Identification of Driveline Parameters using an Augmented Nonlinear Model

Modern approaches for engine control assume the knowledge of the dynamic properties connecting the engine via driveline to the road. A formally identical problem arises when a combustion engine is operated on a test bench, with an electrical machine simulating the wheel load. While in some cases design information allows sufficient estimation of the parameters, in many other cases it may prove more adequate to determine them using measurements. This is usually complicated by the fact that measurements of driveline quantities are disturbed by gas exchange in the cylinder. As this paper shows, a suitable representation of the plant allows to concentrate the disturbances arising from the compression into a nonlinear periodic term acting in parallel to a static nonlinear feedback caused by friction. If standard linear parameter identification methods are used, the effect of this concentrated nonlinearity corresponds to a possibly infinite number of additional poles, which, however, depend on the rotational speed of the shaft. Using this property, it turns out possible to use a standard ARMAX identification approach to determine the model of the driveline. This is confirmed by measurements performed on an engine test bench.