Adaptive Filtering Method of MFL Signal on Rail Top Surface Defect Detection

Kailun Ji,Yunfei Ye,Ping Wang,Yinliang Jia,Shunyi Ding

doi:10.1109/access.2021.3065044

Abstract

Magnetic flux leakage (MFL) detection technology provides an effective method to conduct high-speed detection of the damage suffered by rail surface. With regard to high-speed detection, there is frequently a complex noise contained in the magnetic signal of railway leakage, which is similar to the amplitude of defect and the overlaps of frequency spectrum. In this paper, an improved adaptive filtering method is proposed to solve the problem caused by filtering the MFL signal on the rail top surface. Through the characteristics of distribution shown by defects on the top surface of the railway and those of the data collected by the rail top array sensor, this method is applied to construct a virtual channel containing almost only interference signals but no defects. Then, in combination with the adaptive filtering algorithm, the virtual channel signal is taken as the reference input of the adaptive canceller, each single channel MFL signal is taken as the original input of the adaptive canceller, and the filtered MFL signal is taken as the output. Then, the MFL signal of rail top is collected by the train at the speed of 30km / h on the manual calibration line. According to the experimental results, the noise intensity of MFL signal is reduced by up to 81.44%. In addition, the filtering method is adopted to process MFL signals with different directions and varying detection speed. As indicated by the results, the noise intensity of MFL signal is reduced by more than 74%.

Highlights

At present, the non-destructive testing technology of magnetic flux leakage (MFL) [1] has been widely applied to conduct non-destructive test on the surface cracks of such ferromagnetic parts as rails due to the simple structure of its sensor, the high sensitivity of detection and the capability of non-contact detection
EXPERIMENTS AND RESULTS At the speed of 30km/h, the Z-direction MFL signal of the measured rails with 8 pits is selected for signal processing
It can be known that the filtering method proposed in this paper shows a more significant advantage in processing high-speed MFL signals

Summary

INTRODUCTION

The non-destructive testing technology of magnetic flux leakage (MFL) [1] has been widely applied to conduct non-destructive test on the surface cracks of such ferromagnetic parts as rails due to the simple structure of its sensor, the high sensitivity of detection and the capability of non-contact detection. K. Ji et al.: Adaptive Filtering Method of MFL Signal on Rail Top Surface Defect Detection environmental conditions [6]. MFL signals contain complex noise under the condition of high-speed rails inspection These noises show large amplitudes, with the power spectra of these noise overlapping those of useful signals. In respect of signal processing, it is inevitable for these requirements to result in the circumstance where high-intensity and nonstationary random noise is made and the power spectrum of the noise overlaps with useful signals The noise of these types can cause serious interference with signal analysis and defect reconstruction. They play a major role in hindering the application of MFL detection technology in the field of rail inspection.

THEORETICAL ANALYSIS OF MFL DETECTION

IMPROVED ADAPTIVE FILTERING METHOD

THE INDICATOR OF FILTER EFFECT EVALUATION

RESULTS AND DISCUSSIONS

CONCLUSION AND FUTURE WORK