Active compensation method for restraining high-speed MFL signals distortion based on atypical synthesized magnetic field

Abstract

Magnetic flux leakage (MFL) detection is attaching importance in pipeline non-destructive detection. However, the MFL signals will be distorted due to the speed effect, resulting in a low detection accuracy. Reducing the detection speed and algorithmic compensation for the offline data are the two main current methods, but these methods reduce the detection efficiency and require a large amount of training data. In this article, an active compensation method for restraining high-speed MFL signals distortion based on atypical synthesized magnetic field (ASMF) is proposed to solve above problems. ASMF is a magnetic field with the asymmetric double peaks, whose shape and intensity can be complementary to the distorted MFL signals. First, the dynamic circuit theory is introduced to elaborate the speed effect mechanism. Second, the ASMF method is proposed to compensate the distorted MFL signals according to the speed. Furthermore, the target and non-target magnetic fields are corrected to satisfy the MFL detection under different lift-off. The relative optimum position between the main peak and side peak is studied to further reduce the MFL signals distortion. Third, the active compensation circuit system is developed, which can measure the speed and lift-off in real time to adjust ASMF and compensate the distorted MFL signals. Finally, the MFL detection experiments under different speed, lift-off, and defect are performed to verify the effectiveness of the proposed method. Results show that the minimum relative error of the defect depth detection using the compensated MFL signals can reach -2.33%, and Type A uncertainty $U_{Am}$ can be kept within 0.0346 mm.