Showing papers in "Vehicle System Dynamics in 2010"
TL;DR: In this paper, the authors summarize the development and research achievements of the first generation of adaptive cruise control (ACC)-equipped vehicles in order to provide more useful experiential guidance for the new deployment.
Abstract: It has been 15 years since the first generation of adaptive cruise control (ACC)-equipped vehicles was available on the market and 7 years since the ISO standard for the first generation of ACC systems was produced. Since the next generation of ACC systems and more advanced driver-assistant systems are at the verge of complete introduction and deployment, it is necessary to summarise the development and research achievements of the first generation of ACC systems in order to provide more useful experiential guidance for the new deployment. From multidimensional perspectives, this paper looks into the related development and research achievements to objectively and comprehensively introduce an ACC system to researchers, automakers, governments and consumers. It attempts to simply explain what an ACC system is and how it operates from a systematic perspective. Then, it clearly draws a broad historical picture of ACC development by splitting the entire history into three different phases. Finally, the most significant research findings-related ACC systems have been reviewed and summarised from the human, traffic and social perspectives respectively.
271 citations
TL;DR: In this paper, the authors describe extensions to the widely used TNO MF-Tyre 5.2 Magic Formula tyre model to cope with large camber angles and inflation pressure changes.
Abstract: This paper describes extensions to the widely used TNO MF-Tyre 5.2 Magic Formula tyre model. The Magic Formula itself has been adapted to cope with large camber angles and inflation pressure changes. In addition, the description of the rolling resistance has been improved. Modelling of the tyre dynamics has been changed to allow a seamless and consistent switch from simple first-order relaxation behaviour to rigid ring dynamics. Finally, the effect of inflation pressure on the loaded radius and the tyre enveloping properties is discussed and some results are given to illustrate the capabilities of the model.
107 citations
TL;DR: In this article, the authors presented an approach for the frequency domain analysis of a vehicle fitted with a general hydraulically interconnected suspension (HIS) system, in which the relationship between the dynamic fluid states, i.e. pressures and flows, at the extremities of a single fluid circuit were determined by the transfer matrix method.
Abstract: This paper presents a novel approach for the frequency domain analysis of a vehicle fitted with a general hydraulically interconnected suspension (HIS) system. Ideally, interconnected suspensions have the capability, unique among passive systems, to provide stiffness and damping characteristics dependent on the all-wheel suspension mode in operation. A basic, lumped-mass, four-degree-of-freedom half-car model is used to illustrate the proposed methodology. The mechanical–fluid boundary condition in the double-acting cylinders is modelled as an external force on the mechanical system and a moving boundary on the fluid system. The fluid system itself is modelled using the hydraulic impedance method, in which the relationships between the dynamic fluid states, i.e. pressures and flows, at the extremities of a single fluid circuit are determined by the transfer matrix method. A set of coupled, frequency-dependent equations, which govern the dynamics of the integrated half-car system, are then derived and the ...
105 citations
TL;DR: In this article, a new estimation process for tyre/road forces is introduced, which presents many benefits over the existing state-of-the-art works, within the dynamic estimation framework.
Abstract: The motion of a vehicle is governed by the forces generated between the tyres and the road. Knowledge of these vehicle dynamic variables is important for vehicle control systems that aim to enhance vehicle stability and passenger safety. This study introduces a new estimation process for tyre/road forces. It presents many benefits over the existing state-of-art works, within the dynamic estimation framework. One of these major contributions consists of discussing in detail the vertical and lateral tyre forces at each tyre. The proposed method is based on the dynamic response of a vehicle instrumented with potentially integrated sensors. The estimation process is separated into two principal blocks. The role of the first block is to estimate vertical tyre forces, whereas in the second block two observers are proposed and compared for the estimation of lateral tyre/road forces. The different observers are based on a prediction/estimation Kalman filter. The performance of this concept is tested and compared with real experimental data using a laboratory car. Experimental results show that the proposed approach is a promising technique to provide accurate estimation. Thus, it can be considered as a practical low-cost solution for calculating vertical and lateral tyre/road forces.
