Research On Dynamic Coordinated Control Strategy Of Single Axis Parallel Hybrid System

Vehicle is one of the most important transportation tools in our modern life,which brings great convenience to people. However, with the increase of vehicleownership, it has brought a huge burden to the energy and environment. Energyshortage and environmental pollution have become a worldwide problem. They havedrawn great attention over the world. As a result, mission regulations have beenissued in many countries, which require the automobile manufacturers to improvethe vehicle’s fuel efficiency and emission. Traditional vehicles have been developedfor a long time, and its technology is quite mature. But for some of its ownlimitations, it’s very difficult task for traditional vehicles to reduce fuel consumptionand emissions further. Under such a background, new energy vehicles arise. The newenergy vehicles use motor completely or partly to replace the driving system withinternal combustion engine. The efficiency is higher and the emission is lower. As atransitional product from traditional cars to new energy vehicles, the hybrid electricvehicle (HEV) has received widespread attention. Lots of research has been done bymain carmakers. Some companies even introduced production models.Because the motor is introduced into the power source, hybrid electric vehiclescan use motor to drive themselves when the engine’s efficiency is low. It ensures thatthe engine works in high efficient area most of the time, so it plays an important rolein promoting energy conservation and emissions reduction. Because of multiplepower supply, the vehicle has a variety of work modes under different conditions.According to different road conditions, the modes switch correspondingly, whichmay cause large vehicle jerk and descends the riding comfort.In this thesis, the vehicle’s jerk when the vehicle modes witch is studied. Thevehicle ride comfort is improved through optimizing control strategy. The “enginetorque open-loop+engine torque identification+motor torque compensation”dynamic coordinated control strategy is proposed on the basis of the energymanagement strategy. Dynamic coordinated control strategy mainly include s twoparts. The first part is the torque management strategy. The other part is the dynamiccoordinated control strategy. Torque management strategy is the basis of the dynamic coordinated control strategy. It decides the time to switch the mode, and according todifferent work modes, the total demanded torque is distributed to the engine andmotor respectively. Dynamic coordinated control strategy controls the distribution ofthe dynamic torque in the process of modes switching to smooth the transient processduring modes switching. For different response characteristics of the engine andmotor, the main control idea is that the engine torque is distributed directly. Becausethe engine torque response is relatively slow, the engine torque value can’t reach thetarget value instantly. The deviation from the target value is compensated by themotor. The instantaneous engine torque can be identified by a torque sensor.Matlab/Simulink software is used to build simulation models and LabVIEW isused as a communication interface between the vehicle controller and Simulink. Thedynamic coordinated control strategy is simulated with hardware-in-the-loop andverified through the bench test. The results show that the proposed dynamiccoordinated control strategy can greatly improve the smoothness of the hybridsystem.