Time Synchronization Subnodes for Fast Reference Failover
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Solution Overview
Problem
Existing time synchronization methods in factory automation networks experience instability and abnormal synchronization when the time synchronization reference node disconnects, especially in networks with multiple paths, leading to prolonged selection times and increased time differences among subnodes.
Innovation Solution
A time synchronization subdevice that relays shared time and priority information to other subdevices, allowing for rapid selection of a new reference node without performing the Best Master Clock Algorithm (BMCA) by using pre-assigned first and second priorities to manage time distribution and synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the Best Master Clock Algorithm (BMCA) is performed to select a new time synchronization reference node when the current reference node disconnects, then the network can eventually restore time synchronization, but the selection process takes longer time and causes greater time differences among subnodes
Solution Approach 1:
The patent applies preliminary action by pre-assigning priority values to each device in the network before any disconnection occurs. When the reference node disconnects, subnodes with higher priorities can immediately take over without needing to perform the time-consuming BMCA process. This pre-prepared priority information enables rapid reference node selection and maintains time synchronization stability while minimizing disruption time.
2Duration of action of stationary object
If multiple network devices forcibly distribute time when the reference node disconnects, then time distribution continues without interruption, but time synchronization referencing to a single clock is not performed and errors accumulate
Solution Approach 1:
The patent applies local quality by enabling only specific subnodes with the highest priorities to act as temporary reference nodes and distribute time, rather than allowing all subnodes to distribute time simultaneously. This selective approach ensures that time distribution continues without interruption while maintaining reference to a single authoritative clock source, preventing error accumulation across the network.
3Duration of action of stationary object
If time synchronization subnodes use their own clocks to measure time when the reference node is disconnected, then time measurement continues, but differences in clock accuracy generate time differences between subnodes
Solution Approach 1:
The patent applies preliminary action by pre-configuring priority information in each subnode before disconnection occurs. When the reference node disconnects, subnodes with higher priorities immediately assume reference node functionality and provide a unified time source for all other subnodes. This prevents subnodes from using their own inaccurate clocks and eliminates time differences caused by varying clock accuracies.
Data Source
AI summary
A time synchronization subdevice includes a periodic data receiver that receives periodic data transmitted periodically from a time synchronization reference device, an acquirer that acquires first priority information indicating a first priority assigned to the time synchronization reference device, a first priority transmitter that transmits the first priority information to another time synchronization subdevice, a second priority information transmitter that transmits, when the periodic data is interrupted, transmission information indicating a second priority assigned to the time synchronization subdevice, a second priority information receiver that receives reception information indicating a second priority assigned to a device different from the time synchronization subdevice, and a distributor that distributes, when the periodic data is interrupted and the second priority indicated with the transmission information is higher than the second priority indicated with the reception information, time measured by a clocking unit as new shared time to the another time synchronization subdevice.