Showing papers in "Vehicle System Dynamics in 2002"
TL;DR: In this article, a control synthesis procedure using a linear vehicle model which includes the yaw motion and disturbance input with speed and road adhesion variations is presented, where the synthesis procedure allows the separate processing of the driver reference signal and robust stabilization problem or disturbance rejection.
Abstract: Summary This paper first analyses some stability aspects of vehicle lateral motion, then a coprime factors and linear fractional transformations (LFT) based feedforward and feedback H 8 control for vehicle handling improvement is presented. The control synthesis procedure uses a linear vehicle model which includes the yaw motion and disturbance input with speed and road adhesion variations. The synthesis procedure allows the separate processing of the driver reference signal and robust stabilization problem or disturbance rejection. The control action is applied as an additional steering angle, by combination of the driver input and feedback of the yaw rate. The synthesized controller is tested for different speeds and road conditions on a nonlinear model in both disturbance rejection and driver imposed yaw reference tracking maneuvers.
227 citations
TL;DR: In this paper, an eleven degrees of freedom, non-linear, multi-body dynamics model of a motorcycle is presented, which takes into account the geometric shape of tires and the elastic deformation of tire carcasses.
Abstract: This paper presents an eleven degrees of freedom, non-linear, multi-body dynamics model of a motorcycle. Front and rear chassis, steering system, suspensions and tires are the main features of the model. An original tire model was developed, which takes into account the geometric shape of tires and the elastic deformation of tire carcasses. This model also describes the dynamic behavior of tires in a way similar to relaxation models. Equations of motion stem from the natural coordinates approach. First, each rigid body is described with a set of fully cartesian coordinates. Then, links between the bodies are obtained by means of algebraic equations. This makes it possible to obtain simple equations of motion, even though the coordinates are redundant. The model was implemented in a Fortran code, named FastBike. In order to test the code, both simulated and real slalom and lane change maneuvers were carried out. A very good agreement between the numerical simulations and experimental test was found. The co...
191 citations
TL;DR: In this article, a full-vehicle suspension system with four independent magnetorheological dampers is constructed and its governing equations of motion including vertical, pitch and roll motions are derived.
Abstract: Summary This paper presents an investigation of the feedback control performance of a full-vehicle suspension system featuring magnetorheological (MR) dampers. A cylindrical MR damper is designed and manufactured by incorporating a Bingham model of aMR fluid which is commercially available. After evaluating the field-dependent damping characteristics of the MR damper, a full-vehicle suspension system installed with 4 independent MR dampers is constructed and its governing equations of motion which include vertical, pitch and roll motions are derived. A H 8 controller which has inherent robustness against system uncertainties is formulated by treating the sprung mass of the vehicle as uncertain parameter. This is accomplished by adopting the loop shaping design procedure. For the demonstration of a practical feasibility, control performance characteristics for vibration suppression of the proposed MR suspension system are evaluated under various road conditions through the hardware-in-the-loop simulation (...
156 citations
TL;DR: In this article, a non-linear rubber isolator included in a dynamic system is examined where influences of dynamic amplitude and frequency are investigated through measurements and modeling, and good agreement is obtained in a wide frequency and amplitude range for a freely oscillating one degree of freedom system, with the isolator acting as a coupling between exciting foundation and mass.
Abstract: A non-linear rubber isolator included in a dynamic system is examined where influences of dynamic amplitude and frequency are investigated through measurements and modeling. The frequency dependence of the isolator is modeled by a fractional calculus element while a frictional component accounts for its amplitude dependence. The model works in the time-domain and simulations of harmonic and non-harmonic motion are compared to measurements. Good agreement is obtained in a wide frequency and amplitude range for a freely oscillating one degree of freedom system, with the isolator acting as a coupling between exciting foundation and mass, and for a single isolator showing the typical amplitude dependence known as the Payne effect. The model is found to be superior to the commonly applied Kelvin-Voigt element in modeling the dynamic isolator properties.
