CN110554049B - Composite insulator defect detection device and method based on terahertz wave, and medium - Google Patents
Composite insulator defect detection device and method based on terahertz wave, and medium Download PDFInfo
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- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
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- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
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Abstract
A composite insulator defect detection method, a composite insulator defect detection device and a computer readable storage medium based on terahertz waves are provided, wherein the method comprises the following steps: collecting terahertz time-domain incident waves incident to the composite insulator and terahertz time-domain reflected waves reflected back through the composite insulator; converting a terahertz time-domain incident wave into a terahertz frequency-domain incident wave and converting a terahertz time-domain reflected wave into a terahertz frequency-domain reflected wave; constructing a frequency domain expression of the terahertz frequency domain reflected wave based on the terahertz frequency domain incident wave, the transfer function of the composite insulator and a preset correction term; solving the frequency domain expression to obtain a frequency domain optimal solution of the transfer function; converting the frequency domain optimal solution of the transfer function into a time domain waveform; and analyzing the time domain waveform based on the transfer function to obtain the defect detection result of the composite insulator. According to the invention, the waveform is analyzed by using a convolution removing algorithm, the possibility of overlapping terahertz pulses is reduced, and the defect detection precision of the composite insulator is improved.
Description
Technical Field
The invention relates to the technical field of product detection, in particular to a terahertz wave-based composite insulator defect detection device and method and a computer-readable storage medium.
Background
Compared with the traditional insulator, the composite insulator has the advantages of light weight, simple production process, lower maintenance cost, strong hydrophobicity and hydrophobic migration performance and the like, and the use amount of the composite insulator is continuously increased since the composite insulator is put into commercial operation. The composite insulator plays a significant role in the electric power system in China, and the working state of the composite insulator influences the safe and stable operation of a power grid. The composite insulator has complex structure and shape, severe working environment and higher requirements on nondestructive testing technology, and the existing nondestructive testing method has limitations in being applied to the detection of the internal defects of the composite insulating material, for example, the traditional ultrasonic testing method has more complicated operation and is not suitable for the detection of the composite insulator with complex structure; the traditional infrared detection method is only suitable for live detection and cannot be used for detection before the composite insulator is networked; x-ray detection is expensive in equipment and harmful to humans. And the internal defects formed in the composite insulator at an early stage are difficult to identify by the conventional detection method because the composite insulator is hidden, has small size and can appear at a deeper position.
The terahertz detection wave method can simultaneously guarantee a plurality of requirements on convenient and safe operation, detection of defects with small size and the like. The existing terahertz wave detection method mainly utilizes the number of pulses to judge the condition of an internal interface of the composite insulator, so that whether defects exist or not is identified. But since the terahertz pulse is generally a bipolar pulse and has a certain width, about 20 ps. When the defect size of the composite insulator is small and the number of interfaces is large, partial/complete pulse overlapping may occur, and the defect detection accuracy is further affected.
Disclosure of Invention
In view of the above, there is a need to provide a composite insulator defect detection apparatus and method based on terahertz waves, and a computer readable storage medium, which perform deconvolution processing on terahertz reflected waves reflected by a composite insulator interface, so as to reduce the possibility of overlapping terahertz pulses and improve the composite insulator defect detection accuracy.
An embodiment of the invention provides a composite insulator defect detection method based on terahertz waves, which comprises the following steps:
collecting terahertz time-domain incident waves incident to the composite insulator and terahertz time-domain reflected waves reflected back by the composite insulator;
converting the terahertz time-domain incident wave into a terahertz frequency-domain incident wave and converting the terahertz time-domain reflected wave into a terahertz frequency-domain reflected wave;
constructing a frequency domain expression of the terahertz frequency domain reflected wave based on the terahertz frequency domain incident wave, the transfer function of the composite insulator and a preset correction term;
solving the frequency domain expression to obtain a frequency domain optimal solution of the transfer function;
converting the frequency domain optimal solution of the transfer function into a time domain waveform of the transfer function; and
and analyzing the time domain waveform based on the transfer function to obtain a defect detection result of the composite insulator.
Preferably, the method further comprises:
collecting terahertz time-domain reflected waves reflected back by a metal plate; and
and taking the terahertz time-domain reflected wave reflected back by the metal plate as a terahertz time-domain incident wave incident to the composite insulator.
