Shifting Control Strategy For Two-speed AMT Of Pure Electric Vehicle

With the continuous development of pure electric vehicles. The requirement of driving range, acceleration time and other performance requirements become higher. The control of the cost of the car is also more and more harsh. The transmission system of pure electric vehicle has become a trend. Equipped with multi gear transmission of pure electric vehicles can improve the performance of electric vehicles, reduce vehicle requirements for motor performance. To a certain extent, it also can improve the vehicle mileage. Equipment with two-speed AMT of pure electric vehicle has become a hot research at home and abroad. It increase a gear compared with the fixed gear reducer. In the vehicle driving process, Reasonable shifting control strategy has a great significance for the development of the vehicle economy and the power performanceIn this paper, select the current more popular pure electric vehicles which equipment with two-speed AMT for the study. By analyzing the effect of system efficiency on the performance of the vehicle, studied the shifting control strategy of the two-speed AMT. Specific contents as follows:1) Based on the theoretical analysis and experimental results, the charge discharge efficiency of the power battery was analyzed and the corresponding efficiency model was established. Based on the experimental data, the efficiency of the driving motor is obtained by interpolation and fitting with the experimental data. A theoretical analysis is made on the internal power losses of the two-speed AMT, and combined with the experimental data obtained from the two-speed AMT bench test, use the experimental data to modify the parameters of the transmission theory calculation mode. Made the two-speed AMT efficiency model is consistent with the experimental results. So we can obtain efficiency calculation model of the whole power transmission system of the pure electric vehicle2) Based on the two-speed AMT of pure electric vehicle system efficiency model. Divide main working mode of the AMT of pure electric vehicle and analysis the system efficiency effects on economic system when vehicle working on the driving conditions, established the best economic gear rise curve of the two-speed AMT under different battery SOC. From the system efficiency level analyzed the input power of the motor characteristics and output power of the battery characteristics. With the optimal output power of the system, established the best dynamic gear rise curve of the two-speed AMT under different battery SOC. Finally, analysis the whole vehicle braking force when vehicle working on the braking conditions, get the regenerative braking force under different braking strength and different gear Based on the system efficiency under different braking strength established the best economic gear reduse curve of the two-speed AMT under different battery SOC and different braking strength.3) On the basis of the best economy and the best dynamic shift curve. Using the fuzzy control rules to identify the driver's power requirement under the driving condition. The specific shift curve of the two-speed AMT is modified by the identification results, made the shift schedules tradeoff between the best economic and dynamic characteristics. By analyzing the influence of SOC on the optimal power and economic shift schedule. Use the battery SOC as the threshold division of the shift rule under different driving conditions, so as to establish the two-speed AMT comprehensive shift strategy.4) As a result of the driver's intention, the vehicle forward simulation model is established. Simulation and analysis are carried out on the optimal economic shift schedule under different acceleration and deceleration conditions and typical city cycle conditions, and compared with the traditional method of shifting schedule. And the optimal power shift schedule is compared with the traditional method in the full acceleration pedal opening. In the model of the integrated shift rule, the simulation analysis is carried out to verify the proposed shift schedule have certain applicability in the daily driving process.