No description available.

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.

No description available.

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.

Neste trabalho foi realizada a seleção da espessura do disco a ser utilizada em um dinamômetro em escala reduzida, chamado Dinamômetro em Escala da Fras-le, a partir de quatro espessuras de disco ensaiadas conforme o procedimento de ensaio chamado de caracterização térmica. A seleção da espessura do disco foi realizada através da comparação dos resultados dos comportamentos térmicos dos discos de diferentes espessuras, ensaiados conforme o ensaio de caracterização térmica, com os resultados de quatro sistemas de freio, ensaiados em dinamômetros convencionais com o mesmo procedimento de ensaio. Os coeficientes de atrito médio por frenagem obtidos no ensaio de caracterização térmica do dinamômetro em escala reduzida e dos quatro sistemas de freio também foram comparados de modo a comprovar que a espessura de disco escolhida foi realmente adequada para este procedimento de ensaio. Esta comparação foi realizada através de três métodos: coeficiente de correlação de Pearson, comparação qualitativa e comparação quantitativa. Após a comparação foi comprovado que o Dinamômetro em Escala da Fras-le reproduz o comportamento do coeficiente de atrito médio por frenagem dos quatros sistemas com o ensaio de caracterização térmica para um material de fricção orgânico. / In this work, a disc thickness for a reduced-scale dynamometer called Fras-le Scale Dynamometer was selected by testing four disc thicknesses with the thermal characterization test procedure. The disc thickness selection was done by comparison of the different thick-disc thermal behavior tested with the thermal characterization procedure, with the results of four brake systems tested with the same procedure in full-scale dynamometers. The mean friction coefficients by braking obtained in the thermal characterization test of the reduced-scale dynamometer and of the four brake systems were also compared to prove that the selected disc-thick is adequate for this test procedure. This comparison was done by three methods: Pearson correlation coefficient, qualitative comparison and quantitative comparison. After this comparison it was verified that the Fras-le Scale Dynamometer can reproduce the behavior of the mean friction coefficient by braking of the four systems with the thermal characterization test for an organic friction material.

Neste trabalho foi realizada a seleção da espessura do disco a ser utilizada em um dinamômetro em escala reduzida, chamado Dinamômetro em Escala da Fras-le, a partir de quatro espessuras de disco ensaiadas conforme o procedimento de ensaio chamado de caracterização térmica. A seleção da espessura do disco foi realizada através da comparação dos resultados dos comportamentos térmicos dos discos de diferentes espessuras, ensaiados conforme o ensaio de caracterização térmica, com os resultados de quatro sistemas de freio, ensaiados em dinamômetros convencionais com o mesmo procedimento de ensaio. Os coeficientes de atrito médio por frenagem obtidos no ensaio de caracterização térmica do dinamômetro em escala reduzida e dos quatro sistemas de freio também foram comparados de modo a comprovar que a espessura de disco escolhida foi realmente adequada para este procedimento de ensaio. Esta comparação foi realizada através de três métodos: coeficiente de correlação de Pearson, comparação qualitativa e comparação quantitativa. Após a comparação foi comprovado que o Dinamômetro em Escala da Fras-le reproduz o comportamento do coeficiente de atrito médio por frenagem dos quatros sistemas com o ensaio de caracterização térmica para um material de fricção orgânico. / In this work, a disc thickness for a reduced-scale dynamometer called Fras-le Scale Dynamometer was selected by testing four disc thicknesses with the thermal characterization test procedure. The disc thickness selection was done by comparison of the different thick-disc thermal behavior tested with the thermal characterization procedure, with the results of four brake systems tested with the same procedure in full-scale dynamometers. The mean friction coefficients by braking obtained in the thermal characterization test of the reduced-scale dynamometer and of the four brake systems were also compared to prove that the selected disc-thick is adequate for this test procedure. This comparison was done by three methods: Pearson correlation coefficient, qualitative comparison and quantitative comparison. After this comparison it was verified that the Fras-le Scale Dynamometer can reproduce the behavior of the mean friction coefficient by braking of the four systems with the thermal characterization test for an organic friction material.

