Electro-mechanical Braking Force Distribution And Stability Control Strategies For HEV

Regeneration during braking is an important technique for hybridelectric vehicles to improve their fuel economy and extend their drivingrange. During braking course, the electric motor acts as generator, theregenerative kinetic energy of vehicle stores in battery as electrical energyfor future use. Energy regeneration is a wide used technique for enhancethe fuel economy.Different from the traditional vehicle, electric motor adds theregenerative braking torque to the power line during deceleration.Therefore, hybrid electric vehicle has two different braking torques, oneis regenerative braking torque which is offered by electric motor; theother is hydraulic braking torque which is provided by hydraulic brakingsystem. Based on conventional passenger vehicle’s braking theory, thebraking theory of hybrid electric vehicle’s electro-mechanical hybridbraking system should to be added new researched and analyzed content.Based on the financially supported national project of HEVindustrialization, the electro-mechanical hybrid braking force distributionand stability control strategies were researched according to the R&Dflow of system, as following.First, considering the needs of theory research and system analysis, adynamic model for HEV electro-mechanical hybrid braking system hasbeen built up as one important part of design of braking system controlstrategy, it has strong influence on the efficiency and effectiveness ofdeveloped controller. The vehicle system dynamic model main consists ofvehicle dynamic model, tire model, hydraulic system model, electricmotor model, battery model. The modeling course using theoreticalmodeling approach combined with empirical modeling. This dissertationmake a deep insight into the tire model, hydraulic system model andmotor model in order to get the needed model calculation parameters,design the experiments schedule and make the related experiments.Second, HEV electro-mechanical hybrid braking force distribution control strategies were researched. Because the braking force distributionto the front and rear axles has great influence on the braking stability andsafety, based on the research of HEV electro-mechanical hybrid brakingstability control system and hydraulic braking force distribution to thefront and rear axles, the control equation of braking force distributioncoefficient was built and its braking force distribution curves were alsodescribed. Meanwhile, available adhesion coefficient, braking efficiencyand other braking characteristics of HEV hydraulic braking wereanalyzed. And, the electro-mechanical braking force distribution controlstrategies were presented. The braking force distribution simulationresults show that the control strategies are feasible and effective.Third, HEV electro-mechanical hybrid braking stability controlstrategies were researched. Many influential factors to regenerativebraking torque, such as motor characters of generating electricity, batterysafty and its charging characters were analyzed. Based on analysis of theinfluential factors to regenerative braking torque, the electro-mechanicalhybrid antilock braking control strategies were researched, which werethe extension of electro-mechanical hybrid braking force distributioncontrol strategies. The idea that motor intervention control was springedbefore antilock braking is triggered was presented. Meanwhile, the motorregenerative braking control method which aims at offseting the hydraulicbraking hysteresis was presented. Based on feed forward compensationand fuzzy logic control, using yaw rate and slid slip angle as the statefeedback, the lateral braking stability were presented. Simulation resultsshow that the braking stability control strategies are feasible andeffective.Lastly, real vehicle test for braking control system was executed.Through the software and hardware design of real vehicle braking controlsystem and real vehicle test, the control strategies were analyzed. Theresults from experiment show that harmonious coordination betweenregenerative and hydraulic braking function, braking safty and stability ofthe vehicle is good, a amount of braking energy can be recovered and theproposed control strategy and method are effective.As one of the key techniques, braking control strategies play theimportant roles in the development of HEV with domestic independentintellectual property, and it is significant to propel the industrialization ofHEV.