Redundant Controller Preloading for Fast Failover in Networked Control
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Solution Overview
Problem
Existing control systems in distributed environments face challenges in maintaining high availability and reliability when failures occur, particularly due to the difficulty in quickly switching between controllers with short switching time margins, as seen in configurations like JP 9-330106 A and JP 2007-274255 A.
Innovation Solution
A control system where multiple controllers are connected via a common network, with a redundant controller holding context data and programs of highly available and normal controllers in non-volatile memory, allowing for immediate substitution of processing in case of failures by using pre-held context and program data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a backup controller is used to ensure system continuity, then reliability is improved, but switching time increases due to program download requirements
Solution Approach 1:
The backup controller pre-stores the control program and context data of the active controller in its memory before failure occurs. This preliminary preparation eliminates the need for program download after failure, enabling immediate switching and resolving the time loss contradiction while maintaining reliability.
2Reliability
If full redundancy is implemented for all controllers, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The backup controller is designed with multi-functionality, capable of storing and executing programs from multiple different controllers. A single backup controller can replace any failed controller in the system, eliminating the need for dedicated backup units for each controller and reducing overall system complexity while maintaining high availability.
Solution Approach 2:
Instead of implementing physical redundancy with identical backup hardware for each controller, the system uses data copying where the backup controller stores copies of control programs and context information in memory. This virtual copying approach provides redundancy without proportionally increasing hardware complexity.
3Adaptability or versatility
If context data is transferred via network after failure, then adaptability is improved, but switching speed decreases
Solution Approach 1:
The backup controller pre-loads and stores context data and control programs in its local memory before failure occurs. This preliminary action eliminates the need for post-failure network data transfer, enabling immediate local execution and achieving both high switching speed and adaptability.
Data Source
AI summary
A control system in which a plurality of controllers and a redundant controller are connected to a common network, the plurality of controllers are divided into a highly available controller and other normal controllers, the redundant controller obtains context data of the highly available controller to hold the context data in a memory, holds programs of the plurality of controllers in a non-volatile memory, and holds the program of the highly available controller in the memory, and an arithmetic unit substitutes processing of the highly available controller by using the context data and the program of the highly available controller held in advance in the memory when a failure occurs in the highly available controller.