Showing papers in "Vehicle System Dynamics in 2006"
TL;DR: In this paper, the dual extended Kalman filter (DEKF) technique is used for combined estimation of vehicle states and parameters, which can be used to switch off the parameter estimator, once a sufficiently good set of estimates has been obtained.
Abstract: The article demonstrates the implementation of a model-based vehicle estimator, which can be used for combined estimation of vehicle states and parameters. The estimator is realised using the dual extended Kalman filter (DEKF) technique, which makes use of two Kalman filters running in parallel, thus ‘splitting’ the state and parameter estimation problems. Note that the two problems cannot be entirely separated due to their inherent interdependencies. This technique provides several advantages, such as the possibility to switch off the parameter estimator, once a sufficiently good set of estimates has been obtained. The estimator is based on a four-wheel vehicle model with four degrees of freedom, which accommodates the dominant modes only, and is designed to make use of several interchangeable tyre models. The paper demonstrates the appropriateness of the DEKF. Results to date indicate that this is an effective approach, which is considered to be of potential benefit to the automotive industry.
338 citations
TL;DR: With vehicle hardware-in-the-loop (VEHIL) simulations, the development process, and more specifically the validation phase, of intelligent vehicles is carried out safer, cheaper, and is more manageable.
Abstract: This paper presents a new method for the design and validation of advanced driver assistance systems (ADASs). With vehicle hardware-in-the-loop (VEHIL) simulations, the development process, and more specifically the validation phase, of intelligent vehicles is carried out safer, cheaper, and is more manageable. In the VEHIL laboratory, a full-scale ADAS-equipped vehicle is set up in a hardware-in-the-loop simulation environment, where a chassis dynamometer is used to emulate the road interaction and robot vehicles to represent other traffic. In this controlled environment, the performance and dependability of an ADAS is tested to great accuracy and reliability. The working principle and the added value of VEHIL are demonstrated with test results of an adaptive cruise control and a forward collision warning system. On the basis of the 'V' diagram, the position of VEHIL in the development process of ADASs is illustrated.
292 citations
TL;DR: In this article, a vehicle dynamics integrated control algorithm using an on-line non-linear optimization method is proposed for 4-wheel-distributed steering and 4wheeldistributed traction/braking systems.
Abstract: In this article, vehicle dynamics integrated control algorithm using an on-line non-linear optimization method is proposed for 4-wheel-distributed steering and 4-wheel-distributed traction/braking systems. The proposed distribution algorithm minimizes work load of each tire, which is controlled to become the same value. The global optimality of the convergent solution of the recursive algorithm can be proved by extension to convex problems. This implies that theoretical limited performance of vehicle dynamics integrated control is clarified. Furthermore, the effect of this vehicle dynamics control for the 4-wheel-distributed steering and 4-wheel-distributed traction/braking systems is demonstrated by simulation to compare with the combination of the various actuators.
223 citations
TL;DR: In this article, the authors derived optimal linear preview controllers using the two approaches starting from a common state-space description of the vehicle dynamics, and the transformation of the controllers from ground-fixed axes to vehicle-fixed axis is discussed.
Abstract: A brief review of the literature reveals that both predictive control theory and linear quadratic (LQ) control theory have been used to design path-following controllers with preview, but it is not clear how the controllers compare. This article derives optimal linear preview controllers using the two approaches starting from a common state-space description of the vehicle dynamics. The transformation of the controllers from ground-fixed axes to vehicle-fixed axes is discussed. The influences of preview horizon, control horizon and cost function are investigated. For the case of long preview and long control horizons, it is found that the predictive and LQ approaches give identical controllers. The results in this article provide a basis for identifying human steering behaviour from measured data.
178 citations
TL;DR: In this article, train-track interaction is more complex in railway turnouts (switches and crossings) than that in ordinary tangent or curved tracks, and multiple contacts between wheel and rail are common.
