A guided wave signal calibration system and method

Abstract

The application discloses a guided wave signal calibration system and method, and belongs to the technical field of aviation structure health monitoring.The guided wave signal calibration method is integrated in an upper computer, a control signal is output to a four-quadrant multiplier by a logic controller to adjust voltage gain, after a guided wave signal to be calibrated enters the guided wave signal calibration system, the guided wave signal to be calibrated sequentially passes through a reverse proportional device, the four-quadrant multiplier and a current feedback type amplifier, and then a calibrated guided wave signal is output.The guided wave signal calibration system and method are simple in design, easy to integrate, high in calibration precision and high in signal-to-noise ratio.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aviation structure health monitoring, and particularly relates to a guided wave signal calibration system and method. BACKGROUND

[0002] During the service of an aircraft, the in-service conditions and failure modes are usually complex and unpredictable, and the aerospace industry usually uses time-based or usage-based periodic maintenance, which is very time-consuming and very expensive. Therefore, structure health monitoring technology supporting real-time online monitoring has great application prospects.

[0003] Structure health monitoring technology is based on intelligent material structure, and intelligent sensing / driving elements are installed in the structure. Physical information of the intelligent sensing / driving elements is obtained by a structure health monitoring system in real time and online, and advanced damage identification algorithms are used to process the obtained signals to extract feature parameters of the structure health status, identify the structure state, and realize online or offline monitoring of the structure. Structure health monitoring technology can monitor and control the state of the aircraft structure during the design, experiment and service of the aircraft, thereby guiding the structural design of the aircraft, reducing maintenance costs, and improving flight safety. Among many structure health monitoring technologies, piezoelectric guided wave-based structure health monitoring technology is widely used because of its advantages of long monitoring distance, large monitoring area, ability to realize regional monitoring, sensitivity to small structural damage, etc. The main method is to excite the driving elements on the structure by high-frequency high-amplitude guided wave voltage signals, collect guided wave response signals on the sensing elements, and use advanced damage imaging algorithms to identify the damage on the structure.

[0004] However, when the piezoelectric guided wave-based structure health monitoring technology is applied to the aircraft structure, there are many time-varying uncertain factors in the real service environment, such as changes in environmental temperature and humidity, operating conditions, and structural boundary conditions, and these time-varying environmental factors may have an uncertain impact on the monitored guided wave signals. In addition, factors such as the material of the aircraft structure, the structure, and the sensor arrangement error will also affect the monitored guided wave signals. The piezoelectric guided wave-based structure health monitoring method compares the signal difference between the health signals and the damage signals monitored before and after the structure damage to characterize the damage. Therefore, the above uncertain changes in the guided wave signals will affect the subsequent structure damage identification.

[0005] Therefore, it is necessary to introduce guided wave calibration in the guided wave acquisition system, taking the guided wave signal affected by time-varying factors, structural changes, sensor differences, etc. as the standard signal, and calibrating the signal affected by the above factors, so as to improve the accuracy of structural damage diagnosis. The change of guided wave signal caused by the above factors is mainly the change of signal amplitude, therefore, for the calibration of guided wave signal, a voltage regulation circuit needs to be introduced in the guided wave conditioner to adjust the voltage gain of the guided wave signal and thus adjust its amplitude, wherein the guided wave conditioner is used to amplify the weak guided wave signal (for details, see patent No. CN111697946A). The circuit should meet the following requirements: the voltage gain is approximately continuously adjustable, and the adjustment step is as small as possible; in the frequency domain of the guided wave signal (15kHz-700kHz), except for the amplitude of the guided wave signal, it does not change other characteristics of the original signal, especially the phase; the circuit can be controlled in real time by a microcontroller. The commonly used voltage regulation circuit is realized by a feedback circuit composed of an integrated operational amplifier, and the gain control is realized by changing the resistance value of the feedback path, wherein the commonly used voltage regulation circuit includes analog switch and resistance network method, digital potentiometer method, VGA (Variable Gain Amplifier) method, etc. The circuit schematic diagram of the analog switch and resistance network method is shown in Figure 1 , however, it has the following disadvantages: narrow gain adjustment range, low gain adjustment resolution; affected by the on-resistance of the analog switch, the gain adjustment accuracy is not high; there is crosstalk between the analog switch channels, and the gain cannot be accurately adjusted. The circuit schematic diagram of the digital potentiometer method is shown in Figure 2 , however, it has the following disadvantages: the digital potentiometer tap has a parasitic resistance, and the temperature drift coefficient of the resistance is large, which affects the gain adjustment accuracy; there are a large number of parasitic capacitances in the digital potentiometer, including tap parasitic capacitance, termination ground capacitance, etc., which cause the digital potentiometer to exhibit different frequency characteristics when outputting different resistances to alternating current signals, and the bandwidth of the digital potentiometer is limited, which cannot be used for guided wave signal calibration. The circuit schematic diagram of the VGA method is shown in Figure 3 , however, it has the following disadvantages: the gain of the analog control VGA circuit is controlled by an external voltage, and a control voltage generating circuit needs to be designed for guided wave signal calibration, which is easily affected by external interference, resulting in low accuracy, and most of the VGAs on the market realize voltage amplification multiple control by the exponential law of control voltage, which complicates the entire calibration process; the digital control word of the digital control VGA can only reach 5-7 bits, resulting in a large gain adjustment step and low calibration accuracy for the guided wave signal; the voltage amplification multiple of the digital control VGA is in an exponential law with the digital control word, resulting in a complex calibration process; the lower cutoff frequency of the digital control VGA device is above 5MHz, which is higher than the frequency range of the guided wave signal (15kHz-700kHz). SUMMARY

