FlexRay时钟同步的同向漂移

Clock Drift in FlexRay

介绍了FlexRay时钟同步的方法,发现由于延迟补偿不足或过头以及算法临界稳定特征根的存在,虽然节点间的偏差可以消除,但是它们将同向漂移,与节点内host的时钟发生偏离。普通帧因通信时钟比host变慢而丢帧;host与通信时钟同向漂移时帧就绪推迟,也会造成消息丢帧,从而产生到达顺序的混乱,影响其确定性与可靠性。

After briefing the synchronization method of FlexRay, the paper discovers a problem. Due to uncompensated error in propagation delay and the existence of critical characteristic root in transfer matrix of algorithm, there is a tendency that the clocks drift in one direction though they are synchronized. The drift with respect to the host clock makes the frame being overwritten before its sending; hence some frame will be lost. The host drift with respect to communication clock makes frame not ready;hence frame will be lost. Frame lost or the order change in message delivery causes determinativeness Ioss and reliability problems.