CN111060600A

CN111060600A - Sound beam focusing time delay control method for ultrasonic phased array imaging in pipeline

Info

Publication number: CN111060600A
Application number: CN201911244567.2A
Authority: CN
Inventors: 谭超; 李占鹏; 刘皓; 董峰
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2019-12-06
Filing date: 2019-12-06
Publication date: 2020-04-24
Anticipated expiration: 2039-12-06
Also published as: CN111060600B

Abstract

The invention relates to an acoustic beam focusing time delay control method for ultrasonic phased array imaging in a pipeline, which comprises the following steps: the method comprises the following steps: an ultrasonic phased array sensor arrangement. Step two: and (4) exciting and receiving the ultrasonic phased array sensor. Step three: considering any angle deflection in the field with the circular pipeline as the boundary, the time delay according to each channel is calculated. Step four: and distributing the time delay obtained by the calculation in the third step to each array element excitation channel of the ultrasonic phased array probe, delaying the same excitation electric signal for different time to generate excitation electric signals with equal amplitude and different phases, applying the excitation electric signals to each array element of the phased array probe to generate ultrasonic excitation with equal amplitude and different phases, and generating ultrasonic focusing waves with different focusing distances through superposition, cancellation and interference effects of the ultrasonic excitation electric signals to achieve effective control of focusing of any point sound beam in the pipeline.

Description

Sound beam focusing time delay control method for ultrasonic phased array imaging in pipeline

Technical Field

The invention belongs to the technical field of ultrasonic tomography, and relates to a time delay control method for sound beam focusing, which is used for solving the problems of errors and control failure caused by curved-surface pipe wall refraction in the ultrasonic phased array sound beam focusing process and realizing the visual test of high-precision sound field configuration and multi-phase medium distribution in a closed pipeline in the industrial process.

Background

Ultrasonic Tomography (UT) is a structural imaging technique that reconstructs refractive index, attenuation coefficient, or acoustic impedance distribution inside a field to be measured by arranging an array of Ultrasonic sensors outside the field to be measured and applying certain excitation to obtain boundary voltage measurement data. Compared with other soft field imaging technologies such as Electrical Impedance Tomography (EIT) and electromagnetic Tomography (MIT), UT has the advantages of non-invasion and high resolution, and compared with a hard field imaging technology with higher precision such as X-ray Computed Tomography (X-CT) and an optical Tomography (OCT), UT is safe to use, has a simple structure and can realize real-time imaging. In addition, the UT also has the advantages of non-contact, good directivity, low cost and the like, and is an ideal process visual detection monitoring means. The UT is used as a chromatographic imaging technical means and has wide application in multiphase flow visualization detection, chemical petroleum transportation, aircraft engine exploration and biomedical diagnosis.

The complete ultrasound tomography technique consists of three parts: designing, manufacturing and installing an ultrasonic transducer array; a signal excitation and acquisition system; and (3) an ultrasonic imaging image reconstruction algorithm. The ultrasonic transducer array consists of a plurality of single-wafer probes, the exciting probe converts a voltage signal into an acoustic signal through an inverse piezoelectric effect to form an exciting acoustic wave, and the receiving probe converts the sensed acoustic signal into an electric signal through the piezoelectric effect to send the electric signal to the detection system; the signal excitation and acquisition system sends a voltage excitation signal to the ultrasonic transducer, records, converts and demodulates a voltage detection signal generated by the ultrasonic transducer, and circularly excites the ultrasonic transducer at different positions through time sequence control; and the image reconstruction algorithm obtains effective measurement data of all the transducers under certain excitation by using the extracted measurement amplitude or the transit time obtained by demodulation, and obtains reasonable estimation of the distribution of the content medium in the field by using an image reconstruction method.

