Proposed Method of Loop Detection for Industrial Networks to Prevent Communication Path Changes

The past few decades have seen a large increase in the use of industrial field bus for factory automation (FA). An industrial field bus requires constant searching to synchronize operation and achieve high reliability. This paper focuses on reliability assurance in the presence of unintentional loops. In an industrial network, it is necessary to maintain the network topography in order to keep the transfer delay of the synchronization frames constant. The conventional approaches can detect and eliminate loops, but make no attempt to block ports to maintain the communication path that existed prior to loop formation. Therefore, this paper proposes an effective method to detect a loop and to select a blocking point that avoids the communication path changing. The effectiveness of the proposed method was confirmed in terms of synchronization and fault-tolerance by comparing it with a conventional approach in the presence of two loop patterns.