Showing papers in "Vehicle System Dynamics in 2009"
TL;DR: In this article, a three-dimensional vehicle-track coupled dynamics model is developed in which a typical railway passenger vehicle is modelled as a 35-degree-of-freedom multi-body system.
Abstract: This paper presents a framework to investigate the dynamics of overall vehicle-track systems with emphasis on theoretical modelling, numerical simulation and experimental validation. A three-dimensional vehicle-track coupled dynamics model is developed in which a typical railway passenger vehicle is modelled as a 35-degree-of-freedom multi-body system. A traditional ballasted track is modelled as two parallel continuous beams supported by a discrete-elastic foundation of three layers with sleepers and ballasts included. The non-ballasted slab track is modelled as two parallel continuous beams supported by a series of elastic rectangle plates on a viscoelastic foundation. The vehicle subsystem and the track subsystem are coupled through a wheel-rail spatial coupling model that considers rail vibrations in vertical, lateral and torsional directions. Random track irregularities expressed by track spectra are considered as system excitations by means of a time-frequency transformation technique. A fast explicit integration method is applied to solve the large nonlinear equations of motion of the system in the time domain. A computer program named TTISIM is developed to predict the vertical and lateral dynamic responses of the vehicle-track coupled system. The theoretical model is validated by full-scale field experiments, including the speed-up test on the Beijing-Qinhuangdao line and the high-speed running test on the Qinhuangdao-Shenyang line. Differences in the dynamic responses analysed by the vehicle-track coupled dynamics and by the classical vehicle dynamics are ascertained in the case of vehicles passing through curved tracks.
620 citations
TL;DR: In this article, a new coordination scheme based on optimal guaranteed cost control technique by coordinating active front steering and direct yaw moment control is proposed, considering the uncertainty of tyre cornering stiffness due to the frequent variation of running conditions.
Abstract: Considering the uncertainty of tyre cornering stiffness due to the frequent variation of running conditions, a new coordination scheme is proposed based on optimal guaranteed cost control technique by coordinating active front steering and direct yaw moment control. A general procedure to develop an optimal guaranteed cost coordination controller (OGCC) is presented, and the effect of uncertainty deviation magnitude on the control system is discussed. An optimal coordination (OC) scheme based on LQR is also presented. Many simulations are carried out on an 8-DOF nonlinear vehicle model for a slalom manoeuvre and a lane-change manoeuvre, respectively. The simulation results show that the OGCC scheme has superior stability and tracking performances at different running conditions compared with the OC scheme.
198 citations
TL;DR: In this paper, the performance benefits of train suspension systems employing a new mechanical network element called an inerter were investigated, which is a true mechanical two-terminal element with the applied force proportional to the relative acceleration across the terminals.
Abstract: This paper investigates the performance benefits of train suspension systems employing a new mechanical network element called an inerter. An inerter is a true mechanical two-terminal element with the applied force proportional to the relative acceleration across the terminals. Until now, ideal inerters have been applied to car and motorcycle suspension systems, for which a significant performance improvement was reported. In this paper, we discuss the performance benefits of train suspension systems employing inerters. The study was carried out in three phases. First, fixed suspension structures were applied to train suspension systems, and optimised for two performance measures. Secondly, this optimisation was further carried out using linear matrix inequality approaches to discuss the achievable performance of passive networks. The resulting networks can then be realised by synthesis methods, such as the Brune and Bott–Duffin realisation. Finally, the nonlinear properties of inerter models and their im...
170 citations
TL;DR: In this paper, a review of recent research on the cross-wind effects on road and rail vehicles is presented, including a detailed methodology for using this information to predict accident risk, including details of the vehicle dynamics system models that can be used.
Abstract: This paper presents a review of recent research that has been carried out on the cross-wind effects on road and rail vehicles. After a brief introduction to the issues involved, the risk analysis framework is set out. All risk analysis methods require some knowledge of cross-wind aerodynamic force and moment coefficients, and methods of obtaining these through full scale and wind tunnel testing and through Computational Fluid Dynamics methods are then described. The picture of the flow fields around vehicles that is suggested by these measurements and calculations is then presented, and the steady and the unsteady aerodynamic force characteristics described. The detailed methodology for using this information to predict accident risk is then set out, including details of the vehicle dynamics system models that can be used. Finally potential alleviation methods are described and suggestions made for further works.
