Research On Control Strategy Of Direct Drive System Of Motor Transmission For Pure Electric Bus

The use rate of pure electric vehicles in China is increasing year by year,which has made great contribution to energy saving and environmental protection.Especially in the urban road section of our country,compared with the traditional vehicles,pure electric vehicles have the characteristics of quick start response,small energy consumption,better quietness,and brake energy recovery when braking frequently,which are highly praised by the market.However,the development of pure electric vehicle is restricted by its slow charging speed and low mileage.The state has also issued a series of plans and policies for the development of pure electric vehicles.The investigation shows that there is good market feedback on the development and application of pure electric bus.Because the application of pure electric bus is more in line with the situation of large passenger flow and complex driving conditions in China.The characteristics of fixed-point driving of pure electric bus can effectively solve the two major problems of battery charging maintenance and endurance mileage.Therefore,the development of pure electric bus is more practical.The direct drive system of motor transmission is an important part of the power assembly of pure electric vehicle.It has the advantages of small volume,saving installation space,small loss of power in the transmission process and cost saving.The research on the control strategy of direct drive system is helpful to improve the power,economy and ride comfort of pure electric bus,and plays a key role in the development of pure electric bus.This paper mainly focuses on the control strategy of the direct drive system of the motor transmission of the pure electric bus.Firstly,according to the performance requirements of the target bus and the parameters of the whole vehicle,the permanent magnet synchronous motor(PMSM)and AMT are selected as the driving motor and transmission of the direct drive system of the motor transmission.Then,the parameters of PMSM and AMT are determined by the matching formula of drive motor and transmission.Based on the actual research of the direct drive system of motor transmission at home and abroad,this paper analyzes the logical characteristics and specific steps of gearshift without clutch in the direct drive system.Secondly,according to the logical characteristics of gearshift without clutch and the specific steps,the control strategy of the direct drive system of motor transmission is formulated.There are vector control strategy of PMSM,traditional two parameter shift strategy of AMT and coordinated control strategy.Then,according to Matlab / Simulink,the whole vehicle simulation model is established,which includes driver model,motor and controller model,AMT shift logic model,coordination controller model,transmission system model and whole vehicle motion model.The control strategy is applied to the whole vehicle simulation model,and the specific road conditions and driver operation are designed,and the reasonable reliability of the control strategy of the direct drive system is verified by simulation.Then,in order to realize the multi-performance comprehensive shift law under different accelerator pedal opening.The comprehensive evaluation function is established,and the multi-performance comprehensive shift law curve is obtained by using particle swarm optimization algorithm.The shift strategy is written into the vehicle simulation model,and its comprehensive performance is simulated and verified.The shift impact of the direct drive system of motor transmission is analyzed.In order to reduce the impact of shifting,the mathematical model is established,and it is found that the key factor affecting the impact of shifting is the loading curve of the driving motor.The fuzzy PI control method overcomes the shortcomings of traditional PI control,and optimizes the load curve of the drive motor.The simulation results show that the optimization method can reduce the shift impact of the motor transmission direct drive system reasonably and reliably.Finally,the test-bed of the direct drive system of the motor transmission is built,and the shift law is verified by the test-bed.After the test analysis,the control strategy is stable and reliable and reasonable.