Abstract
Hybrid electric vehicles (HEVs) require supervisory controllers to distribute the propulsion power from sources like an engine and motors. Control concepts based on optimal control theories such as dynamic programming (DP) and Pontryagin’s minimum principle (PMP) have been studied to maximize fuel efficiencies. These concepts are, however, not practical for real-world applications because they guarantee optimality only if future driving information is given prior to the actual driving. Instead, heuristic rule-based control concepts are widely used in real-world applications. Those concepts are not only simple enough to be designed based on existing vehicle control concepts, but also allow developers to easily intervene in the control to enhance other vital aspects of real-world vehicle performances, such as safety and drivability. In this study, a rule-based control for parallel type-2 HEVs is developed based on representative control concepts of real-world HEVs, and optimal control parameters are determined by optimization processes. The performance of the optimized rule-based control is evaluated by comparing it with the optimal results obtained by PMP, and it shows that the rule-based concepts can achieve high fuel efficiencies, which are close, typically within 4%, to the maximum values obtained by PMP.
Highlights
The depletion of fossil fuels is a global energy issue that is becoming more serious even as industrial demand for oil increases [1]
hybrid electric vehicles (HEVs) controllers based on optimal control theories like dynamic programming (DP) and Pontryagin’s minimum principle (PMP) produce optimal fuel
HEV controllers based on optimal control theories like DP and PMP produce optimal fuel efficiencies but have unsolved technical matters; rule-based controls have been used in most efficiencies but have unsolved technical matters; rule-based controls have been used in most
Summary
The depletion of fossil fuels is a global energy issue that is becoming more serious even as industrial demand for oil increases [1]. As alternatives to conventional vehicles, hybrid electric vehicles (HEVs) are a promising solution to save fuel and meet regulations. To improve the fuel efficiencies of HEVs, various types of powertrain configurations have been developed in the last two decades, varying in the layout of the transmission and the power sources; these include the series hybrid, parallel hybrid, power split hybrid, and multi-mode hybrid [6,7]. The power split hybrid system [8], represented by the Toyota Prius [9] which was introduced in 1997, has been considered to be a promising solution for vehicle hybridization [10,11], but a parallel hybrid system, applied in other vehicles like the Hyundai Ioniq, has recently shown outstanding performance in fuel efficiency that is close to or outperforms the power split hybrid system [12]
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