CN109115868A - A kind of depth of defect detection device and method based on impulse eddy current - Google Patents
A kind of depth of defect detection device and method based on impulse eddy current Download PDFInfo
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- 230000024241 parasitism Effects 0.000 description 2
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Abstract
The present invention provides a kind of depth of defect detection device and method based on impulse eddy current, is related to technical field of nondestructive testing.The specific method is as follows: excitation signal generator generates periodic pulse signal and is added in excitation coil both ends after power amplifier module；Detection coil receives magnetic field signal above test specimen, and output is to signal conditioning module after being converted into analog voltage signal；A/D conversion module is given in output after signal conditioning module is filtered analog voltage signal, amplifies；A/D conversion module carries out the analog/digital conversion of signal under the control of trigger collection module, digital signal after conversion is sent into Characteristic parameter identification module identification and obtains characteristic parameter, it is then fed into the depth of defect detection module based on random forest, detects the depth information of defect on test specimen.The physical model for the Pulsed Eddy Current Testing System that apparatus of the present invention are established improves modeling accuracy, reduces the detection error of depth of defect due to considering influence of the inductive loop to characteristic parameter on test specimen.
Description
Technical field
The present invention relates to technical field of nondestructive testing more particularly to a kind of depth of defect detection devices based on impulse eddy current
And method.
Background technique
With gradually lengthening, the gradually increasing of freight volume of domestic and international oil-gas pipeline, the conveying of oil-gas pipeline highly effective and safe
Extensive attention is obtained.Due to prolonged corrosion, wear and unexpected mechanical damage etc., ferromagnetism oil-gas transportation
Pipeline will form various defects.The generation of accident is revealed in order to prevent, it is necessary to using pipe detection device to pipeline
It is detected.Eddy detection technology is a kind of unique and low cost extensive detection technique of high speed, there is uniqueness；With it is super
Sound method is compared with ray method, it does not need couplant, untouchable can be measured, and detection speed is faster；It is right compared with magnetic particle method
Magnetic and non-magnetic material is effective and free from environmental pollution；Compared with osmosis, it does not need cleaning test specimen, may be implemented
Detection automation.It is less for the Pulsed eddy current testing probe of oil-gas pipeline defect and detection method research at present, relevant device
Price is more expensive, detection accuracy is low.
Summary of the invention
It is a kind of based on impulse eddy current the technical problem to be solved by the present invention is in view of the above shortcomings of the prior art, provide
Depth of defect detection device and method reduce the detection error of depth of defect.
In order to solve the above technical problems, the technical solution used in the present invention is:
On the one hand, the present invention provides a kind of depth of defect detection device based on impulse eddy current, comprising: pumping signal occurs
Device, power amplifier module, excitation coil, detection coil, signal conditioning module, A/D conversion module, DSP central processing unit；Institute
It states excitation signal generator to be connected with the input terminal of power amplifier module, the two of the output end of power amplifier module and excitation coil
End is connected, detection coil and excitation coil coaxial placement, the input terminal and the output end phase of detection coil of signal conditioning module
Even, the output end of signal conditioning module is connected with the input terminal of A/D conversion module, output end and the DSP center of A/D conversion module
The input terminal of processing unit is connected；
Cyclic pulse signal is transmitted to power amplification for generating periodic pulse signal by the excitation signal generator
Module；
The periodic pulse signal that the power amplifier module is used to generate excitation signal generator carries out voltage, electric current is put
Excitation coil both ends are added to after big；
The excitation coil generates alternating magnetic field for being passed through amplified periodic pulse signal；
The detection coil is used to detect magnetic field signal above test specimen, and convert thereof into voltage signal export to
Signal conditioning unit；
The signal conditioning module for export after the voltage signal detected in detection coil is filtered, is amplified to
A/D converting unit；
The A/D conversion module is used to convert digital voltage signal for the voltage signal that signal conditioning module exports, and
Digital signal after conversion is exported to DSP data processing module；
The DSP central processing unit includes trigger collection module, Characteristic parameter identification module, lacking based on random forest
Fall into depth detection module；The trigger collection module is used to control the D/A switch that A/D conversion module carries out voltage；The spy