103 citations
TL;DR: In this article, an adaptive integrated control algorithm based on active front steering and direct yaw moment control using direct Lyapunov method is proposed to ensure robustness of the integrated controller.
Abstract: In this article, an adaptive integrated control algorithm based on active front steering and direct yaw moment control using direct Lyapunov method is proposed. Variation of cornering stiffness is considered through adaptation laws in the algorithm to ensure robustness of the integrated controller. A simple two degrees of freedom (DOF) vehicle model is used to develop the control algorithm. To evaluate the control algorithm developed here, a nonlinear eight-DOF vehicle model along with a combined-slip tyre model and a single-point preview driver model are used. Control commands are executed through correction steering angle on front wheels and braking torque applied on one of the four wheels. Simulation of a double lane change manoeuvre using Matlab®/Simulink is used for evaluation of the control algorithm. Simulation results show that the integrated control algorithm can significantly enhance vehicle stability during emergency evasive manoeuvres on various road conditions ranging from dry asphalt to very slippery packed snow road surfaces.
99 citations
TL;DR: In this paper, the authors present a design process that enables systematic search and screening through all three major dimensions of hybrid vehicle designs, including system configuration, component sizing and control, to achieve optimal performance while satisfying the imposed constraints.
Abstract: Multiple power sources in a hybrid vehicle allow for flexible vehicle power-train operations, but also impose kinematic constraints due to component characteristics. This paper presents a design process that enables systematic search and screening through all three major dimensions of hybrid vehicle designs - system configuration, component sizing and control, to achieve optimal performance while satisfying the imposed constraints. An automated dynamic modelling method is first developed which enables the construction of hybrid vehicle model efficiently. A screening process then narrows down to configurations that satisfy drivability and operation constraints. Finally, a design and control optimisation strategy is carried out to obtain the best execution of each configuration. A case study for the design of a power-split hybrid vehicle with optimal fuel economy is used to demonstrate this overall hybrid vehicle design process.
94 citations
TL;DR: An errorable car-following driver model is presented that emulates human driver’s functions and can generate both nominal (error-free) and devious behaviours, as well as devious (with error) behaviours.
Abstract: An errorable car-following driver model is presented in this paper. An errorable driver model is one that emulates human driver’s functions and can generate both nominal (error-free), as well as devious (with error) behaviours. This model was developed for evaluation and design of active safety systems. The car-following data used for developing and validating the model were obtained from a large-scale naturalistic driving database. The stochastic car-following behaviour was first analysed and modelled as a random process. Three error-inducing behaviours were then introduced. First, human perceptual limitation was studied and implemented. Distraction due to non-driving tasks was then identified based on the statistical analysis of the driving data. Finally, time delay of human drivers was estimated through a recursive least-square identification process. By including these three error-inducing behaviours, rear-end collisions with the lead vehicle could occur. The simulated crash rate was found to be simil...
91 citations
TL;DR: In this article, the benefits of lateral stability of train suspension systems employing a newly developed mechanical network element known as an inerter were investigated, where an ideal mechanical two-port element was proposed to substitute for the mass element in the mechanical/electrical analogy.
Abstract: This paper investigates the benefits of lateral stability of train suspension systems employing a newly developed mechanical network element known as an inerter. An inerter was proposed as an ideal mechanical two-port element to substitute for the mass element in the mechanical/electrical analogy. As of now, inerters have been successfully applied to car and motorcycle suspension systems, for which significant performance benefits were reported. This paper discusses the improvements on lateral stability of train suspension systems employing inerters. The study was carried out in three parts. First, an existing 12 degrees-of-freedom (DOF) train model was built and verified by a multi-body-builder, AutoSimTM. Second, inerters were applied to the train suspension system to increase the critical speed. Finally, the discussion was extended to a 16-DOF model to demonstrate the performance improvement by inerters. From the results, inerters were deemed effective in improving the lateral stability of train suspen...
86 citations
TL;DR: In this paper, an analysis of the equilibria of a bicycle model with nonlinear tyres reveals the existence of unstable "drift equilibrium" corresponding to cornering at high sideslip angle in a countersteer configuration.
