Design of a Speed Ratio Control Method for Electric Vehicle Continuously Variable Transmission
At present,when formulating powertrain control strategies for electric vehicles,the main focus is on the working status of the motor,while ignoring the operating status of the continuously variable transmission,which leads to poor efficiency.In view of this,the continuously variable transmission is considered as a whole in this paper,and a speed ratio control method for continuously variable transmission is designed to optimize the overall efficiency of electric vehicle operation.Firstly,the variation patterns between the engine torque and the fuel consumption rate are clarified,as well as between the driving motor torque and the electrical energy consumption.Based on this,the corresponding speed ratio on the minimum fuel electric energy consumption line or within a small range is found while not exceeding the speed ratio range of the continuously variable transmission.And the optimal economic transmission system speed ratio is obtained based on different vehicle speeds,that is,the target speed ratio.Then,the error between it and the current speed ratio is used as the control term to complete the speed ratio control.Finally,the experiments are carried out to verify the efficacy of the proposed method.The test results show that using the proposed method,the vehicle can travel longer distances within the same time,and consumes lower fuel and electricity per 100 kilometers.This indicates that the proposed method can not only accurately control the speed ratio under different working conditions,but also significantly improve the fuel efficiency of electric vehicles.
electric vehiclescontinuously variable transmissionspeed ratio controlreasonable scopetarget speed ratiocontroller
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