Neste trabalho foi realizada a seleção da espessura do disco a ser utilizada em um dinamômetro em escala reduzida, chamado Dinamômetro em Escala da Fras-le, a partir de quatro espessuras de disco ensaiadas conforme o procedimento de ensaio chamado de caracterização térmica. A seleção da espessura do disco foi realizada através da comparação dos resultados dos comportamentos térmicos dos discos de diferentes espessuras, ensaiados conforme o ensaio de caracterização térmica, com os resultados de quatro sistemas de freio, ensaiados em dinamômetros convencionais com o mesmo procedimento de ensaio. Os coeficientes de atrito médio por frenagem obtidos no ensaio de caracterização térmica do dinamômetro em escala reduzida e dos quatro sistemas de freio também foram comparados de modo a comprovar que a espessura de disco escolhida foi realmente adequada para este procedimento de ensaio. Esta comparação foi realizada através de três métodos: coeficiente de correlação de Pearson, comparação qualitativa e comparação quantitativa. Após a comparação foi comprovado que o Dinamômetro em Escala da Fras-le reproduz o comportamento do coeficiente de atrito médio por frenagem dos quatros sistemas com o ensaio de caracterização térmica para um material de fricção orgânico. / In this work, a disc thickness for a reduced-scale dynamometer called Fras-le Scale Dynamometer was selected by testing four disc thicknesses with the thermal characterization test procedure. The disc thickness selection was done by comparison of the different thick-disc thermal behavior tested with the thermal characterization procedure, with the results of four brake systems tested with the same procedure in full-scale dynamometers. The mean friction coefficients by braking obtained in the thermal characterization test of the reduced-scale dynamometer and of the four brake systems were also compared to prove that the selected disc-thick is adequate for this test procedure. This comparison was done by three methods: Pearson correlation coefficient, qualitative comparison and quantitative comparison. After this comparison it was verified that the Fras-le Scale Dynamometer can reproduce the behavior of the mean friction coefficient by braking of the four systems with the thermal characterization test for an organic friction material.

M.Ing. / Adaptive traction control can greatly enhance the mobility of vehicles on varying road surfaces. Traction control includes Antilock Braking Systems (ABS) and Antislip Regulation Systems (ASR). During braking, wheel slip is controlled with ABS, while wheel slip during acceleration is controlled by an ASR. Since the friction between a vehicle's tyre and the road surface is a function of wheel slip, there is an optimum wheel slip value at which the best road holding performance can be achieved. This optimum wheel slip value will however change with differing road surfaces and vehicle speeds. Optimising the wheel slip values has several advantages: both vehicle stopping and acceleration distances can be optimised, vehicle handling during in-turn braking and acceleration are optimised and tyre wear is reduced. Currently there are various ABS and ASR systems available, with the common goal of optimising wheel slip. These systems are however mechanically complex, while the operation of both these systems is usually triggered when some wheel slip value is exceeded. Differing road surfaces can greatly influence the effectiveness of these systems. The central theme of this research is the development of a fuzzy logic control algorithm for vehicle traction control. The control algorithm is tested with an experimental setup. The operating conditions experienced by an ABS are closely simulated in order to study the feasibility of fuzzy logic for traction control. The results obtained indicates the viability of fuzzy logic for wheel slip control. Confirmation of these results, obtained with the experimental ABS, have to be validated during vehicle testing. The main goal is to improve the performances of existing traction control systems and the feasibility of fuzzy controllers in automobile applications.

Squeal noise has been an on-going concern with automotive brake systems since their inception. Even after many decades of research no single theory exists that adequately describes the phenomenon, and no general methods for eliminating squeal noise exist. Broadly speaking, three primary methods of analysis have been applied to understanding and eliminating brake squeal: analytical, experimental and numerical. Analytical models provide some insight into the mechanisms involved when a brake squeals, but have limitations in applicability to specific brake systems. Experimental methods provide the backbone of brake squeal investigations, especially in an industrial environment. However, the core focus of this thesis is to use a large scale finite element analysis (FEA) model to investigate brake squeal. Initially the FEA model was developed and the dynamic characteristics were validated against experimental modal analysis results. A complex eigenvalue analysis was performed to identify potential squeal modes which appear as unstable system vibration modes. Further techniques are described that allow the deeper probing of unstable brake system modes. Feed-in energy, which is the conversion of friction work into vibrational energy during the onset of squeal, is used to determine the relative contribution of each brake pad to the overall system vibration. The distribution of the feed-in energy across the face of a brake pad is also calculated. Component strain energy distributions are determined for a brake system as a guide to identifying which components might best be modified in addressing an unstable system mode. Finally modal participation is assessed by calculating the Modal Assurance Criterion (MAC) between component free modes and the component in the assembly during squeal. This allows participating modes to be visualised and aids in the development of countermeasures. The majority of the work in this thesis was performed using the commercial FEA code MSC.Nastran with user defined friction interfaces. An alternative approach using a contact element formulation available in Abaqus was also implemented and compared to the MSC.Nastran results. This analysis showed that considerable differences were noted in the results even though the overall predicted stability correlated relatively well to observed squeal. Abaqus was also used in a case study into the design of a brake rotor in a noisy brake system. The results of this study provided good correlation to observed squeal and facilitated effective rotor countermeasures to be developed. Some success was achieved in the main aims of predicting brake squeal and developing countermeasures. However, while the tools presented do allow a deeper probing of system behaviour during squeal, their use requires good correlation to observed squeal on brake system to be established. As such, their use as up-front design tools is still limited. This shortcoming stems from the complexity of brake squeal itself and the limitations in modelling the true nature of the non-linearities within a brake system.

No description available.