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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.

By analyzing the dynamic distortion in all body closure openings in a complete vehicle, a better understanding of the body characteristics can be achieved compared to traditional static load cases such as static torsional body stiffness. This is particularly relevant for non-traditional vehicle layouts and electric vehicle architectures. The body response is measured with the so-called Multi Stethoscope (MSS) when driving a vehicle on a rough pavé road (cobble stone). The MSS is measuring the distortion in each opening in two diagonals. During the virtual development, the distortion is described by the relative displacement in diagonal direction in time domain using a modal transient analysis. The results are shown as Opening Distortion Fingerprint ODF and used as assessment criteria within Solidity and Perceived Quality. By applying the Principal Component Analysis (PCA) on the time history of the distortion, a Dominant Distortion Pattern (DDP) can be identified.

In the last years automotive industry has shown a growing interest in exploring the field of vehicle dynamic control, improving handling performances and safety of the vehicle, and actuating devices able to optimize the driving torque distribution to the wheels. These techniques are defined as torque vectoring. The potentiality of these systems relies on the strong coupling between longitudinal and lateral vehicle dynamics established by tires and powertrain. Due to this fact the detailed (and correct) simulation of the dynamic behaviour of the driveline has a strong importance in the development of these control systems, which aim is to optimize the contact forces distribution. The aim of this work is to build an integrated vehicle and powertrain model in order to provide a proper instrument to be used in the development of such systems, able to reproduce the dynamic interaction between vehicle and driveline and its effects on the handling performances.

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.