Showing papers in "International Journal of Vehicle Design in 2014"

Road surface description and vehicle response

Abstract: The paper is concerned with the determination of vehicle response due to traversal of a road surface described by means of the concepts of random process theory. The relevant response theory is developed, first, in terms of a four-variate excitation and then in terms of the possible simplifying assumptions. The relationship between excitation and the road profile is explained. Roads are described in terms of single profiles, profile pairs and then, using the concept of isotropy, complete surfaces. The validity of the isotropic hypothesis is considered.

Exploring the optimum posture for driver comfort

Abstract: Published postural angles for driving comfort are based on theoretical calculations and not observed driving postures. An experiment was conducted to investigate observed optimum driving postures and positions of the main driving controls for comparison with available data. New guidelines for optimum postural comfort have been developed. The recommended range of postural angles should be used with care because not all people will be comfortable with the whole range as individuals. Furthermore, inter-relationships between adjacent joint angles need to be considered. The data also support a strong need for both horizontal and vertical adjustment in the steering wheel.

An analytical model of pneumatic tyres for vehicle dynamic simulations. Part 2: Comprehensive slips

Abstract: This is the second paper in a three–part study presenting an analytical approach for determining tyre dynamic properties. In this study analytical formulations are derived for the tyre dynamic properties as functions of the slip ratio, slip angle, camber angle and other tyre dynamic parameters. There formulae can be used for the general vehicle simultaneous in braking/traction and steering manoeuvres with a varying camber angle are regular or irregular terrains. In this paper the lateral force and self–aligning torque due to both slip and camber angles are first studied. The longitudinal, lateral forces and self–aligning torque during braking/traction and steering without any camber angle or with a varying camber angle are also analysed. Also, both the friction eclipse concept and the friction circle concept are investigated.

Determination of load spectra for design and testing

Abstract: For the service fatigue life of components and systems, operational loading conditions are of paramount importance. The load spectra used for the design and testing must fulfil the task of predicting the service life, taking into account the customer usage as well as reliability requirements. In this paper, the criteria and the main parameters for the load spectra to be used for design and testing are described, the procedures to determine these spectra treated, and the requirements concerning the reliability discussed.

Collapse of thin–wall composite sections subjected to high speed axial loading

Abstract: In this paper, static and dynamic crushing tests in a speed range of 18–24 m/s were conducted on specimens of different geometries: square tube, circular tube, and circular cone specimens made of three different composite materials. Two of the composite materials consist of fibreglass and vinylester resin, but with different fibre contents and ply lay–up. The third is made of fibreglass and polyester resin. This study investigated the effects of specimen geometry and crush speed on the specific energy absorption of these composite materials. It was found that for specimens showing stable crushing, greater thickness lends to reduce the specific energy absorption; square tubes have less specific energy absorption than circular tubes, and greater cone angle results in lower specific energy. Crushing speed does not have significant effect on the specific energy absorption of thin–walled circular or square tubes made of the three kinds of composite materials. However, specific energy of thin–walled circular conical specimens made of polyester resin and random chopped strand mat of glass fibre were reduced by some 35% under a crushing speed of about 21 m/s. It is also clear from this study that at higher crush speeds the crushing mechanisms of tubular specimens with large thickness differ from the static cases.

Dynamic optimization method for design and rating of the components of a hybrid vehicle

Abstract: The paper presents a new method for the optimal rating of the components of an autark hybrid driveline. The method uses dynamic optimisation to calculate the optimal torques for both motors and the optimal CVT gear ratios for a given driving cycle of the vehicle. The cost function for the optimisation uses among other things the fuel consumption, which has to be minimised. From the optimal torques and gear ratios, conclusions concerning the rating of the motors can easily be made. The methods derived are used for the TU Munich Hybrid Vehicle project. In this project, a parallel hybrid with an i²–CVT is under development.

Disc brake squeal noise generation: predicting its dependency on system parameters including damping

Abstract: The concept of the mechanism of disc brake squeal noise generation being a 'kinematic constraint' or 'geometricallv induced' instability is extended to include pad support and disc damping. A dynamic analysis is presented of a double–pin and disc system and the conditions for unstable oscillatory motion to occur are detailed. It has been shown previously that there is a good correlation between the occurrence of squeal noise and the predicted unstable states. Illustrations are given of the effects of varying, the system parameters, of having dissimilar pins reacting on the disc, and of including pin support and disc damping. From the wide range of possible system parameter combinations, producing many and varying effects on the size motion to occur is that one or bath of the pins has a negative (digging–in) angle of orientation to the disc surface within the range 0 < θ < tan–1μ; sufficient conditions depend on the magnitude of the system parameter. Stable motion may be obtained by using dissimilar pin orientations, having a large disc mass or high pin torsional stiffnesses. Increasing The disc damping has little effect on the area of the unstable region, but substantially reduces the instability magnitude. Varying the pin torsional damping reduces the unstable region, but has little effect on the instability magnitude.