Abstract: Dynamic train–track interaction is more complex in railway turnouts (switches and crossings) than that in ordinary tangent or curved tracks. Multiple contacts between wheel and rail are common, and ...
145 citations
TL;DR: In this article, a vehicle model of a typical sports sedan was developed in Simulink, with fully independent control of torque distribution, and a proportional-integral control strategy was implemented, applying yaw rate feedback to vary the front-rear torque distribution and lateral acceleration feedback to adjust the left-right distribution.
Abstract: The sophistication of all-wheel-drive (AWD) technology is approaching the point where the drive torque to each wheel can be independently controlled. This potentially offers vehicle handling enhancements similar to those provided by dynamic stability control, but without the inevitable reduction in vehicle acceleration. Independent control of AWD torque distribution would therefore be especially beneficial under acceleration close to the limit of stability. A vehicle model of a typical sports sedan was developed in Simulink, with fully independent control of torque distribution. Box–Behnken experimental design was employed to determine which torque distribution parameters have the greatest impact on the vehicle course and acceleration. A proportional-integral control strategy was implemented, applying yaw rate feedback to vary the front–rear torque distribution and lateral acceleration feedback to adjust the left–right distribution. The resulting system shows a significant improvement over conventional dr...
124 citations
TL;DR: In this article, the authors used a capacitative strip sensor for measuring dynamic type forces and measured the contact area shape and dimensions as well as the longitudinal, lateral and vertical loads.
Abstract: Huge improvements and advances in sensor technology, together with the increasing demand for safety and handling performances, pull research towards new control strategies. Robustness and promptness of sensors used for active control are key requisites. The main idea behind the research presented in this paper is to instrument the tire with appropriate sensors in order to estimate several contact parameters ranging from the kinematic conditions of the tire (the longitudinal slippage and the side slip angle [Fukada, Y., 1999, Slip-angle estimation for vehicle stability control. Vehicle System Dynamics, 32(4–5), 375–388.]) to its dynamic properties (the contact area shape and dimensions as well as the longitudinal, lateral and vertical loads [Cole, D.J. and Cebon, D., 1989, A capacitative strip sensor for measuring dynamic type forces. Proc. of the Second International Conference on Road Traffic Monitoring, London, 38–42; Cole, D.J. and Cebon, D., 1992, Performance and application of a capacitative strip ty...
118 citations
TL;DR: In this paper, both time-domain and frequency-domain-based methods are analyzed to estimate the effective cornering stiffness, defined as the ratio between the lateral force and the slip angle at the two axles.
Abstract: In this article, the cornering stiffness estimation problem based on the vehicle bicycle (one-track) model is studied. Both time-domain and frequency-domain-based methods are analyzed, aiming to estimate the effective cornering stiffness, defined as the ratio between the lateral force and the slip angle at the two axles. Several methods based on the bicycle model were developed, each having specific pros/cons related to practical implementations. The developed algorithms were evaluated on the basis of the simulation data from the bicycle model and the CarSimTM software. Finally, selected algorithms were evaluated using experimental data.
115 citations
TL;DR: In this article, a new method based on sliding mode observers has been developed and is compared with two inertial methods, and experimental results are shown and discussed to evaluate the robustness of the approach.
Abstract: Vehicle motion simulation accuracy, such as in accident reconstruction or vehicle controllability analysis on real roads, can be obtained only if valid road profile and tire–road friction models are available. Regarding road profiles, a new method based on sliding mode observers has been developed and is compared with two inertial methods. Experimental results are shown and discussed to evaluate the robustness of our approach.
100 citations
TL;DR: In this paper, a dynamic analysis method for a pantograph-catenary system for a high-speed train is presented, employing absolute nodal coordinates and rigid body reference coordinates, and the analysis results are compared with experimental data obtained from a running high speed train.
