This work deals with a fork bending oscillation phenomenon observed during hard braking on bicycles. The observed oscillation is described with experimental data and an attempt is made to understand the underlying root cause. Therefore, a multibody model consisting of the front wheel and the fork is employed to simulate a braking maneuver. The self-oscillation is replicated in simulation and implications on the brake process are derived from it. Fork and tire oscillations on bicycles are rarely described in scientific literature. An oscillation due to tire resonance on high-speed motorcycles was described by Cossalter [1]. However, the mentioned speed dependence is not found in the present case under investigation. Klug et al. [2] were the first to report an oscillation of the fork inclination angle during braking. They noticed oscillations in the front wheel speed signals measured with a speed encoder mounted on the fork. Measurements of accelerometers and gyroscopes placed on the fork near the hub showed these oscillations on the forks inclination angular rate and vertical acceleration as well. This makes the phenomenon relevant for suspension and braking control. They also described the distorting effect of fork bending on the wheel speed signal and the wheel slip calculation derived from it. This work tries to identify a root cause of the fork bending oscillation and investigates its influence on the stopping performance.

No / Braking system characteristics, brake system performance and brake system component design parameters that influence brake pedal ‘feel’ in a passenger car have been studied using the simulation modelling package AMESim, in particular to model the linear and nonlinear characteristics of internal components. A passenger car hydraulic brake system simulation model incorporating the brake pedal, booster, master cylinder, brake lines and calipers has been developed to predict brake system response to assist in the design of braking systems with the desired brake pedal force / travel characteristic characteristics to create good brake pedal ‘feel’. This has highlighted the importance of system components, in particular the master cylinder and caliper seal deformation, and the operating characteristics of the booster in determining the brake pedal force / travel characteristic. The potential contribution of these 3 components to brake pedal ‘feel’ improvement has been investigated, and the results of the AMESim model have been verified using experimental measurement data. The model can be used in the future to provide an accurate prediction of brake system response at the design stage thereby saving time and cost.

This article presents a simulation study into effects of compliant (flexible) components (such as the engine subframe and the lower control arm) and their deflections on the characteristics of a vehicle experiencing steering drift during straight-line braking. The vehicle front and rear suspension are modelled using multi-body dynamic analysis software. The front suspension model represents theMacPherson strut design of the vehicle and includes a rack and pinion steering system, brake system, engine subframe, and a powertrain unit. The model has been analysed under two steering control methods: fixed and free control. Suspension characteristics and the effect of deflections arising from the subframe and the lower control arm on these suspension characteristics have been analysed. The simulations confirmed that variation of component stiffness and interactions within components give rise to side-to-side deflections that could affect lateral drift during braking. It is concluded that side-to-side variation of suspension characteristics can have a detrimental effect on lateral drift during braking and that compliant components whose stiffness varies from side to side can cause different side-to-side deflections that can induce and influence variation in suspension characteristics such as toe steer angle that can lead the vehicle during braking.

More than 900 bicyclists died in motor vehicle crashes in the United States in 2020, which represents a 50% increase from 2010 and the highest number of bicyclist deaths in nearly 35 years [1]. Reversing this trend will require efforts on multiple fronts, including reducing vehicle speeds and improving roadways and vehicles to be more hospitable to cyclists. Automatic emergency braking (ABB) with cyclist detection is a vehicle countermeasure with potential to prevent bicycle-motor vehicle crashes. AEB systems, which typically warn drivers of an impending collision and brake if drivers do not respond, have been shown to reduce vehicle-to-vehicle rear-end crash rates by 50% [2] and pedestrian crash rates by 27% [3]. Little is known about the real-world effects of ABB with cyclist detection on bicycle crashes. Subaru's EyeSight system, which includes ABB, has been capable of detecting cyclists in parallel configurations beginning in model year (MY) 2013 in the United States. The ability to detect cyclists in perpendicular configurations was added to some models beginning in MY 2022. The goal of this study is to evaluate the effects of the early version of EyeSight on U.S. bicycle crashes. [from Introduction]

One of the benefits of electric vehicles (EVs) and hybrid vehicles (HVs) is their potential to recuperate braking energy. Regenerative braking (RB) will minimize duty levels on the brakes, giving advantages including extended brake rotor and friction material life and, more significantly, reduced brake mass and minimised brake pad wear. In this thesis, a mathematical analysis (MATLAB) has been used to analyse the accessibility of regenerative braking energy during a single-stop braking event. The results have indicated that a friction brake could be downsized while maintaining the same functional requirements of the vehicle braking in the standard brakes, including thermomechanical performance (heat transfer coefficient estimation, temperature distribution, cooling and stress deformation). This would allow lighter brakes to be designed and fitted with confidence in a normal passenger car alongside a hybrid electric drive. An approach has been established and a lightweight brake disc design analysed FEA and experimentally verified is presented in this research. Thermal performance was a key factor which was studied using the 3D model in FEA simulations. Ultimately, a design approach for lightweight brake discs suitable for use in any car-sized hybrid vehicle has been developed and tested. The results from experiments on a prototype lightweight brake disc were shown to illustrate the effects of RBS/friction combination in terms of weight reduction. The design requirement, including reducing the thickness, would affect the temperature distribution and increase stress at the critical area. Based on the relationship obtained between rotor weight, thickness and each performance requirement, criteria have been established for designing lightweight brake discs in a vehicle with regenerative braking. / Ministry of Higher Education of Malaysia

