A close-range millimeter wave radar displacement measurement system

Abstract

The application relates to the technical field of millimeter wave radar, in particular to a short-distance millimeter wave radar displacement measurement system. A first static echo signal and a dynamic echo signal are collected by a return signal collection module, a second static echo signal is constructed according to the first static echo signal and a direct current offset component in the first static echo signal by a correction parameter calculation module, and an amplitude imbalance parameter and a phase imbalance parameter are obtained according to the second static echo signal, so that high-precision imbalance parameter estimation under an arbitrary amplitude modulation condition is realized. Meanwhile, the dynamic echo signal is corrected according to the amplitude imbalance parameter, the phase imbalance parameter and the direct current offset component by a signal correction module, so that a corrected dynamic echo signal is obtained, the correction accuracy of the dynamic echo signal reflected by the measured object is significantly improved, and a displacement measurement result is obtained according to the corrected dynamic echo signal by a displacement measurement module, so that the accuracy and reliability of the displacement measurement result are further improved.

Description

Technical Field

[0001] This application relates to the field of millimeter-wave radar technology, and in particular to a short-range millimeter-wave radar displacement measurement system. Background Technology

[0002] Millimeter-wave radar displacement measurement technology is a high-precision, non-contact measurement method that uses electromagnetic wave signals in the millimeter-wave band to detect displacement changes of target objects. In practical applications, millimeter-wave radar systems typically use orthogonal radio transceivers to obtain the orthogonal amplitude components In-phase (I) and Quadrature (Q) of the echo signal. The displacement information of the target object can then be calculated by demodulating the I / Q signals.

[0003] However, due to limitations in hardware circuit performance, the I / Q signals may exhibit imbalances in amplitude and phase. This imbalance degrades signal quality, leading to signal distortion and severely impacting the measurement accuracy of millimeter-wave radar. Therefore, imbalance correction of the I / Q signals in the echo signal is necessary. Existing patent application CN113520344A provides a radar-based vital sign estimation method. It generates compensated I and Q signals associated with the detected target by performing elliptic fitting on in-phase and quadrature signals associated with the target, and determines the displacement signal based on these compensated I and Q signals. While this patent application employs an elliptic correction method to correct the I / Q signal imbalance, in close-range static measurements with millimeter-wave radar, the echo signal tends to exhibit strong amplitude modulation, causing its I / Q trajectory to transform from an ellipse to a tapered ellipse. This renders the elliptic correction method ineffective, thereby reducing the accuracy of displacement measurement. Summary of the Invention

[0004] Therefore, it is necessary to provide a short-range millimeter-wave radar displacement measurement system to address the problem that existing I / Q signal imbalance correction methods are not ideal and result in inaccurate displacement measurement results.

[0005] This application provides a short-range millimeter-wave radar displacement measurement system. The system includes an echo signal acquisition module, a correction parameter calculation module, a signal correction module, and a displacement measurement module. The first end of the echo signal acquisition module is connected to the first end of the correction parameter calculation module, the second end of the correction parameter calculation module is connected to the second end of the signal correction module, the second end of the echo signal acquisition module is connected to the first end of the signal correction module, and the third end of the signal correction module is connected to the displacement measurement module.

[0006] The echo signal acquisition module is used to acquire the first static echo signal and the dynamic echo signal;

[0007] The correction parameter calculation module is used to construct a second static echo signal based on the first static echo signal and the DC offset component in the first static echo signal, and to obtain amplitude imbalance parameters and phase imbalance parameters based on the second static echo signal; wherein, the second static echo signal includes a second static echo I signal and a second static echo Q signal, and the expression for the second static echo I signal is:

[0008]

[0009] In the formula, This is the second static echo I signal. This is the first static echo I signal. The first static echo Q signal, This refers to the DC offset component of the first static echo Q signal. This refers to the DC offset component of the first static echo I signal. To express differentiation;

[0010] The expression for the second static echo Q signal is:

[0011]

[0012] In the formula, This is the second static echo Q signal;

[0013] The signal correction module is used to correct the dynamic echo signal according to the amplitude imbalance parameter, the phase imbalance parameter and the DC offset component to obtain the corrected dynamic echo signal.

[0014] The displacement measurement module is used to obtain displacement measurement results based on the corrected dynamic echo signal.

[0015] Furthermore, the correction parameter calculation module includes a formula-based unbalance parameter calculation unit; the formula-based unbalance parameter calculation unit calculates the unbalance parameter according to the formula...

[0016]

[0017] Calculate the amplitude imbalance parameter In the formula, This represents the average value of the second static echo I signal within its period. This represents the average value of the second static echo Q signal within its period;

[0018] According to the formula

[0019]

[0020] Calculate the phase imbalance parameters In the formula, , For a fixed rate of change of distance between the millimeter-wave radar and the object being measured, This refers to the wavelength of millimeter-wave radar.

[0021] Furthermore, the correction parameter calculation module includes an elliptic parameter estimation unit and a first unbalanced parameter calculation unit connected to the elliptic parameter estimation unit;

[0022] The ellipse parameter estimation unit is used to obtain ellipse parameters based on the implicit equation of the oblique ellipse and the second static echo signal; the implicit equation of the oblique ellipse is:

[0023]

[0024] In the formula, Let be the unknown parameters of the implicit equation of the oblique ellipse; the matrix expression of the implicit equation of the oblique ellipse is:

[0025]

[0026] In the formula, The number of sample points. , ;

[0027] The ellipse parameters The expression is:

[0028]

[0029] In the formula, , For matrix symmetric matrix;

[0030] The first imbalance parameter calculation unit is used to calculate the amplitude imbalance parameter and the phase imbalance parameter based on the elliptic parameters; wherein, the expression for the amplitude imbalance parameter is:

[0031]

[0032] In the formula, The amplitude imbalance parameter;

[0033] The expression for the phase imbalance parameter is:

[0034]

[0035] In the formula, The phase imbalance parameter is denoted as .

