Design And Development Of Electric Vehicle Electro-Hydraulic Hybrid Braking System Based On Test Bench

With the increasingly serious problems of environmental pollution and energy crisis,clean and energy-saving electric vehicles have attracted more and more attention and have become the focus of research and development in countries around the world.The braking system of electric vehicle is a combination of motor braking and mechanical hydraulic braking,which is called Electro-Hydraulic Hybrid Braking System(EHHB).Compared with the traditional braking system,EHHB has more advantages,but it also increases the complexity of the system.How to coordinate the working process between the two braking forces has become a key research topic in today’s electric vehicle braking system.This paper firstly analyzes the braking process of electric vehicles and designs the structure scheme of the electric vehicle electro-hydraulic hybrid braking test bench based on the braking dynamics theory.According to the principle of motor regenerative braking and braking torque,the structure and working principle of high-speed on-off valve,and the adjustment principle of hydraulic braking force,the key components of the test bench are designed,and the components are assembled according to the structure scheme to complete the test bench.The test bench mainly includes motor braking subsystem,hydraulic braking subsystem and power supply subsystem.Then,based on the hardware structure of the test bench,the hydraulic circuit for pressurization,decompression and pressure maintenance is designed,and the braking force distribution strategy is designed by analyzing the characteristics of each typical braking force distribution strategy.This paper designs the control circuit of the test bench based on the STM32 singlechip microcomputer,which mainly includes the upper controller,the drive circuit of the key components and the signal acquisition circuit.The control scheme of the system is designed,and the control program of EHHB is written in Keil u Vision5 in C language according to the control scheme.In order to collect the test data and analyze the test results,this paper uses the single-chip microcomputer as the lower computer,Lab VIEW as the upper computer,and adopts the method of serial communication to develop the data acquisition system of the test bench.In order to verify the performance of the test bench,related tests are carried out on the bench,including hydraulic circuit verification test,follow-up test and compound brake test.The test results show that the actual hydraulic circuit when the test bench is working is consistent with the circuit designed in this paper.The hydraulic brake subsystem built has excellent control performance and can better follow the changes in expected pressure.The work coordination between the motor braking subsystem and the hydraulic braking subsystems is good.The hydraulic braking force can be adjusted with the changes of the motor braking force in real time.The entire bench has good control performance and reaches the design goal.