Ultrasonic thickness measurement system and ultrasonic thickness measurement method

Abstract

This application provides an ultrasonic thickness measurement system and method. The ultrasonic thickness measurement system includes: a signal generation unit configured to generate a discrete frequency modulated time-domain ultrasonic excitation signal; an ultrasonic transceiver unit configured to convert the time-domain ultrasonic excitation signal into ultrasonic waves and transmit them to the object under test, receive echo ultrasonic waves reflected from inside the object under test, and convert the echo ultrasonic waves into echo electrical signals; an analog mixing unit configured to perform analog mixing of the echo electrical signals and the time-domain ultrasonic excitation signal (which serves as a local oscillator signal) to obtain a mixed signal; an analog filtering unit configured to filter the mixed signal to obtain a low-frequency beat frequency signal; an analog-to-digital conversion unit configured to sample the low-frequency beat frequency signal and convert it into a digital difference frequency signal; and a signal processing unit configured to perform frequency domain analysis on the digital difference frequency signal and calculate the target thickness of the object under test based on the analysis results.

Description

Technical Field

[0001] This application relates to the field of nondestructive testing technology, and more specifically, to an ultrasonic thickness measurement system and ultrasonic thickness measurement method. Background Technology

[0002] Ultrasonic thickness measurement is a commonly used non-destructive testing technique in various fields, including industry and medicine. For example, in industry, it is often used to measure the wall thickness of metallic or non-metallic components such as pipes, containers, and plates to assess their structural integrity and safety; in medicine, it can be used to measure the thickness of human tissues.

[0003] Traditional ultrasonic thickness measurement techniques mostly employ the pulse-echo method, which calculates thickness by directly measuring the propagation time of ultrasonic waves within the object being measured. Traditional ultrasonic thickness measurement systems often require direct analog-to-digital conversion (ADC) of the high-frequency echo signals. Due to the extremely narrow time-domain width of ultrasonic pulses, the sampling rate and bandwidth requirements of the ADC unit are extremely high. Typically, a high sampling rate ADC unit of 50MHz or higher is needed to capture the echo leading edge and details. This results in high hardware costs, large amounts of raw data, and a complex and extremely time-consuming signal processing process. Summary of the Invention

[0004] This application provides an ultrasonic thickness measurement system and method, which can significantly reduce hardware costs, simplify the signal processing in the ultrasonic thickness measurement process, and improve detection efficiency and portability.

[0005] In a first aspect, an ultrasonic thickness measurement system is provided, comprising: The signal generating unit is configured to generate a discrete frequency modulated time-domain ultrasonic excitation signal; The ultrasonic transceiver unit, connected to the signal generating unit, is configured to: convert the time-domain ultrasonic excitation signal into ultrasonic waves and transmit them to the object under test; receive the echo ultrasonic waves reflected from inside the object under test; and convert the echo ultrasonic waves into echo electrical signals. The analog mixing unit, connected to the signal generating unit and the ultrasonic transceiver unit respectively, is configured to: perform analog mixing of the echo electrical signal and the time-domain ultrasonic excitation signal, which is the local oscillator signal, to obtain the mixed signal; The analog filtering unit, connected to the analog mixing unit, is configured to filter the mixing signal to remove high-frequency components and obtain a low-frequency beat signal containing the thickness information of the object being measured. The analog-to-digital conversion unit, connected to the analog filtering unit, is configured to sample the low-frequency beat frequency signal and convert it into a digital difference frequency signal. The signal processing unit, connected to the analog-to-digital conversion unit, is configured to perform frequency domain analysis on the digital difference frequency signal and calculate the target thickness of the object under test based on the analysis results.

[0006] In one embodiment, the ultrasonic thickness measurement system further includes a control unit connected to the signal generating unit; The control unit is configured to send a configuration command to the signal generation unit to configure the discrete frequency modulation parameters of the time-domain ultrasonic excitation signal, wherein the discrete frequency modulation parameters include the frequency step value and the dwell time at each frequency point; The signal generation unit generates a discrete-frequency modulated time-domain ultrasonic excitation signal, which is configured as follows: In response to configuration commands, a time-domain ultrasonic excitation signal is generated, in which the frequency exhibits discrete step changes on the time axis according to the frequency step value and the dwell time.

[0007] In one implementation, the analog-to-digital conversion unit samples the low-frequency beat frequency signal and is configured to: The low-frequency beat frequency signal is sampled at a preset sampling frequency, which is significantly lower than the center frequency of the time-domain ultrasonic excitation signal.

[0008] In one implementation, the signal processing unit performs frequency domain analysis on the digital difference frequency signal and is configured to: A window function is applied to the digital difference frequency signal for weighting to suppress spectral leakage, resulting in a weighted digital signal sequence. Using the Fast Fourier Transform algorithm, the weighted digital signal sequence is converted from a time domain signal to a frequency domain signal to obtain the frequency domain amplitude spectrum; The target thickness of the object under test is calculated based on the frequency domain amplitude spectrum.

[0009] In one implementation, the signal processing unit uses a Fast Fourier Transform algorithm to convert the weighted digital signal sequence from a time-domain signal to a frequency-domain signal, obtaining a frequency-domain amplitude spectrum, which is configured as follows: The weighted digital difference frequency signal sequence is zero-padded in the time domain to obtain the zero-padded digital difference frequency signal sequence. Perform a Fast Fourier Transform on the zero-padded digital difference frequency signal sequence to obtain the frequency domain amplitude spectrum.

[0010] In one embodiment, the ultrasonic thickness measurement system further includes a first signal amplifier and / or a second signal amplifier; The first signal amplifier is connected to both the signal generating unit and the ultrasonic transceiver unit, and is configured as follows: The time-domain ultrasonic excitation signal is amplified, and the amplified time-domain ultrasonic excitation signal is sent to the ultrasonic transceiver unit. The second signal amplifier is connected to both the analog filtering unit and the analog-to-digital converter unit, and is configured as follows: The low-frequency beat signal is amplified and then sent to the analog-to-digital conversion unit.

[0011] In one implementation, the analog filtering unit filters the mixing signal and is configured as follows: High-frequency components and DC leakage signals in the mixed signal are filtered out to obtain a low-frequency beat signal that contains only the thickness information of the object being measured.

[0012] In one implementation, the signal processing unit performs frequency domain analysis on the digital difference frequency signal and is configured to: The digital difference frequency signal is converted from a time domain signal to a frequency domain signal using the Fast Fourier Transform algorithm to obtain the frequency domain amplitude spectrum; Search for the maximum amplitude value in the frequency domain amplitude spectrum, and determine the frequency point corresponding to the maximum amplitude value as the measurement beat frequency; The target thickness of the object under test is calculated based on the measured beat frequency, the frequency modulation slope of the time-domain ultrasonic excitation signal, and the propagation speed of the ultrasonic wave in the object under test.

[0013] In one implementation, the signal processing unit calculates the target thickness of the object being measured, and is configured to: The target thickness of the object being measured is calculated using the following formula:

[0014] in, d Indicates thickness, c This indicates the speed of sound in which ultrasound waves propagate through the object being measured. f b Indicates the measured beat frequency. μ Indicates the frequency modulation slope. This indicates the pre-calibrated inherent system delay time.

[0015] Secondly, an ultrasonic thickness measurement method is provided, applied to the ultrasonic thickness measurement system of any embodiment of this application, the method comprising: The signal generation unit generates a discrete frequency modulated time-domain ultrasonic excitation signal; The ultrasonic transceiver unit converts the time-domain ultrasonic excitation signal into ultrasonic waves and transmits them to the object under test. It also receives the echo ultrasonic waves reflected from inside the object under test and converts the echo ultrasonic waves into echo electrical signals. The analog mixing unit performs analog mixing of the echo electrical signal and the time-domain ultrasonic excitation signal, which is the local oscillator signal, to obtain the mixed signal; The analog filtering unit filters the mixed signal to remove high-frequency components and obtains a low-frequency beat signal containing the thickness information of the object being measured. The analog-to-digital converter samplees the low-frequency beat frequency signal and converts it into a digital difference frequency signal; The signal processing unit performs frequency domain analysis on the digital difference frequency signal and calculates the target thickness of the object under test based on the analysis results.

[0016] The ultrasonic thickness measurement system provided in the first aspect of this application effectively converts high-frequency ultrasonic echo signals into low-frequency beat signals by employing discrete-frequency modulated time-domain ultrasonic excitation signals and combining them with analog-to-digital down-conversion mixing technology. Compared to traditional ultrasonic thickness measurement (pulse-echo method), which directly relies on time-of-flight measurement and requires extremely high-sampling-rate analog-to-digital converters to capture narrow pulse echoes, the technical solution of this application effectively overcomes the dependence on high-sampling-rate analog-to-digital converters in traditional methods by effectively extracting low-frequency beat signals carrying thickness information. Instead, it samples the low-frequency beat signals, significantly reducing the sampling rate requirement of the analog-to-digital converter unit. This allows for the selection of lower-cost, lower-power, medium-to-low-sampling-rate analog-to-digital converters, significantly reducing system hardware costs. The reduced sampling rate also significantly reduces the amount of data generated, thereby reducing the complexity of data processing and computational resource requirements. Furthermore, since the signal generation unit only needs to generate discrete-frequency modulated time-domain ultrasonic excitation signals, control is simple and continuous linear calibration is not required, further reducing the implementation complexity and cost of the signal generation unit. Therefore, the ultrasonic thickness measurement method of this application embodiment significantly reduces the hardware cost of the system, improves the system response speed and measurement efficiency, and can realize the miniaturization and portability of the system while maintaining high thickness measurement accuracy.

[0017] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0018] Figure 1 A schematic diagram of the structure of an ultrasonic thickness measurement system provided in one embodiment of this application is shown; Figure 2 A flowchart illustrating an embodiment of the ultrasonic thickness measurement method provided in this application is shown. Figure 3 A schematic diagram of the structure of an ultrasonic thickness measurement system provided in another embodiment of this application is shown; Figure 4 A schematic diagram illustrating the implementation principle of an ultrasonic thickness measurement method provided in another embodiment of this application is shown; Figure 5 A partial flowchart of an ultrasonic thickness measurement method provided in another embodiment of this application is shown. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. In the description of the embodiments of this application, unless otherwise stated, " / " means "or," for example, A / B can mean A or B; "and / or" in this text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, in the description of the embodiments of this application, "multiple" refers to two or more than two.

