Research On Redundant Control Of Electro-Mechanical Braking System Of Commercial Vehicle

While the global automobile industry is transforming and upgrading towards the direction of electrification,intelligence,networking and sharing,the traditional hydraulic and pneumatic braking forms can no longer meet the requirements of new energy vehicles and intelligent networked vehicles for flexible chassis layout,compatible system architecture and integrated control functions.As one of the main development directions of braking system in the future,the brake-by-wire scheme represented by electro-mechanical brake is gradually accepted by people.Therefore,it has become an important topic to utilize the inherent redundancy characteristics of actuators to reduce the safety risks caused by system failures.Based on this,this paper mainly carries out the following research:(1)The construction principle of the electro-mechanical braking system is analyzed,and the overall structure of the simulation model of the electro-mechanical redundant braking system is determined.The controlled vehicle model was set in Trucksim,and the vehicle reference model was built in Simulink to get the ideal value of yaw rate and sideslip angle.The relationship between slip rate and adhesion coefficient was analyzed,and the tire model was established.Finally,the vertical load of each wheel was calculated based on the load transfer caused by braking and steering conditions.(2)Combined with the traditional pneumatic brake structure of commercial vehicles,this paper determines the structure of the electro-mechanical brake executing agency of commercial vehicles,and establishes the overall structure of the electro-mechanical brake execution system.The vector control system simulation model of permanent magnet synchronous motor and the transmission mechanism model are built,and the three closed-loop control system of brake executing agency was established.Finally,based on the Simulink simulation platform,a control prototype of the braking execution system was built to simulate and analyze the clamping force response performance of the brake executing agency,so as to verify the feasibility and effectiveness of the control strategy of the electro-mechanical braking execution system in this paper.(3)The influence of brake executing agency failure on vehicle stability was analyzed,and the vehicle stability control strategy of electro-mechanical redundant braking was formulated.A vehicle stability controller based on yaw rate and sideslip angle was designed to obtain the additional yaw moment required to maintain vehicle stability.According to the vehicle’s requirements for stability and braking efficiency under the conventional and the single-wheel braking failure conditions,the conventional braking force allocation strategy and the redundant braking force allocation strategy based on the difference between the target slip rate and the optimal slip rate were proposed.(4)The control strategy model was built in MATLAB/Simulink and co-simulated with Trucksim to simulate and analyze the vehicle stability control strategy of redundant braking under conventional braking conditions and single-wheel braking failure conditions.It is verified that compared with the conventional braking force allocation strategy,the redundant braking force allocation strategy can better maintain the stability of the vehicle in the emergency braking condition when the single-wheel braking force is lost,so as to improve the safety performance.