Multiplexed Signal Inspection for Chattering Detection
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Solution Overview
Problem
Conventional methods fail to detect signal abnormalities like chattering in multiplexed signals within a short cycle that does not exceed the allowable period, leading to undetected safety malfunctions in systems like programmable controllers.
Innovation Solution
A signal inspection apparatus comprising an acquisition unit to acquire signal values, a count unit to count changes in a predetermined time frame, a calculation unit to calculate differences between signal counts, and an output unit to indicate discrepancies if the difference exceeds an allowable value, allowing for the detection of signal abnormalities in shorter cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional signal inspection methods are used to detect discrepancy between multiplexed signals, then safety is enhanced by cross-checking signal values, but signal abnormalities such as chattering in short cycles cannot be detected because the inspection cycle exceeds the abnormality duration
Solution Approach 1:
The patent segments the signal inspection process into two distinct inspection methods: a first inspection method that compares signal values at specific timing points (suitable for detecting sustained discrepancies), and a second inspection method that counts signal changes over a predetermined time frame (suitable for detecting short-cycle abnormalities like chattering). This segmentation allows each method to specialize in detecting different types of signal abnormalities, thereby resolving the contradiction between safety and detection precision.
Solution Approach 2:
The patent dynamically selects between two different inspection approaches based on the characteristics of the signal being monitored. The system can switch between value comparison (first inspection) and change counting (second inspection) depending on the expected nature of potential abnormalities. This dynamic adaptation enables the system to maintain high detection precision across various abnormality types while preserving safety through comprehensive monitoring.
2Reliability
If the allowable period for signal discrepancy is set long to ensure safety, then safety margin is increased, but detection response time increases and short-cycle abnormalities are missed
Solution Approach 1:
The patent implements periodic signal inspection with a predetermined cycle, and within each cycle, performs both the first inspection (value comparison) and the second inspection (change counting). The second inspection specifically uses a predetermined time frame that is shorter than the allowable period, enabling detection of short-cycle abnormalities. This periodic multi-method inspection resolves the contradiction by maintaining safety through regular comprehensive checks while reducing detection response time through the use of shorter inspection intervals.
3Measurement precision
If signal inspection is performed in every cycle to detect short-cycle abnormalities, then detection precision is improved, but system complexity and processing load increase
Solution Approach 1:
The patent applies partial inspection by performing the more resource-intensive second inspection method (change counting over predetermined time frame) only when necessary, rather than continuously applying both inspection methods in all cycles. This partial application of the enhanced inspection method maintains high detection precision for short-cycle abnormalities while avoiding the excessive processing load that would result from running both inspections continuously, thus resolving the contradiction between detection precision and system complexity.
Data Source
AI summary
A signal inspection apparatus, a signal inspection system, a signal inspection method, and a non-transitory computer-readable medium encoded with a signal inspection program are provided, all of which can appropriately detect discrepancy between multiplexed signals. A signal inspection apparatus includes: an acquisition unit that acquires values of at least two signals among multiplexed signals in a predetermined cycle; a count unit that counts respective changes in the at least two signals in a predetermined time frame; a calculation unit that calculates a difference between the counts of changes; and an output unit that performs an output indicating discrepancy between the signals, if the difference between the counts of changes exceeds an allowable value.