151 citations
TL;DR: In this paper, the main features of a mathematical model for the simulation of pantograph-catenary dynamic interaction are presented and some aspects related to the catenary and pantograph schematisation are outlined.
Abstract: Summary The main features of a mathematical model for the simulation of pantograph-catenary dynamic interaction are presented and, in particular, some aspects related to the catenary and pantograph schematisation are outlined. The model enables to investigate the behaviour of the system in a relatively large frequency range (up to 100 Hz), due to the inclusion of the bending modes of the collector head. In order to simulate the contact between wire and collector, a procedure based on the penalty method is adopted, and it is shown by means of a numerical test case that the method reproduces the constraint acting at the pantograph-catenary interface over a wide frequency range with high accuracy, provided that suitable values are given to the contact parameters. The problem of minimising the numerical disturbances due to the discretisation of the contact wire is also discussed, showing that the entity of these disturbances can be reduced to acceptable values by adopting a proper discretisation of the contac...
150 citations
TL;DR: Based on the Transrapid system, a 10-degree-of-freedom model of a car running over three types of guideways with constant speed was developed in this paper, where random guideway irregularities were discussed and taken into account for simulation of the vehicle response and for evaluation of the ride comfort.
Abstract: Summary The research and development (R & D) of maglev technology had made a great progress in China since the early 1980s. Especially, a 35 km-long Shanghai high-speed maglev railway employing the German Transrapid system began to be constructed on March 1, 2001. Based on the Transrapid system, the paper develops a 10-degree-of-freedom model of maglev vehicle running over three types of guideways with constant speed. Random guideway irregularities are discussed and taken into account for simulation of the vehicle response and for evaluation of the ride comfort. Using the direct time integration method and the discrete fast Fourier transform (DFFT), random responses of the maglev vehicle-guideway systems are obtained and analyzed. Numerical results show that the resonant frequency of car body acceleration response is 0.5–1 Hz, and there is a 2.2 Hz periodic vibration due to the periodic configuration of rigid piers when the maglev vehicle travels over the elevated-beam guideway. The car body acceleration ...
130 citations
TL;DR: In this article, an Extended Kalman Filter (EKF) was used to estimate the vehicle mass and road slope using two different sensor configurations, one where speed is measured and one where both speed and specific-force is measured.
Abstract: SUMMARYKalman filtering is used as a powerful method to obtain accurate estimation of vehicle mass and road slope. First the problem of estimating the slope when the vehicle mass is known is studied using two different sensor configurations. One where speed is measured and one where both speed and specific-force is measured. A filter design principle is derived guaranteeing the estimation error under a worst case situation (when assuming first order dynamics). The simultaneous estimation problem required an Extended Kalman Filter (EKF) design when measuring speed only whereas the additional specific force ease yielded a simple filter structure with a time-variant measurement equation. Additionally the filter needs present propulsion force which in our case is calculated form the engine speed and amount of fuel injected. When the vehicle uses the foundation brakes the estimates are frozen since varying friction properties makes the braking force unknown. Both sensor configurations are concluded to be robus...
105 citations
TL;DR: In this paper, a wheel profile wear prediction toot is presented and verified by using a case study, where a methodology is introduced that is based an a load collective concept, where representative vehicle-track simulations are chosen to take into account parameters that affect wheel wear.
Abstract: A wheel profile wear prediction toot is presented and verified by using a case study. A methodology is introduced that is based an a load collective concept, where representative vehicle-track simulations are chosen to take into account parameters that affect wheel wear. Key parts of the toot are load collective design, vehicle-track simulations, wheel-rail contact response calculations, wear calculations and wheel profile updating. Simulated and measured wheel profiles and corresponding scalar wear measures agree well.
102 citations
TL;DR: In this paper, the authors describe an approach to set up a complex numerical model of the railway vehicle, suitable for reproducing its dynamic behaviour in the 0-50 Hz frequency range, especially with respect to the ride comfort problem.