145 citations
TL;DR: In this article, the authors derived analytical solutions for the global optimum of the ride comfort and tyre grip performance measures for a quarter-car vehicle model optimised both individually and in combination.
Abstract: The paper derives analytical solutions for the global optimum of the ride comfort and tyre grip performance measures for a quarter-car vehicle model optimised both individually and in combination. The solutions are derived for six simple suspension networks comprising one or two springs, one damper and possibly one inerter. The solutions are functions of four vehicle parameters: the sprung mass, the unsprung mass, the tyre stiffness and the static stiffness, of the suspension.
117 citations
TL;DR: In this paper, a detailed multibody model of the catenary and the pantograph is presented for the identification of the dynamic behaviour of the pantographs and of the interaction phenomena in the catenaries of high-speed trains due to the action of aerodynamics forces.
Abstract: Most of the high-speed trains in operation today have the electrical power supply delivered through the pantograph-catenary system. The understanding of the dynamics of this system is fundamental since it contributes to decrease the number of incidents related to these components, to reduce the maintenance and to improve interoperability. From the mechanical point of view, the most important feature of the pantograph-catenary system consists in the quality of the contact between the contact wire of the catenary and the contact strips of the pantograph. The catenary is represented by a finite element model, whereas the pantograph is described by a detailed multibody model, analysed through two independent codes in a co-simulation environment. A computational procedure ensuring the efficient communication between the multibody and finite element codes, through shared computer memory, and suitable contact force models were developed. The models presented here are contributions for the identification of the dynamic behaviour of the pantograph and of the interaction phenomena in the pantograph-catenary system of high-speed trains due to the action of aerodynamics forces. The wind forces are applied on the catenary by distributing them on the finite element mesh. Since the multibody formulation does not include explicitly the geometric information of the bodies, the wind field forces are applied to each body of the pantograph as time-dependent nonlinear external forces. These wind forces can be characterised either by using computational fluid dynamics or experimental testing in a wind tunnel. The proposed methodologies are demonstrated by the application to real operation scenarios for high-speed trains, with the purpose of defining service limitations based on train and wind speed combination.
110 citations
TL;DR: The validation of simulation results is increasingly important, and this paper discusses recent trends in this area, and takes a brief look forward to future simulation issues.
Abstract: Rail vehicle dynamic simulation has progressed a long way from its origins as a research tool. Modern multibody software packages are used as an essential part of the design process for new vehicle ...
110 citations
TL;DR: In this paper, a 17-degree-of-freedom (DOF) model of a full-scale railway vehicle integrated with the semi-active controlled magnetorheological (MR) fluid dampers in its secondary suspension system is proposed to cope with the lateral, yaw, and roll motions of the car body, trucks, and wheelsets.
Abstract: In this paper, it is aimed to investigate semi-active suspension systems using magnetorheological (MR) fluid dampers for improving the ride quality of railway vehicles. A 17-degree-of-freedom (DOF) model of a full-scale railway vehicle integrated with the semi-active controlled MR fluid dampers in its secondary suspension system is proposed to cope with the lateral, yaw, and roll motions of the car body, trucks, and wheelsets. The governing equations combining the dynamics of the railway vehicle integrated with MR dampers in the suspension system and the dynamics of the rail track irregularities are developed and a linear quadratic Gaussian (LQG) control law using the acceleration feedback is adopted, in which the state variables are estimated from the measurable accelerations with a Kalman estimator. In order to evaluate the performances of the semi-active suspension systems based on MR dampers for railway vehicles, the random and periodical track irregularities are modelled with a uniform state-space formulation according to the testing data and incorporated into the governing equation of the railway vehicle integrated with the semi-active suspension system. Utilising the governing equations and the semi-active controller developed in this paper, the simulation and analysis are presented in Part II of this paper.
109 citations
TL;DR: In this paper, the authors discuss the importance of wheel-rail interface management for railway operation and its maintenance represents a major share of the total maintenance cost. In general, the course of events usually called wear i...