Sign parameter identification module is used to extract the digital voltage signal of the A/D conversion module output after the control of trigger collection module,
Characteristic parameter identification is carried out to the signal by the physical model of the Pulsed Eddy Current Testing System of building, the feature after identification is joined
The number output extremely depth of defect detection module based on random forest；The depth of defect detection module based on random forest is used for
The characteristic parameter that Characteristic parameter identification module is exported detects the depth information of test specimen defect as input, output；
On the other hand, the present invention provides a kind of depth of defect detection method based on impulse eddy current, is based on arteries and veins by one kind
The depth of defect detection device of punching vortex is realized, comprising the following steps:
Step 1: acquiring the magnetic field signal above test specimen with detection coil, and be converted into voltage signal, carry out
After filter and amplification, it is further converted into digital voltage signal；
Step 2: in Characteristic parameter identification module, constructing the physical model of Pulsed Eddy Current Testing System, establish detection line
The complex frequency domain receptance function of voltage response signal on circle, by obtaining detection coil voltage time domain side after reverse drawing Laplace transform
Journey；Again using the digital voltage signal of step 1 as input, variable weight multi-parameter fitting method identification impulse EDDY CURRENT system is utilized
The characteristic parameter of the physical model of system；The physical model of the Pulsed Eddy Current Testing System wherein constructed has 4 characteristic parameters, passes through
The depth of defect information of characteristic parameter reflection test specimen；
Step 3: in the depth of defect detection module based on random forest, using characteristic parameter as input, using being based on
The depth of defect detection method of random forest obtains the depth information of detection test specimen defect.
The step 2 the following steps are included:
Step 2.1: constructing the physical model of Pulsed Eddy Current Testing System；
Step 2.1.1: the equation of change of electric current on excitation coil is sought；Pulse signal is added in excitation coil both ends, signal electricity
Pressure is mutated the amplitude U to pulse signal by 0sWhen, obtain electric current I on excitation coilL1Equation of change are as follows:
Wherein RL1For the equivalent resistance of excitation coil, r is the internal resistance of driving source,τeFor down slope time constant, when t is
Between, e is natural constant；
Step 2.1.2: the induced electromotive force in detection coil is sought；Detection coil detects the magnetic field letter above test specimen
Number, and voltage signal is converted thereof into, obtain the induced electromotive force in detection coil:
Wherein N1、N2Respectively the number of turns of excitation coil and detection coil, k are detection coil and excitation coil single turn magnetic flux
The ratio of amount；
Step 2.1.3: the voltage frequency domain receptance function at detection coil both ends is sought；By detection coil induced electromotive force ε, electricity
The circuit that sense, resistance and parasitic capacitance form, obtains the voltage complex frequency domain receptance function U at detection coil both ends0(s) are as follows:
WhereinR2e、L2e、C2eRespectively equivalent resistance, inductance and the parasitism electricity of detection coil
Hold, s indicates the independent variable of complex frequency domain；
Step 2.1.4: the physical model of Pulsed Eddy Current Testing System is sought；It is general that reverse drawing is carried out to obtained frequency response function
Lars transformation, obtains domain equation when detection coil voltage:
It enablesIt obtains:
Uo(t) physical model of the Pulsed Eddy Current Testing System as acquired, B, C, D, τeFor the characteristic parameter of model；
Step 2.2: using the digital voltage signal of A/D conversion module as input, utilizing variable weight multi-parameter fitting method
The characteristic parameter of the physical model of identification impulse eddy detection system；
Step 2.2.1: by the digital voltage signal U of inputDiConversion is counted as voltage value Ui；
Wherein i=T, 2T ..., nT, T are the sampling period of A/D conversion module, UDiIt is different for same position on test specimen
Moment collected n digital voltage, N are the digit of A/D conversion module, VrefFor the reference voltage of A/D conversion module；
Step 2.2.2: the weight coefficient of variable weight multi-parameter fitting method is determined；Seek UiIn maximum value Umax, it is contemplated that
The rapidity of impulse eddy current decaying, as voltage value UiGreater than 0.368UmaxWhen can more embody the characteristic of vortex, obtain weight system
Number wiExpression formula it is as follows:
Wherein n1To meet U in all voltage valuesi> 0.368UmaxNumber；
Step 2.2.3: the physical model U of Pulsed Eddy Current Testing System is utilizedo(t) U is calculatedo(i) value, i=T,
2T ..., nT, by Uo(i) with voltage value UiDifference is done one by one, by difference Ui-Uo(i) square multiplied by corresponding weight coefficient wi
It sums again, obtains error function E:
Step 2.2.4: error function E is respectively to B, C, D, τePartial derivative is sought, is obtainedAnd
Solve system of equation:
Obtain Characteristic parameter B, C, D, τ of physical modeleValue.