Abstract: This paper presents simple analytical techniques that are used to understand and control high sideslip drift manoeuvres of road vehicles. These are manoeuvres in which a skilled driver stabilises a vehicle beyond its limits of handling, an operating regime responsible for major safety concerns in everyday driving. An analysis of the equilibria of a bicycle model with nonlinear tyres reveals the existence of unstable 'drift equilibria' corresponding to cornering at high sideslip angle in a countersteer configuration. Equipped with this information, linearisation about a desired drift equilibrium is used to design a controller that stabilises the vehicle at the equilibrium. The controller is subsequently implemented on a steer- and drive-by-wire testbed and successfully used to achieve autonomous drifts.
82 citations
TL;DR: In this article, the authors investigated the fundamental issues related to feasibility and properties of the passive, full-vehicle interconnected, hydro-pneumatic suspension configurations using both analytical and simulation techniques.
Abstract: Passive fluidically coupled suspensions have been considered to offer a promising alternative solution to the challenging design of a vehicle suspension system. A theoretical foundation, however, has not been established for fluidically coupled suspension to facilitate its broad applications to various vehicles. The first part of this study investigates the fundamental issues related to feasibility and properties of the passive, full-vehicle interconnected, hydro-pneumatic suspension configurations using both analytical and simulation techniques. Layouts of various interconnected suspension configurations are illustrated based on two novel hydro-pneumatic suspension strut designs, both of which provide a compact design with a considerably large effective working area. A simplified measure, vehicle property index, is proposed to permit a preliminary evaluation of different interconnected suspension configurations using qualitative scaling of the bounce-, roll-, pitch- and warp-mode stiffness properties. Analytical formulations for the properties of unconnected and three selected X-coupled suspension configurations are derived, and simulation results are obtained to illustrate their relative stiffness and damping properties in the bounce, roll, pitch and warp modes. The superior design flexibility feature of the interconnected hydro-pneumatic suspension is also discussed through sensitivity analysis of a design parameter, namely the annular piston area of the strut. The results demonstrate that a full-vehicle interconnected hydro-pneumatic suspension could provide enhanced roll- and pitch-mode stiffness and damping, while retaining the soft bounce- and warp-mode properties. Such an interconnected suspension thus offers considerable potential in realising enhanced decoupling among the different suspension modes.
75 citations
TL;DR: The proposed approach to multi-objective H ∞/GH 2 preview control of active vehicle suspensions is evaluated on a quarter-car model and compared with the state-of-the-art preview control algorithm in the literature, namely, Linear quadratic Gaussian preview.
Abstract: This study concerns with multi-objective H ∞/GH 2 preview control of active vehicle suspensions. This control scheme has two main aspects: first, it allows constrained outputs of the system to vary freely as long as they remain within their given bounds, in order that the best possible performance could be delivered. Secondly, the optimisation as well as constraint fulfilment is done for the worst-case road disturbances to cover all road types. To design a system to perform satisfactorily for a wide range of road irregularities, H ∞-norm is used wherever minimisation is required, and generalised H 2-norm is used to care for the constraints on suspension working space. Moreover, to ensure desired stability margins for the system, pole location constraints are considered in the design. The proposed approach is evaluated on a quarter-car model and compared with the state-of-the-art preview control algorithm in the literature, namely, Linear quadratic Gaussian preview. Simulation results demonstrate the effec...
TL;DR: In this article, a multi-objective dimensional synthesis technique was used to optimize an RSSR-SS linkage subject to some constraints involved in the dynamic behavior of vehicles, such as equality and inequality constraints, thus, the usual ranges of values may be imposed on the functional parameters.
Abstract: This paper is focused on the kinematic design of double-wishbone suspension systems in vehicles, which is tackled using a multiobjective dimensional synthesis technique. The synthesis goal is to optimise an RSSR-SS linkage, subject to some constraints involved in the dynamic behaviour of vehicles. The synthesis method is based on gradient determination using exact differentiation to obtain the elements in the Jacobian matrix. These characteristics make the method adapt well to the optimum design of vehicle suspension systems. The method is capable of handling equality and inequality constraints, thus, the usual ranges of values may be imposed on the functional parameters. The formulation presented is easy to implement and the solutions obtained demonstrate the accuracy and robustness of the method.