Abstract: The dynamic interaction between the catenary and the pantographs of high-speed trains is a very important factor that affects the stable electric power supply. In order to design a reliable current collection system, a multibody simulation model can provide an efficient and economical method to analyze the dynamic behavior of the catenary and pantograph. In this article, a dynamic analysis method for a pantograph–catenary system for a high-speed train is presented, employing absolute nodal coordinates and rigid body reference coordinates. The highly flexible catenary is modeled using a nonlinear continuous beam element, which is based on an absolute nodal coordinate formulation. The pantograph is modeled as a rigid multibody system. The analysis results are compared with experimental data obtained from a running high-speed train. In addition, using a derived system equation of motion, the calculation method for the dynamic stress in the catenary conductor is presented. This study may have significance in ...
98 citations
TL;DR: A new class of five-phase anti-lock brake algorithms that use wheel deceleration logic-based switching and a simple mathematical background that explains their behavior are provided and an approximation of the Poincaré map of the system is computed.
Abstract: The aim of our paper is to provide a new class of five-phase anti-lock brake algorithms (that use wheel deceleration logic-based switching) and a simple mathematical background that explains their behavior. First, we completely characterize the conditions required for our algorithm to work. Next, we explain how to compute analytically an approximation of the Poincare map of the system (without using numerical integration) and show how to calibrate the algorithm's parameters to obtain the most efficient limit cycle.
TL;DR: In this paper, the authors present the results of an experimental and numerical investigation on the derailment of a railway wheelset with solid axle, under quasi-steady state conditions, on a full-scale roller rig, and allowed to point out the effect of different parameters like the wheelset's angle of attack and the ratio between the vertical loads acting on the flanging and non-flanging wheels.
Abstract: This paper presents the results of an experimental and numerical investigation on the derailment of a railway wheelset with solid axle. Tests were carried out under quasi-steady-state conditions, on a full-scale roller rig, and allowed to point out the effect of different parameters like the wheelset's angle of attack and the ratio between the vertical loads acting on the flanging and non-flanging wheels. On the basis of the test results, some existing derailment criteria are analysed in this paper and two new criteria are proposed. A model of wheel–rail contact is proposed for the mathematical modelling of the flange climb process, and numerical vs. experimental comparisons are used to obtain model validation.
TL;DR: In this article, a validation of the STRIPES method for normal problem computing on three test cases is proposed in which the test cases do not fulfill the hypothesis required for the Hertz theory.
Abstract: Wheel–rail contact calculations are essential for simulating railway vehicle dynamic behavior. Currently, these simulations usually use the Hertz contact theory to calculate normal forces and Kalker's ‘FASTSIM’ program to evaluate tangential stresses. Since 1996, new methods called semi-Hertzian have appeared: 5 7 (STRIPES). These methods attempt to estimate the non-elliptical contact patches with a discrete extension of the Hertz theory. As a continuation of 2, a validation of the STRIPES method for normal problem computing on three test cases is proposed in this article. The test cases do not fulfill the hypothesis required for the Hertz theory. Then, the Kalker's FASTSIM algorithm is adapted to STRIPES patch calculus to perform tangential forces computation. This adaptation is assessed using Kalker's CONTACT algorithm.
TL;DR: In this paper, a dynamic sliding surface design combined with recursive backstepping algorithm is introduced to solve a physical problem about the minimal excitation of the slosh dynamics associated with the longitudinal and lateral excitations of the vehicle.
Abstract: Control and handling of heavy commercial vehicles carrying liquid cargo are influenced by liquid movement within the partially filled tank. During steering and braking maneuvering tasks, the truck may exhibit unstable behavior at lateral acceleration levels of 0.3 g to 0.4 g [m/s2]. The fluid slosh forces and dynamic load transfers in the lateral and longitudinal directions and parametric uncertainties caused by moving liquid cargo affect the overall dynamics of the vehicle. To solve a physical problem about the minimal excitation of the slosh dynamics associated with the longitudinal and lateral excitation of the vehicle, dynamic sliding surface design combined with recursive backstepping algorithm is introduced. Compensator dynamics are introduced in the sliding mode through a class of switching surfaces which has the interpretation of linear operators such that the resulting closed-loop system retains the insensitivity to uncertainties in the sliding mode while minimizing the excitation of flexible mod...
