No / In this paper, a similarity concept is proposed to improve student understanding on difficult and complicated engineering theory. The planned application of this approach is for the Transportation Studies module (CSE6004-A) at School of Engineering, University of Bradford, United Kingdom. In the module, noise induced by road transport and vehicles are taught in depth, where the proposed teaching method will be applied to aid student understanding on the numerical concept of the vibration effect and noise on vehicle braking system. As part of the module planning, the full numerical solution of brake judder/vibration effect, which includes shaking (forced vibration) and nibbling (torsional vibration) effects will be introduced to students where similarity concept will be adapted in its teaching. The successfully applied concept will also be able to utilize by other engineering teaching and modules.

Collision avoidance systems (CASs) are being developed and fielded to reduce the number and severity of rear-end crashes. Kinematic algorithms within CASs evaluate sensor input and apply assumptions describing human-response timing and deceleration to determine when an alert should be presented. This dissertation presents an analytic assessment of dynamic function and performance CASs and associated driver performance for preventing automotive rear-end crashes. A method for using naturalistic data in the evaluation of CAS algorithms is described and applied to three algorithms. Time-series parametric data collected during 13 rear-end crashes and 70 near-crashes are input into models of collision avoidance algorithms to determine when the alerts would have occurred. Algorithm performance is measured by estimating how much of the driving population would be able to respond in the time available between when an alert would occur and when braking was needed. A sensitivity analysis was performed to consider the effect of alternative inputs into the assessment method. The algorithms were found to warn in sufficient time to permit 50–70% of the population to avoid collision in similar scenarios. However, the accuracy of this estimate was limited because the tested algorithms were found to alert too frequently to be feasible. The response of the assessment method was most sensitive to differences in assumed response-time distributions and assumed driver braking levels. Low-speed crashes were not addressed by two of the algorithms. Analysis of the events revealed that the necessary avoidance deceleration based on kinematics was generally less than 2 s in duration. At the time of driver response, the time remaining to avoid collision using a 0.5g average deceleration ranged from â 1.1 s to 2.1 s. In 10 of 13 crashes, no driver response deceleration was present. Mean deceleration for the 70 near-crashes was 0.37g and maximum was 0.72g. A set of the events was developed to measure driver response time. The mean driver response time was 0.7 s to begin braking and 1.1 s to reach maximum deceleration. Implications for collision countermeasures are considered, response-time results are compared to previous distributions and future work is discussed. / Ph. D.

A presente dissertação visa analisar o desempenho na frenagem de um cavalo mecânico e semi-reboque que utiliza o sistema ABS (Antilock Braking System). Foi desenvolvido um modelo virtual de simulação utilizando a técnica dos sistemas multicorpos (Multibody System) do SimMechanics, um toolbox do Matlab/Simulink. No modelo virtual do veículo combinado foram considerados os parâmetros geométricos e mecânicos dos chassis, das suspensões, dos freios, contato pneu-pavimento e a válvula sensível à carga. São obtidas as forças normais dinâmicas no contato pneu pavimento quando o veículo está desacelerando de 20m/s até a parada completa, estas forças normais dinâmicas são entradas de uma sub-rotina em Simulink onde são calculadas as forças de frenagem, quando os freios tipo S carne são acionados. São realizadas simulações de frenagens em linha reta em pistas de média aderência (0,4) e alta aderência (0,8). As eficiências são obtidas quando o cavalo mecânico utiliza a configuração fixa de ABS tipo 6S/6M e o semi-reboque utiliza diversas configurações de ABS tipos: 2S/1M (e 4,6); 2S/2M (e 4,6); 4S/2M (e4); 4S/2M (e6); 4S/3M (e4); 4S/3M (e6); 4S/4M (e4) e 4S/4M (e6) e 6S/6M. O veículo é simulado também freando sem sistema ABS e a eficiência resultante comparada com as obtidas anteriormente. Os resultados são apresentados em figuras que mostram as forças normais dinâmicas ao pavimento, as aderências utilizadas pelos pneus e as eficiências atingidas pelas diversas configurações de ABS utilizadas no semi-reboque. Conclui-se de forma geral que configurações de ABS com mais sensores e válvulas moduladoras produzem uma eficiência maior e que a utilização de qualquer configuração de ABS como sistema complementar do sistema de freios de serviço, aumenta a eficiência de frenagem que é sempre superior ao do veículo sem sistema ABS. Esses resultados ajudam na preservação da dirigibilidade e estabilidade do veículo combinado, contribuindo assim na prevenção de acidentes de trânsito em situações de emergência. / This dissertation reports on the development of a simulation model for the analysis of the braking performance of tractor-semitrailer vehicles that use the ABS (Antilock Braking System). The model was developed using the virtual simulation technique of multibody systems with SimMechanics, a toolbox of Matlab/Simulink. In this simulation model the mechanical and geometrical parameters of the chassis, suspensions, brakes, adhesion coefficient, and load sensing valve were considered. When the vehicle is decelerating, the normal forces between the tire and road surface are obtained by the virtual model. These forces are the input of a subroutine in which the braking forces are calculated when the S Came brakes are triggered. Simulations of braking on straight line in road were made for average adhesion coefficient (0.4) and high adhesion coefficient (0.8). Efficiencies were obtained when the tractor used fixed ABS configuration of a 6S/6M type, and the semitrailer used the ABS type: 2S/lM (and 4.6); 2S/2M (and 4.6); 4S/2M (e4); 4S/2M (e6); 4S/3M (e4); 4S/3M (e6); 4S/4M (e4) and 4S/4M (e6) and 6S/6M. The results are presented in figures which show, the normal dynamic forces between tire and road, adhesions used by the tires and the efficiencies achieved by different ABS configurations installed in the semi-trailer. It is possible to conclude that in general ABS configurations with more sensors and modulating valves produce higher efficiency and the use of any configuration as a complementary system of the ABS brake system service increases the braking efficiency, which is always higher than that of a vehicle without ABS. The results help preserving the vehicle stability and maneuverability, preventing road accidents in emergency situations.

