<p>Research shows that flywheels have a significant potential for improving the performance of EV (Electric Vehicle) drivelines. Flywheels can be used as power buffers that even out the energy flow between the primary energy storage device and the EV traction motor. This improves the potential energy density and extends the lifetime of the primary energy storage device of the EV.</p><p>In this degree project a prototype of a flywheel-buffered driveline was constructed. The flywheel chosen was an electric motor/generator constructed at the Division of Electricity at Uppsala University. Lead acid batteries were used as the primary energy storage device in the driveline and the traction motor was a DC-motor.</p><p>Two DC/DC buck converters were designed for the driveline. The first limited the current from the batteries to the flywheel and the second controlled the power from the flywheel to the traction motor. Both converters were controlled by microcontrollers. The current limiter was controlled by a hysteresis controller and the DC-motor power was regulated manually, under the constraint of a maximum current PI-controller. The buck circuits were simulated in MATLAB Simulink prior to their construction.</p><p>The performance of the driveline was satisfactory, despite the poor efficiency of the DC-motor. The results showed that the efficiency of the flywheel and the power converters was relatively high and that the flywheel had excellent power-buffering properties.</p>

Research shows that flywheels have a significant potential for improving the performance of EV (Electric Vehicle) drivelines. Flywheels can be used as power buffers that even out the energy flow between the primary energy storage device and the EV traction motor. This improves the potential energy density and extends the lifetime of the primary energy storage device of the EV. In this degree project a prototype of a flywheel-buffered driveline was constructed. The flywheel chosen was an electric motor/generator constructed at the Division of Electricity at Uppsala University. Lead acid batteries were used as the primary energy storage device in the driveline and the traction motor was a DC-motor. Two DC/DC buck converters were designed for the driveline. The first limited the current from the batteries to the flywheel and the second controlled the power from the flywheel to the traction motor. Both converters were controlled by microcontrollers. The current limiter was controlled by a hysteresis controller and the DC-motor power was regulated manually, under the constraint of a maximum current PI-controller. The buck circuits were simulated in MATLAB Simulink prior to their construction. The performance of the driveline was satisfactory, despite the poor efficiency of the DC-motor. The results showed that the efficiency of the flywheel and the power converters was relatively high and that the flywheel had excellent power-buffering properties.

The goal of this thesis was to develop a powertrain model of a vehicle and parametrize itusing non-invasive sensors. The non-invasive sensors available were chassis dynamometer,the pedal robot and the vehicle’s on-board diagnostics which was accessed using a scantool. Non-invasive sensors were used so that the vehicle to model can easily be changed. Aparametrization methodology to parametrize the model for a new vehicle was also developedto facilitate the change of vehicle. The powertrain model is for cars with a combustion engineand a manual gearbox. The engine model consist of two static maps, a pedal map and an engine map. The pedalmap is created using the fact that a constant pedal position and engine speed gives a constantthrottle position. The engine map is created in similar manner using that a constant throttleposition and engine speed gives a constant engine torque. The engine model also uses a firstorder lag element to model the time delay from a change in pedal position to a change inwheel torque. The driveline model is a rigid driveline model that assumes that the clutch,driveshaft and propeller shaft are stiff. The developed parametrization methodology contains information on how to estimate theparameters of the model which are gear ratios, engine and driveline inertias, engine anddriveline losses, engine and pedal maps and the time constant for the time delay. The powertrain model was validated component wise, as standalone and integrated intothe vehicle model against data gathered with the help of the chassis dynamometer. For thestandalone and integrated validation the gathered data were for different driving cases, suchas up and down gear-shifting, engine braking and skipping gears. The standalone validationshowed that the model performed well for the presented driving cases and the results hadgood data fit for 3rd gear and higher. However not for 1st and 2nd gear due to problemsin the pedal map. The pedal map was constructed on the assumption that the same pedalposition for all gears gives the same throttle position, which was not always the case. Thiscaused problems in some areas of the engine and pedal maps however in the validation ofthe maps it was shown that the maps for the most part gave good results.

