Material Testing Force Control Using Elongation-Based Estimation
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Solution Overview
Problem
In material testing machines, increasing feedback gain for improved responsiveness amplifies noise, leading to unstable control, and using low-pass filters to reduce noise delays the detection signal and decreases stability.
Innovation Solution
A material testing machine with a load mechanism, first and second monitor amount measurement units, a monitor amount conversion unit, and a material test control unit that determines operation amounts based on correlation conditions to reduce deviations between actual and target monitor amounts, using a control stiffness calculation to improve feedback control stability and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If feedback gain is increased to improve responsiveness, then responsiveness is improved, but noise component is amplified and control stability deteriorates
Solution Approach 1:
The patent introduces a monitor amount conversion unit that converts the first monitor amount (measured by the first measurement unit) into a second monitor amount estimation value that serves as a substitute for the second monitor amount (measured by the second measurement unit). This intermediary conversion process allows the feedback control to use the first monitor amount with higher signal quality, thereby maintaining control stability while achieving responsive control performance.
Solution Approach 2:
The patent changes the parameter used for feedback control from directly using the second monitor amount (which contains noise) to using the second monitor amount estimation value derived from the first monitor amount (which has better signal quality). This parameter change enables the system to maintain high feedback gain for responsiveness while avoiding noise amplification through the conversion process.
2Reliability
If low-pass filter is used to reduce noise component, then noise is reduced, but detection signal is delayed and control stability deteriorates
Solution Approach 1:
Instead of using a low-pass filter that delays the signal, the patent uses a monitor amount conversion unit that converts the first monitor amount into a second monitor amount estimation value. This conversion process does not introduce time delay while still achieving noise reduction, as it uses the correlation between the first and second monitor amounts to generate an accurate estimation without filtering the original signal.
3Measurement precision
If second monitor amount measurement unit is used to measure testing force, then measurement is obtained, but noise component is superimposed and measurement precision deteriorates
Solution Approach 1:
The patent introduces a monitor amount conversion unit that converts the first monitor amount (which has better signal quality) into a second monitor amount estimation value. This estimation value serves as an intermediary that replaces the noisy direct measurement from the second monitor amount measurement unit, thereby achieving precise testing force measurement without noise contamination.
Solution Approach 2:
The patent creates a copy of the second monitor amount information through the second monitor amount estimation value, which is derived from the first monitor amount. This copied information has the same functional purpose as the direct measurement but with superior signal quality, effectively replacing the noisy original measurement in the feedback control process.
Data Source
AI summary
Provided are a material testing machine that can improve the responsiveness and the stability and perform a feedback control for a test condition, and a method for controlling a material testing machine. A monitor amount conversion unit (23) calculates an estimation testing force by multiplying an elongation amount measured by an elongation amount measurement unit (22) by a control stiffness of a test piece (TP). A material test control unit (24) determines an operation amount for a servo motor (43) for reducing a deviation between an actual testing force applied to the test piece (TP) and a target testing force according to a test condition based on an estimation testing force, and executes a tensile test for the test piece (TP).