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Viewing 1 to 30 of 3200
2010-09-28
Technical Paper
2010-32-0041
Jih Houh Lee, Horizon Gitano, Hock Seng Eu, Ahmad Syazli Mohd Khalil
Existing drive cycles do not correlate well with actual drive cycles in developing countries due to differences in vehicle mixes, and traffic flow patterns. Several distinct drive cycles were identified in Malaysia namely the urban, suburban, rural, highway and delivery drive cycles. Several methods were used in generating drive cycles including direct observation, motorcyclist surveys, vehicle shadowing with on-board wheel speed measurement and data logging. These drive cycles were compared to existing European, United States, world harmonized motorcycle drive cycles and evaluated for fuel consumption. Results indicate that the Malaysian drive cycles are capable predicting actual vehicle fuel mileage within +/− 10% for a wide range of vehicles, while the European drive cycle results in a 20%deviation from the actual vehicle fuel mileage.
2011-04-12
Technical Paper
2011-01-0436
Alejandra Paola Polanco, Luis Munoz
In this paper the comfort sensitivity to the variation of the inertia parameters is studied. For the theoretical approach, two computational models that predict the comfort response of a vehicle are developed and verified. These models are used to study the effect of a change on the inertial properties of the car on its comfort response. The models are developed on a commercial multi-body package and also implementing handwritten equations with a numerical integration algorithm. The influence of the inertial properties on comfort is also experimentally studied. Both approaches use two different road patterns as input generating a roll and pitch excitation. An allowed uncertainty on the inertia properties is proposed, based on the sensitivity to those properties.
2010-04-12
Technical Paper
2010-01-1140
Shawky Hegazy, Corina Sandu
This paper presents a six degree of freedom full vehicle model simulating the testing of heavy truck suspensions to evaluate the ride comfort and stability using actual characteristics of gas charged single tube shock absorbers. The model is developed using one of the commercial multi-body dynamics software packages, ADAMS. The model incorporates all sources of compliance: stiffness and damping with linear and non-linear characteristics. The front and the rear springs and dampers representing the suspension system were attached between the axles and the vehicle body. The front and the rear axles were attached to a wheel spindle assembly, which in turn was attached to the irregular drum wheel, simulating the road profile irregularities. As a result of the drum rotation, sudden vertical movements were induced in the vehicle suspension, due to the bumps and rebounds, thus simulating the road profile.
2010-04-12
Technical Paper
2010-01-1135
Krishna Prasad Balike, Subhash Rakheja, Ion Stiharu
Automotive suspensions invariably exhibit asymmetric damping properties in compression and rebound, which is partly attributed to asymmetric damping and in-part to the suspension linkage kinematics together with tire lateral compliance. Although automotive suspensions have invariably employed asymmetric damping, the design guidelines and particular rationale for such asymmetry has not been explicitly defined. The influences of damper asymmetry together with the suspension kinematics and tire lateral compliance on the dynamic responses of a vehicle are investigated analytically under bump and pothole excitations, and the results are interpreted in view of potential design guidance. A quarter-car kineto-dynamic model of the road vehicle employing a double wishbone type suspension comprising a strut with linear spring and multiphase asymmetric damper is formulated for the analyses.
2010-04-12
Technical Paper
2010-01-1139
Mike J. Johnston, Rob Rieveley, Jennifer Johrendt, Bruce Minaker
Though the purpose of a vehicle's suspension is multi-faceted and complex, the fundamentals may be simply stated: the suspension exists to provide the occupants with a tolerable ride, while simultaneously ensuring that the tires maintain good contact with the ground. At the root of the familiar ride/handling compromise, is the problem that tuning efforts which improve either grip or handling are generally to the detriment of the other. This study seeks to set forth a clear means for examining the familiar ride/handing compromise, by first exploring the key ideas of these terms, and then by describing the development of content-rich metrics to permit a direct optimization strategy. For simplicity, the optimization problem was examined in a unilateral manner, where heave (vertical; z-axis) behaviour is examined in isolation, though the methods described herein may be extended to pitch and roll behaviour as well.