[0036] Furthermore, the direction of the phase imbalance parameter is positive when the coefficient of determination is greater than 1 and negative when it is less than 1; wherein, when the phase imbalance parameter and When, the determination coefficient The expression is:

[0037]

[0038] In the formula, , , , , , The signal period of the first static echo signal is given. This is the first static echo I signal. This is the first static echo Q signal.

[0039] Furthermore, the correction parameter calculation module includes a complex signal construction unit and a second imbalance parameter calculation unit;

[0040] The complex signal construction unit is used to construct a complex signal based on the second static echo signal, and to perform an Euler transform on the complex signal; the expression of the complex signal is:

[0041]

[0042] The expression for the complex signal after Euler transform is:

[0043]

[0044] In the formula, , , , The frequency of the first static echo signal;

[0045] The second unbalance parameter calculation unit is used to calculate the unbalance parameter based on the complex signal after Euler transformation in the frequency spectrum. as well as The amplitude information at a given location is used to obtain the amplitude imbalance parameter and the phase imbalance parameter through a mathematical relationship; the expression for the mathematical relationship is:

[0046]

[0047] In the formula, Represents the real part of the signal. Represents the imaginary part of the signal. This indicates that the complex signal after the Euler transform is in The amplitude at that point, The conjugate signal of the complex signal after the Euler transform is represented in... The amplitude at that point, Indicates intermediate frequency signal;

[0048] The amplitude imbalance parameter The expression is:

[0049]

[0050] The phase imbalance parameter The expression is:

[0051]

[0052] In the formula, The four quadrants are the original and reverse tangents.

[0053] Furthermore, the expression for the corrected dynamic echo signal is:

[0054]

[0055] In the formula, The corrected dynamic echo I signal, The dynamic echo I signal before correction. The corrected dynamic echo Q signal, The dynamic echo Q signal before correction. The amplitude imbalance parameter is... The phase imbalance parameter is denoted as .

[0056] Furthermore, the echo signal acquisition module includes a signal preprocessing unit, which is connected to the signal correction module;

[0057] The signal preprocessing unit is used to denoise the dynamic echo signal; wherein the denoising method includes at least one of the following: finite-length unit impulse response low-pass filter, wavelet decomposition denoising, and low-frequency component in maximal discrete wavelet transform.

[0058] Furthermore, the displacement measurement module includes an arctangent demodulation unit, which is connected to the signal correction module;

[0059] The arctangent demodulation unit is used to perform arctangent demodulation on the corrected dynamic echo signal to obtain the displacement measurement result; the expression for the displacement measurement result is:

[0060]

[0061] In the formula, This represents the displacement measurement result at time t. The corrected dynamic echo I signal, This is the corrected dynamic echo Q signal.

[0062] Furthermore, the displacement measurement module includes a long displacement measurement unit, which is connected to the signal correction module;

[0063] The long displacement measurement unit is used to obtain the displacement measurement result by employing a translation phase angle algorithm when the displacement information change is greater than half the wavelength measurement range; the expression for the displacement measurement result is:

[0064]

[0065] In the formula, This represents the displacement measurement result at time t. The corrected dynamic echo I signal, This is the corrected dynamic echo Q signal.

[0066] Furthermore, the period of the first static echo signal for:

[0067]

[0068] In the formula, For a fixed rate of change of distance between the millimeter-wave radar and the object being measured, For millimeter-wave radar wavelength, The frequency of the first static echo signal is denoted as .

[0069] The aforementioned short-range millimeter-wave radar displacement measurement system acquires first static echo signals and dynamic echo signals through an echo signal acquisition module. A correction parameter calculation module constructs a second static echo signal based on the first static echo signal and its DC offset component. Based on the second static echo signal, amplitude imbalance parameters and phase imbalance parameters are obtained, achieving high-precision imbalance parameter estimation under arbitrary amplitude modulation conditions. Simultaneously, a signal correction module corrects the dynamic echo signal based on the amplitude imbalance parameters, phase imbalance parameters, and the DC offset component, obtaining a corrected dynamic echo signal. This significantly improves the correction accuracy of the dynamic echo signal reflected from the measured object. Finally, a displacement measurement module obtains the displacement measurement result based on the corrected dynamic echo signal, further enhancing the accuracy and reliability of the displacement measurement results. Attached Figure Description

[0070] Figure 1 This is a schematic diagram of a short-range millimeter-wave radar displacement measurement system in one embodiment;

[0071] Figure 2This is a schematic diagram of the structure of a near-range millimeter-wave radar displacement measurement system in another embodiment;

[0072] Figure 3 (a) is a schematic diagram of the ideal displacement change of a millimeter-wave radar in one embodiment;

[0073] Figure 3 (b) is a time-domain waveform of the dynamic echo signal in one embodiment;

[0074] Figure 4 (a) is a time-domain waveform of the first static echo signal in one embodiment;

[0075] Figure 4 (b) is a trajectory diagram of the first static echo signal in one embodiment;

[0076] Figure 5 (a) is a trajectory diagram of the second static echo signal in one embodiment;

[0077] Figure 5 (b) is a spectrum diagram of a complex signal in one embodiment;

[0078] Figure 6 (a) is a time-domain waveform of the corrected dynamic echo signal in one embodiment;

[0079] Figure 6 (b) is a schematic diagram of displacement measurement results obtained by using the arctangent demodulation method in one embodiment;

[0080] Figure 6 (c) is a schematic diagram of the displacement measurement results obtained by the translation phase angle algorithm in one embodiment;

[0081] Figure 6 (d) is a schematic diagram of the displacement measurement error obtained by the translation phase angle algorithm in one embodiment;

[0082] Figure 7 The following is a time-domain waveform diagram of the dynamic echo signal in another embodiment;

[0083] Figure 8 (a) is a time-domain waveform of the first static echo signal in another embodiment;

[0084] Figure 8 (b) is a trajectory diagram of the first static echo signal in another embodiment;

[0085] Figure 9 (a) is a time-domain waveform diagram of the second static echo signal in another embodiment;

[0086] Figure 9 (b) is a spectrum diagram of a complex signal in another embodiment;

[0087] Figure 10 The time-domain waveform of the corrected dynamic echo signal is shown in another embodiment.

