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Dissertations / Theses on the topic 'Aerodynamics of road vehicles'
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1
Peters, Brett. "On Accelerating Road Vehicle Aerodynamics." Thesis, The University of North Carolina at Charlotte, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10791882.
Full textAbstract:
Road vehicle aerodynamics are primarily focused on developing and modeling performance at steady-state conditions, although this does not fully encompass the entire operating envelope. Considerable vehicle acceleration and deceleration occurs during operation, either because of driver input or from transient weather phenomenon such as wind gusting. With this considered, high performance road vehicles experience body acceleration rates well beyond ±1G to navigate courses during efficient transition in and out of corners, accelerating from maximum straight-line speed to manageable cornering speeds, and then back to maximum straight-line speed. This dissertation aims to answer if longitudinal acceleration is important for road vehicle aerodynamics with the use of transient Computational Fluid Dynamics (CFD) to develop a method for obtaining ensemble averages of forces and flow field variables. This method was developed on a simplified bluff body, a channel mounted square cylinder, achieving acceleration through periodic forcing of far field velocity conditions. Then, the method was applied to an open-source road vehicle geometry, the DrivAer model, and a high performance model which was created for this dissertation, the DrivAer-GrandTouringRacing (GTR) variant, as a test model that generates considerable downforce with low ground proximity. Each test body experienced drag force variations greater than ±10% at the tested velocities and acceleration rates with considerable variations to flow field distributions. Finally, an empirical formulation was used to obtain non-dimensional coefficients for each body from their simulated force data, allowing for force comparison between geometries and modeling of aerodynamic force response to accelerating vehicle conditions.
2
Shah, Nawazish A. "Boundary element methods for road vehicle aerodynamics." Thesis, Loughborough University, 1985. https://dspace.lboro.ac.uk/2134/26942.
Full textAbstract:
The technique of the boundary element method consists of subdividing the boundary of the field of a function into a series of discrete elements, over which the function can vary. This technique offers important advantages over domain type solutions such as finite elements and finite differences. One of the most important features of the method is the much smaller system of equations and the considerable reduction in data required to run a program. Furthermore, the method is well-suited to problems with an infinite domain. Boundary element methods can be formulated using two different approaches called the ‘direct' and the ‘indirect' methods.
3
Robinson, Christopher M. E. "Advanced CFD modelling of road-vehicle aerodynamics." Thesis, University of Manchester, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488031.
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4
Forbes, David C. "Coupling road vehicle aerodynamics and dynamics in simulation." Thesis, Loughborough University, 2017. https://dspace.lboro.ac.uk/2134/25565.
Full textAbstract:
A fully coupled system in which a vehicle s aerodynamic and handling responses can be simulated has been designed and evaluated using a severe crosswind test. Simulations of this type provide vehicle manufacturers with a useful alternative to on road tests, which are usually performed at a late stage in the development process with a proto- type vehicle. The proposed simulations could be performed much earlier and help to identify and resolve any aerodynamic sensitivities and safety concerns before significant resources are place in the design. It was shown that for the simulation of an artificial, on-track crosswind event, the use of the fully coupled system was unnecessary. A simplified, one-way coupled system, in which there is no feedback from the vehicle s dynamics to the aerodynamic simulation was sufficient in order to capture the vehicle s path deviation. The realistic properties of the vehicle and accurately calibrated driver model prevented any large attitude changes whilst immersed in the gust, from which variations to the aerodynamics could arise. It was suggested that this system may be more suited to other vehicle geometries more sensitive to yaw motions or applications where a high positional accuracy of the vehicle is required.
5
Littlewood, Rob. "Novel methods of drag reduction for squareback road vehicles." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12534.
Full textAbstract:
Road vehicles are still largely a consumer product and as such the styling of a vehicle becomes a significant factor in how commercially successful a vehicle will become. The influence of styling combined with the numerous other factors to consider in a vehicle development programme means that the optimum aerodynamic package is not possible in real world applications. Aerodynamicists are continually looking for more discrete and innovative ways to reduce the drag of a vehicle. The current thesis adds to this work by investigating the influence of active flow control devices on the aerodynamic drag of square back style road vehicles. A number of different types of flow control are reviewed and the performance of synthetic jets and pulsed jets are investigated on a simple 2D cylinder flow case experimentally. A simplified ¼ scale vehicle model is equipped with active flow control actuators and their effects on the body drag investigated. The influence of the global wake size and the smaller scale in-wake structures on vehicle drag is investigated and discussed. Modification of a large vortex structure in the lower half of the wake is found to be a dominant mechanism by which model base pressure can be influenced. The total gains in power available are calculated and the potential for incorporating active flow control devices in current road vehicles is reviewed. Due to practicality limitations the active flow control devices are currently ruled out for implementation on a road vehicle. The knowledge gained about the vehicle model wake flow topology is later used to create drag reductions using a simple and discrete passive device. The passive modifications act to support claims made about the influence of in wake structures on the global base pressures and vehicle drag. The devices are also tested at full scale where modifications to the vehicle body forces were also observed.
6
Mullarkey, Seamus Paul. "Aerodynamic stability of road vehicles in side winds and gusts." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/8683.
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7
Gumusluol, Unsal. "Experimental Investigation Of Aerodynamic Interactions Of Vehicles In Close Folowing And Passing Situations." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607287/index.pdf.
Full textAbstract:
In this Thesis study, aerodynamic interactions of vehicle models in close following and passing situations were investigated expeimentally. Effect of the inter-vehicle spacing and lateral distance on drag coefficients of two close-following vehicles were observed. Two different types of vehicle models were used in order to investigate the shape effect on aerodynamic vehicle interactions. Drag froces and surface pressures of the models at each situation were measured. Two different blockage correction methods on the basis of drag coefficient results were applied. Linear increments of drag coefficients were observed on leading and trailing MIRA models. Beacuse of their blunter shapes and sharp edges, the leading and trailing Ahmed Body models feel the presence of aerodynamic interactions substantially. The most important reduction in drag force occurs at the least vehicle spacing for both vehicle types. In the passing situations, it was observed that drag coefficients of MIRA models did not change considerably. However, big amount of changes were observed at all positions for Ahmed Body. Maximum values of drag coefficients were reached when the models were at side by side position for both vehicle types. In conclusion, it is possible to obtain more drag reductions with more numbers of vehicles in close-following. the lower drag coefficients in close-following operations caues to increase fuel savings and to reduce air pollution.
8
Pearson, William E. "The aerodynamic flow over a bluff body in ground proximity : CFD prediction of road vehicle aerodynamics using unstructured grids." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/16054.