2010-04-12
Technical Paper
2010-01-1138
Efthimio Duni, Giovanni Toniato, Raffaele Saponaro, Paolo Smeriglio, Vincenzo Puleo
This work describes a numerical methodology based on the Finite Element approach able to simulate the dynamic maneuver of the full vehicle running on fatigue reference roads. The basic idea of present work stays in combining a moderately complex and general finite element tire model with traditional full-vehicle methods, including both implicit and explicit finite element techniques, in order to predict the dynamic response of the car running on the real fatigue reference roads. Some issues related to application of tire finite element model to a long simulation time in an explicit solution have been discussed. The best integration strategy between implicit and explicit solutions, based on pure sequential and/or the combined sequential and co-simulation mode is discussed. The real fatigue load is digitalized and implemented as a rigid body in the explicit code.
2010-04-12
Technical Paper
2010-01-1137
Bhaskar Chaturvedi, Deepak Rana, Mugundaram Ravindran
In a highly competitive market, one of the major challenges for an automobile designer is to lower the product cost while improving the performance. Therefore, from the vehicle comfort point of view, achieving a good ride, handling and NVH performance, while satisfying the low cost and low weight target needs attention from the concept stage of the development cycle. To achieve this balance, it is important to optimize the static and dynamic stiffness of the vehicle body. This paper focuses on the effect of vehicle body stiffness on the ride, handling and NVH parameters. It also addresses the relation between static and dynamic stiffness of the vehicle. The correlation of the stiffness values with the ride, handling and NVH performance is also studied through various experiments on the actual vehicle
2010-04-12
Technical Paper
2010-01-1136
Seung-hoon Woo, Chang Su Kim, Choong kim
Various deformation shapes of the vehicle body were investigated for the purpose to establish vehicle body's performance criteria which correlates well to handling performance and ride comfort. Using CAE tool, the dynamic behavior of a structure by its modal parameter can be described instead of by its nodes and elements. Each modal characteristic in a dynamic system is reduced by its modal stiffness, its modal mass and its damping parameter in the model. This technology offers not only computational efficiency but also parametric model enabling easy what-if simulation. This reduced model can be obtained by modal test as well as simulation of full FE model. It was also investigated that which mode is sensitive to ride or handling performance using the parameterized model. The body stiffness of the brand new 2010 SONATA was improved on reference to the sensitivity analysis. The ride and handling performance of the 2010 SONATA were verified by computer simulation and vehicle field test
2010-12-01
Technical Paper
2010-01-1582
Joseph Maiorana, Bruce P. Minaker
In this study the capabilities of a semi-active suspension and an active roll suspension are evaluated for comparison with a passive suspension. The vehicle used is a utility truck modeled as a multi-body system in ADAMS/Car while the ECU (electronic control unit) is built in Matlab/Simulink. Cosimulation is used in linking the vehicle model with the controller by exchanging the input and output values of each sub-system with one another. For the simulation models considered, results indicate that for a fish-hook cornering maneuver the semi-active suspension is limited in increasing vehicle performance while the active roll suspension significantly improves it. Further analysis is needed to confirm these findings.
2010-04-12
Journal Article
2010-01-0513
Kenichi Ando, Akio Takamura, Isao Saito
Optimization methodology employing CFD for the aerodynamic design of automotive car styling is presented. The optimization process consists of three stages: Design of Experiments (DOE), Response Surface Modeling (RSM), and optimization algorithm execution. RSM requires a number of CFD calculations in order to ensure its accuracy, making it difficult to apply the RSM to aerodynamic design optimization. In order to resolve this issue, Adaptive Multi Stage RSM (AMS-RSM) was conceived. This method provided the response surface its required accuracy and robustness. The optimization process was realized by constructing an automatic optimization system consisting of software.
