Semi-active dampers utilizing various working principles have been developed for a variety of vehicles. These semi-active dampers have been designed to resolve the ride and handling compromise associated with conventional passive dampers, and increase vehicle stability. This thesis briefly reviews existing semi-active damper designs, including but not limited to MR dampers, before presenting two new prototype semi-active hydraulic dampers. Both prototype dampers are designed to provide a large force range while maintaining easily controllable valve characteristics. The first of these dampers served primarily as a proof of concept and a means of understanding the dynamics of a disc valve housed inside the main piston. The valve design is presented, along with other information concerning the fabrication of the Initial Prototype damper. Test results are presented and analyzed, and a second iteration of the valve is designed. The Final Prototype damper is a scaled up version of the initial design, with refinements made in piston geometry, internal disc profile, and dynamic seals. This large force range damper is tested and results are compared with existing MR dampers. The Final Prototype damper provides a significantly larger force range when compared with typical MR dampers. Finally, to conclude this research, the vehicle dynamics implications of the Final Prototype damper are discussed and recommendations for further study are made. / Master of Science

The effects of weigh-in-motion (WIM) systems on traffic operations and weight enforcement were compared and evaluated. The systems studied included high speed WIM, medium speed WIM and conventional static scales alone. The major measurements of effectiveness were traffic delay, queue, and the avoidance rate for overweight vehicles. Four weighing facilities from both the eastern and western United States were chosen as the real life bases for the study. Queuing theories, probability and statistics were the major methodologies employed in the study. The characteristics of queuing systems, such as traffic arrival patterns, weight enforcement processing time distribution, and capacity of the static scales at each weigh station were determined through field data collection at weigh stations. The proportion of the vehicle population directed to the static scale by WIM screening was analyzed, based on WIM accuracy and truck weight distributions at or near each weigh facility. By considering delay, queue, and the avoidance rate of overweight vehicles comprehensively, optimal weighing systems are proposed for different V/C ratios, i.e., the ratio of traffic volume at a specific site to the actual capacity of the static scale. When the V/C ratio is less than 1, a weighing facility using a static scale alone is most cost effective; when the V/C ratio is between 1 and 1.5, a medium speed WIM is suggested. High speed WIM is recommended only when the V/C ratio is larger than 1.5. / Master of Science

Driver distraction has become a major concern for the U.S. Department of Transportation (US DOT).  Performance decrements are typically the result of driver distraction because attentional resources are limited, which are limited; fatigue and drowsiness limit attentional resources further.  The purpose of the current research is to gain an understanding of the relationship between mobile device use (MDU), fatigue, through driving time and time on duty, and drowsiness, through time of day and amount of sleep, for commercial motor vehicle drivers.  A re-analysis of naturalistic driving data was used to obtain information about the factors, MDU, safety-critical events (SCE), and normal driving epochs.  Odds ratios were used to calculate SCE risk for 6 mobile device use subtasks and each of the factors, which were divided into smaller bins of hours for more specific information.  A generalized linear mixed model and chi-square test were used to assess MDU for each factor and the associated bins.  Results indicated visually demanding subtasks were associated with an increase in SCE risk, but conversation on a hands-free cell phone decreased SCE risk.  There was an increase in SCE risk for visual manual subtasks for all bins in which analyses were possible.  Drivers had a higher proportion of MDU in the early morning (circadian low period) than all other times of day that were analyzed.  These results will be used to create recommended training and evaluate policy and technology and will help explain the relationship between MDU, fatigue, and drowsiness. / Master of Science

In this study, trucks or large trucks are defined as straight trucks (ST-TR) also known as single unit trucks having a single body without any hitch between the loading section and front driving mechanism, tractor trailers (TR -TR) having two bodies coupled by a hitch, and twin tractor trailers (TW-TR) with front driving mechanisms towed by a double trailer. Vehicle miles of travel (VMT) for these trucks have been steadily increasing for the past five years (1986-1990) showing a continuous growth in transportation goods both inside and outside of the State of Virginia. The objective of this research is to identify the major factors associated with truck overturns occurring on which occurred between 1986 and 1990, on the main line of the Virginia Interstate System in general and 1-81 in particular. / Master of Science

