The work is divided into two parts – theoretical and practical. The first, theoretical part is focused on introduction with the problematics, describing the concept of translation motion and brake physics, defining terms adhesion and friction, skid, driving resistances, calculation formulas etc. After the mechanics chapter follows the chapter about tire and its composition and properties, and a brake system chapter, describing Anti-lock brake system (ABS) and some other important brake-support systems. Second part of this thesis is focused on practical side, which contains acceleration measuring and skid marks creation, followed by evaluation of measured data in form of calculations and graphs.

The aim of my diploma thesis is the formula car pedal assembly design. The introduction of the thesis presents the possible design variants of the car pedal assembly of the current vehicles completed with requirement that are demanded from them. Furthermore, there are mentioned and described individual elements of the car pedal assembly including their principle and function. The thesis mentions collected basic information about the design of the components. On the basis of this mentioned information the thesis aims for the design including the choice of appropriate and relevant components. The final design of pedals and the basic console results from the mentioned calculation of stress analysis. In conclusion of the thesis there are evaluated achieved results that are compared with the current pedal assembly and there are presented the possible ways of designs with the respect to their production.

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No description available.

The air hybrid engine absorbs the vehicle kinetic energy during braking, stores it in an air tank in the form of compressed air, and reuses it to start the engine and to propel a vehicle during cruising and acceleration. Capturing, storing and reusing this braking energy to achieve stop-start operation and to give additional power can therefore improve fuel economy, particularly in cities and urban areas where the traffic conditions involve many stops and starts. In order to reuse the residual kinetic energy, the vehicle operation consists of 3 basic modes, i.e. Compression Mode (CM), Expander Mode (EM) and normal firing mode, as well as stop-start operation through an air starter. A four-cylinder 2 litre diesel engine has been modelled to operate in four air hybrid engine configurations so that the braking and motoring performance of each configuration could be studied. These air hybrid systems can be constructed with production technologies and incur minimum changes to the existing engine design. The regenerative engine braking and starting capability is realised through the employment of an innovative simple one-way intake system and a production cam profile switching (CPS) mechanism. The hybrid systems will allow the engine to be cranked by the compressed air at moderate pressure without using addition starters or dedicated valves in the cylinder head. Therefore, the proposed air hybrid engine systems can be considered as a cost-effective regenerative hybrid powertrain and can be implemented in vehicles using existing production technologies. A novel cost-effective pneumatic regenerative stop-start hybrid system, Regenerative Engine Braking Device (RegenEBD), for buses and commercial vehicles is presented. RegenEBD is capable of converting kinetic energy into pneumatic energy in the compressed air saved in an air tank using a production engine braking device and other production type automotive components and a proprietary intake system design. The compressed air is then used to drive an air starter to achieve regenerative stop-start operations. The proposed hybrid system can work with the existing vehicle transmission system and can be implemented with the retro-fitted valve actuation device and a sandwich block mounted between the cylinder head and the production intake manifold. Compression mode operation is achieved by keeping the intake valves from fully closed throughout the four-strokes through a production type variable valve exhaust brake (VVEB) device on the intake valves. As a result, the induced air could be compressed through the opening gap of intake valves into the air tank through the intake system of proprietary design. The compressed air can then be used to crank the engine directly through the air expander operation or indirectly through the action of an air starter in production. A single cylinder camless engine has been set up and operated to evaluate the compression mode performance of two air hybrid concepts. The experimental results are then compared with the computational output with excellent agreement. In order to evaluate the potential of the air hybrid engine technologies, a new vehicle driving cycle simulation program has been developed using Matlab Simulink. An air hybrid engine sub-model and methodology for modelling the air hybrid engine’s performance have been proposed and implemented in the vehicle driving cycle simulation. The NEDC analysis of a Ford Mondeo vehicle shows that the vehicle can achieve regenerative stop-start operations throughout the driving cycle when it is powered by a 2.0litre diesel engine with air hybrid operation using a 40litre air tank of less than 10bar pressure. The regenerative stop-start operation can lead to 4.5% fuel saving during the NEDC. Finally, the Millbrook London Transport Bus (MLTB) driving cycle has been used to analyse the effectiveness of RegenEBD on a double deck bus powered by a Yuchai diesel engine. The results show that 90% stop-starts during the MLTB can be accomplished by RegenEBD and that a significant fuel saving of 6.5% can be obtained from the regenerative stop-start operations.

