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.

No description available.

Many mechanisms have been suggested for brake squeal over many years. In order to identify the most appropriate of these mechanisms, an experimental investigation has been carried out to define in detail the vibration characteristics of a squealing heavy vehicle air operated drum brake on both a vehicle and a laboratory brake test rig. This required the development of a novel 'scanning' technique for the modal analysis of the rotating drum, which showed the presence of well-defined complex wavelike modes. From these results, the dynamic behaviour of the drum, in particular, is found to be in good qualitative agreement with the predictions of a simple 'binary flutter' mechanism of squeal. Based on the role of rotor symmetry in this mechanism, a means of decoupling, flutter modes is developed involving a reduction in the rotational symmetry of the drum by means of attaching masses in a defined pattern at its periphery. It is shown theoretically that such decoupling would be expected to increase the dynamic stability of the brake, and experimental application of the technique confirms its effectiveness in reducing or eliminating squeal. Practical design aspects of reducing the rotational symmetry of the drum are considered, using finite element modelling, and it is also shown that the technique can be effective in other types of vehicle brake, such as disc brakes and hydraulic drum brakes. The simple lumped parameter models used in the above work are inadequate as brake design tools, however, and so a novel application of finite element modelling is used to extend the principle of the binary flutter mechanism to a more detailed model of a complete brake. This is shown to be capable of predicting known features of squeal and may be used as a brake design tool for both the brake structure and the friction material.

Thesis (M.S.)--University of Wisconsin--Madison, 1969. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Orientador: Auteliano Antunes dos Santos Junior / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia mecanica / Made available in DSpace on 2018-08-04T10:30:47Z (GMT). No. of bitstreams: 1 Santos_AliandroHenriqueCosta_M.pdf: 10616712 bytes, checksum: 57733fcc9ba5b442556901d87af2a403 (MD5) Previous issue date: 2005 / Resumo: Os freios utilizados para veículos são normalmente por atrito. A tendência internacional é no sentido de utilizar somente freios por atrito à disco, eliminando os atuais tambores empregados em rodas traseiras para automóveis de passageiros. O aumento do desempenho de veículos automotivos e a conseqüente alteração em suas características dinâmicas tem levado a criação de sistemas de freio mais eficientes. A expansão do mercado para pastilhas e a necessidade de redução de custos tem levado ao surgimento de materiais sem a qualidade necessária para o desempenho da frenagem. Os procedimentos de ensaio existentes hoje e que permitem avaliar a qualidade do material de atrito são complexos e normalmente fazem uso de dinamômetros com inércia, de custo muito elevado e não disponíveis nos centros e instituições de pesquisa brasileiras. Este trabalho teve como objetivo caracterizar o desempenho de materiais de atrito para pastilhas de freio através da criação de um procedimento de ensaio que englobe as principais variáveis que influenciam o processo de frenagem. Foi utilizado o Dispositivo de Ensaio de Amostras, dinamômetro de baixo custo disponível no Departamento de Projeto Mecânico da FEM-Unicamp. Um planejamento experimental ortogonal L9 permitiu o estudo da influência de variáveis envolvidas no processo de utilização de pastilhas, que são a marca, o fornecedor, a pressão específica, a velocidade e a temperatura, em dois níveis de desgaste. Os resultados mostram que o procedimento proposto pode ser utilizado na avaliação da qualidade do material de atrito de pastilhas, de forma rápida, eficiente e com baixo custo / Abstract: Automotive brake systems are mainly friction based. The world tendency is toward using disc brakes instead of drum brakes, which are usually installed in the rear wheels. The increase in the performance of automotive vehicles and the changes in the dynamic characteristics have conducted to more efficient brake systems. The expansion of the brake pads market has impacted the quality of the products. Low quality products have been found, specially were no control exists. The actual test procedures to evaluate the quality of rnction materials are compIex and most of them require a fuII scale inertial dynamometer. Those machines are very expensive and most of the Brazilian research and quality centers do not have them. This work aimed to deveIop a procedure to characterize the performance of brake pads and analyzing the main factors of influence. A Iow cost non-inertial dynamometer, called D.E.A. - Fixture to text sampIes of friction material, was used. It is instalIed in the Department of Mechanical Design - FEM of the State University of Campinas, in Brazil. An experimental orthogonal design L9 was used to take the factor of influences in account. They are identified and the main factors are: contact pressure, disc speed, temperature and pad manufacturer. The influences were evaluated in two leveI of pad wearing. The results show that the procedure can be used to evaluate the quality of the rnction material for brake pads, in a fast and not expensive way / Mestrado / Projeto Mecanico / Mestre em Engenharia Mecânica

