Research On Energy Recovery Strategies In Regenerative Braking Process Of HEV

Development of the new energy automobile industry is becoming an importantmeasure that can accelerate the transformation of transportation energy all over theworld especially in those automobile industrial powerhouses gradually since the21stcentury. Hybrid electric vehicle will be in the long-standing ranks of new energyvehicles because of its lower fuel consumption, lower emission and higher costperformance. Research on hybrid electric vehicle design and control is becomingmore and more widely nowadays. In this thesis, regenerative braking forcedistribution method and braking energy recovery efficiency promoting strategy isdeeply research based on research of HEV regenerative problems.First of all, braking process in traditional fuel vehicles is discussed; basic dynamictheory of braking process and basic theory of braking stability are analyzed. On basisof the above, performance of HEV motors in reverse connection working conditionis discussed. And then, braking stability of hybrid electric vehicles is analyzed.Besides performance of the motor in HEVs, performance of HEV energy storagesystems is simply discussed, especially a model of lithium iron phosphate batterythat is easy to simulate is given in this thesis.Next, common methods that have already been used in HEV regenerative brakingcontrol are discussed, especially the logic threshold control method based onexperience and fuzzy logic control in intelligent system method are mainlyintroduced. Combined with the understanding of the regenerative braking process ofHEVs, basic idea of dynamic programming is used to solve the problem; theregenerative process is divided into many sub-processes. During each sub-process,feed-back control idea is used, distribution ratio of braking force between front andrear axles, distribution ratio of mechanical braking force and regenerative brakingforce on front axle are adjusted real-time to ensure that braking energy recoveryefficiency in each sub-process can reaches the maximum. As a result, efficiencyduring the whole process is maximized. During the feed-back control of eachsub-process, braking stability and braking strength requirement is the primaryconstraint condition real-time.Finally, the proposed regenerative braking control method is experimented andverified in different driving cycles in Advanced Vehicle Simulator Advisor. By comparing energy recovery efficiency and energy recovery effect in different drivingcycles, advantages and disadvantages of the control method used in this thesis iscomprehensively evaluated.