<p>The Automated Manual Transmission system Opticruise is dependent on signals from sensors located in different parts of the Scania trucks. These signals are of different qualities and have different update frequencies. Some signals and quantities that are hard or impossible to measure are also of importance to this system.</p><p>In this thesis a driveline observer for the purpose of signal improvement is developed and estimations of unknown quantities such as road incline and mass of the vehicle are performed. The outputs of the observer are produced at a rate of 100 Hz, and include in addition to the mass and road incline also the speed of the engine, output shaft of the gearbox, wheel and the torsion in the driveline. Further the use of an accelerometer and the advantages gained from using it in the observer are investigated.</p><p>The outputs show an increased quality and much of the measurement noise is successfully removed without introducing any time delays. A simulation frequency of 100 Hz is possible, but some dependency toward the stiffness of the driveline is found. The observer manages to estimate the road slope accurately. With the use of an accelerometer the road slope estimation is further improved and a quickly converging mass estimation is obtained.</p>

The aim of the thesis is to derive a mathematical model of the engine and driveline in a passenger car, capable of describing the wheel speed disturbances related to the engine and driveline. The thesis is conducted in order to improve the disturbance cancelation algorithm in the indirect tire pressure monitoring system, TPI developed by NIRA Dynamics AB. The model consists of two parts, the model of the engine and the model of the driveline. The engine model uses an analytical cylinder pressure model capable of describing petrol and diesel engines. The model is a function of the crank angle, manifold pressure, manifold temperature and spark timing. The output is the pressure in the cylinder. This pressure is then used to calculate the torque generated on the crankshaft when the pressure acts on the piston. This torque is then applied in the driveline model. Both a two wheel and a four wheel driveline model are presented and they consist of a series of masses and dampers connected to each other with stiff springs. The result is a 14 and 19 degrees of freedom system of differential equations respectively. The model is then validated using measurements collected at LiU during two experiments. Measurements where conducted of the cylinder pressure of a four cylinder petrol engine and on the wheel speed of two different cars when driven in a test rig. The validation against this data is satisfactory and the simulations and measurements show good correlation. The model is then finally used to examine wheels speed disturbance phenomenon discovered in the huge database of test drives available at NIRA Dynamics AB. The effects of the drivelines natural frequencies are investigated and so is the difference between the disturbances on the wheel speed for a petrol and diesel engine. The main reasons for the different disturbance levels on the front and rear wheels in a four wheel drive are also discussed.

Simulating the translatory motion of a vehicle during a gear shift gives a good basis to evaluate performance and comfort of a gear shift. This evaluation can be used for gear shifting strategy in an automatic transmission. A model of a diesel engine and it's electronic control system is developed to capture the engines behaviour in a vehicle simulation environment. The modelled quantities are brake torque, fuel consumption and exhaust gas temperature and are based on engine speed and pedal position. In order to describe these outputs the inlet air flow and boost pressure are also modelled and used as inner variables. The model is intended to be implemented on board a vehicle in a control unit which has limited computational performance. To keep the model as computationally efficient as possible the model basically consists of look-up tables and polynomials. First order systems are used to describe the dynamics of air flow and exhaust temperature. The outputs enables gear shift optimization over three variables, torque for vehicle acceleration, fuel consumption for efficiency and exhaust temperature to maintain high efficiency in the exhaust after treatment system. The engine model captures the low frequent dynamics of the modelled quantities in the closed loop of the engine and it's electronic control system. The model only consists of three states, one for the pressure build up in the intake manifold and two states for modelling the exhaust temperature. The model is compared to measured data from a engine test cell and the mean absolute relative error are lower than 6.8%, 7.8% and 5.8% for brake torque, fuel consumption and exhaust gas temperature respectively. These results are considered good given the simplicity of the model.

The Automated Manual Transmission system Opticruise is dependent on signals from sensors located in different parts of the Scania trucks. These signals are of different qualities and have different update frequencies. Some signals and quantities that are hard or impossible to measure are also of importance to this system. In this thesis a driveline observer for the purpose of signal improvement is developed and estimations of unknown quantities such as road incline and mass of the vehicle are performed. The outputs of the observer are produced at a rate of 100 Hz, and include in addition to the mass and road incline also the speed of the engine, output shaft of the gearbox, wheel and the torsion in the driveline. Further the use of an accelerometer and the advantages gained from using it in the observer are investigated. The outputs show an increased quality and much of the measurement noise is successfully removed without introducing any time delays. A simulation frequency of 100 Hz is possible, but some dependency toward the stiffness of the driveline is found. The observer manages to estimate the road slope accurately. With the use of an accelerometer the road slope estimation is further improved and a quickly converging mass estimation is obtained.

