Instantaneous Crankshaft Torque Measurements - Modeling and Validation

A simulation model for the dynamic properties of multi-cylinder engines is developed. Specifically, the model is used to describe the relation between the individual cylinder pressures and the resulting torque in the crankshaft. The model is validated against a 5-cylinder SI-engine equipped with a crankshaft integrated torque sensor. The simulation model developed is based on a system of first order nonlinear differential equations where the crankshaft dynamics are expressed as interconnected mass-spring-damper elements. The motivation is to investigate how instantaneous crankshaft torque measurements can be used to deduce information on the combustion process, cylinder by cylinder, for the purpose of engine control. Therefore, a computationally simple simulation method is introduced. For the model validation, an engine testbed has been developed which includes a standard production engine equipped with a crankshaft integrated magneto-elastic based torque sensor and cylinder pressure sensors. The torque sensor provides a crank-angle resolved measurement signal. The model was validated against measurements collected during engine tests at several load cases. The cylinder pressure signals acquired were used as input to the simulation model and the resulting simulated torque was compared with the measured torque signal with promising results.