Plant Control System Segmentation for Reliability
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Solution Overview
Problem
Current plant control systems in steelmaking plants face challenges in balancing the high reliability and stability of programmable logic controllers with the superior arithmetic processing ability and ease of software development of general-purpose personal computers, particularly in ensuring punctuality and reliability in industrial applications.
Innovation Solution
A plant control system that divides functions between programmable logic controllers and information processors, where the programmable logic controller executes sequential control logic and the information processor handles complex arithmetic processing, with a consistency check mechanism to ensure the validity of arithmetic result data, thereby enhancing the reliability of the information processor in industrial applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a general-purpose personal computer is introduced into the plant control system to handle arithmetic processing, then the arithmetic processing ability and ease of software development are improved, but the reliability and punctuality in industrial applications deteriorate
Solution Approach 1:
The system divides the control architecture into distinct layers: the upper layer uses a general-purpose personal computer for arithmetic processing and software development, while the lower layer employs a programmable logic controller for real-time control. This segmentation allows each component to specialize in its strength while mitigating its weaknesses through the structured division of labor in the control system.
Solution Approach 2:
The programmable logic controller serves as an intermediary between the general-purpose personal computer and the actual control equipment. It receives arithmetic results from the PC, validates them against predetermined references, and only executes control actions when consistency is confirmed. This intermediary role ensures that the reliability requirements of industrial control are met while still benefiting from the PC's superior arithmetic capabilities.
2Reliability
If the programmable logic controller directly controls all equipment, then the reliability and stability are secured, but the development efficiency of software for complicated arithmetic processing deteriorates
Solution Approach 1:
The system segments software development responsibilities: the general-purpose personal computer handles complicated arithmetic processing and convergent arithmetic algorithms, while the programmable logic controller manages real-time control logic. This segmentation enables software to be developed more efficiently on the PC platform while maintaining the reliability of the PLC for critical control functions.
Solution Approach 2:
The programmable logic controller acts as an intermediary that validates arithmetic results from the personal computer against predetermined references before execution. This intermediary validation mechanism enables the use of more sophisticated software on the PC side without compromising the reliability and stability required for industrial control applications.
3Productivity
If the general-purpose personal computer is directly connected to control equipment, then the arithmetic processing ability is improved, but the risk of causing troubles and reliability issues increases
Solution Approach 1:
The programmable logic controller serves as a protective intermediary between the general-purpose personal computer and the control equipment. It validates arithmetic results by comparing them against predetermined references and only permits execution when consistency is confirmed. This intermediary validation layer significantly reduces the risk of troubles caused by erroneous arithmetic results while preserving the high arithmetic processing ability of the PC.
Solution Approach 2:
The system implements beforehand cushioning by establishing predetermined references and validation rules in advance within the programmable logic controller. These pre-established validation mechanisms cushion against potential errors from the personal computer's arithmetic processing, preventing harmful effects before they can impact the control equipment.
Data Source
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AI summary
A plant control system includes a process computer (1) managing a plant, a PLC (2) interposed between the process computer (1) and equipment (3) of the plant, and a general-purpose PC (7) executing arithmetic processing based on arithmetic data received from the PLC (2) and transmitting arithmetic result data thereof to the PLC (2). The functions are divided such that sequential control logic is executed by the PLC (2) and complicated arithmetic processing is executed by the general-purpose PC (7), and the arithmetic result data outputted from the general-purpose PC (7) always passes through the PLC (2) so that consistency of the arithmetic result data is checked in the PLC (2). This makes it possible to apply a general-purpose personal computer (general-purpose PC) to the plant control system so as to divide the functions between the programmable logic controller (PLC) and the general-purpose PC and to compensate the reliability of the general-purpose PC in an industrial application, for example, in terms of punctuality.