Linear vibration measurement and analysis techniques have appeared to be sufficient with most vibration problems. This is partially due to the lack of proper identification of physical nonlinear dynamic responses. Therefore, as an example, a vehicle driveshaft exhibits a nonlinear super harmonic jump due to nonconstant velocity, NCV, joint excitation. Previously documented measurements or analytical predictions of vehicle driveshaft systems do not indicate nonlinear jump as a typical vibration mode. The nonlinear jump was both measured on a driveshaft test rig and simulated with a correlated model reproduced the jump. Subsequent development of the applied moments and simplified equations of motion provided the basis for nonlinear analysis. The nonlinear analyses included bifurcation, Poincare, Lyapunov Exponent, and identification of multiple solutions. Previous analytical models of driveshafts incorporating NCV joints are typically simple lumped parameter models. Complexity of models produce significant processing costs to completing significant analysis, and therefore large DOF systems incorporating significant flexibility are not analyzed. Therefore, a generalized method for creating simplified equations of motion while retaining integrity of the base system was developed. This method includes modal coupling, modal modification, and modal truncation techniques applied with nonlinear constraint conditions. Correlation of resonances and simulation results to operating results were accomplished. Previous NCV joint analyses address only the torsional degree of freedom. Limited background on lateral excitations and vibrations exist, and primarily focus on friction in the NCV joint or significant applied load. Therefore, the secondary moment was developed from the NCV joint excitation for application to the driveshaft system. This derivation provides detailed understanding of the vibration harmonic excitations due to NCV joints operating at misalignment angles. The model provides a basis for completing nonlinear analysis studying the system in more detail. Bifurcation analysis identified ranges of misalignment angles and speeds that produced nonlinear responses. Lyapunov Exponent analysis identified that these ranges were chaotic in nature. In addition, these analyses isolated the nonlinear response to the addition of the ITD nonlinear stiffness. In summary, the system and analysis show how an ITD installed to attenuate unwanted vibrations can cause other objectionable nonlinear response characteristics.

In recent years, the impact of humans on the environment has been the subject of much debate. Car companies in particular are among the main actors in this environmental degradation with the polluting aspect of combustion cars. However, in recent years, these companies have started to switch to electric cars in order to reduce their impact on the environment. This is the case for Volvo, for example, where electrification is a priority. With the goal of becoming a climate neutral company by 2040, Volvo is driving innovation to reduce the use of polluting materials, such as oil.  Oil is not only used to power cars, but also in the fluids used to cool electrical machines or lubricate transmissions. However, alternatives to these fluids have emerged in recent years, such as glycerol-based or water-based lubricants. This Master Thesis aims to follow the evolution of water-based lubricants, but also to compare the performance of existing fluids within electric drivelines.  Water is known to have very good thermal properties but also to have a high electrical conductivity, which represents a big challenge for the use of this type of lubricant within an electric machine. It is with the aim of evaluating the impact of these properties that the following study investigates the electrical compatibility of a water-based lubricant within an electrical machine. The thermal performance of this type of fluid is also investigated and compared to that of an oil- based fluid also studied at Volvo. This master thesis will serve as a springboard for further studies of these lubricants, and will also raise questions and challenges that need to be addressed in the future in order to be able to take full advantage of the properties of these water-based lubricants.

The work presented in this thesis is dedicated to the study of transient tyre dynamics and how these influence the dynamic behaviour of the vehicle and its driveline, with the main focus being on low-to-zero speed manoeuvres such as pull-away events. The bulk of the work focuses on the amalgamation of the hitherto disparate fields of driveline modelling and detailed tyre modelling. Several tyre models are employed and their relative advantages and disadvantages analysed. The observed dynamic behaviour is correlated to the inherent structure of each tyre model in order for the most appropriate for driveline studies to be identified. The main simulation studies are split into two parts: the first comprises a study into isolated driveline dynamics; where the yaw, pitch and roll behaviours of the vehicle body are neglected. A relatively detailed driveline model with an open differential is used with tyre models of increasing complexity with the aim of determining when increased model detail fails to increase the accuracy of the results. The second part is concerned with the study of how the dynamics of the vehicle body and suspension affect tyre model performance and associated effects on the driveline behaviour. For this, the driveline and tyre models are incorporated into a full six degree-of-freedom vehicle model with full suspension effects. Frequency migration on low-μ surfaces is successfully explained via the decoupling of the vehicle and driveline inertias. Frequencies observed in FFT analyses of the simulation results correspond to those obtained through eigen-analysis of appropriately modified state-space models with varying degrees of coupling that reflect the vehicle travelling on uniform low- or split-μ surfaces. The main finding of the thesis is that this decoupling theory can also be applied to high-speed take-off manoeuvres, as it is the position along the tyre slip-force curve that dictates decoupling; i.e. if the curve has saturated. This leads to the effective traction stiffness being zero, which modifies the equations of motion and subsequently the system eigenvalues. A series of measurements are taken in order to verify the findings from the simulation work. Manoeuvres analogous to those simulated are carried out. It is found that only the simulation of split-μ conditions is necessary, as the results from the low-μ test show a similar pattern to those seen on the split-μ surface.