2010-04-12
Technical Paper
2010-01-0512
Y.A. Irving Brown, S. Windsor, A.P. Gaylard
Two methods of passive flow control were investigated to determine their effectiveness in reducing aerodynamic drag on large Sports Utility Vehicles (SUVs). Passive means of flow control were selected since all active methods require the input of additional energy (e.g., pressurized fluids or electrical energy). The selected methods were base bleed and the use of a rear cavity, and various combinations of these were experimentally tested in full-scale wind tunnels with and without a moving belt/rotating wheel assembly. Aerodynamic drag reduction was accomplished by restructuring the low-pressure wake directly behind the vehicle. External cavity depths ranging from d/h=0.17 to 0.83 were used, while body cavity depths ranged from d/h=0 to 0.83, where the depth of the cavity d is non-dimensionalized by the height h of the base area.
2010-04-12
Technical Paper
2010-01-0511
Taeyoung Han, Youngtae Kim
Aerodynamic forces are the result of various complex viscous flow phenomena such as three-dimensional turbulent boundary layer on the body surfaces, longitudinal vortices induced by three-dimensional boundary layer separation, and high turbulence caused by flow separations. Understanding the flow characteristics and, especially, how the aerodynamic forces are influenced by the changes in the vehicle body shape, are very important in order to improve vehicle aerodynamics (particularly for low drag shapes). The present study was an attempt to provide insights for better understanding of the complex three-dimensional flow field around a vehicle by observing the limiting surface streamlines and the surface pressure gradients in the stream-wise and the transverse directions. The main objective of this work is to provide a comprehensive diagnostic analysis of the basic flow features in order to learn more about the flow separations in three-dimensions.
2010-04-12
Technical Paper
2010-01-0510
Rob Littlewood, Martin Passmore
A large contribution to the aerodynamic drag of a vehicle is the loss of pressure in the wake region, especially on square-back configurations. Wake pressure recovery can be achieved by a variety of physical shape changes, but with vehicle shapes becoming ever more aerodynamically efficient research into active technologies for flow manipulation is becoming more prominent. The aim of the current paper is to generate an understanding of how an optimized roof trailing edge, in the form of a chamfer, can reduce wake size, increase base pressures and reduce drag. A comprehensive study using PIV (Particle Image Velocimetry), balance measurements and static pressure measurements was performed in order to investigate the flow and wake structure behind a simplified car model. Significant reductions in C d are demonstrated and directly related to the measured base and slant pressures.
2011-04-12
Technical Paper
2011-01-0182
Sujay J. Kawale, John B. Ferris
The accuracy of computer-based ground vehicle durability and ride quality simulations depends on accurate representation of road surface topology as vehicle excitation data since most of the excitation exerted on a vehicle as it traverses terrain is provided by the terrain topology. It is currently not efficient to obtain accurate terrain profile data of sufficient length to simulate the vehicle being driven over long distances. Hence, durability and ride quality evaluations of a vehicle depend mostly on data collected from physical tests. Such tests are both time consuming and expensive, and can only be performed near the end of a vehicle's design cycle. This paper covers the development of a methodology to synthesize terrain profile data based on the statistical analysis of physically measured terrain profile data.
2011-04-12
Technical Paper
2011-01-0177
Pascal Theissen, Johannes Wojciak, Kirstin Heuler, Rainer Demuth, Thomas Indinger, Nikolaus Adams
Unsteady aerodynamic flow phenomena are investigated in the wind tunnel by oscillating a realistic 50% scale model around its vertical axis. Thus the model is exposed to time-dependent flow conditions at realistic Reynolds and Strouhal numbers. Using this setup unsteady aerodynamic loads are observed to differ significantly from quasi-steady loads. In particular, the unsteady yaw moment exceeds the quasi-steady approximation by 80%. On the other hand, side force and roll moment are over predicted by quasi-steady approximation but exhibit a significant time delay. Using hotwire anemometry, a delayed reaction of the wake flow of Δt/T = 0.15 is observed, which is thought to be the principal cause for the differences between unsteady and quasi-steady aerodynamic loads. A schematic mechanism explaining these differences due to the delayed reaction of the wake flow is proposed.
