CN113758995A - Multi-frequency multi-channel digital eddy current flaw detection device - Google Patents
Multi-frequency multi-channel digital eddy current flaw detection device Download PDFInfo
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
- G01N27/82—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws
- G01N27/90—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents
- G01N27/904—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables for investigating the presence of flaws using eddy currents with two or more sensors
Abstract
The invention provides a multi-frequency multi-channel digital eddy current flaw detection device, which comprises a probe wire: the device is used for receiving the multi-frequency excitation signal, detecting the tested piece and collecting an eddy current signal; the result is; adjustable gain amplifier circuit: and the comparison result is obtained and is subjected to differential amplification to determine a defect signal. The invention supports multi-frequency parallel excitation. The flaw detection device technically realizes multi-frequency multi-channel flaw detection, and simultaneously supports a Bobbin (Bobbin) probe and a rotary probe so as to reduce the influence on the result.
Description
Technical Field
The invention relates to the technical field of nondestructive testing and flaw detection, in particular to a multi-frequency multi-channel digital eddy current flaw detection device.
Background
The eddy current flaw detection technology is one of the conventional nondestructive technologies, and the current flaw detection methods such as multi-frequency eddy current, pulse eddy current, low-frequency eddy current and the like are successfully applied. Several countries have also established and implemented various eddy current testing standards. China starts to research the technology from the middle of the 60 th generation of the 20 th century, the development is faster in the middle of the 70 th generation, and complete sets of eddy current flaw detection instrument equipment can be developed in 80 th generation and flaw detection standards are established. At present, the eddy current flaw detection technology in China is applied to various departments of metallurgy, machinery, aerospace, aviation, electric power, chemical engineering, military and civil use, and the function and application range of the eddy current flaw detection technology are gradually expanded. The eddy current nondestructive testing mainly has the following advantages:
the detection speed is high, and the automation is easy to realize;
the detection sensitivity of the surface and subsurface defects is high;
the method has wide application range, and can be used in special occasions where other detection methods such as high temperature, thin tube, hollow surface and the like are difficult to detect;
no coupling agent is needed;
the detection result can be displayed in real time and can be stored for a long time.
Due to the advantages, the eddy current inspection technology is widely applied to the inspection of the processing and manufacturing of various metal devices and the operation and maintenance of equipment. In particular, in the detection of the steam generator pipe of the nuclear power station, the eddy current detection has an irreplaceable position due to the characteristics of high speed and high efficiency.
The eddy current flaw detection frequency has a large relationship with the sensitivity of detecting a flaw, and when selecting the flaw detection frequency, factors such as the length of the detection coil and the flaw detection speed are considered in addition to the position (inner wall or outer wall) of the flaw to be detected, the shape and the size. The number of probes and different types of probes influence the flaw detection result, but in the prior art, multi-frequency parallel detection does not exist, and because the existing detection devices are direct detection devices and cannot perform signal regulation during testing, single-frequency detection is performed; moreover, it is difficult to display various signal states in the flaw detection process in a signal visualization manner, and only the final result can be displayed.
Disclosure of Invention
The invention provides a multi-frequency multi-channel digital eddy current flaw detection device, which is used for solving the problem that the flaw detection device technically realizes multi-frequency multi-channel flaw detection, and simultaneously supports a Bobbin (Bobbin) probe and a rotary probe so as to reduce the influence on the result.
A multi-frequency multi-channel digital eddy current flaw detection device comprises:
a probe line: the device is used for receiving the multi-frequency excitation signal, detecting the tested piece and collecting an eddy current signal;
a measurement comparison circuit: the eddy current signal acquisition module is used for acquiring an eddy current signal, comparing the signal and determining a comparison result;
adjustable gain amplifier circuit: and the comparison result is obtained and is subjected to differential amplification to determine a defect signal.
As an embodiment of the present invention: the digital eddy current inspection device further includes:
an excitation source: the multi-frequency parallel multi-frequency excitation signal is acquired, and the multi-frequency excitation signal controls the probe head to carry out flaw detection;
FPGA core board: the eddy current signal acquisition module is used for receiving a user instruction, executing eddy current signal acquisition and carrying out digital conversion;
a PC machine: the method is used for setting parameters of the multi-frequency excitation signal, acquiring the eddy current signal after digital conversion, and determining an impedance diagram of a tested piece.
