This study provides a comprehensive modeling evaluation of the dynamic stability of Long Combination Vehicles (LCVs) that are commonly operated on U.S. highways, using multibody dynamic simulations in MATLAB/Simulink®. The dynamic equations for a tractor with two trailers connected by an A-frame converter dolly (A-Dolly) are developed. The dynamic model is used for running MATLAB® simulations, with parameters that are obtained through measurements or obtained from other sources. The simulation results are verified using track test data to establish a baseline model. The baseline model is used for parametric studies to evaluate the effect of trailer cargo weight, center of gravity (CG) longitudinal location, and trailer wheelbase. The dynamic model is further used to analyze both single-trailer and double-trailer trucks through nondimensionalization. The nondimensionalization method has the added advantage of enabling studies that can more broadly apply to various truck configurations. The simulation results indicate that increasing the trailer wheelbase reduces rearward amplification due to the damping effect of the longer wheelbase. A larger momentum ratio due to increased trailer gross weight increases rearward amplification. The detailed models of pneumatic disc and drum brakes in LCVs, including the airflow delay and thermal characteristics, are also developed and are coupled with the articulated vehicle dynamic models. The disc and drum brake braking performance are evaluated and compared in straight-line braking and combined steering and braking at a 150-ft J-turn maneuver. In straight-line braking, the simulation results indicate that disc brakes provide significantly shorter braking distance than drum brakes at highway speeds on a dry road, mainly due to their larger braking torque. On a slippery road surface, however, the greater braking torque causes more frequent wheel lockup and ABS activation at higher speeds, and disc brakes do not provide a substantially shorter braking distance than drum brakes. The simulations also point out that the disc brakes' cooling capacity is higher than the drum brake, with the cooling efficiency heavily dependent on the airflow speed. At higher driving speeds, the airflow accelerates to a turbulent flow and increases the convection efficiency. For braking in-turn maneuvers, at higher entering speeds, disc brakes decelerate the vehicle slightly sooner and then scrub speed faster, resulting in better roll stability when compared with drum brakes. / Doctor of Philosophy / Long combination vehicles (LCVs) are the combination of a tractor and two or more trailers and have been widely used on U.S. highways for cargo transport. Although LCVs have a larger cargo volume and provide more modularity in transporting goods, at higher speeds, they can be more prone to rollovers and require longer stopping distances and space to maneuver from one lane of travel to another. This study investigates the dynamic stability of an LCV, A-double trailer that includes a tractor, two trailers, and a dolly through modeling and simulation. The dynamic equations of each vehicle unit are derived based on Newtonian Mechanics (i.e., F = ma). The dynamic models are tuned to match the track testing results for similar vehicles, performed by the Center for Vehicle Systems and Safety (CVeSS) at Virginia Tech in the past. A novel evaluation method that nondimensionalizes the equations is used to allow for ease of use for LCVs with different cargo weights, lengths, and other similar variations. The dimensionless parameters are the function of vehicle parameters and express the relationship among the magnitude of vehicle parameters. Using the nondimensionalized model, the study performs a frequency analysis of the effect of trailer cargo weight, CG longitudinal position, and trailer wheelbase on roll stability and rearward amplification. Rearward amplification is the ratio of peak lateral acceleration between the tractor and the rearmost trailer. Slow-sweeping sinusoidal steering from 0.01 Hz to 0.6 Hz is used for the simulation analysis. The simulation results show that by increasing the trailer wheelbase—the distance from the trailer kingpin to the axle—the vehicle is more laterally stable because the longer wheelbases make the trailer more resistive to spinning around. Additionally, the pneumatic disc and drum brake models and thermal models are developed and coupled with the vehicle dynamic model. The disc and drum brake braking performance are investigated during both straight-line braking and combined steering and braking in a curve. The disc brakes generate a greater brake torque compared with drum brakes, and as such can decelerate the vehicle more efficiently on dry road surfaces, particularly at higher speeds such as highway speeds. This improves avoidance during emergency stops and roll stability during traveling in a curve, such as at a highway exit. The disc brakes also have greater cooling capacity because they can transfer the generated heat to the air due to the greater airflow and turbulence caused naturally by their design. This greatly helps to keep the brakes cooler on the track and to improve their stopping efficiency.

This thesis explores the concept of using sensors found in normal vehicles, also known as probe vehicles, to collect road infrastructure data. This concept was demonstrated by measuring vertical acceleration using in-vehicle sensors in order to describe road ride quality. Data collection was performed at the Virginia Smart Road using two instrumented vehicles. The gathered information was compared to road profile data collection, which is the current state-of-the-practice in ride quality assessment. Following the concept validation, the acceleration measurements were further analyzed for repeatability and effect of various independent variables (vehicle speed and type). A network-level simulation was completed using the robust set of measurements from the experiment. In addition, methodology for identifying rough sections and locations were established. Results show that under controlled testing conditions, roadway profile can accurately be estimated using probe vehicle acceleration data and may provide a more practical way to measure road smoothness. The analysis also showed that vertical acceleration data from a fleet of probe vehicles can successfully identify poorly-conditioned pavement areas. This suggests that instrumented probe vehicles might be a viable and effective way of implementing a network level roadway health monitoring program in the near future. / Master of Science

With the number of deaths, commute time, and injuries constantly rising due to human driving errors, it’s time for a new transportation system, where humans are no longer involved in driving decisions and vehicles are the only machine that decide the actions of a vehicle. To accomplish a fully autonomous world, it’s important for vehicles to be able to communicate instantly and report their movements in order to reduce accidents. This paper discusses four approaches to vehicle to vehicle communication, as well as the underlying standards and technology that enable vehicles to accomplish communicating.