Abstract: Wheel-rail interface management is imperative to railway operation and its maintenance represents a major share of the total maintenance cost. In general, the course of events usually called wear i ...
101 citations
TL;DR: In this paper, the estimation process is separated into three blocks: the first block identifies the vehicle's mass, the second block contains a linear observer whose main role is to estimate the roll angle and the one-side lateral transfer load, while in the third block compared linear and nonlinear models for the estimation of four wheel vertical forces.
Abstract: Knowledge of vehicle dynamics data is important for vehicle control systems that aim to enhance vehicle handling and passenger safety. This study introduces observers that estimate lateral load transfer and wheel-ground contact normal forces, commonly known as vertical forces. The proposed method is based on the dynamic response of a vehicle instrumented with cheap and currently available standard sensors. The estimation process is separated into three blocks: the first block serves to identify the vehicle's mass, the second block contains a linear observer whose main role is to estimate the roll angle and the one-side lateral transfer load, while in the third block we compare linear and nonlinear models for the estimation of four wheel vertical forces. The different observers are based on a prediction/estimation filter. The performance of this concept is tested and compared with real experimental data acquired using the INRETS-MA (Institut National de Recherche sur les Transports et leur Securite - Departement Mecanismes d'Accidents) Laboratory car. Experimental results demonstrate the ability of this approach to provide accurate estimation, thus showing its potential as a practical low-cost solution for calculating normal forces.
86 citations
TL;DR: In this article, an automatic path-tracking controller of a four-wheel steering (4WS) vehicle based on the sliding mode control theory is proposed, where the front and rear wheel steering can be decoupled at the control points defined as centres of percussion with respect to the rear and front wheels.
Abstract: The present paper proposes an automatic path-tracking controller of a four-wheel steering (4WS) vehicle based on the sliding mode control theory. The controller has an advantage in that the front- and rear-wheel steering can be decoupled at the front and rear control points, which are defined as centres of percussion with respect to the rear and front wheels, respectively. Numerical simulations using a 27-degree-of-freedom vehicle model demonstrated the following characteristics: (1) the automatic 4WS controller has a more stable and more precise path-tracking capability than the 2WS controller, and (2) the automatic 4WS controller has robust stability against system uncertainties such as cornering power perturbation, path radius fluctuation, and cross-wind disturbance.
TL;DR: In this article, a review of state-of-the-art studies on brake vibration and noise is presented, focusing on the still-open questions that appear crucial from the perspective of a leading brake manufacturer.
Abstract: Several state of the art papers and even books on brake vibration and/or noise have been presented in the literature. Many of them have analytically and sharply accounted for the impressive amount of research undertaken on this topic. This state of the art review focuses on the still-open questions that appear crucial from the perspective of a leading brake manufacturer. The paper deals with the phenomena of brake vibration and/or noise, the experimental and theoretical methods for studying such phenomena, and the actions that are identified to be necessary to definitely solve the addressed problem. Key topics are the modelling of friction, the modelling of the dynamics of the brake as a non-linear system subjected to deterministic or random (parametric) excitation, the proper modelling of the contact between the disc and the pad, and the experimental validation of the mathematical models.
TL;DR: In this article, a mathematical model of train-turnout interaction in the mid-frequency range (0-500 Hz) is proposed, which accounts for the effects of rail profile variation along the track and of local variation of track flexibility.
Abstract: The paper proposes a mathematical model of train–turnout interaction in the mid-frequency range (0–500 Hz). The model accounts for the effects of rail profile variation along the track and of local variation of track flexibility. The proposed approach is able to represent the condition of one wheel being simultaneously in contact with more than one rail, allowing the accurate prediction of the effect of wheels being transferred from one rail to another when passing over the switch toe and the crossing nose. Comprehensive results of train–turnout interaction during the negotiation of the main and the branch lines are presented, including the effect of wear of wheel/rail profiles and presence of track misalignment. In the final part of the paper, comparisons are performed between the results of numerical simulations and line measurements performed on two different turnouts for urban railway lines, showing a good agreement between experimental and numerical results.
TL;DR: An algorithm is presented to classify terrain using a single suspension-mounted accelerometer to classify multiple terrain types with reasonable accuracy at a range of typical automotive speeds and it is shown that the removal of terrain impulses prior to classification improves classifier performance.
