Research On Two-speed AMT Control System Of Pure Electric Vehicle

With the exhaustion of fossil resources, people have higher requirements forenvironmentally friendly vehicles. Electric vehicles entered the people’s field ofvision. The transmission of electric vehicles has become one of the hot topics. AMTis based on the manual transmission and its shift actuatoris controlled by themicrocontroller to realize automatic shifting. Not only AMT inherits the advantagesof efficiency and low cost of manual transmission, but also can switch gear accordingto the performance of the vehicle state as the automatic transmission.The paper was based on the characteristics of wide speed range andpositive-negative rotating of drive motor. Combined with an electric vehicle underdevelopment, the AMT system of a two-speed, no clutch and no reverse gear wasdeveloped. Main contents and innovations are as follows:1、Comparison and analysis of the shift drive motor of AMT was finished, thusdetermined the use of brushless DC motor. According to the control target of shifttime, the paper selected the model of brushless DC motor.2、Power and economy shift strategy of AMT was studied and the paperdeveloped a shift strategy for it.3、The paper developed the TCU hardware and software based on single-chip of16-bit Freescale MC9S12XS128.The hardware mainly was composed ofMC9S12XS128minimum system, CAN communications interface circuits, serialinterface circuits, three-phase bridge driver circuit, power supply circuit, a currentdetection circuit and the Hall signal adjusting circuit; the software included some ofthe major shift control strategies under different conditions, definition of CANmessage protocol and send and process of CAN message-receiving.4、Based on the AMT control system and shift actuator,bench test show thatengage a gear and pick neutral action can be completed stable and reliable.CANcommunication module can be stable and reliable packet reception and transmission.Based on gear shifting strategy byusing drive motor active speed control. Shorten theshifting process synchronization time, thereby reducing the shift time, reduces shift shock and sense of frustration, improved shifting comfort and electric vehicle ridecomfort.