TL;DR: In this paper, the influence of the contact nonlinearities on the behaviour of railway vehicles at the stability limit is investigated. And the authors present a description of wheel/rail contact geometry using two parameters and compare with the examples of wheelset/track pairs and the correlation between the proposed parameters and vehicle behaviour.
Abstract: The equivalent conicity is widely used to characterise the wheel/rail contact geometry; however, it does not consider the contact nonlinearity. There is a need for an improved but still simple description, which accounts for the most important effect of the contact nonlinearity on the running dynamics of railway vehicles. This article demonstrates the influence of the contact nonlinearities on the behaviour of railway vehicles at the stability limit and presents a description of wheel/rail contact geometry using two parameters. The proposed characteristic parameters are compared with the examples of wheelset/track pairs and the correlation between the proposed parameters and the vehicle behaviour presented.
TL;DR: In this paper, a model for three-dimensional, heavy vehicle-pavement-foundation coupled system is presented, which is modelled as a seven-DOF vehicle moving along a simply supported double-layer rectangular thin plate on a linear viscoelastic foundation.
Abstract: This paper presents a model for three-dimensional, heavy vehicle-pavement-foundation coupled system, which is modelled as a seven-DOF vehicle moving along a simply supported double-layer rectangular thin plate on a linear viscoelastic foundation. The vertical tyre force is described by a single point-contact model, while the pavement-foundation is modelled as a double-layer plate on a linear viscoelastic foundation. Using the Galerkin method and quick direct integral method, the dynamical behaviour of the vehicle-pavement-foundation coupled system is investigated numerically and compared with that of traditional vehicle system and pavement system. The effects of coupling action on vehicle body vertical acceleration, suspension deformations, tyre forces and pavement displacements are also obtained. The investigation shows that the coupling action could not be neglected even on a smooth road surface, such as highway. Thus, it is necessary to investigate the dynamics of vehicle and pavement simultaneously based on the vehicle-pavement-foundation coupled system.
TL;DR: In this article, a model for the frequency domain analysis of vehicles with hydraulically interconnected suspension (HIS) systems is applied to the ride analysis of a four-degrees of freedom roll-plane, half-car under a rough road input.
Abstract: In this paper, a previously derived model for the frequency-domain analysis of vehicles with hydraulically interconnected suspension (HIS) systems is applied to the ride analysis of a four-degrees of freedom roll-plane, half-car under a rough road input. The entire road surface is assumed to be a realisation of a two-dimensional Gaussian homogenous and isotropic random process. The frequency responses of the half-car, in terms of bounce and roll acceleration, suspension deflection and dynamic tyre forces, are obtained under the road input of a single profile represented by its power spectral density function. Simulation results obtained for the roll-plane half-car fitted with an HIS and those with conventional suspensions are compared in detail. In addition, sensitivity analysis of key parameters of the HIS to the ride performance is carried out through simulations. The paper also presents the experimental validation of the analytical results of the free and forced vibrations of the roll-plane half-car. T...
TL;DR: In this paper, a new method is presented for estimating the current sprung mass inertial parameters of a vehicle, such as the mass, pitch and roll mass moments of inertia, and lateral and longitudinal center of gravity locations.
Abstract: In this paper, a new method is presented for estimating the current sprung mass inertial parameters of a vehicle, such as the mass, pitch and roll mass moments of inertia, and lateral and longitudinal centre of gravity locations. The method measures the sprung mass response when the vehicle is driven over an unknown and unmeasured random road profile. From these measurements, the equivalent free-decay responses are extracted and modal analysis techniques used to estimate the sprung mass natural frequencies, damping ratios and mode shapes. This information is combined with a simplified vehicle estimation model, least squares analysis and known equivalent stiffness parameters to estimate the vehicles' inertial parameters. The results obtained from several simulation examples show that estimates of the inertial parameters generally have small relative errors.