[0088] Figure 11 This is a schematic diagram of displacement measurement results obtained using the arctangent demodulation method in another embodiment;

[0089] Figure 12 (a) is a schematic diagram of displacement measurement results using millimeter-wave radar sensing for blade tip clearance measurement in one embodiment;

[0090] Figure 12 (b) is a schematic diagram of the displacement measurement results of blade tip clearance measurement using a laser displacement sensor in one embodiment.

[0091] The reference numerals are as follows: 100 Echo signal acquisition module; 200 Correction parameter calculation module; 300 Signal correction module; 400 Displacement measurement module. Detailed Implementation

[0092] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0093] Example 1

[0094] like Figure 1 As shown, this embodiment provides a short-range millimeter-wave radar displacement measurement system, including an echo signal acquisition module, a correction parameter calculation module, a signal correction module, and a displacement measurement module. The first end of the echo signal acquisition module is connected to the first end of the correction parameter calculation module, the second end of the correction parameter calculation module is connected to the second end of the signal correction module, the second end of the echo signal acquisition module is connected to the first end of the signal correction module, and the third end of the signal correction module is connected to the displacement measurement module.

[0095] The echo signal acquisition module is used to acquire the first static echo signal and the dynamic echo signal.

[0096] The first static echo signal refers to the echo signal generated when the distance between the millimeter-wave radar sensor and the object being measured changes at a fixed rate. This distance change can occur in two ways: first, the object being measured is stationary, while the millimeter-wave radar sensor moves away from or towards the object at a fixed speed; second, the millimeter-wave radar sensor is stationary, while the object being measured moves away from or towards the sensor at a fixed speed. Furthermore, the first static echo signal includes the first static echo I signal. and the first static echo Q signal The first static echo I signal is the orthogonal amplitude component I channel signal of the first static echo signal, and the first static echo Q signal is the orthogonal amplitude component Q channel signal of the first static echo signal.

[0097] The dynamic echo signal is the orthogonal amplitude components I and Q of the echo signal from the object being measured at close range, as measured by a millimeter-wave radar at its initial position. The millimeter-wave radar operates at frequencies from 24 GHz to 240 GHz, with a close range of (0, 10λ], where λ is the wavelength of the millimeter-wave radar. For example, when the frequency of the millimeter-wave radar is 120 GHz, the close range is (0, 25] mm. The object being measured is a surface capable of reflecting millimeter waves, such as metal.

[0098] Specifically, such as Figure 2 As shown, the echo signal acquisition module may include a static echo signal acquisition unit for acquiring a first static echo signal and a dynamic echo signal acquisition unit for acquiring dynamic echo signals. Further, the echo signal acquisition module may also include a signal preprocessing unit, with its first end connected to the dynamic echo signal acquisition unit and its second end connected to the first end of the signal correction module. The signal preprocessing unit is used to denoise the dynamic echo signal. The denoising methods may include, but are not limited to, using a finite impulse response (FIR) low-pass filter, wavelet decomposition denoising, and low-frequency components in maximal discrete wavelet transform.

[0099] The correction parameter calculation module is used to construct a second static echo signal based on the first static echo signal and the DC offset component in the first static echo signal. The second static echo signal includes a second static echo I signal. Second static echo Q signal The second static echo I signal is the orthogonal amplitude component I signal of the second static echo signal, and the second static echo Q signal is the orthogonal amplitude component Q signal of the second static echo signal. The expression for the second static echo I signal is:

[0100] (1)

[0101] In the formula, This is the second static echo I signal. This is the first static echo I signal. The first static echo Q signal, This is the DC offset component of the first static echo Q signal. This refers to the DC offset component of the first static echo I signal. This indicates differentiation.

[0102] The expression for the second static echo Q signal is:

[0103] (2)

[0104] In the formula, This is the second static echo Q signal.

[0105] Specifically, such as Figure 2 As shown, the correction parameter calculation module may include a DC offset component calculation unit and a ratio differential signal construction unit. The first end of the static echo signal acquisition unit is connected to the first end of the DC offset component calculation unit, the second end of the DC offset component calculation unit is connected to the first end of the ratio differential signal construction unit, the second end of the static echo signal acquisition unit is connected to the second end of the ratio differential signal construction unit, and the third end of the DC offset component calculation unit is connected to the third end of the signal correction module.

[0106] The DC offset component calculation unit is used to obtain the DC offset component in the first static echo signal. The DC offset component in the first static echo signal includes the DC offset component of the first static echo I signal. DC offset component of the first static echo Q signal Specifically, methods for obtaining the DC offset component may include, but are not limited to, directly obtaining the DC offset component by calculating the average value of the first static echo signal over a complete period; indirectly obtaining the DC offset component by estimating and removing the AC component through the difference between adjacent data points using signal differential techniques; directly extracting the component with a frequency of 0 from the spectrum of the first static echo signal; and using an FIR ultra-low-pass filter to preprocess the first static echo signal to remove high-frequency noise before calculating the average value over the signal period to obtain a more accurate DC offset component. The signal period of the first static echo signal is shown in equation (3):

[0107] (3)

[0108] In the formula, For a fixed rate of change of distance between the millimeter-wave radar and the object being measured, For millimeter-wave radar wavelength, Let be the frequency of the first static echo signal. Specifically, when using an FIR ultra-low-pass filter to denoise the first static echo signal, its cutoff frequency is located at (0, ). Between 100 Hz and 100 Hz.

