Fig 1.
Flowchart of the FPA algorithm.
Fig 2.
Flowchart of the IFPA algorithm.
Table 1.
Parameters of the test function.
Table 2.
Performance comparison of four optimization algorithms of reference function f1–f6.
Table 3.
Performance comparison of four optimization algorithms of reference functionf7 -f10.
Fig 3.
Algorithm convergence curve.
Fig 4.
Structure diagram of ELM network.
Fig 5.
Flowchart of the IFPA-ELM model.
Fig 6.
Flowchart of feature extraction of pipeline defect signal.
Table 4.
Peak-to-valley curve data of a single-peak–double-valley flux leakage signal.
Table 5.
Six features of pipeline defect signal.
Fig 7.
EMD diagram of a normal pipeline signal S1.
Fig 8.
EMD diagram of a pipeline pit defect signal S2.
Fig 9.
EMD diagram of a pipeline crack defect signal S3.
Fig 10.
Correlation coefficient plot of each IMF component and the original signal.
Table 6.
Table of IMF components in relation to raw data.
Table 7.
Sample entropy of each IMF.
Table 8.
Main parameter settings of the optimisation algorithm.
Table 9.
Output results based on three algorithms.
Table 10.
Comparison of the identification rates of defective samples.