Abstract
During the non-contact geomagnetic detection of pipeline defects, measured signals generally contain noise, which reduces detection efficiency. Complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) has recently emerged as a signal filtering method, but its filtering performance is influenced by two parameters: the amplitude of added noise and the number of ensemble trials. To solve this issue and improve detection accuracy and distinguishability, a detection method based on improved CEEMDAN (ICEEDMAN) and the Teager energy operator (TEO) is proposed. The magnetic detection signal was first decomposed into a series of intrinsic mode functions (IMFs) by CEEMDAN with initial parameters. Signal IMFs were then distinguished using the Hurst exponent to reconstruct the preliminary filtered signal, and its maximum value (except the zero point) of the normalized autocorrelation function was defined as salp swarm algorithm (SSA) fitness. The optimal parameters that maximize fitness were found by SSA iterations, and their corresponding filtered signal was obtained. Finally, the gradient calculation and TEO were carried out to complete non-contact geomagnetic detection. The results of the simulated signal based on magnetic dipole under a noisy environment and field testing prove that ICEEMDAN denoising has better filtering performance than conventional CEEMDAN denoising methods, and ICEEMDAN-TEO has obvious advantages compared to other detection methods in the aspects of location error, peak side-lobe ratio, and integrated side-lobe ratio.
Highlights
Buried steel pipelines are used for oil and gas transportation across the world and directly influence national economies and public security
External inspection techniques represented by the transient electromagnetic method (TEM) [10] and Nopig [11] can be applied for the inspection of buried steel pipelines where the use of in-line inspection (ILI) is challenging
The results prove that ICEEMDAN denoising can adaptively select parameters to achieve the most effective filtering for the noisy magnetic detection signal
Summary
Buried steel pipelines are used for oil and gas transportation across the world and directly influence national economies and public security. External inspection techniques represented by the transient electromagnetic method (TEM) [10] and Nopig [11] can be applied for the inspection of buried steel pipelines where the use of ILI is challenging These techniques have low detection efficiencies and are influenced by the excitation source. TEO estimates the total energy required for the source to produce a dynamic signal which can calculate instantaneous amplitude and instantaneous frequency and extract instantaneous energy This method has been successfully applied in speech recognition [38], bearing fault detection [39], and power system oscillation diagnosis [40]. The magnetic detection signal was decomposed into a series of IMFs via CEEMDAN with an initial amplitude of added noise and a number of ensemble trials. The gradient calculation and TEO were used to identify the locations of pipeline defects
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