The beneficial effects of adopting the technical scheme are that a kind of lacking based on impulse eddy current provided by the invention
Depth detection apparatus and method are fallen into, the present invention is using the physical model for establishing Pulsed Eddy Current Testing System, it is contemplated that feels on test specimen
It should be vortexed the influence to characteristic parameter, to improve modeling accuracy, reduce the detection error of depth of defect.
Detailed description of the invention
Fig. 1 is the depth of defect detection device overall structure block diagram provided in an embodiment of the present invention based on impulse eddy current；
Fig. 2 is the device figure of test specimen provided in an embodiment of the present invention, excitation coil and detection coil；Wherein, 1, quilt
Test block；2, excitation coil；3, detection coil；
Fig. 3 is detection coil voltage curve provided in an embodiment of the present invention；
Fig. 4 is the voltage curve of part A in detection coil voltage curve provided in an embodiment of the present invention；
Fig. 5 is the depth of defect detection method overview flow chart provided in an embodiment of the present invention based on impulse eddy current；
Fig. 6 is Characteristic parameter identification module work flow chart provided in an embodiment of the present invention.
Specific embodiment
With reference to the accompanying drawings and examples, specific embodiments of the present invention will be described in further detail.Implement below
Example is not intended to limit the scope of the invention for illustrating the present invention.
The method of the present embodiment is as described below:
On the one hand, the present invention provides a kind of depth of defect detection device based on impulse eddy current, as depicted in figs. 1 and 2, packet
It includes: excitation signal generator, power amplifier module, excitation coil, detection coil, signal conditioning module, A/D conversion module, DSP
Central processing unit；The excitation signal generator is connected with the input terminal of power amplifier module, the output of power amplifier module
End is connected with the both ends of excitation coil, detection coil and excitation coil coaxial placement, the input terminal of signal conditioning module and inspection
The output end of test coil is connected, and the output end of signal conditioning module is connected with the input terminal of A/D conversion module, A/D conversion module
Output end be connected with the input terminal of DSP central processing unit；
Cyclic pulse signal is transmitted to power amplification for generating periodic pulse signal by the excitation signal generator
Module；
The periodic pulse signal that the power amplifier module is used to generate excitation signal generator carries out voltage, electric current is put
Excitation coil both ends are added to after big；
The excitation coil generates alternating magnetic field for being passed through amplified periodic pulse signal；
The detection coil is used to detect magnetic field signal above test specimen, and convert thereof into voltage signal export to
Signal conditioning unit；
The signal conditioning module for export after the voltage signal detected in detection coil is filtered, is amplified to
A/D converting unit；
The A/D conversion module is used to convert digital voltage signal for the voltage signal that signal conditioning module exports, and
Digital signal after conversion is exported to DSP data processing module；
The DSP central processing unit includes trigger collection module, Characteristic parameter identification module, lacking based on random forest
Fall into depth detection module；The trigger collection module is used to control the D/A switch that A/D conversion module carries out voltage；The spy
Sign parameter identification module is used to extract the digital voltage signal of the A/D conversion module output after the control of trigger collection module,
Characteristic parameter identification is carried out to the signal by the physical model of the Pulsed Eddy Current Testing System of building, the feature after identification is joined
The number output extremely depth of defect detection module based on random forest；The depth of defect detection module based on random forest is used for
The characteristic parameter that Characteristic parameter identification module is exported detects the depth information of test specimen defect as input, output；
Wherein excitation signal generator generates frequency 100Hz, duty ratio 50%, the periodic pulse signal that amplitude is 200mv,
It is sent into power amplifier module；Power amplifier module selects amplifier TL071 and the concatenated structure type of Darlington transistor, to input pulse
Signal voltage amplification, Darlington transistor push-pull circuit carries out Current amplifier output driving excitation coil, and (parameter is resistance R=12.95
Ω, the number of turns N=500, line footpath dl=0.21mm, internal diameter di=15.6mm, outside diameter doThe high h=10mm of=20.8mm, coil)；Detection
(parameter is resistance R=4.32 Ω, the number of turns N=400, line footpath d to coill=0.21mm, internal diameter di=3mm, outside diameter do=8.5mm,
The high h=10mm of coil) detection test specimen above magnetic field signal, be converted into analog voltage signal, analog voltage signal such as Fig. 3 and figure
Shown in 4；It is then output to signal conditioning module, conditioning circuit is filtered signal, unit is amplified, and finally exports and turns to A/D
Change the mold block；The chip that A/D conversion module uses is ADS7844, and I/O mouthfuls are connected with DSP trigger collection module respectively, and DSP is adopted
TMS320F28335.
