This dissertation covers the design and manufacture of an autonomous guided cart (AGC) for use in the material handling industry. General Motors South Africa (GMSA) requires a low-cost AGC for use in their Struandale plant. A budget of R35 000 per unit was proposed. The researcher, in collaboration with staff at GM, compiled a list of engineering requirements for the AGC. After research into the unique problems of the project, an examination of a previous design attempt by staff of GM Thailand, the researcher developed a new design, the subject of this report. Different solutions for each design problem were investigated before the design was finalised. A three-wheeled vehicle was designed making use of two motors in a differential-drive setup to control motion. Navigation is via a line-following mechanism, using an induction sensor-array in conjunction with a pre-laid metallic strip. To aid the design, the system was modelled to understand the different control elements at play. The researcher developed software for several aspects of the design: for the PLC controlling the system and motors; for a microcontroller that communicates with the PLC and a wireless module; for a computer server that communicates with a second wireless device, receiving information from the PLC; and a web interface to view this information. These form the SCADA integration of the project. The final product meets the GMSA specifications. It is a robot capable of towing a trolley of mass not exceeding 350 kg. While the robot is able to navigate a pre-laid route, it cannot reliably stop at marked locations. It is possible to monitor the system via a web-interface. The robot is capable of operating for an entire 8-hour shift before the batteries need to be recharged. The total cost of the prototype was R26 340.

This thesis presents an investigation of the influence of turbocharging on the performance and combustion behaviour of a dual fuelled, spark-ignition engine fuelled with natural gas and gasoline. The investigation was carried out using a combination of experimental and analytical methods. The experimental data was obtained from an instrumented, four cylinder, Toyota engine mounted in a test cell. An electrically driven Roots blower was used to provide compressed air to the engine, and a restriction was placed in the exhaust pipe to simulate the effects of an exhaust-driven turbine. Cylinder pressure data were recorded and analysed using a computer routine in order to provide information on mass burning rates and burning velocities. Computer routines were also developed to simulate the compression, combustion and expansion processes in the engine. It was found that the laminar burning velocity of natural gas is 50% to 60% lower than gasoline, under engine-like conditions of temperature and pressure. Mass-burning rate analyses of measured cylinder pressure data showed that the lower burning velocity of natural gas has its greatest influence during the ignition delay period (up to 1% mass burned) and that it can cause increases in ignition delay of between 50% and 100% relative to gasoline. It was observed that the low burning velocity of natural gas also affects the main combustion period, but to a much lesser extent, increasing it by up to 10% relative to gasoline. It was concluded that the main combustion period is dominated by turbulence effects and that it is relatively unaffected by variations in fuel type, air/fuel ratio or boost pressure. Results from the engine tests and simulation program indicated that it is possible to recover the power loss experienced by an engine running on natural gas by boosting the intake pressure to 3 psig (20 kPa) above that provided when the engine is running on gasoline. This increase in boost pressure does not significantly reduce the efficiency or raise the specific fuel consumption. It was found, however, that the peak cylinder pressures attained can be as much as 20% higher on natural gas than on gasoline at the same power level. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

A large percentage of automobile accidents in city traffic occur at speeds below 15 mph. Unfortunately there is a scarcity of experimental crash data at these low speeds to help investigators to reconstruct accidents. Accident reconstruction experts have consequently attached a low level of confidence to speed predictions from vehicle crush at the low end of the speed spectrum. The need for more experimental crash data, especially in a low speed range, has repeatedly been mentioned by accident investigators. The University of British Columbia Accident Research Croup has constructed a crash test facility in conjunction with the Insurance Corporation of British Columbia to address this need. The lCBC-UBC barrier is a low speed crash test facility. A description of the ICBC-UBC crash barrier, its systems and crash testing techniques at the ICBC-UBC facility are presented in this thesis. Also multiple impacts on the same vehicle are investigated to see if this technique provided accumulated crush data that reproduced known high speed crashes. In addition, the preliminary findings are presented on the impact speed to initiate permanent crush and subsequent implications toward vehicle crush characteristics in a low speed range. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

No description available.

