Quality Optimization And Coordinated Control Of The Shifting Process For Electric Vehicles With Large Order Planetary Transmission

In this thesis,the object is an electric drive system integrated with a drive motor and a two-speed large order ratio planetary automatic transmission for an electric vehicle,which has the advantages of high transmission efficiency and large torque transmission.The coordinated control of the drive motor and the combination clutch can improve the shortcomings of the long shift time,long interruption time of powertrain and poor shift quality of the conventional transmission.Based on the project of extended-range electric school bus,the dynamic model of the transmission shift process is established,the dynamic characteristics of the shift process are studied to reveal the factors affecting the shift quality.The discrete-stage and multi-target control strategy coordinated control strategy of the drive motor and the combined clutch is proposed and validated by HIL(hardware-in-the-loop)simulation.According to the structure of the large-order ratio planetary transmission,the dynamics model of the two-speed large-order planetary transmission during the shifting process is established based on Lagrange equation the equivalent lumped mass method.In addition,the longitudinal dynamics model and transmission system model of the vehicle are established based on the dynamics of the vehicle,including the drive motor model,transmission system and load model,hydraulic pressure control system model.The shifting process of the drive motor-large-order planetary transmission has the dynamics characteristics of discrete stage and multi-constraints.The shifting process is divided into five stages according to the characteristics of system dynamics,and the control objects,and control targets of each stage are analyzed.From the simulation of shifting process,shift quality is jointly influenced by several factors: on one hand,the residual rotation speed after the motor speed regulation stage will influence the clutch/brake engagement time,shift jerk and sliding friction work.The torque change rate during torque unloading and torque recovery stage will directly influence the longitudinal acceleration of the vehicle and cause jerk;mutation in clutch/brake engagement friction torque will influence shift jerk,shift time and sliding friction work.In the perspective of reducing power interruption,shift jerk and friction work,shift quality index is selected as shift time,shift jerk and friction work.The multi-stage and multi-target control strategy which jointly control drive motor and hydraulic system is proposed to improve shifting quality.The hardware-in-the-loop(HIL)simulation experiment platform based on Speedgoat,vehicle controller,real pedal,and host computer display is established.The control strategy is generated through RTW(Real-Time Workshop)and embedded into the vehicle controller.In order to verify the real-time performance of the shift control strategy,the HIL simulation experiment of vehicle automatic gearshift is carried out,and the real-time control strategy of gearshift control is verified.Based on the natural hydraulic pressure output curve of the hydraulic system,the shift quality is optimized through the torque compensation of the drive motor.The shift control optimization problems are constructed,including the state equations of the control system,the target functional,and the state constraints.Using the pseudo-spectral optimization control algorithm,the torque compensation control trajectory of the drive motor is obtained and the optimal shift quality is obtained.