As an embodiment of the present invention: the measurement comparison circuit includes: the device comprises a comparator, a trigger, a pulse transmitting circuit, a delayer and a state reading register; wherein the content of the first and second substances,
the positive input end of the comparator is electrically connected with the probe line;
the reverse input end of the comparator is electrically connected with a preset standard signal end;
the trigger is electrically connected with the pulse transmitting circuit through a dual pulse trigger;
the output end of the pulse transmitting circuit is electrically connected with the time delay device;
the delayer is electrically connected with the output end of the comparator;
the state reading register is electrically connected with the output end of the comparator and the time delay unit.
As an embodiment of the present invention: the adjustable gain amplification circuit comprises: a gain amplifier and an A/D conversion chip;
the output end of the gain amplifier is electrically connected with the input end of the A/D conversion chip;
the input end of the gain amplifier is electrically connected with the measurement comparison circuit; wherein the content of the first and second substances,
the gain amplifier is used for acquiring the compared eddy current signals and carrying out difference amplification on the eddy current signals according to the comparison result to generate defect signals,
the A/D conversion chip is used for converting the defect signal into a digital quantity, and the digital quantity is used for generating an impedance diagram of the tested piece through the PC.
As an embodiment of the present invention: the digital eddy current inspection device further includes: the device comprises a communication circuit, a multi-frequency excitation signal circuit, a monitoring circuit and an RPC drive circuit;
the communication circuit is used for performing man-machine interaction and generating an eddy current feedback signal;
the multi-frequency excitation signal circuit is used for acquiring a multi-frequency excitation signal sent by the PC and dividing the multi-frequency excitation signal into a first multi-frequency excitation signal and a second multi-frequency excitation signal through an analog switch; wherein the content of the first and second substances,
the first multi-frequency excitation signal is used for generating and transmitting to a probe head and controlling the probe head to carry out flaw detection;
the second multi-frequency excitation signal is used for forming a standard signal end;
the monitoring circuit is used for acquiring a voltage division signal and a temperature signal of the temperature sensor through the AD conversion chip;
the RPC driving circuit is used for driving the probe line to work.
As an embodiment of the present invention: the digital eddy current inspection device further includes: a power panel circuit and a power adapter; wherein the content of the first and second substances,
the power panel circuit is used for connecting the UPS module and the battery pack and providing power for the probe line and the FPGA core board;
the power panel circuit further comprises a DCDC power module for converting commercial power alternating current into direct current;
the power adapter is electrically connected with the power panel circuit and dynamically adjusts voltage.
As an embodiment of the present invention: the power adapter carries out voltage dynamic regulation and comprises the following steps:
step 1: acquiring initial output voltage of the power panel circuit; wherein the content of the first and second substances,
the initial output voltage is controlled for the first time through voltage droop and a virtual impedance ring;
step 2: receiving, by the power adapter, the initial output voltage;
and step 3: determining a circuit to be powered which is connected with an adaptive output port of the power adapter, and determining the required voltage of the circuit to be powered;
and 4, step 4: according to the initial output voltage and the required voltage, the voltage is adjusted for the second time, and the power is supplied to the circuit to be powered through the adaptive output port; wherein the content of the first and second substances,
and the secondary voltage regulation is distributed through distributed coordination control of the circuit to be powered.
As an embodiment of the present invention: the measurement comparison circuit performs signal comparison, and comprises the following steps:
acquiring a standard eddy current signal according to the multi-frequency excitation signal;
acquiring a first eddy current waveform according to the first standard eddy current signal;
acquiring a second eddy current waveform according to the eddy current signal;
comparing the first eddy current waveform with the second eddy current waveform to obtain an eddy current compensation curve;
constructing a multivariate function model of the eddy current curve according to the eddy current compensation curve;
determining a comparison result according to the multivariate function model; wherein the content of the first and second substances,
the comparison result comprises: mean, mean square error, and contrast threshold curve.
As an embodiment of the present invention: the FPGA core board is used for carrying out digital conversion, wherein the digital conversion comprises eddy current signal digital quantity conversion, delay signal digital quantity conversion, pulse signal digital quantity conversion, standard signal digital quantity conversion, multi-frequency excitation signal digital quantity conversion and defect signal digital quantity conversion.