Full textAbstract:
The prediction of external automobile aerodynamics using Computational Fluid Dynamics (CFD) is still in its infancy. The restrictions on grid size for practical use limit the ability of most organisations to predict the full flow over an automobile. Some insight into the flow over a passenger car can be made by examining the flow over a bluff body in close proximity to the ground. One such body is the Ahmed body composed of a rounded front, straight mid-section and variable slant-rear section. This body exhibits many of the 3D flow structures exhibited by passenger cars. The main feature of the flow around this body is the change in flow structure as the angle of the slant surface at the rear of the body is increased. The flow starts fully attached and ends fully separated. In between these two regimes is a third high drag regime. The flow structure is characterised by strong counter-rotating longitudinal vortices originating from the interaction between the flow from the sides and top of the body, and a small separation from the top/slant edge on the centre-plane of the body. The flow reattaches to the slant surface and the low-pressure fluid within the separation bubble increases the drag considerably. The use of CFD incorporating tine averaged statistical turbulence models to reproduce these flow patterns is assessed in this study. Initial work concentrated on evaluating structured grid methods for this flow type. Some success was achieved with the flow fields for the attached and fully separated cases but the third high drag regime was not predicted. The flow field also exhibited a grid dependent flow structure and drag result. To examine these effects further without high grid overheads an unstructured mesh generator was developed and used to provide meshes with more grid cells clustered around the body and it's wake. Analysis and refinement of the unstructured grids proved successful at removing the grid dependent flow field but still showed no evidence of the third high drag flow regime. Further, the bulk levels of drag in all cases was too high and the fully separated flow regime occurred too late in the slant surface angle sweep, coming at 40° instead of the 30° seen in the wind tunnel results. Further analysis of the flow field using highly refined mixed meshes showed no improvement in the drag or flow field prediction with the high drag flow field still not present. The use of higher order differencing schemes and anisotropic turbulence models reduced the drag levels considerably but not to the levels seen in the wind tunnel results. Comparison of the results from this work with the work of other authors is difficult for two reasons. Firstly, work on the specific body used in this thesis is sparse and, secondly, much of the work done by other authors was in conjunction with automotive manufacturers and details of the specific numerical methods employed are not available. The most important parallel conclusion from the work presented here and that of other authors is the inability of the CFD prediction to capture the change in flow mode as the angle of slant surface is increased. This failure can, in all probability, be attributed to the use of a steady-state CFD solution algorithm to capture the flow field around the body. A small possibility perhaps still exists that further grid refinement, very localised around the body, would help, but the detailed and careful predictions presented in this study make this highly unlikely. The most important piece of further work that could follow this work would therefore be the application of a time-accurate (unsteady) CFD solution algorithm to the bluff body in ground proximity problem. Whether these predictions should be of an unsteady RANS nature, or full LES predictions would be best answered by applying these methods to the present flow problem which is fundamental to the study of automobile aerodynamics.
9
Hamidy, Eghbal. "The structure of wakes of 3D bluff bodies in proximity to the ground." Thesis, Imperial College London, 1991. http://hdl.handle.net/10044/1/7603.
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10
Newnham, P. S. "The influence of turbulence on the aerodynamic optimisation of bluff body road vehicles." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/14381.
Full textAbstract:
In order to promote further understanding of the effects of the atmospheric environment encountered by road vehicles in the real world, a wind tunnel based investigation was conducted into the effect of small scale turbulence on the road vehicle optimisation process. An initial investigation was carried out using a I-box model with variable leading edge radii from 10mm to 100mm. Measurements of time averaged forces were made over a range of Reynolds numbers from 200,000 to 1,300,000 (based on the square root of frontal area) and free stream turbulence levels from 0.2% to 5.1%. The transcritical Reynolds number based on edge radius was established as a basis for comparison between turbulence levels. Centreline pressures and PlV vector fields are presented to provide information on separation and reattachment. The investigation was extended to a more representative 2-box model using the same radii as before and a reference model at full scale, where the edge radii varied from 25mm to 150mm and turbulence intensity from 1.8% to 4.3%. It was shown that there is a strong reduction of separation under increased turbulence, and a small increase in skin friction. A further experiment was carried out to investigate the influence of freestream turbulence on the characteristic effect of changing backIight angle on lift and drag. It is shown that there was a reduction in drag due to the action of turbulence on the separation over the backIight, which may be driven by an effect on vortex strength. Tests were also carried out on two full scale vehicles to investigate the effect of increasing turbulence intensity on front and rear spoilers, cooling drag, and A-pillar vortex flows. The observed changes were small but would often be cumulative in their effect, so that optimising a vehicle in a significantly different turbulence level could produce a difference in the total forces acting on the vehicle. These experiments have shown that the primary effect of the additional freestream turbulence introduced by grids is on the boundary layer, as was expected from the literature. The results showed that increasing the turbulence intensity made separated regions smaller, and suggested that vortices become weaker and less well defined. The work provides a basis for continuing to investigate the effect of freestream turbulence on the process of optimising the aerodynamics of road vehicles.
11
Horký, Martin. "Měření aerodynamických charakteristik vozidla na základě jízdních testů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231526.
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12
Regner, Dominik. "Studie příčného rychlostního pole v blízkosti rotujícího kola s uvažováním vlivu nucené konvekce kotoučové brzdy." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-399576.
Full textAbstract:
The master thesis deals with the influence of a local change of temperature due to advection from disc brake to axial velocity field close to the rotating wheel of a car. The second goal is to set parameters applicable to various wheel discs and study of the influence of these parameters to aerodynamical properties of car and thermodynamical properties of the disc brake. The thesis is numerically executed in StarCCM+. The first part focuses on theoretical background about the numerical solution and current status of research. There are described disc parameters, geometry input and solver settings in the second part. The final part deals with a comparison of velocity fields for isothermal and thermodynamical model and evaluates the influence of parameters to velocity field, aerodynamical drag and thermodynamical performance of the brake.
13
Tastan, Umur. "Investigation Of Turbulence Models Used In Automotive Industry." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613626/index.pdf.
Full textAbstract:
In this studyreliability and performance of turbulence models used in CFD softwares to determine the aerodynamics of passenger cars, are tested and compared. In the analyses, drag forces acting on the car, pressure and velocity distributions and wake flow patterns are determined by using several turbulence models with a commercial software Fluent. Calculated results compared to the experimental results given in the literature. It is observed that, turbulence models give relatively reliable results for determining aerodynamic properties of the model car. Among the turbulence models, RNG k-&epsilon
and standard k-&omega
models stand one step ahead of the other models according to results.
14
Adams, Jordan. "The feasibility of a road vehicle mounted aerodynamic testing apparatus." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10004.
Full textAbstract:
A ground vehicle mounted aerodynamic testing apparatus has been identified as a candidate concept for a low-cost alternative to traditional techniques. This dissertation explores the feasibility of a ground vehicle based system by identifying physical and practical issues facing such a system. The focus is on the two most important physical problems facing the concept. These are: the ride dynamics of a vehicle as it traverses a road, and the extent of the distortion of the airflow around a vehicle. Each of these problems is quantified using approximate methods in order to estimate their influence on the testing of the aircraft in order to determine if the concept is workable.
15
Rodriguez, Romain. "Etude expérimentale de la dispersion de particules ultrafines dans le sillage de modèles simplifiés de véhicules automobiles." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0032/document.