TL;DR: In this paper, an adaptive sliding controller is proposed to control the active suspension systems of a quarter-car model with hydraulic actuator, where the highly nonlinear actuator dynamics is assumed to have some time-varying uncertainties with unknown bounds.
Abstract: An adaptive sliding controller is proposed in this article to control the active suspension systems of a quarter-car model with hydraulic actuator. The highly nonlinear actuator dynamics is assumed to have some time-varying uncertainties with unknown bounds. Owing to its time-variant nature, traditional adaptive designs are not feasible. As the variation bounds are not given, the conventional robust controllers cannot be applied either. In this article, we use the function approximation technique to represent the uncertainties with finite combinations of some basis functions, and the Lyapunov method is employed to find update laws for the coefficients of the approximating series. The actuator force can track the desired force generated from the skyhook dynamics with ultimately bounded performance. If a sufficient number of basis functions are used and the approximation error can be ignored, asymptotic convergence performance can be proved. If the bound of the approximation error is available, asymptotic c...
TL;DR: In this paper, a mathematical model of the driver's muscle reflex system suggests that co-contraction may be an optimal control strategy despite the extra energy required, which increases the limb stiffness and thus the bandwidth of the control loop, which in turn allows smaller path-following errors.
Abstract: The work described in this article is part of a larger programme of research to understand the dynamic interaction between driver and vehicle. The driver's neuromuscular dynamics are thought to be an important aspect of the interaction. Measurements of muscle activation voltage (electromyography, EMG) are used to identify the muscles involved in generating torque at the steering wheel. The EMG instrumentation is then developed to measure muscle co-contraction. In a lane-change manoeuvre performed on a driving simulator, muscle co-contraction is observed to occur during the manoeuvre. A mathematical model of the driver's muscle reflex system suggests that co-contraction may be an optimal control strategy despite the extra energy required. The co-contraction increases the limb stiffness and thus the bandwidth of the control loop, which in turn allows smaller path-following errors.
TL;DR: In this article, a multi-purpose platform for HIL testing of safety relevant railway subsystems, such as odometry boards or wheel slide protection systems, is shown, which is a product of the cooperation of Trenitalia with researchers of Dip. Energetica Sergio Stecco (University of Florence).
Abstract: In this article, a multi-purpose platform for Hardware In the Loop (HIL) testing of safety relevant railway subsystems, such as odometry boards or wheel slide protection systems, is shown. The rig, called MI-6, is a product of the cooperation of Trenitalia with researchers of Dip. Energetica Sergio Stecco (University of Florence). In this work, special attention has been paid to vehicle real-time model optimization according to customer specifications (Trenitalia) and to simulate artificially degraded adhesion between rolling surfaces where conventional adhesion models have poor performances or require unaffordable computational resources for real-time applications. In this article, a heuristic model based on energetic considerations and a wide archive of experimental test (courtesy of Trenitalia Societa per Azioni) is presented. Also some simulation results and comparison with the experimental data are shown.
TL;DR: In this article, a numerical analysis of high-frequency dynamic train-track interaction is combined with the analysis of material deterioration in terms of rolling contact fatigue (RCF) and plastic deformations to analyze the influence of insulated rail joints.
Abstract: Numerical analysis of high-frequency dynamic train-track interaction is combined with the analysis of material deterioration in terms of rolling contact fatigue (RCF) and plastic deformations to analyze the influence of insulated rail joints. These joints form local rail irregularities and lead to a local change of dynamic track stiffness. Dynamic responses at wheel passes are evaluated. Further, related plastic deformations at the joint and increased RCF impact along a stretch of the track adjacent to the joint are predicted.
