Research On Acoustic Tracing And Positioning Technology Of Spherical Detector In Pipeline

The pipeline inner detector is one of the commonly used pipeline defect detection methods.The emerging spherical inner detector has a low risk of jamming,low production and operating costs,and convenient adjustment of the type of sensor mounted on the detector.It has begun to attract users’ attention and has broad application prospects.However,due to the special movement method of the spherical inner detector,it is difficult to realize real-time tracking using traditional internal detector tracking and positioning technology,which bring new risks in the detection process.This paper proposes an active acoustic positioning method based on the principle of ultrasonic guided waves in pipelines,and studies the acoustic tracking and positioning technology of the spherical inner detector.The main innovative work includes:Use the global matrix method to derive the pipeline dispersion equation and perform numerical calculations.Draw and compare the dispersion curves of the hollow pipeline and the liquid-filled pipeline.It is clear that the guided wave of the liquid-filled pipeline is affected by the coupling of the hollow pipeline and the liquid column in the pipeline,which changes between two forms with frequency.The time-domain simulation analysis of the propagation law of axisymmetric guided waves in the pipeline is carried out,and the simulation results are basically consistent with the dispersion curve.The ultrasonic guided wave tracing positioning method of the detector inside the spherical pipe is proposed,the positioning model is established and the influence of key parameters such as guided wave frequency,propagation time and propagation speed on the tracing positioning is clarified.An experimental device for guided wave positioning of water-filled pipes was built,and the key technical parameters of guided wave positioning under the excitation of non-axisymmetric sound sources were experimentally studied.The time-frequency analysis method is used to clarify the energy distribution characteristics of the guided wave signal,and a variety of signal time of arrival(TOA)methods are compared,and the positioning effect is fitted.It is clear that the dynamic threshold method is the best choice for obtaining TOA.The optimal excitation frequency is 45～65k Hz,and the propagation speed of the guided wave is about 1.5m/ ms.Design and realize the tracking and positioning system of the spherical inner detector,complete the software and hardware design of the ultrasonic guided wave transmitter and signal receiver,and the optimize the structure by simulation analysis to improve the transmission intensity.The internal detector tracing and positioning experiment test was carried out in the water-filled pipeline,which can realize real-time tracking and positioning.