The traditional ultrasound tomography technology based on the single wafer probe has certain limitations: the single crystal probe emits sound waves in a fan shape (cone shape), the scanning range is narrow, side lobe attenuation is large under the condition of a wide emission angle, the installation position and the direction of the single crystal probe are fixed, and dynamic configuration and direction-variable scanning of an excitation sound field cannot be realized. In addition: the ultrasonic tomography depends heavily on the number of field boundary transducers, and the image reconstruction process has serious ill-conditioned (small perturbation on the measured value can cause large-amplitude change of the reconstruction result) and under-qualitative (the number of the equation to be solved is far less than the unknown quantity) under the condition of low transducer number. The development of ultrasound tomography is severely limited by the fixed excitation acoustic field format and the limited number of transducers. In order to realize high-precision and non-disturbance ultrasonic tomography visual test, Tan super et al at Tianjin university propose a scanning tomography method based on ultrasonic plane waves in the patent ultrasonic plane wave scanning multiphase flow visual measurement device, sound beam control is carried out by controlling time delay of each array element in an ultrasonic phased array probe, a sound field is flexibly configured in an area which can not be detected by a traditional single-wafer probe, the quantity of projection data is greatly improved under the condition of not increasing an ultrasonic transducer, and image reconstruction quality is improved.

In the ultrasonic phased array acoustic beam focusing control algorithm, each array element is generally equivalent to a point sound source, time delay is added to an excitation signal of each channel to generate phase difference, and an excitation acoustic wave array surface of each array element is configured through the Huygens theorem to form a focusing acoustic beam with a variable aperture. The method is widely applied to the research of medical ultrasonic phased array imaging and industrial material nondestructive testing. However, in the industrial process, the ultrasonic tomography generally faces a closed test field with a definite physical boundary (such as a pipe, a container, etc.), and the acoustic characteristics of media on both sides of the boundary are different, so that a stronger acoustic impedance difference often exists. The sound wave is transmitted from the probe array element to the field region and needs to pass through the physical boundary and generate nonlinear effects such as amplitude attenuation, direction change and the like, so that the control effect of sound beam focusing time delay generates larger error and the control is invalid. Aiming at the common physical boundary of a circular pipeline in the industrial process, an acoustic beam focusing time delay control method aiming at the curved surface configuration is urgently needed, so that the dynamic focusing of the acoustic beam can be realized in circular pipelines with different materials, thicknesses and diameters, and the aim of dynamically configuring and exciting a sound field at high precision is fulfilled.

Disclosure of Invention

The invention aims to provide an ultrasonic phased array acoustic beam focusing time delay control method based on travel time equality, aiming at the problem that the control of acoustic beam focusing time delay is invalid due to the fact that the control of the acoustic beam focusing time delay is large in error caused by a curved surface physical boundary represented by a circular pipeline. In circular pipelines with different materials, thicknesses and diameters, dynamic focusing of sound beams is realized, and the purpose of dynamically configuring and exciting a sound field with high precision is achieved.

1. An acoustic beam focusing time delay control method for ultrasonic phased array imaging in a pipeline comprises the following steps:

the method comprises the following steps: ultrasonic phased array sensor arrangement: the ultrasonic phased array probe comprises an ultrasonic sensor array formed by a plurality of ultrasonic phased array probes, each ultrasonic phased array probe is a linear array formed by a fixed number of array elements, each array element has the same performance parameters and can be independently excited or received, all the ultrasonic phased array probes are arranged at equal intervals along the anticlockwise direction, the ultrasonic phased array probes are embedded and installed on the outer wall of a pipeline, the surfaces of the ultrasonic phased array probes are all parallel to the tangential direction of the outer wall of the pipeline, and the ultrasonic phased array probes are coupled with the outer wall of the pipeline by a coupling agent.

Step two: and (4) exciting and receiving the ultrasonic phased array sensor. And sequentially selecting the ultrasonic phased array probes for excitation according to a cyclic excitation scheme. And performing time delay control on the M array element channels of the excitation phased array probe to enable the acoustic beam to be focused at any distance in the field. Meanwhile, all array elements of other phased array probes receive ultrasonic signals transmitted in the pipeline and analyze and process the signals; and calculating a projection path based on the geometric position and the sound field configuration form, and recording and storing time-varying waveform data of the corresponding path.

