A new control strategy for hybrid electric vehicles equipped with a continuously variable transmission

Abstract

The electric assist control strategy is one of the well-known methods for managing the power sources of hybrid electric vehicles. Because of the dependence of the electric assist control strategy approach on its parameters, optimization of this strategy can improve its performance, which results in lower fuel consumption and lower emission levels. However, one of the main concerns about optimization of this strategy is its dependence on the driving behaviour. This paper aims to propose a new control strategy based on the electric assist control strategy with a smaller number of control parameters and less dependence on the driving behaviour. This strategy is usable only for vehicles equipped with a continuously variable transmission. In this strategy, the engine’s operating point is determined by considering its best point in terms of the fuel consumption and the emissions, and also the high-efficiency region of the powertrain. After optimization of the proposed strategy and the electric assist control strategy approach, the methods are compared. It is shown that the proposed strategy provides a better performance in terms of the fuel consumption and the emissions during all the considered driving cycles. Moreover, it is demonstrated that the performance of the proposed strategy has less dependence on the driving-cycle pattern because fewer parameters are used than in the electric assist control strategy. This feature makes the devised control strategy desirable for real-world conditions where the vehicle undergoes various driving patterns.