[0006] To address the aforementioned issues, this invention provides a guided wave signal calibration system and method based on a four-quadrant multiplier. By adjusting the voltage gain of the guided wave signal, guided wave signal calibration is achieved, which is used to accurately identify structural damage in aircraft, improve the reliability of aircraft structural health monitoring, and ensure aircraft safety.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] A guided wave signal calibration method, comprising,

[0009] Step S1: Use the n-channel sensing signal of the first test piece as the standard signal and the n-channel sensing signal of the second test piece as the monitoring signal.

[0010] Step S2, import initial parameters, wherein the initial parameters include the waveguide voltage gain g0 and the initial voltage gain g1 of the waveguide calibration system;

[0011] Step S3 includes:

[0012] Step S31: Use the initial parameters to collect data on the first specimen to obtain guided wave data for n channels of the first specimen;

[0013] Step S32: Use the initial parameters to acquire data on the second specimen to obtain guided wave data for n channels of the second specimen;

[0014] Step S4, set the loop parameter i = 1;

[0015] Step S5: Read the peak voltage V of the i-th channel of the first test piece. 1i and the voltage gain g0 of the waveguide conditioner;

[0016] Step S6: Read the peak voltage V of the i-th channel of the second specimen. 2i ;

[0017] Step S7: Calculate the peak voltage V of the i-th channel of the second specimen. 2i The gain g required by the guided wave calibration system to meet the calibration requirements 2i The calculation formula is as follows:

[0018]

[0019] g 2i To calculate the gain;

[0020] Step S8: Locate the actual gain truth table and add the calculated gain g. 2i Corrected to actual gain g ci The voltage gain of the guided wave calibration system when acquiring the i-th channel of the second specimen is set to the actual gain g.ci ;

[0021] Step S9: Set the loop parameter i = i + 1, and repeat steps S5 to S8 until i = n to complete the voltage gain setting of the guided wave calibration system for all channels of the second specimen.

[0022] Step S10: Use the calibrated voltage gain of each channel as a new parameter to acquire data for the second specimen.

[0023] In one specific embodiment, the calculated gain g is... 2i With the actual gain g ci An approximation correction is performed, using the actual gain truth table that is closest to the calculated gain g. 2i The value of g is used as the actual gain g ci .

[0024] The present invention also provides a guided wave signal calibration system, comprising,

[0025] The host computer integrates the aforementioned guided wave signal calibration method;

[0026] A logic controller, the input of which is connected to the host computer;

[0027] An inverting proportional amplifier, the input of which is connected to the guided wave signal to be calibrated;

[0028] A four-quadrant multiplier, wherein the reference voltage terminal of the four-quadrant multiplier is connected to the output terminal of the inverting proportional amplifier, and the control terminal of the four-quadrant multiplier is connected to the output terminal of the logic controller;

[0029] A current feedback amplifier is provided, wherein the negative input terminal of the current feedback amplifier is connected to the first output terminal of the four-quadrant multiplier, the positive input terminal of the current feedback amplifier is connected to the second output terminal of the four-quadrant multiplier, the feedback terminal of the current feedback amplifier is connected to the feedback resistor terminal of the four-quadrant multiplier, and the output terminal of the current feedback amplifier outputs the calibrated guided wave signal.