TL;DR: In this article, a generalised 14 degree-of-freedom nonlinear vehicle model is developed and validated to evaluate vehicle ride and handling dynamic responses and suspension anti-roll and anti-pitch characteristics under various road excitations and steering/braking manoeuvres.
Abstract: In the first part of this study, the potential performance benefits of fluidically coupled passive suspensions were demonstrated through analyses of suspension properties, design flexibility and feasibility. In this second part of the study, the dynamic responses of a vehicle equipped with different configurations of fluidically coupled hydro-pneumatic suspension systems are investigated for more comprehensive assessments of the coupled suspension concepts. A generalised 14 degree-of-freedom nonlinear vehicle model is developed and validated to evaluate vehicle ride and handling dynamic responses and suspension anti-roll and anti-pitch characteristics under various road excitations and steering/braking manoeuvres. The dynamic responses of the vehicle model with the coupled suspension are compared with those of the unconnected suspensions to demonstrate the performance potential of the fluidic couplings. The dynamic responses together with the suspension properties suggest that the full-vehicle-coupled hydro-pneumatic suspension could offer considerable potential in realising enhanced ride and handling performance, as well as improved anti-roll and anti-pitch properties in a very flexible and energy-saving manner.
TL;DR: In this paper, the longitudinal vibration in bogies is used as a dynamic vibration absorber (DVA) to reduce the vertical bending vibration of railway vehicle carbodies in a simple and easy way.
Abstract: This paper presents a theory to utilise the longitudinal vibration in bogies as a dynamic vibration absorber (DVA) to reduce the vertical bending vibration of railway vehicle carbodies in a simple and easy way. This study focuses upon the interaction between carbody vertical bending and bogie longitudinal motion, and the condition for tuning the natural frequency of the bogie motion to the target carbody vibration is derived theoretically using a very simple formula. Numerical and experimental studies are then outlined to validate the theory and formula, and the DVA effects are observed from both of them. The effectiveness of the method is also confirmed from a running test with a Shinkansen train on a commercial line.
TL;DR: A numerical method for the time-optimal control of the race car is presented and is capable of operation with arbitrarily complex vehicle models as it requires only limited access to the vehicle model state vector.
Abstract: A numerical method for the time-optimal control of the race car is presented. The method is then used to perform the role of the driver in numerical simulations of manoeuvres at the limit of race car performance. The method does not attempt to model the driver but rather replaces the driver with methods normally associated with numerical optimal control. The method simultaneously finds the optimal driven line and the driver control inputs (steer, throttle and brake) to drive this line in minimum time. In principle, the method is capable of operation with arbitrarily complex vehicle models as it requires only limited access to the vehicle model state vector. It also requires solution of the differential equation representing the vehicle model in only the forward time direction and is hence capable of simulating the full vehicle transient response.
TL;DR: The errable driver model used in this paper is a model that emulates human driver's functions and can generate both nominal (error-free) and devious (with error) behaviours, which was used to evaluate the performance of several existing CW/CA algorithms.
Abstract: Collision warning/collision avoidance (CW/CA) systems must be designed to work seamlessly with a human driver, providing warning or control actions when the driver's response (or lack of) is deemed inappropriate. The effectiveness of CW/CA systems working with a human driver needs to be evaluated thoroughly because of legal/liability and other (e.g. traffic flow) concerns. CW/CA systems tuned only under open-loop manoeuvres were frequently found to work unsatisfactorily with human-in-the-loop. However, tuning CW/CA systems with human drivers co-existing is slow and non-repeatable. Driver models, if constructed and used properly, can capture human/control interactions and accelerate the CW/CA development process. Design and evaluation methods for CW/CA algorithms can be categorised into three approaches, scenario-based, performance-based and human-centred. The strength and weakness of these approaches were discussed in this paper and a humanised errable driver model was introduced to improve the developing...
TL;DR: In this paper, the authors define and compare alternative mathematical modelling approaches for the secondary air-spring suspension and assess their effect on the accuracy of rail vehicle dynamics multibody simulation, and demonstrate that a dynamic model of the airspring is required to assess ride comfort correctly, especially when the pneumatic layout of the suspension includes a long pipe between the air spring and the reservoir.
