Thesis (MScIng)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

D.Econ.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 115-125). Also available via the Internet.

Thesis (M.S.)--University of Wisconsin--Madison, 1966. / eContent provider-neutral record in process. Description based on print version record.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2007. / Noise, Vibrations and Harshness (NVH) characteristics are becoming ever more significant in today’s vehicle manufacturing industry. Similar to good vibration and harshness characteristics, the perception of a vehicle’s quality is enhanced by a well sounding vehicle interior. This study’s main aim was to develop objective equations to directly optimise interior sound quality of light commercial vehicles ( ½ ton LCVs) on the South African market. The effects the noise of the engine, the wind and road/tyre interaction during steady-state conditions have on the interior sound quality of eleven comparable vehicles was investigated with the aid of a binaural head. Steady-state condition in this content refers to the fact that vehicles were tested at constant speeds, no acceleration involved. A strong emphasis was laid on the influence road noise has on the interior sound quality of LCVs. Other objectives for the thesis were, to provide a method to benchmark the interior SQ of LCVs and to develop target values for objective metrics for these vehicles. Establishing a comprehensive literature survey formed another objective of this study. It seeks to provide a summary of the modern SQ analysis procedure and the findings of a number of studies. The survey also presents an opportunity to compare this thesis’s results with previous studies. A last objective was to develop a list of possible hardware modifications that would improve the vehicle interior sound quality, influenced by different noise sources. A strong correlation between vehicle and engine speed and Zwicker loudness as well as Aure sharpness was found, for all test conditions. The road surface roughness was observed to also have a strong influence on the objective metrics of vehicle interior SQ. Loudness was found to be around 25% higher and sharpness around 5.6% lower in vehicles driving on rough tar roads than on smooth roads. Good correlations between a newly developed metric (the SPF), an equation in Zwicker loudness and Aure sharpness, and subjective ratings was obtained for a number of test conditions. Four objective equations, as well as target values for loudness and sharpness have been developed to objectively optimise the sound quality of LCVs. Benchmarking interior sound quality utilising the developed equations, will ensure continuous improvements in the SQ sector for future LCVs.

The Commercial Vehicle Safety Alliance (CVSA) is an association of industry representatives, and state, territorial, provincial, and federal government officials in the United States, Canada, and Mexico. The CVSA's goal is to improve commercial vehicle safety. The CVSA concentrates its safety focus on three areas; driver, vehicle, and hazardous materials. Since 1981, the CVSA has developed a set of criteria for each of the three areas that define conditions which are so unsafe that a truck and/or driver should not be allowed to operate. These criteria are known as out of service (OOS) criteria. To check the compliance of motor carriers with the CVSA criteria, a series of road side inspections is conducted by state and local governments. If the driver and/or vehicle are found in violation of the CVSA OOS criteria, they are placed "out of service" until the conditions are completely remedied. Due to criteria growth, the CVSA wanted to examine the OOS criteria in the vehicle and hazardous materials areas. This study, focused on the vehicle portion of the OOS criteria, attempted to correlate commercial vehicle defects to commercial vehicle accidents. For a major portion of this project, actual accident reports from six states of the United States were evaluated. The states and reports were selected via a stratified two stage cluster sampling system. The results were used to form estimates of the proportion and number of commercial vehicle accidents in the United States with a mechanical defect as a contributing factor. In addition to the accident report sampling, other sources were used to establish a correlation between vehicle defects and commercial vehicle accidents. They include literature, national databases, and post-crash inspections. Results from this study show that approximately 4.6% of all commercial vehicle accidents have a mechanical defect as a factor contributing to the accident. Of these, brakes (1.66%), tires (0.45%), couplings (0.38%), load securement (0.37%), and wheels (0.33%) accounted for the majority. A comparison was also made between the OSU study results and the information gathered from other sources. A cost factor was also used to rank the accidents. The sampled accidents accrued $22.7 million in damage to people and property. The underlying assumption is vehicle defects that are strongly represented in accidents and accident damage estimates should have a strong representation in the out-of-service criteria. / Graduation date: 1997

The air brake system is one of the critical components in ensuring the safe operation of any commercial vehicle. This work is directed towards the development of a fault-free model of the pneumatic subsystem of the air brake system. This model can be used in brake control and diagnostic applications. Current enforcement inspections are done manually and hence are time consuming and subjective. The long-term objective is to develop a model-based, performance-based diagnostic system that will automate enforcement inspections and help in monitoring the condition of the air brake system. Such a diagnostic system can update the driver on the performance of the brake system during travel and with recent advancements in communication technology, this information can be remotely transferred to the brake inspection teams. Since this system is performance-based, it will eliminate the subjective nature of visual inspections. The first step in the development of such a diagnostic system is to obtain a fault-free model of the air brake system. The model of the pneumatic subsystem correlates the pressure transients in the brake chamber with the brake pedal actuation force and the brake valve plunger displacement. An experimental test bench was set up at Texas A&M University and the experimental data is used to corroborate the results obtained from the model.

This research is focused on developing a control scheme for regulating the pressure in the brake chamber of an air brake system found in most commercial vehicles like trucks, tractor-trailers and buses. Such a control scheme can be used for providing the ground work for future systems such as forward collision avoidance systems, advanced anti-lock brake systems and differential braking systems. The development of this controller involves two tasks. The first task was the development of a control scheme for achieving the desired pressure in the brake chamber. This scheme was based on a mathematical model of the treadle valve of the air brake system. The second task was the implementation of this control scheme on the experimental facility that was set up at Texas A&M University. The results indicate successful control of a desired brake chamber pressure for a demonstrated range of controller gains.

The air brake system is one of the critical components in ensuring the safe operation of any commercial vehicle. This work is directed towards the development of a fault-free model of the pneumatic subsystem of the air brake system. This model can be used in brake control and diagnostic applications. Current enforcement inspections are done manually and hence are time consuming and subjective. The long-term objective is to develop a model-based, performance-based diagnostic system that will automate enforcement inspections and help in monitoring the condition of the air brake system. Such a diagnostic system can update the driver on the performance of the brake system during travel and with recent advancements in communication technology, this information can be remotely transferred to the brake inspection teams. Since this system is performance-based, it will eliminate the subjective nature of visual inspections. The first step in the development of such a diagnostic system is to obtain a fault-free model of the air brake system. The model of the pneumatic subsystem correlates the pressure transients in the brake chamber with the brake pedal actuation force and the brake valve plunger displacement. An experimental test bench was set up at Texas A&M University and the experimental data is used to corroborate the results obtained from the model.

Thesis (M. Sc.)--University of Hong Kong, 1997. / Includes bibliographical references (leaf 88-91).