Abstract: Terrain physical characteristics can have a significant impact on passenger vehicle handling, ride quality, and stability. Here, an algorithm is presented to classify terrain using a single suspension-mounted accelerometer. The algorithm passes a measured acceleration signal through a dynamic vehicle model to estimate the terrain profile, and then extracts spatial frequency components of this estimated profile. A method is introduced to identify and remove terrain impulses from the profile that are caused by ruts and potholes. Finally, a supervised support vector machine is employed to classify profile segments as members of pre-defined classes (such as asphalt, brick, gravel, etc.). The classification algorithm is validated with experimental data collected with a passenger vehicle driving in real-world conditions. The algorithm is shown to classify multiple terrain types with reasonable accuracy at a range of typical automotive speeds. It is also shown that the removal of terrain impulses prior to classification improves classifier performance.
TL;DR: In this paper, the semi-active suspension system for railway vehicles based on the controlled fluid dampers is investigated, and compared with the passive on and passive off suspension systems, while the car body accelerations of the railway vehicle integrated with four MR dampers in the secondary suspension systems are simulated under the random and periodical track irregularities using the established governing equations of a railway vehicle and the modelled track irregularities.
Abstract: In this paper, the semi-active suspension system for railway vehicles based on the controlled (MR) fluid dampers is investigated, and compared with the passive on and passive off suspension systems. The lateral, yaw, and roll accelerations of the car body, trucks, and wheelsets of a full-scale railway vehicle integrated with four MR dampers in the secondary suspension systems, which are in the closed and open loops respectively, are simulated under the random and periodical track irregularities using the established governing equations of the railway vehicle and the modelled track irregularities in Part I of this paper. The simulation results indicate that (1) the semi-active controlled MR damper-based suspension system for railway vehicles is effective and beneficial as compared with the passive on and passive off modes, and (2) while the car body accelerations of the railway vehicle integrated with semi-active controlled MR dampers can be significantly reduced relative to the passive on and passive off ...
TL;DR: In this article, the authors employed the Hilbert Huang transform (HHT), the wavelet transform and the Fourier transform to analyze the road surface profiles of three pavement profiles and found that the strength of HHT is the ability to process non-stationary and non-linear data.
Abstract: This study employs the Hilbert–Huang transform (HHT), the wavelet transform and the Fourier transform to analyse the road surface profiles of three pavement profiles. The wavelet and Fourier transforms have been the traditional spectral analysis methods, but they are predicated on a priori selection of basis functions that are either of infinite length or have fixed finite widths. The central idea of HHT is the empirical mode decomposition, which decomposes a signal into basis functions called the intrinsic mode functions (IMFs). The Hilbert transform can then be applied to the IMFs to generate an energy–time–frequency spectrum called the Hilbert spectrum. The strength of HHT is the ability to process non-stationary and non-linear data. Unlike the Fourier transform, which transforms information from the time domain into the frequency domain, the HHT does not lose temporal information after transformation, i.e. energy–frequency information is maintained in the time domain. This paper attempts to reveal the...
TL;DR: In this paper, the authors proposed a nonlinear model of the Macpherson strut suspension system for ride control applications, which includes the vertical acceleration of the sprung mass and incorporates the suspension linkage kinematics.
Abstract: The main purpose of this paper is to propose a new nonlinear model of the Macpherson strut suspension system for ride control applications. The model includes the vertical acceleration of the sprung mass and incorporates the suspension linkage kinematics. This two-degree-of-freedom (DOF) model not only provides a more accurate representation of the Macpherson suspension system for control applications in order to improve the ride quality, but also facilitates evaluation of the suspension kinematic parameters, such as camber, caster and king-pin angles as well as track alterations on the ride vibrations. The performances of the nonlinear and linearised models are investigated and compared with those of the conventional model. Besides, it is shown that the semi-active force improves the ride quality better than active force, while the opposite is true in terms of improving the performance of the kinematic parameters. The results of variations of the kinematic parameters based on the linear model subject to ...
TL;DR: In this article, the effects of the guideway's vibrational characteristics, such as natural frequency and damping, on the dynamics of the UTM-02 are numerically and experimentally analyzed.
