An improved matching pursuit method for overlapping echo separation in ultrasonic thickness measurement

Abstract

Overlapping of reflected ultrasonic echoes is a universal physical phenomenon, when the measured thickness is less than a limit threshold (e.g. 1mm for metallic materials using conventional processing methods). Generally, two typical signal states may be generated in this situation: highly overlapping and distorted overlapping. If the overlapping echoes cannot not be separated precisely, significant measurement errors will inevitably occur. In this research, an improved matching pursuit method for overlapping echo separation has been developed. To approximate the overlapping echoes, a dictionary composed of atoms with truncated Nakagami functions is constructed to replace the commonly used model, which considers scattering conditions. Furthermore, an atomic selection principle combining preselection of the remainder L2 norm and minimum L1 norm of the residual signal is presented. To reduce the correlation of the residual error in iterations and ensure the correct separation of echoes in order, the ultrasonic signal is truncated for matching based on short-time Fourier transform (STFT) analysis. Compared with some competing methods, the proposed method shows superiority in handling highly overlapping echoes and distorted echoes in both simulation and experiments of ultrasonic thickness measurement.

Scanning control based on real-time contact force feedback for ultrasonic thickness measurement

“…To realize the ultrasonic thickness scanning process, a multi-functional and highly integrated ultrasonic on-machine thickness measuring device is designed and the scanning process of the thickness is proceeded on the CNC equipment (Lian et al, 2019a; Lian et al, 2019b), as shown in Figure 1. It is composed of a programmable multi-axis controller, eight servo drivers, eight servo motors, a force sensor, an ultrasonic probe, a data acquisition card, and an industrial computer.…”

Continuous Artery Monitoring Based on Decomposition of Ultrasound Radiofrequency Signals

“…Matching pursuit (MP) [73], [82], [94] methods of signal decomposition, on the other hand, offer a flexible approach for representing signals in terms of localized structures using a selected basis. MP does not suffer from inherent resolution limitations and does not assume a static echo shape along the depth of the signal.…”

“…Separation of overlapping echoes is a problem that is studied in ultrasound nondestructive evaluation and biomedical applications. MP methods of decomposition have received attention in ultrasound nondestructive evaluation [82], [102], [103], and demonstrated success despite drawbacks in the MP algorithm such as the greedy selection resulting in suboptimal echo estimates and the tendency to converge to global signal structures. IMT estimation requires the depth location of the echoes from the lumen-intima and media-adventitia boundaries of the artery wall.…”

“…Other echo models exist that incorporate additional parameters to characterize frequencyChapter 4. Methods of Ultrasound RF Signal Decomposition and Artery Monitoring 41dispersion and diffuse scattering[82]. Dispersion can cause a frequency downshift of the ultrasound wave within the received echo (chirping).…”

“…Additionally, statistics of the ultrasound RF signal envelope change depending on the scattering density and structure, and can be characterized using a model known as the Nakagami distribution[83]. The authors in[82] used a Nakagami envelope shape for the ultrasound RF echo model, and demonstrated lower residual error compared to the GMS model when fit to an acquired echo.…”