Abstract: Summary Appropriate modelling of the dynamic behaviour of the vehicle components, particularly car body flexibility, is essential in the analysis of railway vehicle comfort performance, especially for high-speed vehicles. This paper deals with the description of the adopted approach to set up a complex numerical model of the railway vehicle, suitable for reproducing its dynamic behaviour in the 0–50 Hz frequency range, especially with respect to the ride comfort problem. The implemented model is used to simulate in time domain the dynamic behaviour of a vehicle running on irregular track. Numerical results are validated by means of comparison with experimental data of on-line tests. Finally, the analytical model is used to perform a sensitivity analysis, in order to point out the parameters that most significantly affect comfort.
90 citations
TL;DR: In this article, the static and dynamic behavior of the pantograph-catenary system was examined and the effect of the presag and the surface irregularities of contact wire on current collection was studied.
Abstract: Summary In order to examine the static and dynamic behavior of the pantograph-catenary system, a special teat facility is established and described in this paper. Since the catenary is difficult to be modeled by a hardware teat facility indoor, a mixed theoretical-experimental technique is introduced, in which the pantograph is an actual one but the catenary is just an input of a mathematical model. Bayed on setting up the hybrid simulation teat device of the pantograph-catenary system, the dynamic behavior of the system under overhead equipment with variant parameters is analyzed for different speed. The effect of the presag and the surface irregularities of contact wire on current-collection has been studied.
86 citations
TL;DR: In this article, different ways to actively damp the driveline oscillations are investigated, using the engine as an actuator in order to achieve active damping, so-called active engine control.
Abstract: When a vehicle is subjected to acceleration or disturbances, the elasticity of the various components in the driveline may cause torsional vibrations which can result in an oscillating vehicle speed. These driveline oscillations are also known as shuffle and are low frequency oscillations corresponding to the first resonance frequency of the driveline. The oscillations give rise to, apart from material stress, noticeable lessened driveability. In this work, different ways to actively damp the oscillations are investigated. The idea is to use the engine as an actuator in order to achieve active damping, so-called active engine control. Different linear controllers are investigated and evaluated. The paper includes driveline modelling, control design and verifications by simulations, and tests in real vehicle. Implementation issues such as limited amount of available engine torque and parameter identifications are also discussed. A Linear-Quadratic-Gaussion (LQG) controller has been implemented and tested o...
TL;DR: In this paper, the authors present the results of experimental and numerical investigations on regular wear of wheel profiles on a full-scale roller rig and allow to measure the evolution of wheel profile as well as contact forces and several quantities describing the motion of the wheelset.
Abstract: SUMMARYThe paper presents the results of experimental and numerical investigations on regular wear of wheel profiles. Experimental tests were performed on a full-scale roller rig and allowed to measure the evolution of wheel profiles as well as contact forces and several quantities describing the motion of the wheelset.As to the numerical investigations, a wear prediction model was developed, based on the interfacing of a multi-body simulation code for rail vehicle dynamics, of a local contact analysis model and of a material wear model that assumes a proportionality relationship between wear and frictional power. The validation of this model by comparisons with the measurement performed on the roller rig is still in progress. Some preliminary results are shown in this paper.
TL;DR: In this article, the authors present a framework for coupling software-tools specialized for the application in different fields of mechanics and/or physics, particularly if based on different mathematical methods.