Full textAbstract:
La pollution de l’air cause de près de 7 millions de décès annuels dans le monde. L’exposition aux Particules Ultrafines (PUF), polluants parmi les plus néfastes pour la santé, atteint ses niveaux les plus importants en milieu urbain, principalement dus au transport routier. Dans cette thèse, nous examinons les liens entre les champs de concentration en nombre des PUF émises à l'échappement dans le sillage de modèles simplifiés d'automobiles (corps d’Ahmed) et les propriétés de ces écoulements. Ces travaux permettent de mieux comprendre les niveaux d'exposition aux PUF auxquels sont soumis tous les usagers de la route à l’échelle du sillage du véhicule. Trois modèles simplifiés de véhicules ont été utilisés. Ils sont caractérisés par leur angle de lunette arrière permettant de reproduire en soufflerie les structures principales des écoulements de sillage automobile. A l’aide d’une méthode innovante de traitement des données, des mesures de vitesses acquises grâce à des techniques différentes (LDV/PIV) ont été analysées. Elles ont révélé que l’angle d’inclinaison de la lunette a un rôle déterminant sur la structure des écoulements de sillage. Par ailleurs, la comparaison avec les mesures des concentrations en nombre de PUF a permis de montrer que le volume de la structure torique de recirculation en proche culot, dépendant de la géométrie, a un impact majeur sur la dispersion des particules dans la direction verticale. Enfin, il est mis en évidence que les structures tourbillonnaires longitudinales existantes pour une inclinaison intermédiaire de la lunette ont un impact prépondérant sur la dispersion transversale ainsi que sur la symétrie des champs de concentrationAround 7 million worldwide annual death sare due to air pollution. Among all pollutants, UltrafineParticles (UFP) cause strong adverse effects. Due to road transport, UFP exposure reaches its most significant levels in urban areas. In this thesis, the aim is to assess the links between the wake flow properties of simplified car models(Ahmed bodies) and UFP number concentration fields due to exhaust emission. This study enables the knowledge about UFP exposure levels of all road users at vehicle wake scale to be better understood. Three simplified car models with three corresponding rear slant angles have been used in order to reproduce the principal wake structures of road vehicles in a wind tunnel. Thanks to an innovative data processing method, velocity measurements with two techniques(LDV/PIV) point out the major role of the rear slantangle on the model wake structures. Moreover, comparisons have been made with particle number concentration measurements of UFP in the wake of the same models. We highlighted the link between the volume of the toric recirculation region close to the rear and the vertical dispersion of UFP. Furthermore, longitudinal vortices that exist with the intermediate rear slant angle geometry play an important role on the transversal dispersion as well as on the concentration field symetry
16
Prachař, Roman. "Jízdní odpory vozidel." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-232514.
Full textAbstract:
his thesis deals with the analysis of particular road resistances that affect the car. It describes their importance and factors that influence their size. This thesis defines steps that determine particular quantities that are necessary to assess road resistances. Describing, it qualifies transfer and sizes of driving force that is needed to overcome total road resistance, measuring methods of road range tests upon appropriation of road resistances and influence of road resistances on economy of traffic. Practical part discusses the plan and course of realized measuring of selected sample of cars. Final part deals with the evaluation of measured values of realized measuring.
17
Chadwick, Andrew. "Crosswind aerodynamics of sports utility vehicles." Thesis, Cranfield University, 1999. http://hdl.handle.net/1826/2508.
Full textAbstract:
Crosswind gusts have a continuous influence on the ride and handling of road vehicles. At low speeds the effect is negligible but as both car and wind speeds increase there is a reduction in refinement, ride quality is degraded and it becomes tiring to drive. Future environmental legislation concerning the reduction of carbon dioxide emissions will lead to a lighter road vehicle and a corresponding increase in crosswind sensitivity.
The aerodynamicist's approach to understanding the fluid flow around a vehicle when subjected to a crosswind has conventionally been through steady state model tests where aerodynamic force and moment data are taken for different yaw angles. The accuracy of this data has previously been questioned because of a lack of simulation of the transient nature of the crosswind gust. Additionally, although force and moment data can tell the aerodynamicist which are the principle loads influencing a vehicles response in a crosswind, they fail to identify the specific regions on the vehicle that contribute to these aerodynamic loads. This can only be achieved by pressure mapping the model surface and although such a technique has been employed during steady state tests, no research has been presented with the correct modeling of the transient crosswind gust.
To gain an initial understanding of the complex time dependent and separated flow fields around bluff vehicles, such as sports utility vehicles, when subjected to a crosswind, aerodynamic force, moment and surface pressure data of simple geometric shapes has been collected on the Cranfield crosswind track facility. Steady state data has been obtained from conventional wind tunnel tests and compared with the transient data. Unique pressure animations identify the growth and collapse of vortices on the leeward face as the primary transient characteristic and which produce peak aerodynamic yawing moments up to double that seen in the steady state.
18
Zhang, Zheshuo. "Dynamics of road vehicles crossing rail-road intersections." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/132688/2/Zheshuo%20Zhang%20Thesis.pdf.
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This project was a step forward in redesigning level crossing for improved safety of level crossing infrastructure. A vehicle-tire-obstacle model capable of predicting the vehicle dynamic behaviour as well as the tire-obstacle contact forces was developed from basic equations of motion. The thesis investigated the profile of redesigned level crossing from the perspective of road vehicle dynamics including the safety risk to the occupant and the dislodgement risk of the freights in the road vehicles. It was shown that the redesigned level crossings can save lives and avoid damages to trains, road vehicles and the related infrastructure.
19
Allison, Duncan. "Longitudinal vibration of road vehicles." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284907.
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20
Minaker, Bruce P. "Active geometry suspension for road vehicles." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ59533.pdf.
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21
Hall, Jeremiah. "Low Reynolds number aerodynamics for micro aerial vehicles." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1448684.
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22
Favre, Tristan. "Aerodynamics simulations of ground vehicles in unsteady crosswind." Doctoral thesis, KTH, Aerodynamik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-50242.
Full textAbstract:
Ground vehicles, both on roads or on rail, are sensitive to crosswinds and the handling, travelling speeds or in some cases, safety can be affected. Full modelling of the crosswind stability of a vehicle is a demanding task as the nature of the disturbance, the wind gust, is complex and the aerodynamics, vehicle dynamics and driver reactions interact with each other. One of the objectives of this thesis, is to assess the aerodynamic response of simplified ground vehicles under sudden strong crosswind disturbances by using an advanced turbulence model. In the aerodynamic simulations, time-dependant boundary data have been used to introduce a deterministic wind gust model into the computational domain. This thesis covers the implementation of such gust models into Detached-Eddy Simulations (DES) and assesses the overall accuracy. Different type of grids, numerical setups and refinements are considered. Although the overall use of DES is seen suitable, further investigations can be foreseen on more challenging geometries. Two families of vehicle models have been studied. The first one, a box-like geometry, has been used to characterize the influence of the radius of curvature and benefited from unsteady experimental data for comparison. The second one, the Windsor model, has been used to understand the impact of the different rear designs. Noticeably, the different geometries tested have exhibited strong transients in the loads that can not be represented in pure steady crosswind conditions. The static coupling between aerodynamics and vehicle dynamics simulations enhances the comparisons of the aerodynamic designs. Also, it shows that the motion of the centre of pressure with respect the locations of the centre of gravity and the neutral steer point, is of prime interest to design vehicles that are less crosswind sensitive. Recommendations on the future work on crosswind sensitivity for ground vehicles are proposed at the end of this thesis.QC 20111206
crosswind stability and unsteady aerodynamics
23
Coleman, Simon Anthony. "The aerodynamics of ground vehicles in cross winds." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278349.
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24
Singh, Amarjit. "Experimental study of slender vehicles at hypersonic speeds." Thesis, Cranfield University, 1996. http://hdl.handle.net/1826/4257.
Full textAbstract:
An
experimental
investigation
of the hypersonic flow
over
(i)
a wing-body
configuration,
(ii)
a
hemi-spherically blunted
cone-cylinder
body
and
(iii)
a one-half-
power-law
body has been
conducted
for M,,
=
8.2
and
Re,,
=
9.35x104
per cm.