An overview of performance measures for heavy commercial vehicles in north america.

Abstract: In recent studies, it has become apparent that a set of safety–related performance measures for heavy vehicles can be useful in the design process as well as in the more conventional realm of screening heavy vehicles by regulation. In Canada, these regulations control, separately, the combined trailer length and overall vehicle length, total vehicle weight, maximum axle–load, multiple–axle group spacing, and the characteristics of a few selected components of new vehicles (e.g. service and emergency air and/or hydraulic brake systems). None of the existing regulations has been applied for quantifying the dynamic properties of individual vehicles, either newly designed or already in service; instead they have been used to qualify classes or groupings of vehicles. The objective of this paper is to present an overview of the efforts made in North America to develop a set of safety–related performance measures and promote their use for determining and controlling the dynamic quality of heavy vehicles on an individual basis from both the design and regulatory standpoints.

Overview of electric machines for electric and hybrid vehicles

Abstract: This invited paper gives an overview of various electric machines for application to Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs). First of all, the classification and a brief introduction of EVs and HEVs are presented. Then, viable electric machines that have been applied to EVs and HEVs, including the DC, induction, Switched Reluctance (SR) and Permanent Magnet (PM) brushless types, are reviewed. Consequently, the advanced PM machines that are promising for application to EVs and HEVs are discussed. Finally, the integrated PM machines are introduced, which are essential for future EVs and HEVs.

Modelling of road profiles using roughness indicators

Abstract: The vertical road input is the most important load for durability assessments of vehicles. We focus on stochastic modelling of the road profile with the aim to find a simple but still useful model. The proposed nonstationary Laplace model with ISO spectrum has only two parameters, and can be efficiently estimated from a sequence of roughness indicators, such as IRI or ISO roughness coefficient. Thus, a road profile can be stochastically reconstructed from roughness indicators. Further, explicit approximations for the fatigue damage due to Laplace roads are developed. The usefulness of the proposed Laplace-ISO model is validated for eight measured road profiles.

Neural network and fuzzy logic applications to vehicle systems: literature survey

Abstract: Recent developments in the application of the artificial neural networks (NN) and fuzzy logic (FL) have attracted the attention of many researchers in the area of vehicle dynamics and control. Neural networks are able to emulate the solution of different classes of nonlinear algebraic equations and differential transfer functions. Fuzzy logic interface systems can map those functions that have no equivalent mathematical model or whose mathematical models are very complicated. A large number of studies have been published on the application of neural networks and fuzzy logic interface systems to vehicle dynamics and control. In this paper, an extensive literature survey of more than forty papers and reports, published during the last five years, has been conducted. Reviewed papers cover different subjects including: vehicle motion control, driver modelling, tyre modelling, braking control, suspension control, steering system, transmission control, and engine control. This literature review is part of an ongoing research project related to the application of neural networks and fuzzy logic to vehicle dynamics and control.

Comparative assessment of European tools to estimate traffic emissions

Abstract: Four models used to calculate motor vehicle emissions across Europe (Handbook of Emission Factors, Drive–Modem model, Digitalized Graz Method and Computer Programme to Calculate Emissions from Road Traffic) are compared. The focus is on their methods for the estimation of emissions of passenger cars. By using driving profile data from real–world recordings in urban streets as well as general emission functions, the results obtained from the four models are presented and discussed. Furthermore, on the basis of relevant investigations conducted in Europe, including this one, a number of critical vehicle emission modelling issues are discussed: (i) whether detailed methodologies lead indeed to improved emission estimates, (ii) how refined vehicle emission models have to be for use in different applications, and (iii) if it is possible to have one method and model for estimating vehicle emissions in any type of application.