Abstract: SUMMARYCo-Simulation gives a suitable framework for coupling software-tools specialized for the application in different fields of mechanics and/or physics, particularly if based on different mathematical methods For the computational analysis of a vehicle's running behaviour usually a Multibody System approach is used while flexible tracks—representing for example a bridge—are best examined with the help of Finite Element software Now, for the simulation of a vehicle running on a flexible track without neglecting the inherent interaction, an obvious and promising strategy is to simulate each of the two subsystems (vehicle and flexible track) with the appropriate software concurrently and to exchange the interfacing data at discrete communication points To minimize the numerical effort, the track's finite element model can be reduced modally to a linear description in a pre-processing step additionally; the resulting linear equations of motion of the track can then be solved analytically with high effi
TL;DR: Wang et al. as discussed by the authors proposed a numerical simulation technique that is used to investigate the dynamic train/track/bridge interaction, and two dynamic models are established to simulate the dynamic responses of a train running on the bridges with the ballasted track and the non-ballasted slab track.
Abstract: SUMMARYThis paper describes a numerical simulation technique that is used to investigate the dynamic train/track/bridge interaction. Two dynamic models are established to simulate the dynamic responses of a train running on the bridges with the ballasted track and the non-ballasted slab track, respectively. Effect of the track structure and the wheel/rail interaction on the system dynamics is considered in the models. The influence of track random irregularities on train/track/bridge dynamic interactions is investigated. The proposed simulation technique is applied to practical construction engineering in the Chinese first special railway line for passenger transport. The structural design of three extraordinary large bridges with non-ballasted tracks in this line is evaluated through a detailed simulation in the design stage and results show that these bridges are able to satisfy the demand of dynamic performance for the high-speed transport.
TL;DR: In this paper, an existing state-space based numerical method to simulate vertical dynamic interaction between a rolling train and a railway track is improved and extended to enable general three-dimensional motion of a train traversing a track.
Abstract: Summary An existing state-space based numerical method to simulate vertical dynamic interaction between a rolling train and a railway track is improved and extended. The model is extended to enable general three-dimensional motion of a train traversing a track. For the vehicle description a multibody dynamics method is used which allows for flexible components, for example, wheelsets. The track model is accordingly made three-dimensional in the sense that it allows for deflections and forces in all three directions at the wheel-rail contact. A track and a train in general motion imply two-dimensional modelling of the contact surface. Therefore, a linearised contact model including contact zone detection is proposed. The equations of motion of the system are formulated in a first-order form. The generalised dynamic train-track interaction model is verified against existing programs and good agreement of the results is obtained.
TL;DR: In this article, a torque estimation-based robust controller for passenger car torque converter clutch slip system is presented, which uses only the measurements available from inexpensive sensors that are installed in current passenger vehicles for torque estimation and feedback control.
Abstract: In this paper, a torque-estimation-based robust controller for passenger car torque converter clutch slip system is presented. The proposed robust controller uses only the measurements available from inexpensive sensors that are installed in current passenger vehicles for torque estimation and feedback control. A conventional full state observer along with a neural-network-based open-loop hydraulic actuator observer is designed to estimate the unknown driving load, and a neural-network-based turbine torque estimator considering the temperature of oil circulating the torque converter is developed for improved turbine torque estimation accuracy. The stability of the internal dynamics is also investigated, and the performance and robustness of the robust controller is validated by simulation studies.
TL;DR: In this paper, the effects of the wave reflections between the wheels on the contact force were studied, and it was shown that the contact forces can have up to four main peaks in the frequency region 550-1200?Hz due to the wave reflection between wheels, so that the wavelengths of short pitch corrugation can be associated with multiple frequencies.
Abstract: The wheel/rail contact forces are calculated in the frequency domain using a track model with multiple wheels on the rail. The effects of the wave reflections between the wheels on the contact force are studied. Different pad stiffnesses are used in the calculations to investigate the influence on the contact force. It is shown that the contact force can have up to four main peaks in the frequency region 550–1200?Hz due to the wave reflections between the wheels, so that the wavelengths of short pitch corrugation can be expected to be associated with multiple frequencies. As a conclusion, it is recommended that in a model for predicting short pitch corrugation the effects of multiple wheel/rail interactions need to be included.
TL;DR: In this article, a two-dimensional mathematical model for the motion of a bicycle-rider system with wheel suspensions with uneven track is described, focusing on the prediction of vibrational stress on the rider due to uneven track.