[0030] The above-mentioned actual gain truth table is in the logic controller.

[0031] The aforementioned logic controller includes a communication module and a control module. The input terminal of the communication module is connected to the host computer, the output terminal of the communication module is connected to the input terminal of the control module, and the output terminal of the control module is connected to the control terminal of the four-quadrant multiplier.

[0032] The aforementioned communication module communicates with the host computer via serial port, network port, or peripheral bus protocol, and the control module communicates with the four-quadrant multiplier via three-wire SPI protocol.

[0033] The aforementioned inverting amplifier includes a first operational amplifier, a first resistor, and a second resistor. The negative input terminal of the first operational amplifier is connected to the guided wave signal to be calibrated through the first resistor. The negative input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier through the second resistor. The positive input terminal of the first operational amplifier is grounded. The output terminal of the first operational amplifier is connected to the reference voltage terminal of the four-quadrant multiplier.

[0034] The aforementioned four-quadrant multiplier includes a resistor network and a data control shift latch module. The input of the data control shift latch module is connected to the output of the logic controller, and the output of the data control shift latch module is connected to the resistor network.

[0035] In one specific embodiment, the above-mentioned four-quadrant multiplier is a current-mode multiplication DAC with an R-2R ladder resistor network structure.

[0036] The aforementioned current feedback amplifier includes a second operational amplifier, a first capacitor, and a third resistor. The first terminal of the first capacitor is connected to the first output terminal of the four-quadrant multiplier and the negative input terminal of the second operational amplifier. The second terminal of the first capacitor is connected to the output terminal of the operational amplifier. The first terminal of the third resistor is connected to the feedback resistor terminal of the four-quadrant multiplier. The second terminal of the third resistor is connected to the output terminal of the second operational amplifier. The positive input terminal of the second operational amplifier is connected to the second output terminal of the four-quadrant multiplier. The positive input terminal of the second operational amplifier is grounded.

[0037] Beneficial effects: The guided wave signal calibration system and method of this invention are simple in design and easy to integrate. For systems with microcontrollers, only a multiplier DAC, a dual-channel operational amplifier, a sliding rheostat, and a small number of resistors and capacitors are needed, greatly reducing the system size. It can calibrate AC and DC signals in a wide frequency range (0-700kHz) and a large range (0-±10V), with a calibration accuracy (i.e., voltage gain accuracy) of up to 1 / 211V / V. Selecting a multiplier DAC with a higher control bit width can further improve the calibration accuracy. It has a high signal-to-noise ratio and is less affected by temperature after temperature compensation. Except for the signal amplitude, it does not change other characteristics of the signal, including phase and signal frequency components. It is flexible in application. Utilizing the real-time controllability of the system and the controllable gain range (0-2V / V), the calibration system can be used for signal attenuation or enhancement under specific conditions.

[0038] To make the above-mentioned features and advantages of the invention more apparent and understandable, specific embodiments are described below, and detailed descriptions are provided in conjunction with the accompanying drawings. Attached Figure Description

[0039] Figure 1 This is a circuit diagram illustrating the analog switch and resistor network method.

[0040] Figure 2 This is a circuit diagram of the digital potentiometer method.

[0041] Figure 3 This is a circuit diagram for the VGA method.

[0042] Figure 4 This is a circuit diagram of a specific embodiment of a guided wave signal calibration system according to the present invention.

