Redundant Bus Subscriber Communication Blocking on Fault Detection
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Solution Overview
Problem
In safety-related systems with distributed safety modules via a communication bus, central units lack direct access to output modules, making it difficult to switch off outputs independently of logic units, especially in cases of common cause failures such as power supply voltage drifts.
Innovation Solution
A bus subscriber with a redundant structure, comprising two logic units, a monitoring circuit, and a transmission unit, which communicates via a media access controller and blocks communication upon detecting errors, preventing the transmission of corrupted data and ensuring safe communication interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a monitoring circuit is implemented in the central unit to monitor supply voltage, then common cause faults can be detected, but the central unit cannot directly switch off distributed output modules coupled via the bus
Solution Approach 1:
The safety function is segmented between the central unit (monitoring and detection) and the distributed output modules (local switching capability). Each output module is equipped with its own monitoring circuit and switching mechanism, allowing independent operation from the central unit. This segmentation enables the central unit to detect faults while individual modules can autonomously switch off their outputs.
Solution Approach 2:
The patent introduces an intermediary monitoring circuit within each distributed output module that acts as a local agent. This intermediary circuit receives supply voltage monitoring independently and can trigger local switching off of outputs without requiring direct control from the central unit, thus bridging the gap between central monitoring capability and distributed switching requirement.
2Ease of operation
If direct access from central unit to output modules is implemented, then independent switching is enabled, but system complexity and bus coupling requirements increase
Solution Approach 1:
Each distributed output module is equipped with self-service capabilities including local supply voltage monitoring and autonomous switching mechanisms. The modules can independently detect faults and switch off their outputs without requiring direct control signals from the central unit, thereby eliminating the need for complex direct access pathways while maintaining independent switching functionality.
Solution Approach 2:
The system architecture is segmented into autonomous output modules that handle their own monitoring and switching operations. This segmentation eliminates the need for complex centralized control pathways to each module, reducing overall system complexity while enabling independent switching through local autonomy.
Data Source
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AI summary
The invention relates to a bus subscriber (10) which comprises a first logic unit (11), a second logic unit (12), a monitoring circuit (13) and a transmission unit (14). The bus subscriber (10) is designed in such a manner that, in a communication phase, the first logic unit (11) communicates with a bus (21) via the transmission unit (14) and that, in the event of a fault, the monitoring circuit (13) outputs a monitoring signal (SU) to the transmission unit (14) such that the transmission unit (14) blocks the communication.