Abstract: The paper describes a two-dimensional mathematical model for the motion of a bicycle-rider system with wheel suspensions. It focusses on the prediction of vibrational stress on the rider due to uneven track. The model was evaluated by comparing its predictions with measuring data concerning weighted accelerations on the human body, depending on various bicycle designs and road surfaces. For the intended purpose the predictions for vibrational stress and vibrational behaviour are sufficiently precise, and the model turns out to be adequate for designing and developing bicycle suspensions.
TL;DR: In this paper, the authors developed a thermomechanical model representing all these phenomena with good approximation and being compatible with the natural laws of thermodynamics for estimating the time-dependent dynamical loads when riding, for example, over potholes or other obstacles.
Abstract: In the development of cars numerical simulation plays a more and more important role. A method commonly used in this context is based on the formalism of multibody dynamics. In this approach a vehicle is described as a system of rigid bodies connected by joints, bushings, springs and dampers. For the purpose of estimating the time-dependent dynamical loads when riding, for example, over potholes or other obstacles we need enhanced models representing the mechanical behavior of the shock absorbers. A model of this type should describe the nonlinear rate dependence of the force in combination with friction effects and thermomechanical coupling phenomena. Due to the dissipation of energy the temperature of the shock absorber increases and influences its damping behavior. When riding over long rugged test tracks these effects are strongly pronounced. Thus we develop a thermomechanical model representing all these phenomena with good approximation and being compatible with the natural laws of thermodynamics. T...
TL;DR: This paper describes a single steering controller that achieves all performance objectives of the BRT concept and various data collected during several public demonstrations are presented to illustrate the effectiveness of the approach.
Abstract: Bus Rapid Transit (BRT) is an effective alternative for providing rail-like corridor transit service. An advanced BRT concept involves the use of automated buses to provide functions of a rail transit system. A vehicle under automatic steering control following a prescribed trajectory is operated like a train on a rail. A lateral position sensing that uses roadway markers, such as magnetic markers embedded under the roadway, as lateral reference is one of the promising approaches for a reliable sensing system. The BRT concept requires the steering control system to consistently perform all necessary steering functions from high speed driving to low speed precision docking. This paper describes a single steering controller that achieves all performance objectives. Various data collected during several public demonstrations are presented in this paper to illustrate the effectiveness of the approach. These data include the following automatic steering control scenarios: over 100 mph high-speed driving, high-...
TL;DR: In this paper, the effect of the presag of contact wire on current-feeding is studied, and the reasonable presag is proposeded based on setting up the model, the dynamic behavior of pantograph/catenary system under condition of China railway system is studied.
Abstract: SUMMARYIn order to simulate the dynamic behavior of pantograph/catenary system accurately, a complicated simulation model in vertical is set up, in which not only the pantograph and catenary are included, but also the locomotive and track with irregularity are considered. Based on setting up the model, the dynamic behavior of pantograph/catenary system under condition of China railway system is studied. The parameters of catenary such as length of span, structure height and tension, and structure type of catenary with simple stitched wire or elasticity stitched wire are analyzed. In this paper, the effect of the presag of contact wire on current-feeding is studied, and the reasonable presag is proposeded. The irregularity of contact wire is firstly considered, and its influence on contact force is investigated. In order to improve the dynamic behavior of pantograph/catenary system, the parameters of pantograph such as stiffness, damping and mass are analyzed.
TL;DR: In this paper, the authors proposed an extension for the creep force calculation in the case of dry friction, based on the creep forces law of Shen, Hedrick and Elkins.
Abstract: SUMMARYSome characteristics of measured creep force curves cannot be explained with common theories of rolling contact. This work proposes extensions for creep force calculation in the case of dry friction. It is based on the creep force law of Shen, Hedrick and Elkins. The approximate consideration of the surface roughness yields a reduced initial slope whereas the introduction of a temperature dependent coefficient of friction can explain the decrease of creep forces at high creepages. The creep force curves calculated with the new model show the same characteristics as in measurements.