ADS7844 converts analog signals into digital signal under the control of DSP trigger collection module and is sent into DSP centre
Manage unit.In dsp in Central Processing Unit, the depth of defect detection method process based on impulse eddy current is as shown in Figure 5；After conversion
Digital signal obtain characteristic parameter by Characteristic parameter identification module identification, be then fed into the depth of defect based on random forest
Detection module obtains the depth information of detection test specimen defect using the depth of defect detection method based on random forest.
On the other hand, the present invention provides a kind of depth of defect detection method based on impulse eddy current, is based on arteries and veins by one kind
The depth of defect detection device of punching vortex is realized, comprising the following steps:
Step 1: acquiring the magnetic field signal above test specimen with detection coil, and be converted into voltage signal, carry out
After filter and amplification, it is further converted into digital voltage signal；
Step 2: in Characteristic parameter identification module, constructing the physical model of Pulsed Eddy Current Testing System, establish detection line
The complex frequency domain receptance function of voltage response signal on circle, by obtaining detection coil voltage time domain side after reverse drawing Laplace transform
Journey；Again using the digital voltage signal of step 1 as input, variable weight multi-parameter fitting method identification impulse EDDY CURRENT system is utilized
The characteristic parameter of the physical model of system；The physical model of the Pulsed Eddy Current Testing System wherein constructed has 4 characteristic parameters, can
Reflect the depth of defect information of test specimen；
Step 3: in the depth of defect detection module based on random forest, using characteristic parameter as input, using being based on
The depth of defect detection method of random forest obtains the depth information of detection test specimen defect.
As shown in fig. 6, the step 2 the following steps are included:
Step 2.1: constructing the physical model of Pulsed Eddy Current Testing System；
Step 2.1.1: the equation of change of electric current on excitation coil is sought；Pulse signal is added in excitation coil both ends, signal electricity
Pressure is mutated the amplitude U to pulse signal by 0sWhen, obtain electric current I on excitation coilL1Equation of change are as follows:
Wherein RL1For the equivalent resistance of excitation coil, r is the internal resistance of driving source,τeFor down slope time constant, take
It is worth related to the vortex incuded above the resistance of coil, inductance, test specimen；T is the time, and e is natural constant, about
2.71828。
Step 2.1.2: the induced electromotive force in detection coil is sought；Detection coil detects the magnetic field letter above test specimen
Number, and voltage signal is converted thereof into, obtain the induced electromotive force in detection coil:
Wherein N1、N2Respectively the number of turns of excitation coil and detection coil, k are detection coil and excitation coil single turn magnetic flux
The ratio of amount；
Step 2.1.3: the voltage frequency domain receptance function at detection coil both ends is sought；By detection coil induced electromotive force ε, electricity
The circuit that sense, resistance and parasitic capacitance form, obtains the voltage complex frequency domain receptance function U at detection coil both ends0(s) are as follows:
WhereinR2e、L2e、C2eRespectively equivalent resistance, inductance and the parasitism electricity of detection coil
Hold, equivalent resistance, inductance and the parasitic capacitance of the detection coil are all and related with the vortex of induction, and s indicates oneself of complex frequency domain
Variable；
Step 2.1.4: the physical model of Pulsed Eddy Current Testing System is sought；It is general that reverse drawing is carried out to obtained frequency response function
Lars transformation, obtains domain equation when detection coil voltage:
It enablesIt obtains:
Uo(t) physical model of the Pulsed Eddy Current Testing System as acquired, B, C, D, τeFor the characteristic parameter of model；
Step 2.2: using the digital voltage signal of A/D conversion module as input, utilizing variable weight multi-parameter fitting method
The characteristic parameter of the physical model of identification impulse eddy detection system；
Step 2.2.1: by the digital voltage signal U of inputDiConversion is counted as voltage value Ui；
