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In every driving condition powertrain and vehicle dynamics deeply influence each other. The main role of powertrain influence is played by the differential, which transmit the driving torque with respect to wheel kinematics. Many different solutions have been historically developed from pure mechanical devices (as open, self-locking, torque sensitive and speed sensitive) to semi-active and full-active differentials. The recently developed controlled differentials underlined the importance of a good project and tuning of this component to achieve a good performance of the vehicle, in terms of traction, stability, and, more over, drive “feeling”. This paper tries to cover the lack of present literature to provide analysis tools to be used in the preliminary phase of vehicle project in order to evaluate differential influence on vehicle performance.

While VDC systems usually operate on the engine torque and on brake pressures, new automotive applications try to use semi-active or active differentials in order to optimize the torque distribution on the wheels for traction maximization, driving comfort, stability and safety of the vehicle. The system presented in the paper comes out from the cooperation of Ferrari S.p.A. and Politecnico di Milano in the development of a new semi-active differential. In the paper a description of the vehicle dynamic control strategy, its development, and experimental results are given.