2DoF Controller Tuning via Control-Error Anomaly Detection

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Solution Overview

Problem

Two Degree of Freedom (2DoF) controllers face challenges in maintaining accuracy and robustness due to changes in the system, such as disturbances, wear, or nonlinearities, leading to incorrect control actions and potential system endangerment.

Innovation Solution

Anomaly detection is implemented to derive an anomaly detection signal from the control error, allowing adaptation of control parameters in a 2DoF controller to address deviations, with flexibility in model usage and output limitation to enhance accuracy and safety.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a Two Degree of Freedom controller uses an inverse model in the feedforward part, then reference tracking performance is improved, but robustness deteriorates when the system changes due to disturbances, wear, or nonlinearities

Engineering Contradiction:
Improvereference tracking performanceVSAvoidrobustness
Core Design Contradiction:
Measurement precisionVSReliability

Solution Approach 1:

The controller dynamically adapts its parameters based on real-time system behavior. The tuning parameter is continuously adjusted according to the control error signal, allowing the controller to transition between relying on the feedforward inverse model and relying on feedback, thereby maintaining both tracking performance and robustness against system changes

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

A feedback mechanism is introduced where the control error is used to detect anomalies and trigger parameter adaptation. When the control error exceeds a threshold, the tuning parameter is modified to increase feedback contribution, compensating for model inaccuracies and maintaining reliability despite system variations

Inventive Principle:
Principle #23Feedback

2Measurement precision

If controller parameters are tuned to achieve desired control behavior, then control accuracy is improved, but device complexity increases

Engineering Contradiction:
Improvecontrol accuracyVSAvoidcontroller complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The invention modifies the controller parameters dynamically based on system performance. A tuning parameter is introduced that can be adjusted in real-time according to the control error, allowing the controller to adapt to system changes without requiring complex manual retuning or multiple fixed parameter sets

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The controller performs self-adjustment by using its own control error signal to detect anomalies and automatically modify its tuning parameter. This self-service capability eliminates the need for external intervention or complex parameter tuning procedures, maintaining simplicity while improving accuracy

Inventive Principle:
Principle #25Self-service

Data Source

PatentEP4686985A1Control method and control device with anomaly detection
Publication Date: 2026.02.04 ABB (SCHWEIZ) AG
  • EP4686985A1 patent drawingFigure 1~5
  • EP4686985A1 patent drawingFigure 2
  • EP4686985A1 patent drawingFigure 3a~3b

AI summary

In order to provide a method for controlling a technical system (1) by means of a Two Degree of Freedom controller (2), which allows for increased accuracy, higher robustness and better safety even in cases of changes of the technical system (1), at an anomaly detection time point (tw) during control of the technical system (1), an anomaly detection signal (w) is derived, at least one control parameter (kp, ki, umax) parametrizing the Two Degree of Freedom controller (2) is adapted depending on the anomaly detection signal (w) and, from the anomaly detection time point (tw) onwards, the technical system (1) is controlled by means of the Two Degree of Freedom controller (2) parameterized by said at least one adapted control parameter (kp, kj, umax).