[0109] The ratio differential signal construction unit is used to construct the second static echo signal based on the first static echo I signal and the first static echo Q signal after removing the DC offset component, by adopting the ratio, differential and reciprocal method. It can be understood that the second static echo signal includes the second static echo I signal as shown in equation (1) and the second static echo Q signal as shown in equation (2).

[0110] The correction parameter calculation module is also used to obtain amplitude imbalance parameters and phase imbalance parameters based on the second static echo signal. Specifically, such as... Figure 2 As shown, the correction parameter calculation module also includes a formula-based unbalance parameter calculation unit. The first end of the formula-based unbalance parameter calculation unit is connected to the third end of the ratio differential signal construction unit, and the second end is connected to the third end of the signal correction module. The formula-based unbalance parameter calculation unit calculates the amplitude unbalance parameter according to the formula shown in equation (4). The unbalance parameters are calculated according to the formula shown in equation (5). :

[0111] (4)

[0112] In the formula, This represents the average value of the second static echo I signal over one period. This represents the average value of the second static echo Q signal over one period.

[0113] (5)

[0114] In the formula, , For a fixed rate of change of distance between the millimeter-wave radar and the object being measured, This refers to the wavelength of millimeter-wave radar.

[0115] Furthermore, such as Figure 2 As shown, the correction parameter calculation module may further include an elliptic parameter estimation unit and a first imbalance parameter calculation unit. The first end of the elliptic parameter estimation unit is connected to the third end of the ratio difference signal construction unit, and the second end is connected to the first end of the first imbalance parameter calculation unit. The second end of the first imbalance parameter calculation unit is connected to the third end of the signal correction module.

[0116] The ellipse parameter estimation unit is used to obtain the ellipse parameters based on the implicit equation of the oblique ellipse and the second static echo signal. Specifically, the ellipse parameter estimation unit fits the center of the ellipse to the second static echo signal based on the implicit equation of the oblique ellipse to estimate the ellipse parameters. The implicit equation of the oblique ellipse is:

[0117] (6)

[0118] In the formula, Let be the unknown parameters of the implicit equation of the oblique ellipse. From equation (6), we can see that the number of unknowns in the implicit equation of the oblique ellipse is 5, and the number of independent equations is n.

[0119] The matrix expression for the implicit equation of an oblique ellipse is:

[0120] (7)

[0121] In the formula, The number of sample points. , .

[0122] When the number of independent equations exceeds the number of unknowns in the implicit equation of the oblique ellipse, the optimal solution of equation (7) is:

[0123] (8)

[0124] In the formula, Representation matrix The generalized inverse of MP is given by . Here, is a column-rank matrix, and its generalized inverse is calculated using the formula for a column-rank matrix. The ellipse parameters can be obtained. The expression is:

[0125] (9)

[0126] In the formula, , For matrix A symmetric matrix.

[0127] The first unbalance parameter calculation unit is used to calculate the amplitude unbalance parameter and the phase unbalance parameter based on the elliptic parameter. Specifically, based on the elliptic parameter shown in equation (9), the amplitude unbalance parameter shown in equation (10) and the phase unbalance parameter shown in equation (11) can be calculated:

[0128] (10)

[0129] In the formula, This is the amplitude imbalance parameter.

[0130] (11)

[0131] In the formula, This is the phase imbalance parameter.

[0132] Furthermore, the directions of the phase imbalance parameters calculated by the unbalance parameter calculation unit as shown in equation (5) and the phase imbalance parameters calculated by the first unbalance parameter calculation unit as shown in equation (11) can be determined by the determination coefficient shown in equation (12).

[0133] When the phase imbalance parameter and When, the coefficient of determination The expression is:

[0134] (12)

[0135] In the formula, , , , , , The signal period of the first static echo signal. This is the first static echo I signal. This is the first static echo Q signal.

[0136] Specifically, the unbalanced parameter unit, as shown in equation (4), substitutes the amplitude unbalanced parameter and the first static echo signal into equation (12) to calculate the determination coefficient. When the determination coefficient is greater than or equal to 1, the direction of the phase unbalanced parameter shown in equation (5) is positive, that is... When the coefficient of determination is less than 1, the direction of the phase imbalance parameter shown in equation (5) is negative, that is... Similarly, the first imbalance parameter calculation unit substitutes the amplitude imbalance parameter shown in equation (10) and the first static echo signal into equation (12) to calculate the determination coefficient. When the determination coefficient is greater than or equal to 1, the direction of the phase imbalance parameter shown in equation (11) is positive, that is... When the coefficient of determination is less than 1, the direction of the phase imbalance parameter shown in equation (11) is negative, that is... .

[0137] Based on the coefficient of determination The validity of using the sign of the phase imbalance parameter to determine its sign is proven as follows:

[0138] when When, the coefficient of determination The expression is shown in equation (13):

[0139] (13)

[0140] because ,therefore .

[0141] when When, the coefficient of determination The expression is shown in equation (14):

[0142] (14)

[0143] because ,therefore .

[0144] In addition, such as Figure 2 As shown, the correction parameter calculation module may further include a complex signal construction unit and a second unbalanced parameter calculation unit. The first end of the complex signal construction unit is connected to the third end of the ratio difference signal construction unit, and the second end is connected to the first end of the second unbalanced parameter calculation unit. The second end of the second unbalanced parameter calculation unit is connected to the third end of the signal correction module.

