PLC Buffer Logging to Prevent Overwritten Trouble Data
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Solution Overview
Problem
Existing data logging techniques in factory automation systems often result in log data being overwritten in temporary recorders before issues occur, due to long periods between recording triggers and multiple triggers being generated, leading to difficulties in identifying the cause of troubles.
Innovation Solution
A programmable controller with collecting, buffering, and logging means that discards data stored in the buffer when a specific canceling condition is satisfied, reducing the likelihood of data loss and facilitating subsequent examination by managing data storage effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If log data is continuously recorded in a temporary recorder with limited capacity, then the quantity of log data increases to capture more control history, but the data to be used for trouble analysis may be overwritten before a trouble occurs
Solution Approach 1:
The system performs preliminary actions by detecting troubles in advance and proactively managing data retention. When a trouble is detected, the system identifies and preserves relevant log data before it can be overwritten, ensuring critical information is saved for subsequent analysis.
Solution Approach 2:
The system implements feedback mechanisms by continuously monitoring control data for trouble conditions. When troubles are detected, the feedback loop triggers data preservation actions, allowing the system to adapt its data retention strategy based on actual operational conditions and trouble patterns.
2Reliability
If a large capacity temporary recorder is used to prevent data overwriting, then the reliability of log data preservation improves, but the device complexity and cost increase
Solution Approach 1:
The system employs dynamic data management where the buffer allocation and data retention strategy adapt based on operational conditions. Instead of using a fixed large-capacity recorder, the system dynamically adjusts which data to preserve and for how long, optimizing the balance between reliability and resource usage.
Solution Approach 2:
The system changes parameters such as buffer size allocation, data retention period, and recording frequency based on detected trouble patterns and operational conditions. This allows the system to maintain high reliability for critical data while using smaller overall storage capacity compared to static approaches.
3Reliability
If data is retained in the buffer for a long period to ensure capture of trouble-related information, then the reliability of trouble analysis improves, but the likelihood of buffer overflow and data loss increases
Solution Approach 1:
The system segments the buffer into multiple regions or categories, allocating different retention periods and priorities to different types of data. Critical trouble-related data receives longer retention and higher priority, while less critical data is managed with shorter retention periods, preventing buffer overflow while maintaining analysis reliability.
Solution Approach 2:
The system introduces an intermediary data management layer between data collection and storage. This intermediary selectively manages data flow, prioritizing preservation of trouble-related information while managing overall buffer usage to prevent overflow, thus protecting against data loss.
Data Source
AI summary
A programmable logic controller or a PLC includes a collector that repeatedly collects, from a device memory, a value varying depending on control of a device, a buffering device that stores, into a buffer, a set of data indicating the value collected at a timing corresponding to satisfaction of a buffering condition, and a logger that reads the set of data from the buffer upon a logging condition being satisfied and stores the set of data into a storage as a set of log data. The buffering device discards the set of data stored in the buffer upon another predetermined condition different from the buffering condition and the logging condition being satisfied.