Automotive catalytic converters are increasingly used to reduce emissions from internal combustion engines to comply with emission regulations. Maldistributed flow across the catalyst affects its warm up, light off time, ageing, and conversion efficiency. This thesis concerns flow distribution in automotive catalytic converters and methods to improve CFD predictions. Previous studies showed that modelling the monolith flow resistance using the Hagen- Poiseuille’s formulation under predicted flow maldistribution. The predictions were improved by incorporating an additional pressure loss term V2 2 1  , where V is transverse velocity just upstream of a monolith channel, for oblique entry of the flow into the monolith known as the entrance effect. Further improvement was obtained by incorporating the critical angle of attack method. However, there was no experimental evidence to support these oblique entry loss formulations. There also remained the possibility that under prediction of flow maldistribution might be due to the failure to predict flow in the diffuser accurately. A one-dimensional oblique angle flow rig was designed and built to measure the effect of oblique entry flow losses in monoliths. Experiments were performed at different angles of attack (α), using different lengths of substrate and a methodology was developed to obtain the oblique flow entrance losses. The results showed that the pressure loss attributed to the entrance effect increased with the angle of attack. The entrance effect was also found to be dependent on channel Reynolds number and substrate length. The theoretical assumption of V2 2 1  predicts accurately at low Reynolds number but looses its validity at high Reynolds number. From the experimental studies, an improved correlation for the entrance effect has been derived as a function of major controlling variables, i.e., angle of attack, length of the substrates and Reynolds number. A two-dimensional rig was designed to measure the flow field using PIV in a 2-D diffuser placed upstream of two different length substrates. The results showed that the flow in a wide angle diffuser consisted of a central core, free shear layer and recirculation regions. The near-field region was found similar to that of a plane jet. The flow field was found to be independent of Reynolds number. Increasing the substrate length resulted in a flattening of the axial profiles close to the substrate face. A CFD study was undertaken to predict maldistributed flow at the exit of the substrate for an axisymmetric catalyst model by incorporating the measured entrance effect correlation. A fixed critical angle of attack (αc,F) approach was used whereby the entrance effect is assumed constant for α>αc,F. Incorporating the entrance effect with αc,F= 810 improved the prediction of maldistribution in the flow profiles. A 2-D CFD study was undertaken to predict the flow distribution in the diffuser and downstream of the substrate. A comparison of the CFD predictions in the diffuser using different turbulence models showed that all the turbulence models used in this study over predicted the width of the central core region and the V2F turbulence model gave velocity predictions that compared best with PIV. Incorporating the entrance effect improved the predictions close to the diffuser-substrate interface and downstream of the substrate.

The research of this thesis was performed to understand the vibrational dynamics of stage 0&1 child safety seats and of the children who occupy them. Since no previous vibration data for small children or child seats was found, the investigation took the form of experiments designed to shed light on the behaviour of the system consisting of child, child seat, vehicle safety belt and vehicle seat. To provide a background for interpreting the results a literature review was performed of child seat characteristics, of human whole-body response and of primate whole-body response. An industrial test procedure for measuring the vibration isolation properties of vehicular seats is also presented as an illustration of the concepts involved. A whole-body vibration bench for testing children in the vertical direction was built and apparent mass and absorbed power functions were measured for 8 children of age less than 24 months and mass less than 13 kg. An algorithm was developed for identifying the parameter values of a single degree of freedom mass-spring-damper model of the seated body using Differential Evolution optimisation. The parameter values were determined for each child and compared to those of adults and primates. This thesis also presents the results of modal testing of 2 child seat units and of operational deflection shape testing of 1 unit in an automobile under 3 loading conditions (empty, sandbag or child). In-vehicle transmissibility measurements were also performed in the vertical direction for 10 children and child seats using 9 automobiles. The floor-to-human transmissibilities were determined for each child and driver when passing over a reference road surface at both 20 and 40 km/h. Except for the damping ratio, all child mechanical response parameters were found to differ with respect to those of adults or primates, with the differences being greater with respect to adults. The first resonance frequency of children was found to be located at 8.5 Hz as opposed to 4.0 Hz for adults, raising questions regarding the applicability of standards such as ISO 2631 towards the evaluation of child vibrational comfort. The child seats were found to have higher transmissibilities on average than the vehicular seats occupied by adults. A characteristic low frequency rigid body rocking motion was noted at 1.8 Hz as were multiple flexible body resonances starting from frequencies as low as 15 Hz. Areas of possible improvement and topics for further research have been identified.

No description available.