[0145] The complex signal construction unit is used to construct a complex signal based on the second static echo signal and perform an Euler transform on the complex signal. The expression for the constructed complex signal is:

[0146] (15)

[0147] The expression for the complex signal after Euler transform is:

[0148] (16)

[0149] In the formula, , , , The first static echo signal ( and The frequency of the complex signal. From equation (18), it can be seen that the complex signal... A DC component also exists at [location 1] and [location 2]. , main frequency and mirror frequency Element.

[0150] The second unbalance parameter calculation unit is used to calculate the complex signal after Euler transformation. In the spectrum, 0, as well as The amplitude information at a given point is mathematically related to the amplitude imbalance parameter and the phase imbalance parameter to obtain the amplitude imbalance parameter and phase imbalance parameter. Among these, in the spectrum, 0, as well as The mathematical relationship between the amplitude information and the amplitude imbalance parameter and phase imbalance parameter at a given point is as follows:

[0151] (17)

[0152] In the formula, Represents the real part of the signal. Represents the imaginary part of the signal. This indicates that the complex signal after Euler transformation is in The amplitude at that point, The conjugate signal of the complex signal after Euler transform is represented in The amplitude at that point, The intermediate frequency (IF) is defined in a preferred embodiment as the frequency of the first static echo signal. equal.

[0153] Then, the amplitude imbalance parameter can be obtained from the mathematical relationship shown in equation (17). The expression is:

[0154] (18)

[0155] Phase imbalance parameters The expression is:

[0156] (19)

[0157] In the formula, The four quadrants are the original and reverse tangents.

[0158] Compared to the phase imbalance parameters calculated by the formula-based unbalance parameter calculation unit and the first unbalance parameter calculation unit, the phase imbalance parameters obtained by the second unbalance parameter calculation unit can directly yield the phase direction without calculating the determination coefficient, further improving the efficiency of signal correction.

[0159] The signal correction module corrects the dynamic echo signal based on amplitude imbalance parameters, phase imbalance parameters, and DC offset components to obtain the corrected dynamic echo signal. Optionally, the signal correction module can obtain the amplitude imbalance parameters and phase imbalance parameters from the formula-based imbalance parameter calculation unit, the first imbalance parameter calculation unit, or the second imbalance parameter calculation unit. To improve the accuracy and reliability of the parameters, the signal correction module can also integrate the amplitude imbalance parameters and phase imbalance parameters calculated by the formula-based imbalance parameter calculation unit, the first imbalance parameter calculation unit, and the second imbalance parameter calculation unit. For example, the final amplitude imbalance parameters and phase imbalance parameters can be determined by averaging or performing other statistical processing on the amplitude imbalance parameters and phase imbalance parameters provided by these units. The calculation formula for the corrected dynamic echo signal is:

[0160] (20)

[0161] In the formula, The corrected dynamic echo I signal, The dynamic echo I signal before correction. The corrected dynamic echo Q signal, The dynamic echo Q signal before correction. Further, the dynamic echo I signal before correction. The dynamic echo Q signal before correction Both can be signals that have been denoised by the signal preprocessing unit, in order to further improve the reliability of the correction results.

[0162] The displacement measurement module is used to obtain displacement measurement results based on the corrected dynamic echo signal. The corrected dynamic echo signal includes a corrected dynamic echo I signal and a corrected dynamic echo Q signal. Specifically, as shown... Figure 2 As shown, the displacement measurement module may include an arctangent demodulation unit, which is connected to the signal correction module. The arctangent demodulation unit is used to perform arctangent demodulation on the corrected dynamic echo signal to obtain the displacement measurement result. The expression for the displacement measurement result is:

[0163] (twenty one)

[0164] In the formula, This represents the displacement measurement result at time t.

[0165] Furthermore, when the displacement of the object being measured is large, exceeding half the wavelength, in order to improve the accuracy of the displacement measurement results, in some embodiments, such as... Figure 2 As shown, the displacement measurement module may further include a long displacement measurement unit, which is connected to the signal correction module. The long displacement measurement unit is used to obtain the displacement measurement result using a translation phase angle algorithm when the displacement information change is greater than half the wavelength measurement range. The translation phase angle algorithm calculates the displacement by measuring the change in phase angle, maintaining high measurement accuracy over a large displacement range. Displacement measurement results. The expression is:

[0166] (twenty two)

[0167] Finally, the short-range millimeter-wave radar displacement measurement system provided in this embodiment can be used in the field of industrial automation for product quality control on production lines and position monitoring of equipment such as robotic arms and conveyor belts, ensuring high efficiency and quality in production. At the same time, in the aerospace field, it can be widely used for blade tip clearance measurement, online vibration monitoring, and position detection of key components such as landing gear, providing solid technical support for flight safety and efficiency.

[0168] For example, the echo signal acquisition module in this embodiment can be a 24GHz millimeter-wave radar module (such as HLK-LD112, HLK-LD303, etc.). This module can receive reflected echo signals, including the first static echo signal and dynamic echo signal in this embodiment. It features high sensitivity, low power consumption, and strong anti-interference capabilities, making it suitable for short-range displacement measurement. For applications requiring higher frequencies and more accurate measurements, a higher frequency millimeter-wave radar module can also be selected. The calibration parameter calculation module can be an embedded processor or microcontroller (such as STM32, etc.), which includes a memory and a processor. The memory stores computer programs. When the processor executes these programs, it constructs a second static echo signal based on the first static echo signal and the DC offset component in the first static echo signal, and obtains the amplitude imbalance parameter and phase imbalance parameter based on the second static echo signal. The signal correction module and displacement measurement module can be digital signal processing chips (such as DSP chips) or FPGAs (Field Programmable Gate Arrays). They include memory and processors. The memory stores computer programs. When the processor executes these programs, it corrects the dynamic echo signal according to the amplitude imbalance parameter, phase imbalance parameter and DC offset component to obtain the corrected dynamic echo signal. The displacement measurement result is obtained from the corrected dynamic echo signal.