Step three: considering axial arbitrariness within a field bounded by circular pipesFocusing distance, selecting the number of array elements of the ultrasonic phased array probe as M, the pitch of the array elements as s, and the thickness of the pipeline, namely the distance between the phased array probe and the tangent line of the physical boundary of the field to be measured as DT₀The axial focusing distance of the sound beam to be controlled is DF, the inner diameter of the pipeline is R, the sound velocity of the pipeline is c₁The sound velocity of the background medium in the field to be measured is c₂Calculating the transit time Deltat of the ith array element_{i_focus}Expressed as follows:

calculating the time delay t of each array element according to the time delay of each channel_{di_focus}Expressed as follows:

t_{di_focus}＝max(Δt_{i_focus})-Δt_{i_focus}

step four: and distributing the time delay obtained by the calculation in the third step to each array element excitation channel of the ultrasonic phased array probe, delaying the same excitation electric signal for different time to generate excitation electric signals with equal amplitude and different phases, applying the excitation electric signals to each array element of the phased array probe to generate ultrasonic excitation with equal amplitude and different phases, and generating ultrasonic focusing waves with different focusing distances through superposition, cancellation and interference effects of the ultrasonic excitation electric signals to achieve effective control of focusing of any point sound beam in the pipeline.

The invention provides an ultrasonic phased array sound beam focusing time delay control method based on travel time equality, aiming at the problem that sound beam focusing time delay control is invalid due to the fact that a curved surface physical boundary represented by a circular pipeline generates a large error. By using the method, the dynamic focusing of the sound beam can be realized in circular pipelines with different materials, thicknesses and diameters, the excitation sound field is configured dynamically and precisely, and the solving precision and the image resolution of the reconstruction result are obviously improved on the basis of meeting the real-time requirement of the industrial flow process.

Drawings

FIG. 1 is a schematic diagram of a basic test scheme and sensor arrangement for ultrasonic phased array tomography;

FIG. 2 is a schematic diagram of the ultrasonic phased array probe acoustic beam focusing control method in the presence of a circular pipe according to the present invention;

FIG. 3 is a graph comparing the focusing effect of sound beams using the method of the present invention and the general control method for different inner diameters of pipes;

Detailed Description

The invention discloses an acoustic beam focusing time delay control method for ultrasonic phased array imaging in a pipeline, which comprises the following steps:

the method comprises the following steps: an ultrasonic phased array sensor arrangement. The ultrasonic sensor array is formed by a plurality of ultrasonic phased array probes, each ultrasonic phased array probe is a linear array formed by a fixed number of array elements, each array element has the same performance parameter and can be independently excited or received, all the sensors are arranged at equal intervals along the anticlockwise direction, the sensors are embedded and installed on the outer wall of the pipeline, the surfaces of the sensors are all parallel to the tangential direction of the outer wall of the pipeline, and the sensors are coupled with the outer wall of the pipeline by a coupling agent.

Step three: considering the axial random distance focusing in the field area with the circular pipeline as the boundary, the array element number of the ultrasonic phased array probe is selected to be M, the array element pitch is selected to be s, and the distance between the thickness of the pipeline (the distance between the phased array probe and the physical boundary tangent line of the measured field area) is selected to be DT₀The axial focusing distance of the sound beam to be controlled (focusing distance in the pipeline) is DF, the inner diameter of the pipeline is R, and the sound velocity of the pipeline is c₁Background medium sound velocity in the field to be measuredIs c₂. Calculating the transition time delta t of the ith array element_{i_focus}Expressed as follows:

t_{di_focus}＝max(Δt_{i_focus})-Δt_{i_focus}

In the embodiment of the acoustic beam focusing time delay control method for ultrasonic phased array imaging in the circular pipeline, the method provided by the invention is used for controlling the acoustic beam focusing time delay of the ultrasonic phased array probe in a common application form of an ultrasonic tomography technology of oil-gas-water three-phase flow imaging in an industrial pipeline. The basic principle of ultrasonic phased array tomography and the operation steps and the improvement effect of the method provided by the invention are described in detail below by taking an ultrasonic phased array transducer array consisting of 8 16-array-element phased arrays as an example. The following examples are intended to be illustrative of embodiments of the invention and are not intended to be the only forms in which the present invention may be made or utilized, and other embodiments that perform the same function are also within the scope of the present invention.

