| Electric vehicles have become the future direction of development of vehicles.However,there are many problems restricting the development of electric vehicles.The limited driving distance is one of key issues to limit the development of electric vehicles.It is an effective method to improve the driving distance of electric vehicles to increase the energy efficiency of electric drive system.As the motor has a wide speed range,with low-speed constant torque,high-speed constant power characteristics,most of electric vehicles are equipped with a fixed speed ratio transmission.However,the high-efficiency area of motor is usually in a certain speed range.It can improve the working time in high-efficiency area for electric vehicle with multi-speed transmission.This paper takes a three-axle hybrid electric vehicle the platform and takes the 2-speed AMT in electric drive axle as the studying object.This paper focuses on the shifting control strategy of 2-speed AMT in three-axle hybrid electric vehicle.The main contents are as follows:1.Modeling of vehicle powertrain systemFirstly,the structural characteristics and working principle of the three-axle hybrid electric vehicle powertrain are analyzed.Secondly,the forward simulation model is selected as the modeling method.Then,a three-axle hybrid vehicle powertrain model is established based on MATLAB/Simulink simulation platform.Finally,the model is validated.2.Development of AMT shifting control strategyFirst,the shift time and shift impact are chosen as the evaluation index.Secondly,the five stages of the electric drive AMT shift process are analyzed in detail and the mechanism of the shift impact at different stages in the shift process is studied,and the torque unloading and recovery rate are determined.Then,a model predictor controller is designed to realize the motor speed control.Finally,the control strategy of switching between AMT block and second gear is developed.3.Research on shifting control strategy of 2-speed AMT in three-axle hybrid electric vehicleFirstly,the function design and model of 2-speed AMT controller for three-axle hybrid vehicle are established.Secondly,the shift control strategy of 2-speed AMT under normal vehicle operation mode is analyzed,and the corresponding shift control strategy is worked out.Then,in order to prevent the the "cycle shift" phenomenon when the emergency braking,AMT control strategy when emergency braking is developed;Finally,the three typical faults are selected and the corresponding fault diagnosis method and processing strategy are worked out.The significance of this paper is developing a more comprehensive shift control strategy for electric drive 2-speed AMT and solving the issues such as shift quality deterioration,shift failure,the vehicle anchor when vehicle emergency braking and AMT system failure.The reliability and fault tolerance are improved effectively. |
