PLC Log Retention Using Triggered Recording and Selective Erasure
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Solution Overview
Problem
The existing technique for recording log data in factory automation systems faces limitations due to the capacity constraints of temporary recording units and storage memory, leading to potential data loss and difficulties in investigating causes of trouble.
Innovation Solution
A programmable controller that collects data, records it when a first trigger condition is met, adds additional information when a second trigger condition is satisfied, and erases secondary data to retain primary data, thereby managing storage capacity and retaining essential data for investigation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the temporary recording unit capacity is increased to store more log data for longer periods, then the ability to investigate trouble causes is improved, but the device complexity and cost increase
Solution Approach 1:
The patent divides the storage system into two distinct segments: a temporary recording unit (ring buffer) for short-term data collection and a storage memory for long-term archival. This segmentation allows each component to be optimized for its specific function, avoiding the need for a single large-capacity storage device while maintaining the ability to retain essential log data for trouble investigation.
Solution Approach 2:
The system performs preliminary recording of log data in the temporary recording unit before transferring selected data to storage memory. This preliminary action ensures that data is captured immediately when recording triggers occur, preventing data loss while allowing selective transfer to long-term storage based on trigger conditions, thus avoiding the need for continuously large storage capacity.
2Loss of information
If the storage memory capacity is increased to retain more historical log data, then the investigation capability is improved, but the cost and device complexity increase
Solution Approach 1:
The patent applies local quality by selectively transferring only certain log data to storage memory based on specific trigger conditions, rather than uniformly storing all data. This allows the storage memory to maintain sufficient capacity for important historical data while avoiding saturation from unnecessary data, thus reducing the required storage capacity while maintaining investigation capability.
Solution Approach 2:
The system discards log data from the temporary recording unit after successful transfer to storage memory, recovering the temporary storage space for continuous operation. This cyclic process allows the storage memory to accumulate historical data over time without being constrained by the limited capacity of the temporary recording unit, effectively increasing retained data volume without proportionally increasing total storage capacity.
3Reliability
If the temporary recording unit capacity is increased to prevent data overwriting, then data loss is reduced, but the ease of operation and system simplicity deteriorate
Solution Approach 1:
The patent implements a dynamic data transfer mechanism where the timing and selection of data transfer from temporary recording unit to storage memory is determined by runtime trigger conditions rather than fixed capacity limits. This dynamic approach allows the system to maintain data integrity by transferring data based on operational events, eliminating the need for oversized temporary storage while preserving reliability.
4Quantity of substance
If selective erasure of log data is implemented to manage storage space, then storage capacity utilization is improved, but the difficulty of detecting and measuring essential data increases
Solution Approach 1:
The system performs preliminary marking of log data with identification information before transfer to storage memory, based on trigger conditions. This preliminary action ensures that essential data can be easily identified and retrieved later, even after selective erasure of other data from the temporary recording unit, thus reducing the difficulty of detecting essential data while enabling effective storage space management.
Data Source
AI summary
A PLC includes a data collector to repetitively collect data variable depending on control of a machine from a device memory, a recorder to record data collected by the data collector at a timing corresponding to satisfaction of a predetermined first trigger condition into a storage when the first trigger condition is satisfied, an information adder to add additional information to at least one of first data, recorded by the recorder into the storage, or second data, collected by the data collector after the first data and recorded by the recorder into the storage, when a second trigger condition different from the first trigger condition is satisfied, and an eraser to erase the second data from the storage while retaining the first data in the storage on the basis of the additional information after recording of the first and second data into the storage.