The
tests were performed at model
incidences,
a=0,5 and
10° for flap deflection
angles,
(3
=
0,5,15,
and
25° for the wing-body.
The incidence
ranged
from
-3
to 10° for the cone-
cylinder and
-5
to 15° for the power-law
body.
(i) The
schlieren pictures showing top and side views of the model
indicate that the
body
nose shock
does
not
intersect the wing throughout the range of a under
investigation. Detailed
pressure measurements on the lower
surface of the wing and
flap
along with the liquid
crystal pictures suggest that the body
nose shock
does
not strike
the flap
surfaces either.
The
wing
leading
edge shock
is found to be
attached at a=0
and
5° but detached
at a= 10°.
The liquid
crystal pictures and surface pressure measurements
indicated
attached
flow
on the lower
surface of the wing and
flap for 13
=0 and
5°
at all values of a under
test. However
at a=
0°,
as the flap
angle
is increased to 15° the flow
separates ahead of
the hinge line. As incidence is increased the boundary layer becomes transitional giving
rise to complex separation patterns around the flap hinge line.
The
spherically
blunted body
nose causes strong entropy
layer
effects over the
wing and the trailing edge
flap. A Navier-Stokes
solution
indicated
a thick entropy
layer
of approximately constant thickness all around the cylindrical section of the body
at zero
incidence. However,
at an
incidence
of
10° the layer tapers and
becomes thinner under
the body. The
surface pressure over the wing and the plateau pressure
for
separated
flow
was
found to increase from the root to the tip. This is
partly
because
of the decrease in
local Reynolds
number across the span,
however in the present case, entropy
layer
effects also affected separation.
The
entropy
layer
effects were
found to reduce the peak
pressures obtainable on the flap. The
peak pressures, over the portion of the flap
unaffected
by
entropy
layer
effects, could
be
estimated assuming quasi two dimensional
flow.
(ii) Force
measurements were made
for the blunted
cone-cylinder alone as well as
with the delta
wing, with trailing-edge flap,
attached to it. The lift, drag,
and pitching
moment characteristics
for the cone-cylinder agree reasonably well with the modified
Newtonian theory and the N-S
results.
The
addition of a wing to the cone-cylinder
body
increases the lift
as weil as the drag
coefficient
but there is
an overall
increase in the
lift/drag
ratio.
The deflection
of a
flap from 0° to 25° increases the lift
and
drag
coefficients at all the incidences tested. However, the lift/drag
ratio
is
reduced showing
the affects of separation over the wing.
The
experimental results on the wing-body are
compared with the theoretical estimates
based
upon two-dimensional shock-expansion
theory.
(iii) The lift,
and
drag
characteristics of a one-half-power-law
body
are compared
with other existing results.
The
addition of strakes to the power-law
body
are
found to
improve its
aerodynamic efficiency without any significant change
in its
pitching
moment characteristics.
25
Favre, Tristan. "Numerical Investigation of Unsteady Crosswind Aerodynamics for Ground Vehicles." Licentiate thesis, KTH, Aeronautical and Vehicle Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11311.
Full textAbstract:
Ground vehicles are subjected to crosswind from various origins such as weather, topography of the ambient environment (land, forest, tunnels, high bushes...) or surrounding traffic. The trend of lowering the weight of vehicles imposes a stronger need for understanding the coupling between crosswind stability, the vehicle external shape and the dynamic properties. Means for reducing fuel consumption of ground vehicles can also conflict with the handling and dynamic characteristics of the vehicle. Streamlined design of vehicle shapes to lower the drag can be a good example of this dilemma. If care is not taken, the streamlined shape can lead to an increase in yaw moment under crosswind conditions which results in a poor handling.
The development of numerical methods provides efficient tools to investigate these complex phenomena that are difficult to reproduce experimentally. Time accurate and scale resolving methods, like Detached-Eddy Simulations (DES), are particularly of interest, since they allow a better description of unsteady flows than standard Reynolds Average Navier-Stokes (RANS) models. Moreover, due to the constant increase in computational resources, this type of simulations complies more and more with industrial interests and design cycles.
In this thesis, the possibilities offered by DES to simulate unsteady crosswind aerodynamics of simple vehicle models in an industrial framework are explored. A large part of the work is devoted to the grid design, which is especially crucial for truthful results from DES. Additional concerns in simulations of unsteady crosswind aerodynamics are highlighted, especially for the resolution of the wind-gust boundary layer profiles. Finally, the transient behaviour of the aerodynamic loads and the flow structures are analyzed for several types of vehicles. The results simulated with DES are promising and the overall agreement with the experimental data available is good, which illustrates a certain reliability in the simulations. In addition, the simulations show that the force coefficients exhibit highly transient behaviour under gusty conditions.
ECO2 Crosswind Stability and Unsteady Aerodynamics for Ground Vehicles
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Alekseeva, Natalia Mihajlovna, and Natalia Alekseeva. "Developing an autosteering of road motor vehicles in slippery road conditions." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13155942/?lang=0, 2020. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13155942/?lang=0.
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In the nearest future, the human driver is viewed as a reliable backup even for the fully automated road motor vehicles (cars). Indeed, the driver is assumed to swiftly take the control of the car in cases of suddenly occurring (i) challenging environmental conditions, (ii) complex unforeseen driving situations, or (iii) degradation of performance of the car. However, due to the cognitive overload in such a sudden, stressful takeover of the control, the driver would often experience the startle effect, which usually results in an unconscious, instinctive, yet incorrect response. An extreme case of startle is freezing, in which the driver might be incapable to respond to the sudden takeover of control at all. The possible approaches to alleviate the startle during the takeover of control (i.e., the automation startle) include an offset- (i.e., either early- or delayed-), gradual yielding the controls to the driver. In the cases considered above, however, these approaches are hardly applicable because of (i) the presumed unpredictability of the events that result in the need of takeover of control, and (ii) the severe time constraints of the latter. Conversely, the objective of our research is to propose an approach of minimizing the need of yielding the control to the driver in challenging environmental conditions by guaranteeing an adequate automated control in these conditions. Focusing on slippery roads as an instance of challenging conditions, and steering control as an instance of control, we aim at developing such an automated steering that controls the car adequately in various road surfaces featuring low friction coefficients without the need of driver’s intervention.In order to develop such an automated steering we employed an in-house evolutionary computation framework – XML-based genetic programming (XGP) – which offers a flexible, portable, and human readable representation of the evolved optimal steering functions. The trial runs of the evolved steering functions were performed in the Open Source Racing Car Simulator (TORCS), which features a realistic, yet computationally efficient simulation of the car and its environment. The obtained experimental results indicate that due to the challenging dynamics of the unstable car on slippery roads, neither the canonical (tuned) servo-control (as a variant of PD) nor the (tuned) PID-controller could control the car adequately on slippery roads. On the other hand, the controller, featuring a relaxed, arbitrary structure evolved by XGP outperforms both the servo- and PID controllers in that it results in a minimal deviation of the car from its intended trajectory in rainy, snowy, and icy road conditions. Moreover, the evolved steering that employs anticipated perceptions is even superior as it could anticipate the imminent understeering of the car at the entry of the turns and consequently – to compensate for such an understeering by proactively turning the steering wheels in advance – well before entering the turn. The obtained results suggest a human competitiveness of the evolved automated steering as it outperforms the commonly used alternative steering controllers proposed by human experts. The research could be viewed as a step towards the evolutionary development of automated steering of cars in challenging environmental conditions.博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University
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Banks, Karen S. "Together on the road /." Full text available online, 2009. http://www.lib.rowan.edu/find/theses.