A presente dissertação visa analisar o desempenho na frenagem de um cavalo mecânico e semi-reboque que utiliza o sistema ABS (Antilock Braking System). Foi desenvolvido um modelo virtual de simulação utilizando a técnica dos sistemas multicorpos (Multibody System) do SimMechanics, um toolbox do Matlab/Simulink. No modelo virtual do veículo combinado foram considerados os parâmetros geométricos e mecânicos dos chassis, das suspensões, dos freios, contato pneu-pavimento e a válvula sensível à carga. São obtidas as forças normais dinâmicas no contato pneu pavimento quando o veículo está desacelerando de 20m/s até a parada completa, estas forças normais dinâmicas são entradas de uma sub-rotina em Simulink onde são calculadas as forças de frenagem, quando os freios tipo S carne são acionados. São realizadas simulações de frenagens em linha reta em pistas de média aderência (0,4) e alta aderência (0,8). As eficiências são obtidas quando o cavalo mecânico utiliza a configuração fixa de ABS tipo 6S/6M e o semi-reboque utiliza diversas configurações de ABS tipos: 2S/1M (e 4,6); 2S/2M (e 4,6); 4S/2M (e4); 4S/2M (e6); 4S/3M (e4); 4S/3M (e6); 4S/4M (e4) e 4S/4M (e6) e 6S/6M. O veículo é simulado também freando sem sistema ABS e a eficiência resultante comparada com as obtidas anteriormente. Os resultados são apresentados em figuras que mostram as forças normais dinâmicas ao pavimento, as aderências utilizadas pelos pneus e as eficiências atingidas pelas diversas configurações de ABS utilizadas no semi-reboque. Conclui-se de forma geral que configurações de ABS com mais sensores e válvulas moduladoras produzem uma eficiência maior e que a utilização de qualquer configuração de ABS como sistema complementar do sistema de freios de serviço, aumenta a eficiência de frenagem que é sempre superior ao do veículo sem sistema ABS. Esses resultados ajudam na preservação da dirigibilidade e estabilidade do veículo combinado, contribuindo assim na prevenção de acidentes de trânsito em situações de emergência. / This dissertation reports on the development of a simulation model for the analysis of the braking performance of tractor-semitrailer vehicles that use the ABS (Antilock Braking System). The model was developed using the virtual simulation technique of multibody systems with SimMechanics, a toolbox of Matlab/Simulink. In this simulation model the mechanical and geometrical parameters of the chassis, suspensions, brakes, adhesion coefficient, and load sensing valve were considered. When the vehicle is decelerating, the normal forces between the tire and road surface are obtained by the virtual model. These forces are the input of a subroutine in which the braking forces are calculated when the S Came brakes are triggered. Simulations of braking on straight line in road were made for average adhesion coefficient (0.4) and high adhesion coefficient (0.8). Efficiencies were obtained when the tractor used fixed ABS configuration of a 6S/6M type, and the semitrailer used the ABS type: 2S/lM (and 4.6); 2S/2M (and 4.6); 4S/2M (e4); 4S/2M (e6); 4S/3M (e4); 4S/3M (e6); 4S/4M (e4) and 4S/4M (e6) and 6S/6M. The results are presented in figures which show, the normal dynamic forces between tire and road, adhesions used by the tires and the efficiencies achieved by different ABS configurations installed in the semi-trailer. It is possible to conclude that in general ABS configurations with more sensors and modulating valves produce higher efficiency and the use of any configuration as a complementary system of the ABS brake system service increases the braking efficiency, which is always higher than that of a vehicle without ABS. The results help preserving the vehicle stability and maneuverability, preventing road accidents in emergency situations.

