Ethernet Time Synchronization via Segment-Specific Telegram Conversion
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Solution Overview
Problem
In Ethernet-based networks used for industrial control and automation, achieving precise time synchronization across multiple segments with varying transmission rates is challenging due to differences in internal timers, leading to potential drift and the need for cyclic synchronization to maintain a common time base.
Innovation Solution
A method involving a master network subscriber that sends synchronization telegrams to each segment, where network distributors convert and forward these telegrams, allowing network subscribers to adjust their local system time using synchronization values, accounting for delay times to ensure synchronization across the network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cyclic time synchronization is performed on field buses to ensure precise time coordination, then time synchronization precision is improved, but device complexity and processing overhead increase
Solution Approach 1:
The network is divided into multiple segments with network distributors positioned at segment boundaries. Each network distributor independently manages time synchronization for its respective segment by receiving synchronization telegrams from the master subscriber and converting them into segment-specific synchronization signals. This segmentation allows precise time coordination within each segment while reducing the complexity of managing synchronization across the entire network.
Solution Approach 2:
Network distributors act as intermediary devices between the master subscriber and network subscribers in different segments. These distributors receive synchronization telegrams, convert them into appropriate formats for their segments, and forward them to local network subscribers. This intermediary approach simplifies the synchronization process by distributing the timing function across multiple devices rather than requiring all devices to directly communicate with the master subscriber.
2Measurement precision
If network distributors convert and forward synchronization telegrams to maintain synchronization across segments with varying transmission rates, then time synchronization precision is improved, but telegram processing complexity increases
Solution Approach 1:
Each network distributor is configured with segment-specific parameters including transmission rates and delay times characteristic of its local segment. The distributor converts synchronization telegrams by adjusting timing information according to its local segment's characteristics rather than using a uniform conversion approach. This local quality approach maintains synchronization precision across segments with varying transmission rates while simplifying the conversion process by tailoring it to specific segment requirements.
Solution Approach 2:
Network distributors modify specific parameters of synchronization telegrams such as timing offsets, transmission intervals, and synchronization values to match the characteristics of their target segment. By changing these parameters according to segment-specific transmission rates and delay times, the system maintains precise time synchronization across heterogeneous segments without requiring complex real-time adjustments.
3Measurement precision
If network subscribers adjust their local system time speed using synchronization values to compensate for timer differences, then time synchronization precision is improved, but processing time and computational overhead increase
Solution Approach 1:
Network subscribers perform preliminary calculations of time adjustments based on synchronization values received from network distributors. The adjustment parameters are pre-computed and stored, allowing subscribers to quickly apply time corrections without performing complex real-time computations. This preliminary action reduces processing time during actual synchronization operations while maintaining high precision in time coordination.
Data Source
AI summary
A method for synchronizing time in an Ethernet-based network having a master network subscriber, a first segment and a second segment. Each segment has at least one network subscriber. The second segment is connected to the first segment by a first network distributor, arranged in the second segment. The method comprises steps for sending out a synchronization telegram addressed to the second segment by the master network subscriber, the synchronization telegram being of the first type; receiving the synchronization telegram by the first network distributor, for conversion into a second type; forwarding the synchronization telegram to a network distributor of the second segment, by the first network distributor; reading out a synchronization value stored in the synchronization telegram by the first network distributor of the second segment; and adjusting a speed of a local system time of the network distributor of the second segment, using the synchronization value.