Automotive Stability and Handling Dynamics in Cornering and Braking Maneuvers

SUMMARY

Automotive steering behaviour is classified for steady-state cornering and the definitions of over-/understeer and stability/instability are well known. In this paper it is intended to apply these definitions to combined cornering and braking maneuvers i.e. to extend the criteria to quasi-steady-state conditions. This way of investigation was chosen because it gives a clear idea of the typical handling behaviour. Furthermore, the vehicle behaviour is analyzed using the cornering stiffness of the axles and front/rear cornering stiffness ratio because this is always of primary significance. The following contribution is based on a theoretical analysis considering the most important non-linear vehicle properties.

The paper deals with two groups of vehicles: single vehicles (passenger cars) and combinations (passenger car/caravan and tractor/semitrailer). In the case of combinations the effect of trailers on the towing vehicles is examined. So, careful attention is paid to the coupling forces, which alter the wheel loads and influence steerability and stability.     

Stabilization of Passenger Car-Caravan Combination Using Four Wheel Steering Control

This study aims to stabilize the trailer at high speed. The behavior of passenger cars with four wheel steering system, vehicles with rear wheel steering and of trailer and passenger car are similar. This is regarded as an optimal regulator problem with linear equation of motion, and a state variables feedback control system is adopted. The problem of stability at high speed on a straight course can be solved. Therefore, the passenger car-trailer system can be stabilized. Furthermore, this study indicates the way forward to stabilize a passenger car-trailer system.     

Seat Movement Relative to the Passenger Compartment—A Possible Method to Improve Passenger Protection During Frontal Impacts

The present study is meant to prove in a theoretical way that a controlled seat movement relative to the passenger compartment will result into an improvement of passenger deceleration during vehicle frontal impacts.

This effect could be of advantage in some respects: as possible alternative for the most favourable design of the energy absorbing zones of a vehicle, as an additional safety device for the occupants of heavy vehicles with relatively soft impact absorbing zones in case of crashes against rigid obstacles, and in small vehicles where only little space exists for passenger protection.

With regard to the complexity of this subject, the study at hand must be regarded as a first step towards the final solution of the problem.     

Very-High-Speed Tests on the French Railway Track

The very-high-speed tests carried out by SNCF between the end of 1989 and May 1990, are an extension of the investigations which have been made for many years in order to acquire the control of high speeds. The high-speed run which ended the tests is well known [1], [2],[3].

In order to place the final test campaign in its context, we can recall progression made during the last decade.

In February 1981, the maximal speed of 380 km/h was reached with a TGV-PSE¹ train set, having the same configuration as the series, but only seven trailers instead of eight.

During the following years, until 1986, the pneumatic suspension and the new Y 231 carrying bogies designed for TGV-ATL train sets were developed, with numerous test runnings in the speed range from 300 to 350 km/h, in order to obtain certitudes as regards the stability of the bogies and the appropriate choice of anti-hunting devices for commercial speeds of 270 km/h (LGV-PSE) or 300 km/h (LGV-ATL).

These tests allowed the definition of the TGV equipment design principles, which are applied today as regards the critical speed of the bogies.

Between 1985 and 1988, the development of the prototype train set equiped with self-controlled synchronous motors (March 1988) led once more to numerous runnings at high speed, in December 1988 with the so-called “operation TGV 88”. During this operation, the speed range from 350 to 400 km/h was investigated (maximal speed 408,4 km/h on December 12th 1988).

Apart from the capability of the synchronous traction equipment to develop the required power and the performance consisting in the realization of such tests on a line kept in operation (LGV-PSE), the teachings gathered together during this test campaign were decisive for the pursuit of the operation.

On this occasion, we discovered that:

-with the single-phase GPU pantograph mounted on this train set, we could get the current collection under control without difficulties inside the studied speed range,

-the bogies presented a stability margin distinctly higher than that which had been estimated, according to the results of former experiences.

Consequently, the test campaign of the TGV 117 could be engaged with a great confidence in the capabilities of the TGV equipment to achieve markedly higher speeds with full safety. The preparation of this test campaign had begun in 1986 and was conducted in a parallel direction to the above mentioned experimentation.

The campaign was preceded by a preliminary test campaign with the train set TGV-ATL n° 308, with a reduced train composition, including eight trailers. The goal was the validation, until 390 km/ h, of the test field consisting in the TGV-ATL Aquitaine branch, as well for the track as for the overhead contact line, the achievement of which was just ended.

