Research Of Electric Vehicle Regenerative Braking Control Strategy Based On EHB System

Dissertation Title:Research of Electric Vehicle Regenerative Braking Control Strategy Based on EHB SystemWith the reduction of energy and degradation of environment,'world crisis'saying is everywhere,electric vehicle can resolve the global energy and environmental crisises.Due to the limitation of current battery technology,the driving range of electric vehicle is too short.Based on the existing structures and components of electric vehicle,regenerative braking can generate braking torque and electricity at the same time, recover part of the braking energy while braking,which make up of the defect of electric vehicle drving range,maximize electric vehicle's energy-saving advantage and social benefits.The electro-hydraulic braking system is an intermediate product between traditional braking system and braking-by-wire.Achieving regenerative braking of electric vehicle based on EHB not only maximize the energy recovery rate,but also improve the braking performance.The combination of electric vehicle, electric hydraulic braking and regenerative braking is the development trend in the future and must be the best combination.This article is one part of'Electric vehicle development' project which cooperated by Jinzhou Wande Group and Jilin University,main work is developing regenerative braking control strategy for electric vehicle based on electric hydraulic braking system,simulating and analysing vehicle performance and braking performance,providing theoretical basis and control algorithm for building test bench and vehicle testing.Main research contents are as follows.(1) Electric vehicle modeling and performance simulating based on EHB system.Built 15th degree of freedom forward electric vehicle model based on Simulink, including the driver,electric motor,battery,EHB system model,and compared vehicle model with Advisor's,analyzed their accelerated and decelerated performance,validated its veracity.Each component module and the parameters selected included in the EHB system model, then compared with EHB system modeled in AMESim, analysed the pressurized and vacuum process of wheel cylinder,met the basic pressure adjusted request and rapid pressure response of wheel cylinder.Developed braking control model,coordinated the electric braking force and hydraulic braking force.Calculated the maximize regenerative braking torque based on the current state of motor,battery and vehicle,at the same time judged the braking force the driver need according to the braking pedal displacement,ultimately got the needed values of regenerative braking torque and friction barking force.The motor generated the electric braking torque as need at the same time of generating electricity, charging up the batteries through converter.Achieved the friction torque by controling the winding current of inlet and outlet solenoid valves of EHB hydraulic control unit.Satisfied the driver's braking demand through combining the two torques.(2) Researched the regenerative braking force distribution strategy.Based on the classical front and rear axle braking force distribution methods,developed an algorithm called braking force distribution method based on ECE regulation, controlled regenerative braking force with Fuzzy logic controller,ensured the maximized of braking energy recovery,assured the braking security and the allowed of each component state.(3) Simulated the electric vehicle regenerative braking performance based on EHB system.Choosed the evaluation indexes for electric vehicle braking performance,simulated the front-wheel drive electric vehicle and four wheel drive electric vehicle respectively in typical normal braking conditions and typical urban cycling conditions,with different battery SOC and road adhesion coefficients,compared their braking performance.The analysis results showed that for electric vehicle used in urban condition, the braking force distribution algorithm based on ECE regulation not only satisfied the ECE regulation requirement,but also the braking energy recovery rate was higher than other methods.Normally,people think that the four wheel drive vehicle should use more energy,but the simulated results showed that four wheel drive electric vehicle used almost the same energy with front wheel drive electric vehicle,the braking energy recovery rate was also equivalent. Innovations of this paper are as follows:(1) Proposed the electric vehicle regenerative braking control strategy based on EHB system the first time.(2) Compared and analyzed the basic barking performance and regenerative braking performance of two-wheel drive and four-wheel drive electric vehicle.(3) Developed a new braking force distribution method of front and rear axle, which increased the braking energy recovery rate.The research results of this paper provided theoretical basis for electric vehicle drive and brake type, and control strategy for developing regenerative braking system.