Abstract
Power split driveline ensures a hybrid vehicle good performance in fuel economy and emissions, but might bring about serious torsional vibrations at city traffic operation. A power split driveline is addressed in this paper to understand the mechanism behind the failure of its transmission shaft. Lumped-parameter models were established for the system at various engine and motor configurations corresponding to typical working conditions. Natural frequencies and mode shapes were calculated for each configuration. Sensitivity analysis reveals the variation of the natural frequencies with respect to the inertia or stiffness of the system. It is revealed that there exists unavoidable resonance with the system during vehicle operation, which should be the main reason of the shaft failure.