Bearing Abnormality Diagnosis via Servo Frequency Analysis
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Solution Overview
Problem
In machine tools with a feed axis using a ball screw, diagnosing bearing abnormalities is challenging due to overlapping vibration frequencies with the ball screw, leading to potential misdiagnosis and increased failure risk without additional sensors.
Innovation Solution
A method and device that perform frequency analysis on servo information from a servomotor to determine damage frequencies, comparing them to thresholds, while accounting for interference between bearing and ball screw vibration frequencies, using different thresholds for interference and non-interference scenarios to accurately diagnose bearing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequency analysis is performed on servo information to diagnose bearing abnormalities, then diagnostic capability is improved, but misdiagnosis occurs when bearing vibration frequency overlaps with ball screw vibration frequency
Solution Approach 1:
The patent segments the vibration frequency spectrum into distinct analysis bands. By dividing the frequency range and analyzing specific frequency components separately, the system can distinguish between bearing vibrations and ball screw vibrations even when their frequencies are close, preventing misdiagnosis while maintaining diagnostic accuracy.
Solution Approach 2:
The patent changes the analysis parameters by using different thresholds for threshold comparison based on the specific frequency characteristics being analyzed. By adjusting diagnostic parameters dynamically according to the operating conditions and frequency overlap scenarios, the system achieves reliable diagnosis without misidentifying normal ball screw vibrations as bearing abnormalities.
2Measurement precision
If additional sensors are added to diagnose ball screw and bearing vibrations separately, then diagnostic precision is improved, but system cost and complexity increase
Solution Approach 1:
The patent makes the existing vibration sensor serve multiple diagnostic functions. By developing advanced signal processing algorithms that can extract information about both ball screw and bearing conditions from a single vibration signal, the system achieves comprehensive diagnostics without adding additional sensors, thereby reducing system complexity and cost.
Solution Approach 2:
The patent replaces the need for multiple physical sensors with sophisticated signal processing and analysis methods. By using computational techniques to separate and identify different vibration sources within the single sensor signal, the system achieves precise diagnostics without the mechanical complexity of multiple sensors.
3Measurement precision
If vibration frequencies of bearing and ball screw are close, then normal ball screw vibrations may be misdiagnosed as bearing vibrations, but using different thresholds for interference and non-interference cases resolves this issue
Solution Approach 1:
The patent implements dynamic threshold adjustment based on the detected frequency overlap conditions. When frequency interference is detected between ball screw and bearing vibrations, the system automatically switches to different analysis thresholds and methods appropriate for interference conditions, thereby eliminating misdiagnosis while maintaining high detection precision.
Solution Approach 2:
The patent changes diagnostic parameters dynamically based on the operating mode and frequency characteristics. By adjusting analysis thresholds and parameters according to whether frequency interference is present, the system accurately distinguishes between normal ball screw vibrations and actual bearing abnormalities, preventing misdiagnosis while maintaining high detection accuracy.
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 reduces the risk of misdiagnosing normal ball screw vibrations as bearing vibrations, enabling accurate detection of bearing damage even when their frequencies are close, thus preventing unnecessary component replacement and failure.
Implementation Method 1
a frequency analysis unit that performs a frequency analysis on the servo information
Data Source
AI summary
An abnormality diagnostic method executes causing the feed axis to perform an axis operation in a predetermined diagnosis condition to obtain servo information according to a control of the servomotor, performing a frequency analysis on the obtained servo information, obtaining a damage frequency generated while the feed axis whose bearing is damaged performs the axis operation, from a result of the frequency analysis, and comparing the obtained damage frequency with a predetermined threshold to determine a presence/absence of an abnormality. In the determining, before the damage frequency is compared with the threshold, a determination whether a vibration frequency of the bearing interferes with a vibration frequency generated while a rolling element passes through a nut of the ball screw or not is performed, and the comparison is performed by setting the respective thresholds that are different in a case of the interference and a case of no interference.