The operation TGV 117 was then carried out in two phases:

-in December 1989 the train set TGV-ATL 325 with a reduced train composition consisting in four trailers between two motor cars reached the maximal speed of 482,4 km/h on December 5th,

-in May 1990 the same train set, but with only three trailers, improved the performance unto the final record: the speed of 515,3 km/h was reached on May 18th.     

The Dynamics of Single Track Vehicles

The paper contains a brief review of the more subjective aspects of the steering behaviour of single track vehicles, a review of the more significant published work in the field, and an assessment of the current state of understanding and likely ways in which further progress can be made

Attention is drawn to the many areas of agreement between theory and practice and to some areas of disagreement. The greatest need now seems to be for the incorporation of more complex tyre models into vehicle handling models.     

The Steering Characteristics of Multiple Axle Bogie Systems

Legislation limits the load that may be transferred to the roadway by the axies of a commercial vehicle and this has resulted in the development of multi axle bogies for both the tractor and trailer units of articulated vehicles and at the rear of rigid vehicles, some of these bogies contain self steering or articulation steered axles

Experience shows that the tyre wear characteristics of multi axle bogies may be unsatisfactory. The paper analyses the role of such bogies in the context of vehicle handling and shows how the lateral tyre forces vary between the axles. An hypotheses relating the forces in a steady state turn to wear is given. The analysis may also be applied to the general case of vehicle handling.     

汽车列车的转弯半径计算

由于运输效率提升的需要,一辆汽车会拖挂多台挂车,为了满足后期运营场景,在设计之初就应对这种汽车列车的最小转弯半径进行计算,评估运营场地或道路情况。文章主要通过汽车列车转动时没有相对转动角速度这一前提条件,对拖拽多台挂车的汽车列车的最小转弯半径进行分析计算,从而得出拖拽3台挂车的最小转弯半径公式,并由此推导出拖拽n台挂车的转弯半径的计算公式。运用该公式对某一机场牵引列车进行计算,该公式的计算结果与实际运营场景相符,证实该公式可用于工程开发和实车应用评估。     

A Two DOF Model for Jerk Optimal Vehicle Suspensions

Researchers have proposed various active suspension concepts to optimize the tradeoff between ride and handling in passenger vehicles. A few investigators suggested inclusion of the passenger jerk, the derivative of the passenger acceleration, as a measure of ride quality in the performance index. Minimization of a performance index then optimizes both the acceleration and jerk as well as other outputs representing handling quality and design constraints. This approach is called jerk optimal control.

This paper compares two different vehicle models of increasing complexity (the one and two DOF quarter car) using jerk optimal control. Different aspects of suspension performance are investigated, including the structure of the system transfer functions, the structure of the force control laws, and the tradeoffs between the various root mean square (rms) outputs defining system ride and handling performance. Tables compare the numerical results of the two models, allowing predictions of actual vehicle performance.

The results of the two models show the same basic trend for the tradeoff between ride and handling quality: at a constant level of rms passenger acceleration the rms passenger jerk can be reduced significantly, but only at a cost of increased rms tire deflections. In physical terms, a softer ride results in degraded handling performance. For a chosen level of ride improvement, the more realistic two DOF quarter car model predicts more severe degradation of handling. The latter nevertheless predicts a substantial increase in vehicle ride quality is possible through a 55% reduction in jerk. It is expected that actual suspensions could also produce significant increases in ride quality through jerk reduction. Jerk optimal suspensions could find use both in higher end passenger vehicles and in transports for vibration sensitive cargo.     

Discomfort from feeling vehicle vibration

Vehicle refinement should include a consideration of the discomfort likely to be caused by vibration. This paper reviews the measurement, the evaluation, and the assessment of vehicle vibration felt by drivers and passengers.

The feeling of vibration that gives rise to judgements of vibration discomfort can be predicted using evaluation procedures that take into account human sensitivity to different magnitudes, frequencies, directions, and durations of vibration. The evaluation methods make it possible to optimise vehicles via dynamic modelling before the production of prototypes and they assist the testing and optimisation of prototypes and production vehicles.

Vibration evaluation provides imperfect predictions of discomfort when driver or passenger opinion is influenced by factors other than the vibration that is being measured and evaluated. Vibration evaluation can detect changes that are not detectable subjectively since smaller changes can be detected by measurement and evaluation than by subjective assessment.     

