Redundant Automation System With Asynchronous Slave PLC Backup
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Solution Overview
Problem
Current redundant automation systems require high hardware outlay and complex configuration to achieve redundancy, leading to increased costs and complexity, and existing solutions do not efficiently manage failover without disrupting the technical process.
Innovation Solution
Implementing a redundant automation system where only selected master PLCs are operated redundantly using a backup PLC, with asynchronous synchronization to reduce hardware complexity and ensure bumpless failover, allowing the slave PLC to take over in case of master PLC failure, and using a multi-core based backup PLC for efficient redundancy management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all master PLCs are operated redundantly with dedicated slave PLCs, then system reliability is improved, but hardware cost and device complexity increase significantly
Solution Approach 1:
The slave PLC is designed to serve multiple master PLCs simultaneously, acting as a universal backup unit. Instead of dedicating one slave PLC to each master PLC, a single slave PLC can take over control tasks from any of the master PLCs in case of failure, reducing the total number of required PLC units while maintaining system reliability
Solution Approach 2:
The control tasks and programs from multiple master PLCs are merged into a single slave PLC. The slave PLC is configured to execute control programs from different masters and manage multiple process areas, combining the functionality of multiple dedicated backup units into one centralized backup system
2Reliability
If synchronous synchronization is implemented between master and slave PLCs, then bumpless failover is achieved, but processing time and system complexity increase
Solution Approach 1:
The slave PLC continuously executes control programs in advance and maintains readiness to take over, with programs being pre-loaded and synchronized asynchronously. This preliminary preparation ensures that when failover is needed, the slave can immediately assume control without requiring time-consuming synchronous synchronization at the moment of failure
Solution Approach 2:
The synchronization mechanism is made dynamic by allowing asynchronous operation during normal conditions, where the slave PLC processes programs independently without strict timing constraints. The system transitions to synchronous operation only when failover is detected, adapting the synchronization behavior to the actual system state and needs
3Device complexity
If a single slave PLC serves multiple master PLCs, then hardware cost is reduced, but the slave PLC must process multiple control programs simultaneously increasing operational complexity
Solution Approach 1:
The control programs are segmented into distinct process areas, with each master PLC associated with specific process areas. The slave PLC is configured to handle specific segments or process areas from different masters, dividing the overall program management into manageable sections rather than requiring the slave to manage all programs simultaneously in a monolithic structure
Solution Approach 2:
A program storage area or memory structure acts as an intermediary between multiple master PLCs and the slave PLC. Control programs from different masters are stored in this intermediate storage area, which organizes and manages the programs, allowing the slave PLC to access and execute them in an organized manner without direct complex interactions with all masters
Data Source
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AI summary
The invention relates to a redundant automation system with several interconnected automation devices, each of which processes a control program to control a technical process. The automation system comprises several automation devices operating as masters, and measures are proposed by which redundant operation can be achieved with reduced hardware requirements.