CVT Speed-ratio Matching And Control Strategy Based On PHEV

The CVT speed-ratio matching,economy performance,emergency accelerationperformance of a plug-in hybrid electric vehicle(PHEV) are researched. The PHEV usesa CVT.Optimal operation conditions are analyzed in different driving modes of the PHEVto improve the economy performance. Optimal economic conditions of the constantpower curve are used as the optimal operation condition in the pure engine drive modeand pure electric drive mode. The CVT ratio matching is related with the energymanagement strategy in the hybrid drive mode and charge drive mode. Objectiveoperation conditions of the engine and motor are analyzed to obtain the highestefficiency of the power system. The CVT target ratio in different driving modes arecalculated based on the optimal operation conditions and the velocity of the PHEV.A backward simulation model is established on the Simulink/Stateflow platform tovalidate the rationality of the CVT ratio. The economy performance of the PHEV issimulated by using the New European Driving Cycle(NEDC). The CVT target ratio ofthe pure electric drive mode,charge drive mode and the hybrid drive mode arereasonable. The engine and motor work at the target conditions. The energy cost of thePHEV declined compared with the prototype vehicle.The emergency acceleration performance is analyzed when the PHEV operates atthe pure engine drive mode. The mathematical models of the driver’s desired torque andpowertrain are established.The change of the PHEV dynamic performance caused bythe CVT ratio change rate is analyzed. The emergency acceleration performance of thePHEV is poor since the CVT ratio increasing. Therestriction of the CVT ratio changerate and torque compensation by the motor are proposed by considering features of thePHEV to overcome the problem. The compensation torque of the motor is obtainedbased on analyses of factors that influence the CVT ratio change rate. The emergencyacceleration performance of the PHEV is simulated by using the Simulink. Resultsshow that the strategy can improve the acceleration performance of the PHEV.