Pneumatic Regulating Module Of Regenerative Braking System In Electric Bus

With the rising in vehicle ownership,energy crisis and environmental pollution is becoming increasingly serious and the development of new energy vehicles is imperative.The regenerative braking system,as an important energy-saving technology,can effectively improve the energy economy of the electric vehicle,which is of great significance for relieving energy crisis and environmental pressure.However,the introduction of the regenerative braking force makes the friction braking force to adjust according to the intervention degree of the motor regenerative braking force in real time.The friction braking force is not only determined by the brake pedal,but also affected by the battery status and motor load.In order to meet the demand of the total braking force,requiring the pneumatic regulating module to control the friction braking force more precisely and quickly.The pneumatic regulating module of regenerative braking system of electric vehicle were investigated from the regenerative braking system program,control strategy,precise control methods of friction braking force by means of simulation and hard-ware-in-loop(HIL)test in this paper.Based on the pneumatic ABS system,the regenerative braking system scheme based on solenoid valve and proportional valve was designed.For the solenoid valve,which was widely used for ABS/ESP,an electro-magneticmechanical-pneumatic coupling dynamic model was built through the analysis of its structure and working principle.A logic threshold control algorithm was proposed and the effectiveness was verified.But the solenoid valve is controlled discontinuously with long response time as well as frequent pressure fluctuation,which makes it unable to realize accurate control,so consider using proportional valve instead of solenoid valve to adjust the friction braking force.For the proportional relay valve,a nonlinear mathematical model was established and the hysteresis curve and pressure response time are obtained by analyzing the hysteresis and pressure response characteristics.A PID controller with feed forward and anti-windup compensation was designed and verified by experiment.HIL test was processed to compare the control effect of solenoid valve and proportional valve from the aspects of pressure fluctuation,braking smoothness,regenerative braking efficiency,the speed-following effect and the economic contribution rate of regenerative braking.The ABS control effect of solenoid valve and proportional valve in the emergency braking state was analyzed and compared from the aspects of slip ratio,braking distance and so on.The test results show that the proportional valve has more advantages in application of regenerative brake systems.