Dynamic Measurements in the Research and Development of Rail Vehicles

This paper reviews the measurements which are necessary to all aspects of vehicle dynamics as applied to rail vehicles. Although an attempt has been made to introduce some reference to measurements made in Europe and America, the detailed discussion has been limited to those techniques employed by British Rail. This has the advantage that the discussion can be first hand and therefore more specific.

For convenience the measurements have been collected together under four broad headings.

1. Measurements of rail system data.

2. Measurements of vehicle parameters.

3. Measurements to validate theory and predictions.

4. Measurements of vehicle performance.     

Steering and Dynamic Stability of Railway Vehicles

For railway vehicles having coned wheels mounted on solid axles there is a conflict between dynamic stability and steering ability

It is shown that the stiffness and kinematic properties of all possible interwheelset connections are characterised by two properties describing the distortional characteristics of the vehicle in plan. Within this framework, the various possibilities for steered wheelsets are considered, and several past and current proposals are reviewed. Using the linear approach to dynamic stabibty and curve negotation the performance of existing and newly proposed configurations is discussed

For any symmetric, two-axle vehicle it is shown that for perfect steering on a curve there should be zero bending stiffness between the wheelsets. It is further shown that if the bending stiffness is zero, the vehicle lacks dynamic stability as the critical speed of instability, is zero. In this case, the vehicle undergoes a steering oscillation which occurs at the kinematic frequency of a single wheelset and which is a motion in which pure rolling occurs

Similar results are obtained with vehicles with three or more axles if adjacent axles are connected by shear structures. However, it is shown that it is possible to satisfy both the requirements of perfect steering and a non-zero critical speed if the vehicle has zero bending stiffness and if, in addition to adjacent wheelsets being connected in shear, at least one pair of non-adjacent axles are connected by a shear structure.     

关于重卡防护装置增加阻尼系统的可行性分析与设计

市场上汽车和挂车后下部防护装置多为刚性连接,当发生车辆追尾碰撞时,不能有效保护乘坐人员的安全,屡屡发生小车钻进大货车尾部伤亡事故.本文目的是提供一种汽车和挂车后下部柔性防护装置,克服已有汽车和挂车后下部防护装置缺点和不足,使汽车发生追尾碰撞时避免发生伤亡事故.此后下部防护装置不仅仅是保护追尾的小车,同时也保护了货车自身...     

纯电动乘用车的进展

文章介绍了国外各个历史阶段的主要纯电动乘用车的主要技术参数和市场运营情况,以及我国高速纯电动乘用车和低速纯电动乘用车的产品开发情况和主要技术参数,并根据纯电动乘用车的技术特点进行了发展趋势的分析,指出由于基础充电设施不完善,近期我国纯电动乘用车在城市内不能普及,主要倡导发展纯电动公交车,但是低速纯电动乘用车在农村前景广阔。     

Nähere Untersuchungen zur stationären Kurvenfahrt von Einspurfahrzeugen

Detailed Investigations of the Steady State Turning of Single Track Vehicles

In the paper the steady state turning of single track vehicles on a horizontal, even road is investigated, supposing the air to be at rest. The vehicle model used has six degrees of freedom: rolling, yawing, pitching and bouncing of the vehicle, rotation of the front wheel system (steering) relatively to the main frame and distortion of the rear wheel system due to limited stiffness of its linkage, and also takes into account wind drag and gyroscopic effects generated by wheels and other vehicle components. A special importance is given to the geometry of the vehicle

The results show a comparison of two types of motorcycles with different geometries and tires. To characterize the vehicle behaviour the roll, side slip and steering angle as functions of the normal acceleration are used. A more detailed study in respect to the steering torque is added.     

Ride Quality and Dynamics of Rail Vehicle Models for Microcomputers

This paper describes mathematical and computer models for ride quality and dynamics of rail vehicles developed for running on personal computers. The purpose of the computer simulations is for prediction of ride quality in order to study the dynamic stability of the system and the effect of track quality and irregularities on ride quality.