[0043] Figure 5 This is a flowchart of a guided wave signal calibration method according to the present invention. Detailed Implementation

[0044] To make the objectives and technical solutions of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0045] Figure 4 This is a circuit diagram of a specific embodiment of a guided wave signal calibration system according to the present invention. Figure 4 As shown, the guided wave signal calibration system of the present invention includes a host computer 41, a logic controller 42, an inverting proportional amplifier 43, a four-quadrant multiplier 44, and a current feedback amplifier 45. The host computer 41 is connected to the input terminal of the logic controller 42, the output terminal of the logic controller 42 is connected to the control terminal of the four-quadrant multiplier 44, and the input terminal of the inverting proportional amplifier 43 is connected to the guided wave signal U to be calibrated. in The guided wave signal to be calibrated is a guided wave signal conditioned by a guided wave signal conditioner. The output terminal of the inverting proportional amplifier 43 is connected to the reference voltage terminal of the four-quadrant multiplier 44. The first output terminal OUT1 of the four-quadrant multiplier 44 is connected to the inverting input terminal of the current feedback amplifier 45. The second output terminal OUT2 of the four-quadrant multiplier 44 is connected to the non-inverting input terminal of the current feedback amplifier 45. The feedback resistor terminal FB of the four-quadrant multiplier 44 is connected to the feedback terminal of the current feedback amplifier 45. The output terminal of the current feedback amplifier 45 outputs the calibrated guided wave signal U. out .

[0046] The logic controller 42 includes a communication module 421 and a control module 422. The input terminal of the communication module 421 is connected to the host computer 41, and the output terminal of the communication module 421 is connected to the input terminal of the control module 422. The output terminal of the control module 422 is connected to the control terminal of the four-quadrant multiplier 44. The communication module 421 implements the communication protocol and receives and decodes instructions from the host computer 41. The control module 422 receives the decoded instructions from the communication module 421 and transmits control commands D to the four-quadrant multiplier 44 in a manner that satisfies the timing requirements of the four-quadrant multiplier 44. In a specific embodiment, the logic controller 42 is implemented by a microcontroller and its peripheral circuits. The microcontroller can be a single-chip microcomputer, a field-programmable gate array, etc. The communication module 421 communicates with the host computer 41 through protocols such as serial port, network port, or peripheral bus. The control module 422 communicates with the four-quadrant multiplier 44 through the three-wire SPI protocol. Furthermore, in order to enable the normal writing of the control command D, the port level of the logic controller 42 should be compatible with the four-quadrant multiplier 44.

[0047] The inverting proportional amplifier 43 includes an operational amplifier A41, a resistor R41, and a resistor R42. The negative input terminal of the operational amplifier A41 is connected to the guided wave signal U to be calibrated via the resistor R41. in The negative input terminal of operational amplifier A41 is connected to its output terminal via resistor R42, the positive input terminal of operational amplifier A41 is grounded, and its output terminal is connected to the reference voltage terminal of the four-quadrant multiplier 44. The inverting proportional amplifier 43 can both isolate from the front-end waveguide conditioner (not shown in the figure) and adjust the phase of the guided wave signal, ultimately maintaining the calibration guided wave signal U. out Apart from the signal amplitude, other characteristics such as phase remain unchanged. In one specific embodiment, resistors R41 and R42 are high-resistance resistors.

[0048] The four-quadrant multiplier 44 includes a resistor network 441 and a data control shift latch module 442. The four-quadrant multiplier 44 is a current-type multiplication DAC with an R-2R trapezoidal resistor network structure. The resistor network 441 includes n switches, S41 to S4n. The resistance value of the resistors in the trapezoidal resistor network 441 is R or 2R. The input terminal of the resistor network 441 is the reference voltage terminal of the four-quadrant multiplier 44, and the first output terminal of the resistor network 441 is the first output terminal OUT1 of the four-quadrant multiplier 44. The second output terminal is the second output terminal OUT2 of the four-quadrant multiplier 44. The feedback resistor terminal FB of the resistor network 441 is the feedback resistor terminal FB of the four-quadrant multiplier 44. The input terminal of the data control shift latch module 442 is connected to the output terminal of the logic controller 42, and the output terminal of the data control shift latch module 442 is connected to the resistor network 441. The data control shift latch module 442 controls the on / off state of switches S41 to S4n. More specifically, the data control shift latch module 442 uses n-bit binary code d1 to dn. n Control d i The corresponding switches S on each branch 4i Where i = 1, 2, ..., n. The four-quadrant multiplier 44 performs multiplication operations on the digital control word output by the logic controller 42 to ultimately achieve guided wave signal amplitude calibration. The reference voltage input of the four-quadrant multiplier 44 has a high control bit width and supports a wide range of AC modes. The feedback resistor R in the resistor network 441... FB The resistance value is R.