Abstract: The mathematical model of suspension components in a railway vehicle may have an important effect on the results of vehicle dynamics simulations and their accuracy in reproducing the actual vehicle behaviour. This paper aims to define and compare alternative mathematical modelling approaches for the secondary airspring suspension and to assess their effect on the accuracy of rail vehicle dynamics multibody simulation. To derive reliable models of the suspension, a quasi-static and dynamic characterisation of the suspension was performed by means of a full-scale laboratory experiment. Based on this, two different modelling approaches were developed for the airspring suspension: a quasi-static one, in which the frequency-dependent behaviour of the suspension is neglected, but the coupling between shear and roll stiffness is included, and a dynamic one in which additionally the frequency-dependent behaviour of the suspension in vertical direction is represented using a thermodynamic model, and additionally the dependency of lateral/roll stiffness parameters on the load is incorporated. The results of vehicle dynamics simulations in curved track and/or in the presence of crosswinds and the results of ride comfort calculations are presented, to assess the effect of the models developed, in comparison with a simpler model only reproducing the vertical and lateral stiffness of the suspension. It is demonstrated that the quasi-static coupling effect between shear and roll deformation in the airsprings can have a large effect on the simulation of load transfer effects in curved track and in the presence of crosswinds, and hence remarkably affect the assessment of ride safety and track loading, whereas the dynamic model of the airspring suspension appears to be required when wheel unloading under the action of crosswind is evaluated. Finally, it is shown that a dynamic model of the airspring is required to assess ride comfort correctly, especially when the pneumatic layout of the suspension includes a long pipe between the airspring and the reservoir.
TL;DR: In this paper, the authors deal with the terramechanical characteristics for wheel-soil contact dynamics modelling and simulation and its experimental validation on the basis of the future European Mars rover mission ExoMars.
Abstract: Rovers on Mars or the Moon for planetary exploration are obtaining increased importance within the spaceflight nations. To achieve full mission success, drivability and mobility in all kinds of complex motion scenarios have to be guaranteed. Here, proper modelling and understanding of the complex wheel–soil interaction, i.e. the terramechanics for flexible and rigid wheels interacting with hard, soft and loose soil, are a major driver for supporting reliable rover design and assisting in testing of the flight model. This paper deals with the terramechanical characteristics for wheel–soil contact dynamics modelling and simulation and its experimental validation on the basis of the future European Mars rover mission ExoMars. The physical contact models are integrated by a multi-body system approach and the performance of the rover mobility will be shown for various driving scenarios on hard and soft soil.
TL;DR: In this article, the effect of the air spring system on vehicle comfort is studied. But the authors focus mainly on the impact of a variable area orifice in the pipe that joints the air springs and the surge reservoir.
Abstract: The air spring is one of the components that most affects vehicle comfort. This element usually makes up the main part of the secondary suspension, which introduces both stiffness and damping between the bogie and the car body. Therefore, a deep understanding of this element is necessary in order to study the comfort of a vehicle, the influence of different parameters and the ways to improve it. In this work, the effect of the air spring system on comfort is studied. To accomplish this, a typical pneumatic suspension composition is briefly studied as a first step. Then, the test bench developed to characterise air springs is described, presenting experimental results. Correlation of the results with some theoretical models is also addressed. Afterwards, the effect of the air spring system on comfort is analysed, and finally, improvements from introducing a variable area orifice in the pipe that joints the air spring and the surge reservoir are discussed.
TL;DR: In this paper, a complete numerical model for studying the vertical dynamics of the vehicle/track interaction and its impact on the surrounding soil is presented, with the emphasis on vehicle modelling.
