Technical Note: Some limitations of the chassis dynamometer in vehicle simulation

Sie sind hier: Homepage > Suche

Technical Note: Some limitations of the chassis dynamometer in vehicle simulation

Plint, M. A. / Martyr, A. J.

The chassis dynamometer is the standard tool for legislatively prescribed emission tests. For emission testing and many other vehicle test purposes the dynamic response is an adequate approximation to ‘on road’ conditions. This is not necessarily true if the requirement is to study vehicle driveline dynamics. The present analysis arose from two quite separate requirements to study driveline oscillations and ‘judder’ using chassis dynamometers of the same eVective inertia as the vehicle. During the studies by the authors it became clear that the dynamics of the vehicle-dynamometer combination diVer in important respects from those of a vehicle on the road. As the eVective inertia of the dynamometer falls the natural frequency of the engine-driveline-vehicle system rises while the oscillatory energy imparted to the vehicle falls rapidly. For reasonably accurate simulation of driveline vibration the roll inertia should be some five times that of the vehicle. It is shown that electrical simulation of inertia, as employed in most modern chassis dynamometers, is unsatisfactory where oscillatory phenomena are being studied.