[0049] The current feedback amplifier 45 includes an operational amplifier A42, a capacitor C41, and a resistor R43. The first terminal of capacitor C41 is connected to the first output terminal OUT1 of the four-quadrant multiplier 44, and the second terminal of capacitor C41 is connected to the output terminal of operational amplifier A42. The first output terminal OUT1 is connected to the negative input terminal of operational amplifier A42, and the positive input terminal of operational amplifier A42 is connected to the second output terminal OUT2 of the four-quadrant multiplier 44. The second output terminal OUT2 is grounded. The first terminal of resistor R43 is connected to the feedback resistor terminal FB, and the second terminal of resistor R43 is connected to the output terminal of operational amplifier A42. The output terminal of operational amplifier A42 outputs a calibration guided wave signal U. outIn this configuration, resistor R43 is a variable resistor, and capacitor C41 is used for phase compensation. The current feedback amplifier 45 converts the current-form guided wave signal, after multiplication, back into a voltage signal before outputting it, thus achieving voltage gain adjustment together with the four-quadrant multiplier 44. In a specific embodiment, considering the frequency domain (50kHz~700kHz) of the guided wave signal and interference from crosstalk signals, the operational amplifier A42 in the current feedback amplifier 45 should be a low-bias, high-gain-bandwidth product, high-speed, high-voltage operational amplifier.

[0050] The following will continue to combine Figure 4 This invention introduces the working principle of a guided wave signal calibration system. Considering that the input resistance of the inverting proportional amplifier 43 is equivalent to R41, and that the preamplifier of this guided wave signal calibration system needs to be used in conjunction with a guided wave signal conditioner, in this specific embodiment, R41 = R42, and the guided wave signal U to be calibrated... in The voltage at node 401 after passing through the inverting amplifier 43 is:

[0051]

[0052] The voltage U 401 The reference voltage for the four-quadrant multiplier 44 is I, and the current is I. in Input current, output current I o To pass through switch S 4i In this specific embodiment, the sum of the output currents of the selected branches is such that when the digital signal d... i When d = 1, the branch is connected to the inverting input terminal of the operational amplifier A42, d i When the input resistance is 0, the branch is connected to the non-inverting input terminal of the operational amplifier A42. Based on the series and parallel relationships of the resistors in the resistor network 441, the input resistance at node 401 can be obtained as R. in =R, input current I in With the voltage U 401 Satisfying relation I in =U 401 / R in Furthermore, based on the current-shunting effect of the resistor, the output current I... o The expression is as follows:

[0053]

[0054] Therefore, it can be seen that through d i =1 or d i =0 can control the output current I o The magnitude of the current. Based on the "virtual short" and "virtual open" characteristics of the operational amplifier, the potential at node 402 is 0, and the feedback loop current I... FB≈I o The output voltage U out The following relationship must be satisfied:

[0055]

[0056] In this specific embodiment, the four-quadrant multiplier 44 is an AD5452 chip from Analog Devices (ADI). The AD5452 chip has a 12-bit control width and an input resistance R. in and feedback resistor R FB Both are 9kΩ±2kΩ, input resistance R in and feedback resistor R FB The temperature drift is ±50ppm / ℃. As a calibration system, the circuit should be able to amplify or attenuate the voltage, and the calibration system mainly plays a fine-tuning and compensation role; therefore, the system's voltage gain can be set to 0~2V / V. For a typical four-quadrant multiplier, R... FB =R=R in Considering input resistance tolerance and temperature drift, Figure 4 The temperature drift coefficient of the variable resistor R43 mentioned above is the same as that of the input resistance R. in and feedback resistor R FB Furthermore, before using the calibration system, the resistance value of the variable resistor R43 should be adjusted so that the maximum gain of the calibration system is 2V / V. Considering the input resistance R... in Temperature drift coefficient T Rin Feedback resistor R FB Temperature drift coefficient T RFB The temperature drift coefficient T of the variable resistor R43 R43 Under the condition that the output voltage U is within the temperature variation range of Δt℃, out for:

[0057]

[0058] After the above analysis of the input resistor R in the resistor network 441 in The feedback resistor R FB The compensation for the temperature drift coefficient of the variable resistor R43, and the output voltage U out The expression is:

[0059]

[0060] Where D is the control command, D∈[0,2] n-1 ], where n is the control bit width of the four-quadrant multiplier 44. In this specific embodiment, n = 12, the adjustment range of the calibration system gain is 0 to 2V / V, and the adjustment accuracy is 1 / 2 11 =0.000488V / V.

