Concurrent Safety Connections in HA Control Networks
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Solution Overview
Problem
High availability (HA) and safety industrial control systems face challenges in efficiently communicating between redundant devices without exceeding communication network bandwidth, and existing solutions do not effectively balance the requirements of HA and safety attributes.
Innovation Solution
The implementation of concurrent connections as a fault-tolerant mechanism at the transport layer, which sets up multiple paths for redundancy between connection originator and target modules, ensuring continuous operation and detection of failures while reducing safety connection timeouts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple redundant communication paths are established between HA control systems and safety instrumented systems, then system availability and fault tolerance are improved, but communication network bandwidth is exceeded
Solution Approach 1:
The communication network is segmented into two distinct types of connections: concurrent connections for safety-critical data and standard connections for non-safety data. This segmentation allows safety data to have dedicated communication paths while non-safety data shares available bandwidth, preventing total bandwidth exhaustion while maintaining safety system reliability.
Solution Approach 2:
Different quality levels of communication are assigned to different data types: safety data receives high-priority, dedicated communication resources with guaranteed bandwidth and lower latency, while non-safety data receives best-effort service. This local quality differentiation ensures safety systems maintain high availability without requiring all network resources.
2Reliability
If concurrent connections are implemented for safety data transmission, then fault detection capability is improved, but connection management complexity increases
Solution Approach 1:
A connection manager component acts as an intermediary that automatically handles the complexity of concurrent connection management. It monitors connection status, detects failures, and manages the concurrent connection pool without requiring complex intervention from end devices. This intermediary approach maintains high fault detection capability while reducing the operational complexity burden on the system.
3Duration of action of stationary object
If redundant communication paths are used, then system operation continuity is improved, but the number of connections and management overhead increase
Solution Approach 1:
Instead of establishing full redundancy for all connections, the system implements concurrent connections selectively for safety-critical data streams that require fault tolerance. Non-safety data uses standard single connections. This partial redundancy approach maintains system operation continuity for critical functions while limiting the total number of connections and management overhead to necessary levels.
Data Source
AI summary
A system for communicating between redundant devices balances the desired attributes of a high availability (HA) control system and a safety control system. The system includes concurrent connections as a fault tolerant mechanism for industrial protocol connections at the transport layer. The concurrent connections establish multiple paths for redundancy from a data producer to a data consumer. Concurrent connections increase availability of the HA control and safety instrumented systems. More specifically, concurrent connections and architectural redundancies eliminate a single point of failure within the control system and further reduce safety connection timeouts during fault detection and/or recovery. Concurrent connections may be used to keep a HA system operational or to provide detection of a failure in a safety system. The industrial control network may be configured to function as a HA control system, as a safety control system, or with certain degrees of both HA and safety-related operation.