CVT discrete speed ratio optimizations based on energy efficiency for PHEV

The continuous speed ratio of the continuously variable transmission (CVT) changed rapidly, which made the quantity of oil intake and discharge of hydraulic system vary frequently, resulting in large energy loss and reduction in vehicle economy. In view of this issue, in this paper, taking a plug-in hybrid electric vehicles (PHEV) equipped with CVT as the research object, and a CVT discretely variable speed ratio optimization method based on genetic algorithm (DVROM-GA), which could reduce the energy loss and improve the system transmission efficiency, was proposed. Firstly, five driving modes of PHEV were studied to obtain the system transmission efficiency under different modes. Subsequently, the continuously variable speed ratio of CVT was divided into discretely variable speed ratios, and a genetic algorithm, which aimed at optimizing system transmission efficiency, was adopted to simultaneously optimize the number of gears and the discretely variable speed ratio to obtain the shifting rules under different driving modes. Ultimately, to verify the effectiveness of the proposed method, compared with the energy consumption of continuously variable transmission, the proposed method could improve the economy of PHEV by 2.2%.