Mode Shift Mechanism And Control Method For Dual Mode Drive System Of Electric Vehicle

The electric drive system is the core component of the electric vehicle,its configuration mainly includes two kinds of centralized driving and distributed driving.The distributed drive system can control the dynamic stability of the whole vehicle by adjusting the torque of each driving wheel independently,but there is a lack of torque self balancing mechanism between the coaxial driving wheels.When one side drives the system,the vehicle is prone to instability,such as deviation,and the centralized drive system uses a differential to drive the coaxial wheel drive.The dynamic moment is roughly distributed,and the power and economy are improved by multi gear transmission,but the auxiliary control device must be added to realize the function of driving antiskid and stability control.In this paper,an electric vehicle dual mode coupling drive system,which can realize centralized drive and can realize distributed drive and has two gear variable functions,is studied.The mechanism of mode switching is analyzed,and the corresponding control method is put forward to realize the fast and smooth switching of the driving mode.The main contents of this paper are as follows:(1)A dual mode drive system model for electric vehicle is established.The system model mainly includes the synchronizer model,the variable die execution mechanism model,the variable mode motor model,and the torsional vibration model of the transmission system based on the gear contact model.The torsional vibration model mainly considers the damping and stiffness between the gears,including the gear contact model between the centralized drive system and the distributed drive system.(2)A control model of drive motor speed and torque management is established.According to the structural characteristics of the dual mode coupling drive system and the dynamic characteristics of the mode switching,the mathematical model of the permanent magnet synchronous motor is set up in this paper,and the speed control model based on direct torque control is established.The control method of the drive motor is set up to reduce the impact.(3)An electromechanical coordinated control strategy based on dual motor active speed regulation mechanism is established.Cooperative control strategy includes two motor speed regulation strategy,torque management control strategy and variable die actuating control strategy.In order to improve the quality of mode switching,the optimal control curve of mode switching is fitted with variable modulus drive motor,and a predictive functional controller is established.Complete the simulation verification of control effect.According to the simulation results of the system,the idea of adding a torsional shock absorber between the driving motor and the drive mechanism is proposed,and the function of the torsional shock absorber to improve the variable die quality is verified by the simulation.(4)The prototype of electric vehicle dual mode coupling drive system is trial manufactured.Through the bench test simulation of the vehicle mode switching condition,the feasibility of the prototype of the driving system is verified,and the test model is reproduced.The test process of the whole vehicle verifies the correctness of the theory and the feasibility of the control strategy of the two mode coupling drive system of the electric vehicle.