Research And Analysis On The Control Of Pneumatic Blending Braking System By Wire And Hil Test

With the increase in car ownership,especially the rapid growth of new en ergy vehicles,people increasingly high requirements for new energy vehicles,energy saving,safety and environmental protection,especially the city bus running conditions are complex,resulting in the loss of braking energy,it is of great significance for the development of advanced composite braking system.At present,the braking energy recovery system applied to new energy vehicles is parallel,and the application of the air pressure brake technology by wire for large buses and large trucks is still in its infancy.This subject regard city electric bus as the research object,researching on air pressure braking system by wire,and the braking force distribution is more flexible in order to guarantee safe braking and braking energy recovery more.Based on the pneumatic brake system with parallel dual chamber air brake valve,modifying the air brake valve into a new valve by wire,making the valve as the actuator Pneumatic brake system,pneumatic brake system by wire is designed.The air brake part and the regenerative braking part of the composite braking system are modeled respectively,and their working characteristics are analyzed,then a complete model of the braking system is established.By modeling and analysis,the air pressure in the front and rear axle brake chambers can be flexibly controlled.The friction braking force is well controlled by using the PD control algorithm,which proves the feasibility of the wire brake scheme proposed in this paper.To ensure the safety of automobile braking,the vehicle model and the sliding mode observer algorithm is established,to observe the automobile brake speed,and sliding mode control algorithm is designed with PID,to control vehicle braking speed,avoiding braking wheel lock,losing the direction of s tability,and the simulation results show that the algorithm can accurately observe the speed observation the slip rate control algorithm can control the slip rate in the vicinity of the target slip rate.Based on the slip ratio control algorithm,the composite brake allocation algorithm and the traditional allocation algorithm based on I curve comparison is designed,and simulation results show that the slip rate allocation algorithm can reduce the braking distance and braking based on guarantee slip rate at around the target slip rate,avoid the vehicle lock.Electric vehicle module is modified in ADVISOR software,and the regenerative braking force distribution strategy model and the traditional model of brake distribution is loaded into the software,th e comparative analysis of three kinds of braking energy recovery strategy including software distribution model under different conditions.Finally,the hardware in the loop simulation test scheme is designed,and the x PC double machine control test-bench is built.The braking control unit is designed according to the functional requirements and test purposes of the system,and the necessary experimental information collection and the accurate control of the braking pressure are realized.In the custom condition on the test rig by wire brake systems and brake force distribution strategy designed in this paper is verified by using the vehicle model with three degrees of freedom,the test results show that the system can work well,and achieve the braking energy recovery.