Friction force oscillations caused by changing properties of the contact zone between brake disc and pad are well known from various applications. Resulting effects like brake judder are known phenomena in brake technologies and in the scope of various scientific work. A new measure to potentially reduce brake torque oscillations is the active compensation with the use of the control system of a self-energizing hydraulic brake (SEHB). New in comparison to traditional disc brakes is the fact that the brake torque is measured by the pressure in an additional supporting cylinder. Thus, the brake system is able to work in brake torque control mode. Within this paper a dynamic simulation model of the SEHB is shown and evaluated with measurement data achieved from a full scale test rig for railway applications. Based on the simulation model a pressure control strategy is developed to minimize brake torque oscillations of lower frequencies. The control parameters of the simulation are transferred to the experimental setup. Finally, simulation and experimental results are compared. Future work will deal with the development of control strategies to additionally minimize brake torque oscillations of the higher dynamics.

In this thesis we investigate the existence and stability of periodic solutions of Hamiltonian systems with a discrete symmetry. The global existence of periodic motions can be proven using the classical techniques of the calculus of variations; our particular interest is in how the stability type of the solutions thus obtained can be determined analytically using solely the variational problem and the symmetries of the system -- we make no use of numerical or perturbation techniques. Instead, we use a method introduced in [41] in the context of a special case of the three-body problem. Using techniques from symplectic geometry, and specifically the Maslov index for curves of Lagrangian subspaces along the minimizing trajectories, we verify conditions which preclude the existence of eigenvalues of the monodromy matrix on the unit circle. We study the applicability of this method in two specific cases. Firstly, we consider another special case from celestial mechanics: the hip-hop solutions of the 2N-body problem. This is a family of Z_2-symmetric, periodic orbits which arise as collision-free minimizers of the Lagrangian action on a space of symmetric loops [14, 53]. Following a symplectic reduction, it is shown that the hip-hop solutions are brake orbits which are generically hyperbolic on the reduced energy-momentum surface. Secondly we consider a class of natural Hamiltonian systems of two degrees of freedom with a homogeneous potential function. The associated action functional is unbounded above and below on the function space of symmetric curves, but saddle points can be located by minimization subject to a certain natural constraint of a type first considered by Nehari [37, 38]. Using the direct method of the calculus of variations, we prove the existence of symmetric solutions of both prescribed period and prescribed energy. In the latter case, we employ a variational principle of van Groesen [55] based upon a modification of the Jacobi functional, which has not been widely used in the literature. We then demonstrate that the (constrained) minimizers are again hyperbolic brake orbits; this is the first time the method has been applied to solutions which are not globally minimizing. / Thesis (Ph.D, Mathematics & Statistics) -- Queen's University, 2013-09-25 10:47:53.257

The control of the flagellar motor in Rhodobacter sphaeroides was investigated. Unlike most flagellar motors which are controlled by reversing the direction of rotation, the R. sphaeroides motor is controlled via a stop-start mechanism. Advanced optical microscopy was employed alongside genetic, biochemical, and behavioural techniques. High-resolution measurements of rotating beads on flagellar stubs revealed that the R. sphaeroides motor is similar to its E. coli counterpart, rotating counterclockwise at comparable torques/speeds (1,300 pNnm/rad at stall torque), and exhibiting transient step changes in speed. The mean stop duration, mean stop frequency (number of stops per s), and run bias (fraction of time spent rotating) of wild-type at steady-state were 0.66 ± 1.01 s, 0.31 ± 0.19 s-1, and 0.80 ± 0.20, respectively. Manipulating signal inputs to the motor genetically, or by exposing cells to chemotactic stimuli revealed that (i) without chemotactic stimulation the motor rotates continuously, (ii) phosphorylated CheYs are required to stop the motor, and (iii) the chemotaxis system cannot control the speed of rotation of the motor (termed chemokinesis) as previously reported. Complementation studies revealed that CheY3, CheY4, and CheY5 are functionally equivalent. The copy numbers per cell of important CheYs were found to vary greatly under the conditions tested (<1,000, ~3,000, ~60,000 for CheY3, CheY4, and CheY6 respectively). To determine how CheY-P binding causes the motor to stop, external force (viscous flow or optical tweezers) was applied to chemotactically stopped motors. CheY-P binding might either cause the torque-generating units to disengage from the rotor, analogous to a clutch, or trigger the rotor to jam, analogous to a brake. The rotor resisted re-orientation during a chemotactic stop implying that the motor was held in a locked state. The value of torque resisting forward motion (keeping it locked) was estimated to be 2-3 x stall torque (2,500-4,000 pNnm/rad). Furthermore beads attached to flagellar stubs stop at fixed angles for several seconds, showing no large-scale Brownian motion. Step analysis revealed that these stop events occur at 27-28 discrete angles around the motor, which most likely reflect the periodicity of the rotor (i.e. copies of FliG). This represents the first experimental resolution of steps in the rotation of a wild-type bacterial flagellar motor with a full complement of torque-generating units.