Preferably, the step of converting the terahertz time-domain incident wave into a terahertz frequency-domain incident wave and the step of converting the terahertz time-domain reflected wave into a terahertz frequency-domain reflected wave include:
and converting the terahertz time-domain incident wave into the terahertz frequency-domain incident wave and converting the terahertz time-domain reflected wave into the terahertz frequency-domain reflected wave by utilizing a Fourier transform algorithm.
Preferably, the frequency domain expression is: y (w) ═ h (w) × x (w) + e, where y (w) is the thz frequency domain reflected wave, x (w) is the thz frequency domain incident wave, h (w) is the transfer function, and e is the preset correction term.
Preferably, the step of solving the frequency domain expression to obtain the frequency domain optimal solution of the transfer function includes:
carrying out regularized transformation on the frequency domain expression by utilizing a Tikhonov regularization algorithm; and
and solving the converted expression to obtain the optimal frequency domain solution of the transfer function.
Preferably, the frequency domain optimal solution H of the transfer function is: h ═ X (w)]T*Y(w)/[(X(w)]TX (w) + λ I), wherein [ X (w)]TIs the transpose matrix of X (w), I is the identity matrix, and λ is the predetermined coefficient.
Preferably, the time-domain waveform of the transfer function is composed of a plurality of unipolar pulses, and the step of obtaining the defect detection result of the composite insulator based on the time-domain waveform of the transfer function includes:
and analyzing the time domain position and the amplitude of each unipolar pulse to obtain a defect detection result of the composite insulator.
Preferably, after the step of solving the frequency domain expression to obtain the frequency domain optimal solution of the transfer function, the method further includes:
and carrying out interpolation processing on the frequency domain optimal solution of the transfer function by utilizing a cubic spline interpolation algorithm.
The invention provides a terahertz wave-based composite insulator defect detection device, which comprises a processor and a memory, wherein the memory is stored with a plurality of computer programs, and the processor is used for realizing the steps of the terahertz wave-based composite insulator defect detection method when executing the computer programs stored in the memory.
An embodiment of the present invention further provides a computer-readable storage medium, where a plurality of instructions are stored, and the plurality of instructions may be executed by one or more processors to implement the steps of the terahertz wave-based composite insulator defect detection method.
Compared with the prior art, the composite insulator defect detection device and method based on the terahertz waves and the computer readable storage medium solve the problem of transfer function waveforms representing composite insulator interface information by performing discrete deconvolution processing on terahertz incident signals and reflected signals, and analyze the time domain position and amplitude of each pulse in the transfer function waveforms to realize evaluation on the composite insulator interface, so that the composite insulator defects are diagnosed, the possibility of overlapping of terahertz pulses can be reduced by deconvolution algorithm processing, the composite insulator defect detection precision is improved, and the defects with smaller sizes can be diagnosed.
Drawings
Fig. 1 is a schematic configuration diagram of a composite insulator defect detection system according to an embodiment of the present invention.
Fig. 2 is a functional block diagram of a composite insulator defect detection apparatus according to an embodiment of the present invention.
Fig. 3 is a functional block diagram of a composite insulator defect detection program according to an embodiment of the present invention.
Fig. 4 is a schematic structural diagram of a terahertz wave generating apparatus according to an embodiment of the present invention.
Fig. 5(a) -5(d) are waveform diagrams of detection waveforms obtained by the composite insulator according to the embodiment of the present invention by using a conventional terahertz detection method.
Fig. 6(a) -6(d) are waveform diagrams of detection waveforms obtained by the composite insulator according to the embodiment of the present invention by the terahertz detection method using deconvolution processing.
Fig. 7 is a flowchart of a composite insulator defect detection method according to an embodiment of the present invention.
Description of the main elements
The following detailed description will further illustrate the invention in conjunction with the above-described figures.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is further noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Fig. 1 is a schematic structural diagram of a composite insulator defect detection system based on terahertz waves according to a preferred embodiment of the present invention.
The composite insulator defect detection system 1 includes a composite insulator defect detection apparatus 100 and a composite insulator 200. The composite insulator defect detection device 100 is configured to generate a terahertz wave to be incident on the composite insulator 200 and collect a terahertz reflected wave reflected by the composite insulator 200, and the composite insulator defect detection device 100 is further configured to analyze the terahertz reflected wave to obtain a defect detection result of the composite insulator 200.