As an embodiment of the present invention: the PC machine determining the impedance diagram of the tested piece comprises the following steps:
determining an impedance value of the tested piece at each moment when the tested piece is subjected to flaw detection based on the eddy current signals;
converting the impedance value of each moment into a corresponding impedance image;
the impedance maps at each time are spliced to generate an impedance map.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
In the drawings:
FIG. 1 is a system diagram of a multi-frequency multi-channel digital eddy current inspection apparatus according to an embodiment of the present invention;
FIG. 2 is a hardware block diagram of a multi-frequency multi-channel digital eddy current inspection apparatus according to an embodiment of the present invention;
FIG. 3 is a circuit diagram of a measurement comparison circuit of a multi-frequency multi-channel digital eddy current inspection apparatus according to an embodiment of the present invention;
fig. 4 is a communication circuit diagram of a multi-frequency multi-channel digital eddy current inspection apparatus according to an embodiment of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
As shown in fig. 1, 2 and 3, the embodiment of the invention provides a multi-frequency multi-channel digital eddy current inspection device, which comprises:
a probe line: the device is used for receiving the multi-frequency excitation signal, detecting the tested piece and collecting an eddy current signal;
a measurement comparison circuit: the eddy current signal acquisition module is used for acquiring an eddy current signal, comparing the signal and determining a comparison result;
adjustable gain amplifier circuit: and the comparison result is obtained and is subjected to differential amplification to determine a defect signal.
The working principle and the beneficial effects of the technical scheme are as follows:
in the invention, the eddy current detection system consists of a probe line, a measurement comparison circuit and an adjustable gain amplification circuit; eddy current inspection is a method for detecting defects on the surface and near surface of a conductor based on the principle of electromagnetic induction. The probe is used for receiving the multi-frequency excitation signal, applying the multi-frequency excitation signal to an object to be detected, and feeding back a signal returned after the object to be detected acts to the circuit. When a detection probe carrying an alternating current multi-frequency excitation signal is close to a tested conductor test piece, an alternating magnetic field is established by a probe coil, and the alternating magnetic field passes through a conductor to induce eddy current in the conductor. The eddy currents in the conductor also create a magnetic field that causes the probe coil voltage to change, thereby changing the equivalent impedance of the coil. When the surface or the near surface of the conductor has defects, the distribution of an eddy magnetic field is influenced, the change of the eddy can cause the change of the voltage and the impedance of the detection coil, and the existence of the defects in the conductor can be indirectly known according to the change. The multi-frequency excitation signal of the invention adopts multi-frequency parallel alternating current, at most 4-frequency 8-channel detection is supported during actual implementation, but a larger error exists during comparison at a comparison stage, but the invention can reduce the error at a flaw detection stage by signals of the same excitation source in a mode of displaying waveform on a PC through an eddy current signal, because the excitation sources are the same, when the eddy current signal difference occurs, the error can be displayed very clearly, but if different identical excitation sources exist, a reference curve is wrong, and the scheme is based on a high-performance DA conversion chip, adopts a main control chip to realize the design of a multi-frequency excitation signal source, and then carries out a series of differential amplification and filtering to obtain the multi-frequency excitation signal (peak-to-peak values are tested through an oscilloscope, and the peak-to-peak values of multi-frequency excitation signals with different frequencies can be kept at 1.76V), a maximum of 4 frequencies are supported. The flaw detection device technically realizes multi-frequency multi-channel flaw detection, and simultaneously supports a Bobbin (Bobbin) probe and a rotary probe so as to reduce the influence on the result.
In one embodiment of the invention: the digital eddy current inspection device further includes:
an excitation source: the multi-frequency parallel multi-frequency excitation signal is acquired, and the multi-frequency excitation signal controls the probe head to carry out flaw detection;
FPGA core board: the eddy current signal acquisition module is used for receiving a user instruction, executing eddy current signal acquisition and carrying out digital conversion;
a PC machine: the method is used for setting parameters of the multi-frequency excitation signal, acquiring the eddy current signal after digital conversion, and determining an impedance diagram of a tested piece.
The principle of the technical scheme is as follows: the multi-frequency excitation source can detect a signal without passing through a frequency excitation signal, and can also detect flaws through a plurality of excitation sources with the same frequency, so that the stability of a signal source is greatly improved. The FPGA core board not only is a logic control board, but also is a digital quantization logic conversion board for digital conversion, can execute more instruction tasks, and can realize high-efficiency digitization so as to realize digital display. The PC is used for setting the excitation signal, adjusting and controlling the multi-frequency signal from the source, and displaying the impedance diagram in the process of carrying out digital conversion.
