| In recent years,with the increase in global vehicle ownership,the problem of environmental pollution caused by vehicle exhaust emissions has attracted increasing attention of Governments,along with traditional cars cost a lot of petrol,causing the depletion of oil and energy,therefore,hybrid electric vehicles(HEVS)came into being as the representation of the new energy vehicles.Hybrid electric vehicles' driving range is long,and it is equipped with two operating modes :pure electric driving mode and regenerative braking mode,the situation of oil consumption and emissions compared to conventional fuel vehicles can be obviously improved.As one kind of energy recycling method,regenerative braking system(energy recovery braking)in the HEV attracts the attention of domestic and foreign Auto companies.When the vehicle is braking,the motor coupling with the engine will become a generator to generate electric power as well as supply partial braking forces.Eventually,electric power is stored into the battery pack through the electrical power train system which could increase the EV mode endurance and has an impressive impact on fuel consumption and emission of HEV.Electromechanical control continuously variable transmission(EMCVT)can achieve the true sense of the stepless automatic transmission as the same as traditional continuously variable transmission(CVT),they both have outstanding advantages in terms of adjustment of the power source work area,the difference of the both is that the EMCVT take a electromechanical speed drive mechanism to achieve axial movement of the drive pulley which is consist of electric motor ?gear reducer and screw nut mechanism,abandoning the traditional hydraulic system completely,this approach reduces the manufacturing cost of the system,and improve the system reliability.When the car is in braking condition,the system can maximize the recovery of braking energy by adjusting the CVT ratio and the motor speed to make the motor work in the optimized working curve,which is derived from the basement of the motor / battery joint efficiency model.This paper studies on the PHEV equipped with EMCVT,including hybrid electric vehicle regenerative braking system theoretical analysis and simulation,we have obtained the following results:1.Based on analysis of the brake dynamics of traditional fuel vehicles,and brake force distribution with reference to conventional cars,combining EMCVT continuously variablecharacteristics,a braking force distribution ratio based control strategy of hybrid electric vehicle being proposed.2.Based on the analysis of battery charging efficiency,the motor generating optimal working line while braking is drawn,CVT ratio and control strategy is given to make the motor working in high efficiency working zone while generating;considering the effect of SOC on the battery charging efficiency,the CVT ratio changing surface chart under diverse SOC is drawn.3.Established of a hybrid electric vehicle regenerative braking system mathematical model based on CRUISE simulation platform,according to the configurations and parameters of EMCVT equipped PHEV.4.Proposed regenerative braking system simulation evaluation,taking a simulation analysis in the European NEDC cycle working conditions with different braking initial speed and the battery state of charge(SOC),Under the typical braking situation and the typical city driving cycles(NEDC)simulation,the results shows that the regenerative braking system model built and the CVT ratio control strategy in this paper could satisfy the requirement of normal braking as well as recycling the braking power. |
PDF Full Text Request