Research On Efficiency Optimization And Shift Control Of Pure Electric Vehicle With Two-speed Planetary Gear Transmission

How to optimize the transmission system to improve the cruising range is an important issue for pure electric vehicles,among which the multi-speed transmission and the incidental shift performance have received extensive attention.In this paper,considering the improvement of vehicle economy and the optimization of shifting performance,a hierarchical control system is designed for the shifting problem of twospeed planetary gear transmission(PAT).The main research contents are as follows:(1)Parameter matching and dynamic modeling.According to the dynamic performance indicators,the drive motor parameters of the two-gear pure electric vehicle and the transmission ratio of the two-gear PAT are matched,which provides the parameter basis for the follow-up work.Based on Newton’s second law,the driving motor,the two-gear PAT and the vehicle longitudinal dynamics model are established and implemented with MATLAB/Simulink,which provides a simulation verification platform for subsequent work.(2)Formulate the shifting law and optimize the parameters to reduce the energy consumption of the drive motor.According to the efficiency MAP of the drive motor and the initially matched PAT transmission ratio of the two gears,and taking the intersection of the efficiency-vehicle speed curves of the two gears as the shifting point,an economical shifting rule is formulated.In order to reduce the energy consumption of the vehicle under the NEDC cycle condition,the transmission ratio and the shift law are optimized based on the genetic algorithm.The simulation results show that the energy consumption of the drive motor is reduced.(3)Formulate a shifting strategy to solve the problem of shifting performance optimization derived from multi-shifting.The shift target strategy is formulated,and the meaning of each signal point in the shift process is clarified.Considering the influence of motor coordinated control on the output torque during the shifting process,four shifting execution strategies are formulated,and combined with the formulated shifting rules,the shifting performance of each strategy under different accelerator openings is simulated and compared.The results show that the motor has the best performance under the strategy of inertial participation in coordinated control,so it is selected as the shift execution strategy in this paper.(4)Based on the formulated shifting strategy,the upper LQR controller is designed to further optimize the shifting performance.Firstly,the state space equation of the power transmission system is established,and then combined with the state variables and control variables related to shifting performance,the performance index function is designed,the Riccati equation is solved to obtain the LQR feedback control gain,and the optimized LQR controller is formed.Comparing it with the control method before optimization,the results show that the optimized control improves the shifting performance.In addition,the LQR control is a state feedback control,so a sliding mode observer and a Romberg observer are designed for the problem that some state information is difficult to obtain.The simulation comparison and analysis are carried out under the interference of measurement noise.The results show that the observation error of the mode observer is smaller and the robust performance is better under the given interference.(5)Based on the input requirements of the upper controller to the actuator,the lower hydraulic execution system is designed for tracking execution.The underlying hydraulic actuation system is designed,and the relationship between the pressure of the actuating cylinder and the control signal of the on-off valve duty ratio is clarified through the established flow pressure model.The tracking control is derived and proved based on the sliding mode Back Stepping algorithm,and an adaptive law is designed for the parameter uncertainty of the hydraulic oil bulk modulus.The simulation results show that the lower-level actuator can achieve robust tracking of the upper-level control target.In this paper,a layered control system is designed to improve the cruising range of pure electric vehicles and optimize the shifting performance.