The beneficial effects of the above technical scheme are that: the invention can improve the stability of the signal source to a great extent, can execute more instruction tasks, can realize high-efficiency digitization, further digitally display, regulate and control the multi-frequency signal from the source and finally display the impedance diagram.
In one embodiment, the measurement comparison circuit includes: the device comprises a comparator, a trigger, a pulse transmitting circuit, a delayer and a state reading register; wherein the content of the first and second substances,
the positive input end of the comparator is electrically connected with the probe line;
the reverse input end of the comparator is electrically connected with a preset standard signal end;
the trigger is electrically connected with the pulse transmitting circuit through a dual pulse trigger;
the output end of the pulse transmitting circuit is electrically connected with the time delay device;
the delayer is electrically connected with the output end of the comparator;
the state reading register is electrically connected with the output end of the comparator and the time delay unit.
The principle of the technical scheme is as follows: in the practical implementation of the invention, the temperature sensor is also arranged and is used for realizing the detection of the surface temperature of the detected conductor; the temperature sensor can also convert the acquired analog quantity into digital quantity through an A/D conversion chip; at a certain temperature, the two ends of the sensor are a constant resistance value, and the output of the sensor is a stable voltage value because the current passing through the temperature sensor is constant. When the temperature changes in the moment, the resistance value of the temperature sensor processed by pure metal also changes in the moment: r ═ R0(1+γT)(1)；R0The resistance at both ends of the sensor is 0 degree, gamma is the resistance temperature coefficient of the sensor, and T is the temperature detected by the temperature sensor. By using the change of the resistance, the change value of the temperature can be measured:
the power panel circuit adopts an MWA100015A power adapter to convert 220V alternating current commercial power into direct current 15V, and a UPS module and a battery pack are matched to be used as power panel input (the input voltage is 12V). The design of the power panel selects DCDC power modules WDQ75-12S15 and WDQ75-12S3V3 to respectively generate +/-15V and +3.3V, in order to make the isolation of input and output voltages, the output voltage +15V is used as the input of LM1085IS-12 to generate +12V voltage
As can be derived from the law of ohms,
in the present inventor, I is the circuit dc current, U is the stable voltage value output by the sensor, and R is the resistance across the sensor; the measured conductor surface temperature can be obtained by the formulas (1) and (2):
the digital signals are converted into digital signals through an A/D converter and transmitted to a main control device, the digital signals are processed by the main control device and then can be displayed in real time at a PC end, the digital signals are transmitted to a D/A conversion chip after instruction operation is received, and eddy current feedback signals are transmitted to a PC.
In the present invention, as shown in fig. 3, the comparator B is used for comparing signals through the conversion of different excitation signals, so as to realize the comparison and extraction of defect signals in the eddy current signals, and the defect signals are determined based on the compensation signals of different eddy current signals. In the process, two triggers, a first trigger C1 and a second trigger C2, execute the signal triggering action, and the pulse transmitting circuit comprises two parts, namely a pulse generator M and a pulse transmitter F, and transmits a pulse signal. The delay unit Y delays the signals mainly for synchronizing the signals, and the status register Z receives the compared signals for storing the status.
The beneficial effects of the above technical scheme are:
the voltage division signals of each power supply and the output signals of the temperature sensors are connected to the analog input end of the A/D conversion chip to realize voltage monitoring and temperature detection, the A/D conversion chip converts the received signals into digital quantity and then is connected to the main control chip, the main control chip carries out digital demodulation on the received digital quantity and displays the parameters of the eddy current signals and the impedance diagram of the detection coil of the probe in real time at the upper machine position. The flaw detection device technically realizes multi-frequency multi-channel flaw detection, and simultaneously supports a Bobbin (Bobbin) probe and a rotary probe so as to reduce the influence on the result.
In one embodiment of the present invention, the adjustable gain amplifying circuit includes: a gain amplifier and an A/D conversion chip;
the output end of the gain amplifier is electrically connected with the input end of the A/D conversion chip;
the input end of the gain amplifier is electrically connected with the measurement comparison circuit; wherein the content of the first and second substances,
the gain amplifier is used for acquiring the compared eddy current signals and carrying out difference amplification on the eddy current signals according to the comparison result to generate defect signals; ,
the A/D conversion chip is used for converting the defect signal into a digital quantity, and the digital quantity is used for generating an impedance diagram of the tested piece through the PC.
