Passive and active limited-slip differentials are used in high-performance cars to optimize the torque distribution on the driving wheels for traction maximization, driving comfort, stability and active safety of the vehicle. In this paper, detailed and reduced dynamic models for the simulation of four kinds of differential are presented. The models refer to the limited-slip steering differential with two clutches. The model of the conventional differential, of the mechanical limited-slip differential and of the controlled limited-slip differential can be obtained by simplification. The detailed model allows the simulation of the internal phenomena that influence the differential dynamics. The reduced model focuses only on the main dynamic behaviour of the differential. Some simulations show the use of the reduced model to compare the effects of the four differentials on the vehicle dynamics.
while Vehicle Dynamics Control 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, MAGNA STEYR and Politecnico di Milano in the development of a semi-active differential. In the paper a description of either the physical layout of the system, its capabilities, and of the control software is given. Experimental results on an existent vehicle are shown.
One important task of electrification of vehicle powertrain is the functional integration of all new systems in respect of the performance, comfort and emission restrictions. In this particular case, starting from a mass produced vehicle platform in the small vehicle segment, the requirement was to keep the originally installed powertrain largely unchanged, but on the other hand enabling hybrid operating functions such as boosting and recuperating and additionally providing some torque vectoring features, under all relevant driving situations. The paper describes and explains the possibilities and limitations of an electrically supported four wheel drive system: first in simulation by use of a mathematical model and then, the experiences gained in the actual development of a prototype car, will be reported. A special focus will be put on the methodology of the development of a model based hybrid controller.
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