[0020] Hereinafter, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature.

[0021] Specific details, such as particular system architectures and techniques, are set forth for illustrative purposes and not for limitation, to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted to avoid unnecessary detail that could obscure the description of this application.

[0022] As mentioned earlier, traditional ultrasonic thickness measurement methods typically require high sampling rate analog-to-digital converters (ADCs) of 50MHz or higher to capture the echo leading edge and details when processing echo signals. This results in high hardware costs, large amounts of raw data, and complex and extremely time-consuming signal processing.

[0023] Furthermore, traditional ultrasonic thickness measurement techniques result in high system complexity and limited hardware selection, thus affecting the overall system's deployability and operational efficiency. For example, in industrial pipeline wall thickness inspection applications, the on-site environment places stringent requirements on the portability and power consumption characteristics of the thickness measurement equipment. However, due to the necessity of high-sampling-rate analog-to-digital converters, existing equipment is bulky and consumes a lot of power, making it difficult to adapt to rapid inspection operations in confined spaces. In particular, the excessive data processing volume causes significant delays in the measurement process, limiting real-time monitoring capabilities and further impacting the continuity of the inspection process and the efficiency of operators.

[0024] To at least partially solve the above-mentioned technical problems, embodiments of this application provide an ultrasonic thickness measurement system and an ultrasonic thickness measurement method. By using a discrete frequency modulated excitation signal combined with analog mixing technology, the high-frequency echo signal is converted into a low-frequency beat frequency signal for sampling and analysis. This scheme can effectively overcome the dependence on high sampling rate analog-to-digital converters in traditional ultrasonic thickness measurement methods, and has the advantages of significantly reducing hardware costs, simplifying the signal processing process, improving detection efficiency and portability.

[0025] First, this application provides an ultrasonic thickness measurement method. This ultrasonic thickness measurement method is applicable to non-destructive testing scenarios in various fields, including but not limited to: industrial inspection, medical, aerospace, and automotive manufacturing. For example, in industrial pipeline inspection, it can rapidly measure the thickness of metal pipelines that may corrode and thin after long-term use, or perform periodic monitoring to promptly identify potential safety hazards; in aero-engine blade inspection, it can accurately measure the thickness of different parts of the blade to ensure it meets design requirements; in the medical field, ultrasound can be used to rapidly detect the thickness of human skin, muscles, and other tissues, providing data support for clinical diagnosis. Furthermore, the ultrasonic thickness measurement method of this application can also be used to measure the wall thickness of industrial containers, sheet metal, and other metal or non-metal components to assess their structural integrity and safety; it can also be used in automotive manufacturing to measure the thickness of body panels, engine parts, etc., to improve vehicle quality and performance; and it can also be used for thickness measurement of various materials and components in shipbuilding, petrochemical, and construction industries. The ultrasonic thickness measurement method of this application can quickly, accurately and cost-effectively obtain the thickness information of the object being measured without damaging it, providing reliable data support for quality control, safety assessment and fault diagnosis in related fields.

[0026] First, it should be noted that the target thickness measured by ultrasonic thickness measurement in the embodiments of this application can include various dimensional quantities that are expected to be measured and characterize the geometric features of the object under test along the ultrasonic wave propagation path. These include, but are not limited to: the measurement of the overall wall thickness of the object under test, and the measurement of the burial depth (i.e., the vertical distance from the surface of the object under test to the defect interface) of discontinuous defects (such as cracks, pores, corrosion pits, etc.) inside the object under test.

[0027] The implementation of the ultrasonic thickness measurement method of this application will be described in detail below with reference to specific embodiments.

[0028] like Figure 1As shown, the ultrasonic thickness measurement system 100 of this application embodiment includes, in sequence along the signal flow propagation direction: a signal generation unit 110, an ultrasonic transceiver unit 120, an analog mixer unit 130, an analog filter unit 140, an analog-to-digital converter unit 150, and a signal processing unit 160. The signal generation unit 110 is connected to both the ultrasonic transceiver unit 120 and the analog mixer unit 130. The remaining units are connected sequentially via the signal flow, forming a complete ultrasonic thickness measurement signal propagation link from excitation signal generation, ultrasonic transmission and reception, signal mixing and filtering, analog-to-digital conversion to digital signal processing.

[0029] like Figure 2 As shown, the ultrasonic thickness measurement method of this application embodiment includes the following steps S210, S220, S230, S240, S250 and S260.

[0030] In step S210, the signal generation unit generates a time-domain ultrasonic excitation signal with discrete frequency modulation.

[0031] In this embodiment, discrete frequency modulation refers to a signal whose frequency does not change continuously over time, but rather exhibits discrete variations. For example, the signal jumps from one frequency value to the next according to a preset interval (frequency step value) and time (dwell time). The time-domain ultrasonic excitation signal can be an electrical signal whose voltage changes over time, generated by a signal generation unit, and can be used to drive an ultrasonic probe to generate ultrasonic waves. The discrete frequency modulated time-domain ultrasonic excitation signal can be an ultrasonic excitation signal whose frequency exhibits discrete step changes on the time axis. For example, the frequency of this signal remains constant at a preset frequency step value within different time periods, forming a series of discrete frequency points. It can be understood that this modulation method allows the echo signal of the ultrasonic wave to generate a measurable frequency difference between the echo signal and the original excitation signal when the ultrasonic wave propagates in the object being measured, thereby carrying the thickness information of the object being measured.

[0032] In this embodiment, the signal generation unit can be any circuit module or chip capable of emitting a time-domain ultrasonic excitation signal with discrete frequency modulation. Optionally, the signal generation unit can be implemented using a Direct Digital Synthesis (DDS) chip. Specifically, the DDS can output an electrical signal with a specific discrete frequency in different time periods according to a preset frequency step value and dwell time. For example, the DDS can be set to increase the frequency by a fixed step size every microsecond, thereby forming a stepped frequency modulation waveform. Alternatively, the signal generation unit can be implemented using a voltage-controlled oscillator (VCO) or a microcontroller unit (MCU) in conjunction with a digital-to-analog converter. Alternatively, the signal generation unit can also be implemented using an Arbitrary Waveform Generator (AWG), which can store the discrete frequency modulation waveform data in a memory in advance and have the AWG read and output it according to a timing sequence.

[0033] It is understandable that the frequency range of the time-domain ultrasonic excitation signal generated by the signal generation unit is typically determined by the inherent center frequency of the ultrasonic transceiver unit (such as piezoelectric ceramic). A suitable ultrasonic transceiver unit can be selected based on the material properties of the object being measured (such as sound velocity and attenuation coefficient) and the desired measurement accuracy and depth. For example, for thickness measurement of metallic materials, an ultrasonic transceiver unit with a center frequency between 1 MHz and 10 MHz can be selected. The specific number of frequency points, frequency step values ​​(e.g., 10 kHz, 50 kHz, or 100 kHz), and dwell time at each frequency point (e.g., 10 microseconds, 50 microseconds, or 100 microseconds) can be flexibly configured through the control unit mentioned later to adapt to different detection needs.

[0034] In step S220, the ultrasonic transceiver unit converts the time-domain ultrasonic excitation signal into ultrasonic waves and transmits them to the object under test. It also receives the echo ultrasonic waves reflected from inside the object under test and converts the echo ultrasonic waves into echo electrical signals.

[0035] In this embodiment, the ultrasonic transceiver unit can be a device for converting electrical signals into ultrasonic waves and transmitting them to the object under test, while simultaneously receiving the echo ultrasonic waves reflected from the object under test and converting them into electrical signals.

[0036] In this embodiment, the ultrasonic transceiver unit can be implemented using various suitable devices, as long as they can achieve the mutual conversion between electrical energy and acoustic energy. Optionally, the ultrasonic transceiver unit can use a piezoelectric ceramic transceiver or an electromagnetic ultrasonic probe to achieve electroacoustic conversion. For example, a piezoelectric ceramic transceiver can generate mechanical vibration and emit ultrasonic waves when it receives a time-domain excitation signal, and can generate an electrical signal when it receives ultrasonic waves. Alternatively, the ultrasonic transceiver unit can also use separate transmitting and receiving transceivers to achieve electroacoustic conversion, wherein the transmitting transceiver can convert electrical signals into ultrasonic waves for transmission, while the receiving transceiver can receive echo ultrasonic waves and convert them back into electrical signals.

[0037] In step S230, the analog mixing unit performs analog mixing of the echo electrical signal and the time-domain ultrasonic excitation signal, which serves as the local oscillator signal, to obtain a mixed signal.

[0038] In this embodiment, the analog mixing unit can be a circuit module used to perform analog mixing of the received echo electrical signal and the original time-domain ultrasonic excitation signal, which serves as the local oscillator signal. It can be understood that through the mixing operation, two signals of different frequencies are multiplied to generate a new signal containing the sum and difference of the frequencies of the original signals (i.e., the local oscillator signal and the echo electrical signal acquired by the analog mixing unit at the same time). The analog mixing unit in this embodiment can down-convert the high-frequency echo signal to a lower frequency range to facilitate subsequent signal processing and quickly calculate the target thickness of the measured object.

[0039] It can be understood that the signal generating unit emits discrete frequency signals over a period of time, and the ultrasonic transceiver unit continuously receives echo signals. Therefore, at the same moment, the analog mixer unit can acquire the local oscillator signal currently output by the signal generating unit (i.e., the time-domain ultrasonic excitation signal at a certain discrete frequency point) and the echo electrical signal currently received by the ultrasonic transceiver unit. Since ultrasonic waves require a certain amount of time to propagate in the object under test, the excitation signal corresponding to the echo electrical signal is actually a signal at a certain discrete frequency point emitted by the signal generating unit at an earlier time. Therefore, there is a time difference between the local oscillator signal and the echo electrical signal, which corresponds to the round-trip propagation time of the ultrasonic wave in the object under test. Since the excitation signal is discretely frequency modulated, the excitation signal emitted at different times has different frequencies. Therefore, there is a frequency difference between the frequency of the local oscillator signal and the frequency of the echo electrical signal. This frequency difference corresponds to the measurement beat frequency mentioned later. Since the propagation time of ultrasonic waves in the object under test is related to the thickness of the object under test, and the propagation time will cause a corresponding frequency shift between the echo signal and the current local oscillator signal, the beat frequency signal carries the thickness information of the object under test. By using an analog mixing unit, the high-frequency echo signal and the local oscillator signal can be directly mixed in the analog domain to obtain a mixed signal containing the frequency and the frequency difference, where the frequency difference component is the low-frequency beat frequency signal. This eliminates the need for complex digital signal processing to convert high-frequency signals to low-frequency signals, significantly reducing the difficulty of subsequent signal processing and hardware resource requirements. It overcomes the reliance on high-sampling-rate analog-to-digital conversion of high-frequency echo signals in traditional solutions.

