Multi-frequency least squares demodulation method in electromagnetic rail inspection

As a result of the development of higher speed and heavier load of rail networks, rail defects have been more serious than ever before. This paper introduces the least squares method (LSM) to demodulate multi-frequency signals in electromagnetic rail inspection using eddy current detection. The demodulation speed of LSM is faster than other methods because it can estimate frequencies with one time matrix calculation. Furthermore, its calculation complexity is less than other demodulation methods like FFT and fast correlation. Consequently, this method can improve the demodulation speed without decrease the demodulation accuracy. And it will be used as ideal demodulation algorithm for online real time multi-frequency electromagnetic rail inspection.