FlexRay总线静态段消息重传调度策略

Message Retransmission Scheduling Strategy on Static Segments of FlexRay Bus

FlexRay总线协议具有较强的错误检测机制,但缺少相应的重传机制,对于功能安全需求较高的应用,通信系统难以达到相应的安全等级要求。为此,提出一种静态段消息重传调度策略。该策略以满足全局可靠性目标为前提,减小静态段报文重传对带宽的占用,建立消息重传次数最优化数学模型,对所有消息通过消息传输总延迟时间最小化为目的建立混合整数线性规划数学模型来分配相应的发送时隙及周期。运用建模语言AMPl及相关求解器对上述2个数学模型进行编程求解,并将消息重传调度策略应用于汽车线控系统。实验结果表明,该调度策略在使通信系统满足相应功能汽车安全需求等级的前提下,提高FlexRay总线带宽利用率和消息调度的成功率,同时实现各消息发送时延最小化。

Although the FlexRay bus protocol has a strong error detection mechanism,there is no corresponding retransmission mechanism.For applications with high functional safety requirements,it may be hard for the communication system to achieve the corresponding security level.Therefore,this paper propose a message retransmission scheduling strategy on static segment.In order to meet the global reliability goal and reduce the bandwidth occupancy of static segment message retransmission,this paper establishes a mathematical model to get the optimal number of message retransmissions,and establisnes a Mixed Integer Linear Programming(MILP) mathematical model to allocate the corresponding transmission timeslot and cycle for all messages to minimize the total delay time.The above two mathematical models are programmed and solved by the modeling language AMPl and the relevant solver,and the message retransmission scheduling strategy is applied to the automobile X-by-wire system.Experimental results show that in the premise that the communication system achieves the corresponding Automotive Safety Integrity Level(ASIL) the scheduling strategy improves FlexRay bus bandwidth utilization and the success rate of message scheduling,and realizes the minimization of the transmission delay of each message.