[0040] In this embodiment, the analog mixing unit can multiply the echo signal from the ultrasonic transceiver unit with the original excitation signal from the signal generation unit using an analog multiplier. Specifically, it can be implemented using an active multiplier, a passive mixer, or a differential operation circuit. For example, the analog mixing unit can use a Gilbert unit mixer to achieve high linearity analog mixing. Alternatively, the analog mixing unit can also use a diode-based passive mixer to achieve nonlinear analog mixing.

[0041] In step S240, the analog filtering unit filters the mixed signal to remove high-frequency components and obtain a low-frequency beat signal containing the thickness information of the object being measured.

[0042] In this embodiment, the low-frequency beat signal can refer to a low-frequency signal obtained after analog mixing, down-conversion, and low-pass filtering. The frequency of the low-frequency beat signal can be the frequency difference between the echo signal and the local oscillator signal. As mentioned earlier, the frequency of the low-frequency beat signal is directly related to the propagation time of the ultrasonic wave in the object under test (i.e., thickness information). Therefore, by analyzing the frequency of this low-frequency beat signal, the thickness of the object under test can be indirectly obtained.

[0043] In this embodiment, the analog filtering unit can at least have a low-pass filtering function to remove high-frequency noise. For example, the analog filtering unit may include a low-pass filter whose cutoff frequency can be set according to the frequency range of the low-frequency beat signal to be retained, so as to effectively filter out the high-frequency sum frequency component and other high-frequency noise interference in the mixing signal, and retain only the difference frequency component containing thickness information, i.e., the low-frequency beat signal. The low-pass filter can be implemented in various circuit forms, such as an RC passive low-pass filter, an LC passive low-pass filter, or an active low-pass filter composed of operational amplifiers. In a specific example, the low-pass filter can be implemented by a multi-order Butterworth filter or a Chebyshev filter.

[0044] In some examples, the analog filtering unit can also have a high-pass filtering function. Optionally, the analog filtering unit can be implemented using a band-pass filter. This band-pass filter has a preset lower cutoff frequency and a preset upper cutoff frequency. Its lower cutoff frequency can be set to a value higher than the frequency of the DC leakage signal generated after mixing (e.g., 0 Hz) to effectively filter out the DC component and near-DC extremely low-frequency leakage signals. Its upper cutoff frequency can be set significantly lower than the frequency of the high-frequency and low-frequency components generated by mixing, but higher than the highest possible frequency of the beat frequency signal, thereby filtering out high-frequency and low-frequency components and out-of-band noise. In this scheme, the band-pass filter can simultaneously filter out the high-frequency unwanted components and low-frequency DC leakage components in the mixed signal, allowing only the mid-to-low frequency beat frequency signal containing thickness information to pass through, achieving effective separation of useful signals and interference signals in the frequency domain, and providing a clean beat frequency signal without DC offset for subsequent signal amplifiers. Alternatively, the analog filtering unit can also be implemented using cascaded analog low-pass and high-pass filters. The analog low-pass filter first processes the mixing signal. Its cutoff frequency can be higher than the highest possible frequency of the beat frequency signal to filter out high-frequency and low-frequency components and high-frequency noise generated during mixing, resulting in a filtered signal that includes low-frequency beat frequencies and DC leakage. This filtered signal can then be further fed into a high-pass filter. The high-pass filter can be a conventional high-pass filter or a DC blocking circuit. The cutoff frequency of the high-pass filter can be higher than the frequency of the DC leakage signal but lower than the lowest possible frequency of the beat frequency signal. The high-pass filter can filter out residual DC components and extremely low-frequency leakage signals from the previous stage signal. Through this cascaded processing flow of first filtering out high frequencies and then filtering out DC, the analog filtering unit can ultimately output a clean beat frequency signal without DC leakage.

[0045] In step S250, the analog-to-digital conversion unit samples the low-frequency beat frequency signal and converts it into a digital difference frequency signal.

[0046] In this embodiment, the digital difference frequency signal can be the signal obtained by sampling and digitizing the low-frequency beat frequency signal through an analog-to-digital converter. This signal can be a discrete digital sequence that retains the frequency information of the original low-frequency beat frequency signal, allowing the signal processing unit to perform further digital processing and analysis.

[0047] In this embodiment, the analog-to-digital conversion unit can be a standalone ADC chip or an on-chip ADC integrated into the MCU. For example, the ADC can be a successive approximation ADC, which can convert analog signals (sampled low-frequency beat signals) into digital signals through a series of comparison and approximation operations. Alternatively, a "Δ-Σ" ADC can be used, which can achieve high-resolution digital output at lower sampling frequencies through oversampling and noise shaping techniques.

[0048] In step S260, the signal processing unit performs frequency domain analysis on the digital difference frequency signal and calculates the target thickness of the object under test based on the analysis results.

[0049] In this embodiment, the target thickness can be the distance from the ultrasonic incident surface of the object under test (i.e., the outer wall that the ultrasonic wave contacts when it enters the object under test) to the desired detection position inside the object that can generate an effective ultrasonic echo. The desired detection position can be the relative bottom surface of the object under test (i.e., the inner wall, which constitutes the overall thickness of the material), or it can be any defect or interface (such as cracks, pores, inclusions, delamination, corrosion pits, etc.) located inside the material and formed due to discontinuities in acoustic impedance.

[0050] In this embodiment, frequency domain analysis can be the process of performing mathematical operations such as Fourier transform on the signal to convert the digital difference frequency signal from a time-domain representation to a frequency-domain representation. Through frequency domain analysis, the various frequency components contained in the digital difference frequency signal and their corresponding amplitude or phase information can be revealed. In this embodiment, by performing frequency domain analysis on the digital difference frequency signal, the dominant frequency component, i.e., the beat frequency, can be accurately identified, and thus used to calculate the target thickness of the object being measured.

[0051] In this embodiment, the signal processing unit can be implemented using various hardware or software modules with data processing capabilities. These include, but are not limited to, microcontroller units (MCUs), digital signal processors (DSPs), and field-programmable gate arrays (FPGAs).

[0052] For example, the signal processing unit can be a digital signal processor (DSP) with a built-in hardware accelerator specifically designed for algorithms such as the Fast Fourier Transform (FFT), enabling efficient frequency domain conversion and analysis of digital difference frequency signals. Alternatively, the signal processing unit can be implemented using a field-programmable gate array (FPGA), employing a hardware description language to implement customized frequency domain analysis logic, thereby achieving higher processing speeds and parallelism.

[0053] The following describes the specific implementation of the ultrasonic thickness measurement method of this application embodiment, taking the user's need to perform non-destructive thickness measurement on a metal plate of unknown thickness as an example. As mentioned above, traditional ultrasonic thickness measurement methods require high-sampling-rate analog-to-digital converters, resulting in high equipment costs and complex data processing. However, the ultrasonic thickness measurement method of this application embodiment can quickly and accurately perform non-destructive testing on the metal plate using low-cost hardware. Specifically, firstly, the signal generation unit can generate a discrete-frequency modulated time-domain ultrasonic excitation signal. For example, the signal frequency starts at 5MHz and increases in steps of 10kHz, with each frequency point lingering for 10 microseconds until it reaches 5.1MHz. The signal generation unit can simultaneously send the generated excitation signal to the ultrasonic transceiver unit and the analog mixer unit. Then, after receiving the excitation signal, the ultrasonic transceiver unit can convert it into ultrasonic waves and emit them towards the upper surface of the metal plate (i.e., the outer wall in contact with the ultrasonic probe). After propagating inside the metal plate, the ultrasonic waves can be reflected when they reach the lower surface (i.e., the inner wall away from the ultrasonic probe), forming an echo. After receiving these echo ultrasonic waves, the ultrasonic transceiver unit converts them back into electrical signals and sends them to the analog mixer unit. In the analog mixer unit, the echo electrical signals received at the same time are analog-mixed with the excitation signal (as the local oscillator signal). Due to a time delay (related to the metal plate thickness) between the echo signal and the excitation signal, this delay results in a small frequency difference between the two. The mixing operation multiplies these two signals, producing a mixed signal containing both the sum and difference of frequencies. This mixed signal is then sent to the analog filter unit. This unit filters out the high-frequency components (i.e., the sum of frequencies) from the mixed signal, retaining the low-frequency difference component, i.e., the low-frequency beat signal. The frequency of this low-frequency beat signal directly reflects the round-trip time of the ultrasonic wave propagating through the metal plate, thus containing information about the metal plate's thickness. The analog filter unit then sends the low-frequency beat signal to the analog-to-digital converter (ADC). Because the frequency of this beat signal has been significantly reduced (e.g., from the MHz level to the kHz level), the ADC can sample it at a relatively low sampling frequency, for example, at 100 kHz. The sampled analog signal can be converted into a digital difference frequency signal and transmitted to the signal processing unit. Finally, the signal processing unit can perform frequency domain analysis on the digital difference frequency signal, for example, using a Fast Fourier Transform (FFT) algorithm to obtain its frequency domain amplitude spectrum. The dominant beat frequency can be clearly identified in the amplitude spectrum. Based on this beat frequency, the known frequency modulation slope of the excitation signal, and the propagation speed of the ultrasonic wave in the metal plate material, the signal processing unit can quickly and accurately calculate the thickness of the metal plate.