Roads are essential in modern societies, but as populations grow and traffic volumes rise, roads will continue to be built and expanded. As a result, the effects that roads have on wildlife will likely intensify, making it imperative that managers understand those effects so mitigation can be directed accordingly. In Utah, considerable areas of mule deer (Odocoileus hemionus) habitat have been bisected by roads. Mule deer are commonly involved in vehicle collisions and there is concern that roads and vehicle traffic are impacting populations. This project was conducted to determine the number and demographic effects of deer-vehicle collisions, to examine how movements and survival of deer were impacted by roads, and to develop a smartphone-based reporting system for wildlife-vehicle collisions. Accurate estimates of DVCs are needed to effectively mitigate the effects of roads, but great uncertainty exists with most deer-vehicle collision estimates. I estimated the number of deer-vehicle collisions using carcass surveys, while accounting for several sources of bias to improve accuracy. I estimated that 2-5 % of the statewide deer population was killed in vehicle collisions annually. The effect that vehicle collisions have on deer abundance depended not only on the number of deer killed but also on the demographic groups removed. I found that 65 % of deer killed in vehicle collisions were female and 40 % were adult females. As female deer are the primary drivers of population growth, my data suggest vehicle collisions could significantly affect population abundance. However I was unable to detect a decreasing trend in deer abundance. Deer have distinct movement patterns that affect their distribution in relationship to roads. I analyzed deer movements during two consecutive winters (2010-11 & 2011-12) to determine what effect climate had on deer movements and vehicle collision rates. I observed that as snow depth decreased, the distance that deer occurred from roads increased. As a result road crossing rates declined, as did the number of vehicle collisions. This suggests a causal mechanism by which winter conditions influence vehicle collision rates. Currently there is a need for an efficient wildlife-vehicle collision data collection. I envisioned and, working with colleagues, helped develop a smartphone-based system for reporting wildlife-vehicle collision data. The WVC Reporter system consisted of a mobile web application for data collection, a database for centralized storage of data, and a desktop application for viewing data. The system greatly improved accuracy and increased efficiency of data collection efforts, which will likely result in improved mitigation and ultimately increased safety for motorists and deer.

This thesis evaluates a series hybrid electric drivetrain design for use in parking patrol vehicles. Due to the particular attributes of this application, it is proposed that the design would improve the energy efficiency of such a vehicle. The scheme is evaluated in depth through the use of electromagnetic transient simulation tools, which are used to create a highly accurate model of the vehicle. A prototype vehicle of the same design is built, and used to verify and improve the accuracy of the simulation model. The simulation model is then used to predict the energy efficiency of the series hybrid design for parking patrol. This simulation based design strategy is proposed as a method for more rapid and cost effective design of hybrid electric vehicles. / October 2007

No description available.

A plug-in hybrid electric vehicle (PHEV) is a vehicle powered by a combination of an internal combustion engine and an electric motor with a battery pack. The battery pack can be charged by plugging the vehicle into the electric grid or from using excess engine power. A PHEV allows for all electric operation for limited distances, while having the operation and range of a conventional hybrid electric vehicle on longer trips. A PHEV design with design parameters electric motor size, engine size, battery capacity, and battery chemistry type, is optimized with minimum cost as a figure of merit. The PHEV is required to meet a fixed set of performance constraints consisting of 0-60 mph acceleration, 50-70 mph acceleration, 0-30 mph acceleration in all electric operation, top speed, grade ability, and all electric range. The optimization is carried out for values of all electric range of 10, 20, and 40 miles. The social and economic impacts of the optimum designs in terms of reduced gasoline consumption and carbon emissions reduction are calculated. Argonne National Laboratorys Powertrain Systems Analysis Toolkit is used to simulate the performance and fuel economy of the PHEV designs. The costs of different PHEV components and the present value of battery replacements over the vehicles life are used to determine the designs drivetrain cost. The resulting optimum PHEVs are designs using lead acid battery type. The optimum design parameter values are all determined by a single controlling performance constraint. The PHEV designs show a 63% to 80% reduction in gasoline consumption and a 53% to 47% reduction in CO2 emissions. The PHEV designs have an annual gas savings of $696 to $643 per year over the average sedan meeting the 27.5 mpg CAFE standards.

This thesis evaluates a series hybrid electric drivetrain design for use in parking patrol vehicles. Due to the particular attributes of this application, it is proposed that the design would improve the energy efficiency of such a vehicle. The scheme is evaluated in depth through the use of electromagnetic transient simulation tools, which are used to create a highly accurate model of the vehicle. A prototype vehicle of the same design is built, and used to verify and improve the accuracy of the simulation model. The simulation model is then used to predict the energy efficiency of the series hybrid design for parking patrol. This simulation based design strategy is proposed as a method for more rapid and cost effective design of hybrid electric vehicles.

This thesis evaluates a series hybrid electric drivetrain design for use in parking patrol vehicles. Due to the particular attributes of this application, it is proposed that the design would improve the energy efficiency of such a vehicle. The scheme is evaluated in depth through the use of electromagnetic transient simulation tools, which are used to create a highly accurate model of the vehicle. A prototype vehicle of the same design is built, and used to verify and improve the accuracy of the simulation model. The simulation model is then used to predict the energy efficiency of the series hybrid design for parking patrol. This simulation based design strategy is proposed as a method for more rapid and cost effective design of hybrid electric vehicles.

No description available.