PLC Time-Stamped Data Correlation for Monitoring Debugging
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Solution Overview
Problem
In the field of programmable logic controllers (PLCs), it is challenging to specify the time relationship between device values and data input from various monitoring apparatus, such as cameras, sensors, and communication controllers, due to differing update and scan cycles, making it difficult to identify related data and troubleshoot issues effectively.
Innovation Solution
A programmable logic controller system is designed with a first external interface for receiving user programs and setting information, a program executing section, a device storing section, a first collecting section for device values, and a second external interface for monitoring apparatus data, which collects and associates data with their respective acquisition times in buffers, allowing for easy correlation and saving when predetermined conditions are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If data from monitoring apparatus (e.g., camera, sensor) is collected separately from device values, then data acquisition flexibility is improved, but time correlation between device values and monitoring data becomes difficult to specify
Solution Approach 1:
The patent introduces a time stamp as an intermediary element that mediates between the device value collecting section and the monitoring apparatus data collecting section. Both sections independently add time stamps to their respective data, enabling time correlation to be established without requiring direct synchronization between the different data acquisition processes. This allows separate data collection while preserving time relationship information.
2Productivity
If device values are collected at scan cycle intervals, then PLC control functionality is maintained, but synchronization with monitoring data acquired at different cycles becomes difficult
Solution Approach 1:
The patent changes the parameter of time representation by introducing time stamps that record actual acquisition timing. Instead of relying on fixed cycle synchronization, each data point (device value or monitoring data) is tagged with its precise acquisition time, allowing reliable correlation regardless of different acquisition cycles. This enables maintaining standard PLC scan cycles while achieving accurate data synchronization.
3Device complexity
If multiple data sources are collected independently, then system complexity is reduced, but troubleshooting and debugging become more difficult due to inability to correlate data
Solution Approach 1:
The time stamp acts as a mediator that enables troubleshooting without increasing system complexity. By independently adding time stamps to each data source and then correlating data based on these time stamps, the system maintains simple independent data collection while enabling easy troubleshooting through time-based data association. Users can easily identify which device value corresponds to which monitoring data point.
Data Source
AI summary
A PLC collects a device value stored in any one of a plurality of devices and stores information relating to collecting time at which the device value is collected and the device value in association with each other in a first buffer. The PLC collects data input from a monitoring apparatus and stores information relating to acquiring time at which the data is acquired and the data in association with each other in a second buffer. A saving section saves, when a predetermined saving condition is satisfied, the device value and the information relating to the collecting time stored in the first buffer, and the data and the information relating to the acquiring time stored in the second buffer in correspondence with each other.