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Powertrain modeling for realtime simulation

The goal of this thesis was to develop a powertrain model of a vehicle and parametrize it using non-invasive sensors. The non-invasive sensors available were chassis dynamome- ter, the pedal robot and the vehicle’s on-board diagnostics which was accessed using a scan tool. Non-invasive sensors were used so that the vehicle to model can easily be changed. A parametrization methodology to parametrize the model for a new vehicle was also developed to facilitate the change of vehicle. The powertrain model is for cars with a combustion engine and a manual gearbox. The engine model consist of two static maps, a pedal map and an engine map. The pedal map is created using the fact that a constant pedal position and engine speed gives a constant throttle position. The engine map is created in similar manner using that a constant throttle position and engine speed gives a constant engine torque. The engine model also uses a first order lag element to model the time delay from a change in pedal position to a change in wheel 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 the parameters of the model which are gear ratios, engine and driveline inertias, engine and driveline losses, engine and pedal maps and the time constant for the time delay. The powertrain model was validated component wise, as standalone and integrated into the vehicle model against data gathered with the help of the chassis dynamometer. For the standalone and integrated validation the gathered data were for different driving cases, such as up and down gear-shifting, engine braking and skipping gears. The standalone validation showed that the model performed well for the presented driving cases and the results had good data fit for 3rd gear and higher. However not for 1st and 2nd gear due to problems in the pedal map. The pedal map was constructed on the assumption that the same pedal position for all gears gives the same throttle position, which was not always the case. This caused problems in some areas of the engine and pedal maps however in the validation of the maps it was shown that the maps for the most part gave good results.

Simon Lind


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