Modelling and active damping of engine torque ripple in a power-split hybrid electric vehicle

Torsional vibrations in the power drivetrain are a serious problem for power-split hybrid electric vehicles (HEVs) since the engine is directly connected to the transmission system. The torque ripple also decreases the performance of such vehicles and passenger comfort. The purpose of this paper is to investigate the vibrational performance induced by the engine ripple torque of a power-split HEV under the control of active damping. First, a detailed dynamic model of a power-split HEV is introduced to analyse the dynamic characteristics of the system. Subsequently, a simplified dynamic model of the transmission is proposed; this model simplifies the dynamic analysis of the transmission and makes active vibration control possible. Then, an active vibration controller based on the filtered-x least mean square (FxLMS) algorithm is applied to deal with the vibration in the power-split HEV. The electric motors of the powertrain are used as active damping actuators. The proposed approach is authenticated with simulations. The simulation results show that in steady-state conditions, by applying the active damping algorithm, over 60% of the fluctuation torque in driveline shafts is reduced at different velocities and driving modes, demonstrating that the proposed strategy is effective.