The working principle and the beneficial effects of the technical scheme are as follows: the gain amplifier of the invention is used for amplifying signals, mainly amplifying thicker compensated eddy current signals, and the A/D conversion chip is used for realizing signal conversion. Finally, a visualized impedance diagram is obtained through a PC (personal computer) mall; the main circuit of the invention is based on the core board of the FPGA, and realizes the final visualization and the function control in the technical implementation.
In one embodiment of the present invention,
the digital eddy current inspection device further includes: the device comprises a communication circuit, a multi-frequency excitation signal circuit, a monitoring circuit and an RPC drive circuit;
the communication circuit is used for performing man-machine interaction and generating an eddy current feedback signal;
the multi-frequency excitation signal circuit is used for acquiring a multi-frequency excitation signal sent by the PC and dividing the multi-frequency excitation signal into a first multi-frequency excitation signal and a second multi-frequency excitation signal through an analog switch; wherein the content of the first and second substances,
the first multi-frequency excitation signal is used for generating and transmitting to a probe head and controlling the probe head to carry out flaw detection;
the second multi-frequency excitation signal is used for forming a standard signal end;
the monitoring circuit is used for acquiring a voltage division signal and a temperature signal of the temperature sensor through the AD conversion chip;
the RPC driving circuit is used for driving the probe line to work. The working principle and the beneficial effects of the technical scheme are as follows:
eddy current inspection is a method for detecting defects on the surface and near surface of a conductor based on the principle of electromagnetic induction. The probe is used for receiving the multi-frequency excitation signal, applying the multi-frequency excitation signal to an object to be detected, and feeding back a signal returned after the object to be detected acts to the circuit. When a detection probe carrying an alternating current multi-frequency excitation signal is close to a tested conductor test piece, an alternating magnetic field is established by a probe coil, and the alternating magnetic field passes through a conductor to induce eddy current in the conductor. The eddy currents in the conductor also create a magnetic field that causes the probe coil voltage to change, thereby changing the equivalent impedance of the coil. When the surface or the near surface of the conductor has defects, the distribution of an eddy magnetic field is influenced, the change of the eddy can cause the change of the voltage and the impedance of the detection coil, and the existence of the defects in the conductor can be indirectly known according to the change. The multi-frequency excitation signal adopts multi-frequency parallel alternating current, at most 4-frequency 8-channel detection is supported, the scheme is based on a high-performance DA conversion chip, the design of a multi-frequency excitation signal source is realized by adopting a main control chip, and a series of differential amplification and filtering are carried out to obtain the multi-frequency excitation signal (peak-to-peak values are tested by an oscilloscope, and the peak-to-peak values of the multi-frequency excitation signal with different frequencies can be kept at 1.76V). The flaw detection device technically realizes multi-frequency multi-channel flaw detection, and simultaneously supports a Bobbin (Bobbin) probe and a rotary probe so as to reduce the influence on the result.
In the present invention: the communication circuit is shown in figure 4, and comprises a CPU which realizes the interaction between an operator and equipment through a switch outside a transceiver chip connecting plate, receives an operation instruction and transmits an eddy current feedback signal. After the excitation signals transmitted by the multi-excitation signal circuit from the CPU board pass through the current buffer, the excitation signals are divided into two parts through the analog switch. The probe of the differential amplification circuit is a Bobbin self-comparison probe. If the workpiece has defects, when the first coil passes through the defects (cracks), the loss resistance of an eddy current channel and the reverse magnetic flux generated by the eddy current are reflected to the probe coil, the current magnitude and the phase of the coil are changed, and the amplified defect signals can be obtained by carrying out differential amplification on the coil in the normal area. The analog input end of the A/D conversion chip of the monitoring circuit is connected with the voltage division signal of each power supply and the output signal of the temperature sensor, so that voltage monitoring and temperature detection are realized. A series of serial digital quantities transmitted by the main board of the RPC driving circuit are converted into analog quantities through a D/A chip, and the analog quantities are amplified through a current amplifier to drive the rotary probe.