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. / Institution of Mechanical Engineers (IMechE)

This thesis presents an investigation of braking system characteristics, brake system performance and brake system component design parameters that influence brake pedal force / displacement characteristics as ‘felt’ by the driver in a passenger car. It includes detailed studies of individual brake system component design parameters, operation, and the linear and nonlinear characteristics of internal components through experimental study and simulation modelling. The prediction of brake pedal ‘feel’ in brake system simulation has been achieved using the simulation modelling package AMESim. Each individual brake system component was modelled individually before combining them into the whole brake system in order to identify the parameters and the internal components characteristics that influence the brake pedal ‘feel’. The simulation predictions were validated by experimentally measured data and demonstrated the accuracy of simulation modelling. Axisymmetric Finite Element Analysis (using the ABAQUS software) was used to predict the behaviour of nonlinear elastomeric internal components such as the piston seal and the booster reaction disc which was then included in the AMESim simulation model. The seal model FEA highlighted the effects of master cylinder and caliper seal deformation on the brake pedal ‘feel’. The characteristics of the brake booster reaction disc were predicted by the FEA and AMESim simulation modelling and these results highlighted the importance of the nonlinear material characteristics, and their potential contribution to brake pedal ‘feel’ improvement. A full brake system simulation model was designed, prepared, and used to predict brake system performance and to design a system with better brake pedal ‘feel’. Each of the brake system component design parameters was validated to ensure that the braking system performance was accurately predicted. The critical parameter of brake booster air valve spring stiffness was identified to improve the brake ‘pedal ‘feel’. This research has contributed to the advancement of automotive engineering by providing a method for brake system engineers to design a braking system with improved pedal ‘feel’. The simulation model can be used in the future to provide an accurate prediction of brake system performance at the design stage thereby saving time and cost.

The automotive industry plays a significant role in global CO2 emissions. A transition towards electric vehicles is part of the solution to lower CO2 emissions. While electric vehicles are beneficial from an environmental standpoint, it generates new challenges and technology for the driver to adapt to, emphasising the importance of human interaction. A possible solution to affect drivers to adopt new behaviours is using Gamification inIn-vehicle Information Systems. This study implies that drivers do not fully see the potential of regenerative braking to extend the vehicle's range while contributing to safer and more predictable driving. Thus, this thesis explores the implementation of gamification in a vehicle context by using a prototype in a vehicle simulator environment to observe whether it affects driver behaviours to increase regenerative braking usage. This study uses a design study method with a qualitative research approach resulting in a high-fidelity prototype developed through an iterative design process. The prototype mechanics originates from the M-PM-O framework, found through an in-depth literature study. The mechanics are designed into gamification elements using established design principles for In-vehicleInformation Systems. Further, the prototype was evaluated using Volvo Cars vehicle simulators. The results demonstrated that gamification in a vehicle context is possible and that the prototype affected driver behaviours to increase regenerative braking usage. Through the analysis and discussion, four design guidelines emerged for the design of gamification elements in IVIS. However, the study also raises questions regarding the general feasibility of incorporation. Overall, this study opens for further studies regarding gamification's safety and long-term effects in a vehicle context. / Fordonsindustrin spelar en betydande roll i de globala CO2 utsläppen, ochen övergång till elektriska fordon har identifierats som en del av lösningenför att minska utsläppen. Även om elektriska fordon är fördelaktiga ur ettmiljöperspektiv, ställer de nya krav på förare och tekniken i fordon, vilketökar vikten av mänsklig interaktion. För att uppmuntra förare att anta nyabeteenden mer hållbara körbeetenden har spelifiering identifierats som enmöjlig lösning i bilens informationssystem. Studien antyder att bilförare inteser potentialen i regenerativ bromsning för att öka räckvidden i bilensamtidigt som den främjar säkrare och mer förutsägbart körande. Syftet meddenna studien är att utforska spelifiering element i bilensinformationssystem genom att utveckla och testa en prototyp i enbilsimulator för att undersöka om den kan stödja förarbeteenden att ökaregenerativ bromsanvändning. Studien använder sig utav en designstudiemetod med en kvalitativ forskningsansats som resulterar i en högtdetaljerad prototyp utvecklad genom en iterativ designprocess. I endjupgående litteraturstudie identifieras tre spelifiering element som användsi studien. Spelifiering elementen designas med hjälp av etableradedesignprinciper för bilinformationssystem. Vidare utvärderades prototypen i Volvo Cars simulatormiljö. Resultatenindikerade att spelifiering i bilens informationssystem kan stödjaförarbeteenden att öka regenerativ bromsanvändning. Genom analys ochdiskussion uppdagades tre design riktlinjer för designen av spelifieringelement i bilens informationssystem. Överlag, öppnar studien för vidarestudier gällande spelifierings säkerhet och långtidseffekter i en bilkontext.

