Generalised multi-axle vehicle handling

The familiar two-axle bicycle model and associated basic concepts of vehicle handling are reviewed and used to introduce minor changes in convention from the literature. The two-axle model is extended to a three-axle vehicle to illustrate the effectiveness of the notation combined with a simplifying mathematical identity found in the two-axle vehicle literature. A generalised model is then developed that produces dynamic equations of motion by inspection for a vehicle with an arbitrary number of steerable and non-steerable axles. Furthermore, the vehicle dynamic concepts of understeer and wheelbase are generalised and can be directly computed for various arbitrary vehicle configurations.     

Development of a generalised equivalent estimation approach for multi-axle vehicle handling dynamics

This paper devotes analytical effort in developing the 2M equivalent approach to analyse both the effect of vehicle body roll and n-axle handling on vehicle dynamics. The 1M equivalent vehicle 2DOF equation including an equivalent roll effect was derived from the conventional two-axle 3DOF vehicle model. And the 1M equivalent dynamics concepts were calculated to evaluate the steady-state steering, frequency characteristics, and root locus of the two-axle vehicle with only the effect of body roll. This 1M equivalent approach is extended to a three-axle 3DOF model to derive similar 1M equivalent mathematical identities including an equivalent roll effect. The 1M equivalent wheelbases and stability factor with the effect of the third axle or body roll, and 2M equivalent wheelbase and stability factor including both the effect of body roll and the third-axle handling were derived to evaluate the steady-state steering, frequency characteristics, and root locus of the three-axle vehicle. By using the recursive method, the generalised 1M equivalent wheelbase and stability factor with the effect of n-axle handling and 2M equivalent generalised wheelbase and stability factor including both the effect of body roll and n-axle handling were derived to evaluate the steady-state steering, frequency characteristics, and root locus of the n-axle vehicle. The 2M equivalent approach and developed generalised mathematical handling concepts were validated to be useful and could serve as an important tool for estimating both the effect of vehicle body roll and n-axle handling on multi-axle vehicle dynamics.     

A comparative study of equivalent modelling for multi-axle vehicle

In this paper, equivalent modelling methods of a multi-axle vehicle are presented and compared. Firstly, for the sake of comparison, a single-track model of a three-axle and a two-axle vehicle is developed, and then existing equivalent modelling derivations are presented and discussed. Next, the proposed model-based dynamic equivalence of force/moment at the centre of gravity (CG) is introduced and optimised. It represents the approximately equivalent steady-state and transient response of the yaw rate and side slip angle, which allows different cornering stiffness on the central and rear axle. Finally, to demonstrate how the proposed method is advantageous to the other equivalent models available in the literature, different simulation cases are compared in the dimension of time-domain, eigenvalues characteristics and frequency-domain. Furthermore, the proposed method is extended to any multi-axle vehicle configurations and a general expression is formulated.     

Kinematic and dynamic analysis of a heavy truck with individual front suspension

The main focus of this work is on the characteristics of a commercial vehicle with individual front suspension (IFS). Both kinematic and dynamic properties of the vehicle are investigated through simulations and analytical expressions. Moreover, employing the model of the tractor semitrailer combination, the study presents the results of comparison between the trucks with IFS and rigid front axle with respect to comfort and handling. This is done by analysing the responses of the vehicles to different road and steering inputs. The obtained results show enhanced comfort and steering feeling for the truck with IFS.     

Material characteristics of a vehicle door seal and its effect on vehicle vibrations

The vibration characteristics of the door panels are affected by the weatherstrip seals used in between the doors and vehicle body along the perimeter of the doors. The weatherstrip seals exhibit nonlinear and viscoelastic material properties that vary with frequency, temperature, strain rate and amplitude, and previous load history. The material properties of the seal must be investigated carefully in order to predict the vibration characteristics of the automobiles under different loading conditions.

In this study, we developed hyperelastic and viscoelastic models of the weatherstrip seal to predict dynamic performance of a vehicle door and its effect on the overall vehicle dynamics. For this purpose, first, static compression and stress relaxation experiments were performed on the seal using a robotic indenter equipped with force and displacement sensors and then a finite element model utilising the results of these experiments was developed in ANSYS. Finally, a representative model of the seal was integrated into the finite element model of the vehicle door to investigate its effect on the vehicle vibrations. The model predictions were validated using experimental modal analysis performed on the vehicle door with and without the seal. It was observed that the seal has a significant effect on the vehicle dynamics.     