Abstract: The levitation control system in an electromagnetically levitated vehicle controls the voltage in its winding to maintain the air gap, which is the clearance between the electromagnet and the guideway, within an allowable range of variation, while strongly interacting with the flexible guideway. Thus, the vibrational characteristics of the guideway play an important role in the dynamics of Maglev (magnetically levitated) vehicles that utilise an active electromagnetic suspension system. In this study, the effects of the guideway's vibrational characteristics, such as natural frequency and damping, on the dynamics of the Maglev vehicle UTM-02 are numerically and experimentally analysed. From these analyses, the coupled equations of motion of the simplified vehicle–guideway model with three degrees of freedom are derived. Eigenvalues are calculated and frequency response analysis is also performed, in order to obtain a clear understanding of the dynamic characteristics resulting from the guideway's vibratio...
TL;DR: In this article, a gain-scheduled active steering control and active differential design method is presented to preserve vehicle stability in extreme handling situations, in which a new formulation of the bicycle model in which tyre slip angles, longitudinal slips and vehicle forward speed appear as varying vehicle parameters is introduced.
Abstract: This paper presents a gain-scheduled active steering control and active differential design method to preserve vehicle stability in extreme handling situations. A new formulation of the bicycle model in which tyre slip angles, longitudinal slips and vehicle forward speed appear as varying vehicle parameters is introduced. Such a model happens to be useful in the design of vehicle dynamics controllers scheduled by vehicle parameters: after having expressed the parametric bicycle model in the parametric descriptor form, gain-scheduled active steering and differential controllers are designed to improve vehicle handling at ‘large’ driver-commanded steering angles. Simulations reveal the efficiency of the selected modelling and controller design methodology in enhancing vehicle handling capacity during cornering on roads with varying adhesion coefficient and under variable speed operation.
TL;DR: The article aims to present the results of identification of the driver model parameters on the basis of the resultsof track tests, and the proposed driver model adequate to this type of situation has been proposed.
Abstract: The study presents a brief description of driver models found in the literature. Despite the large number of models, in the case of pre-accident situations the existing driver models cannot be successfully used to reconstruct driver behaviour. A driver model adequate to this type of situation has been proposed. The scenario of a pre-accident situation has been described briefly. The article aims to present the results of identification of the driver model parameters on the basis of the results of track tests. An analysis of the obtained characteristics of the turning angle and deceleration has been made. The drivers studied have been divided into groups according to similar types of reactions. The identification has been conducted for the pre-defined four driver groups. Values and reaction time linear regression equations have been specified for braking and wheel turns on the track. The results of identification of the remaining model parameters on the basis of test results have been presented.
TL;DR: In this paper, the authors proposed the solution of state-dependent Riccati equation as a nonlinear optimal regulator to stabilise the motion dynamics of the vehicle model subjected to sudden disturbance inputs in the lateral direction.
Abstract: This paper proposes the solution of state-dependent Riccati equation as a nonlinear optimal regulator to stabilise the motion dynamics of the vehicle model subjected to sudden disturbance inputs in the lateral direction. The proposed nonlinear regulator coordinates individually actuated wheel braking torque and steering wheel angle simultaneously in an optimal manner. Performance criteria are satisfied by solving the Riccati equation based on the given cost function subjected to the nonlinear vehicle dynamics. On-line control allocation in terms of optimal brake torque distribution enhanced by optimal wheel steering angle input is achieved. Furthermore, the proposed optimal nonlinear regulator is an active fault-tolerant control system against partial by-wire actuator failures while guaranteeing stability with good performance due to its capability to allocate the individual control inputs in an optimal way. The main aim is to stabilise the motion dynamics of the vehicle model during short-term emergency ...
TL;DR: In this article, a fault detection and condition monitoring of vehicle suspensions is presented, which exploits the dynamic interactions between different vehicle modes caused by component failures in the system, leading to a simple but effective solution.
