Study On Shift Control And Ratio Optimization For Automatic Transmission In Pure Electric Vehicle

With the energy shortage and environmental pollution increasingly serious, pure electric vehicle has drawn more attention of the government and auto companies by its advantages in energy saving and environmental protection. It is regarded as one of the future trends of vehicles. The transmission which is applied into the pure electric vehicle also becomes a hot topic. Contract with the single-speed gearbox, multi-speed automatic transmission can not only reduce the performance requirements of drive motor and power battery, but also improves the dynamic performance and energy economy of vehicle by changing motor working points through shift automatically.Taking the pure electric vehicle as the platform and the two speed automatic mechanical transmission (AMT) as the studying object, this paper focuses on researching the shift control and ratio optimization. The main contents are as follows:1. The parameter matching for the major components of the powertrain system is implemented according to the main parameters and design indexes of the vehicle. An analysis involves in the influence of the number of gears and the transmission ratio on dynamic performance and fuel economic is made detailed. The two speed AMT is chosen as the transmission.2. On basis of analyzing the architecture of the two speed AMT and traditional shift schedule, this paper proposes a comprehensive shift schedule formulating method of the two speed pure electric vehicles which takes dynamic and economic performance into account simultaneously. This paper establishes the mathematics model of each stage of shifting process and analyzes the impact of shift control parameters on shift performance. Based on those analyses, the control method of the driving motor and shifting motor is put forward, and by the way the shifting process control strategy is developed.3. In order to improve the dynamic performance and energy economy of pure electric vehicle. This paper proposes a ratio optimization method of the transmission which is on basis of the comprehensive shift schedule. In the meanwhile, conducts a simulation research on the dynamic and economic performance of the vehicle with ADVISOR, so as to validate the accuracy of this optimization model and the effectiveness of the pure electric vehicle development program.4. According to the function requirements of the transmission control unit (TCU), this paper utilizes the microcontroller unit MC9S12XS128 as core chip to design the TCU. Taking advantage of PWM and CAN modules, the TCU can achieve the function of coordinated controlling the driving motor and gear shifting actuator. The development of the TCU provides support for the AMT to realize the function of shifting automatically.