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The aim of this work is to define the core of a stability control, called Active Vehicle System, for a hybrid Formula SAE car that will compete in the next season in the upcoming Alternative Energies (Class 1A) class. The vehicle on which the control system will act is equipped with two electric motors on the front axle and an internal combustion engine connected to the rear axle by the way of a semi-active differential. The layout of the car under consideration has been defined with the purpose of getting the most effectiveness by the Active Vehicle System, whose role is to define a yaw torque to be applied to the vehicle in order to correct its behavior during each maneuver. The results of the Upper Controller will be actuated by two Lower Controllers, one dedicated to the electric motors and one to the semi-active differential. On such controlled vehicle some testing maneuvers have been performed, in order to check its functionality.

The Electro actuated Limited Slip Differential (e-LSD) can help increasing the dynamic features of the vehicle, but to implement a well designed control logic it is necessary a deep knowledge of the actual friction torque built up by the differential clutch. This work presents the development of such a control law that takes into account the wear depth progression. To carry out this task, an alternative method has been used to study the clutch discs engagement depending on the wear rate. The method takes advantages from a mixed approach with a numerical and an experimental part. Using a general purpose block-on-ring test bench, the tribologic analyses were performed following the ASTM G77 standard; thus, the friction coefficient has been investigated in the contact between discs with molybdenum treatment and steel alloy discs, as well as its variation depending on the wear rate.

In a Formula SAE car, as for almost all racecars, suppressing or limiting the action of the differential mechanism is the technique mostly adopted to improve the traction exiting the high lateral acceleration corners. The common Limited Slip Differentials (LSDs) unbalance the traction torque distribution, generating as a secondary effect a yaw torque on the vehicle. If this feature is electronically controlled, these devices can be used to manage the attitude of the car. The yaw torque introduced by an electronically controlled LSD (which can also be called SAD, “Semi-Active Differential”) could suddenly change from oversteering (i.e. pro-yaw) to understeering (i.e. anti-yaw), depending on the driving conditions. Therefore, controlling the vehicle attitude with a SAD could be challenging, and its effectiveness could be low if compared with the common torque vectoring systems, which act on the brake system of the car.