[0061] In summary, the guided wave signal U to be calibrated in After entering the guided wave signal calibration system, the signal passes through an inverting proportional amplifier 43, a four-quadrant multiplier 44, and a current feedback amplifier 45 in sequence before outputting the calibrated guided wave signal U. out .

[0062] This invention also provides a method for calibrating guided wave signals. Figure 5 This is a flowchart of a guided wave signal calibration method according to the present invention, specifically including:

[0063] Step S1: Set the standard signal and the monitoring signal. Specifically, the n-channel sensing signal of the first test piece is used as the standard signal, and the n-channel sensing signal of the second test piece is used as the monitoring signal. The first test piece is the test piece before being affected by time-varying factors, structural changes, sensor differences, etc., and the second test piece is the test piece after being affected by the above factors.

[0064] Step S2, import initial parameters, wherein the initial parameters include waveguide voltage gain g0 and waveguide calibration system voltage gain g1, wherein, in a specific embodiment, g1 is 1V / V.

[0065] Step S3 includes:

[0066] Step S31: The guided wave acquisition system uses the initial parameters to acquire data from the first specimen, and obtains guided wave data for n channels of the first specimen.

[0067] Step S32: The guided wave acquisition system uses the initial parameters to acquire data from the second specimen, and obtains guided wave data for n channels of the second specimen.

[0068] Step S4: Set the loop parameter i = 1.

[0069] Step S5: Read the peak voltage V of the i-th channel of the first test piece. 1i and the voltage gain g0 of the waveguide conditioner.

[0070] Step S6: Read the peak voltage V of the i-th channel of the second test piece. 2i .

[0071] Step S7: Calculate the peak voltage V of the i-th channel of the second specimen. 2i The calibration system needs to provide a gain g to meet the calibration requirements. 2i The calculation formula is as follows:

[0072]

[0073] g 2i To calculate the gain.

[0074] Step S8: Locate the actual gain truth table and correct the actual calibration system gain g. ci Because it is difficult to achieve an ideal gain-adjustable calibration system in practice, the calculated gain g needs to be... 2i The actual gain g that the calibration system can actually provide ci To perform approximate corrections, the actual gain truth table that the calibration system can provide needs to be determined in advance in the logic controller 42 and loaded into the logic controller 42 in advance. In step S8, by searching the actual gain truth table, the value closest to the calculated gain g in the actual gain truth table is selected. 2i The value of g is used as the actual gain. ci The gain of the guided wave calibration system when acquiring the i-th channel of the second specimen is set to the actual gain g. ci .

[0075] Step S9: Set the loop parameter i = i + 1, and repeat steps S5 to S8 until i = n to complete the voltage gain setting of the guided wave calibration system for all channels of the second specimen.

[0076] Step S10: Use the calibrated voltage gain of each channel as a new parameter to acquire data for the second test piece.

[0077] For details of the guided wave acquisition system, please refer to the patent entitled "Multi-channel Integrated Piezoelectric Scanning Structure Health Monitoring System" (authorization announcement number CN100441153C).