In one embodiment, the main components of the composite insulator 200 may include a shed, a sheath, a mandrel, a fitting, and a grading ring. Because the composite insulator 200 has a plurality of dielectric materials, various defects are easily generated at the interface due to long-term live-line operation under severe outdoor conditions, including but not limited to the defects of bubbles, debonding, cracks and even breakage of the core rod in the sheath, and the defects may gradually expand in the continuous operation process of the composite insulator 200 after being generated, and finally, power accidents such as string breakage and equipment breakdown of the composite insulator 200 are caused. Therefore, it is important to find the defects in the composite insulator 200 in time at the initial stage of formation, the interface condition of the composite insulator 200 is complex, and the defects with small size formed in the composite insulator 200 at the early stage have certain detection difficulty by adopting the existing detection method. The embodiment of the invention exemplifies that on the basis of the traditional terahertz wave nondestructive testing method, the deconvolution algorithm is used for carrying out transformation processing on the detected time domain waveform, and the method can be further suitable for detecting the defect of the small size of the composite insulator 200.
It is understood that in other embodiments of the present invention, the deconvolution terahertz wave detection method shown in the present invention can also be used in other product detections.
Fig. 2 is a schematic diagram of a composite insulator defect detection apparatus according to a preferred embodiment of the present invention.
The composite insulator defect detection apparatus 100 includes a memory 10, a processor 20, a composite insulator defect detection program 30 stored in the memory 10 and executable on the processor 20, and a terahertz wave generation apparatus 40. The processor 20 implements steps in an embodiment of the composite insulator defect detection method, such as steps S700 to S710 shown in fig. 7, when executing the composite insulator defect detection program 30. Alternatively, the processor 20 implements the functions of the modules in the composite insulator defect detection program embodiment, such as the modules 101 to 106 in fig. 3, when executing the composite insulator defect detection program 30.
The composite insulator defect detection program 30 may be divided into one or more modules, which are stored in the memory 10 and executed by the processor 20 to accomplish the present invention. The one or more modules may be a series of computer program instruction segments capable of performing specific functions, which are used to describe the execution process of the composite insulator defect detection program 30 in the composite insulator defect detection apparatus 100. For example, the composite insulator defect detection program 30 may be divided into an acquisition module 101, a first conversion module 102, a construction module 103, a calculation module 104, a second conversion module 105 and an analysis module 106 in fig. 3. Specific functions of the modules refer to the functions of the modules in fig. 3 below.
It will be understood by those skilled in the art that the schematic diagram is merely an example of the composite insulator defect detecting apparatus 100, and does not constitute a limitation to the composite insulator defect detecting apparatus 100, and may include more or less components than those shown, or some components in combination, or different components, for example, the composite insulator defect detecting apparatus 100 may further include a display device, a bus, etc.
The terahertz wave generating device 40 can generate a terahertz wave, which is preferably a bipolar terahertz pulse wave, and when the composite insulator 200 is placed on a stage (not shown) for detection, the terahertz wave generated by the terahertz wave generating device 40 is preferably vertically incident to the composite insulator 200.
It is understood that, in other embodiments of the present invention, the terahertz wave generating device 40 may be independently installed in the composite insulator defect detecting device 100.
The Processor 20 may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor 20 may be any conventional processor or the like, and the processor 20 may be connected to the various parts of the composite insulator defect inspection device 100 using various interfaces and buses.
The memory 10 may be used to store the composite insulator defect detecting program 30 and/or modules, and the processor 20 may implement various functions of the composite insulator defect detecting apparatus 100 by running or executing the computer program and/or modules stored in the memory 10 and calling data stored in the memory 10. The memory 10 may include high speed random access memory and may also include non-volatile memory such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), at least one magnetic disk storage device, a Flash memory device, or other non-volatile solid state storage device.
Fig. 3 is a functional block diagram of a composite insulator defect detection process according to a preferred embodiment of the present invention.
Referring to fig. 3, the composite insulator defect detecting program 30 may include an acquisition module 101, a first conversion module 102, a construction module 103, a calculation module 104, a second conversion module 105, and an analysis module 106. In one embodiment, the modules may be programmable software instructions stored in the memory 10 and called to be executed by the processor 20. It will be appreciated that in other embodiments, the modules may also be program instructions or firmware (firmware) that are resident in the processor 20.
The acquisition module 101 is configured to acquire a terahertz time-domain incident wave incident to the composite insulator 200 and a terahertz time-domain reflected wave reflected back by the composite insulator 200.
