Representation, generation, and optimization methodology of hybrid electric vehicle powertrain architectures

Since the first commercial application of hybrid electric vehicle (HEV) powertrains, power-split architectures have been a major option for construction of HEV powertrains. Are power-split HEV powertrains the best solution to all design-objective settings, or will other design schemes arise that better fit the design requirements? To generalize the system optimization to different types of HEV powertrains, representation and generation methods for generic architectures of HEV powertrain are developed, which completely clarify the available design domain of the HEV powertrain architecture. Then, an integrated multi-objective optimization that simultaneously optimizes the architecture, component parameters, and control strategy is engineered to obtain the Pareto optimal design schemes of HEV powertrains in various situations of trade-off between acceleration capacity and fuel economy. The results suggest that the power-split HEV powertrain is superior in fuel economy and the HEV powertrain adopting the architecture with torque coupling among the engine and motor/generators (1-1 type) is superior in acceleration capacity. However, the achievable optimal fuel economies of power-split and 1-1 type HEV powertrains are almost the same, whereas the trade-off ranges of power-split HEV powertrains are narrower than those of the 1-1 type architecture HEV powertrains. Conceptually, the results reflect that when design methods are restricted to a specific subspace of the design domain, due to the limited consideration of variation in HEV powertrain architectures, the theoretical optimality of the design is not guaranteed. Practically, 1-1 type architecture can be more adaptive to different trade-offs among design objectives. For variations in design objectives, the appropriate HEV powertrain can be constructed by modifying in component parameters of the 1-1 No. 5 architecture HEV powertrain rather than reconstruction of the powertrain with architectural modifications. (C) 2020 Elsevier Ltd. All rights reserved.