based on EN 14363 from at least 12 sections, which represent all 4 test zones according to EN 14363. The proposed method, criteria and limit values are intended for the validation of vehicle models applied in the vehicle acceptance process.