FIG. 1 depicts the basic principle of ultrasonic phased array tomography using the method of the present invention, and depicts the mechanism of ultrasonic plane wave testing with water as the continuous phase and gas bubbles and oil bubbles as the discrete phases. When ultrasonic plane waves are formed between the excitation phased array probe and the receiving phased array probe, a test passage is formed between corresponding array elements of the transmission phased array probe and the receiving phased array probe, and oil-gas-water three-phase media in the test passage can generate different ultrasonic propagation modulation effects due to different densities. Due to the strong reflection effect of the bubbles on the ultrasound, incident waves are basically and completely reflected, and the size change of the bubbles can directly influence the ultrasound intensity reaching array elements at different positions of the receiving probe, so that the receiving amplitude of each array element is different, and accordingly, attenuation information corresponding to gas-liquid distribution in the ultrasound passage is obtained. In addition, because the propagation speeds of the ultrasonic waves in the oil phase medium and the water phase medium are different, the oil-water ratio between the corresponding array elements during the process that the ultrasonic plane waves emitted from the excitation phased array probe reach the receiving end does not directly influence the propagation time of the ultrasonic waves in the passage. Attenuation information and time delay information in the ultrasonic path are comprehensively utilized, and phase distribution reconstruction of a three-phase medium can be realized.

Fig. 2 is a schematic diagram illustrating a sound beam focusing control method when the ultrasonic phased array probe is embedded in a pipeline. By controlling the emission delay time tau of each array element of the phased array probe, ultrasonic plane waves with variable directions can be formed in a measured field domain, and after the delay of the array elements is accurately calculated, an ultrasonic focused wave measuring space can be formed between the excitation ultrasonic phased array probe and other phased array probes. The number of array elements of the ultrasonic phased array probe is selected to be M equal to 16, the pitch of the array elements is s equal to 1.2mm, and the distance between the thickness of a pipeline (the distance between the phased array probe and a physical boundary tangent line of a field to be measured) is DT₀The axial focusing distance of the sound beam (focusing distance in the pipeline) to be controlled is DF 20 mm. The inner diameters of the pipelines are respectively 200mm and 100mm, and the sound velocity of the pipeline is c₁2730m/s, the sound velocity of the background medium in the field area to be measured is c₂＝1480m/s。

Fig. 3 shows the difference of the sound beam focusing delay control effect by using the method of the present invention and the conventional method under different inner diameters of the pipes. The traditional time delay control method has the defects that the area of a focusing area is large, the error between the distance of the focusing area and the set axial focusing distance is large, and the control is invalid. The method can effectively focus at any axial distance of the probe in the field in the presence of pipelines with different pipe diameters, and has small area of a focusing area and small distance error; the acoustic beam grating lobes are effectively suppressed under the pipelines with different inner diameters.

The embodiments described above are some exemplary models of the present invention, and the present invention is not limited to the disclosure of the embodiments and the drawings. It is intended that all equivalents and modifications which come within the spirit of the disclosure be protected by the present invention.

Claims

Step two: excitation and reception of the ultrasonic phased array sensor: and sequentially selecting the ultrasonic phased array probes for excitation according to a cyclic excitation scheme. And performing time delay control on the M array element channels of the excitation phased array probe to enable the acoustic beam to be focused at any distance in the field. Meanwhile, all array elements of other phased array probes receive ultrasonic signals transmitted in the pipeline and analyze and process the signals; and calculating a projection path based on the geometric position and the sound field configuration form, and recording and storing time-varying waveform data of the corresponding path.

Step three: considering the axial random distance focusing in the field area with the circular pipeline as the boundary, the array element number of the ultrasonic phased array probe is selected as M, the array element pitch is s, the thickness of the pipeline, namely the distance between the phased array probe and the physical boundary tangent line of the measured field area is DT₀The axial focusing distance of the sound beam to be controlled is DF, the inner diameter of the pipeline is R, the sound velocity of the pipeline is c₁The sound velocity of the background medium in the field to be measured is c₂Calculating the transit time Deltat of the ith array element_{i_focus}Expressed as follows:

t_{di_focus}＝max(Δt_{i_focus})-Δt_{i_focus}