Controller Parameter Update Method for Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional automatic adjustment technologies for controllers destabilize control systems, leading to unstable responses.
Innovation Solution
A parameter update method that calculates the variable parameter of a controller to minimize an evaluation function, which includes a first function to adjust the control output and a second function to prevent significant changes in the transfer function's frequency characteristics, ensuring system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional automatic adjustment technologies (FRIT or VRFT) are used to adjust the controller parameter to obtain target response, then the control output corresponds to the target response, but the control system becomes unstable and the response disperses
Solution Approach 1:
The patent changes the parameter optimization approach from directly minimizing output error (conventional FRIT/VRFT) to minimizing a composite evaluation function that includes both output error and transfer function deviation. This parameter change in the objective function prevents instability by constraining how much the controller parameters can change, thereby resolving the contradiction between achieving target response accuracy and maintaining system stability.
Solution Approach 2:
The patent introduces an intermediary evaluation function that mediates between the target response requirement and system stability. This evaluation function includes two components: one measuring output error and another measuring transfer function deviation. The intermediary function balances both requirements, allowing the system to achieve accurate control output while preventing instability, thus resolving the contradiction.
2Productivity
If the variable parameter is adjusted to minimize output error, then the control performance improves, but the transfer function characteristics change significantly causing instability in critical frequency bands
Solution Approach 1:
The patent modifies the parameter adjustment strategy by changing the optimization objective from purely minimizing output error to minimizing a composite function that penalizes significant changes in transfer function characteristics. This parameter change ensures that controller parameters are adjusted to improve control performance while maintaining stability in critical frequency bands, resolving the contradiction between productivity and stability.
Solution Approach 2:
The patent applies local quality by focusing on maintaining stability in specific critical frequency bands rather than uniformly across all frequencies. The evaluation function includes a transfer function deviation component that specifically protects critical frequency bands from excessive parameter changes, allowing control performance improvement in non-critical bands while preserving stability where it matters most.
Data Source
AI summary
There is provided a method of updating a setting value of a variable parameter, the method including: obtaining a time-series data of control input and a time-series data of control output observed in control with a controller; calculating a value of the variable parameter which minimizes an output value of an evaluation function based on the obtained time-series data of the control input and the control output; and updating the setting value of the variable parameter to the calculated value of the variable parameter. The evaluation function includes a first function part in which a first norm or a second norm changes depending on the value of the variable parameter, and a second function part of which specific frequency band has an amount, by which the output value of the evaluation function is increased, larger than that of any other frequency band.