In one embodiment of the present invention,
the digital eddy current inspection device further includes: a power panel circuit and a power adapter; wherein the content of the first and second substances,
the power panel circuit is used for connecting the UPS module and the battery pack and providing power for the probe line and the FPGA core board;
the power panel circuit further comprises a DCDC power module for converting commercial power alternating current into direct current;
the power adapter is electrically connected with the power panel circuit and dynamically adjusts voltage.
The working principle and the beneficial effects of the technical scheme are as follows:
the power panel circuit adopts a power adapter to convert 220V alternating current commercial power into direct current, and the UPS module and the battery pack are matched to be used as power panel input. The design of the power panel selects the DCDC power module to generate +/-15V and +3.3V respectively, and in order to make isolation of input and output voltages, the output voltage +15V is used as an input to generate a +12V voltage.
In one embodiment of the present invention,
the power adapter carries out voltage dynamic regulation and comprises the following steps:
step 1: acquiring initial output voltage of the power panel circuit; wherein the content of the first and second substances,
the initial output voltage is controlled for the first time through voltage droop and a virtual impedance ring;
step 2: receiving, by the power adapter, the initial output voltage;
and step 3: determining a circuit to be powered which is connected with an adaptive output port of the power adapter, and determining the required voltage of the circuit to be powered;
and 4, step 4: according to the initial output voltage and the required voltage, the voltage is adjusted for the second time, and the power is supplied to the circuit to be powered through the adaptive output port; wherein the content of the first and second substances,
and the secondary voltage regulation is distributed through distributed coordination control of the circuit to be powered.
The working principle and the beneficial effects of the technical scheme are as follows: when the power voltage adapter performs dynamic adjustment of voltage, the voltage adjustment is performed twice, the first realization is voltage conversion adjustment, namely 220V alternating current of a mains supply is converted into direct current and alternating current with other standard voltages; and when the control adjustment is carried out for the second time, the distributed coordination distribution of tooth falling is realized.
The virtual impedance loop conforms to the following equation when a control is performed:
that is, the virtual impedance is a virtual impedance loop of the power strip circuit, and the positive output voltage V1 and the negative output voltage V2 thereof are respectively equal to the positive load current IZ of the positive virtual impedance RZ; negative virtual impedance RF positive load current IF; i.e. the proportional part of the output current, enables the voltage reference value to be reduced as this current increases, thereby providing a load voltage suitable for different circumstances, i.e. detecting the output voltage. Thereby realizing the appearance of a multi-frequency excitation source.
The secondary voltage control conforms to the following equation:
in this formula, K represents a model of distributed control; qijRepresenting the voltage adaptation weight of the ith and jth input circuits to be powered; qiRepresenting the voltage variable of the ith input circuit to be supplied with power; i and j are positive integers which represent several input circuits to be powered. Similarly, the specific value of the principle K for voltage distribution in the coordinated control is also the voltage to be distributed.
In one embodiment of the present invention,
the measurement comparison circuit performs signal comparison, and comprises the following steps:
acquiring a standard eddy current signal according to the multi-frequency excitation signal;
acquiring a first eddy current waveform according to the first standard eddy current signal;
acquiring a second eddy current waveform according to the eddy current signal;
comparing the first eddy current waveform with the second eddy current waveform to obtain an eddy current compensation curve;
constructing a multivariate function model of the eddy current curve according to the eddy current compensation curve;
determining a comparison result according to the multivariate function model; wherein the content of the first and second substances,
the comparison result comprises: mean, mean square error, and contrast threshold curve.
The working principle and the beneficial effects of the technical scheme are as follows: the eddy current signal of the invention is that two eddy current waveform signals exist, which are respectively obtained by different excitation signals, one is a standard eddy current signal and the other is a monitored eddy current signal. When the signal waveform is illustrated, a curve driving is presented, and the final curve is compensated through an eddy current curve, a multivariable function model is constructed, and a comparison result is determined.