Digitized by Kansas Correctional Industries

This research studied the tractive performance of integrated steering-drive systems by investigating a two-wheel-drive vehicle having two independent rear drive wheels and non-driven steerable front wheels. The feasibility of integrating the steering and drive systems and the performance advantages that may be obtained was investigated. In order to demonstrate the feasibility of the concept, the steering system and the drive system of a test vehicle were integrated using a computer with a specially-developed program. The software algorithm developed for the program used the mathematical relationship between the rear drive wheel speeds and the steer angles of the non-driven front wheels to set the steer angles. A test-bed vehicle was fitted with instrumentation to implement the computer-integrated system. The circuitry of the hydraulic lines of the hydraulically-driven test vehicle was modified to allow changes in drive configuration. These changes are not possible with conventional vehicles. The test vehicle could be configured for the following steering-drive configurations: open differential rear drive with steerable front wheels, independent rear drive wheels with front castors, locked differential rear drive with steerable front wheels and the computer-integrated steering-drive system developed. The sensors on the vehicle allowed data collection for characterising the vehicle and wheels. omputer models were developed for the various steering-drive configurations from the force relationships, longitudinal slip relationships, vehicle geometry and turning geometry. Characteristics of the test vehicle's wheels for use in the models were measured experimentally. he models were used to simulate the behaviour, and calculate the tractive performance, of the four steering-drive configurations in various situations but actual tests were not able to be conducted with the available resources. Unlike previous models, the models of this research used force and longitudinal slip information rather than power input and power output to produce values for drawbar efficiency. theoretical analysis was conducted into the optimal slip conditions for maximum tractive efficiency. The analysis was conducted using a more rigorous mathematical analysis than previous researchers and used a thorough graphical analysis to substantiate the mathematical analysis. Previous studies concluded that under all traction conditions the efficiency of slip will be a maximum when the slip of each wheel is equal. This research revealed that, contrary to the previous literature, efficiency of slip will not be a maximum when the slip of each wheel is equal under non-uniform traction conditions. The simulations were focussed on turning situations, non-uniform traction conditions and traversing slopes. The optimal slip conditions and steer angles for turning situations were also investigated and analysed. The computer-integrated steering-drive system achieved a drawbar pull 50% higher than that for a conventional open differential when undertaking a 10 m radius turn with non-uniform traction conditions. Under these conditions, the drawbar efficiency of the computer-integrated steering-drive system was 5% greater than that for the open differential at the lower drawbar pull. It was concluded that it is feasible and beneficial to use a computer-integrated steering system. Vehicles using such a system would operate more effectively and efficiently when turning under load, moving across slopes and in non-uniform traction conditions. More effectiveness was provided through greater drawbar pull and higher drawbar efficiency. / thesis (PhD)--University of South Australia, 2005.

An important part of automobile safety is the braking system. Disc brakes have been widely used in automobiles for sped retardation for over 30 years. During that time, they have developed from a simple disc to a complex disc with channels, vanes, holes and grooves. The stopping capability of disc brakes is affected by the rate at which heat is dissipated by forced convection and the thermal capacity of the rotor. Catastrophic failure of brake rotors can occur during rapid increases or decreases in rotor temperature where regions of high temperature gradients result in high thermal strains. There is little information in the public domain regarding the relative merits of different disc brake rotor geometries, particularly in terms of airflow patterns, heat transfer rates, and internal thermal gradients. The aim of this research project was to investigate how geometrical variations affect the thermal performance of bi-directional disc brake rotors, particularly for high performance applications. Dynamometer testing showed that respectable increases in braking performance are achievable with relatively simple machining modifications. Tuft and smoke visualization techniques provided a preliminary understanding of the airflow in the passages of three distinct bi-directional rotor designs. Particle Image Velocimetry was used for detailed flow measurements which supported the numerical simulations. Computational Fluid Dynamics was used to predict the airflow and heat transfer associated with eight bi-directional brake rotor designs. The results show that 'pillared' passage designs can achieve higher heat transfer rates than traditional straight radial vane designs and that the heat loss from pillared rotors is generally more uniform than from vaned rotors. Subsequent conjugate heat transfer simulations found that temperature gradients inside pillared rotors are typically lower than inside vaned rotors. Thus failure rates due to excessive thermal strain are expected to be lower for pillared rotors. It was shown that rotor selection based solely on heat transfer rates is inappropriate and different passage designs are suited to different applications. The findings of this research will directly benefit local disc brake manufacturers, who do not have resources to conduct thorough studies comparing the thermal characteristics of different brake rotor designs.