Handling performance of truck–trailer vehicles: A state–of–the–art survey

Abstract: This paper reviews the state of theoretical and experimental research relative to the handling performance of truck–trailer vehicles. Seventy articles have been reviewed for this purpose. The survey comprises three major sections corresponding to the traditional classification of vehicle handling performance: directional performance, braking performance and combined directional and braking performance. Under certain circumstances the truck–trailer vehicles can be prone to dangerous behaviour: snaking, jack–knifing, trailer swing. Down to the present day the research of such risky driving situations does not appear to have brought satisfactory results. The analyses that have been performed offer only a few general recommendations (some of them rather contradictory). However, no absolute values are encountered. Important theoretical papers are scarce and systematical experimental research seems to be sporadic. There are few comparisons between theoretical and experimental results. Investigations of the influence of the driver upon the behaviour of the whole system (driver - articulated vehicle - road) are totally absent. This paper concludes with some recommendations for future research consistent with the findings of the review.

A friction circle concept for dugoff's tyre friction model

Abstract: This paper presents a method of simplifying the calculations required when Dugoff's tyre friction model is used for simulation purposes. It also provides a physical interpretation in that it brings to light an idea similar to the traditional friction circle concept implicit in Dugoff's model. The procedure for calculating the tyre forces is presented, together with a flow chart for use in preparing a suitable computer model.

Sliding mode wheel slip controller for an antilock braking system

Abstract: A nonlinear control system that combines a sliding mode based optimiser and a proportional–plus–integral–plus–derivative (PID) controller is presented for a vehicle antilock brake system. The sliding mode optimiser performs an on–line search for the optimal wheel slip that corresponds to the vehicle's maximum deceleration. The PID controller and the sliding mode optimiser are coupled to regulate the vehicle's brake torque to control the wheel slip to its optimal value. The performance of the proposed control schemes is illustrated with simulation examples.

Determinants of US passenger car weight

Abstract: After a precipitous drop from 1976–1982, the weight of US passenger cars has grown steadily. This article examines multiple conflicting influences on vehicle weight in two categories: technological changes that reduce vehicle weight and improvements in functionality that, ceteris paribus, add to vehicle weight. The widespread adoption of unibody construction, lightweight materials and smaller engines has been offset by growth in vehicle size and feature content. The best estimates from this work indicate that new features and functionality would have added at least 250 kg (550 lbs) to the weight of the average new car between 1975 and 2009, if not for offsetting improvements in technology. Over the same period, it is estimated that alternative materials, more weight-efficient vehicle architectures and reduced engine sizes have taken 790 kg (1700 lbs) out of the weight of the average car. These observable influences do not explain the full extent of the drop and subsequent growth in weight, suggesting that substantial non-observed technological improvements were made from 1976–1982 and that unobserved improvements in areas such as crashworthiness and NVH have added substantially to vehicle weight in the past two decades.

On fuel-optimal velocity control of a motor vehicle

Abstract: This paper presents the motor vehicle velocity control that, under certain well–defined conditions, ensures a minimum fuel consumption. To this purpose, a vehicle with a stepped mechanical transmission is considered, assuming that the gear is unchanged during the movement. The optimal control problem is formulated for different cases and solved by applying Pontryagin's maximum principle. Whenever there is a singular solution, it is shown to correspond to the uniform motion law. The optimal velocity controls include the following phases that may be combined in different ways: deceleration without engine shut–off (null engine power), strong decelerative braking, constant speed movement and full–throttle acceleration. Examples are presented by using the experimental data on engine fuel consumption. The stress falls on the significant reductions in fuel consumption that can be achieved compared to uniform motion.

Intelligent control of clutch judder and shunt phenomena in vehicle drivelines

Abstract: In the area of vehicle refinement, noise and vibrations associated with the driveline have been important sources of problems. Such noise and vibration phenomena are subjectively associated with judder, harshness or 'lack–of–refinement' complaints by customers. In a mathematical analysis, it is shown how friction gradient coefficient, effective system damping, clutch and driveline compliances, clutch engagement details and other driveline parameters affect the overall driveline behaviour. Particular problems are associated with clutch judder and torsional vibration instabilities during start–off or gear change manoeuvres. With the recent interest in automatic control of manual gearboxes, clutchless–shift systems and clutch modulation during take–up, it is shown that it should be possible in principle to avoid such refinement problems by controlling the clutch modulation using robust and adaptive control algorithms.