This research provides a thorough flow characterization study to compare the functionality of two types of load-leveling valves that are commonly used for air suspension systems of commercial trucks. The first valve features a simple disk/slot design and is relatively compact for installation. The second type is larger and has a sophisticated, chambered design, which allows for considerably quicker fill and exhaust response times in the transient region. A new approach is introduced to estimate the transient mass flow rate of a load-leveling valve under different suspension pressures, without requiring a mass flow meter. An extensive series of dynamic tests are conducted to characterize and compare the two load-leveling valves. A generic heavy-truck pneumatic suspension, consisting of load-leveling valves, airspring, air tank, and air-hose fittings, is configured for testing. The test setup is used to evaluate the transient performance of each type of load-leveling valve in a typical truck suspension. The flow behavior of the system is validated by the force/pressure responses of the air spring due to various displacement excitations. The experimental results describe the detailed flow behavior of both valves. The flow characterization results can be incorporated as one of the most critical parameters for future model development of pneumatic systems. The tests indicate that the leveling valve with chambered design has a far faster transient flow response than the disk valve, although it is more complicated in its mechanical design and therefore costs more. To take advantage of the design simplicity of the disk valve, while also enabling it to have a faster transient response (compared with the chambered design), it is re-designed with larger flow openings and other elements to match the performance of the chambered valve for transient flow. A comparison of the experimental results and simulations validates that the re-designed rotary disk valve performs nearly the same as the chambered valve, but is simpler and costs less. The study's results are directly applicable to improving the transient dynamics of heavy truck air suspensions by providing a better understanding of how load-leveling valves can be used not only to provide ride-height control, but also to influence the roll and pitch dynamics of heavy trucks. / Master of Science

Currently, in the railroad industry, the lack of electrical sources in freight cars is a problem that has yet to find practical solutions. Although the locomotive generates electricity to power the traction motors and all the equipment required to operate the train, the electrical power cannot, in a practical manner, be carried out along the length of the train, leaving freight cars unpowered. While this has not been a major issue in the past, there is a strong interest in equipping modern cars with a myriad of devices intended to improve safety, operational efficiency, or health monitoring, using devices such as GPS, active RFID tags, and accelerometers. The implementation of such devices, however, is hindered by the unavailability of electricity. Although ideas such as Timken's generator roller bearing or solar panels exist, the railroads have been slow in adopting them for different reasons, including cost, difficulty of implementation, or limited capabilities. The focus of this research is on the development of vibration-based electromechanical energy harvesting systems that would provide electrical power in a freight car. With size and shape similar to conventional shock absorbers, these devices are designed to be placed in parallel with the suspension elements, possibly inside the coil spring, thereby maximizing unutilized space. When the train is in motion, the suspension will accommodate the imperfections of the track, and its relative velocity is used as the input for the harvester, which converts the mechanical energy to useful electrical energy. Beyond developing energy harvesters for freight railcar primary suspensions, this study explores track wayside and miniature systems that can be deployed for applications other than railcars. The trackside systems can be used in places where electrical energy is not readily available, but where, however, there is a need for it. The miniature systems are useful for applications such as bicycle energy. Beyond the design and development of the harvesters, an extensive amount of laboratory testing was conducted to evaluate both the amount of electrical power that can be obtained and the reliability of the components when subjected to repeated vibration cycles. Laboratory tests, totaling more than two million cycles, proved that all the components of the harvester can satisfactorily survive the conditions to which they are subjected in the field. The test results also indicate that the harvesters are capable of generating up to 50 Watts at 22 Vrms, using a 10-Ohm resistor with sine wave inputs, and over 30 Watts at peak with replicated suspension displacements, making them suitable to directly power onboard instruments or to trickle charge a battery. / Ph. D.

Changes in production of truck crops in principal producing areas, and changes in market demand changes in market demand for the consumption of these crops, have intensified the problem of successful marketing. Studies are being made to determine the cause of these changes as well as the effect of the results upon the producers. An attempt is made here to present the part of the picture which shows the extent of commercial truck crop supplies from states (or areas) competing with similar supplies from Virginia. / Master of Science

