The research project 'Controllability of Road Vehicles at the Limits of Tyre Adhesion' (CROVLA) was established to investigate how tyre and chassis properties contribute to the handling characteristics and stability of vehicles operating at or near to the limit condition. The project involved the Department of Transport, SP Tyres UK Limited, Jaguar Cars and Cranfield University. An extensive proving ground test program of typical limit handling tests provided characteristic driver input and vehicle response data for a variety of vehicle configurations. The test data analysis was based on the concept of correlation. Cross- correlation coefficients and average response time delays were obtained for various pairs of quantities, namely steering angle and torque for the input and yaw rate and lateral acceleration for the response. The predictability of the vehicle response was evaluated by the rate by which the correlation coefficients change with severity. Analogous to the proving ground work, vehicle dynamics simulations were carried out. Two programs were employed to study the steady state performance and the transient limit handling behaviour. The 'Steady State Cornering Model' was used to confirm some basic suspension design rules established for optimising the lateral adhesion of a suspension design. The importance of controlling camber and vehicle jacking by an appropriate suspension design was identified. A detailed vehicle model was built-up using the simulation code AUTOSIM. After validating the model against proving ground data, some parametric studies were conducted to quantify the effects of suspension and tyre properties on the transient limit response behaviour. Proving ground and simulation results suggest that response time lags and cross- correlation coefficients in combination with other handling parameters can be used as objective quality measures. The results quantified to what extent tyre and chassis modifications change the limit handling behaviour.

High speed cornering of an off-road vehicle poses considerable challenges to the development of an autonomous vehicle due to the non-linear dynamics of the tyre road interface as well as those of the vehicle as a whole during high lateral accelerations. Most driver models are developed for low speed applications using linear control methods under the assumption of linear vehicle dy- namics. The dynamics of a vehicle however become highly non-linear as the lateral acceleration increases, thus rendering these linear models unusable during high speed manoeuvres. In this study, two robust driver models for use in an autonomous vehicle capable of path following at both low and high speeds are presented. Both models make use of the relationship between the yaw acceleration and steering rate to control the yaw angle of the vehicle. The first driver model is derived from the simulation of a full non-linear vehicle model in ADAMS. The Magic Tyre Formula is used to model the relationship between the vehicle's yaw acceleration and steer rate as a function of vehicle speed. The second driver model is a mathematical model which incorporates a form of sliding control. The model includes the lateral tyre dynamics as modelled by the Pacejka '89 tyre model. Both driver models are coupled with a gain scheduling proportional derivative controller to reduce the cross-track error. The two driver models were implemented on a Land Rover Defender and experimentally validated by performing a double lane change manoeuvre at speeds up to 80km/h. The vehicle remained stable even though the lateral accelerations experienced were 80% of the vehicle limits. The result is a robust controller capable of path following at various speeds and at high lateral accelerations. Copyright / Dissertation (MEng)--University of Pretoria, 2011. / Mechanical and Aeronautical Engineering / Unrestricted

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Thesis (M.A.)--Ohio University, November, 2008. / Title from PDF t.p. Includes bibliographical references.

Thesis (M.S.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 54-58).

Ever growing population and increased energy consumption across all industries has resulted in higher atmospheric concentration of the greenhouse gases (GHG) and therefore an increase in the planet's average temperature, which has led to increasingly demanding and more strict legislations on pollutant sources, and more specifically, the automotive industry. As a consequence of all this, the demand for research into alternative energy sources has greatly increased. In this study combustion characteristics, engine performance, and exhaust emission of diesel-ethanol and diesel-gasoline are investigated in an optical direct injection diesel engine. In particular, effects of different substitution ratios and diesel injection strategies are studied when the total fuel energy is kept constant. The three main substitution ratios used in this study include 45% (45% of fuel energy from port-injected ethanol/gasoline and 55% from direct injection diesel), 60%, and 75%. The engine used for this investigation is a Ricardo Hydra single cylinder optical engine running at 1200 rpm. In-cylinder pressure measurement is used for calculating all engine parameters, heat release rate, and efficiency. In addition to the thermodynamic analysis of the combustion parameters, high speed camera was used alongside with a copper vapor laser or the high speed image intensifier in the high speed video imaging for the optical analysis of the effect of the above-mentioned parameters on autoignition and combustion processes, while Horiba particulate analyser and AVL smoke meter were utilized in monitoring and recording emissions for every tested condition. Depending on the testing conditions, such as injection strategy and intake conditions, both dual-fuel operations were able to deliver high efficiency and improved emissions compared to that of a pure diesel engine operation, with the diesel-gasoline operation offering more consistency in improved thermal efficiency, and the diesel-ethanol operation delivering lower emission output. The optical analysis of the combustion represents the main difference in the flame propagation, distribution and quality for each substitute fuel and its substitution percentage, as well as the condition under examination.

