Remote Unit Abnormality Detection Independent of CPU Cycles
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Solution Overview
Problem
Existing remote units for programmable logic controllers rely on CPU operating cycles and communication cycles to detect abnormalities in control targets, leading to delayed updates and inability to detect abnormalities when the CPU fails, limiting the ability to change or stop analog outputs.
Innovation Solution
A remote unit with an external input section to receive detection results, an abnormality determining section to assess these results, and an output section to change or stop control outputs independently of the CPU, allowing for early detection and processing of abnormalities without relying on CPU cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the CPU unit executes a control program to monitor the state of the control target, then the abnormality can be detected, but the detection time and output update time are delayed due to dependency on CPU operating cycle and communication cycle
Solution Approach 1:
The patent segments the control system into two independent parts: the CPU unit for general control and the remote unit for real-time abnormality monitoring. The remote unit independently receives detection results from detection means and determines abnormalities without waiting for CPU processing cycles, thereby reducing detection time while maintaining reliable abnormality detection capability.
2Speed
If the remote unit independently determines abnormalities and changes output, then the response speed increases and CPU dependency decreases, but the system complexity increases
Solution Approach 1:
The patent extracts the abnormality determination function from the CPU unit and places it in the remote unit. This extraction allows the remote unit to independently and quickly determine abnormalities and change outputs without waiting for CPU processing, thereby increasing response speed. The added complexity is localized to the remote unit, which is a dedicated component designed specifically for this function.
Data Source
AI summary
A remote unit (1) that controls a control target (4) on the basis of a command from a CPU unit (2) is provided with: an external input section (11) to receive a detection result of a state of the control target from a detection means (3) that detects the state of the control target; an output section (13) to output a control output for controlling the control target; and an abnormality determining section (12) to determine an abnormality of the control target on the basis of the detection result and to output to the output section, a control instruction to instruct a change or a stop of the control output if the control target is determined to be abnormal.