Study On The Mode Switching Controlling Of Full Hybrid Electric Vehicle Power Transmission System Based On CVT

The gradual deletion of oil resources and environmental pollution have become theglobal problems everyone have to face. For ever-increasing automobile amount andincreasingly stringent vehicle emission regulation, auto industry face a severe challenge,but also a unprecedented opportunity. Pure electric vehicles can not acquire substantialbreakthroughs on several key technical problems like how to have high-capacity andlong lifetime in a short time, fuel cell electrical vehicle also can not get greatdevelopment for some the limitations of its contemporary technology, so hybrid electricvehicle will continue to be the most potential vehicle.The research of the hybrid electric vehicle(HEV) has been paid more attention bycar manufacturers since the problem of energy and environment pollution, as well as theencouragement of the policy. However,many research institutes and manufacturersemphasized their study on the energy management strategy of the HEV, they seldompaid attention to the control strategy during the driving-mode-switch process. Manydriving mode can be achieved by the full hybrid electric vehicle. It is seldom that thedrive torque will be steady during the driving-mode-switch process since the responsetime of the engine and the motor to the torque requirement is different apparently. Thetorque surge would bring impacting to the drivetrain, influence the vehicle ride comfort.It is very necessary to study the control of the drive torque during thedriving-mode-switch process of the HEV.This paper studied the full hybrid electric vehicle with metal belt continuouslyvariable transmission. It is a parallel torque-coupling plug-in hybrid electric vehicle.The vehicle may face mode-switching processes in traveling, these process may havemany different state, such as starting the engine with ISG when traveling, stopping theengine, clutch engagement process, motor joining to work, ISG switching from motorstate to generator state, and so on. To have high mode-switching quality, all these stateneed to get related parts been reasonable controlled. In this paper, the following workswere done:①At first, this paper introduced thestructure and the system parameters of this fullhybrid electric vehicle, gave an analysis of the running modes and built a kineticmodel of this vehicle power transmission system.After having analyzed the dynamiccharacteristic of the components, it built the models of key components by Matlab/simulink soft, including an engine dynamic torque output model, a batterymodel, a CVT model, a motor dynamic torque output model, a clutch model and avehicle longitudinal dynamic model.②Then it recognized the needed torque of the full hybrid electric vehicle withCVT, divided the operation model region of vehicle，set the operating condition, targettorque of engine and motor and the speed ratio control strategy of CVT in each mode.③After setting mode switching condition, the paper analyzed the evaluationcriteria of the mode switching processes, designed the control strategy about the clutchengagement process, both the motor and engine when engine stopping and the motor,engine, clutch when car switched from ISG driving mode to engine driving mode. Italso set the coordinated torque control method and its ending condition of other modeswitching process.④When had built the control simulation model of the full hybrid electric vehiclebased on Matlab/Simulink/Stateflow, the paper specially simulated and analyzed thetypical mode-switching process, such as switching from ISG driving mode to enginedriving mode. Then the bench test of full hybrid electric vehicle power transmissionsystem was developed. The result of simulation and bench test both show the validity ofthe coordinated torque control strategy.