Study On Coordinnated Control Of The Shifting Process For Electric Vehicles With The Two-speed Planetary Transmission

In the thesis, the objects are the motor-two gears planetary gearshift mechanism for anelectric school bus and its hydraulic shift control system. In order to improve the shiftingquality of the vehicle, the coordinated control of the powertrain during the shifting proessand some dynamic simulations were finished in detail. The combined clutch/brake isadopted as the shifting actuator, which is driven by hydraulic and the driven moter adoptsthe torque control mode.Based on the detailed two gears planetary transmission model, the dynamic of shiftingwas analyzed using the Lagrange method. Subsequently, the powertrain dynamics model ofshifting process was established based on the equivalent lumped mass method. The workingstate during the shifting process can be acquired by taking advantage of the above dynamicmodel. By analyzing the characteristics of the hydraulic shift control system for combinedclutch/brake, mathematical models of charging and discharging process of the hydrauliccontrol system were established. The simulation software MATLAB/Simulink was used toanalyze the duty ratio of the high-speed on/off valve–shifting pressure-flow dynamiccharacteristics of each hydraulic component in the system under the transient condition. Asresult, the change law of the shifting pressure during the charging and discharging chargingand discharging process of the hydraulic control system and the relationship between theduty ratio of high-speed on/off valve and the shifting pressure were obtained.The optimal control trajectory of the motor torque and the shifting pressure of thecombined cluth/brake and traking control method were studied. In accordance with thedynamic model during the shifting process, this thesis has established the state-spaceequation which takes change speed of the motor torque and the friction torque of thecombined clutch/brake ad its control variable. The shift jerk and the dissipated energy wereregarded as quadratic performance index, the motor torque and the shifting pressure optimalcontrol were achieved under disturbing matrix using the linear quadratic optimal controltheory, integrating the relationship between the friction torque and the shifting pressure.Having aimed at unobservable shifting pressure and nonlinear hydraulic executive machine,this thesis has designed the sliding model controller by using the sliding model controltheory. Optimal track of the shifting pressure of the combined clutch/brake was realized toincrease the precision and robustness of the control system. The whole simulation model which integrates hydraulic shift control system, theoptimal control model and sliding mode control model was established. And the dynamicresponses of the transmission in shifting process under different motor torque, vehiclespeed and resistance torque were achieved. The simulation results proved the coordinatedcontrol of the powertrain during the shifting process can get the commendable shift quality.