Substitute Server Failover Using Reduced Telegram Data
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Solution Overview
Problem
Existing automation systems face challenges in reliably detecting the failure of a server unit and seamlessly transitioning to a reduced operational mode to prevent damage and ensure fault tolerance.
Innovation Solution
The automation system incorporates a main server unit, a substitute server unit, and client units connected via a field bus. The system continuously monitors the main server unit's functionality and activates a failure operating mode when a failure is detected, allowing the substitute server unit to take over and exchange failure telegrams with reduced data elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redundant controller is provided in the automation system having two identical server units, then the fault tolerance is improved, but the device complexity and cost increase
Solution Approach 1:
The substitute server unit is configured to receive and store normal telegrams from the main server unit, creating a simplified copy of the operational data structure. This allows the substitute unit to take over in failure mode without requiring full functional equivalence, reducing complexity while maintaining fault tolerance
Solution Approach 2:
The telegram data structure is segmented into relevant data elements and optional data elements. The substitute server unit only needs to maintain and process the relevant data elements for failure operation, separating critical functions from non-critical ones to reduce the burden on the redundant unit
2Ease of operation
If the substitute server unit uses data values of relevant data elements from normal telegrams, then the transition to failure mode is simplified, but the loss of information increases due to using default values for optional elements
Solution Approach 1:
Different data elements are treated differently: relevant data elements are preserved with their actual values from normal telegrams, while optional data elements are replaced with default values. This selective approach maintains critical information while allowing simplification in non-critical areas
Data Source
AI summary
In an automation system, a substitute server unit is configured to receive normal telegrams exchanged between a main server unit and a client unit. The functionality of the main server unit is continuously monitored. If a failure event of the main server unit is detected, the substitute server unit is configured to activate a failure operating mode, wherein the substitute server unit and the client unit exchange failure telegrams in the failure operating mode. In the failure telegrams, the predefined user data structure of the normal telegrams is divided up into relevant data elements and optional data elements. The substitute server unit is configured to use the data values of the relevant data elements of the current normal telegram for the relevant data elements of the first failure telegram and to use the default data values specified for the optional data elements of the first failure telegram.