Abstract: A novel scheme for the fault detection and condition monitoring of vehicle suspensions is presented in this study. The new technique exploits the dynamic interactions between different vehicle modes caused by component failures in the system, leading to a simple but effective solution. Compared with many model-based fault detection techniques, the proposed technique does not require complex mathematical models of the system and it overcomes potential difficulties associated with nonlinearities and parameter variations in the system. The use of inexpensive inertial sensors and ease of tuning make the practical implementation of the proposed scheme straightforward. A conventional railway vehicle is used in the study to illustrate the basic ideas as well as the effectiveness of the novel fault detection method, although the general principle is applicable to other systems.
TL;DR: In this paper, the authors apply linear preview control to driving road vehicles with only modest excursions from a straight-running equilibrium state to the general large-lateral motion arena and find the optimal control for steady-cornering trim states of an exemplary car at a given speed as a function of cornering effort.
Abstract: The paper is concerned with modelling car drivers. The context of the work presented is explained. Then, previous research on the application of optimal linear preview control theory to driving road vehicles with only modest excursions from a straight-running equilibrium state is extended into the general large-lateral-motion arena. Optimal controls are found for steady-cornering trim states of an exemplary car at a given speed as a function of cornering effort, up to the practical limit. The manner in which the optimal controls change as the cornering vigour changes is discussed. Simulations of the virtual driver-controlled car are shown to demonstrate the closed-loop system following lateral path demands and the advantages of employing gain-scheduled adaptive control over a fixed-control scheme are demonstrated.
TL;DR: In this paper, a new stability metric, termed the stability moment, is proposed that is accurate on terrain surfaces with arbitrary geometry, which allows it to be used in road departure scenarios.
Abstract: Vehicle rollover represents a significant percentage of single-vehicle accidents and accounts for over 9000 fatalities and over 200,000 non-fatal injuries each year. Previous research has yielded rollover stability control systems that are effective in on-road conditions. Accident statistics show, however, that over 90% of rollovers involve road departure, during which a vehicle may encounter sloped and rough terrain while travelling at high speed. A critical element of most rollover stability control systems is a metric that monitors a vehicle's nearness to rollover. Most metrics, however, are designed for use on flat, level surfaces characteristic of on-road terrain. In this paper, a new stability metric, termed the stability moment, is proposed that is accurate on terrain surfaces with arbitrary geometry, which allows it to be used in road departure scenarios. The metric is based on an estimate of the distribution of wheel–terrain contact forces. The metric can be calculated on line in real time, using...
TL;DR: In this article, the authors present a general presentation of the author's modelling methods used for solving problems relating to railway pneumatic brakes, taking into account air-wave phenomena including air viscosity, the influence of the brake pipe branches, heat transfer in the brake pipes and reservoirs, air flows in brake valves and the dynamics of moving mechanical parts.
Abstract: The design of new pneumatic brakes for rail vehicles or improvements of existing ones can be made better or more efficient by the use of a simulation method. This paper gives a general presentation of the author's modelling methods used for solving problems relating to railway pneumatic brakes. The brake models in this paper (slightly different from those of other authors) take into account air-wave phenomena including air viscosity, the influence of the brake pipe branches, heat transfer in the brake pipes and reservoirs, air flows in the brake valves and the dynamics of moving mechanical parts. For various simulation purposes, separate partial models with different levels of accuracy were created. Various verifications and identifications of the models were performed with the use of train brake testing facilities, including both in-house and other test stands. A variety of examples of simulation results are presented here.
TL;DR: In this paper, an innovative semi-analytic procedure for the detection of the wheel/rail contact points (called the DIFF method) is presented. But this method considers the wheel and the rail as two surfaces whose analytic expressions are known and is based on the idea that in the contact points the difference between the surfaces has local minima and is equivalent to solving an algebraic two-dimensional system.
Abstract: The multibody simulation of railway vehicle dynamics needs a reliable and efficient method to evaluate the contact points between wheel and rail, because their positions have a considerable influence on the direction and intensity of the contact forces. In this work, an innovative semi-analytic procedure for the detection of the wheel/rail contact points (named the DIFF method) is presented. This method considers the wheel and the rail as two surfaces whose analytic expressions are known and is based on the idea that in the contact points the difference between the surfaces has local minima and is equivalent to solving an algebraic two-dimensional system. The original problem can be reduced analytically to a simple scalar equation that can be easily solved numerically (since the problem dimension is one, even elementary non-iterative algorithms can be efficient).
