Moustafa El-Gindy

Rollover dynamics of road vehicles: literature survey

This paper presents a review of literature pertaining to vehicular rollover. It is by no means a complete review of all rollover literature available, but covers many of the most frequently cited papers and those that the author believes make a substantial contribution to the field of vehicle dynamics and rollover in particular. This review is limited to papers covering rollover of road vehicles, such as passenger cars, utility vehicles and heavy commercial trucks - both articulated and non-articulated, i.e. the review excludes papers regarding off-road vehicles. In addition, this review focuses mainly on cases of manoeuvre induced rollover such as rollover in cornering, lane-change manoeuvres, etc., though rollover by tripping is discussed to a certain degree. It begins with a general introduction to the rollover phenomenon that may be applied to both articulated and non-articulated vehicles. Non-articulated vehicles are then examined in more detail and a review of some research into stability metrics and the prediction of rollover for these vehicles is presented. Likewise, the stability metrics and prediction of rollover for articulated heavy trucks carrying rigid and liquid cargo is reviewed along with work into active suspensions, braking control and rollover warning devices.

Examination of different control strategies of heavy-vehicle performance

Heavy vehicles play an economically important role in the transportation process, and their numbers have been increasing for several decades. The active safety of the highway system is an important consideration in the design of a heavy vehicle combination. In this paper, the handling characteristics of a 5-axle tractor-semitrailer is examined and used to test for the desired features of the vehicles handling and stability. Using these results the optimal control criterion is derived for the vehicle. Four different control strategies are examined by using the Linear Quadratic Regulator (LQR) approach. These are, active steering of the rear wheels of the tractor; active steering of the wheels of the trailer; active torque control in the fifth-wheel joint; and active yaw torque acting on the tractor. These controllers are designed and examined using a simplified linear vehicle model. In addition to discussing the above-mentioned approaches, this paper discusses a method of modifying the slip angles at the tractors rear (driven) axles, however the yaw torque at the tractor cg also can be controlled using what is called unilateral braking. As well, the replacement of the active torque control at the fifth wheel joint, by a control strategy based on the usage of controllable dampers at the fifth-wheel joint, will also be examined. In this case, a nonlinear mathematical model of the vehicle is used and a modified control strategy called the RLQR/H∞ approach is used to ensure the vehicles performance in the presence of parametric uncertainties. The examination of these control strategies is conducted by using a sophisticated non-linear vehicle model, and the influence of these control strategies on the vehicles directional and roll stability during severe path-follow lane-change manoeuvre is discussed.

Technical Report: Literature Survey on Driving Simulator Validation Studies

The use of real-time driving simulators for research and training of vehicle operators has increased significantly in recent years. There is a wide range of complexity among simulators currently being used around the world. An important issue to consider when implementing any simulator is validity. This paper presents different interpretations of validity in the context of simulators and vehicle simulation models found in the literature. Examples of different approaches to validating simulators and vehicle simulation models from studies found in the literature are presented.

Heavy vehicle ride comfort: literature survey

The issue of ride comfort for vehicle operations has generated considerable interest recently especially in heavy vehicle systems since long distance drivers are more likely to experience high levels of vibration. This paper introduces the general concept of vibration-related health problems, discusses ride comfort assessment criteria and methods, then focuses on the methodology of using computer simulation to analyse ride comfort. The computer-based ride comfort model can be divided into three sub models: vehicle model, driver/seat model, and road profile input model. Time domain and frequency domain analysis is addressed for seven vehicle models, and detailed modelling techniques are introduced. Five driver/seat models are reviewed to examine the transmissibility and impedance of vibration data from the cab floor through the seat to the body of the operator; these characteristics are routinely neglected in vehicle simulation due to their complexity and uncertainty. Road profile data can be field-measured data as well as the data generated based on the power spectral density method. While the former gives the more accurate result, the latter will allow more flexibility to apply various road conditions to the simulation program.

Sliding mode control for rollover prevention of heavy vehicles based on lateral acceleration

Accidents involving heavy trucks and tractor semi-trailers have contributed significantly to the number of injuries and fatalities on North American highways over the past few decades. This paper investigates two rollover prevention strategies for a truck/semitrailer based on a sliding mode controller. A control strategy based on limiting the lateral acceleration of the center of gravity of the trailer has been examined to prevent rollover of a 75,000 lb 5-axle tractor/semitrailer by applying differential braking. Two different steering inputs, ramp and sinusoidal, were investigated. It was determined that the torque generated by the differential braking could be effective in preventing rollover.

LITERATURE SURVEY OF TRANSIENT DYNAMIC RESPONSE TYRE MODELS

This paper presents a literature review of simulation models that focus on transient dynamic tyre response. Such response largely arises from road roughness, tyre/wheel assembly nonuniformities, and different contact interfaces, and it is directly related to vehicle handling, control, and ride comfort. Generally speaking, three primary approaches have been used to model this kind of response: lumped parameter models, semi-analytical approaches, and full finite element method (FEM) analysis. These three approaches represent three different areas, viewpoints and major interests separately. Advantages, disadvantages, and motivations for use of these different models are discussed. As computational speeds increase at a rapid pace, FEM models continue to gain recognition and prominence as a major analytical tool for tyre design and development in tyre dynamics studies. This survey pays special attention to FEM tyre dynamics models and to studies that relate tyre parameters such as stiffness and damping to tyre design and performance.

