Shifting Actuator Design And Control Of Two-speed AMT For Electric Vehicle

The shifting actuator design and shifting control strategy of two-speed AMT for electric vehicles are proposed in the paper,with purpose to improve shifting performance.It is rapidity,comfort,and accuracy,which separately corresponds to time cost,fork acceleration and displacement error during shifting,that evaluate the performance.The shifting actuator is driven by brushless DC motor(BLDC)and is made up of worm reducer,cam,fork and synchronizer.The profile of cam is designed smoothly,which could definitely improve shifting comfort.With regard to the instant and varied load during shifting process,the dynamic response,which could be solved by dynamic equation,is simulated in MATLAB/Simulink to analyze the shifting performance of 2AMT.What’s more,as the transient response generated by frequent start and brake of shifting motor can never be ignored,the shifting motor with established mathematical model is controlled by double loop system,which consists of PI speed controller and current hysteresis controller.The simulation result shows that it takes about 1.4 seconds to finish shifting process,and the shifting comfort is improved by cosine cam groove compared to the spiral one.Last but not least,the bench test for the driving assemble equipped with 2AMT was carried out in various driving conditions to thoroughly evaluate the feasibility of actuator design and control strategy.The test showed that it took about 1.6~2.0 seconds for a normal shifting,which was close to the result of simulation.Based on the test,it’s suggested to decrease the reduction ratio of worm gear and gradient of cam groove properly,but increase the power of shifting motor to improve shifting performance.