This study includes an experimental evaluation of a prototype trailing-arm suspension for heavy trucks. The primary goal of this new suspension is to match or improve the kinematics and dynamic performance of an existing "Z-bar" suspension. Significant reductions in cost, weight, and number of parts are the main reasons for this redesign. A permanent facility is constructed to support the testing of different heavy truck suspensions. For actuation of the vehicle suspension, hydraulic actuators are used in the kinematics tests in a quasi-dynamic manner. For the dynamic tests, the vehicle is excited using two hydrodynamic actuators. A collection of forces, displacements, velocities, and accelerations are measured during the tests using transducers that were installed on the suspension and test vehicle. The test measurements are analyzed in both time and frequency domains and then the results of the two suspensions were compared to establish the dynamic merits of the prototype suspension. The kinematics tests include vertical stiffness, roll stiffness, and roll steer measurements for each suspension. The results from the kinematics tests show that the trailing-arm suspension exhibits kinematics traits that are quite similar to the "Z-bar" suspension, within the context of the tests conducted in the study. The dynamic testing consists of three input signals commonly used for such tests, namely: a chirp signal input, a step signal input, and a range of pure tone inputs. The test results show that the resonant frequencies of the two primary suspensions differ by an amount that is most likely too small to affect ride dynamics. The two suspensions, however, exhibit significantly different damping characteristics. The new suspension has much less frictional damping than the existing suspension. This is expected to provide better ride characteristics, assuming that the primary dampers (shock absorbers) are properly tuned for the vehicle that the new suspension was designed for. / Master of Science

A digital controller was designed for a semiactive primary suspension for a class 8 highway truck. The controller used a skyhook policy (where the semiactive damper simulates a damper between the sprung mass and an inertial reference) to control magneto-rheological dampers placed on the truck 's primary suspension in response to measurements made by accelerometers placed on the axle and the truck frame. The completed system was then tested for both random noise (on highway driving) and impulse (speed bump) response. The test results showed that for the damping tuning and controller arrangements used in this study, semiactive dampers do not offer any significant benefits in reducing overall vibration levels at the truck frame or axles. The semiactive dampers, however, provided better control of the dynamic transients, such as roll and pitch induced by hitting speed bumps, as compared to passive dampers. Further assessment of the magneto-rheological damper's tuning and the skyhook control policy is needed to establish any definitive conclusions on the potential benefits of semiactive magneto-rheological suspensions for heavy trucks. / Master of Science

<p><strong>Title:</strong> Volvo Trucks' Customer Value Proposition</p><p><strong>Authors:</strong> Ekaterina Storubleva, Gregor Milosch, Christian Neumann</p><p><strong>Tutor:</strong> Erik Hunter</p><p><strong>Date:</strong> May 2009</p><p><strong>Keywords:</strong></p><p><strong></strong>Volvo Truck Corporation, truck industry, customer value, value drivers, retail strategy, communication, relationship marketing</p><p><strong>Purpose:</strong></p><p><strong></strong>The purpose of this thesis is to evaluate the general composition of Volvo Trucks' customer value proposition in Europe and to examine possible ways of enhancing it using Volvo's retailing strategy as a tool.</p><p><strong>Background:</strong></p><p><strong></strong>The concept of customer value gains more and more importance in modern companies. Firms have to truly understand what their customers expect in order to provide the right products for them.Truck manufacturing is a very cyclical industry, which is why in times of crisis, when trade volumes go down, they need to excel even more in order to maintain good business relations with their customers. Volvo Trucks, one of the world's leading truck producers, has adopted a special retailing strategy, in which it owns strategically important dealerships, in order to improve customer understanding and consequently customer value. This paper discusses in how far they succeed at this.</p><p><strong>Method:</strong></p><p><strong></strong>The authors followed a triangular approach, combining quantitative and qualitative research. The quantitative part was covered by a communication chain study and a value driver study, both developed by the authors. In the qualitative part, each participant answered ten open questions, which were then used for internal consistency checks and contributed additional thoughts.</p><p><strong>Conclusion:</strong></p><p><strong></strong>The Volvo Truck Corporation (VTC), by adapting its retail strategy, realized the importance of establishing long-term customer relationships and generating adequate intelligence about customer needs. The company not only incorporated influential elements of relationship marketing but also strives for sustainable improvements in customer-perceived value. However, some conflicts between the stakeholder groups involved have been discovered. The corporation's core values were found to be in line with customer preferences.</p><p>In essence, it is crucial for Volvo Trucks to implement the ideas of relationship marketing, establish superior communication channels, and to promote a common understanding of customer value.</p>