Safety System Local Evaluation Unit Error Detection
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Solution Overview
Problem
Safety systems with multiple interruptible signal transmission paths face challenges in detecting discrepancies between redundant channels, leading to potential loss of redundancy and impaired safety due to increased cabling demands and error recognition limitations.
Innovation Solution
A safety system with a local evaluation unit integrated into the safety-related participant that checks the simultaneous interruption of two interruptible signal transmission paths and opens an interruption switch if they are not both interrupted, ensuring reliable error recognition and activation of the safety function without additional cabling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple interruptible signal transmission paths are connected in a common test signal path to reduce cabling demands, then the demand in cabling is reduced, but the safety of the system is impaired due to inability to detect discrepancy errors between redundant channels
Solution Approach 1:
The patent divides the common test signal path into separate evaluation zones for each interruptible signal transmission path by introducing individual interruption switches (66a, 66b) and evaluation units (50) at each safety-related participant. This segmentation allows independent monitoring of each path while maintaining the common test signal path structure, enabling discrepancy error detection without increasing cabling demand.
Solution Approach 2:
The patent implements feedback mechanisms where evaluation units (50) continuously monitor the interruption status of each signal transmission path and provide feedback to the safety unit (10). The interruption switches (66a, 66b) are controlled based on this feedback to ensure proper test signal path interruption. This feedback system enables the detection of discrepancy errors between redundant channels while maintaining the reduced cabling structure.
2Reliability
If each safety related participant is connected via an own test signal path to ensure reliable error recognition, then the safety level is maintained, but the demand in cabling and number of outputs/safety inputs increases significantly
Solution Approach 1:
The patent merges multiple individual test signal paths into a single common test signal path that traverses all safety-related participants (22a, 22b) in series. The test signal line (18) and bus line (20) are shared among all participants, reducing the overall cabling demand and number of interfaces at the safety unit while maintaining the ability to individually evaluate each participant through locally integrated interruption switches and evaluation units.
Solution Approach 2:
The patent shifts the evaluation function from the central safety unit to the local safety-related participants by integrating interruption switches and evaluation units at each participant location. This dimensional shift distributes the evaluation functionality across the system, allowing individual path monitoring without requiring separate central evaluation channels, thus reducing interface complexity at the safety unit.
3Quantity of substance
If interruptible signal transmission paths are connected in a row in a common test signal path, then cabling demand is reduced, but discrepancy errors remain undetected leading to loss of redundancy
Solution Approach 1:
The patent implements preliminary evaluation at each safety-related participant before the test signal reaches the central safety unit. The evaluation units (50) at each participant proactively check the interruption status of their respective signal transmission paths and control the interruption switches (66a, 66b) accordingly. This preliminary action ensures that discrepancy errors are detected and addressed before they can compromise system safety, maintaining error detection capability while using a common test signal path.
Data Source
AI summary
A safety system includes a safety unit and at least one safety related participant which comprises a protective device and a first and a second interruptible signal transmission path which can be interrupted together on the occurrence of a non-secure state of the protective device. The safety system includes at least one test signal path which runs through the safety related participant to a safety input of the safety unit starting from an output of the safety unit and comprises at least one of the first and the second interruptible signal transmission paths. The safety related participant comprises an interruption switch arranged in the test signal path and an evaluation unit which is connected to the first signal transmission path and/or to a first switching signal output of the protective device and to the second signal transmission path and/or to a second switching signal output of the protective device.