[0078] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method of calibrating a guided wave signal, the method comprising: Comprising, Step S1, taking the n-channel sensing signal of the first test piece as a standard signal and taking the n-channel sensing signal of the second test piece as a monitoring signal, wherein the first test piece is a test piece before being affected by time-varying factors, structural changes and sensor difference factors, and the second test piece is a test piece after being affected by time-varying factors, structural changes and sensor difference factors, Step S2, importing initial parameters, wherein the initial parameters include a guided wave conditioner voltage gain g0 and an initial voltage gain g1 of a guided wave calibration system; Step S3 includes: Step S31, using the initial parameters to collect data of the first test piece to obtain guided wave data of n channels of the first test piece; Step S32, using the initial parameters to collect data of the second test piece to obtain guided wave data of n channels of the second test piece; Step S4, setting a loop parameter i = 1; Step S5, reading the peak voltage V of the i-th channel of the first test piece 1i and the waveguide conditioner voltage gain g0; Step S6, reading the peak voltage V of the i-th channel of the second test piece 2i ; Step S7, calculating the peak voltage V of the i-th channel of the second test piece 2i Gain g provided by the guided wave calibration system when the calibration requirement is met 2i The calculation formula is as follows g 2i to calculate the gain; Step S8, searching for the actual gain true value table, calculating the gain g 2i correcting the actual gain g ci , setting the voltage gain of the guided wave calibration system when collecting the i-th channel of the second test piece as the actual gain g ci ; Step S9, setting the loop parameter i = i + 1, repeating the step S5 to the step S8 until i = n, and completing the voltage gain setting of the guided wave calibration system of all channels of the second test piece; Step S10, using the calibrated voltage gain of each channel as a new parameter to collect data of the second test piece, wherein the calibrated guided wave signal U out is expressed as follows: Wherein, U 401 is a reference voltage of the four-quadrant multiplier, R in is an input resistance, d i is a digital signal, U in is a to-be-calibrated guided wave signal, R FB is a feedback resistance, R43' is a variable resistance, D is a control command, D ∈ [0, 2 n-1 ], and n is a control bit width of the four-quadrant multiplier.

2. The method of claim 1, wherein, approximate the actual gain g 2i approximate the actual gain g ci approximate the actual gain g 2i approximate the actual gain g ci .

3. A guided wave signal calibration system, comprising: Comprising: A host computer, wherein the host computer integrates a guided wave signal calibration method according to any one of claims 1-2, and provides a gain adjustment signal; A logic controller, wherein an input end of the logic controller is connected to the host computer; A reverse proportional amplifier, wherein an input end of the reverse proportional amplifier is connected to a guided wave signal to be calibrated; A four-quadrant multiplier, wherein a reference voltage end of the four-quadrant multiplier is connected to an output end of the reverse proportional amplifier, and a control end of the four-quadrant multiplier is connected to an output end of the logic controller; the four-quadrant multiplier is a current-mode multiplication DAC with an R-2R ladder resistor network structure, and the four-quadrant multiplier includes a resistor network and a data control shift latch module; an input end of the data control shift latch module is connected to the output end of the logic controller, and an output end of the data control shift latch module is connected to the resistor network; A current feedback amplifier, wherein a negative input end of the current feedback amplifier is connected to a first output end of the four-quadrant multiplier, a positive input end of the current feedback amplifier is connected to a second output end of the four-quadrant multiplier, a feedback end of the current feedback amplifier is connected to a feedback resistor end of the four-quadrant multiplier, and an output end of the current feedback amplifier outputs a calibrated guided wave signal; The current feedback amplifier includes a second operational amplifier, a first capacitor and a third resistor; a first end of the first capacitor is connected to the first output end of the four-quadrant multiplier and a negative input end of the second operational amplifier; a second end of the first capacitor is connected to an output end of the second operational amplifier; a first end of the third resistor is connected to the feedback resistor end of the four-quadrant multiplier; a second end of the third resistor is connected to an output end of the second operational amplifier; a positive input end of the second operational amplifier is connected to the second output end of the four-quadrant multiplier; the positive input end of the second operational amplifier is grounded; and the output end of the four-quadrant multiplier is connected to a data acquisition card through the current feedback amplifier, so as to suppress phase distortion.

4. The guided-wave signal calibration system of claim 3, wherein, The actual gain truth table is in the logic controller.

5. The guided-wave signal calibration system of claim 4, wherein, The logic controller comprises a communication module and a control module, an input end of the communication module is connected with the host computer, an output end of the communication module is connected with an input end of the control module, and an output end of the control module is connected with a control end of the four-quadrant multiplier.

6. The guided-wave signal calibration system of claim 5, wherein, The communication module and the host computer communicate through a serial port, a network port or a peripheral bus protocol, and the control module and the four-quadrant multiplier communicate through a three-wire SPI protocol.

7. The guided-wave signal calibration system of claim 3, wherein, The reverse proportional amplifier comprises a first operational amplifier, a first resistor and a second resistor, a negative input end of the first operational amplifier is connected with the to-be-calibrated guided wave signal through the first resistor, a negative input end of the first operational amplifier is connected with an output end of the first operational amplifier through the second resistor, a positive input end of the first operational amplifier is grounded, and the output end of the first operational amplifier is connected with a reference voltage end of the four-quadrant multiplier.

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