Theoretical and experimental studies on the dynamic properties of tyres. part 1: review of theories of rubber friction

Abstract: This research has been divided into four parts for the purpose of serial publication in the International Journal of Vehicle Design. For the sake of completeness the abstracts for all four parts are given here. Part 1: Review of theories of rubber friction. Previous theoretical work on the dynamic properties of tyres is reviewed. Extensions of a theory relating tyre cornering properties to conditions of braking and traction are considered, along with factors relevant to a further extension to the dynamic properties of an actual pneumatic tyre. A theoretical derivation of the six components of force and moment generated in a tyre is given which involves integrating the vertical and friction forces acting on a rubber block and the resultant moments over the area of contact. Part 2: Experimental investigations of rubber friction and deformation of a tyre. Experiments designed to determine the basic properties of a tyre needed for the calculation of the six components of force and moment are described. Similar consideration is then given to experiments aimed at determining the frictional properties needed for the calculation of the six components. Part 3: Calculation of the six components of force and moment of a tyre. The method of calculating the six components of force and moment generated in a tyre is presented, and then applied. Partial results of the calculation are presented. Part 4: Influence of running conditions on the calculations and experiments. The results of calculations performed in previous sections of the paper are applied to the study of the influence of running conditions on the six components of force and moment in the case of real tyres. An experiment to determine the six components is described, and the experimental values compared with the calculated values.

Component sensitivity analysis of conceptual vehicle body for lightweight design under static and dynamic stiffness demands

Abstract: At conceptual design stage, engineers mostly rely on their experience, intuition, and data accumulation when making decisions on conceptual vehicle body (CVB). This paper presents a component sensitivity method for the lightweight design of the CVB. Firstly, CVB is simplified as a frame structure consisting of box beams. Secondly, torsional stiffness, bending stiffness and frequencies are adopted to evaluate the global stiffness performances of the CVB frame. Thirdly, component sensitivity formulas are derived. Fourthly, two application examples of car and bus frame verify that the proposed method is efficient to guide the cross-sectional sizes modification. The sufficient condition to obtain positive frequency sensitivity is also discussed. And finally Vehicle Body-FDO software is released for free to implement this method.

Game theory based autonomous vehicles operation

Abstract: In this paper, we propose a game theory based approach to decision making with application to the operation of autonomous ground vehicles in highway setting. The mixed-motive game theory is utilised as a decisionmaking strategy in the context of a two-player game involving autonomous vehicles. The payoff matrices are defined by considering the safety of each player’s decision combination in view of their desire to stay within a given lane or to change lanes in consideration of the traffic conditions that the vehicles encounter. By analysing the payoff matrix, either a pure (deterministic)strategy or a mixed (probabilistic) strategy is selected. Three 10 km velocity profiles are predefined for simulation purposes. The simulation results demonstrate effective driving performance. In particular when it is compared with non-game theory cases, game theory based results show larger payoff for both vehicles and smaller payoff differences, securing safe manoeuvring via lane change manoeuvre (LCM) and adaptive cruise control (ACC).

Optimisation of geometry and material properties of a non-pneumatic tyre for reducing rolling resistance

Abstract: The effect of geometric and material parameters of a non-pneumatic tyre (NPT) on overall performance of the NPT is investigated. Parametric studies, design of experiments (DOE), and sensitivity analyses are conducted with a hyper-viscoelastic finite element model to determine effects of design variables: i) the thickness of spokes; ii) the shear band thickness and iii) shear modulus of polyurethane (PU), on rolling resistance, vertical stiffness, and contact pressure. A response surface model is generated from DOE and is used to find optimum design values for minimising rolling resistance of an NPT under constraints on vertical deflection and contact pressure. Shear modulus of PU and the shear band thickness are the most important design parameters to affect rolling resistance, vertical stiffness, and contact pressure. The optimised values show that the NPT has low rolling resistance with a higher shear modulus of PU and a higher shear band thickness associated with a lower shear deformation while rolling.

Development of a driving cycle for the prediction of pollutant emissions and fuel consumption

Abstract: In this study, a methodology has been developed for obtaining a driving cycle from the measured data in actual traffic conditions. Vehicle speed transition matrices formed from the measured data are used in two stages to obtain a representative speed–time history for the route in consideration minimizing the deviation from average values for vehicle speed, acceleration and acceleration in relation to speed. Sample calculations have been performed indicating reasonable results.

Conceptual framework for integrating technology into business strategy

Abstract: This paper focuses on the ways that commercial and technology managers communicate as companies try to be more successful in managing technology for growth and competitive advantage. A framework is presented that provides an explicit and systematic way to integrate the different perspectives in the planning process. The framework focuses on the key questions involved in formulating an 'overall business strategy', in determining the 'strategic context' for examining a variety of 'technological considerations' and for transforming judgments about technologies into an examination of the 'strategic implications' for the firm. Once a business strategy emerges from this iterative process, the elements of a technology strategy can be derived. Within this framework, a variety of techniques can be used to generate questions, structure answers, and focus on options and trade–offs.

