Non-periodic Controller Setpoint Compensation Filter
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Solution Overview
Problem
Wireless process control systems with non-periodic measurement updates struggle to respond robustly to setpoint changes due to reliance on outdated process responses, leading to inefficient control dynamics.
Innovation Solution
A continuously updated filter within the controller generates a new indication of the expected process response during each control routine iteration, using a previously generated indication when new measurement updates are unavailable, ensuring the controller accurately compensates for setpoint changes and feed-forward disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If non-periodic measurement updates are used to reduce communication overhead and energy consumption, then energy efficiency improves, but control accuracy deteriorates due to reliance on outdated process responses
Solution Approach 1:
The filter continuously generates predictions of the process response in advance before new measurements are received. This preliminary action allows the controller to maintain accurate control signals during intervals between measurements by using the filtered predictions, thus resolving the contradiction between reduced communication frequency and maintained control accuracy.
2Loss of time
If measurement update frequency is reduced for wireless communication efficiency, then communication overhead decreases, but responsiveness to setpoint changes worsens
Solution Approach 1:
The filtering mechanism provides continuous feedback about the expected process response based on previous measurements and control actions. This feedback loop allows the system to respond quickly to setpoint changes by predicting the process behavior, maintaining responsiveness even when actual measurement updates are infrequent.
3Duration of action of stationary object
If the controller relies on outdated process responses to maintain operation between measurements, then system continuity is maintained, but control performance deteriorates
Solution Approach 1:
The filter acts as an intermediary between the discrete measurements and the continuous control requirements. It processes the outdated measurements and generates smoothed predictions that bridge the time gaps, allowing the controller to maintain both continuity of operation and acceptable control performance during intervals between measurements.
Data Source
AI summary
A technique for controlling a process using non-periodically received process variable measurements enables more robust controller responses to setpoint changes. The control technique implements iterations of a control routine to generate a control signal using a reset or rate contribution component that produces an expected process response to the control signal. When a new measurement of the process variable is unavailable to the controller, the reset or rate contribution component that was generated in response to the receipt of the previous process variable is maintained when generating the control signal. However, the reset contribution component is iteratively recalculated during each controller execution cycle so that the output of the reset contribution component incorporates expected process changes that occur as a result of a setpoint change.