In today’s fast moving world, automobiles are facing challenges in terms of having to survive road accidents, increasing traffic, bad road-conditions and high/express ways. Brake systems play a vital role in controlling the vehicle speed while avoiding road accidents. The conventional brake systems consist of basically an actuator, transmission and frictional parts. This system is difficult for manipulated control by the driver during emergency and panic braking situations. In particular road and environmental conditions, it requires certain skill to have safe and effective brake control, which is always not possible from all drivers. Wheel locking is a predominant phenomenon during panic braking and this will cause vehicle skidding resulting in injuries and road accidents. In the case of a two-wheeler, being a single-track vehicle, skidding is one of the major causes for fatal road accidents due to loss in lateral balance. As the road safety regulations are becoming more stringent, the anti-lock brake systems (ABS) will replace the conventional brake systems in all road vehicles to avoid accidents and to improve vehicle safety. Early ABS systems, developed in the last 100-years, use intermittent and cyclic brake pressure control by sensing the wheel speed or wheel-slip as one of the major control inputs. Regulating the brake pressure with a preset threshold value is another method. These ABS systems have used electronics, or hydraulics or pure mechanical control. However, such ABS are not widely used in two-wheelers and other low cost vehicles till now, because of several limitations identified as follows: High cost, power supply needed for its operation in the case of intermittent and cyclic brake control, susceptibility to failure in the electronics system, interference from RF signals (from cell-phones for example), uneasiness to drivers from pedal pulsations with pedal noise, heavier weight, increased vehicle vibrations and failure modes of wheels due to torsional vibrations. The present research work is carried out to develop a new mechanical ABS concept, which will address most of the above problems. During braking, the change in rider-input force will change wheel reactions. This change is made proportional to the change in rider input force only upto wheel locking. Such a principle is used to develop the new mechanical ABS. The new concept regulates the output force from the ABS, by sensing the dynamic wheel reactions with increase in rider-response. The ABS output force is regulated by one of the following ways: (a) Slipping-down the lever-ratio or (b) preventing the excessive brake input force. Based on the parameters like less number of parts, least weight, simplicity, reliability, efficiency, durability, time-response, etc., the second method (of preventing the excessive brake input force) has been chosen. Further a new concept of ABS interconnecting system is proposed for usage between the front and rear wheels of the vehicle. This interconnecting system will ensure that the two mechanical ABS systems function at any kind of braking-balance between the front and rear applications. An analytical vehicle model has been developed with several input parameters like mass, geometry, inertia, aerodynamic properties, frictions of road and bearing-supports, road gradients, etc. From this analytical model, the dynamic wheel reactions and limiting adhesion of each tyre for various braking conditions are determined and the results are used to design the mechanical ABS. The same analytical model is used to predict the brake performance like stopping distance, vehicle deceleration and the vehicle speed variation for ideal braking conditions. The new ABS is modelled in Pro-E using the inputs from the analytical model. To evaluate the concept, a functional proto-type is built and fitted on a motorcycle. The ABS is evaluated for its functionality and performance at different road (level surface, up-gradients and down gradients) and environmental conditions (dry and wet road conditions). Using the VBOX II, proximate sensors and load-cells fitted on the vehicle, the vehicle stopping distance, wheel slip and pedal force are measured. The results show that wheel locking does not occur under panic driving conditions, which is the primary objective. In addition, the results show a good agreement with the predicted stopping distance and vehicle deceleration from the analytical model. As there is good scope for this new mechanical ABS for use in two-wheelers and other low cost vehicles, further research is needed to make this system work in curvilinear motion & banked surfaces.

This thesis deals with a conceptual design of small utility vehicle with three axles. The aim is to devise a suitable type of frame along with construction of all axles and a steering system, implementation of a drive train, a braking system and other basic equipment. Own solution is preceded by elaboration of a survey dealing with small utility vehicles produced nowadays as well as in the past together with a description of all variants of basic assemblies suitable for the construction of the specified vehicle.