[0054] In the above scheme, by employing a discrete frequency modulated time-domain ultrasonic excitation signal and combining it with analog mixing down-conversion technology, the high-frequency ultrasonic echo signal is effectively converted into a low-frequency beat frequency signal. Compared to traditional ultrasonic thickness measurement (pulse echo method), which directly relies on time-of-flight measurement and requires an analog-to-digital converter with an extremely high sampling rate to capture narrow pulse echoes, the technical solution of this application effectively extracts the low-frequency beat frequency signal carrying thickness information, effectively overcoming the dependence on high-sampling-rate analog-to-digital converters in traditional methods. Instead, it samples the low-frequency beat frequency signal, significantly reducing the sampling rate requirement of the analog-to-digital converter unit. This allows for the selection of lower-cost, lower-power medium-to-low sampling-rate analog-to-digital converters, significantly reducing the hardware cost of the system. Furthermore, due to the reduced sampling rate, the amount of data generated is also greatly reduced, thereby reducing the complexity of data processing and the computational resource requirements. Moreover, since the signal generation unit only needs to generate a discrete frequency modulated time-domain ultrasonic excitation signal, the control is simple and does not require continuous linear calibration, thus further reducing the implementation complexity and cost of the signal generation unit. Therefore, the ultrasonic thickness measurement method of this application embodiment significantly reduces the hardware cost of the system, improves the system response speed and measurement efficiency, and can realize the miniaturization and portability of the system while maintaining high thickness measurement accuracy.

[0055] In one embodiment, the ultrasonic thickness measurement system further includes a control unit connected to the signal generation unit; the ultrasonic thickness measurement method of this application embodiment further includes the following steps: In step S101, the control unit sends a configuration command to the signal generation unit to configure the discrete frequency modulation parameters of the time-domain ultrasonic excitation signal, wherein the discrete frequency modulation parameters include the frequency step value and the dwell time of each frequency point.

[0056] In step S210, the signal generation unit generates a discrete frequency modulated time-domain ultrasonic excitation signal, including the following steps: Step S211: In response to the configuration command, a time-domain ultrasonic excitation signal is generated in which the frequency exhibits discrete step changes on the time axis according to the frequency step value and the dwell time.

[0057] In this embodiment, the control unit can be a component in the ultrasonic thickness measurement system responsible for managing and coordinating system operation. Its function is to provide a centralized control point, enabling the system to intervene in and adjust the output of the signal generating unit according to external commands or preset logic.

[0058] In this embodiment, the control unit can be a microcontroller, a digital signal processor, a field-programmable gate array (FPGA), or an embedded computer system, and can establish a communication connection with the signal generating unit via wired or wireless means. For example, data and instructions can be transmitted through interfaces such as serial peripheral interfaces, I2C buses, universal asynchronous transceivers, or Ethernet.

[0059] In this embodiment, the control unit can be an independent processing module, such as a separate microprocessor. Alternatively, the control unit can be integrated with the signal processing unit in the same processing module, such as integrating them into the same MCU.

[0060] In this embodiment, the configuration instructions can be a series of data or commands sent by the control unit to the signal generating unit, used to set or modify the operating mode and parameters of the signal generating unit. These instructions can be predefined protocol commands or digital sequences containing specific parameter values. Their purpose is to achieve dynamic adjustment of the discrete frequency modulation parameters of the time-domain ultrasonic excitation signal to adapt to different measurement scenarios and accuracy requirements.

[0061] In this embodiment, the discrete frequency modulation parameters can be key values ​​that define the frequency variation characteristics of the time-domain ultrasonic excitation signal. The discrete frequency modulation parameters can include at least the frequency step value and the dwell time at each frequency point. The frequency step value refers to the frequency interval between adjacent frequency points during discrete frequency modulation, which directly affects the signal's frequency resolution and scan bandwidth. For example, a smaller frequency step value can provide higher frequency resolution, but may require a longer scan time.

[0062] In this embodiment, the dwell time at each frequency point refers to the length of time the signal remains constant at each discrete frequency point, which affects the signal's energy accumulation and measurement stability. For example, a longer dwell time can improve the signal-to-noise ratio, but it will increase the total measurement time. The combination of these parameters determines the spectral and temporal characteristics of the time-domain ultrasonic excitation signal.

[0063] For example, discrete frequency modulation parameters may also include other modulation parameters, such as start frequency, end frequency, sweep bandwidth, and sweep duration. The start frequency can be the initial frequency at the start of the time-domain ultrasonic excitation signal; the end frequency can be the final frequency at the end of the signal. By setting the start and end frequencies, the frequency variation range of the entire excitation signal can be determined to adapt to the ultrasonic frequency requirements of the measured object with different thicknesses or materials. For example, for thinner metal materials, a higher start frequency can be configured to obtain more accurate measurement results, while for thicker non-metallic materials, a lower start frequency can be configured to ensure that the ultrasonic waves can penetrate effectively. The sweep bandwidth can be the difference between the start and end frequencies, which determines the range covered by the signal on the frequency axis. A wider sweep bandwidth helps capture more echo information, thereby potentially improving the accuracy and adaptability of the measurement. The sweep duration can be the total time elapsed from the start to the end of the entire discrete frequency modulation process, determined by the start frequency, end frequency, frequency step value, and dwell time at each frequency point. It is understood that the length of the sweep duration affects the efficiency of thickness measurement, and in practical applications, a trade-off between measurement accuracy and efficiency can be struck.

[0064] It is understood that the signal generation unit can be the core component for generating ultrasonic excitation signals. For example, the signal generation unit can be programmable, dynamically adjusting the output frequency and time sequence of its internal oscillator or synthesizer in response to configuration commands. Specifically, upon receiving a configuration command containing frequency step values ​​and dwell time, the signal generation unit can change the output frequency in discrete steps along the time axis according to these parameters, maintaining the dwell time set in the command at each frequency point, thereby generating a time-domain ultrasonic excitation signal with specific modulation characteristics. This response mechanism enables the signal generation unit to precisely execute the control unit's commands, achieving flexible control of the excitation signal.

[0065] In a specific example, the control unit can be an embedded controller running a real-time operating system and parameter configuration management software. This control unit communicates with the signal generation unit via a serial peripheral interface. The signal generation unit can be a direct digital frequency synthesizer (DDS) chip with programmable frequency, phase, and amplitude control capabilities. In practice, the user inputs the required measurement parameters, such as the target thickness range and desired measurement accuracy, through a user interface (e.g., a touchscreen or host computer software) connected to the control unit. The control unit's software module calculates the optimal discrete frequency modulation parameters based on these inputs, including the frequency step value and the dwell time at each frequency point. For example, if the user requires high-precision measurement, the control unit can calculate a smaller frequency step value (e.g., 10 kHz) and a longer dwell time (e.g., 100 microseconds); if the user requires fast measurement, the control unit can calculate a larger frequency step value (e.g., 50 kHz) and a shorter dwell time (e.g., 20 microseconds). The control unit then encapsulates these calculated parameters into SPI protocol data packets and sends them to the signal generation unit via the SPI interface. After receiving these configuration instructions, the DDS chip in the signal generation unit can update its internal registers. Based on the updated frequency step value and dwell time, the DDS chip can accurately generate a time-domain ultrasonic excitation signal with discrete step changes in frequency on the time axis.

[0066] The ultrasonic thickness measurement method of this application solves the problem of insufficient flexibility caused by fixed parameters in the signal generation process by introducing a control unit, thereby enhancing the customizability and measurement accuracy of the system. This control unit is connected to the signal generation unit and can dynamically generate and send configuration commands to the signal generation unit based on preset measurement strategies, user input, or real-time environmental feedback. The core of these configuration commands lies in defining the discrete frequency modulation parameters of the time-domain ultrasonic excitation signal, specifically including the frequency step value and the dwell time at each frequency point. After receiving these configuration commands, the signal generation unit can respond to them and precisely adjust its internal frequency synthesis mechanism. It can change the output frequency in a discrete step manner on the time axis according to the frequency step value specified in the command, and can maintain the dwell time set in the command at each frequency point, thereby generating a time-domain ultrasonic excitation signal with specific modulation characteristics. This configurable discrete frequency modulated time-domain ultrasonic excitation signal generated by the signal generation unit serves as both the source signal for ultrasonic waves transmitted by the ultrasonic transceiver unit and the local oscillator signal for the analog mixer unit. By precisely controlling the excitation signal parameters through the control unit, the frequency range, frequency resolution, and signal energy of the excitation signal can be optimized according to the material properties, thickness range, or required measurement accuracy of the object being measured. This synergistic effect allows the entire ultrasonic thickness measurement system to adapt more flexibly to various complex measurement tasks, thereby improving the system's versatility and efficiency while ensuring measurement accuracy. Furthermore, this step-based frequency control method is simpler in logic than continuous linear frequency modulation, eliminating the need for complex linearity calibration algorithms and significantly reducing the software design difficulty and hardware implementation cost of the signal generation unit. Simultaneously, the discrete step frequency changes make the signal characteristics at each frequency point more stable, reducing phase noise and frequency jitter that may be introduced by continuous frequency changes, thus helping to improve the purity of the beat frequency signal during subsequent mixing and filtering processes. Therefore, this approach further improves the accuracy of thickness measurement.

[0067] In one implementation, such as Figure 3 As shown, the ultrasonic thickness measurement system 100' further includes a first signal amplifier 170, which is connected to the signal generation unit 110 and the ultrasonic transceiver unit 120. The ultrasonic thickness measurement method of this embodiment further includes the following steps: In step S2201, the first signal amplifier amplifies the time-domain ultrasonic excitation signal and sends the amplified time-domain ultrasonic excitation signal to the ultrasonic transceiver unit.

[0068] The first signal amplifier can be a component used to amplify the power of the time-domain ultrasonic excitation signal generated by the signal generating unit. It is understood that the excitation signal directly output by the signal generating unit is usually of low power, making it difficult to drive the ultrasonic transceiver unit (such as an ultrasonic transducer) to effectively emit ultrasonic waves of sufficient intensity, especially when penetrating thick or highly attenuated materials. Insufficient signal strength results in weak echo signals, affecting subsequent detection and analysis. Therefore, the first signal amplifier can increase the voltage or current amplitude of the excitation signal, enhancing its driving capability, enabling the ultrasonic transceiver unit to efficiently convert the electrical signal into mechanical vibrations (i.e., ultrasonic waves) with sufficient energy, allowing the ultrasonic waves to propagate smoothly within the object under test and generate detectable echoes.

[0069] For example, the first signal amplifier can be implemented using a high-efficiency power amplifier circuit, such as a Class AB or Class D power amplifier, to provide sufficient gain while minimizing its own power consumption and heat generation. The amplification factor of the first signal amplifier can be set according to the impedance characteristics of the ultrasonic transceiver unit, the required ultrasonic transmission power, and the output signal amplitude of the signal generating unit.

