A New Dynamometer Test Rig to Develop Drive Lines for All-Wheel Driven Vehicles 881736
To develop drivelines for four-wheel driven vehicles, the design for a new drive line test cell had to address the following key issues: Overall reduction in development time through reduction in testing time, quality improvement of test data and the ability to simulate road tests in the dynamometer cell.
The paper first lists the major tasks to be performed by the test rig. In addition to driveline endurance tests, component interaction during operation is to be investigated for a wide variety of simulated driving conditions. The driveline is to be correctly loaded dynamically during acceleration and deceleration to test behavior under transient conditions. Tests typical for all wheel driven vehicles are to include variations in torque distribution between axles during rapid loading changes as experienced by a spinning wheel, engagement and disengagement of the 4-wheel drive, cornering etc.
The test system designed to meet these requirements uses 4 independent, high response electric dynamometers, each coupled directly to the axles of the driveline. The four dynamometers simulate the loading of the driveline in an actual vehicle. The control concept is based on the mathematical relation between drive and tractive forces and their action upon each wheel.
Full electric inertia simulation added features previously difficult to obtain on dynamometers using chassis rolls or flywheels for the simulation of vehicle mass.
The paper describes the simulation techniques as they are applied to study the effect of rapid changes in wheel torque/load differentials, the engagement of the 4-wheel drive, the effect of anti-lock braking systems and difference in wheel radii.
Speed and torque graphs show a simulated vehicle accelerated from stand still to maximum speed, gear changes, and the effect of a spinning wheel. These graphs and comments on operating experience are from a drive line test system designed and built by Asea Brown Boveri and installed at the development center of the Porsche AG in Weissach, W. Germany.