Adjusting Control Loop Timing via Scheduler Signal Delay Compensation
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Solution Overview
Problem
Process control systems face challenges in timely response to input changes due to transmission delays caused by hardware and software layers, dynamic network loading, and changes in process control equipment, leading to unreliable control loops.
Innovation Solution
An automated method and apparatus that adjust the timing of input signals to ensure they are received within a scheduled time period by using a scheduler to determine the timing of subsequent input signals based on when the previous signal was received, thereby minimizing delays and maintaining control loop efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If input signals are transmitted through hardware and software layers and communication paths, then the control system can process and control multiple field devices, but transmission delays occur causing input signals to be received outside scheduled time periods
Solution Approach 1:
The scheduler determines the expected arrival time of input signals in advance and adjusts output signal timing proactively before the delay problem affects control loop performance. By calculating timing adjustments based on known communication path delays, the system prepares compensation measures ahead of time, ensuring signals are received within scheduled time periods despite transmission delays through hardware and software layers
2Stability of the object's composition
If the control loop operates with fixed timing schedules, then control calculations can be performed systematically, but dynamic changes in process control equipment cause signals to arrive outside scheduled time periods
Solution Approach 1:
The system monitors the actual arrival time of input signals and uses this feedback information to dynamically adjust output signal timing. The scheduler compares expected arrival times with actual reception times, detecting deviations caused by dynamic changes in process control equipment. This feedback mechanism allows the control loop to maintain stability while adapting to equipment changes, automatically compensating for timing variations without manual intervention
Solution Approach 2:
The control system transitions from fixed static timing schedules to dynamic adaptive timing adjustment. The scheduler continuously modifies output signal timing based on real-time observations of input signal arrival patterns, allowing the control loop to adapt its timing characteristics in response to changing system conditions and equipment dynamics while maintaining overall control stability
3Measurement precision
If manual adjustments are made to control loop timing, then specific timing issues can be addressed, but the system requires continuous manual intervention and cannot adapt to dynamic changes automatically
Solution Approach 1:
The scheduler automatically determines and adjusts timing parameters without requiring manual intervention. The system self-monitors input signal arrival times, self-calculates the necessary timing adjustments, and self-implements the corrections by modifying output signal timing. This automated self-service mechanism maintains precise timing accuracy while eliminating the need for continuous manual adjustment, allowing the control loop to adapt dynamically to changing conditions
Data Source
AI summary
Example methods and apparatus to adjust control loop timing in a process control system are disclosed. A disclosed example method includes receiving a first input signal generated via a first process control device within a process control system, determining within the process control system if the first input signal is received during a first scheduled time period of a control loop, and adjusting within the process control system a timing of a subsequent input signal received from the first process control device to cause the subsequent input signal to be received during a subsequent scheduled time period of the control loop, wherein the timing of the subsequent input signal is based on at least when the first input signal was received.