Wherein i=T, 2T ..., nT, T are the sampling period of A/D conversion module, UDiIt is different for same position on test specimen
Moment collected n digital voltage, N are the digit of A/D conversion module, VrefFor the reference voltage of A/D conversion module；
Step 2.2.2: the weight coefficient of variable weight multi-parameter fitting method is determined；Seek UiIn maximum value Umax, it is contemplated that
The rapidity of impulse eddy current decaying, as voltage value UiGreater than 0.368UmaxWhen can more embody the characteristic of vortex, therefore weighed
Weight coefficient wiExpression formula it is as follows
Wherein n1To meet U in all voltage valuesi> 0.368UmaxNumber；
Step 2.2.3: the physical model U of Pulsed Eddy Current Testing System is utilizedo(t) U is calculatedo(i) value, i=T,
2T ..., nT, by Uo(i) with voltage value UiDifference is done one by one, by difference Ui-Uo(i) square multiplied by corresponding weight coefficient wi
It sums again, obtains error function E:
Step 2.2.4: error function E is respectively to B, C, D, τePartial derivative is sought, is obtainedAnd
Solve system of equation:
Obtain Characteristic parameter B, C, D, τ of physical modeleValue.
Finally, it should be noted that the above embodiments are merely illustrative of the technical solutions of the present invention, rather than its limitations；Although
Present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that: it still may be used
To modify to technical solution documented by previous embodiment, or some or all of the technical features are equal
Replacement；And these are modified or replaceed, model defined by the claims in the present invention that it does not separate the essence of the corresponding technical solution
It encloses.
Claims (3)
1. a kind of depth of defect detection device based on impulse eddy current, it is characterised in that: include: excitation signal generator, power
Amplification module, excitation coil, detection coil, signal conditioning module, A/D conversion module, DSP central processing unit；The excitation
Signal generator is connected with the input terminal of power amplifier module, and the output end of power amplifier module is connected with the both ends of excitation coil
It connects, detection coil and excitation coil coaxial placement, the input terminal of signal conditioning module are connected with the output end of detection coil, signal
The output end of conditioning module is connected with the input terminal of A/D conversion module, the output end and DSP central processing list of A/D conversion module
The input terminal of member is connected；
Cyclic pulse signal is transmitted to power amplification mould for generating periodic pulse signal by the excitation signal generator
Block；
After the periodic pulse signal that the power amplifier module is used to generate excitation signal generator carries out voltage, Current amplifier
It is added to excitation coil both ends；
The excitation coil generates alternating magnetic field for being passed through amplified periodic pulse signal；
The detection coil is used to detect the magnetic field signal above test specimen, and converts thereof into voltage signal and export to signal
Conditioning unit；
The signal conditioning module is for output after the voltage signal detected in detection coil is filtered, is amplified to A/D
Converting unit；
The A/D conversion module is used to convert the voltage signal that signal conditioning module exports to digital voltage signal, and will turn
Digital signal after changing is exported to DSP data processing module；
The DSP central processing unit includes trigger collection module, Characteristic parameter identification module, the defect depth based on random forest
Spend detection module；The trigger collection module is used to control the D/A switch that A/D conversion module carries out voltage；The feature ginseng
Number identification module is used to extract the digital voltage signal of the A/D conversion module output after the control of trigger collection module, passes through
The physical model of the Pulsed Eddy Current Testing System of building carries out Characteristic parameter identification to the signal, and the characteristic parameter after identification is defeated
Out to the depth of defect detection module based on random forest；The depth of defect detection module based on random forest is used for will be special
The characteristic parameter of parameter identification module output is levied as input, output detects the depth information of test specimen defect.