In the process, a resume model based on the minimum criterion is obtained through eddy current comparison, and the resume model is preceded by establishing curve functions of a first eddy current waveform and a second eddy current waveform:
in the above formula, a (a) represents a first eddy current waveform signal; b (a) represents the second eddy current waveform signal. CaA coordinate parameter representing a corresponding coordinate point in the first eddy current waveform at time a; daA coordinate parameter representing a corresponding coordinate point in the second eddy current waveform at time a;
the multivariate function model is then simplified by the above formula:
the defect signals can be better extracted by limiting the defect signals between-1 and 1, the difference between the signals is determined, so that time is compared, minE is the minimum difference obtained after comparison, the minimum value of different signal parameters at each moment is extracted, an interval is presented because the signals are fuzzy when the signals exist, and the most accurate result is obtained by obtaining the final minimum value. The final calculation result E is the signal to be compensated.
In one embodiment, the FPGA core board performs digital conversion including eddy current signal digital quantity conversion, time delay signal digital quantity conversion, pulse signal digital quantity conversion, standard signal digital quantity conversion, multi-frequency excitation signal digital quantity conversion and defect signal digital quantity conversion.
The invention aims to realize more accurate monitoring, so that the visualized content is much, the conversion of digital quantity of all generated signals is included, and the result accuracy is also improved.
In one embodiment, the PC determining the impedance profile of the test piece includes:
determining an impedance value of the tested piece at each moment when the tested piece is subjected to flaw detection based on the eddy current signals;
converting the impedance value of each moment into a corresponding impedance image;
the impedance maps at each time are spliced to generate an impedance map.
The impedance map is generated based on the impedance value at each time, and the generated impedance value not only has time continuity, but also can determine the most accurate value even if a threshold value (when a plurality of signals are detected, a plurality of signals with the same frequency are included) is obtained. The threshold is also a minimum range threshold, so that the resulting impedance map is more sharply defined.
In practical implementation, the probe can also pain the position sensor to detect the position of the detected piece, the position sensors are respectively installed at four positions of the probe, the distance between every two adjacent position sensors is equal to d, the position sensor 1 is a coordinate origin, the position sensor 2 is located on the x axis of a coordinate system, the position sensor 3 is located in the coordinate system, and the position sensor 4 is located on the y axis of the coordinate system. Assuming that the coordinates of the probe position are (a, b), according to the pythagorean theorem, the distance from the probe to the position sensor 1 is obtained as follows:
the distance from the probe to the position sensor 2 is:
the probe to position sensor 3 distance is:
the probe to position sensor 4 distance is:
from this, it can be calculated that the real-time position of the probe when the coordinate system moves is:
and calculating to obtain the specific coordinate position of the probe and displaying the specific coordinate position on the PC terminal in real time. The probe is positioned by utilizing electromagnetic induction, so that the method is easy to realize and the cost in the development process is reduced.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A multi-frequency multi-channel digital eddy current flaw detection device is characterized by comprising:
a probe line: the device is used for receiving the multi-frequency excitation signal, detecting the tested piece and collecting an eddy current signal;
a measurement comparison circuit: the eddy current signal acquisition module is used for acquiring an eddy current signal, comparing the signal and determining a comparison result;
adjustable gain amplifier circuit: and the comparison result is obtained and is subjected to differential amplification to determine a defect signal.
2. The multi-frequency multi-channel digital eddy current inspection apparatus according to claim 1, wherein the digital eddy current inspection apparatus further comprises:
an excitation source: the multi-frequency parallel multi-frequency excitation signal is acquired, and the multi-frequency excitation signal controls the probe head to carry out flaw detection;
FPGA core board: the eddy current signal acquisition module is used for receiving a user instruction, executing eddy current signal acquisition and carrying out digital conversion;
a PC machine: the method is used for setting parameters of the multi-frequency excitation signal, acquiring the eddy current signal after digital conversion, and determining an impedance diagram of a tested piece.
3. The multi-frequency multi-channel digital eddy current testing apparatus according to claim 1, wherein the measurement comparison circuit comprises: the device comprises a comparator, a trigger, a pulse transmitting circuit, a delayer and a state reading register; wherein the content of the first and second substances,
the positive input end of the comparator is electrically connected with the probe line;
the reverse input end of the comparator is electrically connected with a preset standard signal end;
the trigger is electrically connected with the pulse transmitting circuit through a dual pulse trigger;
the output end of the pulse transmitting circuit is electrically connected with the time delay device;
the delayer is electrically connected with the output end of the comparator;
the state reading register is electrically connected with the output end of the comparator and the time delay unit.
