Research On Shifting Process Of AMT In Electric Vehicles

Electric vehicles’ motors inherit excellent external drive characteristics and speed andtorque control precision. The application of automatic manual transmission (AMT) inelectric vehicles can further extend their capacity of dynamic performance and energysaving and achieve more satisfying shifting quality as well. Based on the research project ofthe integrated motor-AMT integrating design, the parameter matching of the power trainsystem and the shifting control process of the AMT without clutch and synchronizer arestudied in this thesis.Firstly, according to the vehicle parameters and the driving requirements, someimportant parameters of the power train are matched. The constraints of the transmissionratios are built up following the selecting of the motor parameters. For the purpose of thetransmission ratios optimization, the power train model, including drive cycle model, drivermodel, motor model, transmission model and the whole vehicle dynamic model, togetherwith the energy consumption model and acceleration time calculating model, is establishedon the software platform of MATLAB/Simulink. Then, by employing the multi-objectiveoptimization genetic algorithm NSGA-II in the software ISIGHT, the optimal transmissionratios are identified.Secondly, the dynamic performance of shifting process is analyzed with sufficientconcern for shifting quality, and on the basis of it, the control strategy for the shiftingprocess is set up. The shifting control method of the proposed AMT without clutch andsynchronizer is illustrated and the sequent phases of shifting process are defined andmodeled with consideration for drive axle torsion. Key control technologies of the shiftingprocess are indicated and the control strategy of the shifting process is constructedaccording to the dynamic analysis above.Finally, concerning the important role which electric motors play in reducing thepower train torsional vibration, the optimal control law for motor torque is designed basedon linear-quadratic control theory. The state-space representations for the power trainbefore and after off-shifting are established, and the impact of the initial value of vitalvariables after off-shifting on torsional vibration is demonstrated. Then the objectivefunction is proposed in order to achieve better shifting quality and the optimal control lawis obtained. In the end, the motor torque control law is verified on MATLAB/Simulink and the simulation results show that it can suppress the torsional vibration of the power traineffectively.