Study On Fuzzy Control Strategy For A Plug-in Parallel Hybrid Electric Vehicle

The predictive control strategy of hybrid vehicles achieves the optimal distributionof the engine and motor torque with the further driving condition information of vehicle.The vehicle fuel consumption and emission are determined by the predictive control. Inthis thesis, the fuzzy control strategy for a plug-in hybrid electric vehicle in generalcondition and transient condition is studied, with the reference to the law of state ofcharge (SOC) variation that obtained from the global optimization control strategy, andthe aim of the minimization of the vehicle fuel consumption and emissions. The mainstudies achieved are as follows.①The mathematical model of the powertrain components of the plug-In hybridelectric Vehicle (PHEV) and vehicle driving equation are established, and the fueleconomy simulation model of a plug-in parallel hybrid electric vehicle is built based onthe spatial domain.②The fuzzy control strategy of general condition is studied. The fuzzy controlstrategy in the general condition is proposed, and the theory SOC reference trajectory asthe SOC target trajectory. The inputs of the fuzzy controller are the ratio of the demandtorque and the maximum engine torque at the current speed, the current SOC and thedifference between the current SOC and the corresponding value on the SOC referencetrajectory, and the output is the ratio of the engine output torque and the maximumengine torque. The simulation showed that under multi-NEDC cycles, the fuzzy controlstrategy can make the curve of battery SOC close to the effect of global optimizationcontrol. Under the trip for9NEDC cycles, the fuel consumption with fuzzy controlstrategy increase by10.48%compared to the global optimization strategy.③The situation that the vehicle actual trip is different from the planning trip isstudied. The simulation showed that the fuel consumption increase as the increase of thedifference between actual trip and planning trip. If the planning trip can be changed tothe actual trip and the SOC reference trajectory is corrected in time, influence of theinaccurate the planning trip to the fuel consumption can be reduced effectively.④The predictive control strategy based on the fuzzy control theory is studied inthe transient conditions. The fuzzy predictive controller is built, combining the torquedemand of vehicle and the requirements of charging and discharging in the specialcondition of the further driving route. The inputs of the fuzzy predictive controller are the ratio of the demand torque and the maximum engine torque at the current speed, thecurrent SOC and the SOC various amounts in the future special condition. The fuelconsumption simulation is carried out in the transient and special conditions whichinclude such as the future special conditions being uniform downhill condition andtraffic jam, and the validity of the predictive control strategy in the transient conditionsis verified.