Torsional Vibration Analysis of Multiple Driving Mode Hybrid Bus Drivetrain

Several hybrid electric driveline topologies have been introduced for vehicles in order to reduce emissions and improve energy efficiency in the transportation sector. This study introduces a novel configuration for a hybrid electric bus driveline. The designed driveline is capable of operating in pure electric, series and parallel hybrid modes. The torsional vibration analysis of the proposed drivetrain is performed for different driving mode configurations. The finite element method is applied to solve the torsional natural frequencies and mode shapes of the driveline. The model contains mass-elastic data of drive shafts, a diesel engine, a permanent magnet generator and a traction motor, as well as clutches and couplings. Different modelling strategies are discussed, and a sensitivity analysis is performed in order to determine the effect of different modelling parameters on the system’s torsional frequencies and mode shapes. Different excitation frequencies arising from the diesel engine and electric drives are identified and compared to the natural frequencies.