4. The multi-frequency multi-channel digital eddy current inspection device according to claim 2, wherein the adjustable gain amplification circuit comprises: a gain amplifier and an A/D conversion chip;
the output end of the gain amplifier is electrically connected with the input end of the A/D conversion chip;
the input end of the gain amplifier is electrically connected with the measurement comparison circuit; wherein the content of the first and second substances,
the gain amplifier is used for acquiring the compared eddy current signals and carrying out difference amplification on the eddy current signals according to the comparison result to generate defect signals;
the A/D conversion chip is used for converting the defect signal into a digital quantity, and the digital quantity is used for generating an impedance diagram of the tested piece through the PC.
5. The multi-frequency multi-channel digital eddy current inspection apparatus according to claim 2, further comprising: the device comprises a communication circuit, a multi-frequency excitation signal circuit, a monitoring circuit and an RPC drive circuit;
the communication circuit is used for performing man-machine interaction and generating an eddy current feedback signal;
the multi-frequency excitation signal circuit is used for acquiring a multi-frequency excitation signal sent by the PC and dividing the multi-frequency excitation signal into a first multi-frequency excitation signal and a second multi-frequency excitation signal through an analog switch; wherein the content of the first and second substances,
the first multi-frequency excitation signal is used for generating and transmitting to a probe head and controlling the probe head to carry out flaw detection;
the second multi-frequency excitation signal is used for forming a standard signal end;
the monitoring circuit is used for acquiring a voltage division signal and a temperature signal of the temperature sensor through the AD conversion chip;
the RPC driving circuit is used for driving the probe line to work.
6. The multi-frequency multi-channel digital eddy current inspection apparatus according to claim 1, wherein the digital eddy current inspection apparatus further comprises: a power panel circuit and a power adapter; wherein the content of the first and second substances,
the power panel circuit is used for connecting the UPS module and the battery pack and providing power for the probe line and the FPGA core board;
the power panel circuit further comprises a DCDC power module for converting commercial power alternating current into direct current;
the power adapter is electrically connected with the power panel circuit and dynamically adjusts voltage.
7. The multi-frequency multi-channel digital eddy current inspection device as claimed in claim 6, wherein the power adapter performing the dynamic voltage adjustment comprises the following steps:
step 1: acquiring initial output voltage of the power panel circuit; wherein the content of the first and second substances,
the initial output voltage is controlled for the first time through voltage droop and a virtual impedance ring;
step 2: receiving, by the power adapter, the initial output voltage;
and step 3: determining a circuit to be powered which is connected with an adaptive output port of the power adapter, and determining the required voltage of the circuit to be powered;
and 4, step 4: according to the initial output voltage and the required voltage, the voltage is adjusted for the second time, and the power is supplied to the circuit to be powered through the adaptive output port; wherein the content of the first and second substances,
and the secondary voltage regulation is distributed through distributed coordination control of the circuit to be powered.
8. The multi-frequency multi-channel digital eddy current testing device as claimed in claim 1, wherein the measurement comparison circuit performs signal comparison, comprising the steps of:
acquiring a standard eddy current signal according to the multi-frequency excitation signal;
acquiring a first eddy current waveform according to the first standard eddy current signal;
acquiring a second eddy current waveform according to the eddy current signal;
comparing the first eddy current waveform with the second eddy current waveform to obtain an eddy current compensation curve;
constructing a multivariate function model of the eddy current curve according to the eddy current compensation curve;
determining a comparison result according to the multivariate function model; wherein the content of the first and second substances,
the comparison result comprises: mean, mean square error, and contrast threshold curve.
9. The multi-frequency multi-channel digital eddy current testing device as claimed in claim 2, wherein the FPGA core board performs digital conversion including eddy current signal digital quantity conversion, delay signal digital quantity conversion, pulse signal digital quantity conversion, standard signal digital quantity conversion, multi-frequency excitation signal digital quantity conversion and defect signal digital quantity conversion.
10. The multi-frequency multi-channel digital eddy current testing apparatus according to claim 2, wherein the PC determining the impedance map of the tested piece comprises:
determining an impedance value of the tested piece at each moment when the tested piece is subjected to flaw detection based on the eddy current signals;
converting the impedance value of each moment into a corresponding impedance image;
the impedance maps at each time are spliced to generate an impedance map.
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| CN116068044A (en) * | 2023-03-21 | 2023-05-05 | 辽宁锂想科技有限公司 | Multichannel multi-frequency weld joint flaw detection device |
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