Regulator Over-Integration Elimination for Saturation Hunting
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Solution Overview
Problem
Conventional regulators experience hunting phenomena and reset-windup issues during saturation, leading to overshoots and undershoots, especially when the target value varies in a stepwise manner, and fail to eliminate over-integration effectively.
Innovation Solution
A regulator is designed with an over-integration computing section that eliminates previous over-integration in subsequent control cycles, stabilizing the limited operation signal by correcting integral values and preventing hunting phenomena.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the regulator stops integral actions to prevent limit deviation signal expansion during saturation, then the reset-windup is prevented, but the over-integration produced during the saturation cycle cannot be eliminated, causing hunting phenomenon and repeated saturation-desaturation
Solution Approach 1:
The regulator performs preliminary action by detecting saturation occurrence and proactively eliminating the over-integration that would be produced during the saturation cycle, before the hunting phenomenon can occur. This is achieved by monitoring the operation signal against limit values and preemptively correcting the integral term when saturation is detected.
Solution Approach 2:
The regulator uses feedback by continuously monitoring the operation signal and comparing it with predetermined limit values. When saturation is detected through this feedback mechanism, the system responds by eliminating the over-integration in the subsequent control cycle, thereby preventing the hunting phenomenon while maintaining reliability.
2Reliability
If the speed-type integration regulating signal is made zero to prevent limit deviation signal expansion, then saturation is prevented, but over-integration remains corresponding to the magnitude of target value variations, causing overshoot or undershoot upon recovery
Solution Approach 1:
The regulator extracts and eliminates only the harmful over-integration component that was produced during the saturation cycle, while preserving the necessary integral action for normal operation. This selective removal prevents saturation recovery issues without compromising the precision needed for accurate control.
Solution Approach 2:
The regulator dynamically changes the integral term parameter by eliminating the over-integration portion when saturation is detected. This parameter adjustment allows the system to maintain precision upon recovery from saturation while preventing the harmful effects of accumulated over-integration.
3Reliability
If conventional anti-reset-windup processing is applied, then the limit deviation signal expansion is prevented, but hunting phenomenon occurs in the initial state of saturation with relatively small number of limit deviation signals
Solution Approach 1:
The regulator applies preliminary anti-action by detecting the initial state of saturation and proactively eliminating the over-integration before the hunting phenomenon can develop. This preemptive correction prevents the repeated saturation-desaturation cycles that characterize the hunting phenomenon.
Solution Approach 2:
The regulator uses feedback monitoring to detect when saturation occurs with a relatively small number of limit deviation signals. Upon detecting this specific condition, the system responds by eliminating the over-integration in the subsequent control cycle, thereby preventing the hunting phenomenon while maintaining the benefits of conventional anti-reset-windup processing.
Data Source
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AI summary
A regulator 1 includes a regulation computing section 14 for computing and outputting an operation signal MV[n] to allow a process value PV from a controlled target 2 to agree with a target value SV, and an output limiting section 15 for restricting the operation signal MV[n] from the regulation computing section 14 for output to the controlled target 2. The regulation computing section 14 includes at least a speed-type integration regulating section or a position-type integration regulating section. The output limiting section 15 includes a function for outputting a limit deviation signal δ[n] indicative of the degree of deviation from a predetermined limit. The regulator 1 also includes an over-integration computing section 16 for calculating a previous over-integration signal corresponding to a previous over-integration occurred during a previous control cycle on the basis of the speed-type integration regulating signal delivered by the regulation computing section 14 and the limit deviation signal δ[n]. The regulation computing section 14 includes a function for allowing the previous over-integration signal to eliminate the previous over-integration by correcting an integral stored in itself.