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Arikan, Kutluk Bilge. "Identification Of Handling Models For Road Vehicles." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609440/index.pdf.
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This thesis reports the identification of linear and nonlinear handling models for road vehicles starting from structural identifiability analysis, continuing with the experiments to acquire data on a vehicle equipped with a sensor set and data acquisition system and ending with the estimation of parameters using the collected data. The 2 degrees of
freedom (dof) linear model structure originates from the well known linear bicycle model that is frequently used in handling analysis of road vehicles. Physical parameters of the bicycle model structure are selected as the unknown parameter set that is to be identified. Global identifiability of the model structure is analysed, in detail, and concluded according to various available sensor sets. Physical parameters of the bicycle model structure are estimated using prediction error estimation method. Genetic algorithms are used in the optimization phase of the identification algorithm to overcome the difficulty in the selection of initial values for parameter estimates. Validation analysis of the identified model is also presented. Identified model is shown to track the system response successfully. Following the linear model identification, identification of 3 dof nonlinear models are studied. Local identifiability analysis is done and optimal input is designed using the same procedure for linear model structure identification. Practical identifiability analysis is performed using Fisher Information Matrix. Physical parameters are estimated using the data from simulated experiments. High accuracy estimates are obtained. Methodology for nonlinear handling model identification is presented.
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Lundahl, Kristoffer. "Models and Critical Maneuvers for Road Vehicles." Doctoral thesis, Linköpings universitet, Fordonssystem, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-127798.
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As manufacturers are pushing their research and development toward more simulation based and computer aided methods, vehicle dynamics modeling and simulation become more important than ever. The challenge lies in how to utilize the new technology to its fullest, delivering the best possible performance given certain objectives and current restrictions. Here, optimization methods in different forms can be a tremendous asset. However, the solution to an optimization problem will always rely on the problem formulation, where model validity plays a crucial role. The main emphasis in this thesis lies within methodology and analysis of optimal control oriented topics for safety-critical road-vehicle maneuvers. A crucial element here is the vehicle models. This is investigated as a first study, evaluating the degree to which different model configurations can represent the lateral vehicle dynamics in critical maneuvers, where it is shown that even the low-complexity models describe the most essential vehicle characteristics surprisingly well. How to formulate the optimization problems and utilize optimal control tools is not obvious. Therefore, a methodology for road-vehicle maneuvering in safety-critical driving scenarios is presented, and used in evaluation studies of various vehicle model configurations and different road-surface conditions. It was found that the overall dynamics is described similarly for both the high- and low-complexity models, as well as for various road-surface conditions. If more information about the surroundings is available, the best control actions might differ from the ones in traditional safety systems. This is also studied, where the fundamental control strategies of classic electronic stability control is compared to the optimal strategy in a safety-critical scenario. It is concluded that the optimal braking strategy not only differs from the traditional strategies, but actually counteracts the fundamental intentions from which the traditional systems are based on. In contrast to passenger cars, heavy trucks experience other characteristics due to the different geometric proportions. Rollover is one example, which has to be considered in critical maneuvering. Model configurations predicting this phenomenon are investigated using optimal control methods. The results show that the simple first go-to models have to be constrained very conservatively to prevent rollover in more rapid maneuvers. In vehicle systems designed for path following, which has become a trending topic with the expanding area of automated driving, the requirements on vehicle modeling can be very high. These requirements ultimately depend on several various properties, where the path restrictions and path characteristics are very influential factors. The interplay between these path properties and the required model characteristics is here investigated. In situations where a smooth path is obtained, low-complexity models can suffice if path deviation tolerances are set accordingly. In more rapid and tricky maneuvers, however, vehicle properties such as yaw inertia are found to be important. Several of the included studies indicate that vehicle models of lower complexity can describe the overall dynamics sufficiently in critical driving scenarios, which is a valuable observation for future development.
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Tuplin, Simon. "Adaptive electronic throttle control of road vehicles." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/34641.
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Previous work at Loughborough University has clearly demonstrated the gains that can be made in overall performance feel through the manipulation of the engine demand map. In particular the studies have shown the importance of the throttle progression, and the relationship between throttle pedal progression and wide-open throttle performance. These studies concluded with a clear set of design guidelines for the initial set up of a vehicle to achieve optimal performance feel for a population of drivers. These studies also highlighted the wide variation in response from different subjects indicating that further gains in satisfaction could be achieved if the demand map were optimised for each driver. Failing to provide optimum performance feel for the driver can result in reduced satisfaction, in turn making vehicles less saleable and more difficult to drive through the increased concentration needed to drive the vehicle. This thesis attempts to solve the problem of demographic and driver preference variation, by developing an electronic throttle system that adapts to driver preference.
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Esterhuyse, JC. "Aerodynamic drag of a two-dimensional external compression inlet at supersonic speed." Thesis, Cape Technikon, 1997. http://hdl.handle.net/20.500.11838/1297.
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Thesis (DTech (Mechanical engineering))--Cape Technikon, 1997This study forms the basis from which the aerodynamic drag of a practical supersonic inlet can be predicted. In air-breathing propulsion systems, as used in high performance flight vehicles, the fuel is carried onboard and the oxygen required for combustion is ingested from the ambient atmosphere. The main function of the inlet is to compress the air from supersonic to subsonic conditions with as little flow distortion as possible. When the velocity of the vehicle approaches or exceeds sonic velocity (M = 1,0) a number of considerations apply to the induction system. The reason for this is that the velocity of the ingested air has to be reduced to appreciably less than sonic velocity, typically to M = 0,3. Failure to do so will cause the propulsion system to be inoperative and cause damage. In the process of compressing the air from supersonic to subsonic conditions a drag penalty is paid. The drag characteristics are a function of the external geometry and internal flow control system of the inlet. The problem which was investigated dealt with drag of a specific type of inlet, namely a two-dimensional external compression inlet. This study is directed at formulating definitive relationships which can be used to design functional inlet systems. To this effect the project was carried out over three phases, a theoretical investigation where a fluid-flow analysis was done of the factors influencing drag. The second phase covered a comprehensive experimental study where intensive wind-tunnel tests were conducted for flight Mach numbers of M = 1,8; M = 2,0; M = 2,2; M = 2,3 and M = 2,4. During the third phase a comparison, between the theoretical values and experimental data was done, for validating the predicted aerodynamic drag figures. The following findings are worth recording: • the increase in total drag below the full flow conditions is more severe than predicted due to the contribution of spillage drag; • the range for subcritical mode of operation is smaller than expected due to boundary layer effects. The study has shown that reasonably good correlation could be achieved between the theoretical analysis and empirical test at low subcritical modes of operation. This suggests that the study has achieved its primary objective.
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Kim, Yusik. "Wind turbine aerodynamics in freestream turbulence." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/360372/.
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Topics in wind turbine aerodynamics are reviewed. These include the effect of freestrearn turbulence all the flows over wind turbine blades; dynamic stall phenomenon; and rotational augmentation. The advantages of numerical studies on these topics are highlighted and large-eddy simulation (LES) is selected to overcome the defects for other numerical approaches, e.g. Reynolds Average Navier-Stokes (RANS) , all such applications
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Docton, Mark K. R. "The simulation of transient cross winds on passenger vehicles." Thesis, Durham University, 1996. http://etheses.dur.ac.uk/1580/.