Quasi-steady-state linearisation of the racing vehicle acceleration envelope: a limited slip differential example

In the motorsport environment, passive limited slip differentials are a well-established means of improving the traction limitation imposed by the open differential. Torque sensing types are highly adjustable, and can alter both the stability and agility of the vehicle in the various cornering phases of a typical manoeuvre. In this paper, an adjustable clutch plate or ‘Salisbury’ differential model is presented, which can significantly alter its torque bias characteristics through adjustments in the drive/coast ramp angle, the number of friction faces and preload. To allow robust evaluation of differential parameter changes on ultimate vehicle performance and handling balance, a unified acceleration or ‘GG’ diagram framework is then described. This builds on traditional GG diagram approaches, by using nonlinear constrained optimisation to define both the vehicle acceleration limits and a ‘feasibility’ region within the performance envelope. By linearising a seven degrees of freedom vehicle model at multiple operating points, eigenvalue and yaw rate response analysis is then used to establish contours of stability and agility throughout the GG envelope. This brings new insights into the way in which handling balance changes below and up to the vehicle's acceleration limits.     

二甲醚重型商用车开发

本文介绍了一款二甲醚重型商用车的设计开发方案,包括开发内容、需解决的技术难点和总体设计方案。试制结果表明该二甲醚重型商用车环境适应性强,零部件通用性高,可为其他二甲醚汽车产品的开发提供参考经验。     

Prediction of ride quality of a Maglev vehicle using a full vehicle multi-body dynamic model

In magnetically levitated (Maglev) transportation systems, especially in electromagnetic suspension system (EMS) type Maglev systems, highly accurate prediction of ride quality is very important in order to reasonably relax guideway construction tolerances or constraints and stiffness while meeting the specification for ride comfort, thereby reducing guideway construction and maintenance costs. A full vehicle multi-body dynamic model is proposed, to facilitate a rigorous ride quality prediction of an EMS-type Maglev vehicle. Using the more realistic dynamic model proposed in this paper, the effects of guideway deflection limits, surface roughness, and levitation control system parameters on ride quality are studied numerically. The results obtained from the simulation studies are then used to facilitate a discussion of the trade-off between guideway smoothness and vehicle suspension. It can be expected that these studies could suggest cost-effective specifications for guideway construction tolerances and stiffness and EMS.     

Comparison of various double-lane change manoeuvre specifications

One of the commonly used performance measures to quantify a vehicle's handling transient dynamics is the maximum forward speed (MFS) while passing a certain specified double-lane change (DLC) manoeuvre without violating the boundary and tyre lift-off. The MFS is directly associated with the minimum curvature radius (MCR) of the vehicle centre of gravity (CG) trajectory controlled by the driver during the manoeuvre. The MCR is further affected by the vehicle dimensions to meet the boundary condition. In this study, a single heavy vehicle CG trajectory is assumed to be a combination of three straight lines and two third-order spline curves. A heavy vehicle multi-body system model established with ADAMS/Car is correlated with test data for step-steer and constant radius cornering events, and then the model is used to demonstrate that the assumptions considered in the formulation applied in this paper are valid for this specific vehicle category. The MCRs of four heavy vehicles are maximised among all the possible choices of the vehicle CG trajectory during each of five specific DLC manoeuvres, including North Atlantic Treaty Organization (Allied Vehicle Testing Publication 03-160W), International Organization for Standardization (ISO) 3888-1, ISO 3888-2, Consumer Union Short Course and Test Operations Procedure 2-2-609. The maximised MCR (MMCR), considered as the best possible choice of vehicle CG trajectories, is further solved as a function of the vehicle width and length. The results will show the sensitivity of the MMCR to the vehicle length and width, thus the impact on the vehicle transient handling dynamics. Finally, the comparison of five DLC specifications may help users to correlate a vehicle's MFS from one specification to others.     

浅谈二手商用汽车市场前景及鉴定评估

通过对近几年中国新车市场迅猛提升的现状和二手车销量增长的态势,分析二手车市场的前景和鉴定评估人才的需求。提出二手商用汽车鉴定评估主要理论、方法,将FMEA(失效模式与影响分析)导入二手商用车鉴定评估中,并进行分析和阐述。     

Lateral dynamics emulation via a four-wheel steering vehicle

In this paper, we examine the lateral dynamics emulation capabilities of an automotive vehicle equipped with four-wheel steering. We first demonstrate that the lateral dynamics of a wide range of vehicles can be emulated, either with little or with no modification on the test vehicle. Then we discuss a sliding mode controller for active front and rear wheel steering, in order to track some given yaw rate and side-slip angle. Analytically, it is shown that the proposed controller is robust to plant parameter variations by±10%, and is invariant to unmeasurable wind disturbance. The performance of the sliding mode controller is evaluated via computer simulations to verify its robustness to vehicle parameter variations and delay in the loop, and its insensitivity to wind disturbance. Finally, the emulation of a bus, a van, and two commercially available passenger vehicles is demonstrated in an advanced nonlinear simulator.     

