Distributed Control Node Lockstep Error Detection
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Solution Overview
Problem
Open architecture process automation systems (PAS) in plant facilities face challenges in achieving high reliability and availability due to the arbitrary combination of hardware and software from different manufacturers, leading to potential errors and increased costs, especially when handling a large number of Input/Output (I/O) devices.
Innovation Solution
A management system comprising a distributed control node (DCN) with a lockstep microprocessor unit that compares control values calculated by multiple processors to detect errors, ensuring accurate operation and preventing propagation of errors to other control loops, while maintaining compatibility with general-purpose hardware and software.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an open architecture platform with general-purpose hardware and software is used, then cost is reduced and scalability is enhanced, but reliability of core components deteriorates
Solution Approach 1:
The system segments the control architecture into multiple independent control nodes, each handling specific control loops. This segmentation isolates errors to individual nodes, preventing propagation across the entire system while maintaining open architecture benefits of cost-effectiveness and scalability.
Solution Approach 2:
The system implements preliminary error detection mechanisms within each control node before errors can propagate. By detecting and containing errors at the source through predefined safety protocols and validation checks, the system maintains high reliability without requiring proprietary hardware, thus resolving the contradiction between cost and reliability.
2Productivity
If the number of I/O devices connected to a single controller increases, then productivity is improved, but reliability deteriorates due to error propagation risk
Solution Approach 1:
The system divides the control facility into multiple distributed control nodes, each managing a subset of control loops and I/O devices. This segmentation allows the system to handle a large total number of devices across multiple nodes while limiting error propagation to individual nodes, thus maintaining both high productivity and reliability.
Solution Approach 2:
Each control node is designed with localized error containment capabilities, where errors are detected and isolated at the node level. This local quality approach allows each node to operate independently with its own reliability safeguards, enabling the overall system to scale to handle thousands of devices while maintaining high reliability through localized error management.
Data Source
AI summary
A management system for a plant facility is disclosed. The system includes a first field device that measures a process value, a first control node that calculates a first control value based on the process value, a second field device that operates according to the first control value, and an application node that configures one or more parameters for calculating the first control value. The first control node compares the first control value with a second control value calculated by one of the first field device, a second control node, and the application node. When determining that the first and the second control value are identical, the first control node sets the first control value to the second field device.