In this study / reliability 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.

This thesis investigates the use of an active anti-roll bar as a means of improving the handling of an off-road vehicle. The active anti-roll bar consists of a stiff anti-roll bar and a hydraulic actuator at the one end between the anti-roll bar and the rear axle of the vehicle. The system is designed so that the anti-roll bar can be preloaded in both directions by the actuator. The displacement of the hydraulic actuator is close loop controlled to be a function of the lateral acceleration of the vehicle, which is measured by an accelerometer. For this study, full vehicle simulations were done in ADAMS/View to predict the response of the proposed solutions. A Land Rover Defender 110 was used as the test vehicle to verify the results of the simulations. Constant radius tests and the severe double-lane-change manoeuvre, which are standard handling tests, were used to determine the vehicle’s handling performance. Handling performance was quantified by measuring the body roll angle during the manoeuvre and noting the maximum roll angle. The effect of the active anti-roll bar on ride comfort was measured by driving over Belgian paving at a constant speed. The results show that the proposed system reduces the body roll angle to zero up to a lateral acceleration of 0.4 g during steady state handling and provided a 74% improvement in maximum body roll angle during a double-lane-change-manoeuvre at 70 km/h. The system has no detrimental effect on the ride comfort of the vehicle. / Dissertation (MEng)--University of Pretoria, 2008. / Mechanical and Aeronautical Engineering / unrestricted

The National Park Service (NPS) monitors off-road vehicle (ORV) use in National Seashores across the United States. The sediment disturbance that is caused by ORVs is believed to have a large impact on erosion (by wind or waves), which there by affects the morphology of the foredunes. With greater knowledge of ORV impacts, the NPS can better manage ORV use and minimize anthropogenic affects to the coastal environment. There remains considerable uncertainty about the disturbance and its larger-scale impact. This study quantifies the sediment disturbance made by tire tracks, as well as the tire track form, width, depth, and evolution with relation to the number of vehicle passes and location on the beach at Assateague Island National Seashore (ASIS), Maryland. To measure ORV impact, ground-based LiDAR was used to collect detailed profiles across a three by three meter test plot at each site. Based on the quantification of the displaced sediment and redistribution of that sediment from the tracks, a recommendation to the NPS can be made as to where along the beach traffic should be limited to, in order to minimize impact to the physical environment at ASIS. Tire tracks were found to widen after the first pass, as a result of the imperfections of driving. Compaction of the sediment in the center of the tire track accounts for only a minimal amount of the sediment lost from the tire tracks. Sediment removal accounted for greater than 75% of the sediment lost from the tire tracks at all sites. It was concluded that sediment removal is the most dominant factor in the creation and evolution of a tire track. The width, depth, and evolution of a tire track were also found to be controlled by the imperfections of driving. Despite the amount of sediment disturbance, it is found that there is no net downslope displacement of sediment. This conclusion counters previous ORV impact studies and suggests that ORVs are not directly responsible for beach erosion. It is also recommended that to minimize the impact of OVRs on the beach at ASIS, the NPS should limit driving to the backshore.

Local communities, individuals, visitors, and special interest groups are often called upon to participate in the decision making processes of the National Park Service (NPS). Cape Hatteras National Seashore (CAHA) engaged in a Negotiated Rulemaking process to create an Off Road Vehicle Management Rule. The rulemaking process involved park stakeholders working with the NPS as a Negotiated Rulemaking Advisory Committee with the goal of creating an Off Road Vehicle Management Rule for CAHA. This dissertation used Senecah's practical theory Trinity of Voice to evaluate CAHA's negotiated rulemaking process. Interviews with park staff and negotiated rulemaking participants provided information about the presence of the grammars of TOV in this decision making process. This dissertation described the affects of negotiated rulemaking on the perceptions of participants towards the park resources and management of the national seashore. The effect of the negotiated rulemaking process was an increase in the knowledge of participants about the decision making process employed by the NPS. In general, participants also developed a stronger relationship with park management. This research suggests critical dimensions for achieving widespread social legitimacy through meaningful public involvement in decision making.