Structural optimization with aeroelastic constraints: a survey of US applications

Abstract: The paper describes recent developments in the United States in the application of structural optimization techniques to problems of design under aeroelastic constraints. In particular, the following topics are discussed: (i) conventional–strength design using aeroelastically calculated loads; (ii) aeroelastic tailoring for improved performance; (iii) design under flutter and static aeroelastic constraints; and (iv) miscellaneous applications. Because of the high cost of applying formal optimization techniques to practical design problems, there have been very few applications of structural optimizations to actual aircraft. The paper is focused on trends that may eventually reverse this situation.

The present and future of electric power steering

Abstract: Recently electric power steering systems have been developed and are now provided in production vehicles. Electric power steering systems provide the driver with the correct steering assistance from an electric motor, calculated by the CPU from both vehicle velocity and input steering torque. In this paper, electric power steering systems will be described, and particularly their features, major components, performance and expected future trends.

Robust design of active suspension system

Abstract: In this paper, the authors deal with some new control design methods of the control system used in active wheel suspension. Applicability of H∞ control in case of the active suspension system is examined still using the familiar quarter–car model. The robust control problem is solved in case of direct state–feedback H∞ and in the presence of structured (parametric) uncertainties solving the RLQR design task. The authors solve the joint H∞/RLQR problem proving the trade–off between the external disturbance rejection (road irregularities) and the internal disturbance attenuation arising from the parametric uncertainties.

Profiling of rough terrain

Abstract: This study concentrates on obtaining profiles of rough terrain suitable for vehicle dynamics simulations in a cost–effective manner. Commercially available inertial profilometers are unable to profile the terrains of interest due to their severe roughness. A mechanical profilometer is developed and evaluated by profiling obstacles with known profiles, as well as rough 3-D test track profiles. A good correlation between the profiled and actual terrains is achieved. Realistic three-dimensional (3-D) terrain models are generated from the terrain profiles. The Displacement Spectral Densities (DSDs) of the profiled terrains are found to contain discrete peaks; a straight line fit would not be an accurate estimation for the specific rough terrains. Comparisons between the terrains defined in the International Roughness Index (IRI) and the present study indicate that the roughness index of the terrains profiled with the mechanical profilometer is significantly higher than the terrains normally profiled by inertial profilometers.

Fuzzy logic control of vehicle suspension systems.

Abstract: Passenger ride comfort has been one of the major issues of vehicle design. The most efficient way of achieving better ride quality is to improve the control of vehicle suspension systems. This paper focuses on developing a robust control algorithm for vehicle suspension systems which can handle a wide range of road roughness as well as mechanical variances of suspension systems while providing a comfort ride. Specifically, a model reference self–tuning fuzzy logic control scheme which consists of a primary and a secondary controller is proposed. The primary controller performs the major control function of the actual sprung mass acceleration. The secondary controller, however, is used to tune the output membership function of the primary fuzzy logic controller on line such that it is capable of adapting process variations such as sprung mass change, spring and damper rate variations and harsh road conditions. The simulation results show that the proposed fuzzy logic controller can make the active suspension system accommodate normal road condition variations and provide near–zero sprung mass acceleration, which in turn yields good quality ride. The comparison study through simulation also demonstrates the superior robustness of the proposed controller over the conventional controller for active vehicle suspension systems.

Optimizing the design of a hydrogen engine with pilot diesel fuel ignition

Abstract: A diesel engine was converted to dual–fuel hydrogen operation, ignition being started by a 'pilot' quantity of diesel fuel but with 65 to 90% of the energy being supplied as hydrogen. With later injection timing, use of delayed port admission of the gas, and a modified combustion chamber, thermal efficiencies were achieved nearly 15% greater than those for diesel as the sole fuel. A 'solid' water injection technique was used to curb knock under full load conditions when the power output equalled or exceeded that of a similar diesel engine. The indicator diagrams under these conditions closely approach those of the Otto cycle. The development was assisted by computer simulation using a novel self–ignition and flame propagation model. The very fast burning rates obtained with stoichiometric hydrogen–air mixtures show combustion to occur within 5 degrees of crank rotation yet Otto cycle thermal efficiency was not achieved. However, greenhouse gases are shown to be reduced by more than 80%, nitrogen oxides by up to 70%, and exhaust smoke by nearly 80%.