Single-Wire Safety System Architecture for Reliable Monitoring
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Solution Overview
Problem
Industrial safety systems require reliable safety device monitoring without the need for dual redundant signal channels, as dual redundant channels increase wiring complexity and introduce the risk of cross faults, while single-wire solutions lack redundancy for ensuring safety reliability.
Innovation Solution
A single-wire safety system architecture that uses a safety relay as a communications master and safety devices configured to perform two-channel evaluations of pulse signals, with a safety master generating a defined pulse train that is passed through each device, allowing bi-directional communication and message exchange over a single wire, ensuring reliable safety monitoring and diagnostics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dual redundant signal channels are used for safety monitoring, then safety reliability is improved, but wiring complexity increases and cross fault risks are introduced
Solution Approach 1:
The patent combines multiple functions (safety monitoring, diagnostics, communication) into a single-wire architecture. The safety input device integrates a safe state detection component, pulse detection component, safety signal relaying component, and message processing component all operating over one communication channel, eliminating the need for separate redundant wiring while maintaining safety integrity through integrated two-channel evaluation of the single wire signal
2Reliability
If dual redundant signal channels are used for safety monitoring, then safety reliability is improved, but cross fault risks increase
Solution Approach 1:
By merging safety monitoring and diagnostics into a single-wire system, the patent eliminates the physical separation that could lead to cross faults between redundant channels. The integrated architecture ensures that both safety evaluation channels share the same communication medium, preventing independent faults that could occur in separately wired redundant systems
Solution Approach 2:
The patent implements continuous feedback through the single-wire communication channel, where the message processing component monitors signal integrity and device status. This feedback mechanism detects faults early and maintains safety reliability without requiring physically separate redundant channels that could develop cross faults
3Device complexity
If single-wire solution is used for safety monitoring, then wiring complexity is reduced, but redundancy for safety reliability is lost
Solution Approach 1:
The patent segments the safety monitoring function into two independent evaluation channels within the safety input device, both operating over the single-wire medium. The safe state detection component and pulse detection component provide separate evaluation paths that maintain redundancy while using the same physical communication channel, thus reducing wiring complexity without sacrificing safety reliability
Solution Approach 2:
The single-wire communication channel serves multiple functions simultaneously: it carries safety monitoring signals, diagnostic information, and device communication data. This multi-functional use of a single wire provides the necessary redundancy for safety reliability while minimizing wiring complexity, as the same medium supports both safety-critical and non-critical functions
Data Source
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AI summary
A single-wire safety system architecture is provided that yields reliable safety device monitoring without the need for dual redundant signal channels. The safety system comprises a safety relay acting as a communications master device and one or more compatible safety input devices connected in series with the safety relay via a single-wire communication circuit. The safety input device farthest from the safety relay on the safety circuit modulates a safety signal with a recognizable pulse pattern that traverses the single-wire safety circuit to the safety relay via the intermediate safety devices. The safety relay maintains safety mode as long as the pulse pattern is received and recognized. In addition to conveying the safety signal, the architecture allows bi-directional communication of initialization, configuration, and diagnostic messages over the single-wire safety channel. The architecture also facilitates rapid initialization of the safety channel using asynchronous sub-link detection and device enumeration.