2. a kind of depth of defect detection method based on impulse eddy current, by described in claim 1 a kind of based on impulse eddy current
Depth of defect detection device realize, it is characterised in that: the following steps are included:
Step 1: acquiring the magnetic field signal above test specimen with detection coil, and be converted into voltage signal, be filtered amplification
Afterwards, it is further converted into digital voltage signal；
Step 2: in Characteristic parameter identification module, constructing the physical model of Pulsed Eddy Current Testing System, establish in detection coil
The complex frequency domain receptance function of voltage responsive signal, domain equation when by obtaining detection coil voltage after reverse drawing Laplace transform；
Again using the digital voltage signal of step 1 as input, variable weight multi-parameter fitting method identification impulse eddy detection system is utilized
Physical model characteristic parameter；The physical model of the Pulsed Eddy Current Testing System wherein constructed has 4 characteristic parameters, passes through spy
Levy the depth of defect information of parameter reflection test specimen；
Step 3: in the depth of defect detection module based on random forest, using characteristic parameter as input, using based on random
The depth of defect detection method of forest obtains the depth information of detection test specimen defect.
3. a kind of depth of defect detection method based on impulse eddy current according to claim 2, it is characterised in that: the step
Rapid 2 the following steps are included:
Step 2.1: constructing the physical model of Pulsed Eddy Current Testing System；
Step 2.1.1: the equation of change of electric current on excitation coil is sought；Pulse signal is added in excitation coil both ends, and signal voltage is by 0
It is mutated the amplitude U of pulse signalsWhen, obtain electric current I on excitation coilL1Equation of change are as follows:
Wherein RL1For the equivalent resistance of excitation coil, r is the internal resistance of driving source,τeFor down slope time constant, t is time, e
For natural constant；
Step 2.1.2: the induced electromotive force in detection coil is sought；Detection coil detect test specimen above magnetic field signal, and by its
It is converted into voltage signal, obtains the induced electromotive force in detection coil:
Wherein N1、N2Respectively the number of turns of excitation coil and detection coil, k are detection coil and excitation coil single turn magnetic flux
Ratio；
Step 2.1.3: the voltage frequency domain receptance function at detection coil both ends is sought；By detection coil induced electromotive force ε, inductance, electricity
The circuit of resistance and parasitic capacitance composition, obtains the voltage complex frequency domain receptance function U at detection coil both ends0(s) are as follows:
WhereinR2e、L2e、C2eThe respectively equivalent resistance, inductance and parasitic capacitance of detection coil, s
Indicate the independent variable of complex frequency domain；
Step 2.1.4: the physical model of Pulsed Eddy Current Testing System is sought；Anti- Laplce is carried out to obtained frequency response function
Transformation, obtains domain equation when detection coil voltage:
It enablesIt obtains:
Uo(t) physical model of the Pulsed Eddy Current Testing System as acquired, B, C, D, τeFor the characteristic parameter of model；
Step 2.2: using the digital voltage signal of A/D conversion module as input, being recognized using variable weight multi-parameter fitting method
The characteristic parameter of the physical model of Pulsed Eddy Current Testing System；
Step 2.2.1: by the digital voltage signal U of inputDiConversion is counted as voltage value Ui；
Wherein i=T, 2T ..., nT, T are the sampling period of A/D conversion module, UDiFor same position different moments on test specimen
Collected n digital voltage, N are the digit of A/D conversion module, VrefFor the reference voltage of A/D conversion module；
Step 2.2.2: the weight coefficient of variable weight multi-parameter fitting method is determined；Seek UiIn maximum value Umax, it is contemplated that pulse
The rapidity of eddy current decay, as voltage value UiGreater than 0.368UmaxWhen can more embody the characteristic of vortex, obtain weight coefficient wi's
Expression formula is as follows
Wherein n1To meet U in all voltage valuesi> 0.368UmaxNumber；
Step 2.2.3: the physical model U of Pulsed Eddy Current Testing System is utilizedo(t) U is calculatedo(i) value, i=T, 2T ..., nT,
By Uo(i) with voltage value UiDifference is done one by one, by difference Ui-Uo(i) square multiplied by corresponding weight coefficient wiIt sums, obtains again
Error function E:
Step 2.2.4: error function E is respectively to B, C, D, τePartial derivative is sought, is obtainedAnd the side of solution
Journey group:
Obtain Characteristic parameter B, C, D, τ of physical modeleValue.
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