TL;DR: In this paper, the effects of the wheelset structural flexibility and track flexibility on the wheel-rail forces are investigated in the frequency range 0-150 Hz and the influence of track modelling and pertinent data on the simulation results is particularly assessed through a set of moving track models.
Abstract: Vehicle-track dynamic interaction emerged as a key multi-aspect subject following the development in high-speed and high axle-load trains. In this context, wheelset structural flexibility and track flexibility are the two main factors that contribute to high frequency content of the wheel-rail forces and influence the vehicle-track damage. Appropriate wheelset and track flexibility models are hence of great importance in pertinent numerical simulations. The present study comprises vehicle-track dynamic simulations considering wheelset structural flexibility and advanced moving track models. Simulated wheel-rail forces are then validated against measured data. The effects of the wheelset structural flexibility and track flexibility on the wheel-rail forces are investigated in the frequency range 0-150 Hz. The influence of track modelling and pertinent data on the simulation results is particularly assessed through a set of moving track models. Measured track data, i.e. irregularities, roughness and flexibility support the simulations. It is confirmed that track flexibility with appropriate modelling and data is important when examining the vehicle-track interaction. In the present case study, the influence of wheelset structural flexibility on the lateral wheel-rail forces is quite significant too.
TL;DR: In this article, the available degrees of freedom are used to execute the desired vehicle motion while minimizing the utilization of the tyre's grip potential, which is done by sampled constrained least squares optimization of the linearized problem.
Abstract: This work proposes to approach global chassis control (GCC) by means of model inversion-based feedforward with allocation directly on the actuator commands. The available degrees of freedom are used to execute the desired vehicle motion while minimizing the utilization of the tyre’s grip potential. This is done by sampled constrained least-squares optimization of the linearized problem. To compensate for model errors and external disturbances, high-gain feedback is applied by means of an inverse disturbance observer. The presented method is applied in a comparison of eight vehicles with different actuator configurations for steer, drive, brake and load distribution. The approach shows a transparent and effective method to deal with the complex issue of GCC in a unitized way. It gives both a base for controller design and a structured way to compare different configurations. In practice, the transparency supports automatic on-board reconfiguration in the case of actuator hardware failure.
TL;DR: In this paper, an electro-mechanical actuator was used to improve the running behavior of a railway vehicle, both in straight track and curve negotiation, in order to increase the vehicle critical speed and reduce the maximum values of track shift forces.
Abstract: To further increase passenger train comfort and handling performances, a mechatronic approach to the design of railway vehicles is necessary In fact, active systems on board a railway vehicle allow to push design barriers beyond those encountered with just passive systems The article deals with the development of an electro-mechanical actuator to improve the running behaviour of a railway vehicle, both in straight track and curve The main components of the active system are a brushless motor and a mechanical transmission, used to apply a longitudinal force between the carbody and the bogie of the vehicle The actuator is operated in force control Different control strategies were developed for straight track running, where the aim is to increase the vehicle critical speed, and for curve negotiation, where the goal is to reduce the maximum values of track shift forces A mathematical model of the railway vehicle incorporating the active control device has been developed and used to optimise control str
TL;DR: In this article, an analytical method to investigate the 3D flexural vibration of railway vehicle car bodies is presented, where a car body is modeled as a box-type structure consisting of plates and beams.
Abstract: An analytical method to investigate the three-dimensional (3D) flexural vibration of railway vehicle car bodies is presented in this article. In the method, a car body is modeled as a box-type structure consisting of plates and beams. The condition to connect components is satisfied by introducing artificial springs at their joints. The detailed analytical procedure is described. Some numerical calculations are carried out employing a commuter vehicle, which has a stainless steel car body, as an example. The numerical results are compared with the measured data to evaluate the validity of the model. Although the target vehicle has complicated mode shapes, it is shown that the analytical model can express such 3D vibration mode shapes successfully. It is also demonstrated that a good agreement is observed between the calculation results by the above method and the measured data for both stationary excitation and running test.