[0070] In the above scheme, the time-domain ultrasonic excitation signal is amplified by a first signal amplifier, which significantly improves the power level of the excitation signal. This allows the ultrasonic transceiver unit to obtain sufficient driving energy, thereby effectively emitting ultrasonic waves of appropriate intensity. This enables the ultrasonic waves to propagate stably in the object under test and generate detectable echo signals, improving the signal-to-noise ratio of the echo signals. This also improves the accuracy of extracting low-frequency beat signals, thereby improving the accuracy of thickness measurement.

[0071] In one implementation, step S250, where the analog-to-digital conversion unit samples the low-frequency beat frequency signal, includes the following steps: Step S251: Sample the low-frequency beat frequency signal at a preset sampling frequency, wherein the preset sampling frequency is significantly lower than the center frequency of the time-domain ultrasonic excitation signal.

[0072] In this embodiment, the preset sampling frequency is significantly lower than the center frequency of the time-domain ultrasonic excitation signal and satisfies the Nyquist sampling theorem, that is, the preset sampling frequency can be greater than or equal to twice the highest frequency of the low-frequency beat frequency signal.

[0073] In this embodiment, the center frequency of the time-domain ultrasonic excitation signal can be the center value of the frequency range of the ultrasonic signal emitted by the ultrasonic transceiver unit to the object under test. For example, in industrial non-destructive testing, the center frequency of the time-domain ultrasonic excitation signal is usually in the megahertz (MHz) range, such as 2MHz, 5MHz, or 10MHz. In this embodiment, there is a difference of one or more orders of magnitude between the sampling frequency of the analog-to-digital conversion unit (i.e., the preset sampling frequency) and the center frequency of the time-domain ultrasonic excitation signal; that is, the preset sampling frequency is much smaller than the center frequency of the time-domain ultrasonic excitation signal.

[0074] It is understandable that, since the low-frequency beat signal is a difference frequency signal after frequency conversion and mixing, its frequency is much lower than the center frequency of the original ultrasonic excitation signal. Therefore, the analog-to-digital converter (ADC) uses a sampling frequency significantly lower than this center frequency, which allows it to accurately capture all the information of the low-frequency beat signal while fully satisfying the Nyquist sampling theorem. In other words, the ADC does not need to have the ability to process high-frequency signals, and a lower-cost, lower-power ADC can be selected. At the same time, the lower sampling frequency also means a significant reduction in the amount of data generated per unit time, significantly reducing the data processing burden and storage requirements of subsequent signal processing units. This allows for further reduction in hardware costs and data processing complexity while maintaining high measurement accuracy.

[0075] For example, the center frequency of the time-domain ultrasonic excitation signal is 5MHz, while the frequency of the low-frequency beat signal obtained by frequency conversion is typically in the range of several hundred Hz to tens of thousands of Hz. In this case, the preset sampling frequency can be set to 2.5 to 3 times the highest frequency of the beat signal. For instance, when the highest frequency of the beat signal is 10kHz, the preset sampling frequency can be set to 25kHz to 30kHz, which is much lower than the 5MHz center frequency. Using a sampling frequency significantly lower than the center frequency of the time-domain ultrasonic excitation signal in the analog-to-digital conversion unit not only ensures accurate sampling and digitization of the low-frequency beat signal and reduces aliasing distortion, but also significantly reduces the data processing pressure on the analog-to-digital conversion unit and the amount of data stored. This further reduces the system's hardware processing requirements, facilitating system miniaturization and low-power design.

[0076] In one embodiment, step S260, where the signal processing unit performs frequency domain analysis on the digital difference frequency signal, includes the following steps: In step S261, the signal processing unit applies a window function to the digital difference frequency signal for weighting processing to suppress spectral leakage and obtain a weighted digital signal sequence. In step S262, the signal processing unit uses the fast Fourier transform algorithm to convert the weighted digital signal sequence from the time domain signal to the frequency domain signal to obtain the frequency domain amplitude spectrum. In step S263, the signal processing unit calculates the target thickness of the object under test based on the frequency domain amplitude spectrum.

[0077] In this embodiment, the window function may include, but is not limited to, the Hanning window function, the Hamming window function, and the Blackman window function. Window functions can be used to weight time-domain signals of finite length, reducing spectral leakage caused by signal truncation. Spectral leakage is a phenomenon that occurs during Fast Fourier Transform (FFT), where, due to the finite length and non-periodic nature of the signal, signal energy "leaks" from its actual frequency to other frequency components. The frequency domain amplitude spectrum is a graph obtained after the signal undergoes FFT, used to describe the distribution of signal amplitude (or energy) with frequency.

[0078] For example, in step S261, the digital difference frequency signal can be multiplied by a window function to achieve signal weighting. The window function is typically finite in the time domain and gradually decays to zero at both ends, smoothing the beginning and end of the signal and making the changes at the truncation points more gradual, thereby reducing the amplitude of sidelobes in the spectrum and minimizing energy diffusion to non-true frequency components. In step S262, the Fast Fourier Transform (FFT) algorithm can be used to perform frequency domain analysis on the digital signal sequence after window function weighting. The Fast Fourier Transform is an efficient algorithm for calculating the Discrete Fourier Transform, capable of quickly converting time-domain signals to the frequency domain and revealing the frequency components of the signal. Through FFT, the amplitude and phase information of the signal at different frequencies can be obtained, resulting in a frequency domain amplitude spectrum that accurately reflects the energy magnitude of each frequency component. In step S263, various suitable methods can be used to calculate the target thickness of the object under test based on the frequency domain amplitude spectrum. It is understandable that the thickness of the object being measured is usually related to the frequency difference between the echo signal and the excitation signal (i.e., the beat frequency), and the beat frequency information is reflected at specific frequency points in the amplitude spectrum in the frequency domain. By analyzing the amplitude spectrum, the main beat frequency components can be identified, and then, combined with the known ultrasonic propagation speed and system parameters, the thickness of the object being measured can be calculated. For example, the frequency point corresponding to the maximum peak in the amplitude spectrum can be searched as the measurement beat frequency, or the beat frequency can be determined by performing more complex analyses of the amplitude spectrum (such as spectral line fitting).

[0079] In a specific example, the signal processing unit can first apply a Hamming window function to the digital difference frequency signal output by the analog-to-digital converter for weighting, effectively suppressing spectral leakage caused by signal truncation, thereby obtaining a weighted digital signal sequence. Next, a Fast Fourier Transform module based on the radix-2 algorithm can be used to process this weighted digital signal sequence, efficiently converting it from the time domain to the frequency domain and generating the frequency domain amplitude spectrum of the digital difference frequency signal. Finally, by analyzing this frequency domain amplitude spectrum, the frequency point with the largest amplitude is identified as the measurement beat frequency, and combined with preset parameters such as the propagation speed of ultrasound in the measured object and the frequency modulation slope of the time-domain ultrasonic excitation signal, the thickness of the measured object is calculated.

[0080] In the above scheme, by applying a window function to the digital difference frequency signal for weighting, spectral leakage can be significantly suppressed, making the frequency domain amplitude spectrum obtained by the subsequent fast Fourier transform more accurate and realistic. This results in higher accuracy and reliability of the thickness information of the measured object extracted from the frequency domain amplitude spectrum, thereby improving the measurement performance of the entire ultrasonic thickness measurement system. Especially when the analog-to-digital converter samples the low-frequency beat frequency signal at a lower sampling frequency, this scheme can effectively compensate for the spectral analysis error caused by the sampling rate limitation, enabling the system to achieve high-precision thickness measurement while reducing hardware costs and data processing volume.

[0081] In one implementation, step S262, the signal processing unit uses the Fast Fourier Transform algorithm to convert the weighted digital signal sequence from a time-domain signal to a frequency-domain signal to obtain a frequency-domain amplitude spectrum, including the following steps: Step S2621: The signal processing unit performs time-domain zero-padding on the weighted digital difference frequency signal sequence to obtain a zero-padding digital difference frequency signal sequence. In step S2622, the signal processing unit performs a fast Fourier transform on the zero-padded digital difference frequency signal sequence to obtain the frequency domain amplitude spectrum.

[0082] In this embodiment, the time-domain zero-padding operation can be achieved by adding zero values ​​to the end of the original digital signal sequence (the weighted digital difference frequency signal sequence) to increase the effective length of the sequence. This improves the frequency resolution of the subsequent Fast Fourier Transform (FFT) without introducing additional information. Specifically, the sequence length can be extended by appending a specified number of zero values ​​to the end of the original sequence, or by filling the original data at the beginning position and filling the remaining space with zeros in the data storage or processing buffer. The zero-padding digital difference frequency signal sequence can be a digital signal sequence with increased length after the time-domain zero-padding operation, providing a longer input for the FFT and thus enabling the generation of a more refined frequency domain amplitude spectrum.

[0083] Specifically, after receiving the weighted digital difference frequency signal sequence, the signal processing unit performs time-domain zero-padding on the sequence to improve the accuracy of spectral analysis. This increases the sequence length, allowing the subsequent Fast Fourier Transform (FFT) to generate a denser frequency sampling point, effectively improving the frequency resolution of the frequency domain amplitude spectrum. Next, the signal processing unit performs a FFT on the zero-padding digital difference frequency signal sequence. Due to the increased effective length of the input sequence, the transform process generates a higher-resolution frequency domain amplitude spectrum. This high-resolution amplitude spectrum allows for more accurate identification of beat frequency peaks, providing more accurate frequency information for subsequent calculations of the target thickness of the object being measured.

[0084] The above scheme effectively improves the frequency resolution of the amplitude spectrum of the digital difference frequency signal, enabling more accurate identification of the beat frequency during frequency domain analysis. It solves the problem of low spectral resolution caused by insufficient sequence length, thereby significantly improving the accuracy of the ultrasonic thickness measurement system in calculating the thickness of the object being measured.