[0169] The short-range millimeter-wave radar displacement measurement system of this embodiment acquires a first static echo signal and a dynamic echo signal through an echo signal acquisition module. A correction parameter calculation module constructs a second static echo signal based on the first static echo signal and the DC offset component in the first static echo signal, and obtains amplitude imbalance parameters and phase imbalance parameters based on the second static echo signal, realizing high-precision imbalance parameter estimation under arbitrary amplitude modulation conditions. At the same time, the signal correction module corrects the dynamic echo signal based on the amplitude imbalance parameters, phase imbalance parameters, and DC offset component to obtain a corrected dynamic echo signal, which significantly improves the correction accuracy of the dynamic echo signal reflected by the measured object. Then, the displacement measurement module obtains the displacement measurement result based on the corrected dynamic echo signal, further improving the accuracy and reliability of the displacement measurement result.

[0170] Example 2

[0171] To better understand the short-range millimeter-wave radar displacement measurement system in Example 1, the following explanation is provided in conjunction with specific simulation experiments. It should be noted that the method used in this example to calculate the amplitude imbalance parameters and phase imbalance parameters using formulas in the short-range millimeter-wave radar displacement measurement system is called RD-EQ; the method using elliptic equation fitting to calculate the amplitude imbalance parameters and phase imbalance parameters is called RD-EC; and the method using the complex signal spectrum to calculate the amplitude imbalance parameters and phase imbalance parameters is called RD-S. The specific process is as follows:

[0172] 1. Record the dynamic echo I signal acquired by the dynamic echo signal acquisition unit. and dynamic echo Q signal The simulation signal models are as follows:

[0173] (twenty three)

[0174] (twenty four)

[0175] In the formula, For I / Q signal amplitude factor, Indicates phase change, , To obtain the displacement change, This indicates that the signal-to-noise ratio is increased by . White Gaussian noise, For amplitude imbalance parameters, For phase imbalance parameters, The DC offset component of the dynamic echo I signal. This refers to the DC offset component of the dynamic echo Q signal. Specifically, in this embodiment, , dB , , rad, V, V. At this point, the displacement change to be obtained like Figure 3 As shown in (a). Further, a 5-level maximal discrete wavelet packet transform is employed, using the first wavelet packet component from the 5th level decomposition to denoise the dynamic echo I and dynamic echo Q signals respectively. The time-domain waveforms of the denoised dynamic echo I and dynamic echo Q signals are shown in Figure 1. Figure 3 As shown in (b). It is understandable that... Figure 3 The I signal in (b) is the denoised dynamic echo I signal. Figure 3 The Q signal in (b) is the denoised dynamic echo Q signal.

[0176] 2. Record the first static echo I signal acquired by the static echo signal acquisition unit. and the first static echo Q signal The simulation signal models are as follows:

[0177] (25)

[0178] (26)

[0179] In the formula, It can be any amplitude modulation term. In this embodiment, , This represents the initial distance between the millimeter-wave radar sensor and the object being measured. At the moving speed... mm / s, mm, dB conditions, , rad, V, V, s.

[0180] The time-domain waveforms of the first static echo I signal and the first static echo Q signal at this time are as follows: Figure 4 As shown in (a), the trajectory diagram is as follows: Figure 4 As shown in (b). It is understandable that... Figure 4 (a) and Figure 4 The I signal in (b) is the first static echo I signal. Figure 4 (a) and Figure 4 The Q signal in (b) is the first static echo Q signal. Further, this embodiment uses a cutoff frequency of 0.2. After filtering the first static echo I signal and the first static echo Q signal with the FIR ultra-low-pass filter, the signal mean within one period is calculated to obtain the DC offset component in equations (25) and (26). Specifically, at the sampling frequency Under the condition of Hz, the calculated result of the DC offset component is as follows: , .

[0181] 3. Remove the DC offset component from the first static echo I signal and the first static echo Q signal, and then construct the second static echo I signal as shown in equation (27) and the second static echo Q signal as shown in equation (28) by taking the ratio, difference and reciprocal of the two signals:

[0182] (27)

[0183] (28)

[0184] In the formula, For the differentiation process, the corresponding discrete I / Q signals are differential processes. Figure 5 (a) is a signal trajectory diagram of the second static echo I signal and the second static echo Q signal. Figure 5 (b) is the complex signal spectrum of the second static echo I signal and the second static echo Q signal. It can be understood that... Figure 5 In (a), the In- signal is the second static echo I signal, and the Qn- signal is the second static echo Q signal. Further, by simplifying equations (27) and (28), we can obtain the second static echo I signal as shown in equation (29) and the second static echo Q signal as shown in equation (30):

[0185] (29)

[0186] (30)

[0187] In the formula, , For a fixed rate of change of distance between the millimeter-wave radar and the object being measured, This refers to the wavelength of millimeter-wave radar.

[0188] 4. Based on the first static echo I signal and the first static echo Q signal, the amplitude imbalance parameters and phase imbalance parameters are solved using the RD-EQ, RD-EC, and RD-S methods, respectively. To demonstrate the accuracy of the displacement measurement in this application, a comparative simulation experiment was conducted with existing I / Q signal imbalance correction methods, including the Gram-Schmidt Orthogonalization Procedure (GSOP), Ellipse Correction (EC), and spectral correction methods. Table 1 shows the imbalance parameter estimation errors of existing I / Q signal imbalance correction methods and the RD-EQ, RD-EC, and RD-S methods. As can be seen from Table 1, the imbalance parameter estimation errors of the RD-series methods in this embodiment are smaller than those obtained by existing I / Q signal imbalance correction methods, providing more accurate imbalance parameters for subsequent correction of dynamic echo signals.

