PLC Sequence Tracking Across Multiple Control Devices
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Solution Overview
Problem
Existing Programmable Logic Controller (PLC) systems struggle to trace and identify the cause of sequence, input, or output deviations due to the lack of memory for sequence information, particularly in complex systems with multiple interdependent devices.
Innovation Solution
A control system performance tracking apparatus with a data memory device that monitors and timestamps data from multiple control devices, compiling a time-based sequence data stack for each device, and includes a processor to analyze and visualize this data, enabling advanced data processing and diagnostic capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PLC systems operate on a logic switch basis without maintaining sequence information in memory, then real-time control reliability is improved, but the ability to trace and identify sequence deviations is worsened
Solution Approach 1:
The system separates the PLC control function from the sequence monitoring function. The PLC continues to operate purely as a real-time controller without memory burden, while an external monitoring system captures and stores sequence information separately. This segmentation allows both real-time reliability and sequence traceability to coexist.
Solution Approach 2:
An intermediary monitoring system is introduced between the PLC and the user/diagnostic tools. This intermediary captures sequence information from the PLC's inputs and outputs, maintains the sequence data in its own memory, and provides traceability capabilities without modifying the PLC's core control function.
2Adaptability or versatility
If multiple PLCs are arranged in a networked configuration to control interdependent devices, then system versatility is improved, but the difficulty of detecting and measuring sequence deviations is worsened
Solution Approach 1:
The monitoring system merges data from multiple PLCs into a unified sequence record. By consolidating inputs, outputs, and events from all PLCs in the network into a single time-stamped data stream, the system simplifies the detection of sequence deviations across interdependent devices while maintaining the versatility of the networked configuration.
Solution Approach 2:
The system adds a temporal dimension to the monitoring by implementing time-stamping of all sequence events. This allows sequence deviations to be detected and measured in the time domain, providing a clear chronological record that simplifies analysis of complex multi-PLC interactions.
3Device complexity
If PLC systems use standard memory architecture without external data logging, then device complexity is reduced, but the capability for predictive analysis is worsened
Solution Approach 1:
The data logging and historical storage functions are extracted from the PLC itself and placed in an external system. The PLC maintains its simple memory architecture for real-time control, while the external monitoring system captures and stores historical sequence data for later analysis and predictive capabilities.
Solution Approach 2:
The monitoring system creates a copy of the PLC's operational data (inputs, outputs, events) and stores it separately. This copying approach allows historical data to be preserved for predictive analysis without adding complexity to the original PLC system, as the PLC continues to operate with its standard memory architecture.
Data Source
AI summary
The present invention relates to a control system performance tracking apparatus comprising: a data memory device coupled in use to a plurality of control devices of a control system, the data memory device being configured to: monitor the plurality of control devices; receiving data related to inputs, outputs and events of each control device; time stamp said data on a common time base; and store a resulting time-based sequence data for each of the plurality of control devices; and a processor configured to compile the sequence data for the plurality of control devices into a common data stack.