[0085] It should be noted that in the ultrasonic thickness measurement method of this application embodiment, due to the limited resolution of the digital generation unit and the limited number of physical sampling points of the analog-to-digital conversion unit in the low-cost hardware device, directly performing Fourier transform may cause frequency quantization errors, resulting in the true peak frequency falling into the spectral gaps due to the "pick-up fence effect," failing to meet the high-precision thickness measurement requirements. To address this technical problem, this application does not adopt the traditional path of increasing hardware costs, but creatively combines "stepped frequency sweeping" with "time-domain zero-padding interpolation," using zero-padding operations to perform high-density interpolation of the spectrum, effectively overcoming the limitation of discrete spectral lines on frequency positioning. It should be noted that time-domain zero-padding in this application is not only used as an auxiliary means for spectrum smoothing, but also to compensate for the inherent accuracy loss of the stepping architecture. Without increasing the physical sampling burden, it significantly improves the computational resolution, enabling the system to accurately capture and correct frequency deviations caused by quantization errors. Thus, it achieves thickness measurement accuracy meeting industrial-grade requirements under low-cost hardware conditions, achieving unexpected technical results.

[0086] Furthermore, zero-padding in the time domain is an example of a digital signal processing technique used in this application embodiment to accurately estimate the peak position of the spectrum. In other embodiments, other interpolation estimation methods may also be used to estimate the peak position of the spectrum.

[0087] In one implementation, such as Figure 3 As shown, the ultrasonic thickness measurement system 100' of this application embodiment further includes a second signal amplifier 180, which is connected to the analog filtering unit 140 and the analog-to-digital conversion unit 150 respectively.

[0088] The ultrasonic thickness measurement method in this application embodiment further includes the following steps: In step S2501, the second signal amplifier amplifies the low-frequency beat signal and sends the amplified low-frequency beat signal to the analog-to-digital conversion unit.

[0089] In this embodiment, the second signal amplifier can be a gain amplifier circuit located after the analog filtering unit and before the analog-to-digital conversion unit, used to amplify the pure beat frequency signal.

[0090] In one example, the second signal amplifier can be configured as an operational amplifier, either as a non-inverting or inverting amplifier circuit, with the gain set by adjusting the ratio of the feedback resistor. In another example, the second signal amplifier can also be a dedicated low-noise amplifier to amplify weak signals while minimizing introduced noise. In this embodiment, the second signal amplifier can specifically be used to increase the amplitude of low-frequency beat signals, making them easier for analog-to-digital converters to accurately identify and quantize. Furthermore, the second signal amplifier can be configured in a fixed-gain mode, where the amplification factor is preset, suitable for scenarios with small signal amplitude variations. Alternatively, the second signal amplifier can also be configured in a variable-gain mode, dynamically adjusting the amplification factor via an external control signal to adapt to signal amplitude variations under different measured objects or measurement conditions.

[0091] It is understandable that the amplitude of low-frequency beat signals may be very weak due to the attenuation of ultrasonic waves during propagation within the measured object and other system losses. By using a second signal amplifier to amplify the low-frequency beat signal after low-pass analog filtering, its amplitude can be significantly increased. This allows the analog-to-digital converter (ADC) to sample a beat signal with sufficient strength, fully utilizing its quantization range and effectively reducing quantization errors. This enables the ADC to digitize the low-frequency beat signal with higher accuracy, providing high-quality digital input for subsequent frequency domain analysis and thickness calculation in the signal processing unit. Therefore, this approach significantly improves the sampling accuracy of the ADC for low-frequency beat signals. Especially in low signal-to-noise ratio environments or when measuring objects with significant attenuation, it effectively improves the accuracy and reliability of the ultrasonic thickness measurement system.

[0092] In one embodiment, step S240, where the analog filtering unit performs filtering processing on the mixing signal, includes the following steps: Step S241: The analog filtering unit filters out the high-frequency components and DC leakage signals in the mixing signal to obtain a low-frequency beat signal that contains only the thickness information of the object being measured.

[0093] In this embodiment, since the transmitted signal uses discrete frequency modulation, the leakage signal directly coupled from the transmitter to the receiver has no propagation delay, with a delay τ≈0. After mixing with the local oscillator signal, the leakage signal is converted into a DC or near-DC very low-frequency component. Meanwhile, the real echo signal, which has a propagation delay, is mixed to form a low-frequency beat signal that is positively correlated with the delay. The leakage signal and the useful beat signal are naturally separated in the frequency domain; the former is concentrated near zero frequency, while the latter is distributed in a higher frequency band.

[0094] Based on the above frequency domain separation characteristics, the analog filtering unit in this application embodiment can also filter out DC and near-DC leakage signals before high-gain amplification, reducing the occupation of the dynamic range of the subsequent amplifier by useless strong leakage signals, so that weak echo signals can be reliably extracted.

[0095] Optionally, the analog filtering unit is implemented using a bandpass filter. The lower cutoff frequency of the bandpass filter is higher than the DC leakage signal frequency, used to filter out DC and extremely low frequency leakage; the upper cutoff frequency is lower than the high-frequency sum-frequency component frequency, used to filter out high-frequency noise and sum-frequency signals, retaining only the useful beat frequency signal.

[0096] Alternatively, the analog filtering unit can also be implemented by cascading a low-pass filter and a high-pass filter. First, the low-pass filter removes high-frequency and low-frequency components and noise, and then the high-pass filter or DC blocking circuit removes DC and very low-frequency leakage, finally outputting a clean beat frequency signal without DC offset.

[0097] In the above scheme, the useful low-frequency beat frequency signal and interference components in the mixing signal are effectively separated by the analog filtering unit, significantly improving the signal-to-noise ratio. By filtering out high-frequency components, the interference of high-frequency noise on subsequent analog-to-digital conversion and signal processing is reduced; while filtering out DC leakage signals reduces the strong DC signals occupying the dynamic range of the subsequent amplifier, allowing the weak useful beat frequency signal to be effectively amplified and accurately acquired, further improving the accuracy of subsequent frequency domain analysis and thickness calculation.

[0098] In one embodiment, step S260, where the signal processing unit performs frequency domain analysis on the digital difference frequency signal, includes the following steps: In step S2601, the signal processing unit uses the fast Fourier transform algorithm to convert the digital difference frequency signal from the time domain signal to the frequency domain signal to obtain the frequency domain amplitude spectrum. In step S2602, the signal processing unit searches for the maximum amplitude value in the frequency domain amplitude spectrum and determines the frequency point corresponding to the maximum amplitude value as the measurement beat frequency; In step S2603, the signal processing unit calculates the target thickness of the object under test based on the measured beat frequency, the frequency modulation slope of the time-domain ultrasonic excitation signal, and the propagation speed of the ultrasonic wave in the object under test.

[0099] It is understandable that the Fast Fourier Transform (FFT) can convert a discrete-time signal into a frequency-domain representation, thus clearly presenting each frequency component and its corresponding amplitude, obtaining the frequency-domain amplitude spectrum. In the frequency-domain amplitude spectrum, the frequency point with the largest amplitude is the most representative effective component. By finding the maximum amplitude value in the frequency-domain amplitude spectrum and determining its corresponding frequency point as the measurement beat frequency, noise and interference can be suppressed, improving the accuracy and reliability of beat frequency identification. In practical implementation, the peak value can be directly traversed to find the peak value, or the spectrum can be smoothed first to improve anti-interference capability before finding the peak value.

[0100] In one example, a defined mathematical relationship exists between the beat frequency, the frequency modulation slope of the time-domain ultrasonic excitation signal, and the propagation speed of the ultrasonic wave in the object under test. In step S2603, the signal processing unit can substitute these parameters into the corresponding mathematical formula to directly derive the thickness value of the object under test. In another example, a calibration model or lookup table based on these parameters can be pre-established, and the thickness of the object under test can be obtained by looking up the table or calculating the model, thereby simplifying the complexity of real-time calculation.

[0101] In the above scheme, the frequency domain analysis process of the digital difference frequency signal is optimized to improve the accuracy of beat frequency identification and thickness measurement. The signal processing unit performs a fast Fourier transform on the digital difference frequency signal to obtain the frequency domain amplitude spectrum. Then, the measurement beat frequency is determined by searching for the maximum amplitude, which can effectively suppress noise interference and make beat frequency identification accurate and reliable. Finally, based on the measured beat frequency, frequency modulation slope, and sound velocity, the thickness of the measured object is quickly calculated. This scheme can obtain accurate measurement results under low sampling rate conditions, significantly reducing hardware costs and data processing volume.

[0102] In one embodiment, step S2603, in which the signal processing unit calculates the target thickness of the object being measured, includes the following steps: Step S2603a: Calculate the target thickness of the object being measured using the following formula (a): . Formula (1) in, d Indicates thickness, c This indicates the speed of sound in which ultrasound waves propagate through the object being measured. f b Indicates the measured beat frequency. μ Indicates the frequency modulation slope. This indicates the pre-calibrated inherent system delay time.

[0103] In this embodiment, the frequency modulation slope can be the rate at which the frequency of the time-domain ultrasonic excitation signal changes with time. This rate can be a preset value or dynamically configured by the control unit. For example, it can be determined by controlling the frequency step value and the dwell time at each frequency point. The time delay can be a fixed time delay caused by the system hardware and the signal transmission path itself, which occurs throughout the entire path from the ultrasonic wave emitted by the signal generating unit, to its conversion into an ultrasonic wave by the ultrasonic transceiver unit, then the received echo and its conversion back into an electrical signal, and finally to the analog mixer unit for mixing. This delay can be obtained through calibration experiments with known thickness or without a measured object. For example, by measuring the beat frequency signal without a measured object or using a standard block of known thickness, and then inferring the delay from other known parameters. Alternatively, precise measurements can be taken through a specialized calibration procedure.

[0104] It is understood that measuring beat frequency includes the round-trip propagation time of the ultrasonic wave in the object under test, as well as the system's own fixed delay time. In this embodiment, to accurately calculate the target thickness of the object under test, the system's inherent delay time is subtracted from the total propagation time. Therefore, the term in the above formula represents the total time delay of the ultrasonic wave from transmission to reception, f. b / μ minus Then, the actual round-trip propagation time of the ultrasonic wave in the object being measured can be obtained. Dividing the round-trip propagation time by 2 and multiplying it by the speed of sound yields the precise thickness of the object. This calculation method effectively compensates for the fixed delays caused by system hardware and signal transmission paths, further improving the accuracy and efficiency of thickness measurement.

[0105] For example, the frequency modulation slope can be calculated using the following formula (ii): . Formula (II) in, This represents the sweep bandwidth of the time-domain ultrasonic excitation signal, which can specifically be the difference between the termination frequency and the starting frequency. This indicates the sweep duration of the time-domain ultrasonic excitation signal.