In an embodiment, when a terahertz wave emitted by the terahertz wave generating device 40 enters the composite insulator 200, the terahertz wave is reflected at an interface of the composite insulator 200, and the collecting module 101 can collect a terahertz time-domain reflected wave reflected back through the composite insulator 200.
In an embodiment, it is difficult to directly collect the terahertz time-domain incident wave incident to the composite insulator 200 through the collection module 101, and the metal has a total reflection effect on the terahertz wave, so that the reflected wave of the metal plate can be used as an equivalent substitute. Specifically, the collecting module 101 may collect the terahertz time-domain reflected wave reflected back by the metal plate, and the terahertz time-domain reflected wave reflected back by the metal plate may be used as an equivalent waveform of the terahertz time-domain incident wave incident to the composite insulator 200.
As shown in fig. 4, the terahertz wave generating apparatus 40 includes a femtosecond laser source 401, a polarization beam splitter 402, a photoconductive antenna 403, a power source 404, and a time delay control system 405. The power supply 404 is used to provide an electric field bias to the photoconductive antenna 403, and the femtosecond laser source 401 generates femtosecond laser light which is divided into pump light for generating terahertz pulses and probe light for terahertz wave detection after being irradiated to the polarization beam splitter 402. The pumping light can irradiate onto the photoconductive antenna 403 made of GaAs material under the action of the reflector and the lens to generate a large number of photo-generated carriers, the characteristics of the photoconductive antenna 403 and the pumping light pulse width jointly determine that the frequency band of electromagnetic waves generated by the photo-generated carriers is in the terahertz frequency band, the electromagnetic waves generated by the photo-generated carriers can be focused and calibrated under the action of the parabolic mirror, and are converted into actually emitted bipolar terahertz pulse waves under the action of the time delay control system 405. The maximum delay time of the time delay control system 405 is about 300ps, the femtosecond laser source 401 can adopt a titanium-sapphire femtosecond laser source, the center wavelength is 980nm, the pulse width is 80fs, the repetition frequency is 100MHz, the output power is 20mW, and the frequency range of the finally generated terahertz wave is as follows: 0.02 to 5 THz. Since the signal output by the terahertz detector (not shown) is very weak, the detected current is generally at the nA level and is easily annihilated in the noise signal, and therefore the composite insulator defect detection apparatus 100 needs to extract the signal by means of a lock-in amplifier (not shown). Specifically, the acquisition module 101 may acquire the waveform amplified by the lock-in amplifier.
In other embodiments of the present invention, the collection module 101 may also be integrated in the terahertz wave generating device 40.
The first conversion module 102 is configured to convert the terahertz time-domain incident wave into a terahertz frequency-domain incident wave and convert the terahertz time-domain reflected wave into a terahertz frequency-domain reflected wave.
In an embodiment, the first conversion module 102 may convert the terahertz time-domain incident wave into the terahertz frequency-domain incident wave and convert the terahertz time-domain reflected wave into the terahertz frequency-domain reflected wave by using a fourier transform algorithm.
The building module 103 is configured to build a frequency domain expression of the terahertz frequency domain reflected wave based on the terahertz frequency domain incident wave, the transfer function of the composite insulator 200, and a preset correction term.
In an embodiment, the preset correction term is used for fitting errors caused by instruments and/or measurement environments during a measurement process, and the transfer function of the composite insulator 200 can be used for representing interface information of the composite insulator 200. The frequency domain expression may be: y (w) ═ h (w) × x (w) + e, where y (w) is the thz frequency domain reflected wave, x (w) is the thz frequency domain incident wave, h (w) is the transfer function, and e is the preset correction term.
The calculating module 104 is configured to solve the frequency domain expression to obtain a frequency domain optimal solution of the transfer function.
In an embodiment, after the frequency domain expression of the terahertz frequency domain reflected wave is established, the frequency domain expression may be solved to obtain a frequency domain optimal solution of the transfer function. Because the solution of h (w) is an inverse problem, and the actual situation h (w) is often pathological, the calculation module 104 may perform regularization transformation on the frequency domain expression by using a Tikhonov regularization algorithm in the solution process, and then solve the transformed expression to obtain the frequency domain optimal solution of the transfer function. Specifically, in the solving process, a Tikhonov regularization method is adopted to convert the frequency domain expression into an adaptive problem, and a preset coefficient λ is added to avoid h (w) from appearing a large value in the solution, so that the solving problem can be converted into the following optimization problem:
let J have a partial derivative equal to 0 with respect to H (w), it can be obtained that the optimization term J takes a minimum value when H (w) satisfies the formula (1), which is obtained: h ═ X (w)]T*Y(w)/[(X(w)]TX (w) + λ I), wherein [ X (w)]TIs a transpose matrix of X (w), I is an identity matrix, and H is a frequency domain optimal solution of the transfer function.