Abstract: This paper presents a complete numerical model for studying the vertical dynamics of the vehicle/track interaction and its impact on the surrounding soil, with the emphasis on vehicle modelling. A decoupling between the track and the soil is proposed, due to the difficulty of considering all the subsystem components. The train/track model is based on a multibody model (for the vehicle) and a finite element model (for the track). The soil is modelled using an infinite/finite element approach. Simulations of both models are carried out in the time domain, which is better able to simulate the propagation of the vibration waves and to take into account the possible nonlinearity of a component. The methodology is applied in the case of an urban tram track and validated with the available experimental data. Models for the tram, the track and the soil are described. Results from the complete model of the vehicle and a simple model, based on an axle load, are compared with experimental results and the benefits of a complete model in the simulation of the ground vibration propagation induced by railway vehicles are demonstrated. Moreover, a parametric study of the vehicle wheel type is conducted, which shows the advantage of a resilient wheel, for various rail defects.
TL;DR: In this paper, a proportional integral (PI) active front steering control and a PI active rear steering control with an additive feed-forward reference signal for the vehicle sideslip angle were shown to decouple the lateral velocity and the yaw rate dynamics.
Abstract: This paper shows that, for a four-wheel steering vehicle, a proportional-integral (PI) active front steering control and a PI active rear steering control from the yaw rate error together with an additive feedforward reference signal for the vehicle sideslip angle can asymptotically decouple the lateral velocity and the yaw rate dynamics; that is the control can set arbitrary steady state values for lateral speed and yaw rate at any longitudinal speed. Moreover, the PI controls can suppress oscillatory behaviours by assigning real stable eigenvalues to a widely used linearised model of the vehicle steering dynamics for any value of longitudinal speed in understeering vehicles. In particular, the four PI control parameters are explicitly expressed in terms of the three real eigenvalues to be assigned. No lateral acceleration and no lateral speed measurements are required. The controlled system maintains the well-known advantages of both front and rear active steering controls: higher controllability, enlarged bandwidth for the yaw rate dynamics, suppressed resonances, new stable cornering manoeuvres and improved manoeuvrability. In particular, zero lateral speed may be asymptotically achieved while controlling the yaw rate: in this case comfort is improved since the phase lag between lateral acceleration and yaw rate is reduced. Also zero yaw rate can be asymptotically achieved: in this case additional stable manoeuvres are obtained in obstacle avoidance. Several simulations, including step references and moose tests, are carried out on a standard small SUV CarSim model to explore the robustness with respect to unmodelled effects such as combined lateral and longitudinal tyre forces, pitch, roll and driver dynamics. The simulations confirm the decoupling between the lateral velocity and the yaw rate and show the advantages obtained by the proposed control: reduced lateral speed or reduced yaw rate, suppressed oscillations and new stable manoeuvres.
TL;DR: In this article, the excitation force spectra of railway traffic were determined by two completely different methods: a forward analysis based on vehicle, track and soil irregularities, which are taken from literature and axle-box measurements, calculates the vehicle-track interaction and gets theoretical force spectrum as the result.
Abstract: Excitation force spectra are necessary for a realistic prediction of railway-induced ground vibration. The excitation forces cause the ground vibration and they are themselves a result of irregularities passed by the train. The methods of the related analyses - the wavenumber integration for the wave propagation in homogeneous or layered soils, the combined finite-element boundary-element method for the vehicle-track-soil interaction - have already been presented and are the base for the advanced topic of this contribution. This contribution determines excitation force spectra of railway traffic by two completely different methods. The forward analysis starts with vehicle, track and soil irregularities, which are taken from literature and axle-box measurements, calculates the vehicle-track interaction and gets theoretical force spectra as the result. The second method is a backward analysis from the measured ground vibration of railway traffic. A calculated or measured transfer function of the soil is used to determine the excitation force spectrum of the train. A number of measurements of different soils and different trains with different speeds are analysed in that way. Forward and backward analysis yield the same approximate force spectra with values around 1 kN for each axle and third of octave.
TL;DR: In this article, a non-stationary random vibration technique for the analysis of three-dimensional, time-dependent, train-bridge systems that are subjected to excitations caused by track irregularities is presented.
