Research On The Control Strategy Of Regenerative Braking System In Hybrid Electric Vehicle Based On Compound-Structure Machine

In order to cope with the problem of energy shortage and environmental pollution,new energy vehicles have gradually become an attractive issue in the automotive industry with the advantages of being economical in energy and environmental-friendly.At present,Hybrid vehicles is the most feasible new energy vehicle solution.Hybrid vehicles need a power coupling structure to coordinate the power distribution between the engine and the electric motor.Toyota introduced the first-generation Prius planetary gear power unit and applied for patent protection in 1997.Compound structure motor(CSM)is a new type of electromagnetic stepless speed change device,which has broad application prospects in occasions requiring electromechanical energy conversion such as hybrid vehicles,wind power generation,and underwater propulsion.The application of composite structure motors to hybrid vehicles can realize the function of Toyota Prius’ power transmission structure,which is conducive to breaking its patent protection in the field of hybrid vehicles and promoting the development of domestic hybrid vehicle research.This paper takes the regenerative braking system in Hybrid Electric Vehicle based on Compound-Structure Machine(CSM＿HEV)as the research object,takes full advantage of the flexible energy conversion method of composite structure motors and proposes new types of regeneration braking mode in CSM＿HEV.Then the issues on the new braking mode switching and braking force distribution algorithm,the coordinated control of regenerative braking system and ABS system,and the comfort of braking dynamic process is researched.The researches in this paper provides a new theoretical basis to apply the CSM into practical using and is of great significance for enriching the energy management strategies of hybrid vehicles.This paper first establishes mathematical models of different driving modes in CSM＿HEV,and analyzes the dynamic relationship and power flow of each component of CSM＿HEV.Then the output parameters of the vehicle’s power system is matched according to the driving dynamics requirements.Finally,the power parameters of CSM is allocated using the engine parameters of the Toyota Prius as a reference.This part of research provides a theoretical basis for subsequent regenerative braking research.Then this paper analyzes the dynamic coupling mode of the composite structure motor in the power transmission topology,and establishes the expression of the dynamic coupling relationship between the composite structure motor and the engine output speed and torque and the brake demand is analyzed.Different braking modes,including two new braking modes of Engine-motor coordinating braking(EMB)and Dual-motor braking(DMB)is proposed,of which EMCB mode can make the engine operating in the optimal state under braking conditions,reduces the frequency of engine state switching,improves the fuel economy and DMB mode can make full use of CSM’s regenerative braking force to improve the energy efficiency.Aiming at the problem of new brake mode switching and braking force distribution,this paper proposes a hierarchical controller.The upper controller is a rule-based mode switching control strategy to select the four braking modes.The lower controller is a braking force distribution strategy based on neural network.The controller can realize the mode switching under three typical working conditions of NEDC,Ftp72 and Highway,and achieve efficient braking force distribution under different control modes.Aiming at the problem of coordinated control of regenerative braking and ABS system,this paper proposes a coordinated control strategy of regenerative braking and ABS system based on Model Predictive Control(MPC).The MPC controller allocates the braking force to CSM with the optimization goals of braking safety and the efficiency of CSM.The car can follow the target slip rate and ensure the efficient operation of CSM when applying the proposed control strategy.Aiming at the problem of braking comfort in the dynamic barking process,this paper improves the general control strategy of CSM,and output torque control of CSM and output torque control strategy based on feedback of shock degree are proposed to reduce the new system.The braking shock degree in the braking process and the mode switching process of the new braking mode can meet the requirements for braking comfort with the new control strategy.