Design of Virtual Crank Angle Sensor based on Torque Estimation

Abstract: The topic of thesis is estimation of the crank angle based on pulse signals from an induction sensor placed on the flywheel. The engine management system performs many calculations in the crank angle domain which means that a good accuracy is needed for this measurement. To estimate the crank angle degree the torque balance on the crankshaft based on Newtons 2nd law is used. The resulting acceleration is integrated to give engine speed and crank angle. This approach is made for two crankshaft models, the rigid crankshaft approach and the lumped mass model. The latter can capture the torsional effects of the crankshaft twisting and bending due to torques acting on it. This is then compared to a linear extrapolation of the engine speed which is the chosen method today. To validate results experiments was performed where data for 36 stationary operating points was gathered. The results indicate that using a torque based model and predicting torsion improves the accuracy of the crank angle measurement especially for higher engine speeds. The rigid crankshaft approach does not give enough improvement of the accuracy to warrant further work.