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Method Article

A Novel k-Nearest Neighbor Method with Distribution Discrepancy and Differential Feature Importance for Rolling Bearing Fault Diagnosis

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DOI:

10.3791/70568

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June 5th, 2026

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In This Article

Summary

This study proposes a k-nearest neighbor method that integrates distribution discrepancy and differential feature importance for accurate rolling bearing fault diagnosis.

Abstract

Rolling bearings are among the most vulnerable components in various types of rotary machinery, and accurate fault detection and localization are essential. When a rolling bearing fails, the signal is non-stationary, and the energy distribution of the vibration signal varies depending on the fault location. In traditional k-nearest neighbor (KNN) fault diagnosis algorithms, Euclidean distance is primarily used to measure the distance between sample points, which is not effective at capturing similarity across different spatial distributions. Moreover, these algorithms assume equal feature importance, which does not reflect the actual characteristics of fault vibration signals. This study proposes a KNN-based rolling bearing fault diagnosis method that incorporates distribution discrepancy and differential feature importance. First, vibration signals are decomposed using three-level wavelet packet decomposition, and the energy of each node at the third level is used as the fault feature. Then, the mean impact value (MIV) algorithm is used to determine the relative importance of each feature, and the Earth mover’s distance (EMD) is applied to measure differences between spatial distributions. By integrating Euclidean distance with MIV and EMD and applying the KNN majority voting rule, fault diagnosis is performed. The experimental results indicate that this method achieves a diagnostic accuracy of 99.43%, representing a 5.97% improvement compared to traditional KNN methods. The proposed method demonstrates accurate and effective fault diagnosis performance on the rolling bearing datasets used in this study.

Introduction

With the progress of technology, rotary machinery is increasingly developing toward integration, large-scale systems, high speed, and intelligent operation1. Among various types of rotary electrical machinery, rolling bearing components are the most vulnerable and commonly damaged parts. They offer advantages such as easy start-up, low friction, simple lubrication, and convenient replacement, and are widely used in precision instruments, aerospace, automobiles, machine tools, robots, and other fields. According to relevant statistical data on rotating machinery failures, abnormal vibration faults account for 70%, and 30% of these vibration faul....

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Protocol

This study did not involve human participants or animal subjects; therefore, ethical approval and informed consent were not required. The proposed method was implemented using MATLAB R2014b. The following toolboxes were used: Wavelet Toolbox for wavelet packet analysis (wpdec and wpcoef), Neural Network Toolbox for BP neural network implementation (feedforwardnet and train), Optimization Toolbox for solving the linear programming problem in EMD computation (linprog), and Statistics and Machine Learning Toolbox for KNN classification (fitcknn and predict). The EMD was implemented by solving the transportation problem using linear programming. All experiments were condu....

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Results

The experimental environment and platform are shown in Figure 2. From left to right, the platform consists of a fan-bearing assembly, an induction motor, and a drive unit. The central portion connects these components to a torque transducer/encoder via a coupling, and the rightmost section serves as the dynamometer. The control electronics are not depicted. EDM technology was used to simulate pitting faults on bearings, ranging from weak to severe conditions. Vibration data were collected us.......

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Discussion

The present study proposes a KNN-based fault diagnosis method for rolling bearings that integrates distribution differences through EMD and feature importance through MIV. Experimental results on a rolling bearing dataset containing four health states (normal, inner race fault, rolling element fault, and outer race fault) demonstrate the effectiveness of the proposed approach. The proposed KNN–MIV–EMD method achieves the highest classification accuracy of 99.43% at K = 3, outperforming traditional KN.......

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Disclosures

The authors declare no conflicts of interest.

Acknowledgements

This work was financially supported by the Key Scientific Research Projects of Colleges and Universities in Henan Province (25A580011) and the Scientific and Technological Research Project in Henan Province (262102210057).

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Materials

List of materials used in this article
NameCompanyCatalog NumberComments
Acquisition System
Data Recorder (16-channel)Anti-aliasing filter, 24-bit ADC; dynamic range >90 dB; Case Western Reserve University, Cleveland, OH, USA
Fault Type and Size (inch): All fault types
Load (HP): All
Sampling Frequency: 12 kHz or 48 kHz
Purpose in Study: High-quality data acquisition
File Naming Convention: N/A
Data Subset
Data Selection for This StudyDrive-end data, 12 kHz sampling, 4 load conditions; CWRU Bearing Data Center (https://engineering.case.edu/bearingdatacenter/download-data-file)
Fault Type and Size (inch): 7 conditions × 4 loads = 28 subsets
Load (HP): All
Sampling Frequency: 12 kHz
Purpose in Study: Model training and testing
File Naming Convention: Custom selection
Label Information
Fault Class LabelsOne-hot encoding format
Fault Type and Size (inch): [1,0,0,0,0,0,0] for Normal …
Load (HP): All
Sampling Frequency: N/A
Purpose in Study: Supervised learning labels
File Naming Convention: Label_vector.mat
Sensor
Accelerometer (Drive End)ICP accelerometer; position: 12 o’clock; sensitivity ~500 mV/g; Drive end bearing housing
Fault Type and Size (inch): All fault types
Load (HP): All
Sampling Frequency: 12 kHz or 48 kHz
Purpose in Study: Primary vibration signal acquisition
File Naming Convention: DE_time_series
Accelerometer (Fan End)ICP accelerometer; sensitivity ~500 mV/g; Fan end bearing housing
Fault Type and Size (inch): All fault types
Load (HP): All
Sampling Frequency: 12 kHz or 48 kHz
Purpose in Study: Auxiliary/comparison signal
File Naming Convention: FE_time_series
Test Bearing
Ball Bearing (Healthy)Deep groove ball bearing (6205 type); SKF (commonly used in CWRU setup)
Fault Type and Size (inch): Normal
Load (HP): 0, 1, 2, 3
Sampling Frequency: 12 kHz or 48 kHz
Purpose in Study: Baseline condition
File Naming Convention: Normal_0.mat
Ball Bearing (Inner Race Fault)Single-point fault via EDM
Fault Type and Size (inch): Inner Race (IR) @ 0.007", 0.014", 0.021", 0.028"
Load (HP): 0, 1, 2, 3
Sampling Frequency: 12 kHz or 48 kHz
Purpose in Study: Inner race fault validation
File Naming Convention: IR007_1.mat
Ball Bearing (Outer Race Fault)Single-point fault via EDM (6 o’clock position)
Fault Type and Size (inch): Outer Race (OR) @ 0.007", 0.014", 0.021", 0.028"
Load (HP): 0, 1, 2, 3
Sampling Frequency: 12 kHz or 48 kHz
Purpose in Study: Outer race fault validation
File Naming Convention: OR021_2.mat
Ball Bearing (Ball Fault)Single-point fault via EDM
Fault Type and Size (inch): Ball (B) @ 0.007", 0.014", 0.021", 0.028"
Load (HP): 0, 1, 2, 3
Sampling Frequency: 12 kHz or 48 kHz
Purpose in Study: Ball element fault validation
File Naming Convention: B014_3.mat
Test Rig
Machinery Fault SimulatorMotor-driven system with adjustable load; accelerometer mounted on bearing housing; Case Western Reserve University, Cleveland, OH, USA
Fault Type and Size (inch): N/A
Load (HP): 0, 1, 2, 3
Sampling Frequency: 12 kHz or 48 kHz
Purpose in Study: Source of fault dataset
File Naming Convention: N/A

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