Abstract: This paper presents a new non-stationary random vibration technique for the analysis of three-dimensional, time-dependent, train-bridge systems that are subjected to excitations caused by track irregularities. It is based on the pseudo-excitation method (PEM), which was previously applicable only to time-invariant systems, but is extended herein and the result is strictly proven to be applicable to time-dependent systems. The analysis proceeds by taking time lags between the wheel excitations into account, in order that the effects of track irregularity can be regarded as a set of three-dimensional, uniformly modulated, multi-point, different-phase, non-stationary random excitations. This enables the random surface roughness of the track to be transformed using PEM into the superposition of a series of deterministic pseudo-harmonic surface irregularities. The precise integration method is then extended to compute the corresponding pseudo responses. By using these pseudo-responses, various non-stationary random responses, including the time-dependent PSD and RMS of the system, can be obtained conveniently and efficiently. Numerical examples show the effectiveness and accuracy of the present method by comparison with Monte Carlo simulation. Additionally, the characteristics of such non-stationary random responses are discussed.
TL;DR: In this article, the authors extracted a trade-off strategy between longitudinal traction/braking force and cornering force by using jerk information through observing an expert driver's voluntary braking and turning action, and developed a new control concept, called G-Vectoring control, which is an automatic longitudinal acceleration control (No DYC) in accordance with the vehicle's lateral jerk caused by the driver's steering manoeuvres.
Abstract: We extracted a trade-off strategy between longitudinal traction/braking force and cornering force by using jerk information through observing an expert driver's voluntary braking and turning action. Using the expert driver's strategy, we developed a new control concept, called 'G-Vectoring control', which is an automatic longitudinal acceleration control (No DYC) in accordance with the vehicle's lateral jerk caused by the driver's steering manoeuvres. With the control, the direction of synthetic acceleration (G) changes seamlessly (i.e. vectoring). The improvements in vehicle agility and stability were evaluated by theoretical analysis and through computer simulation. We then introduced a 'G-Vectoring' equipped test vehicle realised by brake-by-wire technology and executed a detailed examination on a test track. We have confirmed that the vehicle motion in view of both handling and ride quality has improved dramatically.
TL;DR: In this paper, an adaptive sidelip angle observer considering tire-road friction adaptation is proposed for a single-track vehicle model with nonlinear tire characteristics, which can be easily obtained through road test data without using special test rigs.
Abstract: An adaptive sideslip angle observer considering tire-road friction adaptation is proposed in this paper. The single-track vehicle model with nonlinear tire characteristics is adopted. The tire parameters can be easily obtained through road test data without using special test rigs. Afterwards, this model is reconstructed and a high-gain observer (HGO) based on input-output linearisation is derived. The observer stability is analysed. Experimental results have confirmed that the HGO has a better computational efficiency with the same accuracy when compared with the extended Kalman filter and the Luenberger observer. Finally, a road friction adaptive algorithm based on vehicle lateral dynamics is proposed and validated through driving simulator data. As long as the tires work in the nonlinear region, the maximal friction coefficient could be estimated. This algorithm has excellent portability and is also suitable for other observers.
TL;DR: In this paper, the authors focus on the possibility of enhancing the performance of the ABS (Antilock Braking System)/EBD (electronic braking distribution) control system by using the additional information provided by "smart tyres" (i.e. tyres with embedded sensors and digital computing capability).
Abstract: The paper focuses on the possibility of enhancing the performances of the ABS (Antilock Braking System)/EBD (electronic braking distribution) control system by using the additional information provided by 'smart tyres' (i.e. tyres with embedded sensors and digital-computing capability). In particular, on the basis of previous works [Braghin et al., Future car active controls through the measurement of contact forces and patch features, Veh. Syst. Dyn. 44 (2006), pp. 3-13], the authors assumed that these components should be able to provide estimates for the normal loads acting on the four wheels and for the tyre-road friction coefficient. The benefits produced by the introduction of these additional channels into the existing ABS/EBD control logic were evaluated through simulations carried out with a validated 14 degrees of freedom (dofs) vehicle + ABS/EBD control logic numerical model. The performance of the ABS control system was evaluated through a series of braking manoeuvres on straight track focusing the attention on μ -jump conditions, while the performance of the EBD control system was assessed by means of braking manoeuvres carried out considering several weight distributions.