2011-04-12
Journal Article
2011-01-0185
Michael W. Sayers
The major actions that move a highway vehicle are the forces and moments generated between the tire and ground; hence, the validity of a simulated vehicle test depends on the quality of both the tire model and the characterization of the ground surface. Other actions come from aerodynamic forces and moments that are affected by the relation of the vehicle body to the ground surface. This paper describes how the ground can be characterized to cover features of interest for most vehicle simulation scenarios involving pavements or other rigid surfaces. The 3D surface is built from tabular data related to specified properties of a road surface such as horizontal geometry, design elevation changes related to curves and drainage (i.e., banking of turns, cross-slope, ditches, etc.), elevation changes due to hills and other major grades, and disturbances and unique features such as bumps and holes. Broadband random-type road roughness is also included.
2011-04-12
Technical Paper
2011-01-0153
Makoto Tsubokura, See Yuan Cheng, Takuji Nakashima, Yoshihiro Okada, Takahide Nouzawa
We investigate the pitching stability characteristics of sedan-type vehicles using large-eddy simulation (LES) technique. Pitching oscillation is a commonly encountered phenomenon when a vehicle is running on a road. Attributed to the change in a vehicle's position during pitching, the flow field around it is altered accordingly. This causes a change in aerodynamic forces and moments exerted on the vehicle. The resulting vehicle's response is complex and assumed to be unsteady, which is too complicated to be interpreted in a conventional wind tunnel or using a numerical method that relies on the steady state solution. Hence, we developed an LES method for solving unsteady aerodynamic forces and moments acting on a vehicle during pitching. The pitching motion of a vehicle during LES was produced by using the arbitrary Lagrangian-Eulerian technique. We compared two simplified vehicle models representing actual sedan-type vehicles with different pitching stability characteristics.
2011-04-12
Journal Article
2011-01-0154
David Schroeck, Werner Krantz, Nils Widdecke, Jochen Wiedemann
In this paper the effect of aerodynamic modifications that influence the unsteady aerodynamic properties of a vehicle on the response of the closed loop system driver-vehicle under side wind conditions is investigated. In today's aerodynamic optimization the side wind sensitivity of a vehicle is determined from steady state values measured in the wind tunnel. There, the vehicle is rotated with respect to the wind tunnel flow to create an angle of attack. In this approach however, the gustiness that is inherent in natural wind is not reproduced. Further, unsteady forces and moments acting on the vehicle are not measured due to the limited dynamic response of the commonly used wind tunnel balances. Therefore, a new method is introduced, overcoming the shortcomings of the current steady state approach. The method consists of the reproduction of the properties of natural stochastic crosswind that are essential for the determination of the side wind sensitivity of a vehicle.
2011-04-12
Journal Article
2011-01-0160
Oliver Mankowski, David Sims-Williams, Robert Dominy, Bradley Duncan, Joaquin Gargoloff
A vehicle on the road encounters an unsteady flow due to turbulence in the natural wind, the unsteady wakes from other vehicles and as a result of traversing through the stationary wakes of road side obstacles. There is increasing concern about potential differences in aerodynamic behaviour measured in steady flow wind tunnel conditions and that which occurs for vehicles on the road. It is possible to introduce turbulence into the wind tunnel environment (e.g. by developing active turbulence generators) but on-road turbulence is wide ranging in terms of both its intensity and frequency and it would be beneficial to better understand what aspects of the turbulence are of greatest importance to the aerodynamic performance of vehicles. There has been significant recent work on the characterisation of turbulent airflow relevant to road vehicles. The simulation of this time-varying airflow is now becoming possible in wind tunnels and in CFD.
2011-04-12
Journal Article
2011-01-0159
Nicholas R. Oettle, David Sims-Williams, Robert Dominy, Charles Darlington, Claire Freeman
The in-cabin sound pressure level response of a vehicle in yawed wind conditions can differ significantly between the smooth flow conditions of the aeroacoustic wind tunnel and the higher turbulence, transient flow conditions experienced on the road. Previous research has shown that under low turbulence conditions there is close agreement between the variation with yaw of in-cabin sound pressure level on the road and in the wind tunnel. However, under transient conditions, sound pressure levels on the road were found to show a smaller increase due to yaw than predicted by the wind tunnel, specifically near the leeward sideglass region. The research presented here investigates the links between transient flow and aeroacoustics. The effect of small geometry changes upon the aeroacoustic response of the vehicle has been investigated.
