Browsing by Subject "Automotive"
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Item Feasibility of using the micro-deval test method as an aggregate production quality control tool(Texas Tech University, 2003-12) Hoare, Appa RaoNot available.Item Fuel economy modeling of light-duty and heavy-duty vehicles, and coastdown study(2009-05) Ates, Murat; Matthews, Ronald D.; Hall, Matthew J.Development of a fuel economy model for light-duty and heavy-duty vehicles is part of the Texas Department of Transportation’s “Estimating Texas Motor Vehicle Operating Costs” project. A literature review for models that could be used to predict the fuel economy of light-duty and heavy-duty vehicles resulted in selection of coastdown coefficients to simulate the combined effects of aerodynamic drag and tire rolling resistance. For light-duty vehicles, advantage can be taken of the modeling data provided by the United States Environmental Protection Agency (EPA) for adjusting chassis dynamometers to allow accurate determination of emissions and fuel economy so that compliance with emissions standards and Corporate Average Fuel Economy (CAFE) regulations can be assessed. Initially, EPA provided vehicle-specific data that were relevant to a physics-based model of the forces at the tire-road interface. Due to some limitations of these model parameters, EPA now provides three vehicle-specific coefficients obtained from vehicle coastdown data. These coefficients can be related back to the original physics-based model of the forces at the tire-road interface, but not in a manner that allows the original modeling parameters to be extracted from the coastdown coefficients. Nevertheless, as long as the operation of a light-duty vehicle does not involve extreme acceleration or deceleration transients, the coefficients available from the EPA can be used to accurately predict fuel economy. Manufacturers of heavy-duty vehicles are not required to meet any sort of CAFE standards, and the engines used in heavy-duty vehicles, rather than the vehicles themselves, are tested (using an engine dynamometer) to determine compliance with emissions standards. Therefore, EPA provides no data that could be useful for predicting the fuel economy of heavy-duty vehicles. Therefore, it is necessary to perform heavyduty coastdown tests in order to predict fuel economy, and use these tests to develop vehicle-specific coefficients for the force at the tire-road interface. Given these coefficients, the fuel economy of a heavy-duty vehicle can be calculated for any driving schedule. The heavy-duty vehicle model developed for this project is limited to pre-2007 calendar year heavy-duty vehicles due to the adverse effects of emissions components that were necessary to comply with emissions standards that went into effect January 2007.Item A fundamental approximation in MATLAB of the efficiency of an automotive differential in transmitting rotational kinetic energy(2012-05) Vaughn, James Roy; Matthews, Ronald D.; Bryant, Michael D.The VCOST budgeting tool uses a drive cycle simulator to improve fuel economy predictions for vehicle fleets. This drive cycle simulator needs to predict the efficiency of various components of the vehicle's powertrain including any differentials. Existing differential efficiency models either lack accuracy over the operating conditions considered or require too great an investment. A fundamental model for differential efficiency is a cost-effective solution for predicting the odd behaviors unique to a differential. The differential efficiency model itself combines the torque balance equation and the Navier-Stokes equations with models for gear pair, bearing, and seal efficiencies under a set of appropriate assumptions. Comparison of the model with existing data has shown that observable trends in differential efficiency are reproducible in some cases to within 10% of the accepted efficiency value over a range of torques and speeds that represents the operating conditions of the differential. Though the model is generally an improvement over existing curve fits, the potential exists for further improvement to the accuracy of the model. When the model performs correctly, it represents an immense savings over collecting data with comparable accuracy.Item Measuring China’s success in developing a framework for domestic innovation(2013-05) Schultz, Kaye Frances; Rai, VarunThis report attempts to assess the degree to which China is developing a framework that supports domestic innovative capacity. This framework is not a predefined set of components, but is instead a combination of political, institutional, market, and technology factors and linkages that support information flows, interactions between entities, and incentives necessary to increase domestic innovation. Literature suggests that factors contributing to this framework may be influenced by domestic policy, and this report attempts to identify Chinese policies that contribute to the development of this framework within the Chinese solar photovoltaic (PV) and automotive industries. This report uses patent and export data as proxies for innovation in these two industries to measure the presence of this framework. The data suggest that the framework supporting domestic innovation in China is further developed for the solar PV industry than the automotive industry, but that the solar PV industry is still far from leading global innovation. Finally, the report identifies potential factors that have contributed to the variations between these two industries, and challenges that both industries may face in the near future.Item Simulation, design, and experimental characterization of catalytic and thermoelectric systems for removing emissions and recovering waste energy from engine exhaust(2012-12) Baker, Chad Allan; Shi, Li, Ph. D.; Hall, Matthew John; Matthews, Ronald D.; Ezekoye, Ofodike A.; Raja, Laxminarayan L.An analytical transport/reaction model was developed to simulate the catalytic performance of ZnO nanowires as a catalyst support. ZnO nanowires were chosen because they have easily characterized, controllable features and a spatially uniform morphology. The analytical