PLC Ladder Path Analysis for Automated Coverage Recording
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Solution Overview
Problem
In ladder language used in PLC, it is difficult to record coverage of execution paths due to the need for manual management of multiple routes and visual confirmation of coil conditions, which complicates the recording process.
Innovation Solution
An analysis device with a path analysis unit, contact point combination acquisition unit, and path output unit that automatically analyzes and outputs execution paths of a ladder program without manual operation, using a control unit to perform logical operations and display results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ladder program coverage recording is performed manually by managing multiple routes in separate files, then coverage information can be recorded, but the operation complexity and time consumption increase significantly
Solution Approach 1:
The system automatically performs coverage recording by having the PLC execute the ladder program and self-report execution status. The coverage recording unit automatically captures which instructions were executed based on the program counter information returned by the PLC, eliminating the need for manual tracking of multiple execution routes.
Solution Approach 2:
The patent replaces manual mechanical operations (operators physically tracking and recording coverage in separate files) with an automated electronic system. The PLC's program counter and the coverage recording unit work together to automatically generate coverage data, substituting human labor with automated data collection and processing.
2Measurement precision
If conversion to general-purpose language program is performed to improve coverage recording, then coverage can be measured, but the device complexity and loss of original program characteristics increase
Solution Approach 1:
Instead of converting the original ladder program to general-purpose language, the patent creates a simplified copy or representation of the ladder program's control flow. The coverage recording unit maintains a model of the ladder program's instruction sequence and uses the program counter to track execution, preserving the original program while enabling coverage measurement.
Solution Approach 2:
The patent makes the PLC system multi-functional by enabling it to both execute the ladder program and simultaneously provide coverage recording capabilities. The PLC's existing program counter and status flags are leveraged to serve dual purposes: normal program execution and coverage data generation, eliminating the need for separate analysis systems.
3Measurement precision
If visual confirmation of coil conditions is required to confirm coverage, then coverage accuracy can be verified, but the ease of operation decreases
Solution Approach 1:
The system implements automated feedback by having the PLC return program counter information and execution status to the coverage recording unit after each scan cycle. This automatic feedback loop provides continuous verification of which instructions were executed without requiring manual visual inspection of coil conditions or program state.
Solution Approach 2:
The PLC system performs self-verification by automatically tracking its own execution state through the program counter. The coverage recording unit simply collects this self-reported information from the PLC, eliminating the need for external manual verification of coil conditions or program execution state.
Data Source
AI summary
The purpose of the present invention is to easily measure the execution path of a ladder program without manual work by an operator.The present Invention provides an analysis device provided with: a path analysis unit for analyzing each path of a ladder program circuit; a contact point combination acquisition unit for acquiring combinations of contact points for analyzed paths, and a path output unit for outputting a path on the basis of a calculation result of a condition value for each combination.