| The torque distribution method of multi-power source pure electric vehicles(MSEV)has important impact on the vehicle economy.However,current optimal allocation of demand torque for MSEV is mostly based on the optimal efficiency of the motor system,ignoring the transmission system efficiency.This allocation strategy cannot guarantee the optimal economy of the entire vehicle.In addition,in the simulation calculation of vehicle economy,the charge-discharge efficiency of the power battery is often regarded as a fixed value,resulting in a large difference between the simulation result and the actual energy consumption.To improve the economy of the vehicle and accuracy of its simulation calculations,the efficiency characteristics of the battery,motor and transmission system should be comprehensively considered when optimizing the demand torque and analyzing performance of the MSEV.In this study,the dual-motor four-wheel-drive pure electric vehicle(DMFEV)was taken as the research object,and following aspects of research were performed.(1)Modeling of dual-motor four-wheel-drive pure electric vehicle.The structure and control architecture of the DMFEV were analyzed.The battery and motor efficiency model were established based on the experimental data,respectively,and the influence of battery internal resistance characteristics on the vehicle energy consumption was analyzed.The transmission principle and power loss composition of the two-stage reducer on the front and rear axles were analyzed,and the efficiency model of the two-stage reducer was established.The whole vehicle dynamics was analyzed,and the dynamic model of DMFEV was established.(2)Research on torque distribution strategy based on the optimal motor efficiency.Based on the motor efficiency numerical model,the traversal optimization algorithm was used to optimize the motor torque distribution coefficient,and then the drive torque distribution strategy based on motor efficiency optimization was established.The mode selection strategy and braking force distribution strategy under braking conditions were formulated,and the required torque in the regenerative braking mode was optimized with the traversal optimization algorithm.The simulation of vehicle economy was performed and comparison with the average torque distribution strategy was made.The comparison results show that the torque distribution strategy based on the optimal motor efficiency is better than the average torque distribution strategy at the aspect of economy.(3)Improved torque distribution strategy considering the efficiency characteristics of the reducer.Based on the optimal torque distribution strategy of motor efficiency,the influence of the transmission efficiency of reducer on vehicle energy consumption and torque distribution strategy were analyzed.Combined with the efficiency numerical model of motor and reducer,the total efficiency numerical model of motor and reducer was calculated.Then,the optimal torque distribution strategy based on the efficiency of motor and reducer was formulated,and the economic simulation analysis was carried out.The simulation results show that the torque distribution strategy considering the efficiency characteristics of the reducer can better reflect the actual running state and energy consumption level of the vehicle.(4)Simulation and actual vehicle verification of torque optimal distribution strategy based on the analysis of pedal characteristics.A driver model was established to simulate the driver’s operation of the pedal during actual driving.An analytical control strategy of linear pedal characteristics based on the rated external characteristics of the motor was established to identify and calculate the required torque.To reduce the jerk of the vehicle and obtain better comfort of vehicle,the changing rate of torque during the motor’s responses process was limited.The forward simulation model was established to analyze the strategy,and the accuracy of the simulation results was verified by the real vehicle test. |
PDF Full Text Request