Search

This thesis considers the application of neural networks to automotive suspension systems. In particular their ability to learn non-linear feedback control relationships. The speed of processing, once trained, means that neural networks open up new opportunities and allow increased complexity in the control strategies employed. The suitability of neural networks for this task is demonstrated here using multilayer perceptron, (MLP) feed forward neural networks applied to a quarter vehicle simulation model. Initially neural networks are trained from a training data set created using a non-linear optimal control strategy, the complexity of which prohibits its direct use. They are shown to be successful in learning the relationship between the current system states and the optimal control.

This thesis presents laboratory and field studies into the effects of solar radiation on the thermal comfort of vehicle occupants. Whilst, thermal comfort has been widely studied in built environments, there have been relatively few studies into thermal comfort in vehicles. Those studies that have been conducted have noted that the effect of solar radiation is considerable in these confined microclimates. The aim of this thesis was to provide baseline data for the effects of solar radiation on thermal sensation and determine how this information can be integrated to provide a method for the assessment of vehicle thermal comfort. This was achieved using a specially constructed whole body solar chamber in a series of four laboratory studies looking at different aspects of solar radiation on human thermal comfort and an extensive field trial conducted in Seville, Spain. The laboratory studies were as follows:- 1, The effect of the intensity of direct simulated solar radiation on human thermal responses. Eight male subjects were exposed to 4 different intensity solar radiation conditions. Physiological and psychological measurements were taken. It was established that a mean response to 200 Wm"2 of direct simulated solar radiation will give a thermal sensation shift of one positive scale point. 2, The effect of the spectral content of simulated solar radiation on human thermal responses. Eight male subjects were exposed to 4 different spectral radiation conditions, with the same total radiation intensity, 400 wm·2 • There was found to be no significant difference in the thermal sensation responses due to spectra. 3, The effects of glazing type on human thermal comfort responses. Eight male subjects were exposed to 4 different automotive glazings, with a fixed external solar radiation level of 1000 wm·2 • The spectral qualities of glazing can significantly effect human thermal comfort. The lower the transmission of visible radiation through the glazing, the lower the thermal sensation felt by subject in a neutral environment. 4, The effect of direct short wavelength and long wavelength radiation on human thermal comfort. Nine male subjects were exposed to short wavelength, long wavelength and combined short and long wavelength radiation. For the conditions investigated it was established that the addition of reradiation from internal components has an effect on thermal sensation when combined with direct solar radiation. However, it is not considered that it will be a major factor in a real world situation, as dashboards generally do not maintain high surface temperatures in vehicles without high air temperatures. Using the data collected in the laboratory studies a predictive model, PMV sotu, was developed which integrated directed solar radiation into an existing thermal comfort model (PMV) in the form of a factor, Rsolar· Rsolar is a correction factor for the addition of short wavelength radiation which converts actual measured solar radiation to a thermal sensation scale adjustment The PMV solar model was validated with other models in field trials conducted in Seville, Spain. Four male subjects, undertook a series of 32, one hour long experiments over 8 days, whilst travelling on a Spanish highway. Environmental, physiological and psychological measurements were taken throughout the experiments to provide data for validation of THE PMV solar model. The assessment of human thermal comfort in vehicles is complex. Variation in environmental parameters in terms of both spatial and temporal changes, make accurate prediction of thermal comfort difficult. However, the PMV solar model provides an improved level of prediction of the state of thermal comfort of the vehicle occupants, in environments which have a high solar radiation level over existing thermal indices.

Exhaust Gas Recirculation (EGR) is one of several technologies that are being investigated to deliver future legislative emissions targets for diesel engines. Its application requires a detailed understanding of the thermofluidic processes within the engine's charge air system. A fully validated Computational Fluid Dynamics (CFD) process is one way of providing this understanding. This thesis describes how a process was developed using validation data from a four-branch diesel engine inlet manifold with a secondary EGR inlet. The validation and verification technique adopted, divided the complex flow problem into simpler elemental flow problems. Knowledge on these simple problems was, in some cases, found to be well documented in published literature. In other cases, additional detailed experimental validation and verification studies were carried out to supplement published information. Knowledge from these simple problems was utilised to develop the main CFD process and to enhance understanding of the calculation uncertainties.

This thesis discusses a general approach to hybrid powertrain control based on optimisation and optimal control techniques. A typical strategy comprises a high level non-linear control for optimised energy efficiency, and a lower level Linear Quadratic Regulator (LQR) to track the high-level demand signals and minimise the first torsional vibration mode. The approach is demonstrated in simulation using a model of the Toyota Prius hybrid vehicle, and comparisons are made with a simpler control system which uses proportional integral (PI) control at the lower level. The powertrain of the Toyota Prius has a parallel configuration, comprising a motor, engine and generator connected via an epicyclic gear train. High level control is determined by a Power Efficient Controller (PE C) which dynamically varies the operating demands for the motor, engine and generator. The PEC is an integrated nonlinear controller based on an iterative downhill search strategy for optimising energy efficiency and battery state of charge criteria, and fully accounts for the non-linear nature of the various efficiency maps. The PEC demand signals are passed onto the LQR controller where a cost function balances the importance of deviations from these demands against an additional criterion relating to the amplitude of driveline vibrations. System non-linearity is again accounted for at the lower level through gain scheduling of the LQR controller. Controller performance is assessed. in simulation, the results being compared with a reference system that uses simple PI action to deliver low-level control. Consideration is also given to assessing performance against that of a more general, fully non-linear dynamic optimal controller.

Six sets of subscale carbon–carbon composite rotors and stators for aircraft brakes were manufactured to provide friction and wear test samples at six different densities. The friction and wear tests used energies to represent the service energy of the Boeing 767 aircraft. A functional relationship between fiction coefficient and porosity/density was made. This relationship was used to minimise manufacturing cost by providing the minimum densification of the carbon–carbon composite brake discs needed to meet design friction coefficient.