In an embodiment, after the calculation module 104 obtains the frequency domain optimal solution of the transfer function by solving, the frequency domain optimal solution of the transfer function may further be interpolated by using a cubic spline interpolation algorithm.
The second conversion module 105 is configured to convert the frequency-domain optimal solution of the transfer function into a time-domain waveform of the transfer function.
In an embodiment, the second conversion module 105 may perform inverse fourier transform on the frequency domain optimal solution of the transfer function to obtain a time domain waveform of the transfer function, so as to implement deconvolution processing.
The analysis module 106 is configured to obtain a defect detection result of the composite insulator 200 based on the time domain waveform analysis of the transfer function.
In one embodiment, the time domain waveform of the transfer function is composed of a plurality of unipolar pulses, each pulse representing the time and attenuation of the reflection of the corresponding interface of composite insulator 200. It can be understood that the longer the time that the terahertz incident wave pulse propagates before being reflected by a certain interface is, the later the time domain position of the pulse is, the larger the pulse amplitude is, and the smaller the attenuation degree of the terahertz reflected pulse is compared with the incident time, so that the interface condition of the composite insulator 200 can be evaluated by analyzing the time domain position and amplitude of each pulse, and the defect can be diagnosed. Specifically, the analysis module 106 may obtain the defect detection result of the composite insulator 200 by analyzing the time domain position and the amplitude of each unipolar pulse.
In an embodiment, the analysis module 106 may be omitted, and the external computer may analyze the time-domain waveform of the transfer function to obtain the defect detection result of the composite insulator 200. Specifically, an analysis program is written by using Matlab, and the time domain waveform of the transfer function is automatically processed by using the analysis program, so that a detection result can be obtained.
Referring to fig. 5(a) -5(d) and fig. 6(a) -6(d), composite insulators 200 with different sizes of air gap defects are tested, and air gap characteristic pulses are extracted and analyzed after deconvolution. The terahertz waves obtained by the conventional terahertz detection method are shown in fig. 5(a) -5(d), and the waveforms obtained after deconvolution processing are respectively shown in fig. 6(a) -6(d), wherein fig. 5(a) and 6(a) are free of air gap defects, fig. 5(b) and 6(b) are 0.17mm, fig. 5(c) and 6(c) are 0.51mm, and fig. 5(d) and 6(d) are 1.14 mm. In a reflection waveform obtained by a traditional method, a first pulse is a terahertz pulse reflected by the surface of silicon rubber, and then two opposite-phase pulses of the upper surface and the lower surface of an air gap are obtained. It can be seen that the two pulses in FIG. 5(d) have substantially no overlap due to the larger air gap defect size, the negative peaks of the two pulses in FIG. 5(c) have a partial overlap, and the negative peaks of the two pulses in FIG. 5(b) have nearly overlapped together due to the smaller air gap defect size. Fig. 6(a) -6(d) respectively show the deconvolution processing results of the four waveforms in fig. 5(a) -5(d), the main pulse is a pulse with positive polarity after conversion, the width is narrow, the peak value is high, and then the two opposite-phase reflected pulses on the upper and lower surfaces of the air gap are deconvolved to become two unimodal pulses with opposite polarities, and as can be seen from fig. 6(b), the air gap defect size is minimum, and fig. 5(b) with the highest overlap degree can also separate two opposite-phase unipolar pulses after deconvolution processing. Therefore, the waveform overlapping phenomenon caused by the undersize of the defect can be effectively relieved through deconvolution processing, and the identification and diagnosis of the defect of the composite insulator 200 are facilitated.
Fig. 7 is a flowchart of a composite insulator defect detection method based on terahertz waves in an embodiment of the present invention. The order of the steps in the flow chart may be changed and some steps may be omitted according to different needs.
Step S700, collecting a terahertz time-domain incident wave incident to the composite insulator 200 and a terahertz time-domain reflected wave reflected back by the composite insulator 200.