2011-04-12
Technical Paper
2011-01-0164
Johannes Wojciak, Pascal Theissen, Kirstin Heuler, Thomas Indinger, Nikolaus Adams, Rainer Demuth
Unsteady aerodynamic flow phenomena are investigated in a wind tunnel by oscillating a realistic 50% scale model around the vertical axis. Thus the model is exposed to time-dependent flow conditions at realistic Reynolds and Strouhal numbers. Using this setup unsteady aerodynamic loads are observed to differ significantly from quasi steady loads. In particular, the unsteady yaw moment exceeds the quasi steady approximation significantly. On the other hand, side force and roll moment are over predicted by quasi steady approximation but exhibit a significant time delay. Part 2 of this study proves that a delayed and enhanced response of the surface pressures at the rear side of the vehicle is responsible for the differences between unsteady and quasi steady loads. The pressure changes at the vehicle front, however, are shown to have similar amplitudes and almost no phase shift compared to quasi steady flow conditions.
2011-04-12
Technical Paper
2011-01-0090
Wei Liu, Wenku Shi Sr
In this paper, a Magneto-Rheological (MR) fluid semi-active suspension system was tested on a commercial vehicle, a domestic light bus, to determine the performance improvements compared to passive suspensions. MR fluid is a material that responds to an applied magnetic field with a significant change in its rheological behavior. When the magnetic field is applied, the properties of such a fluid can change from a free-flowing, low viscosity fluid to a near solid, and this change in properties takes place in a few milliseconds and is fully reversible. A quarter suspension test rig was built out to test the nonlinear performance of MR damper. Based on a large number of experimental data, a phenomenological model of MR damper based on the Bouc-Wen hysteresis model was adopted to predict both the force-displacement behavior and the complex nonlinear force-velocity response.
2011-04-12
Journal Article
2011-01-0058
Giles Bryer, Christopher Eccles
As mass reduction becomes an increasingly important enabler for fuel economy improvement, having a robust structural development process that can comprehend Vehicle Dynamics-specific requirements is correspondingly important. There is a correlation between the stiffness of the body structure and the performance of the vehicle when evaluated for ride and handling. However, an unconstrained approach to body stiffening will result in an overly-massive body structure. In this paper, the authors employ loads generated from simulation of quasi-static and dynamic vehicle events in ADAMS, and exercise structural finite element models to recover displacements and deflected shapes. In doing so, a quantitative basis for considering structural vehicle dynamics requirements can be established early in the design/development process.
2010-04-12
Technical Paper
2010-01-0757
Vyankatesh Bagal, Aditya Mulemane
Aerodynamic simulation using commercial CFD (Computational Fluid Dynamics) codes is now an integral part of the vehicle design process. Aerodynamic prediction and vehicle development program runs in parallel. This requires a good agreement between experimental measurements and CFD prediction of aerodynamic behavior of a vehicle. The comparison between experimental and simulation results show differences, as it may not be possible to replicate effect of all the wind tunnel parameters in the simulation. This paper presents the details of aerodynamic simulation process of a Crossover and its validation with the experimental results available from the wind tunnel tests. The results are compared for different configurations such as- closing the grille openings, removing the rearview mirror, adding ski-rack and using different tyres. This study also includes the effect of different wind speeds and yaw angles on the coefficient of drag.
2010-04-12
Technical Paper
2010-01-0756
Bradley D. Duncan, Satheesh Kandasamy, Khaled Sbeih, Todd H. Lounsberry, Mark E. Gleason
In an environment of tougher engineering constraints to deliver tomorrow's aerodynamic vehicles, evaluation of aerodynamics early in the design process using digital prototypes and simulation tools has become more crucial for meeting cost and performance targets. Engineering needs have increased the demands on simulation software to provide robust solutions under a range of operating conditions and with detailed geometry representation. In this paper the application of simulation tools to wheel design in on-road operating conditions is explored. Typically, wheel and wheel cover design is investigated using physical tests very late in the development process, and requires costly testing of many sets of wheels in an on-road testing environment (either coast-down testing or a moving-ground wind-tunnel).