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

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

重型商用汽车轻量化研究

轻量化是汽车设计水平的一项关键指标,而谈起汽车轻量化,行业内往往关注的是乘用车的轻量化技术重型商用车的轻量化技术往往被忽视,本文就重型商用车轻量化技术的现状和发展空间及瓶颈做简要阐述。     

悬架K&C特性对车辆操控性能影响的分析

悬架系统设计开发是底盘开发的重要环节,对于整车操控性能有至关重要的影响。本文以某A级车的大量KC数据为基础,利用面向总成特性的整车动力学仿真软件CarSim分析悬架KC特性变化对整车操控性能的影响,并运用试验统计学中的DOE试验设计方法计算各特性车辆操控性能指标的主效应,得到了悬架KC特性影响整车操控性能的规律,在设定悬架性能目标时重点关注,为整车开发早期的结构选择和后续的结构设计提供了依据。     

商用车驾驶室外观造型的模糊评价

通过建立模糊评价模型,提出了对商用车驾驶室外观造型的模糊评价方法。基于此评价方法,将以往商用车驾驶室外观造型的定性评价转化为定量评价,解决了商用车驾驶室开发中外观造型评价存在的问题,使评价方法在综合性、合理性、科学性等方面得到了改进。     

Modelling and analysis of a gyrostat elastically attached to a vehicle

In recent studies, the dynamic response of a passenger car to a gyrostat was investigated for a series of driving manoeuvres, but the gyrostat was assumed to be rigidly supported, thus neglecting the effect of rotor precession. The aim of the present study is the modelling and investigation of the gyrostat-vehicle interaction for elastically mounted gyrostats. For this purpose, a general model describing the motion of a gyrostat elastically supported by a moving platform is derived. Emphasis is placed on the mathematical derivation, where all considerations that are necessary to arrive at the final result are included. Thus, the presented considerations and results can be easily adopted and are suitable to serve beyond their actual purpose as a reference work for other applications. The derived model is tested with the aid of vehicle dynamics simulations and the simulation results prove to be consistent with the results of the rigid attachment model, provided that the elastic approach is subjected to high-bearing stiffnesses. However, it is shown that at lower bearing stiffnesses the solutions are progressively different, since low-bearing stiffnesses enable the gyrostat to move, due to the compliance of the bearings itself, relative to the vehicle chassis with high-angular velocities.     

Model reduction in vehicle dynamics using importance analysis

Previous work by the authors developed a novel model reduction method, namely importance analysis, that offered a unique set of properties: concurrent dynamic and kinematic reduction, applicability to nonlinear systems, preservation of realisation, and trajectory dependence. This paper investigates the utility of importance analysis as a model reduction tool within the context of vehicle dynamics. To this end, a high-fidelity model of a High Mobility Multipurpose Wheeled Vehicle (HMMWV) is considered, and this model is reduced for three different scenarios. Reduction is achieved in both dynamics and kinematics while preserving the original definition and interpretation of state variables and parameters. Furthermore, the resulting reduced models are very different in terms of complexity, containing only what is necessary for their respective scenarios, and providing important insight and computational savings. The conclusion is that importance analysis can be an invaluable reduction tool in vehicle dynamics, offering the aforementioned unique set of properties.     

多功能车操纵稳定性的虚拟样机实验研究

采用面向整车系统的数字化虚拟样机技术,利用ADAMS软件,建立了某多功能车(MPV)的整车虚拟样机模型,在ADAMS虚拟环境模式中对其操纵稳定性进行了大量的仿真计算和实验研究,研究结果表明,该车初始参数匹配状态下整车操纵稳定性能较好。实验结果数据为评估、改进、优化同型车辆提供了重要的理论参考。     

Extended study of railway vehicle lateral stability in a curved track

This article presents results of the studies aimed at more accurate stability analysis of railway vehicles in a curved track. More accurate analysis means extended study of the stability as compared with the method used by the authors so far. New measures undertaken by the authors in order to achieve the goal are explained. Besides, differences between results obtained with the earlier and extended approaches are presented and discussed. Results that are expected on the basis of the theory are confronted with practical capabilities to generate them through simulations at the same time. The issues of interest are precise determination of nonlinear critical velocity, determination of linear system critical velocity, determination of unstable periodic and unstable stationary solutions, existence of multiple solutions and correct determination of velocity at which unbounded growth of the solutions (lateral dynamics coordinates) happens during calculations resulting in their stop.     

Ride quality evaluation of a vehicle with a planar suspension system

The longitudinal connection between a chassis and a wheel in a conventional vehicle suspension system is commonly very stiff than the vertical connection. Such a mechanism can efficiently isolate vibrations and absorb shocks in the vertical direction but cannot sufficiently attenuate the impact in the longitudinal direction. In order to overcome such a limitation, a planar suspension system (PSS) with spring–damper struts in both the longitudinal and vertical directions is proposed so that the vibration along any direction in the wheel rotation plane can be isolated. In this paper, the dynamic responses of a vehicle with PSS due to a single bump and random road unevenness are investigated. The ride quality of the vehicle with PSS is evaluated in accordance with ISO 2631. A comparison with that of a similar conventional vehicle is conducted to demonstrate the promising potentials of the PSS in improving the vehicle ride quality.