FEA Rotating Tire Modeling for Transient Response Simulations

A full nonlinear finite element P185/70R14 passenger car radial-ply tire model was developed and run on a 1.7-meter-diameter spinning test drum. The virtual tire/drum/cleat finite element model was constructed and tested using the nonlinear finite element analysis software, PAM-SHOCK. The tire model was constructed in extreme detail with three-dimensional solid, layered membrane, and beam finite elements, incorporating over 18,000 nodes and 24 different types of materials. In addition to the tire model itself, the rim was also included and rotated with the tire, with proper mass and rotational inertial effects. The FFT algorithm was applied to examine the transient response information in the frequency domain. The result showed that this P185/70R14 tire has clear peaks of 84 and 45 Hz transmissibility in the vertical and longitudinal directions. Also the paper presents the prediction of tire standing waves phenomenon, and computer animations of the standing waves phenomenon were carried out for the first time. The effects of different tire inflation pressures and tire axle loadings were investigated with respect to their influences on the formation of standing waves. The parameters adopted in this FEA tire model were validated against experimental work and showed excellent agreement.Copyright

Development of Rumble Strip Configurations That Are More Bicycle Friendly

This research was initiated to develop new rumble strip configurations for the Pennsylvania Department of Transportation that would alert inattentive or drowsy motorists and could be safely and comfortably traversed by bicyclists. Three primary steps were involved in the development of the new configurations. First, simulation was used to evaluate different configurations for their potential to be bicycle friendly. Second, several configurations that had the greatest potential to be bicycle friendly were installed and field experiments were conducted to further evaluate their effectiveness. Finally, the field data were analyzed and the configurations that were installed were ranked based on their ability to provide a comfortable and controllable ride for bicyclists and to alert inattentive or drowsy motorists. On the basis of results of bicycle and motor vehicle tests, two new rumble strip configurations were recommended for implementation along nonfreeway facilities. One configuration was recommended for use along nonfreeway facilities with higher operating speeds, and a second was recommended for nonfreeway facilities with lower operating speeds.

Hybrid electric vehicles technology and simulation: Literature review

To meet increasing fuel economy and emissions legislation, the automotive industry will need to undergo drastic changes in vehicle and engine designs. Unlike conventional vehicles on the road today, hybrid electric vehicles (HEV) are designed with a smaller engine and an on-board energy storage system. The smaller engine allows the vehicle to achieve better fuel economy and fewer emissions. The efficiency benefits of diesel engines over gasoline engines make the diesel engine a strong contender for further improving fuel economy. The integration of diesel-engine technology into a hybrid electric vehicle configuration is one of the most promising ways to comply with fuel-economy and emissions legislation. There are many hybrid electric vehicle and diesel engine simulation software packages available for predicting emissions and fuel economy as well as studying the overall performance. Using simulation software, it is possible to quickly and easily optimise the engine and vehicle prior to investing time and money into testing components and building prototypes. The ability to integrate an advanced engine simulation software output and an HEV simulation for the prediction of engine alterations on overall vehicle performance is a critical tool for the success of meeting vehicle emissions and fuel economy goals. The following literature review combines current information on the HEV technology, engine technology, HEV simulation software, and engine simulation software available today.

Soil Modeling Using FEA and SPH Techniques for a Tire-Soil Interaction

In recent years, the advancement of computerized modeling has allowed for the creation of extensive pneumatic tire models. These models have been used to determine many tire properties and tire-road interaction parameters which are either prohibitively expensive or unavailable with physical models. More recently, computerized modeling has been used to explore tire-soil interactions. The new parameters created by these interactions were defined for these models, but accurate soil constitutive equations were lacking. With the previous models, the soil was simulated using Finite Element Analysis (FEA). However, the meshless modeling method of Smooth Particle Hydrodynamics (SPH) may be a viable approach to more accurately simulating large soil deformations and complex tire-soil interactions. With both the FEA and SPH soils modeled as elastic-plastic solids, simplified soil tests are conducted. First, pressure-sinkage tests are used to explore the differences in the two soil-modeling methods. From these tests, it is found that the FEA model supports a surface pressure via the tensile forces created by the stretching of the surface elements. Conversely, for the SPH model, the surface pressure is supported via the compressive forces created by the compacting of particles. Next, shear-displacement tests are conducted with the SPH soil (as this test cannot easily be performed with an FEA soil model). These shear tests show that the SPH soil behaves more like clay in initial shearing and more like sand by exhibiting increased shearing due to vertical loading. While both the pressure-sinkage and shear-displacement tests still show that a larger particle density is unnecessary for SPH soil modeling, the shear-displacement tests indicate that an elastic-plastic material model may not be the best choice.Copyright