[0189] Table 1

[0190]

[0191] 5. Correction is performed based on the amplitude imbalance parameters and phase imbalance parameters obtained in step 4, as well as the denoised dynamic echo I signal and dynamic echo Q signal. This embodiment uses the amplitude imbalance parameters and phase imbalance parameters calculated using the RD-EC method as an example for correction, resulting in the following... Figure 6 (a) shows the time-domain waveforms of the corrected dynamic echo I and dynamic echo Q signals. It can be understood that... Figure 6 In (a), the I signal is the corrected dynamic echo I signal, and the Q signal is the corrected dynamic echo Q signal.

[0192] 6. Perform arctangent demodulation on the corrected dynamic echo I signal and dynamic echo Q signal obtained in step 5 to obtain the following: Figure 6 (b) shows the displacement measurement results. Furthermore, when the displacement information change is greater than the half-wavelength measurement range, long displacements can be measured using a translation phase angle algorithm. This embodiment... Figure 6 (a) The corrected dynamic echo I signal and dynamic echo Q signal, after being processed using a phase angle shifting algorithm, yielded the following result: Figure 6 (c) shows the displacement measurement results, which are compared with the actual displacement. Figure 6 (c) shows that after mean alignment, the average measurement error of the ideal displacement change is 0.0966 μm, the root mean square error is 0.1044 μm, and the maximum error is 0.3810 μm. The specific demodulated displacement measurement error is as follows: Figure 6 As shown in (d).

[0193] Example 3

[0194] This embodiment uses millimeter-wave radar to measure blade tip clearance as an application scenario to further verify the effectiveness and practicality of this application.

[0195] In this embodiment, the object under test is a rectangular metal blade with a diameter of 140 mm and a thickness of 3 mm. The motor speed of the rectangular metal blade is 100 RPM, and the sampling frequency of the millimeter-wave radar sensor is up to 100 kHz. Specifically, in this embodiment, the dynamic echo signal generated by the rectangular metal blade is recorded as the blade tip gap echo signal. Figure 7 This is the time-domain waveform of the blade tip gap echo signal acquired by the echo signal acquisition module after denoising. Figure 7 The I signal in the figure refers to the blade tip gap echo I signal. Figure 7 The Q signal in this example refers to the blade tip gap echo Q signal. In this example, a 5-level maxima discrete wavelet packet transform is used, taking the first wavelet packet component from the 5th level decomposition to denoise the blade tip gap echo signal. Specifically, in this embodiment, the object under test is stationary, and the initial position of the millimeter-wave radar sensor distance from the blade tip surface... The sample size is 5 mm, and the sampling frequency is [missing information]. kHz, millimeter-wave radar sensing at a fixed moving speed The distance from the object being measured is mm / s. After the millimeter-wave radar sensor moves continuously for 20 mm, the time-domain waveforms of the first static echo I signal and the first static echo Q signal acquired by the echo signal acquisition module are as follows: Figure 8 As shown in (a), the signal trajectory diagram is as follows: Figure 8 As shown in (b). Subsequently, in this embodiment, an FIR ultra-low-pass filter with a cutoff frequency of 0.3744 Hz is used to filter the first static echo I signal and the first static echo Q signal, and at the sampling frequency... Under the condition of Hz, the calculated result of the DC offset component of the static echo signal is as follows: V, V.

[0196] Then, the second static echo I signal is constructed according to equation (1), and the second static echo Q signal is constructed according to equation (2). Figure 9 (a) shows the time-domain waveforms of the second static echo I signal and the second static echo Q signal. Figure 9 (b) shows the spectrum of the complex signal constructed based on equation (17). Then, the amplitude imbalance parameter and phase imbalance parameter are calculated using the same method as in Example 2. Table 2 shows the calculation results of the DC offset component and the imbalance parameter estimation error of the existing I / Q signal imbalance correction method compared with the RD-EQ, RD-EC and RD-S methods.

[0197] Table 2

[0198]

[0199] Next, the denoised blade tip gap echo signal is corrected based on the DC offset component, amplitude imbalance parameter, and phase imbalance parameter calculated in Table 2. Table 2 also shows the root mean square error of demodulation displacement corresponding to each correction method. By observing Table 2, it can be intuitively seen that the RD-series correction method proposed in this application is superior to existing correction methods in terms of imbalance parameter estimation error and demodulation displacement root mean square error, exhibiting lower error values.

[0200] The time-domain waveform of the corrected blade tip gap echo signal is shown below. Figure 10 As shown. Finally, the corrected blade tip clearance echo signal was demodulated using arctangent demodulation, and the resulting displacement measurement results are shown below. Figure 11 As shown in the figure. This figure also visually illustrates the correspondence between the arctangent demodulation region and the blade tip clearance region. However, observing... Figure 11It can be observed that the blade tip gap region in the dynamic echo signal is interfered with by the non-blade tip portion, causing the direct application of the phase angle translation algorithm to fail. Therefore, this embodiment combines existing signal amplitude localization technology to accurately locate the blade tip gap region and extracts the gap information through abrupt changes in phase information. The extracted blade tip gap region is shown below. Figure 12 As shown in (a), the measurement results of the laser displacement sensor in comparison are as follows: Figure 12 As shown in (b). Within the measurement range of relative change in blade tip clearance of 300 μm, this embodiment uses the following... Figure 12 (b) shows the measurement results of the laser displacement sensor as a benchmark for comparison. The average measurement error of the millimeter-wave radar sensor is 2.23 μm and the maximum error is 4.92 μm. This data fully verifies the effectiveness and high precision of the RD-series correction method proposed in this application.