TL;DR: In this article, the influence of the aerodynamic action on a pantograph, due to the incoming flow generated by train speed, is investigated considering pantograph-catenary dynamic interaction.
Abstract: Some aspects about the influence on the current collection of the aerodynamic action on a pantograph, due to the incoming flow generated by train speed are investigated considering pantograph–catenary dynamic interaction. Starting from the quasi-steady theory formulation of the drag and lift forces on the collectors, and considering the turbulence of the incoming flow, the dynamic variation of the contact force between pantograph and catenary is taken into account, within an already developed simulation model. Aerodynamic coefficients of the collectors are obtained from wind tunnel measurements, and the aerodynamic forces are applied to the collectors of the pantograph. The interrelation among the geometry of the collector suspension, the collector shape, and the level of the incoming wind turbulence, and their effect on the contact force, are all considered in this article by means of numerical simulation. Results concerning the advantage of modifying the shape of the collector are outlined.
TL;DR: In this paper, the authors developed a transmission ratio controller for a hydraulically actuated metal push-belt continuously variable transmission (CVT), using models for the mechanical and the hydraulic part of the CVT.
Abstract: Vehicular drivelines with hierarchical powertrain control require good component controller tracking, enabling the main controller to reach the desired goals. This paper focuses on the development of a transmission ratio controller for a hydraulically actuated metal push-belt continuously variable transmission (CVT), using models for the mechanical and the hydraulic part of the CVT. The controller consists of an anti-windup PID feedback part with linearizing weighting and a setpoint feedforward. Physical constraints on the system, especially with respect to the hydraulic pressures, are accounted for using a feedforward part to eliminate their undesired effects on the ratio. The total ratio controller guarantees that one clamping pressure setpoint is minimal, avoiding belt slip, while the other is raised above the minimum level to enable shifting. This approach has potential for improving the efficiency of the CVT, compared to non-model based ratio controllers. Vehicle experiments show that adequate tracking is obtained together with good robustness against actuator saturation. The largest deviations from the ratio setpoint are caused by actuator pressure saturation. It is further revealed that all feedforward and compensator terms in the controller have a beneficial effect on minimizing the tracking error.
TL;DR: In this paper, the adaptation of steer-by-wire (SBW) parameters to the driver's steer characteristics for a vehicle equipped with a SBW system whereby steering gain and derivative time constant between the steering-wheel angle and the front-wheel-steer angle can be freely set.
Abstract: This study focuses on the adaptation of steer-by-wire (SBW) parameters to the driver's steer characteristics for a vehicle equipped with SBW system whereby steering gain and derivative time constant between the steering-wheel angle and the front-wheel-steer angle can be freely set. First of all, it presents a simple yet effective method to estimate the driver's steer parameters from experimental data based on the general driver's model. Driver's parameters for young and aged drivers are compared. SBW parameters are then adapted to the identified driver's parameters based on a simple analytical method, and its effect on the driver-vehicle system performance improvement is examined through an experimental study, for the case of aged drivers.
TL;DR: In this article, the authors proposed an alternative lane keeping control strategy with direct yaw moment control (DYC) that utilizes the transverse driving torque distribution, which can be easily and precisely achieved by controlling the in-wheel-motors independently.
Abstract: This article presents the alternative lane keeping control strategy with direct yaw moment control (DYC) that utilizes the transverse driving torque distribution. With the sophisticated structure of today's electric vehicle, the small-size motor can be placed into each driving wheel so that the DYC input can be easily and precisely achieved by controlling the in-wheel-motors independently. The information of road position is acquired by vision system via CCD camera and on-board image processing system. As a feature of the proposed system, the lateral deviation detected by CCD camera is converted into the desired yaw rate for tracing the desired lane. Then, the yaw moment control input is theoretically determined to achieve the desired yaw rate from the viewpoint of vehicle dynamics. This article presents the theoretical analysis of lane keeping control characteristics using linear vehicle model on planar motion, and experimental study using micro-scale electric vehicle to verify the effectiveness of the proposed strategy.
