RTU CPU Redundancy Synchronization for Real-Time Warm Standby
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Solution Overview
Problem
Synchronizing dual remote terminal unit (RTU) central processing units (CPUs) in a way that is transparent to users and covers most RTU data processing use cases is difficult, particularly in duplicating events, firmware upgrades, and logic states between warm-standby RTU controllers.
Innovation Solution
A redundancy protocol that allows for concurrent synchronization of time-stamped events, firmware updates, and logic state-data duplication between main and standby RTU CPUs using the same communication channel, ensuring seamless data transfer and minimal downtime during transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate communication channels are used for event transfer, firmware updates, and logic state synchronization between RTU CPUs, then reliability of data transfer is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple communication functions (event transfer, firmware updates, logic state synchronization) into a single communication channel between RTU CPUs. This merging approach maintains data transfer reliability by implementing protocol-level multiplexing that separates different data types and priorities, while reducing the overall number of physical communication channels required.
Solution Approach 2:
The communication channel is designed to be universal, handling multiple types of data traffic including time-stamped events, firmware update packets, and logic state synchronization data. The protocol implements function codes that identify the type of data being transmitted, allowing a single channel to perform multiple communication functions that would traditionally require separate dedicated channels.
2Speed
If multiple communication channels are used for concurrent synchronization operations, then synchronization speed is improved, but device complexity increases
Solution Approach 1:
The patent implements preliminary prioritization of data types, where time-stamped events are assigned highest priority for immediate transmission, followed by logic state synchronization, and finally firmware updates. This preliminary classification allows the single communication channel to process data in the correct sequence without requiring multiple parallel channels, maintaining synchronization speed while reducing complexity.
Solution Approach 2:
The communication protocol dynamically adjusts transmission priorities based on the current operational state of the RTU system. When events are being generated, the channel prioritizes event transmission; when logic states need synchronization, it switches to that mode; and when firmware updates are pending, it allocates bandwidth accordingly. This dynamic prioritization enables fast concurrent synchronization operations over a single adaptive communication channel.
3Reliability
If time-stamped events are buffered on both main and standby RTU CPUs, then system availability is improved, but memory requirements increase
Solution Approach 1:
The patent implements a selective copying strategy where time-stamped events are buffered on the standby RTU CPU only when they are generated on the main RTU CPU. This creates a synchronized copy of critical event data on the standby unit, ensuring that if a failover occurs, the standby system has the necessary event history to maintain system availability. This approach provides the reliability benefits of dual buffering while minimizing memory requirements by avoiding redundant full buffers on both systems.
4Reliability
If firmware updates are performed on both RTU CPUs simultaneously, then system availability is maintained, but synchronization complexity increases
Solution Approach 1:
The patent implements a preliminary update sequence where the standby RTU CPU is updated with the new firmware version first, while the main RTU CPU continues to operate on the existing firmware. This preliminary action ensures that a compatible firmware version is ready on the standby unit before the main unit is updated, allowing for seamless failover if the main unit update fails. This approach maintains system availability while simplifying synchronization by avoiding the complexity of coordinating simultaneous updates on both CPUs.
Data Source
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AI summary
Redundancy synchronization of remote terminal unit (RTU) central processing units (CPUs) associated with an industrial operation includes queuing time-stamped events on a main RTU CPU for transfer to a standby RTU CPU as the time-stamped events are generated on the main RTU CPU (i.e., in real-time). The synchronized RTU CPUs further permit synchronization of logic states and synchronization of firmware upgrades. Synchronization activities occur on the same synchronization communications channel between redundant RTU CPUs.