Chatter Vibration Determination via Multi-Peak FFT Analysis

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Solution Overview

Problem

Existing methods for determining chatter vibration in machine tools, particularly at low rotation speeds and with tools having a small number of flutes, suffer from poor accuracy in distinguishing between 'forced' and 'regenerative' chatter vibrations, and fail to accurately identify 'natural type vibration' due to friction and impact forces.

Innovation Solution

A vibration determination method and device that detects time-domain vibrations, calculates frequency-domain vibrations using FFT analysis, and identifies peak values and frequencies to determine the type of chatter vibration by establishing synchronizing and natural type vibration ranges, excluding frequencies corresponding to rotation and flute-passage periods, thereby improving determination accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If only the maximum value in frequency-domain vibrational acceleration is used for determination, then the determination process is simple, but determination accuracy between forced chatter vibration and regenerative chatter vibration becomes poor at low rotation speeds and with tools having small number of flutes

Engineering Contradiction:

Improvedetermination process complexityVSAvoidchatter vibration type determination accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent segments the frequency-domain vibrational acceleration spectrum into multiple frequency bands and identifies multiple peak values rather than relying on a single maximum value. This segmentation allows for more precise identification of chatter vibration characteristics by analyzing the distribution and relationships of multiple peaks across different frequency ranges, thereby improving determination accuracy while maintaining a systematic analysis approach.

Inventive Principle:

Principle #1Segmentation

2Device complexity

If only the maximum value of frequency-domain vibrational acceleration is used, then the analysis is straightforward, but natural type vibration occurring at natural frequency cannot be determined

Engineering Contradiction:

Improveanalysis complexityVSAvoidnatural type vibration detection capability

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent introduces a new dimension of analysis by examining the frequency distribution pattern and relative positions of multiple peak values in the frequency spectrum, rather than relying solely on the magnitude of the maximum value. This multi-dimensional approach enables the system to distinguish natural type vibrations from other chatter types by analyzing where peaks occur in the frequency domain and how they relate to the natural frequency of the machine tool system.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If the rotation speed is low and tools with small number of flutes are used, then machining flexibility is improved, but the chatter frequency interval becomes dense and determination accuracy deteriorates

Engineering Contradiction:

Improvemachining condition flexibilityVSAvoidchatter frequency discrimination accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent divides the frequency spectrum into multiple segments and identifies multiple peak values across these segments. By analyzing the spatial distribution and relative relationships of these segmented peaks rather than treating the spectrum as a single entity, the system can distinguish between forced and regenerative chatter vibrations even when their frequencies are closely spaced, thereby maintaining determination accuracy under flexible machining conditions.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables more accurate differentiation between types of chatter vibrations, particularly at low rotation speeds and with tools of small flute numbers, and allows for the identification of 'natural type vibration', leading to improved machining accuracy, reduced tool wear, and enhanced manufacturing efficiency.

Implementation Method 1

time-domain vibrational acceleration detected by vibration sensors

Methodology Applied

Scientific EffectVibration: Vibration

Implementation Method 2

frequency-domain vibrational acceleration is obtained through FFT-analysis on time-domain vibrational acceleration

Methodology Applied

Scientific EffectFFT analysis:

Data Source

PatentUS9211624B2Vibration determination method and vibration determination device

Publication Date: 2015.12.15 OKUMA CORP

AI summary

Determination of chatter vibration is done for a plurality of peak values that appears when frequency-domain vibrational acceleration is obtained through fast Fourier analysis on time-domain vibrational acceleration. In machining at a low rotation speed and machining using a tool with small flute number in particular, a type of chatter vibration that has occurred can be accurately determined, and “natural type vibration” occurring due to friction between a tool and a workpiece and an impact force caused by machining can also be determined.