2010-04-12
Journal Article
2010-01-0758
Emmanuel Guilmineau
This paper presents a finite-volume-based detached-eddy simulation for the prediction of flow around a passenger vehicle. The flow solver used is ISIS-CFD developed by the CFD Department of the Fluid Mechanics Laboratory of Ecole Centrale de Nantes. The validation is carried out by a crosswind simulation around the squareback Willy model. The model was designed in order that separations are limited to the region of the base for a moderate yaw angle. This model without sharp corners on the fore body and a square base is more convenient for the analysis of unsteady separations limited on its leeward side and base. The angle between the upstream velocity and the direction of the model varies between 0° and 30°. The results are compared to a previous numerical study obtained with a RANS simulation and experimental data.
2010-04-12
Technical Paper
2010-01-0760
Oliver Fischer, Timo Kuthada, Edzard Mercker, Jochen Wiedemann, Bradley Duncan
Previous work by the authors showed the development of an aerodynamic CFD model using the Lattice Boltzmann Method for simulating vehicles inside the IVK Model-Scale Wind-Tunnel test-section. In both experiment and simulation, alternate configurations of the wind-tunnel geometry were studied to change the pressure distribution in the wind-tunnel test section, inducing a reduction in aerodynamic drag due to interference between the wind-tunnel geometry and the pressure on the surface of the vehicle. The wind-tunnel pressure distribution was modified by adding so-called “stagnation bodies” inside the collector to create blockage and to increase the pressure in the rear portion of the test section. The primary purpose of previous work was to provide a validated CFD approach for modeling wind-tunnel interference effects, so that these effects can be understood and accounted for when designing vehicles.
2010-04-12
Technical Paper
2010-01-0755
Christoffer Landström, Tim Walker, Lennart Löfdahl
Automotive wind tunnel testing is a key element in the development of the aerodynamics of road vehicles. Continuous advancements are made in order to decrease the differences between actual on-road conditions and wind tunnel test properties and the importance of ground simulation with relative motion of the ground and rotating wheels has been the topic of several studies. This work presents a study on the effect of active ground simulation, using moving ground and rotating wheels, on the aerodynamic coefficients on a passenger car in yawed conditions. Most of the published studies on the effects of ground simulation cover only zero yaw conditions and only a few earlier investigations covering ground simulation during yaw were found in the existing literature and all considered simplified models. To further investigate this, a study on a full size sedan type vehicle of production status was performed in the Volvo Aerodynamic Wind Tunnel.
2013-04-08
Technical Paper
2013-01-1355
Ibrahim Badiru, W. Bradley Cwycyshyn
This paper discusses subjective and objective approaches to quantifying ride performance in three sections: (1) Separates overall ride quality into five components-impact feel, shake, isolation, motion control, and smoothness; (2) Discusses approaches to objectively quantifying ride performance; (3) Provides analytical and test data to illustrate trade-offs in performance between the components of ride. The final section of this paper presents customer clinic data indicating customer preferences for the trade-off balance between ride performance attributes, specifically motion control versus smoothness.
2013-04-08
Technical Paper
2013-01-1354
Wenguang Wu, Zhengqi Gu
Electric wheel dump trucks are mainly used in open pit mines, where the working environment is very harsh and the driver's continuous working time is extremely long, therefore, the ride comfort of the truck is pretty important. This paper evaluates and optimizes the ride comfort, according to ISO2631, and Chinese standard GB/T4970-1996 and Chinese standard QC/T76.8-1993, while the ride comfort test had been done in a open pit mine. After the test data was analyzed, the results showed that the ride comfort of this truck needs to be improved and optimized. The multi-body system dynamic model was built in MATLAB/SIMULINK for this dump truck, to simulate the realistic working condition using a D-class road, which was reconstructed according to ISO/DIS8608 and Chinese standard GB7031-86, while the simulation results were in coincidence with the test ones.
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