During some operations the brake system on a truck is exposed to severe stress and hightemperatures. To ensure function and safety during these operations, Scania test thebrake system both test rigs and in actual trucks around the world. There are tests thatare regulated by law that the truck manufacture must pass to be allowed to sell its vehicleand there are Scania internal tests to validate performance and quality. One of thoseinternal Scania tests is a severe test with extreme temperatures, called the Rossfeld-test,performed at the Rossfeld slope in the German Alps. The idea is that the truck rolls downthe slope only accelerated by the downhill force where the wheel brakes will be appliedwhen the vehicle speed passes 35 km/h and released when going slower than 25 km/h,this is repeated until the end of the slope. No auxiliary brakes are used. The objective of this thesis is to investigate the possibility of using a Scania truck as a testbench to perform a simulation of a truck rolling down a descent. And by this investigatethe possibility of recreating a wheel brake test as the Rossfeld-test on a horizontal roadby using the engine as the source of acceleration instead of the gravity. In this thesis a model was developed in Matlab/Simulink which through the CAN-busnetwork in the truck could request engine torque and brake pressure. Given the roadtopography of the actual German slope, the corresponding downhill force was calculatedand requested of the engine and brake pressure was applied when the truck passed 35km/h and released again when reaching 25 km/h. The model was verified against roll-tests performed in known slopes with three, eightand sixteen percent gradient. Results from simulations with the truck showed a biggerinconsistency with respect to acceleration and gear selection when requesting a low torqueas with the simulation of a 3% slope. This was not the case when requesting a highertorque as when simulating a 8% or 16% slope. The results showed that at a highertorque request the acceleration was more consistent but the truck was still acceleratingslower than the corresponding roll-test and an extra twelve percent of torque was addedto mimic the acceleration of the roll-test. The first 3000 m of the Rossfeld-slope wassimulated by driving in a circle and the temperature measurements catches the differencesin temperature build up as in the result from a real Rossfeld-test performed in the Germanalp. This shows there is a potential in this type of simulation.

Regenerative braking in conjunction with friction braking represents one of the most common braking strategies employed in electric and hybrid vehicles. As the friction brake accounts for about 5 to 85% of total braking in these “blended scenarios”, this warrants for more research into the development of new lightweight, wear resistant, and sustainable friction materials and also for reviewing the existing testing procedures.This research primarily focuses on generation of new knowledge related to development of environmentally friendly, lightweight friction material for vehicles with regenerative braking systems. A sample formulation was initially developed from knowledge gained by literature review and analysis of existing commercially available brake linings. Design of experiments based on Taguchi method and other statistical analysis tools were used to optimize the sample formulation. The density, porosity, shore D hardness, thermal stability, damping capacity of these pads were measured and compared with commercially available friction material. Pads were tested against commercially available rotors (ASTM A48 C30 gray cast iron) coated with ceramic material. Friction performance tests were completed using Universal Mechanical Tester (Tribolab by Bruker) and the scaled-down ISO SAE J2522 procedure. Friction surfaces of pads and rotors were analyzed in order to understand their surface chemistry and morphology, as well as their impact on performance of the tested friction material. The final optimized pad based on design of experiments (DOE 9) showed high and stable friction levels in high temperature sections (Section 9, Section 12.2 and Section 14 in ISO/SAE J2522 testing procedure) and excellent recovery capabilities at lower temperatures (Section 10, Section 13 and Section 15). This pad material was compatible with coated rotors, had low wear, and meets all the industry specifications and standards. SEM and EDX analysis showed that the pads developed stable friction layer on the friction surfaces and this capacity to develop friction material contributed towards overall friction stability of the material.