TL;DR: In this paper, the lateral stability of a rail vehicle is optimized using a combination of multibody dynamics, sequential quadratic programming, and a genetic algorithm, and several steps are taken to validate this integrated approach and to show its effectiveness.
Abstract: Summary The lateral stability of a rail vehicle is optimized using a combination of multibody dynamics, sequential quadratic programming, and a genetic algorithm. Several steps are taken to validate this integrated approach and to show its effectiveness. First, a hand-derived solution to a 17 degree of freedom linear rail vehicle model is compared to the simulation results from the A'GEM multibody dynamics software. Second, the calculation of the ‘critical speed’ (above which a rail vehicle response becomes unstable) using sequential quadratic programming is validated for a specific example. In the process, the existence of sharply-discontinuous ‘cliffs’ in the plots of critical speed versus suspension stiffnesses are identified. These cliffs, which are due to switching of the least-damped mode in the system, greatly hinder the application of gradient-based optimization methods. Two methods that do not require gradient information, a genetic algorithm and the Nelder-Mead's Simplex algorithm, are used to o...
TL;DR: In this paper, a mechanical model for the vertical response of the bolster and friction-wedge suspension elements in a railroad freight truck is developed, which incorporates linear stiffnesses and dry friction contact between rigid elements.
Abstract: A mechanical model for the vertical response of the bolster and friction-wedge suspension elements in a railroad freight truck is developed. The model incorporates linear stiffnesses and dry friction contact between rigid elements. Numerical bifurcation diagrams for sticking events, obtained for parameterizations of the amplitude and frequency of a harmonic track excitation, and for various friction laws, reveal distinct parameter-dependent dynamic responses: strongly nonlinear stick-slip oscillations, observed away from period-1 resonance; and weakly nonlinear, nearly harmonic responses, observed near the period-one resonance. The analytical method of harmonic balance is applied to develop a first order approximation for the period-1 response, and, as should be expected, is found to correspond well with the numerical results in the large amplitude limit and near the resonance location. Given that such weakly nonlinear, large amplitude, period-1 responses are not common for the speeds and system parameter...
TL;DR: In this paper, a numerical method to simulate vertical dynamic interaction between a moving train and a railway track was extended to account for stochastic properties in the track structure, which is carried out in the time-domain with a moving mass model.
Abstract: A numerical method to simulate vertical dynamic interaction between a moving train and a railway track was extended to account for stochastic properties in the track structure. The numerical simulations are carried out in the time-domain with a moving mass model. Full-scale measurements in the field and laboratory experiments were carried out to obtain data for the stochastic track model. The values of the stochastic variables are thus chosen to correspond to real tracks. To investigate the influence of the randomness of selected stochastic parameters in the track structure, the Latin Hypercube sampling method with correlation control was used to generate stochastic realisations.
TL;DR: In this paper, a test-rig for measuring the inertia tensor of a vehicle is presented, which is basically a three or four bar pendulum hanging from the ceiling and carrying, by means of a rigid frame the rigid body under investigation.
Abstract: SUMMARYA new method for measuring the inertia tensor of rigid bodies has been developed and used for vehicle system dynamics applications.In the first part of the paper a brief state-of-the-art is presented referring to methods for measuring the inertia tensor of vehicles (or other rigid bodies). A number of test-rigs (presented in the literature) are classified and compared.In the second part of the paper a new test-rig, studied and built at the Politecnico di Milano, is introduced. The test-rig allows to measure the inertia tensor of vehicles (of mass up to 3500 kg, or more, after a proper adjustment). The rig is basically a three or four bar pendulum hanging from the ceiling and carrying, by means of a rigid frame the rigid body under investigation, e.g. a full road vehicle. The motion of the hanging vehicle is recorded by means of accelerometers, gyroscopes and inclinometers. The recorded data are numerically processed in order to indentify the full inertia tensor of the vehicle body. The paper presen...
