Page - 282 - in Emerging Technologies for Electric and Hybrid Vehicles

energies Article OptimizationofKeyParametersofEnergy ManagementStrategyforHybridElectricVehicle UsingDIRECTAlgorithm JingxianHao1,2,ZhuopingYu1,ZhiguoZhao1,*,PeihongShen1 andXiaowenZhan1 1 SchoolofAutomotiveStudies,TongjiUniversity,Shanghai201804,China;haojingxian@saicmotor.com(J.H.); yuzhuoping@tongji.edu.cn(Z.Y.); shenpeihong@tongji.edu.cn(P.S.); xiaowenzhan1@163.com(X.Z.) 2 SAICMotorCommercialVehicleTechnicalCenter,Shanghai200438,China * Correspondence: zhiguozhao@tongji.edu.cn;Tel.:+86-21-6958-9117 AcademicEditors:MichaelGerardPechtandChunhuaLiu Received: 22August2016;Accepted: 22November2016;Published: 26November2016 Abstract: The rule-based logic threshold control strategy has been frequently used in energy management strategies forhybrid electric vehicles (HEVs) owing to its convenience in adjusting parameters, real-timeperformance, stability,androbustness.However, the logic thresholdcontrol parameters cannot usually ensure the best vehicle performance at different driving cycles and conditions. For this reason, theoptimizationof keyparameters is important to improve the fuel economy,dynamicperformance, anddrivability. Inprinciple, this is amultiparameternonlinear optimizationproblem.The logic thresholdenergymanagementstrategyforanall-wheel-driveHEV iscomprehensivelyanalyzedanddeveloped in this study. Sevenkeyparameters tobeoptimized are extracted. The optimizationmodel of key parameters is proposed from the perspective of fuel economy. The global optimizationmethod, DIRECT algorithm, which has good real-time performance, lowcomputationalburden, rapidconvergence, is selected tooptimize theextracted keyparametersglobally. Theresults showthatwith theoptimizedparameters, theengineoperates moreat thehighefficiencyrangeresulting intoa fuel savingsof7%comparedwithnon-optimized parameters. Theproposedmethodcanprovideguidance forcalibrating theparametersof thevehicle energymanagementstrategyfromtheperspectiveof fueleconomy. Keywords: fueleconomy;hybridelectricvehicle;energymanagementstrategy; logic thresholdvalue; DIRECT;parametersoptimization 1. Introduction Themainfactorsaffectingthe fuelconsumptionandemissionperformanceofahybridelectric vehicle (HEV) include theperformanceparametersofvariouspowertraincomponentsandvehicle control strategyparameters.Optimizingtheparametersof thepowertrainandcontrol strategywill notonlyresult inareasonablematchfor thepowertrain,butalsoreduce thevehicle fuel consumption andemissions. Atthisstage, theenergymanagementstrategybasedonlogic threshold ismainlyusedinHEVs[1,2]. The focus is topredetermineanumberof thresholdparameters thatmaketheengineandbatterywork in thehighefficiencyarea. Thebattery charginganddischargingefficiencyare also considered in order toproperlydistribute thedriver’s requiredtorqueto theengineandmotor, therebyattaininga goodvehicle fueleconomyandemissionperformance. Invehicle tests, thepredefinedparametervaluesof the logic thresholdcontrolstrategyareusually obtained by trial and error based on engineering experience. Thismethod requires considerable debugging time to acquire satisfactory results both in simulationandvehicle transfer hub test for Energies 2016,9, 997;doi:10.3390/en9120997 www.mdpi.com/journal/energies282