The increased prevalence of crash avoidance technologies like autonomous emergency braking necessitates understanding of occupant responses during low-speed frontal pre-crash braking and low-severity crash events. Active human body models (HBMs) have emerged as valuable tools to evaluate occupant safety during these events, but must be validated with relevant volunteer data to accurately represent the responses of live occupants. The objective of this dissertation was to quantify the occupant responses of relaxed and braced 5th percentile female and 50th percentile male volunteers during low-speed frontal and frontal-oblique sled tests designed to simulate pre-crash braking and low-severity crash events. A study comprised of 160 low-speed sled tests was performed with 20 volunteers. The volunteers' kinematics, kinetics, and muscle responses were compared to determine how altering impact direction (frontal and frontal-oblique), impact severity (1 g and 2.5 g), demographic group (mid-size male and small female), and muscle state (relaxed and braced) affected occupant responses. The volunteers' occupant responses were significantly affected by impact direction, impact severity, demographic group, and muscle state. The frontal-oblique tests resulted in greater leftward excursions compared to the frontal tests. Increasing the pulse severity resulted in greater forward excursions, reaction forces, and muscle activation. The male volunteers exhibited greater forward excursions and reaction forces compared to the female volunteers. However, the two demographic groups exhibited similar muscle activation during the sled tests. Bracing increased the volunteers' initial joint angles, muscle activation, and reaction forces prior to the sled tests. Bracing decreased forward excursions and increased reaction forces during the sled tests. The relaxed volunteers exhibited greater relative changes in occupant responses compared to the braced volunteers. Overall, this study demonstrated that muscle activation significantly affected the volunteers' kinematics, kinetics, and muscle responses for both mid-size males and small females during low-speed events. Observed differences between demographic groups were more prominent when relaxed and more diminished when braced. These results underscore the importance of validating active HBMs with relevant volunteer data in order to be more representative of live occupants for a wider range of demographic groups in varying muscle states. Finally, this dissertation provides a large, comprehensive, and novel biomechanical dataset that can be used to develop and validate active HBMs for use in assessing occupant response during frontal pre-crash braking and low-severity crash events. These models will help improve the understanding of potential injury risk and development of effective vehicle safety systems for use during low-speed events. / Doctor of Philosophy / Computer models, known as active human body models (HBMs), have emerged as tools that can be used to assess occupant safety during low-speed vehicle crashes. In these types of events, occupants have enough time to react and potentially brace before the crash, which could in turn affect their responses during the crash. It is important to understand how occupants respond during crashes so that effective vehicle safety systems can be developed. Active HBMs are particularly valuable because they can simulate muscle activation to reflect the response of live occupants. However, data are needed from live occupants to ensure that these models are accurate. To gather this data, a study was performed where volunteers experienced low-speed frontal sled tests when they were relaxed and braced. The sled tests were designed to simulate pre-crash braking and low-severity vehicle crashes. Mid-size male and small female volunteers were recruited to participate to represent the standard adult occupant populations used in current frontal impact vehicle safety standards. A motion capture system was used to measure the volunteers' forward motion, load cells were used to measure the volunteers' exerted reaction forces on the test buck, and electrodes were used to measure the volunteers' muscle activity. The volunteers' responses were significantly different between the relaxed and braced muscle states, and between the males and females. Comparing between males and females, the males moved farther forward and exerted larger reaction forces, but both demographic groups exhibited similar muscle responses. Comparing between muscle states, bracing increased the volunteers' muscle activation and reaction forces before the sled tests. Bracing also increased the volunteers' reaction forces during the sled tests, but decreased forward movement. Overall, the volunteers exhibited greater relative changes in response when they were relaxed compared to when they were braced. Overall, this study demonstrated that muscle activation significantly affected the volunteers' responses for both mid-size males and small females during low-speed events. These results highlight the importance of developing active HBMs with relevant volunteer data in order to be more representative of live occupants. Finally, the data from this study can be used to develop active HBMs to improve their accuracy, so that the models can be used to assess occupant safety during low-speed frontal vehicle crashes. This will help improve the understanding of potential injury risk and development of effective vehicle safety systems, to reduce the number of injuries caused by vehicle crashes.

The rise in overall powertrain complexity and the stringent performance requirements of a hybrid electric vehicle (HEV) have elevated the role of its powertrain control strategy to considerable importance. Iterative modeling and simulation form an integral part of the control strategy design process and industry engineers rely on proprietary ?legacy? models to rapidly develop and implement control strategies. However, others must initiate new algorithms and models in order to develop production-capable control systems. This thesis demonstrates the development and validation of a charge-sustaining control algorithm for a through-the-road (TTR) parallel hybrid (diesel-electric) powertrain. Some unique approaches used in powertrain-level control of other commercial and prototype vehicles have been adopted to incrementally develop this control strategy. The real-time performance of the control strategy has been analyzed through on-road and chassis dynamometer tests over several standard drive cycles. Substantial quantitative improvements in the overall HEV performance over the stock configuration, including better acceleration and fuel-economy have been achieved.