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.

The chemical nature of the Transfer Film (T.F.) or Third-Body Layer (T.B.L.) formed at the friction interface of an automotive friction brake during off-brake motoring has been studied using Energy Dispersive X-ray (E.D.X.) analysis and Scanning Electron Microscopy (S.E.M.). Although these third-body layers are deposited on both mating surfaces of the friction couple, special attention has been paid to those formed on the disc brake rotor surface. Concurrently, detailed investigations have been undertaken examining the temperature-dependent, physico-chemical interactions of friction material constituents with each other, atmospheric oxygen and countermember materials using X-Ray Diffraction (X.R.D.).Evidence is presented relating the tribological performance of the friction pair to both the transfer film thermochemistry and the friction material composition. Among those characteristics describing the tribological performance of the friction couple, particular attention has been applied to the generation of Disc Thickness Variations (D.T.V.) induced by Off-Brake or Non-Braking Wear (O.B.W. or N.B.W.). The critical role of solid lubricants and abrasive friction modifiers and their effectiveness over a range of contact pressures / temperatures has received particular attention. Information obtained using various surface analytical techniques combined with detailed dimensional assessments of the affected triboelements has been used to show the considerable significance of abrasive particle size in determining the overall tribological behaviour of the friction pair, especially with respect to the wear regime and extent encountered at the surface of the countermember during O.B.W.Wear mechanisms are described for the generation of off-brake wear, these varying with friction material formulation. Dynamic and temperature-dependent influences on the level of in-service disc brake rotor runout are named as causes for particular forms of disc thickness variation generated by aggressive friction materials. Keywords: Third-body layer; Transfer film; Tribochemistry; Automotive Friction Braking; Cold Judder; Disc Thickness Variation; Disc Brake; Friction Material.

This research is concerned with exploring the relationship between car driving and musculoskeletal troubles and following on from this investigating methods which could aid the automotive industry in the design and evaluation of car seats. The thesis is divided into two parts. Part I describes the development and results of an epidemiological survey undertaken with data obtained from two sample groups. Study 1 was an interview survey (based on the Nordic Questionnaire) of 600 members of the British public, randomly selected within the strata of age and gender. Study 2 used the same interview, but with two carefully chosen groups of police officers (n=200). The results indicated that car drivers (especially those who drove as part of their job) appeared to be at risk in terms of reported discomfort and sickness absence due to low back trouble. Evidence from this and other studies has also indicated that drivers with the most adjustable driving packages may benefit in terms of both reduced discomfort and reduced sickness absence. This provided the background for the subsequent research in Part II and some impetus for car manufacturers to consider health issues in the design of car workstations. Part II involved a series of three experiments designed to investigate methodologies which could be used by manufacturers to predict car seat discomfort The literature was reviewed to identify suitable predictive techniques which would be robust enough to provide information to the automotive industry in 'real world' situations. The technique of interface pressure measurement had already generated interest in some seat manufacturers and was therefore selected for investigation. As a result of the findings in experiment 1, established guidelines for a comfortable driving posture may need to be modified. The other two experiments were designed to create discomfort in subjects firstly by varying foam hardness and secondly by varying posture. A clear, simple and consistent relationship between interface pressure and discomfort in realistic driving situations was not identified. Future studies using this technique should provide information regarding such factors as gender, the body mass index, anthropometric data, posture and foam hardness due to the confounding nature of these variables.

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No description available.

This thesis begins with a brief overview of vehicle control. The thesis places powertrain control, which is discussed in more detail, within the wider context of vehicle control. Traction control is one aspect of powertrain control. The available methods of traction control are reviewed together with a discussion on the systems in current production. The traditional method adopted by the automotive industry for traction control is analysed. The powertrain system is analysed from a control stand-point and a control oriented approach to traction control design identified. The emphasis in this thesis is on the analysis of traction control systems. The analysis is performed on simulation models and is supported by implementations on the real vehicle. The level of modelling appropriate for the analysis is justified and models developed in a modular manner. The individual modules are developed on the basis of published material and previous work within Ford Motor Company. Based on the analysis, two traction control strategies are developed which are subsequently developed and implemented on real vehicles. The results of this vehicle work is discussed.

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This thesis is concerned with the use of semi-active suspensions in heavy vehicles to improve ride and reduce road damage. An introduction into the subject is given in chapter 1 and a review of the relevant literature is presented at the beginning of each main chapter. The development and modelling of a prototype, continuously variable semi-active damper for heavy vehicles is described in chapter 2. A proportional valve is used to generate the variable damping coefficient and the detrimental effects of the oil flow forces acting on the valve spool are studied. The force tracking performance of the damper is then examined for simple input conditions and the compliance of the hydraulic fluid is found to have a strong influence upon the response of the damper. The different vehicle and road models used in the thesis are described in chapter 3. In chapter 4, the performance of the prototype damper is investigated under realistic operating condition using a Hardware-in-the-Loop (HiL) test rig, with a single wheel station vehicle model. The prototype damper displays a phase lag of approximately 20ms between the demanded and achieved damping force. The semi-active suspension is found to be most effective in reducing the body accelerations relative to an optimum non-linear passive suspension. A theoretical investigation into the reduction of road damage through the use of active and semi-active suspensions is described in chapter 5. The relative performance of four linear state feedback control strategies is examined. The potential for reducing road damage by using a controller which directly regulates various measures of road damage is also studied. Significant improvements are predicted for the three controllers which assume the road inputs to the vehicle are correlated. However, these benefits are shown to diminish as the vehicle speed is reduced. It is concluded that the control of the dynamic tyre forces is an effective means by which to regulate road damage. Theoretical predictions of the benefits from wheelbase preview control are measured experimentally in chapter 6, using the prototype semi-active damper in a half-car HiL rig with a planar two axled heavy vehicle model. The benefits of preview control using the prototype semi-active damper are found to be less than theoretically possible due to the phase lag between the demanded and achieved damping force of the prototype damper. The final section of chapter 6 shows that the performance of the prototype damper can be improved further by having a theoretical simulation running ahead of the HiL vehicle. The theoretical simulation is used to predict the demanded damper force for the HiL vehicle and thereby compensate for the phase lag in the prototype damper. Conclusions and recommendations for further work are presented in chapter 7.

The research in this thesis is focused around the control of rapid automotive product specification changes which are due to multiple and unexpected factors ie. legal requirements, technological improvements, climate conditions. Automotive companies use the Product Specification Concept which consists of a multidisciplinary theory using Boolean logic as the applications environment and a team of auditors - people who check the validity of such a theory - to control the complexity of the changes in its products. Although the specifications data are stored electronically in data bases, the core of such business is dependent on the knowledge and experience of people within the automotive companies and still generally operates manually. Thus, human characteristics have an affect upon the business (ie. the inability of people to work with codes and many different data at once, people tend to forget or they lack proper training and skills, etc.) which makes it less efficient and consequently more costly. In this thesis possible ways of computerising such an environment (specifically, Rover's Auditing function and Product Specification Concept) are investigated. The characteristics of the problem domain indicate the need to use knowledge based reasoning and Object Oriented Programming. A system, ROOVESP (Rover's Object Oriented VEhicle Specification) was developed as the "vehicle" to explore the area and it proved that knowledge and experience can be automatically acquired from the existing data and procedures. When these are coded into rules, computer intelligence can contribute to this traditionally human oriented environment and automate fully both the Auditing area and the Product Specification Concept in Rover. The techniques adopted were proved applicable to other similar areas.

No description available.