Modular Network Node Timing for Earlier Control Output
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Solution Overview
Problem
In Distributed Control Systems (DCS), large-capacity control nodes often execute control loops with fixed periods that are not perfectly aligned with the process control time-constants, leading to reduced control quality due to delayed output transmission to I/O modules and field devices, which can be costly and inefficient.
Innovation Solution
A modular network node system with a control module and SSIO/UIO modules that allow for flexible I/O type selection and time-strobe synchronization, enabling earlier output transmission and improved alignment with process control time-constants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large-capacity control nodes execute control loops with fixed periods, then control cycles can be managed, but control quality is reduced due to delayed output transmission to I/O modules and field devices
Solution Approach 1:
The control node is divided into multiple control modules, each capable of independent control execution. This segmentation allows different control loops to be executed with different sampling periods optimized for their specific process time-constants, rather than using a single fixed period for all loops. Each module can transmit outputs independently, reducing delays.
Solution Approach 2:
The system transitions from static fixed-period control to dynamic adaptive control where sampling periods can be adjusted based on process conditions and specific loop requirements. Control modules can dynamically modify their execution intervals to match changing process time-constants, improving control quality while reducing unnecessary delays.
2Productivity
If control nodes are filled to near capacity to maximize cost effectiveness, then resource utilization is optimized, but control outputs are delayed until near the end of the control cycle
Solution Approach 1:
By segmenting the control node into multiple independent control modules, each module can operate with its own optimized timing and resource allocation. This allows the system to maintain high overall utilization while individual modules can transmit outputs at optimally timed intervals rather than all waiting for cycle completion.
Solution Approach 2:
Control outputs are transmitted earlier in the control cycle by allowing modules to complete their execution and send outputs before the cycle ends. This preliminary transmission of control outputs to I/O modules and field devices reduces the elapsed time for control action to take effect.
3Ease of operation
If fixed period control is used, then control execution is simplified, but the control period is not perfectly aligned with process control time-constants
Solution Approach 1:
The system allows control periods to be dynamically adjusted for different control modules based on the specific time-constants of the processes they control. Each module can be configured with an optimized sampling period that matches its process requirements, maintaining simplicity while achieving precise alignment.
Solution Approach 2:
The sampling period parameter can be changed and optimized for each control module independently. This allows the system to maintain the simplicity of fixed-period execution while adjusting the period value to perfectly align with different process time-constants for different control loops.
Data Source
AI summary
Methods and Systems are described for control at/of a network node. The network node can include a control module and first and second modules coupled to the control module. The first module can be configured to select first input/output (I/O) types of a field device coupled at an I/O interface of the network node. The second module can be configured to select a second I/O types of the field device. The first and second modules can be coupled to the I/O interface through a field device coupler.