Safety Controller History Logging for False OFF Signal Diagnosis
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Solution Overview
Problem
Industrial safety systems often output false OFF signals, leading to unnecessary machine stoppages and reduced production efficiency, necessitating quick determination of the cause of these false signals.
Innovation Solution
A safety controller with an input part, safety control part, acquisition unit, and history recording unit that records input and output signals along with extra information from safety devices, enabling the determination of false OFF signal causes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two MCUs are provided to increase reliability of the safety system, then reliability is improved, but false OFF signals may still occur causing machine stoppages
Solution Approach 1:
The system performs preliminary actions by recording input signals, output signals, and extra information from safety devices before false OFF signals occur. This historical data is stored in advance to enable rapid cause determination when false OFF signals happen, thus maintaining high reliability while minimizing production downtime.
Solution Approach 2:
The system implements feedback by continuously monitoring and recording the operational history of safety devices, MCUs, and signal states. When a false OFF signal occurs, this feedback information allows operators to quickly identify the cause (such as which MCU or safety device is responsible), thereby resolving the contradiction between reliability and productivity.
2Object-affected harmful factors
If safety system outputs OFF signal when danger is detected, then safety is improved, but false OFF signals cause unnecessary machine stoppages
Solution Approach 1:
The system records operational history in advance including input signals from safety devices, output signals from MCUs, and extra information such as device states and error flags. This preliminary recording ensures that when a false OFF signal occurs, the cause can be immediately identified without lengthy investigation, thus minimizing machine stoppage time while maintaining safety protection.
3Difficulty of detecting and measuring
If extra information is recorded from safety devices, then cause determination is improved, but device complexity increases
Solution Approach 1:
The history recording system is segmented into distinct functional units: an acquisition unit that collects extra information from safety devices, a storage unit that records this information alongside input and output signals, and a display unit that presents the data. This segmentation makes the complex system manageable and facilitates easy cause determination without overwhelming device complexity.
Data Source
AI summary
Recording a history related to an operation of a safety program contributes to a determination of a cause of a false OFF signal. A safety controller acquires, from at least one safety input device or safety sensor, extra information that is not used for obtaining an output signal and records an input signal and an output signal together with the extra information as history information at predetermined recording intervals.