Adaptive Scanner for Process Control
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Solution Overview
Problem
Conventional process control systems in industrial plants face challenges with fixed scan periods in shared communications channels, leading to inadequate monitoring during rapid changes in process parameters, potential safety issues, and reduced performance due to communication errors, especially in tank loading/unloading and when data approaches critical thresholds.
Innovation Solution
Implementing an adaptive scan period determination algorithm in a communications device that adjusts scan periods based on specific parameters such as data type, communication methods, and operational events, allowing for dynamic scanning to prioritize critical measurements and optimize bandwidth usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed scan period is used for polling field devices, then the communications device can operate with simple timing control, but the monitoring accuracy deteriorates during rapid process changes
Solution Approach 1:
The patent implements dynamic scan periods that automatically adjust based on process conditions. When rapid changes are detected (such as during tank loading/unloading or when parameters approach critical thresholds), the scan period decreases to increase monitoring frequency. This resolves the contradiction by making the scan period adaptive rather than fixed, improving monitoring accuracy during critical events while maintaining operational simplicity through automated adjustment.
2Measurement precision
If the scan period is decreased to improve monitoring accuracy during critical events, then the monitoring accuracy improves, but the bandwidth consumption increases
Solution Approach 1:
The system dynamically adjusts scan periods based on process conditions, using shorter periods only when necessary (during rapid changes or critical events) and longer periods during stable operations. This resolves the contradiction by making bandwidth consumption adaptive - high monitoring accuracy is achieved only when process conditions require it, while bandwidth is conserved during normal stable operations.
Solution Approach 2:
The patent changes the scan period parameter based on process conditions, transitioning between different scan rates according to the state of the monitored parameters. This allows the system to optimize the balance between monitoring accuracy and bandwidth consumption by adjusting the scan period parameter in response to actual process needs rather than maintaining a constant value.
3Reliability
If the communications device retries communication with non-communicating field devices, then the reliability of data collection is improved, but the scanning performance deteriorates due to repeated retries
Solution Approach 1:
The patent implements dynamic adjustment of retry behavior based on process conditions. During stable operations, the system can afford to perform retries to maintain data collection reliability. However, during rapid process changes or critical events, the system prioritizes scanning current process state over retrying failed communications, temporarily reducing retry activity to maintain overall scanning performance.
Solution Approach 2:
The system uses feedback from process conditions to adjust communication retry behavior. When process parameters indicate stable conditions, retry mechanisms are activated to improve data collection reliability. When parameters indicate rapid changes or critical events, the feedback triggers a shift in priority toward current state monitoring, temporarily suppressing retry operations to maintain scanning performance.
Data Source
AI summary
A method of process control within a plant includes providing a first and second field device associated with processing equipment sensing a first and second process parameter respectively. The field devices are communicably coupled to a host computer by a communications path including a shared field communications channel portion (shared communications channel) that terminates at a communications device which includes a processor and memory that implements an adaptive scan period determination algorithm (adaptive scanner) which determines a first scan period for the first field device and a second scan period for the second field device each based on a parameter relevant to a data type of the process parameter or communications used. The host computer monitors operations in the plant using sampled data provided by the communications device including data based on the first and second process parameter at their respective scan periods.