TL;DR: In this article, the authors studied the comfort of two-wheeled vehicles by means of a frequency-domain approach, which takes place because the same road unevenness excites the front and rear wheel with a time delay which depends on the vehicle's speed.
Abstract: In many European towns, the demand for fast and efficient mobility is frequently satisfied by means of two-wheeled vehicles. The improvement of comfort of two-wheeled vehicles used by tired and busy workers can increase safety in ground transport. Nowadays, multibody codes make it possible to predict the ride comfort of two-wheeled vehicles by means of time-domain or frequency-domain simulations. Comfort indices can be developed by post-processing the results of numerical simulations. This task is difficult, because the indices should depend on vehicle characteristics and should be independent of road quality and vehicle speed. Poor quality roads may generate nonlinear effects. Speed influences the trim of the vehicle and the wheelbase filtering, which takes place because the same road unevenness excites the front and rear wheel with a time delay which depends on the vehicle’s speed. In this paper, the comfort of two-wheeled vehicles is studied by means of a frequency-domain approach. The wheelbase filter...
TL;DR: In this article, the authors extended linear preview control theory to the steering of a car by a driver and extended it to the domain of the motorcycle. But the focus was not on the steering, but on minimizing a weighted sum of path-tracking errors.
Abstract: Prior research into the application of optimal linear preview control theory to the steering of a car by a driver is extended into the domain of the motorcycle. The simple car model employed previously is replaced by a much more elaborate motorcycle model, and the control mode is changed from a fixed control for the car to a free control for the motorcycle. Handlebar torque is always the main control input but, in some cases, the rider's upper body lean torque is also included as a control. The machine speed is considered to be constant. The objective of the optimal control is to minimize a weighted sum of path-tracking errors and control power. The time-invariant control corresponding to an infinite optimization horizon and a white noise disturbance is found for each of several cases, involving variations in machine speed and performance priorities. Results demonstrate the relatively minor role of body lean torque control and the strong relationship between the optimal tracking steering control and the m...
TL;DR: In this article, a method of estimating the longitudinal and lateral grips for use within a control system is proposed, and tested using logged data from a test vehicle, and the force estimates are validated against results from strain-gauged wheel rims.
Abstract: Control systems designed to optimize vehicle performance, such as antilock braking systems or traction control systems, depend upon a knowledge of the amount of available grip at the tyre–road contact point. There have been both qualitative and quantitative approaches to identify the road surface coefficient of friction, μ. This work proposes a method of estimating the longitudinal and lateral grips for use within a control system. The estimation method is explained and the vehicle model equations used are stated. The estimator is then tested using logged data from a test vehicle, and the force estimates are validated against results from strain-gauged wheel rims. Finally, the direction of future work is described.
TL;DR: In this paper, a classification of wheel-rail contact is given, and an analytical closed-form solution is found in the frequency domain for arbitrary type of contact and numerically transformed to the time domain.
Abstract: A classification of wheel–rail contact is given. Difference is made between modelling of a running wheel with continuous single-point-contact, as is common practice in wheel–rail contact analysis, and a wheel with transient double- or multi-point-contact, which may occur for rail irregularities with curvatures larger than that of the wheel circumference. It is shown that application of the first model for these irregularities will strongly underestimate the contact forces as it does not describe occurring mechanisms correctly. Further, it is shown that in principle it is not possible to describe the second type of contact fully correct with a lumped wheel model. Both wheel models are formulated mathematically for some basic contact cases. Afterwards, results are applied to a linear track model. Analytical closed-form solutions are found in the frequency domain for arbitrary type of contact and numerically transformed to the time domain. Finally, the necessity is shown to avoid situations where transient m...