PLC I/O Refresh Control for Real-Time Module Output
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Solution Overview
Problem
Conventional PLC systems do not allow for real-time extraction of processing result data during the computing and command control period, as the output image area refresh operation is only performed at the end of each cycle, making it difficult to operate multiple extension modules efficiently.
Innovation Solution
A PLC system that includes an integrated operation program with added input/output refresh execution commands, allowing for real-time output and input refresh operations when each control program is completed, and comparing previous and current cycle results to optimize refresh operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output image area refresh operation is performed only at the end of each PLC service cycle, then the system structure is simple and easy to implement, but the processing result data cannot be extracted in real-time during the computing and command control period
Solution Approach 1:
The patent segments the PLC service cycle into multiple independent refresh operations. Instead of performing a single output image area refresh at the end of the cycle, the system performs intermediate output refresh operations at specific points during the computing and command control period. This segmentation allows real-time data extraction while maintaining a relatively simple control structure by using predefined refresh points.
2Productivity
If intermediate output refresh operations are added during the computing and command control period, then real-time data extraction is enabled, but the control program complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-defining intermediate output refresh points within the PLC service cycle structure. These refresh operations are planned and positioned in advance during the computing and command control period, allowing the system to extract data at predetermined intervals without requiring complex dynamic decision-making during execution. This approach enhances productivity while controlling program complexity through structured pre-planning.
3Adaptability or versatility
If multiple control programs are executed sequentially to control multiple extension modules, then comprehensive control capability is achieved, but processing result data for individual control programs cannot be extracted and identified separately
Solution Approach 1:
The patent introduces an intermediary mechanism in the form of intermediate output refresh operations that occur between the execution of different control programs. These refresh operations serve as mediators that capture and preserve the processing result data of individual control programs before the next program executes. This allows each control program's results to be extracted and identified separately, maintaining adaptability for controlling multiple extension modules while preventing information loss.
Data Source
AI summary
Disclosed are a PLC system, and a method for controlling an input/output refresh period thereof. A PLC system according to an embodiment of the present disclosure comprises: a memory for storing an integrated operation program in which an input/output refresh run command is added and compiled through a program supporter; and a central processing unit which sequentially performs arithmetical processing of a plurality of control programs included in the integrated operation program, to control an operation of a plurality of expansion modules, wherein when arithmetical processing of at least one control program among the plurality of control programs has been completed, the central processing unit outputs processing result data of the at least one control program for which arithmetical processing has been completed, according to an input/output refresh run command which is additionally input.