The Study On Drivability Of The Electric Vehicle Equipped With Electric-mechanical Continuously Variable Transmission

Mounts of electric vehicles doesn't equippied with transmission part,the actual torque or rotational speed output characteristic of power unit couldn't satisfy with the requirements of complicated driving conditions without transmission part.Electric-mechanical continuously variable transmission(EM-CVT),clamped by disk spring and driven by motor,could be applied to the electric vehicles.To verify the functional performance of the EM-CVT matching with the electric vehicle,the control system frame of EV equipped with the EM-CVT has built up on the electric platform.The drivability could reflect the response characteristics and the ride comfort in the driving condition of the car,based on the subjective evaluation of the driver,the prototype vehicle which equipped with EM-CVT has some insufficient performence of drivability needs to be optimized.The paper presents the typical drivability evaluating test condition and the main point of the drivability evaluating.Focus on the insufficient performence of drivability,the power control strategy,CVT regulating strategy,CVT ratio control strategy has been re-optimised,the main works can be listed:(1)Analyses the drivability evaluating method of traditional vehicles,based on the typical evaluating test condition of the traditional vehicles,the typical evaluating conditions and the evaluating events of the electric vehicles is achieves,analyses the longitudinal dynamic both of the driving mode and braking mode,summarizes the influence factor of the drivability of the electric vehicles;(2)Analyses the system configuration of the electric vehicle equipped with the EM-CVT,the physical model of the motor has researched,based on the mathematic motion equation of the motor,the mathematic equation of the asynchronous motor has been built up,analyses the relationship between the power of the battary and the SOC,the charge and discharge model has been built up;the driving system model,clamping mechanism model and transmission ratio changing rate are built by analyzing the mechanical structure and the gearshift mechanism,finally the simulation model has been built,the transmission model is performed by analyzing the longitudinal dynamics,combing with the driver model the backward simulation model is built;(3)Analyses the insufficient perfomence on the drivability of the electric vehicle under the primary control strategy,in the starting condition,normal acceleration condition and the high speed acceleration condition,the calibration method of the acceleration pedal is studied,a new settlement is achieved to solve the long acceleration response time under low SOC issue;according to the jerk phenomenon of the starting condition and the driving mode switching phase,the new method to add the starting mode and compensation mode is proposed,analysis the driving intention of the driver,introduces the acceleration pedal rate as the parameter as the driver intention recognition,the fuzzy control strategy is proposed to specify the actual driving intention,the different fuzzy control rule is made based on the different SOC;the mechanism of the influence of the ratio changing rate is studied,as well as the relationship between the acceleration pedal changing rate with the ratio changing rate,the optimized strategy is proposed;totally analysis the connectionbetween the PID controller and the actual ratio changing speed,the method to use different PID controller in the different driving mode is achieved,finally the contrast simulation of continuous acceleration between primary and new control strategy is performed.(4)Analyses the insufficient performence on the drivability under the primary control strategy of regenerative braking intervention condition and the exiting condition,the reason of shock in the regenerative braking intervention condition is studied,the solution is proposed,analyses the reason of shock in the regenerative braking exit condition,the relation between the braking declaration and the velocity of the car is studied,a new strategy is performed;relationship between the regenerative power has been researched,the ratio changing rate,the velocity and the new ratio regulation strategy against the braking condition is achieved;the contrast simulation of acceleration-braking condition between primary and new control strategy is performed;analyses the two kind of urban driving condition with and without the brake pedal participating,the insufficient reason on drivability in these situation is studied,the method is proposed,finally,the contrast simulation of the urban driving condition between primary and new control strategy is performed.