Multi-Objective Optimization of Gear Ratios in Two-Speed Dual Clutch Transmissions for Electric Vehicles

The rational matching and optimized design of the gear ratios for the transmission system of an electric vehicle (EV) are of great importance for improving economic and dynamic performances. This paper sets a pure electric vehicle (PEV) as the research object. First, the four common driving cycles considering the urban and suburban areas are selected and analysed which are applied for designing the gear ratios. Second, the parameter matching of the basic indicators of the EV performance and the selection of gear ratios are explored according to the analysis of the four selected driving cycles. Furthermore, gear ratios are set as the variables and the ant colony optimization (ACO) algorithm is applied to optimize the gear ratios by setting the sum of the power demand of the selected common driving cycles, the sum of the average motor efficiency of the chosen driving cycles, and the acceleration time as the objective function in order to optimize the vehicle performances. A two speed dual clutch EV model is constructed in MATLAB/Simulink for verification of the results. The simulation results demonstrate the effectiveness of the optimisation in comparison with the previous gear ratios, where both economic and dynamic performance improvements are evident.