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Singh, Yuvraj. "Regression Models to Predict Coastdown Road Load for Various Vehicle Types." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595265184541326.
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Coppin, Joe. "Aerodynamics, stability and shape optimisation of unmanned combat air vehicles." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/6987/.
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Unmanned Combat Air Vehicles have been proposed for future military roles. The shape of these vehicles is driven by stealth requirements and is often aerodynamically compromised. This results in designs which struggle to meet their take-off lift requirements without experiencing flow separations and unacceptable instabilities in the pitch or yaw axis. This work aims to better understand the aerodynamics of these vehicles as well as develop methods to generate improved designs. An in depth RANS analysis has been completed for the Boeing 1303 UCAV concept with validation from QinetiQ 5m and ARA transonic wind tunnels. Two flow solvers and various turbulence models have been used. Longitudinal and directional stability have been investigated, looking at total and spanwise forces, pressure distributions and flow visualisation. The effects of modelling assumptions has also been studied. This has helped to better understand the underlying flowfield and has given some indication as to how the design may be improved. A novel design methodology has been developed and applied to the 1303 UCAV aiming to minimise drag at cruise while ensuring the leading edge flow remains attached at take-off. This is based on an a sequential quadratic programming (SQP) optimiser where objective function (CD) is calculated with an in house solver MERLIN and the gradients are calculated in an efficient manner using a discrete adjoint solver adjoint-MERLIN. High lift constraints were applied based on Lan's Quasi-Vortex-Lattice Method with an experimentally derived limit on attainable leading edge thrust. The geometry was parametrised with Bézier-Bernstein polynomials combined with the Class Shape Transformation method for improved geometrical control near the leading edge. Various designs were produced giving some indication of the trade-off between cruise and high lift performance as well as limitations to the method. The method has proved to be good for generating balanced designs however higher lift designs suffer from lower surface separation at cruise.
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Silin, Dmytro. "AERODYNAMICS AND FLIGHT PERFORMANCE OF FLAPPING WING MICRO AIR VEHICLES." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194755.
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Research efforts in this dissertation address aerodynamics and flight performance of flapping wing aircraft (ornithopters). Flapping wing aerodynamics was studied for various wing sizes, flapping frequencies, airspeeds, and angles of attack. Tested wings possessed both camber and dihedral. Experimental results were analyzed in the framework of momentum theory. Aerodynamic coefficients and Reynolds number are defined using a reference velocity as a vector sum of a freestream velocity and a stroke-averaged wingtip velocity. No abrupt stall was observed in flapping wings for the angle of attack up to vertical. If was found that in the presence of a freestream lift of a flapping wing in vertical position is higher than the propulsive thrust. Camber and dihedral increased both lift and thrust. Lift-curve slope, and maximum lift coefficient increased with Reynolds number. Performance model of an ornithopter was developed. Parametric studies of steady level flight of ornithopters with, and without a tail were performed. A model was proposed to account for wing-sizing effects during hover. Three micro ornithopter designs were presented. Ornithopter flight testing and data-logging was performed using a telemetry acquisition system, as well as motion capture technology. The ability of ornithopter for a sustained flight and a presence of passive aerodynamic stability were shown. Flight data were compared with performance simulations. Close agreement in terms of airspeed and flapping frequency was observed.
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Whitehead, James Anthony. "Aerodynamics and propulsion of synthetic jet based micro air vehicles." Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409883.
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Uys, Barend Petrus. "Omrol van veldvoertuie." Pretoria : [s.n.], 2007. http://upetd.up.ac.za/thesis/available/etd-06032008-113745/.
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Wells, Andrew K. "Slat aerodynamics and aeroacoustics with flow control." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/49932/.
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This study primarily investigated the flow and aeroacoustics associated with the slat of a three-element aerofoil in approach conditions. The study assessed importance of several factors and examined their aerodynamic impacts. The factors investigated were aerofoil incidence, slat angle, slat cusp geometry, fixing transition and blowing in the slat cove. A combination of experimental and computational techniques investigated the factors selected. The experimental work employed PIV, pressure tap, a force balance, flush mounted microphones and an acoustic array. The computational work used DES along with the FW-H acoustic analogy to obtain the far-field directivity. Tonal features occurred at high incidence and originated at the slat trailing edge, due to the blunt trailing edge and gap, and at the reattachment point. Fixing transition removes the tone at the reattachment point and reduces the slat gap tone at the trailing edge but does not remove the tone generated by the blunt trailing edge. All of the tones found, only occurred at certain slat and wing settings. Broadband sound was present in all conditions but had a strong dependence on the incidence of the wing. The sound was loudest with the wing at = 5o with a reduction as the wing incidence was increased. The broadband sound also reduced as the slat angel decreased from S = 23o. The shear incidence angle was a good indicator of the impact of these two factors on the sound generated. Extending the slat cusp reduced the broadband sound at low aerofoil incidence. However, for 10o the extension led to increased broadband sound. Neither blowing nor fixing transition had a significant impact on the broadband sound generated by the slat system. The aerodynamic loads generated by the wing were mainly dependent on the aerofoil incidence. However, other factors did influence the forces generated. Reducing the slat angle increased the lift generated by the wing especially at low aerofoil incidence but the lift to drag ratio was unaltered. At high aerofoil incidence, extending the slat cusp reduced the lift generated. Blowing and fixing transition did not significantly alter the forces generated by the wing.
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Angland, David. "Aerodynamics and aeroacoustics of flap side-edges." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/66077/.
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An experimental and computational investigation was carried out to determine the aerodynamics and aeroacoustics of a flap side-edge. A porous side-edge treatment was applied to the flap side-edge in an attempt to reduce airframe noise. Measurements taken as part of the experimental study were forces, on-surface pressures, particle image velocimetry, hotwire anemometry and on-surface microphones. Oil flow was performed to visualise the on-surface flow. A detached eddy simulation was performed on a geometry that consisted of a main element and a half span flap to understand the flowfield. From the experimental and computational investigation four sources of vorticity in the flowfield were identified, i.e. the main element cove, the main element trailing-edge, separation on the flap suction surface, and the flap side-edge vortical system. These sources of vorticity interacted to produce a significantly unsteady flowfield above the solid flap surface. Three potential acoustic sources on the flap were identified. The first two sources were the turbulent shear layers that rolled up to form the flap side-edge vortex, reattaching firstly on the side-edge and secondly on the suction surface of the flap. A mid-frequency broadband hump was measured by an on-surface microphone at the point of reattachment of the turbulent shear layer on the flap side-edge. The third source was a low frequency instability in the off-surface vortex due to non-linear vortical interactions upstream of the flap. This instability was measured by a hotwire in the downstream vortex and by an on-surface microphone in the main element flap cove. The application of a porous flap side-edge had two favourable effects. Firstly, it reduced the magnitude of vorticity in the turbulent shear layer and the vortex. This reduced the magnitude of the hydrodynamic instabilities induced by the flap side-edge vortex. Secondly, it displaced the vortex further away from the flap surface due to the finite mass flux allowed through the porous material. This reduced the magnitude of the disturbances that interacted with the solid flap surface by moving them further away. The effect of applying a porous flap side-edge was most noticeable in reducing the mid frequency broadband hump in the on-surface microphone measurements.