In deriving the equations of motion for dynamic stability, the tangential forces acting on the contact areas between the wheels and rails are of fundamental importance in railway vehicles dynamics and are included in the analysis [1]. These forces are due to the creep phenomenon between the wheel and the rail on which it is rolling. Track irregularities are defined in terms of four components consisting of gauge, cross level, alignment and vertical surface profile [2]. Relation of allowable track irregularities versus speed is given by the FRA Track Safety Standards. Analytical representation of track irregularities should include both PSD (Power Spectral Density) for CWR (Continuous Welded Rail) as well as discrete inputs from track joints.

In this paper, the rail vehicle suspension analysis and dynamics mathematical and computer models are described. The computer models are written in Fortran 77 and designed to run on personal computer. The paper also discusses programming considerations that must be taken into account when programming for microcomputers under DOS (IBM's Disk Operating System) and MS or RM Fortran Compilers. Most of the considerations are however, valid in general with respect to engineering software development and programming for microcomputers.

Computer graphics is a powerful tool for visualization of the resulting solutions such as the display of the characteristic roots for the eigenvalues solution on a root locus plot and representation of acceleration levels versus the “Reduced Comfort Boundary” limits defined by the International Standards Organization” (ISO 2631-1985). In this paper some examples of these resulting outputs are presented and their significance discussed.     

Vergleich einiger Rechen- und Messergebnisse zum Fahrverhalten von Sattelzügen

In this paper some results of theoretical and experimental investigations on the dynamic directional properties of heavy tractor-semitrailer vehicles are presented.

A nonlinear digital computer model was developed on which the theoretical system analysis is based. This model takes account of the nonUnear tire properties and the friction couple of the fifth wheel. A combination of numerical computation methods (Runge-Kutta and Newton-Raphson techniques) is used for the digital computer simulation.

Full scale road tests with articulated vehicles of 38 ton total weight were conducted for experimental validation of the used theoretical model. As input signals to the vehicle, predetermined steering wheel angle functions were used. The system output signals corresponding to these input functions were measured and stored.

A comparison of the obtained theoretical and experimental results shows a very good qualitative agreement and hence leads to the conclusion that the developed theoretical model can give consistent estimates of the basic dynamic vehicle properties.     

Identifying multiclass vehicles using global positioning system data

It has been previously evidenced that global positioning system (GPS) data can be used to distinguish passenger cars from delivery trucks. In this paper, a machine learning approach is proposed to use GPS data to identify multiclass vehicles, including passenger cars, single unit trucks, and multi-trailer trucks. The method is acceleration and deceleration-based since it considers the variations of acceleration and deceleration as the most effective features to classify vehicles. The overall classification result for the three vehicle classes is about 75%. The major challenge is to distinguish single unit trucks from multitrailer trucks due to their somewhat similar mobility patterns. The paper also explores the impacts of GPS sampling frequency on vehicle classification. It is found that the proposed multiclass vehicle classification can be reasonably conducted if the data are collected frequently enough (i.e., every five seconds or more frequently) to capture the major acceleration and deceleration processes. The proposed method can be considered as a low-cost and non-intrusive approach to collect vehicle class information and to potentially supplement the existing classification schemes in urban areas.     

Dynamic Behaviour of Ore Wagons in Curves at Malmbanan

The transportation of ore can be made more cost efficient by use of bigger and heavier trains. An increase in axle load is thereby wanted. The fleet of ore wagons of today at Malmbanan/Ofotbanan in northern Sweden and Norway has to be updated. It is of interest to find out if it is possible to allow a higher axle load on the track with new wagons

To be able to understand and predict the effects on track wear depending on what type of vehicle that is in use, the contact forces between wheels and rails have to be determined. A computer aided analysis has been made of the dynamic behaviour of three test vehicles equipped with different types of three-piece bogies running at Malmbanan. The vehicles are modelled and their interaction with the track is analysed using the multibody simulation package GENSYS

The simulations show that, even if the axle load is increased from 25 tons to 30 tons and the velocity is increased from 50 km/h to 60 km/h, it is possible to reduce lateral track forces and wear in curves by using a different bogie than the standard three-piece bogie used today.     

Simulation of Multibody Vehicles Moving over Elastic Guideways1

This paper describes the present state of a general purpose computer program for calculating the dynamic response of vehicles travelling over guideways which may be elastic.

The linearized state-equations of motion for general multibody vehicles are constructed automatically by the program, these equations are supplemented by the equations for the active subsystems. Finally, the vehicle system equations are combined with the modal equations for elastic guideways and the complete set of coupled equations is solved simultaneously by numerical integration.