[0106] In a specific example of measuring the thickness of a steel material, assuming the speed of sound propagating in the steel is 5.9 mm / µs, the sweep bandwidth B of the time-domain ultrasonic excitation signal generated by the signal generation unit is 5 MHz, and the sweep duration is... The pre-calibrated inherent system delay time is 10µs. The beat frequency is 0.5µs. When measuring the thickness of this steel, the signal processing unit obtains the measurement beat frequency f through frequency domain analysis. b The frequency is 1.2MHz. First, μ = 0.5MHz / µs can be calculated using formula (I) above. Then, the parameters can be substituted into the thickness calculation formula (II) to obtain the thickness measurement value of the steel as 5.605mm.

[0107] The following is combined Figure 3 , Figure 4 and Figure 5 This application describes the implementation principle of an ultrasonic thickness measurement method according to another specific embodiment. For example... Figure 3 As shown, the ultrasonic thickness measurement system 100' includes: First, the control unit can send a frequency configuration command to the signal generation unit. For example, the configuration command may include: a start frequency, an end frequency, a sweep bandwidth, a frequency step value, a dwell time, and a sweep duration. For instance, the center frequency between the start and end frequencies is approximately 5MHz. In response to receiving the configuration command, the signal generation unit can generate a stepped sweep signal. Specifically, according to the configuration command, the signal generation unit can synthesize and output a time-domain ultrasonic excitation signal (time-domain voltage waveform) within the sweep bandwidth defined by the start and end frequencies, according to the frequency step value and dwell time, within the sweep duration, causing the output signal frequency to be discretely step-modulated over time, gradually jumping from the start frequency to the end frequency.

[0108] Next, the signal generation unit can simultaneously send the time-domain ultrasonic excitation signal to the analog mixing unit (i.e., Figure 4 The system consists of an analog mixer and a first signal amplifier. The first signal amplifier amplifies the time-domain ultrasonic excitation signal, generating a first electrical signal which is then transmitted to the ultrasonic transceiver unit. The ultrasonic transceiver unit converts the first electrical signal into ultrasonic waves in the form of mechanical energy. If the ultrasonic transceiver unit uses a piezoelectric ceramic probe, the ultrasonic waves can enter the test object from its outer wall through a coupling agent. If the ultrasonic transceiver unit uses an electromagnetic ultrasonic probe, a coupling agent is not required. The ultrasonic waves are reflected inside the test object due to impedance mismatch, returning to the ultrasonic transceiver unit through the outer wall of the test object. The ultrasonic transceiver unit then converts the mechanical energy into a second electrical signal and sends it to the analog mixer unit.

[0109] Then, after receiving the second electrical signal, the analog mixing unit performs difference frequency processing on the second electrical signal and the time-domain ultrasonic excitation signal (which serves as the local oscillator signal), outputting a mixed signal containing sum frequency and difference frequency components, which is then sent to the analog filtering unit. The analog filtering unit can be configured with a preset cutoff frequency to filter out high-frequency sum frequency components and out-of-band noise in the mixed signal, while also filtering out the dynamic range space occupied by the DC leakage signal, retaining only the analog difference frequency signal (i.e., the beat frequency signal) containing the thickness information of the measured object, and sending the analog difference frequency signal to the second signal amplifier. The second signal amplifier can amplify only the pure beat frequency signal to generate an enhanced difference frequency signal, effectively solving the hardware dynamic range bottleneck caused by reflected waves in ultrasonic thickness measurement and achieving high signal-to-noise ratio extraction of weak echoes.

[0110] Next, the analog-to-digital converter (ADC) can discretize the enhanced beat frequency signal at a preset sampling rate, convert it into a digital beat frequency signal, and then transmit it to the signal processing unit. The preset sampling rate is much lower than the center frequency of the excitation signal (5MHz). For example, a preset sampling rate of 250kHz can significantly reduce hardware costs and adapt to the processing requirements of low-frequency beat frequency signals.

[0111] Finally, the signal processing unit can perform frequency domain analysis on the digital difference frequency signal to calculate the thickness of the object under test. Specifically, referring to Figure 5, the signal processing unit can perform the following steps to achieve frequency domain analysis and thickness calculation of the digital difference frequency signal: Step S510: Receive digital difference frequency signal; Step S520: Apply a window function (such as a Hanning window) to the digital difference frequency signal for weighting to suppress spectral leakage and obtain a weighted digital signal sequence. Step S530: Perform time-domain zero-padding on the weighted digital difference frequency signal sequence to obtain a zero-padding digital difference frequency signal sequence; Step S540: Using the Fast Fourier Transform algorithm, the weighted digital signal sequence is transformed from the time domain to the frequency domain to obtain the frequency domain amplitude spectrum. Step S550: Search for the maximum amplitude value in the frequency domain amplitude spectrum; Step S560: Determine the frequency point corresponding to the maximum amplitude as the measurement beat frequency; Step S570: Calculate the thickness of the object being measured based on the measured beat frequency, the frequency modulation slope of the step sweep signal, the sound velocity of the object being measured, and the pre-calibrated system delay time.

[0112] In the above scheme, high-frequency ultrasonic echoes are converted into low-frequency beat signals through analog mixing and down-conversion. Only a low-cost general-purpose ADC (such as an MCU-integrated ADC) at the 250kHz level is needed to effectively acquire the low-frequency beat signals, replacing high-speed ADCs above 50MHz in existing technologies. This significantly reduces the performance requirements of core hardware and system cost, while also reducing data processing volume. Furthermore, to address the spectral fence effect caused by step-sweep and low sampling rates, time-domain zero-padding technology is introduced. This increases the FFT spectral interpolation density without increasing physical sampling time, precisely locating spectral peaks and overcoming the frequency resolution bottleneck of conventional low-cost ultrasonic thickness measurement architectures. This achieves sub-millimeter or even micrometer-level thickness measurement accuracy on a low-cost architecture. In addition, the analog filtering unit filters out sum-frequency components and high-frequency background noise. Combined with the energy focusing characteristics of FFT frequency domain analysis, even in low signal-to-noise ratio industrial environments, it can accurately extract weak echo features submerged in noise, improving measurement stability and reliability. Furthermore, the low data throughput and computational load enable the ultrasonic thickness measurement architecture of this embodiment to run in real time in a low-power microcontroller (MCU) without relying on an FPGA or high-performance DSP. This facilitates the integration of portable devices and low-power design, further expanding the application possibilities of ultrasonic thickness measurement technology in scenarios such as rapid on-site inspection and mobile inspection.

[0113] It should be understood that the above examples are provided to help those skilled in the art understand the embodiments of this application, and are not intended to limit the embodiments of this application to the specific values ​​or scenarios illustrated. Those skilled in the art can obviously make various equivalent modifications or changes based on the above examples, and such modifications or changes also fall within the scope of the embodiments of this application.

[0114] This application also provides an ultrasonic thickness measurement system. For example... Figure 1 As shown, the ultrasonic thickness measurement system 100 provided in this application embodiment includes: The signal generating unit 110 is configured to generate a time-domain ultrasonic excitation signal with discrete frequency modulation. The ultrasonic transceiver unit 120, connected to the signal generating unit 110, is configured to: convert the time-domain ultrasonic excitation signal into an ultrasonic wave and transmit it to the object under test; receive the echo ultrasonic wave reflected from inside the object under test; and convert the echo ultrasonic wave into an echo electrical signal. The analog mixing unit 130 is connected to the signal generating unit 110 and the ultrasonic transceiver unit 120 respectively, and is configured to: perform analog mixing of the echo electrical signal and the time-domain ultrasonic excitation signal, which is the local oscillator signal, to obtain a mixed signal; The analog filtering unit 140, connected to the analog mixing unit 130, is configured to: filter the mixing signal to remove high-frequency components in the mixing signal and obtain a low-frequency beat frequency signal containing the thickness information of the object being measured. The analog-to-digital conversion unit 150, connected to the analog filtering unit 140, is configured to sample the low-frequency beat frequency signal and convert it into a digital difference frequency signal. The signal processing unit 160, connected to the analog-to-digital conversion unit 150, is configured to perform frequency domain analysis on the digital difference frequency signal and calculate the target thickness of the object under test based on the analysis results.

[0115] In one implementation, such as Figure 3 As shown, the ultrasonic thickness measurement system 100' also includes a control unit 190 connected to the signal generation unit 110; The control unit 190 is configured to send a configuration command to the signal generation unit 110 to configure the discrete frequency modulation parameters of the time-domain ultrasonic excitation signal, wherein the discrete frequency modulation parameters include a frequency step value and a dwell time at each frequency point. The signal generation unit generates a discrete-frequency modulated time-domain ultrasonic excitation signal, which is configured as follows: In response to configuration commands, a time-domain ultrasonic excitation signal is generated, in which the frequency exhibits discrete step changes on the time axis according to the frequency step value and the dwell time.

[0116] In some examples, the control unit and the signal processing unit may belong to different hardware modules, that is, physically independent hardware components that interact with each other through a communication bus.

[0117] In other examples, the control unit and signal processing unit can also be integrated into the same processor or microcontroller. It is understood that integrating the control unit and signal processing unit reduces communication latency between modules and improves system response speed. For example, the control unit and signal processing unit can be integrated into the same hardware device, such as a microcontroller (MCU), digital signal processor (DSP), field-programmable gate array (FPGA), or central processing unit (CPU). The integrated hardware device contains both control logic for configuring the signal generation unit parameters and a computational unit for digital signal processing, thereby achieving efficient control and data processing of the entire ultrasonic thickness measurement process. For example, the control unit and signal processing unit are integrated into the same ARM architecture microcontroller. This microcontroller can send frequency configuration commands to the signal generation unit via the SPI interface, and can also receive digital difference frequency signals and perform FFT operations via an on-chip integrated ADC or an external ADC interface. This integration scheme further reduces system size and power consumption.

[0118] In one implementation, the analog-to-digital conversion unit samples the low-frequency beat frequency signal and is configured to: The low-frequency beat frequency signal is sampled at a preset sampling frequency, which is significantly lower than the center frequency of the time-domain ultrasonic excitation signal.

[0119] In one implementation, the signal processing unit performs frequency domain analysis on the digital difference frequency signal and is configured to: A window function is applied to the digital difference frequency signal for weighting to suppress spectral leakage, resulting in a weighted digital signal sequence. Using the Fast Fourier Transform algorithm, the weighted digital signal sequence is converted from a time domain signal to a frequency domain signal to obtain the frequency domain amplitude spectrum; The target thickness of the object under test is calculated based on the frequency domain amplitude spectrum.

