The Research On Steering-by-Wire System Based On FlexRay Bus

Vehicle steering system is the key assembly impact on the active safety of vehicles and vehicle handling and stability. As the next new generation steering system, Steering-by-Wire System removed the mechanical connection between the steering wheel and front wheel, it is a power steering system entirely by the control signal of electronic control unit to control vehicle steering. We can design the angle transmission and force transmission of steering system freely based on different circumstances. According to the requirements of steering by wire system and combine the high speed, deterministic, fault-tolerant, flexibility features of FlexRay bus, we use FlexRay bus to communicate in steering-by-wire system; it can satisfy the real-time and reliability requirements of steering system.The paper has finished the design of the steering-by-wire system based on FlexRay bus communication. Firstly, this paper reviewed the automobile steering system development process, summarized the principle and structure characteristics of the steering-by-wire system. Then researched on the FlexRay bus protocol based on time triggered, determined the FlexRay network topology in steering-by-wire system. Then completed the design scheme of steering-by-wire experimental table, specific analyzed the system based on the modules function and requirement, determined the selection and configuration of steering-by-wire experimental table components, completed install the whole steering-by-wire experimental table, provided the hardware foundation for the following system development. Then analyzed the function structure of steering–by-wire system, built steering control module node and steering executive module node, this two modules use FlexRay dual channel bus to communicate. It has completed node design of hardware and software based on MC9S12XF512 and TJA1080 bus driver. The steering control module and steering executive module establish contact through transmission ratio, established the dynamic model of steering-by-wire system, Analyzed the steering system's aligning torque, determined the steering-by-wire system ideal transmission based on the vehicle system yaw velocity gain and the lateral acceleration gain for setting value method, and researched the steering executive motor's control strategy according ideal transmission.FlexRay network use double channels to communicate in steering-by-wire system, this two channels transmit the same data realize the redundancy backup; it can meet the system's fault-tolerant functional requirements.