TL;DR: In this paper, the authors investigated the physical characteristics of automatic steering controller using steering angle and steering torque as the control input, and compared their differences and found that the steering torque control provides some degree of freedom in permitting the driver to steer the vehicle, thus it has potential for development as a steering assist mechanism.
Abstract: SUMMARYAlternative methods of automatic steering system are investigated by using a vehicle-mounted camera that detects lane markers ahead of the vehicle. The control input of such a steering system can be classified into steering angle and steering torque. This paper investigates the physical characteristics of automatic lane-tracking controller using steering angle and steering torque as the control input, and compares their differences. Generally, most of researches about lane-tracking control manoeuvre deal with steering angle control method due to its excellent robustness. In contrast, the steering torque control provides some degree of freedom in permitting the driver to steer the vehicle, thus it has potential for development as a steering assist mechanism. In this paper, the controller design is Linear Quadratic (LQ) controller based on the simplified dynamics of a 2 degree-of-freedom bicycle model and simplified steering model.
TL;DR: In this article, a relatively simple tilt control system using a gyroscope to provide a tilt control moment is shown capable of stabilizing the vehicle at still stand or at speed on a very low traction surface.
Abstract: Fully enclosed motorcycles could form the basis for extremely fuel and space efficient vehicles, but their inherent instability upon encountering even a momentary loss of traction renders them unsuitable for general use. It will be shown that a relatively simple tilt control system using a gyroscope to provide a tilt control moment is capable of stabilizing the vehicle at still stand or at speed on a very low traction surface. Furthermore, the system can achieve a coordinated turn on high traction surfaces. Since the gyro is an energy storage device, it can be used also in a hybrid system to provide extra power for acceleration and to recover some energy during braking. This relatively old idea should be reconsidered in light of the improved electromechanical devices, which have been developed recently for hybrid electric vehicles.
TL;DR: In this paper, a numerical method to simulate vertical dynamic interaction between a rolling train and a railway track has been used to investigate the influence of stochastic properties of the track structure.
Abstract: A numerical method to simulate vertical dynamic interaction between a rolling train and a railway track has been used to investigate the influence of stochastic properties of the track structure. A perturbation technique has been used to investigate the influence of the scatter in selected track properties. The train-track interaction problem has been numerically solved by use of an extended state-space vector approach in conjunction with a complex modal superposition for the whole track structure. All numerical simulations have been carried out in the time-domain with a moving mass model. Properties such as rail pad stiffness, ballast stiffness, dynamic ballast-subgrade mass and sleeper spacing have been studied. To obtain sufficient statistical information from track structures, full-scale measurements in the field and laboratory measurements have been carried out. The influence of scatter in the track properties on the maximum contact force between the rail and the wheel, the maximum magnitude of the v...
TL;DR: In this article, a mathematical model of track-wheel-terrain interaction is presented that supports the dynamic simulation of tracked vehicles, which takes the form of a two-point nonlinear boundary value problem that accounts for tension variations along the track.
Abstract: A mathematical model of track-wheel-terrain interaction is presented that supports the dynamic simulation of tracked vehicles. This model combines approximate and known constitutive laws for terrain response with a new representation for the track segment. The resulting track-wheel-terrain model allows the computation of the track tension and the normal and shear forces at the track-terrain interface as the track negotiates terrain of arbitrary profile. A key feature of this model is the uniform treatment of contact between the track and the roadwheels and the track and the terrain. Treating both contact problems in the same manner significantly simplifies the problem formulation and also reduces difficulties in computing points of track-wheel and track-terrain separation. The model takes the form of a two-point nonlinear boundary value problem that accounts for tension variations along the track (due to the non-uniformly distributed normal pressure and traction), track extensibility, and geometrically la...