In one embodiment, when a terahertz wave emitted by the terahertz wave generating device 40 enters the composite insulator 200, the terahertz wave is reflected at an interface of the composite insulator 200, and a terahertz time-domain reflected wave reflected back through the composite insulator 200 can be collected.
In one embodiment, since it is difficult to directly collect the terahertz time-domain incident wave incident on the composite insulator 200, the metal has a total reflection effect on the terahertz wave, and thus the reflected wave of the metal plate can be used as an equivalent substitute. Specifically, the terahertz time-domain reflected wave reflected back by the metal plate may be collected, and the terahertz time-domain reflected wave reflected back by the metal plate may be used as an equivalent waveform of the terahertz time-domain incident wave incident to the composite insulator 200.
Step S702, converting the terahertz time-domain incident wave into a terahertz frequency-domain incident wave and converting the terahertz time-domain reflected wave into a terahertz frequency-domain reflected wave.
In one embodiment, a fourier transform algorithm may be used to convert the terahertz time-domain incident wave into the terahertz frequency-domain incident wave and to convert the terahertz time-domain reflected wave into the terahertz frequency-domain reflected wave.
Step S704, a frequency domain expression of the terahertz frequency domain reflected wave is constructed based on the terahertz frequency domain incident wave, the transfer function of the composite insulator 200, and a preset correction term.
In an embodiment, the preset correction term is used for fitting errors caused by instruments and/or measurement environments during a measurement process, and the transfer function of the composite insulator 200 can be used for representing interface information of the composite insulator 200. The frequency domain expression may be: y (w) ═ h (w) × x (w) + e, where y (w) is the thz frequency domain reflected wave, x (w) is the thz frequency domain incident wave, h (w) is the transfer function, and e is the preset correction term.
Step S706, solving the frequency domain expression to obtain a frequency domain optimal solution of the transfer function.
In an embodiment, after the frequency domain expression of the terahertz frequency domain reflected wave is established, the frequency domain expression may be solved to obtain a frequency domain optimal solution of the transfer function. Because the solution of h (w) is an inverse problem, and the actual situation h (w) is often pathological, the frequency domain expression may be regularized and transformed by using a Tikhonov regularization algorithm in the solution process, and then the transformed expression is solved to obtain the frequency domain optimal solution of the transfer function. Specifically, in the solving process, a Tikhonov regularization method is adopted to convert the frequency domain expression into an adaptive problem, and a preset coefficient λ is added to avoid h (w) from appearing a large value in the solution, so that the solving problem can be converted into the following optimization problem:
let J have a partial derivative equal to 0 with respect to H (w), it can be obtained that the optimization term J takes a minimum value when H (w) satisfies the formula (1), which is obtained: h ═ X (w)]T*Y(w)/[(X(w)]TX (w) + λ I), wherein [ X (w)]TIs a transpose matrix of X (w), I is an identity matrix, and H is a frequency domain optimal solution of the transfer function.
In an embodiment, after the optimal frequency domain solution of the transfer function is obtained by solving, the optimal frequency domain solution of the transfer function may be interpolated by using a cubic spline interpolation algorithm.
Step S708, converting the frequency domain optimal solution of the transfer function into a time domain waveform of the transfer function.
In an embodiment, inverse fourier transform may be performed on the frequency domain optimal solution of the transfer function to obtain a time domain waveform of the transfer function, so as to implement deconvolution processing.
Step S710, analyzing the time domain waveform based on the transfer function to obtain a defect detection result of the composite insulator 200.
In one embodiment, the time domain waveform of the transfer function is composed of a plurality of unipolar pulses, each pulse representing the time and attenuation of the reflection of the corresponding interface of composite insulator 200. It can be understood that the longer the time that the terahertz incident wave pulse propagates before being reflected by a certain interface is, the later the time domain position of the pulse is, the larger the pulse amplitude is, and the smaller the attenuation degree of the terahertz reflected pulse is compared with the incident time, so that the interface condition of the composite insulator 200 can be evaluated by analyzing the time domain position and amplitude of each pulse, and the defect can be diagnosed. Specifically, the defect detection result of the composite insulator 200 may be obtained by analyzing the time domain position and the amplitude of each unipolar pulse.