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Simpson, Andrew G. "Parametric modelling of energy consumption in road vehicles /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe.pdf.
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Sahlholm, Per. "Distributed Road Grade Estimation for Heavy Duty Vehicles." Doctoral thesis, KTH, Reglerteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32054.
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An increasing need for goods and passenger transportation drives continued worldwide growth in traffic. As traffic increases environmental concerns, traffic safety, and cost efficiency become ever more important. Advancements in microelectronics open the possibility to address these issues through new advanced driver assistance systems. Applications such as predictive cruise control, automated gearbox control, predictive front lighting control, and hybrid vehicle state-of-charge control decrease the energy consumption of vehicles and increase the safety. These control systems can benefit significantly from preview road grade information. This information is currently obtained using specialized survey vehicles, and is not widely available. This thesis proposes new methods to obtain road grade information using on-board sensors. The task of creating road grade maps is addressed by the proposal of a framework where vehicles using a road network collect the necessary data for estimating the road grade. The estimation can then be carried out locally in the vehicle, or in the presence of a communication link to the infrastructure, centrally. In either case the accuracy of the map increases over time, and costly road surveys can be avoided. This thesis presents a new distributed method for creating accurate road grade maps for vehicle control applications. Standard heavy duty vehicles in normal operation are used to collect measurements. Estimates from multiple passes along a road segment are merged to form a road grade map, which improves each time a vehicle retraces a route. The design and implementation of the road grade estimator are described, and the performance is experimentally evaluated using real vehicles. Three different grade estimation methods, based on different assumption on the road grade signal, are proposed and compared. They all use data from sensors that are standard equipment in heavy duty vehicles. Measurements of the vehicle speed and the engine torque are combined with observations of the road altitude from a GPS receiver, using vehicle and road models. The operation of the estimators is adjusted during gearshifts, braking, and poor satellite coverage, to account for variations in sensor and model reliability. The estimated error covariances of the road grade estimates are used together with their absolute positions to update a stored road grade map. Highway driving trials show that the proposed estimators produce accurate road grade data. The estimation performance improves as the number of road segment traces increases. A vehicle equipped with the proposed system will rapidly develop a road grade map for its area of operation. Simulations show that collaborative generation of the third dimension for a pre-existing large area two-dimensional map is feasible. The experimental results indicate that road grade estimates from the proposed methods are accurate enough to be used in predictive vehicle control systems to enhance safety, efficiency, and driver comfort in heavy duty vehicles. The grade estimators may also be used for on-line validation of road grade information from other sources. This is important in on-board applications, since the envisioned control applications can degrade vehicle performance if inaccurate data are used.QC 20110408
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Gordon, Greg P. (. "Laser position locating system for off-road vehicles /." Connect to resource, 1987. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1200512216.
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Potter, Theodore Edmund Cooper. "Assessing the road damaging potential of heavy vehicles." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389885.
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Wang, Yifei. "Advanced road and obstacle analysis for intelligent vehicles." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556742.
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Road and obstacle analysis are two of the essential building blocks in both Driver Assistance Systems (DAS) and Autonomous Transportation Systems (ATS). Our research focus is to develop computationally efficient algorithm for accurate de- tection of the road boundaries and potential obstacles ba ed on prior knowledge of the highway and urban environments. In this thesis, a novel lane feature extrac- tion algorithm is introduced. It incorporates the global lane shape information to accurately extract feature points that overlap with the lane boundaries. It can be used a a general framework to improve or refine the feature map obtained with a diverse range of local feature extractors. At the lane tracking stage, the performance of the Gaussian Particle Filter (GPF), Gaussian Sum Particle Filter (GSPF) and Sampling Importance Resampling (SIR) particle filter are compared. The GSPF shows a preferable characteristic which is suitable for the lane track- ing application and leads to the best results. For motion-based obstacle detec- tion, we propose a computationally efficient image warping algorithm for motion compensation. This algorithm achieves higher efficiency as well as identical re- sults to perspective mapping based approaches. Furthermore, we investigated stereo vision based obstacle detection and developed a disparity calculation algo- rithm using multi-pass aggregation and local optimisation which utilises the prior knowledge of the traffic scene. This algorithm achieves comparable results to the global optimisation based algorithms with lower computational complexity. Dur- ing the obstacle detection stage, the G-Disparity image. which encloses disparity gradient information, is proposed. Using G-Disparity in conjunction with the -V-Di parity images allows more efficient obstacle extraction with performance improvement over the conventional U- V-Disparity based approaches.
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Wanner, Daniel. "Controlling over-actuated road vehicles during failure conditions." Doctoral thesis, KTH, Fordonsdynamik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-166819.
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The aim of electrification of chassis and driveline systems in road vehicles is to reduce the global emissions and their impact on the environment. The electrification of such systems in vehicles is enabling a whole new set of functionalities improving safety, handling and comfort for the user. This trend is leading to an increased number of elements in road vehicles such as additional sensors, actuators and software codes. As a result, the complexity of vehicle components and subsystems is rising and has to be handled during operation. Hence, the probability of potential faults that can lead to component or subsystem failures deteriorating the dynamic behaviour of road vehicles is becoming higher. Mechanical, electric, electronic or software faults can cause these failures independently or by mutually influencing each other, thereby leading to potentially critical traffic situations or even accidents. There is a need to analyse faults regarding their influence on the dynamic behaviour of road vehicles and to investigate their effect on the driver-vehicle interaction and to find new control strategies for fault handling. A structured method for the classification of faults regarding their influence on the longitudinal, lateral and yaw motion of a road vehicle is proposed. To evaluate this method, a broad failure mode and effect analysis was performed to identify and model relevant faults that have an effect on the vehicle dynamic behaviour. This fault classification method identifies the level of controllability, i.e. how easy or difficult it is for the driver and the vehicle control system to correct the disturbance on the vehicle behaviour caused by the fault. Fault-tolerant control strategies are suggested which can handle faults with a critical controllability level in order to maintain the directional stability of the vehicle. Based on the principle of control allocation, three fault-tolerant control strategies are proposed and have been evaluated in an electric vehicle with typical faults. It is shown that the control allocation strategies give a less critical trajectory deviation compared to an uncontrolled vehicle and a regular electronic stability control algorithm. An experimental validation confirmed the potential of this type of fault handling using one of the proposed control allocation strategies. Driver-vehicle interaction has been experimentally analysed during various failure conditions with typical faults of an electric driveline both at urban and motorway speeds. The driver reactions to the failure conditions were analysed and the extent to which the drivers could handle a fault were investigated. The drivers as such proved to be capable controllers by compensating for the occurring failures in time when they were prepared for the eventuality of a failure. Based on the experimental data, a failure-sensitive driver model has been developed and evaluated for different failure conditions. The suggested fault classification method was further verified with the conducted experimental studies. The interaction between drivers and a fault-tolerant control system with the occurrence of a fault that affects the vehicle dynamic stability was investigated further. The control allocation strategy has a positive influence on maintaining the intended path and the vehicle stability, and supports the driver by reducing the necessary corrective steering effort. This fault-tolerant control strategy has shown promising results and its potential for improving traffic safety.QC 20150520
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Williams, Ian D. "Public attitudes to air pollution from road vehicles." Thesis, Middlesex University, 1994. http://eprints.mdx.ac.uk/13441/.
