AFDX实时流量的时间确定性中间件接入模型研究

Time Deterministic Middleware Model for AFDX Real-Time Flow

为保证COTS平台下的航空电子应用在航空电子全双工以太网(AFDX)上的时间确定性接入,设计了AFDX网络实时流量的中间件接入模型。通过基于中间层驱动过滤机制的协议转换,实现了双边网络的协议对接,并给出了帧顺序号(SN)的插入方法;通过对虚拟链路(VL)在时间上进行有效分配,避免了速率受限的数据流对物理链路的争用,在实现单条VL的BAG整形基础上提出了使实时流量抖动最小的VL复合时间调度算法。搭建典型实验环境对该模型进行仿真实验,结果表明,中间件模型能准确地实现数据帧TCP/IP协议与AFDX协议格式的相互转换,且该时间调度算法大大减小了VL复合所产生的抖动,保证了数据流传输的时间确定性。

To ensure the time determinability of avionics applications based on Commercial-off-the-shelf （COTS） platform when accessing into AFDX （Avionics Full Duplex switched ethemet） network, an AFDX real- time flow middleware was designed. Using protocol conversion function based on filtering mechanism of intermediate driver, the middleware achieved communications between networks nmning with different protocol. Core code of frame sequence number （SN） insertion was described. A time scheduling algorithm which has the minimum jitter aimed at VL-Multiplexing was proposed, by distributing the sending-time of visual links（VL）, it is able to avoid contention on a rate limited physical link. Finally, experiments were made to test the performance of AFDX real-time flow middieware and the results showed that：the middieware model achieved the format mutual conversion between TCP/IP protocol and AFDX protocol, and the time scheduling algorithm can decrease jitter caused by VL multiplex apparently, which ensured the time determinability of AFDX communication.