WSEAS Transactions on Circuits and Systems
Print ISSN: 1109-2734, E-ISSN: 2224-266X
Volume 11, 2012
Coordinated Control of a Series-Parallel Hybrid Electric Bus During EV/HEV Mode Transition
Authors: , , ,
Abstract: Hybrid electric buses have been a promising technology to improve fuel economy and vehicle drivability. Due to the distinct transient response characteristics between different power sources and the discontinuity of the transmitted clutch torque, the output torque fluctuations of hybrid powertrains and the resulting vehicle jerks may occur during mode transitions, especially for the transition from the EV (electric vehicle) mode to the HEV (hybrid electric vehicle) mode. Aiming at achieving a smooth transition from the EV mode to the HEV mode for a series-parallel hybrid electric bus, this paper proposes a transient control strategy to coordinate the diesel engine and the motors during the transition process. The EV/HEV mode-transition control strategy is developed according to the operating status of the clutch, and the engine throttle is restricted during the transition process. In this control strategy, a fuzzy adaptive inference system is developed to estimate the difference between the actual and target engine torques. Then, the estimated torque difference is incorporated with a sliding mode controller to regulate the output torques of the integrated starter generator (ISG)and the traction motor (TM) to reduce the torque fluctuations in the powertrain. A simulation is performed using a forward-facing HEV model to validate the effectiveness of the proposed control strategy, and the results show significant reductions in torque fluctuations and vehicle jerks during the EV/HEV mode transition.
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Keywords: series-parallel hybrid electric bus, EV/HEV mode transition, transient response, fuzzy adaptive sliding mode control, coordinated control