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An assessment of the environmental effects of any new road scheme is currently recommended by the Department of Transport, but the existing appraisal does not include an evaluation of public nuisance from vehicle-derived air pollution. This research project has investigated the subjective nuisance effects of air pollution from road traffic on the public through the simultaneous measurement of public attitudes towards vehicle-generated nuisance and air quality in residential and commercial areas. Roadside pollutant concentrations were monitored during four London-based surveys involving the measurement of CO, NOx, gaseous hydrocarbons, SO₂, O₃, carbonyl compounds, smoke and total suspended particulates. At these roadside locations, traffic flow and classification data were collected together with local and regional meteorological data. To extend the database, air quality data was collected from five other cities within the UK. These data were obtained from the relevant local authority monitoring sites and/or DoE Enhanced Urban Network sites. Monitored air pollutant concentrations were found to be similar to those recorded previously at comparable sites. At the roadside locations, the air quality according to the DoE's public information criteria was typically 'very good' for SO₂and O₃, but sometimes 'poor' for NO₂. At the urban background locations, air quality was generally very good. Positive and significant correlations were recorded between the major vehicular primary pollutants of CO, NO and NMHC and traffic flow at all sites. NO₂/NOx ratios were lower at the commercial locations than at the residential locations, reflecting the lack of available O₃ for NO-NO₂ conversion. Roadside black smoke concentrations were much higher than those typically recorded at rooftop level in the UK, probably indicating the strong influence of diesel vehicle emissions and/or the extreme 'blackness' of diesel particles, and suggesting that the 8-Port technique may overestimate roadside black smoke concentrations. Social surveys, utilising questionnaires developed especially for this research, were performed to assess the causes, extent and magnitude of public nuisance from vehicle-derived air pollution at each of the pollutant monitoring sites. The survey data indicates the high relative importance of air pollution from road traffic when compared to other social issues, indicating that concern for the environment is now an established social issue rather than a transient preoccupation. Local environmental issues were generally of relatively low priority, although traffic-related nuisances were very important local environmental nuisances. Indoors, noise from road traffic was the most important vehicle-derived disturbance with the major concerns relating to the soiling of surfaces and the malodour of fumes. Outdoors, disturbance from smoke, fumes and odour was the most frequently complained about traffic-induced nuisance, with danger ranking equally highly. Most respondents were concerned about the effects of fumes upon their health, with adverse effects widely assumed. Significant differences in disturbance between sites in the same and different cities, between females and males and between different age groups were recorded. No significant differences in annoyance were noted between smokers/non-smokers and different socio-economic groupings. At each location, pollutant concentrations are discussed and the results of the social surveys are presented and interpreted. The relationships between nuisance and pollutant concentrations are examined graphically and a mathematical relationship between black smoke concentrations and disturbance score is produced. This relationship is not considered to be sufficiently accurate for predictive purposes and an alternative method for estimating nuisance is proposed.
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Gordon, Greg P. "Laser position locating system for off-road vehicles." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1200512216.
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Dal, Bianco Nicola. "Optimal control of road vehicles: theory and applications." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3424690.
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In this thesis Optimal Control (OC) of road vehicles is studied especially focusing on minimum lap time simulations. The theory underlying the most used optimal control solving techniques is described, including both the Pontryagin Maximum Principle and the reduction to Nonlinear Programming. Direct and indirect methods for optimal control problems are presented and compared against minimum lap time simulations (LTS).
Modelling of vehicles for OC-LTSs is studied in order to understand how different design choices can affect simulation outcomes. Novel multibody models of four wheeled vehicles - a GP2 car and a go-kart - for OC-LTSs are developed and validated thorough comparison with experimental data. Particular attention is dedicated to the simulation of tyre load dynamics, that is achieved by a proper modelling of the chassis and suspension motions and of the aerodynamic forces.
OC-LTSs are applied to electric vehicles too, specifically to optimise the design of an electric motorbike taking part at the Tourist Trophy Zero competition. A concise yet effective model is proposed in order to perform reliable simulations on a 60km long road in a reasonable amount of time. Experimental data is used to validate the model. A direct full collocation transcription method for OCPs dealing with implicit differential equations and control derivatives is presented, moreover the structure of the resulting NLP problem is accurately described. The relationship between the first order necessary conditions and the Lagrange multipliers of the NLP and OC problems are derived under the adopted discretisation scheme. The presented transcription method is implemented into a software which is currently in use at the University of Padova to solve OC-LTSs.In this thesis Optimal Control (OC) of road vehicles is studied especially focusing on minimum lap time simulations. The theory underlying the most used optimal control solving techniques is described, including both the Pontryagin Maximum Principle and the reduction to Nonlinear Programming. Direct and indirect methods for optimal control problems are presented and compared against minimum lap time simulations (LTS). Modelling of vehicles for OC-LTSs is studied in order to understand how different design choices can affect simulation outcomes. Novel multibody models of four wheeled vehicles - a GP2 car and a go-kart - for OC-LTSs are developed and validated thorough comparison with experimental data. Particular attention is dedicated to the simulation of tyre load dynamics, that is achieved by a proper modelling of the chassis and suspension motions and of the aerodynamic forces. OC-LTSs are applied to electric vehicles too, specifically to optimise the design of an electric motorbike taking part at the Tourist Trophy Zero competition. A concise yet effective model is proposed in order to perform reliable simulations on a 60km long road in a reasonable amount of time. Experimental data is used to validate the model. A direct full collocation transcription method for OCPs dealing with implicit differential equations and control derivatives is presented, moreover the structure of the resulting NLP problem is accurately described. The relationship between the first order necessary conditions and the Lagrange multipliers of the NLP and OC problems are derived under the adopted discretisation scheme. The presented transcription method is implemented into a software which is currently in use at the University of Padova to solve OC-LTSs.
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Castillo-Rivera, Salvador. "Advanced modelling of helicopter nonlinear dynamics and aerodynamics." Thesis, City University London, 2014. http://openaccess.city.ac.uk/13169/.
Full textAbstract:
The work presented here provides a comprehensive dynamic and aerodynamic helicopter model. The possible applications of this work are wide including, control systems applications, reference and trajectory tracking methods implementation amongst others. The model configuration corresponds to a Sikorsky helicopter; a main rotor in perpendicular combination with a tail rotor. Also, a particular model of unmanned aerial vehicle has been modelled as part of collaboration with the La Laguna University (Spain). The modelling tool is VehicleSim, a program that builds rigid body systems, solves the nonlinear equations of motion and generates the time histories of the corresponding state variables of the vehicle under study. VehicleSim is able to provide the linearised equations of motion in a Matlab file and the symbolic state-space model. This is useful when control systems are to be designed. The main rotor model accounts for flap, lag and feather motions for each blade as well as for their nonlinear dynamic coupling. The tail rotor is modelled including the flap-feather coupling via delta three angle. The main and tail rotors' angular velocities are implemented by PID controllers. Main rotor linear and nonlinear equations are derived and validated by comparison with the theory. Main rotor flap and lag degrees of freedom are validated using frequency domain approaches in the absence of external forces. Also, fuselage-main rotor interaction is studied and validated by using modal analysis and root locus methodology. Vibrations originated at the main rotor are simulated and their effects on the fuselage are examined by a Short Time Fourier transformation. The aerodynamic model uses blade element theory on the main-tail rotors. Hover, climb, descent and forward flight conditions are simulated and they allow the helicopter to follow certain trajectories. Finally, the ensuing vibrations when an external perturbation is applied to the main rotor are investigated.