Pressure Coordinated Control Of Electro-hydraulic Braking System In Four-wheel Drive Plug-in Hybrid Electric Vehicle

With the increasing depletion of oil resources and national laws and regulations impose stricter requirements on vehicle emissions,various auto manufacturers have turned their attention to new energy vehicles.However,it is difficult to achieve large-scale promotion of pure electric vehicles in the short-term due to the difficulties in achieving breakthroughs in short-term battery technology,short mileage,and high cost of pure electric vehicle.The hybrid vehicle is a transitional product of traditional fuel vehicles to pure electric vehicles,it has the advantages of energy conservation,emission reduction,long mileage,and strong dynamics.It has received increasing attention and will dominate for a long time.As a key technology for energy-saving and emission-reduction of hybrid vehicles,regenerative braking can recover braking energy during braking,thus achieving energy conservation and emission reduction.It is of great significance to improving the mileage of hybrid vehicles.The hybrid regenerative braking system includes a motor braking system and a hydraulic braking system.The technical difficulty lies in the coordinated control of the motor braking force and the hydraulic braking force in the braking process.Therefore,designing a set of reasonable and effective electro-hydraulic braking system and corresponding control strategy to ensure efficient energy recovery under the premise of safe and reliable braking and braking stability has important practical significance.In this paper,front the rear axle dual-motor drive CVT hybrid vehicle as the research object,in order to ensure good braking performance and good energy recovery effect,designed a set of electro-hydraulic composite braking system and corresponding control strategy,and carried out theoretical analysis,key parameter optimization,system integration modeling,co-simulation and performance evaluation.Through the above work,provide reference for further research on electro-hydraulic composite braking systems.The main work of this paper is as follows:(1)Through the analysis of the traditional ABS working principle,and based on the characteristics of the studied vehicle models,improving the traditional ABS system and an electro-hydraulic braking system structure with traditional braking mode and regenerative braking mode based on ABS hardware is proposed;(2)The structural design and parameter matching of the key components of the hydraulic part of the regenerative braking system(vacuum booster,stroke simulator,high-speed on-off valve,etc.)were performed,and the system dynamic performance simulation were performed.(3)Based on the analysis of vehicle braking dynamics and based on relevant braking regulations,the brake mode discrimination logic,motor braking force and hydraulic braking force distribution strategy and ABS control algorithm suitable for regenerative braking system are designed.(4)Based on the AMESim-Simulink co-simulation technology,the motor model,battery model,CVT model,wheel model,hydraulic brake system model and vehicle 15 degree of freedom model were established on the AMESim platform.Braking mode discrimination model,braking force distribution model,CVT control model and ABS system control model was established on the Simulink platform,completed the construction of a co-simulation platform based on the vehicle-based electro-hydraulic braking system model.(5)Based on the co-simulation platform,a preliminary off-line simulation analysis of the brake performance of the electro-hydraulic braking system under various typical braking conditions and cycle conditions was performed.The simulation results show that the system can meet all braking conditions and efficient energy recovery is achieved on the premise of braking safety and braking smoothness.Based on the theoretical analysis of the electrohydraulic braking system,this paper proposes the structural scheme and control strategy of the electro-hydraulic braking system based on ABS hardware.The feasibility and reliability of the system are verified by theoretical simulation and provides reference for further study of electro-hydraulic composite braking system.