No description available.

Friction-induced oscillations occur in many engineering systems, often resulting in noise, vibration, and excessive or uneven wear. This research addresses the suppression of such oscillations, especially with application to braking systems, through the use of high-frequency dither signals. Brake squeal is an annoying and elusive problem too often present in braking systems of automobiles, trucks and aircraft. In previous work, the effectiveness of high-frequency dither to eliminate squeal in an automotive disc brake assembly was demonstrated experimentally. The main features of the dither-squeal cancellation system was the application of a high frequency variation in the brake pressure force accomplished by means of a piezoelectric stack placed behind one of the brake pads. This thesis contains a theoretical and numerical treatment of the application of dither to frictional systems. Two types of systems are investigated. The first is a classic, mass-on-a-moving belt problem, which experiences friction-induced oscillations similar to those encountered in brake applications. The system is first studied using an analytical technique based on the method of averaging. It is shown that, depending on the system, friction, dither-waveform, and belt-speed parameters, dither can stabilize an unstable system. However, in some cases, dither can destabilize an initially stable system. These results are verified numerically using time integration. The second type of system analyzed in this thesis is an annular plate with a rotating frictional device. The method of multiple scales is used to predict subcritical regions of instability; the results are validated using Floquet theory. The thesis treats both tangential and normal dither, the latter being closer to the brake application. It is found that normal dither, in addition to being harder to analyze, is much less effective than tangential dither.

Embreagens de prensas mecânicas, principalmente as de forja a quente se caracterizam por um intenso regime de trabalho com espaços muito curtos entre acionamentos. Muitas das embreagens apresentam desgaste acentuado obrigando a paradas frequentes para manutenção. Neste trabalho são discutidos os princípios de funcionamento de prensas excêntricas e os parâmetros de projeto de embreagens e freios. Pontos importantes são: o balanço entre torque de operação, número de inserções por minuto e a dissipação de calor. É feita uma breve revisão da literatura sobre compósitos, lonas e seu comportamento. Discute-se a diferença das premissas de projeto de uma lona automotiva e a lona para uso industrial com alto número de aplicações por minuto. Apresenta-se um pressuposto quanto ao processo de transmissão de calor na embreagem e o que influência no desgaste da mesma, relacionando-o com a pressão de contato. Nas manutenções se verificam resíduos (debris) diferentes sugerindo regimes diferentes de desgaste. Há um resíduo preto que caracteriza um regime severo de desgaste. Pode-se associar esse resíduo ao fenômeno da degradação da base polimérica que compõe a lona. A degradação da base polimérica é causada pela alta temperatura de operação dessas embreagens. Em ensaios simples de pino e disco consegue-se reproduzir desgaste das lonas, que comprova o observado na prática e as condições que isso ocorre. Finalmente são apresentadas sugestões para o dimensionamento das embreagens e cuidados necessários no projeto de freios e embreagens. / Mechanical press clutches, especially clutches for hot forging presses have a hard working cycle with a little time between engagements. Many of those clutches present a severe lining wear, needing frequent maintenance stops. This work is discusse, the basics of eccentric presses and the clutch design parameters. Important points are: the balance between operation torque, engagements per minute and heat dissipation. This also presents a short literature review regarding composites and linings. It is discussed the design baselines differences between automotive linings and this specific case. It is presented a hypothesis about the heat transfer process in the clutch and how its related with wear, associating it with the contact pressure. In maintenance it is found different kinds of wear debris, suggesting more than one wear regime. The black debris indicates a severe wear regime. This debris can be associated to the lining polymeric matrix degradation. The polymeric matrix degradation is caused by the high op eration temperatures in these clutches. Based on simple pin-on-disc tests can be obtained results that show what is practical observed and the conditions this occurs, proving the hypothesis. Finally are presented suggestions for clutch dimensioning and necessary project cares.