According to the composite insulator defect detection device and method based on the terahertz waves and the computer-readable storage medium, the terahertz incident signals and the reflected signals are subjected to discrete deconvolution processing to obtain the transfer function waveform representing the composite insulator interface information, the time domain position and the amplitude of each pulse in the transfer function waveform are analyzed, the composite insulator interface is evaluated, accordingly, the composite insulator defects are diagnosed, the possibility of overlapping of the terahertz pulses can be reduced through deconvolution algorithm processing, the composite insulator defect detection precision is improved, and the defects with small sizes can be diagnosed.
It will be apparent to those skilled in the art that other variations and modifications may be made in accordance with the invention and its spirit and scope in accordance with the practice of the invention disclosed herein.
Claims (10)
1. A composite insulator defect detection method based on terahertz waves is characterized by comprising the following steps:
collecting terahertz time-domain incident waves incident to the composite insulator and terahertz time-domain reflected waves reflected back by the composite insulator;
converting the terahertz time-domain incident wave into a terahertz frequency-domain incident wave and converting the terahertz time-domain reflected wave into a terahertz frequency-domain reflected wave;
constructing a frequency domain expression of the terahertz frequency domain reflected wave based on the terahertz frequency domain incident wave, the transfer function of the composite insulator and a preset correction term;
solving the frequency domain expression to obtain a frequency domain optimal solution of the transfer function;
converting the frequency domain optimal solution of the transfer function into a time domain waveform of the transfer function; and
and analyzing the time domain waveform based on the transfer function to obtain a defect detection result of the composite insulator.
2. The method of claim 1, wherein the method further comprises:
collecting terahertz time-domain reflected waves reflected back by a metal plate; and
and taking the terahertz time-domain reflected wave reflected back by the metal plate as a terahertz time-domain incident wave incident to the composite insulator.
3. The method of claim 1, wherein the steps of converting the terahertz time-domain incident wave into a terahertz frequency-domain incident wave and converting the terahertz time-domain reflected wave into a terahertz frequency-domain reflected wave comprise:
and converting the terahertz time-domain incident wave into the terahertz frequency-domain incident wave and converting the terahertz time-domain reflected wave into the terahertz frequency-domain reflected wave by utilizing a Fourier transform algorithm.
4. The method of claim 1, wherein the frequency domain expression is: y (w) ═ h (w) × x (w) + e, where y (w) is the thz frequency domain reflected wave, x (w) is the thz frequency domain incident wave, h (w) is the transfer function, and e is the preset correction term.
5. The method of claim 4, wherein solving the frequency domain expression to obtain a frequency domain optimal solution for the transfer function comprises:
carrying out regularized transformation on the frequency domain expression by utilizing a Tikhonov regularization algorithm; and
and solving the converted expression to obtain the optimal frequency domain solution of the transfer function.
6. The method of claim 5, wherein the frequency domain optimal solution H for the transfer function is: h ═ X (w)]T*Y(w)/[(X(w)]TX (w) + λ I), wherein [ X (w)]TIs the transpose matrix of X (w), I is the identity matrix, and λ is the predetermined coefficient.
7. The method of claim 1, wherein the time domain waveform of the transfer function is comprised of a plurality of unipolar pulses, and wherein the step of obtaining the defect detection result of the composite insulator based on the time domain waveform of the transfer function comprises:
and analyzing the time domain position and the amplitude of each unipolar pulse to obtain a defect detection result of the composite insulator.
8. The method of claim 1, wherein said step of solving said frequency domain expression to obtain a frequency domain optimal solution for said transfer function further comprises:
and carrying out interpolation processing on the frequency domain optimal solution of the transfer function by utilizing a cubic spline interpolation algorithm.
9. A terahertz wave-based composite insulator defect detection apparatus, the apparatus comprising a processor and a memory, the memory having a plurality of computer programs stored thereon, wherein the processor is configured to implement the steps of the terahertz wave-based composite insulator defect detection method according to any one of claims 1 to 8 when executing the computer programs stored in the memory.
10. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a plurality of instructions executable by one or more processors to implement the steps of the terahertz wave-based composite insulator defect detection method according to any one of claims 1 to 8.
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| CN113884014B (en) * | 2021-09-18 | 2024-02-27 | 山东省科学院自动化研究所 | Terahertz metal substrate multi-coating high-resolution thickness measurement method and device |
| CN114397267B (en) * | 2022-01-18 | 2023-08-08 | 清华大学深圳国际研究生院 | Terahertz imaging optimization method, computer device and storage medium |
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