[0120] In one implementation, the signal processing unit uses a Fast Fourier Transform algorithm to convert the weighted digital signal sequence from a time-domain signal to a frequency-domain signal, obtaining a frequency-domain amplitude spectrum, which is configured as follows: The weighted digital difference frequency signal sequence is zero-padded in the time domain to obtain the zero-padded digital difference frequency signal sequence. Perform a Fast Fourier Transform on the zero-padded digital difference frequency signal sequence to obtain the frequency domain amplitude spectrum.

[0121] In one embodiment, the ultrasonic thickness measurement system further includes a first signal amplifier and / or a second signal amplifier; The first signal amplifier is connected to both the signal generating unit and the ultrasonic transceiver unit, and is configured as follows: The time-domain ultrasonic excitation signal is amplified, and the amplified time-domain ultrasonic excitation signal is sent to the ultrasonic transceiver unit. The second signal amplifier is connected to both the analog filtering unit and the analog-to-digital converter unit, and is configured as follows: The low-frequency beat signal is amplified and then sent to the analog-to-digital conversion unit.

[0122] like Figure 3 As shown, the ultrasonic thickness measurement system 100 of this application embodiment also includes a first signal amplifier 170 and a second signal amplifier 180.

[0123] The first signal amplifier 170 is connected between the signal generating unit 110 and the ultrasonic transceiver unit 120. Its main function is to amplify the power of the time-domain ultrasonic excitation signal generated by the signal generating unit 110, so that the ultrasonic transceiver unit 120 can generate ultrasonic waves of sufficient intensity, so that the ultrasonic waves have sufficient penetrating power in the object being measured, thereby improving the detection sensitivity.

[0124] The second signal amplifier 180 is connected to both the analog filter unit 140 and the analog-to-digital converter unit 150. The second signal amplifier 180 can amplify the low-frequency beat signal output by the analog filter unit 140 to increase the signal amplitude, so that the subsequent analog-to-digital converter unit 150 can accurately sample the low-frequency beat signal carrying the thickness information of the object being measured.

[0125] It is understandable that the settings of these two signal amplifiers have been optimized for the transmission of time-domain excitation signals and the reception and processing of echo signals, respectively, thereby improving the stable and reliable operation of the entire ultrasonic thickness measurement system.

[0126] In one implementation, the analog filtering unit filters the mixing signal and is configured as follows: High-frequency components and DC leakage signals in the mixed signal are filtered out to obtain a low-frequency beat signal that contains only the thickness information of the object being measured.

[0127] In one implementation, the signal processing unit performs frequency domain analysis on the digital difference frequency signal and is configured to: The digital difference frequency signal is converted from a time domain signal to a frequency domain signal using the Fast Fourier Transform algorithm to obtain the frequency domain amplitude spectrum; Search for the maximum amplitude value in the frequency domain amplitude spectrum, and determine the frequency point corresponding to the maximum amplitude value as the measurement beat frequency; The target thickness of the object under test is calculated based on the measured beat frequency, the frequency modulation slope of the time-domain ultrasonic excitation signal, and the propagation speed of the ultrasonic wave in the object under test.

[0128] In one implementation, the signal processing unit calculates the target thickness of the object being measured, and is configured to: The target thickness of the object being measured is calculated using the following formula:

[0129] in, d Indicates thickness, c This indicates the speed of sound in which ultrasound waves propagate through the object being measured. f b Indicates the measured beat frequency. μ Indicates the frequency modulation slope. This indicates the pre-calibrated inherent system delay time.

[0130] Figure 1 and Figure 3 This is merely an example of an ultrasonic thickness measurement system and does not constitute a limitation on ultrasonic thickness measurement systems. An ultrasonic thickness measurement system may include more or fewer components than shown in the figure, or combine certain components, or use different components.

[0131] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0132] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0133] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0134] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0135] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for example, the division of units is merely a logical functional division, and there may be other division methods in actual implementation; for example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, and the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0136] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0137] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0138] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An ultrasonic thickness measurement system, characterized in that, include: The signal generating unit is configured to generate a discrete frequency modulated time-domain ultrasonic excitation signal; An ultrasonic transceiver unit, connected to the signal generating unit, is configured to: convert the time-domain ultrasonic excitation signal into ultrasonic waves and transmit them to the object under test; receive echo ultrasonic waves reflected from inside the object under test; and convert the echo ultrasonic waves into echo electrical signals. The analog mixing unit, which is connected to the signal generating unit and the ultrasonic transceiver unit respectively, is configured to: perform analog mixing of the echo electrical signal and the time-domain ultrasonic excitation signal, which is the local oscillator signal, to obtain a mixed signal; An analog filtering unit, connected to the analog mixing unit, is configured to: filter the mixing signal to remove high-frequency components from the mixing signal and obtain a low-frequency beat frequency signal containing thickness information of the object under test; An analog-to-digital conversion unit, connected to the analog filtering unit, is configured to sample the low-frequency beat frequency signal and convert it into a digital difference frequency signal. The signal processing unit, connected to the analog-to-digital conversion unit, is configured to perform frequency domain analysis on the digital difference frequency signal and calculate the target thickness of the object under test based on the analysis results.

2. The ultrasonic thickness measurement system according to claim 1, characterized in that, The ultrasonic thickness measurement system also includes a control unit connected to the signal generating unit; The control unit is configured to send a configuration command to the signal generating unit to configure the discrete frequency modulation parameters of the time-domain ultrasonic excitation signal, wherein the discrete frequency modulation parameters include a frequency step value and a dwell time at each frequency point. The signal generating unit generates a discrete frequency modulated time-domain ultrasonic excitation signal, configured as follows: In response to the configuration command, a time-domain ultrasonic excitation signal is generated in which the frequency exhibits discrete step changes on the time axis according to the frequency step value and the dwell time.

3. The ultrasonic thickness measurement system according to claim 2, characterized in that, The analog-to-digital conversion unit samples the low-frequency beat frequency signal and is configured as follows: The low-frequency beat frequency signal is sampled at a preset sampling frequency, wherein the preset sampling frequency is significantly lower than the center frequency of the time-domain ultrasonic excitation signal.

4. The ultrasonic thickness measurement system according to any one of claims 1-3, characterized in that, The signal processing unit performs frequency domain analysis on the digital difference frequency signal and is configured as follows: A window function is applied to the digital difference frequency signal for weighting to suppress spectral leakage, resulting in a weighted digital signal sequence. Using the Fast Fourier Transform algorithm, the weighted digital signal sequence is converted from a time-domain signal to a frequency-domain signal to obtain the frequency-domain amplitude spectrum; The target thickness of the object under test is calculated based on the frequency domain amplitude spectrum.

5. The ultrasonic thickness measurement system according to claim 4, characterized in that, The signal processing unit uses the Fast Fourier Transform algorithm to convert the weighted digital signal sequence from a time-domain signal to a frequency-domain signal, obtaining a frequency-domain amplitude spectrum, which is configured as follows: The weighted digital difference frequency signal sequence is zero-padded in the time domain to obtain a zero-padded digital difference frequency signal sequence. Perform a Fast Fourier Transform on the zero-padded digital difference frequency signal sequence to obtain the frequency domain amplitude spectrum.

6. The ultrasonic thickness measurement system according to any one of claims 1-3, characterized in that, The ultrasonic thickness measurement system further includes a first signal amplifier and / or a second signal amplifier; The first signal amplifier is connected to both the signal generating unit and the ultrasonic transceiver unit, and is configured as follows: The time-domain ultrasonic excitation signal is amplified by gain, and the amplified time-domain ultrasonic excitation signal is sent to the ultrasonic transceiver unit. The second signal amplifier is connected to both the analog filtering unit and the analog-to-digital conversion unit, and is configured as follows: The low-frequency beat signal is amplified and then sent to the analog-to-digital conversion unit.

7. The ultrasonic thickness measurement system according to claim 6, characterized in that, The analog filtering unit performs filtering processing on the mixing signal and is configured as follows: After filtering out the high-frequency components and DC leakage signals in the mixed signal, a low-frequency beat signal containing only the thickness information of the object under test is obtained.

8. The ultrasonic thickness measurement system according to any one of claims 1-3, characterized in that, The signal processing unit performs frequency domain analysis on the digital difference frequency signal and is configured as follows: The digital difference frequency signal is converted from a time domain signal to a frequency domain signal using the Fast Fourier Transform algorithm to obtain the frequency domain amplitude spectrum; Search for the maximum amplitude value in the frequency domain amplitude spectrum, and determine the frequency point corresponding to the maximum amplitude value as the measurement beat frequency; The target thickness of the object under test is calculated based on the measured beat frequency, the frequency modulation slope of the time-domain ultrasonic excitation signal, and the propagation speed of the ultrasonic wave in the object under test.

9. The ultrasonic thickness measurement system according to claim 8, characterized in that, The signal processing unit calculates the target thickness of the object under test and is configured as follows: The target thickness of the object being measured is calculated using the following formula: in, d Indicates the thickness, c This indicates the speed of sound in which ultrasound waves propagate through the object being measured. f b This indicates the measured beat frequency. μ This indicates the frequency modulation slope. This indicates the pre-calibrated inherent system delay time.

10. An ultrasonic thickness measurement method, characterized in that, The method, applied to the ultrasonic thickness measurement system as described in any one of claims 1-9, comprises: The signal generation unit generates a discrete frequency modulated time-domain ultrasonic excitation signal; The ultrasonic transceiver unit converts the time-domain ultrasonic excitation signal into ultrasonic waves and transmits them to the object under test. It also receives the echo ultrasonic waves reflected from inside the object under test and converts the echo ultrasonic waves into echo electrical signals. The analog mixing unit performs analog mixing of the echo electrical signal and the time-domain ultrasonic excitation signal, which serves as the local oscillator signal, to obtain a mixed signal; The analog filtering unit filters the mixed signal to remove high-frequency components and obtains a low-frequency beat signal containing the thickness information of the object under test. The analog-to-digital conversion unit samples the low-frequency beat frequency signal and converts it into a digital difference frequency signal; The signal processing unit performs frequency domain analysis on the digital difference frequency signal and calculates the target thickness of the object under test based on the analysis results.

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