The fundamental theories of heat generation and transfer at the friction interface of a brake assume either matching or not matching surface temperatures by having a varying or uniform heat partition ratio respectively. In the research presented the behaviour of heat partition has been investigated in a fundamental study based on experimental measurements of temperature and the associated modelling and simulation of heat transfer in a brake friction pair. For a disc brake, an important parameter that was identified from the literature study is the interface tribo-layer (ITL), which has been modelled as an equivalent thermal resistance value based on its thickness and thermal conductivity. The interface real contact area was also an important parameter in this investigation, and it has been found to affect heat partitioning by adding its own thermal resistance. A 2-dimensional (2D) coupled-temperature displacement Finite Element (FE) model is presented, based on which a novel relationship which characterises the total thermal resistance (or conductance) at the friction interface has been characterised based on the ITL thermal properties, the contact area, and the contact pressure at the interface. Using the model the effect of friction material wear on the total thermal resistance (or conductance) at the friction interface was predicted and a comparison of the Archard and Arrhenius wear laws in predicting the wear of a resin bonded composite friction material operating against a cast iron mating surface is presented. A 3-dimensional (3D) model is also presented. This model has represented a small scale disc brake test rig which has been used in parallel with the simulation for validation in a drag braking scenario. Two simulation conditions with different pad surface states were investigated, the first having a nominally flat surface, and the second an adjusted (worn) pad surface based on bedding-in data. The Arrhenius wear model was applied to significance of including wear on the total thermal resistance at the friction interface over a short brake application. A sensitivity analysis on the interface thermal conductance, the location of heat generation, and the magnitude of contact pressure has identified the importance of each factor in determining the total thermal resistance (or conductance) at the friction interface during any friction brake application. It is concluded that the heat partitioning is insensitive on the location of heat generation, and that the most sensitive parameter is the contact pressure.

L’objectif de cette thèse est de proposer de nouvelles solutions matériaux moins sensibles à la fissuration par fatigue thermique induite en frottement, première cause de remplacement des disques de frein de véhicule « poids lourd ». Les performances en freinage doivent être équivalentes à celles obtenues avec le couple de matériaux actuels : disque de frein en fonte à graphite lamellaire- garniture en matériau de friction composite à matrice semi-métallique. L’étude repose sur une approche multidisciplinaire des phénomènes et des couplages induits en freinage. Elle comporte quatre parties : la première partie expose les principaux enjeux industriels et scientifiques du freinage des véhicules « poids lourds » ; la seconde développe une approche modèle-expérience originale pour caractériser les sollicitations de freinage conduisant à la dégradation de disques de frein échelle 1 en fonte à graphite lamellaire ; enfin les nouvelles solutions matériaux considérées sont évaluées suivant une étude tribologique (troisième partie) et en cyclage thermique (quatrième partie), développée en laboratoire / This PhD thesis was carried out with the aim of developing new materials for truck brake discs, so as to increase disc lifespans. Premature failure is the major problem encountered in the operation. Braking performances of new materials should be equivalent to those obtained with the current material couple: lamellar grey cast iron brake disc and commercial semi-metallic brake lining material. To do this, the study is divided in four parts: Firstly, major industrial and scientific aspects in braking are identified in literature and with investigations on truck brake discs used on road. Next, a coupled numerical-experimental approach enable us to characterize thermomechanical loadings induced by braking and leading to damage mechanisms of the lamellar grey cast iron disc. Finally, two aspects of new materials solutions are investigated in laboratory: tribological behaviour and thermal cycling behaviour