TL;DR: Carbody tilting is today a mature and inexpensive technology allowing higher speeds in curves and thus reduced travel time as mentioned in this paper The technology is accepted by many train operators today more than 5000 tilting vehicles, defined as tilting carbodies, have been produced world-wide by different suppliers.
Abstract: Carbody tilting is today a mature and inexpensive technology allowing higher speeds in curves and thus reduced travel time The technology is accepted by many train operators Today more than 5000 tilting vehicles, defined as tilting carbodies, have been produced world-wide by different suppliers Tilting trains can be divided into naturally tilted trains and actively tilted trains However, also natural tilting will often include actuation to ensure satisfactory dynamic performance The mechanical solutions for tilting involving pendulums or rollers are well proven They have also become compact enough to avoid passenger area intrusion The proportion of the lateral acceleration compensated by tilt has decreased over the years In the early days of tilting train development, it was often assumed that the compensation should be 100% Compensation of 50–70% are typically used in today's actively tilting trains, while natural tilting ones still retain compensation close to 100% Recent developments in contr
TL;DR: In this paper, the influence of road waviness on the vibration response variance of selected quantities of the travelling vehicle was investigated using simulations of various vehicle types, including the unevenness index and the travel speed.
Abstract: The simplest form of the power spectral density for characterising longitudinal road unevenness is as a line on a log–log chart The influence of waviness (the slope of the line) on the vibration response variance of selected quantities of the travelling vehicle was investigated using simulations of various vehicle types For expressing the response variance, besides the unevenness index and the travel speed raised to the power containing the longitudinal road waviness (v w−1), the integrated frequency response must also be taken into account The latter is dependent on the road waviness, but this last component may be expressed as a product of two factors One is dependent on the vehicle structure and the quantity to be measured, whereas the other is dependent on the waviness only This separation simplifies the study of the effect of waviness on various aspects of the vehicle dynamics Finally, a simplified method for estimating the unevenness index and waviness without knowing the longitudinal road pro
TL;DR: In this article, the curvature negotiation performance of an urban Maglev vehicle using a U-shaped electromagnet is evaluated using a multibody dynamic model. But the authors focus on the curvatures of the urban guideway.
Abstract: For electromagnetic suspension (EMS) type urban Maglev vehicles using a U-shaped electromagnet, the levitation and guidance forces are generated by only one electromagnet. Although the levitation force is actively controlled by changing the voltage of the electromagnet, the guidance force is passively determined by the levitation force. In addition, the curve negotiation performance of EMS-type urban Maglev vehicles using a U-shaped electromagnet must be considered, because an urban guideway may have some curves with shorter radii. It is, therefore, necessary to predict the curving performance with the greatest accuracy possible, in order to improve electromagnetic suspension and establish guideway design specifications. The objective is to establish a new dynamic modelling technique, so as to achieve more realistic curving simulation and thus to more accurately evaluate the curving performance of an EMS-type Maglev vehicle. The use of a full vehicle multibody dynamic model is proposed, and is applied to the evaluation of curving performance. Design changes are also investigated to obtain the bogie design directions for minimising variation in the lateral air gap, which is a criterion for curving performance.
TL;DR: In this paper, the authors studied the dynamics of nonlinear dynamic systems with the Duffing oscillator with harmonic excitation and showed that the probability of the multiple stable solutions will depend on the initial conditions.
Abstract: Nonlinear dynamic systems are well known to contain certain characteristic additional phenomena compared with linear systems. One example is the fact that nonlinear systems can have multiple stable solutions for one set of parameters. In that case, which one of the multiple stable solutions will be realised will depend on the initial conditions. From the domains of initial conditions which are domains of attraction, probabilities of occurrence of the stable solutions can be calculated. The described dynamical behaviour is studied in the present paper using two examples. To introduce the basic phenomena, the well-known academic Duffing oscillator with harmonic excitation is considered. Domains of attraction are shown for the two stable solutions and the probability of occurrence of the two solutions in the case of equally distributed initial conditions is calculated. The main example to be considered in this paper is the railway wheelset, which is known to show (depending on the nonlinearities in the model...