Cyclic Machine Condition Monitoring for Variable-Speed Fault Detection

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Solution Overview

Problem

Existing condition monitoring methods for cyclically moving machine components, such as bearings and motors, lack accuracy and are complex due to assumptions like constant rotation speed and localized damage, which can lead to missed or premature predictions of impending breakdowns.

Innovation Solution

A method involving the registration of movement characteristics, generation of frequency distributions, segmentation into defined indexes, and comparison of reference term frequencies to accurately classify the machine component status, allowing for timely detection of deviant behavior and impending breakdowns without relying on complex assumptions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional vibration analysis methods are used with assumptions of constant rotation speed and localized damage, then the analysis process becomes simpler, but the measurement precision and reliability of breakdown prediction deteriorate

Engineering Contradiction:
Improvebreakdown prediction accuracyVSAvoidanalysis method complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The vibration signal analysis is segmented into discrete cycles of the machine component. Each cycle is divided into angular segments corresponding to specific positions of the component (e.g., bearing races). This segmentation allows for position-resolved vibration analysis without requiring constant rotation speed assumptions, as each angular position is analyzed independently within its cycle context.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The method transitions from static frequency domain analysis (FFT) to dynamic time-domain analysis where vibration signals are evaluated in the context of actual component motion cycles. The analysis adapts to variable speeds by synchronizing measurements with component position rather than time, allowing accurate breakdown detection even when rotation speed varies during operation.

Inventive Principle:
Principle #15Dynamics

2Reliability

If empirical evaluation of motion characteristics is used, then the implementation becomes simpler, but the reliability of remaining lifetime estimation deteriorates due to error-prone manual assessment

Engineering Contradiction:
Improveremaining lifetime estimation reliabilityVSAvoidautomated analysis system complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The system performs automated self-diagnosis by processing its own vibration measurement data through cycle-resolved analysis algorithms. The method automatically identifies characteristic vibration patterns associated with different fault types (inner race, outer race, ball defects) and estimates remaining lifetime without requiring external expert intervention, thereby improving reliability while maintaining manageable complexity through algorithmic automation.

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The system continuously monitors vibration signals and provides feedback on component health status. By comparing measured vibration characteristics against known fault signatures and tracking changes over multiple cycles, the system dynamically adjusts its assessment of component condition and remaining lifetime, improving reliability through continuous self-evaluation rather than static empirical methods.

Inventive Principle:
Principle #23Feedback

3Adaptability or versatility

If constant rotation speed assumption is made for servomotors, then the calculation model becomes simpler, but the adaptability to actual variable speed operation in automatic machines deteriorates

Engineering Contradiction:
Improvevariable speed profile compatibilityVSAvoidspeed adaptation mechanism complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The analysis method is fundamentally dynamic, synchronizing vibration signal acquisition and analysis with the actual motion cycles of the machine component rather than assuming constant speed. By using cycle-resolved analysis where each vibration cycle is evaluated in the context of the component's actual position and motion state, the system naturally adapts to variable speed profiles without requiring separate speed compensation mechanisms.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The method transitions from time-domain analysis (which requires constant speed assumptions) to angular-domain or cycle-domain analysis. By evaluating vibrations as a function of component angular position rather than time, the system adds a spatial dimension to the analysis that is independent of speed variations, allowing accurate fault detection whether the component rotates at constant or variable speed.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

4Measurement precision

If traditional frequency spectrum analysis is used, then the detection method becomes simpler, but the measurement precision deteriorates when signal-to-noise ratio is low or damage causes are smeared

Engineering Contradiction:
Improvefault detection precisionVSAvoidsignal processing complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The vibration signal is segmented into discrete cycles and further divided into angular segments corresponding to specific positions of the machine component. This segmentation concentrates fault-related vibrations at their characteristic angular positions rather than spreading them across the entire frequency spectrum, improving detectability even when overall signal-to-noise ratio is low. The segmented approach allows identification of localized defects that would be smeared in traditional FFT analysis.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system performs preliminary signal conditioning and cycle-synchronization before fault detection analysis. By pre-processing the vibration signals to align with component cycles and filter out unrelated vibrations, the method enhances the signal-to-noise ratio for fault-related frequencies before the actual detection step, improving precision without requiring excessively complex post-processing.

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP3660613B1A method for condition monitoring of a cyclically moving machine component
Publication Date: 2021.07.21 TETRA LAVAL HOLDINGS & FINANCE SA
  • EP3660613B1 patent drawingFigure 1~2
  • EP3660613B1 patent drawingFigure 3a~3b
  • EP3660613B1 patent drawingFigure 4~5

AI summary

A method (1000) for condition monitoring is disclosed, comprising registering (1010) values (vi) of movement characteristics measured for cycles of motion of a cyclically moving machine, associating (1050) the occurrence of values in a frequency distribution (Fv1) of the values with respective defined indexes (a, b, c, ...) based on intervals, generating (1060) a word string (S) of the defined indexes corresponding to the occurrence of the values, segmenting (1070) said word string (S) into a sub-set of words (si, s2, ..., si), determining (1080) a frequency of the occurrence of the segmented words in said word string as a first reference term frequency (TF1), associated with a first machine status (M1), for subsequently registered set of values of movement characteristics, determining (1100) a subsequent term frequency (TFn), comparing (1110) the subsequent term frequency (TFn) with the first reference term frequency to determine a correlation with the first machine status.