| New energy vehicle is one of the ten key areas of “Made in China 2025". Especially, the pure electric vehicle is a new type of vehicle, which is driven by clean energy and takes the control system as the core. Because of the development of pure electric vehicles, the demand of internal electronic control units(ECUs) is increasing continuously and the auto-control system in vechicles is more and more complex. Meanwhile, people put forward higher requirements for the safety and comfort of vehicle driving. The past active-safety system mainly includes the traditi onal hydraulic braking and anti-lock braking system. They all have been used in vehicles widely, but in theory did not reach the best braking effect. Using X-by-wire technology to establish the electronic control system can improve the automotive safety performance and reliability greatly, and it will bring fundamental change for pure electric vehicles in braking performance. Based on the above facts, traditional in-vehicle network has many problems such as lack of bandwidth, slow communication rate, poor fault tolerance. It can not meet the stringent driving requirement increasingly. FlexRay is a new in-vehicle network in recent years, which has the characteristics of high bandwidth, high transmission rate and d ual redundant fault tolerance mechanism. It can satisfy the high reliability and high real-time requirements for the X-by-wire system. With broad application prospects, FlexRay can provide more development space for automotive electronic technology and pur e electric vehicle.This paper firstly expounds the effect of network bandwidth utilization on the performance of in-vehicle network, and in order to increase the bandwidth utilization, a static parameter optimization model is proposed to improve data transfer rates on the basis of analysis of the FlexRay protocol specification. Three methods are adopted to compared by using multiple sets of examples. The results show that the proposed optimization model can improve the bandwidth utilization significantly.Secondly, the optimization model is applied to the Brake-by-wire(BBW) system. The hardware architecture of the BBW system is set up. The specific functional requirements of BBW system are analyzed. T he parameter of static segment is optimized, then the global parameters and node parameters are designed based on it. The reliability design and analysis are carried out for the BBW communication system using error model to prove the reliability in theory.Thirdly, the simulation model database is designed based on the system communication protocol parameters. The communication model of BBW system is established and simulated by the CANoe.FlexRay simulation software. Then, real node network architecture is established by using FlexRay development boards. Especially, the design of software for the FlexRay node is introduced, including configuration of phase-locked loop(PLL), protocol parameters and message buffer and so on, which ensure the messages could be sent and received correctly.Finally, the communication testing platform of BBW system based on FlexRay is built to evaluate the FlexRay cluster. The communication data of five nodes is displayed by LCD and OLED in real time. Then the FlexRay hardware interface card is connected with simulation software in PC, half and full hardware test are completed to observe that if there any error frames or missing frames. Waveform integrity is analyzed by using oscilloscope and the results show that the network system is as good as the original design. |
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