In this paper, a power management system for hybrid electric vehicles is developed and shown to improve the vehicle fuel consumption in various working conditions. A best-mode concept is defined based on the results of the dynamic programming global optimization strategy. It is shown that the use of exclusive control relations for each working mode improves fuel saving. The working state of the engine and one electric motor is used to determine the best-mode of powertrain operation. The best-mode classification also considers the battery state of charge. This enables the controller to specify near optimal working points in a wide range of state of charge. The control rule for each different work-mode is developed based on the dynamic programming results and applying the particle swarm optimization algorithm. The results show that the best-mode controller is capable of achieving fuel consumptions around 97% of that of the offline dynamic programming.

Hybrid electric vehicles (HEVs) have been developed as a promising way to decrease the fuel consumption and emissions of conventional vehicles. Although the noise emission of HEVs is generally lower than that of conventional vehicles, it is still an issue, especially in urban transportation. In this paper, a power management strategy is developed to minimize the annoying noise of the engine for an HEV. This is a modified version of the strategy that was originally established based on the speed ratio of continuously variable transmission (CVT) as the control parameter (CVT-based strategy). The engine combustion noise is assessed using the experimental data of the in-cylinder pressure. Also, the engine brake specific fuel consumption (bsfc) is defined from the experiments. The bsfc and noise data are implemented in the power management strategy. The proposed strategy offers a better performance in terms of reducing engine noise and fuel consumption in comparison with an electric assist control strategy (EACS). On the other hand, the proposed strategy results in a lower level of engine noise than the original CVT-based strategy at the expense of slightly increasing the fuel consumption. For instance, the noise level (dB) in an urban dynamometer driving cycle using the proposed strategy is 49% lower than the case of CVT-based strategy, while the vehicle FC is about 1.1% more than the CVT-based case.

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