Redundant PLC Synchronization Using Dual Runtime Data Files
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Solution Overview
Problem
Conventional redundant automation systems face challenges in maintaining uninterrupted data capture and synchronization during the transition from solo to redundant operation, leading to potential data loss and increased complexity in write access management.
Innovation Solution
A method involving a first and second data reconciliator that writes status information into both files, monitors write access validity, locks further write accesses to the second file during synchronization, and transfers the locked file to the second subsystem, ensuring data integrity and continuous capture by saving write accesses chronologically until all changes are processed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If write access to persistent data is locked during synchronization procedure, then data integrity during transfer is ensured, but data capture is interrupted and write access is delayed until synchronization completes
Solution Approach 1:
The patent segments the file system into two separate files: a first file for active write access during synchronization and a second file for data capture operations. This segmentation allows simultaneous read/write operations on different files, eliminating the need to lock the entire file system during synchronization while ensuring data integrity through coordinated access management.
Solution Approach 2:
The patent introduces a switching mechanism that acts as an intermediary between the control program and the file system. This switch dynamically redirects write accesses between the first and second files based on the synchronization state, allowing continuous data capture while protecting the integrity of the file being synchronized.
2Reliability
If status information is copied to newly added PLC during update phase, then redundancy is achieved, but complex coordination of simultaneous read/write accesses is required
Solution Approach 1:
The patent implements dynamic file role assignment where the first and second files switch functions based on the synchronization state. During synchronization, the first file is locked for writing while the second file accepts writes; after synchronization, roles reverse. This dynamic approach simplifies coordination by providing a clear, state-dependent access pattern rather than complex simultaneous access management.
Solution Approach 2:
The patent performs preliminary data preparation by maintaining two files in advance - one ready for synchronization and another ready for immediate writing. This preliminary arrangement eliminates the need for complex real-time coordination during synchronization, as the system has already prepared alternative storage locations.
3Reliability
If all status-relevant data is transferred during synchronization, then complete redundancy is achieved, but data loss occurs or complex temporary storage is required for dynamic runtime data
Solution Approach 1:
The patent ensures continuous data capture by directing write operations to the second file during synchronization of the first file. This continuous writing action prevents data loss by ensuring that dynamic runtime data is always being captured, even while synchronization is in progress. The useful action of data capture never stops, only the target file changes.
Solution Approach 2:
The system prepares the second file in advance as a ready-to-use alternative storage location. This preliminary preparation ensures that when synchronization of the first file occurs, data can immediately continue to be written to the second file without interruption or loss, eliminating the need for complex temporary storage mechanisms.
Data Source
AI summary
A redundant automation system includes a first and second subsystems, which each have a control program for controlling a technical process and are each configured in an identical manner, and a synchronization connection between the first subsystem and the second subsystem, wherein in order to capture dynamic runtime data a first data reconciliator has a first file and a second file, where the first data reconciliator is configured to write the status information into the first and second files during a data collection phase, to keep the dynamic runtime data up to date via write accesses to the first and second files and, at the start of a synchronization phase, to lock further write accesses to the second file and to only permit write accesses to the first file, and to also transfer the locked second file to the second subsystem.