model couples convection in the catalyst flow channel with reaction and diffusion in the porous substrate material; it was developed to show that a simple analytical model with physics-based mass transport and empirical kinetics can be used to capture the essential physics involved in catalytic conversion of hydrocarbons. The model was effective at predicting species conversion efficiency over a range of temperature and flow rate. The model clarifies the relationship between advection, bulk diffusion, pore diffusion, and kinetics. The model was used to optimize the geometry of the experimental catalyst for which it predicted that maximum species conversion density for fixed catalyst surface occurred at a channel height of 520 [mu]m. A modeling study of thermoelectric (TE) vehicle waste heat recovery was conducted based on abundant and inexpensive Mg₂ Si[subscript 0.5] Sn[subscript 0.5] and MnSi[subscript 1.75] TE materials with consideration of performance at the system and TE device levels. The modeling study identified a critical TE design space of fill fraction, leg length, n-/p-type leg area ratio, and current; these parameters needed to be optimized simultaneously for positive TE power output. The TE power output was sensitive to this design space, and the optimal design point was sensitive to engine operating conditions. The maximum net TE power for a 29.5 L strip fin heat exchanger with an 800 K exhaust flow at 7.9 kg/min was 2.25 kW. This work also includes two generations of TE waste heat recovery systems that were built and tested in the exhaust system of a Cummins 6.7 L turbo Diesel engine. The first generation was a small scale heat exchanger intended for concept validation, and the second generation was a full scale heat exchanger that used the entire exhaust flow at high speed and torque. The second generation heat exchanger showed that the model could accurately predict heat transfer, and the maximum experimental heat transfer rate was 15.3 kW for exhaust flow at 7.0 kg/min and 740 K.Item Superharmonic nonlinear lateral vibrations of a segmented driveline incorporating a tuned damper excited by non-constant velocity joints(2010-07-14) Browne, MichaelLinear vibration measurement and analysis techniques have appeared to be sufficient with most vibration problems. This is partially due to the lack of proper identification of physical nonlinear dynamic responses. Therefore, as an example, a vehicle driveshaft exhibits a nonlinear super harmonic jump due to nonconstant velocity, NCV, joint excitation. Previously documented measurements or analytical predictions of vehicle driveshaft systems do not indicate nonlinear jump as a typical vibration mode. The nonlinear jump was both measured on a driveshaft test rig and simulated with a correlated model reproduced the jump. Subsequent development of the applied moments and simplified equations of motion provided the basis for nonlinear analysis. The nonlinear analyses included bifurcation, Poincare, Lyapunov Exponent, and identification of multiple solutions. Previous analytical models of driveshafts incorporating NCV joints are typically simple lumped parameter models. Complexity of models produce significant processing costs to completing significant analysis, and therefore large DOF systems incorporating significant flexibility are not analyzed. Therefore, a generalized method for creating simplified equations of motion while retaining integrity of the base system was developed. This method includes modal coupling, modal modification, and modal truncation techniques applied with nonlinear constraint conditions. Correlation of resonances and simulation results to operating results were accomplished. Previous NCV joint analyses address only the torsional degree of freedom. Limited background on lateral excitations and vibrations exist, and primarily focus on friction in the NCV joint or significant applied load. Therefore, the secondary moment was developed from the NCV joint excitation for application to the driveshaft system. This derivation provides detailed understanding of the vibration harmonic excitations due to NCV joints operating at misalignment angles. The model provides a basis for completing nonlinear analysis studying the system in more detail. Bifurcation analysis identified ranges of misalignment angles and speeds that produced nonlinear responses. Lyapunov Exponent analysis identified that these ranges were chaotic in nature. In addition, these analyses isolated the nonlinear response to the addition of the ITD nonlinear stiffness. In summary, the system and analysis show how an ITD installed to attenuate unwanted vibrations can cause other objectionable nonlinear response characteristics.Item X-by-wireless: a novel approach to vehicle control(2009-05-15) Hoelscher, David LouisAs the cost of wireless devices approaches zero, it becomes more feasible to replace wires with wireless communication. Vehicle wiring harnesses are traditionally wired to communicate both power and information simultaneously, resulting in separate circuits for each vehicle device. X-By-Wireless seeks to supplant this configuration in favor of a shared power bus and wireless inter-component communication. In doing so, we can recognize a number of benefits such as reduced weight and increased reliability, flexibility, and upgradeability. However, this introduces new problems such as longer transmission delays, interference and encryption issues, fusing difficulties, and public perception regarding safety. The purpose of this thesis is to define the X-By-Wireless concept and to investigate the benefits and drawbacks in implementing X-By-Wireless. Furthermore, we do a theoretical and case study analysis to expand upon the weight reduction benefit so as to quantify the expected improvements. We also address each of the challenges presented by X-By-Wireless and integrate them into a proposed circuit that is capable of performing all the necessary functions of wireless control, wireless sensing, and fusing. We find that the proposed device can be mass-produced as an effective solution that meets the speed and security constraints necessary for most vehicle components.