Self-excited torsional vibrations caused by clutch differentials in high-performance car drivelines

Torque splitting strategies adopting clutch units are increasingly used in modern powertrains to improve vehicle dynamics, enabling the transition between two-wheel drive and four-wheel drive. A significant drawback, however, is represented by the possible occurrence of self-excited vibrations. Therefore, a nonlinear multibody model of a full driveline has been developed to analyze these issues, validating the results with experimental data. The non-stationary behaviour of the driveline is found to be strongly dependent on the nonlinear friction characteristics. Stability maps let identify negative friction gradients of the clutch torque splitter as responsible of unstable oscillations, while modal analysis revealed a dominant localization of some modes within the whole transmission.