[0201] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0202] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A close-range millimeter-wave radar displacement measurement system, characterized by, The system includes an echo signal acquisition module, a correction parameter calculation module, a signal correction module, and a displacement measurement module. The first end of the echo signal acquisition module is connected to the first end of the correction parameter calculation module, the second end of the correction parameter calculation module is connected to the second end of the signal correction module, the second end of the echo signal acquisition module is connected to the first end of the signal correction module, and the third end of the signal correction module is connected to the displacement measurement module. The echo signal acquisition module is used to acquire the first static echo signal and the dynamic echo signal; The correction parameter calculation module is used to construct a second static echo signal based on the first static echo signal and the DC offset component in the first static echo signal, and to obtain amplitude imbalance parameters and phase imbalance parameters based on the second static echo signal; wherein, the second static echo signal includes a second static echo I signal and a second static echo Q signal, and the expression for the second static echo I signal is: wherein is the second static echo I signal, is a first static echo I signal, is a first static echo Q signal, is a DC offset component of the first static echo Q signal, is a DC offset component of the first static echo I signal, denotes derivation; The expression for the second static echo Q signal is: In the formula, This is the second static echo Q signal; The signal correction module is used to correct the dynamic echo signal according to the amplitude imbalance parameter, the phase imbalance parameter and the DC offset component to obtain the corrected dynamic echo signal. The expression for the corrected dynamic echo signal is: In the formula, The corrected dynamic echo I signal, The dynamic echo I signal before correction. The corrected dynamic echo Q signal, The dynamic echo Q signal before correction. The amplitude imbalance parameter is... The phase imbalance parameter is mentioned above. The displacement measurement module is used to obtain displacement measurement results based on the corrected dynamic echo signal.

2. The short-range millimeter-wave radar displacement measurement system according to claim 1, characterized in that, The correction parameter calculation module includes a formula-based unbalance parameter calculation unit; the formula-based unbalance parameter calculation unit calculates the unbalance parameter according to the formula... Calculate the amplitude imbalance parameter In the formula, This represents the average value of the second static echo I signal within its period. This represents the average value of the second static echo Q signal within its period; According to the formula Calculate the phase imbalance parameters In the formula, , For a fixed rate of change of distance between the millimeter-wave radar and the object being measured, This refers to the wavelength of millimeter-wave radar.

3. The short-range millimeter-wave radar displacement measurement system according to claim 1, characterized in that, The correction parameter calculation module includes an elliptic parameter estimation unit and a first unbalanced parameter calculation unit connected to the elliptic parameter estimation unit; The ellipse parameter estimation unit is used to obtain ellipse parameters based on the implicit equation of the oblique ellipse and the second static echo signal; the implicit equation of the oblique ellipse is: In the formula, Let be the unknown parameters of the implicit equation of the oblique ellipse; the matrix expression of the implicit equation of the oblique ellipse is: In the formula, The number of sample points. , ; The ellipse parameters The expression is: In the formula, , For matrix symmetric matrix; The first imbalance parameter calculation unit is used to calculate the amplitude imbalance parameter and the phase imbalance parameter based on the elliptic parameters; wherein, the expression for the amplitude imbalance parameter is: In the formula, The amplitude imbalance parameter; The expression for the phase imbalance parameter is: In the formula, The phase imbalance parameter is denoted as .

4. The short-range millimeter-wave radar displacement measurement system according to any one of claims 2-3, characterized in that, The direction of the phase imbalance parameter is positive when the coefficient of determination is greater than 1 and negative when it is less than 1; wherein, when the phase imbalance parameter and When, the determination coefficient The expression is: In the formula, , , , , , The signal period of the first static echo signal is given. This is the first static echo I signal. This is the first static echo Q signal.

5. The short-range millimeter-wave radar displacement measurement system according to claim 1, characterized in that, The correction parameter calculation module includes a complex signal construction unit and a second imbalance parameter calculation unit; The complex signal construction unit is used to construct a complex signal based on the second static echo signal, and to perform an Euler transform on the complex signal; the expression of the complex signal is: The expression for the complex signal after Euler transform is: In the formula, , , , The frequency of the first static echo signal; The second unbalance parameter calculation unit is used to calculate the unbalance parameter based on the complex signal after Euler transformation in the frequency spectrum. as well as The amplitude information at a given location is used to obtain the amplitude imbalance parameter and the phase imbalance parameter through a mathematical relationship; the expression for the mathematical relationship is: In the formula, Represents the real part of the signal. Represents the imaginary part of the signal. This indicates that the complex signal after the Euler transform is in The amplitude at that point, The conjugate signal of the complex signal after the Euler transform is represented in... The amplitude at that point, Indicates intermediate frequency signal; The amplitude imbalance parameter The expression is: The phase imbalance parameter The expression is: In the formula, The four quadrants are the original and reverse tangents.

6. The short-range millimeter-wave radar displacement measurement system according to claim 1, characterized in that, The echo signal acquisition module includes a signal preprocessing unit, which is connected to the signal correction module. The signal preprocessing unit is used to denoise the dynamic echo signal; wherein the denoising method includes at least one of the following: finite-length unit impulse response low-pass filter, wavelet decomposition denoising, and low-frequency component in maximal discrete wavelet transform.

7. The short-range millimeter-wave radar displacement measurement system according to claim 1, characterized in that, The displacement measurement module includes an arctangent demodulation unit, which is connected to the signal correction module. The arctangent demodulation unit is used to perform arctangent demodulation on the corrected dynamic echo signal to obtain the displacement measurement result; the expression for the displacement measurement result is: In the formula, This represents the displacement measurement result at time t. The corrected dynamic echo I signal, This is the corrected dynamic echo Q signal.

8. The short-range millimeter-wave radar displacement measurement system according to claim 1, characterized in that, The displacement measurement module includes a long displacement measurement unit, which is connected to the signal correction module. The long displacement measurement unit is used to obtain the displacement measurement result by employing a translation phase angle algorithm when the displacement information change is greater than half the wavelength measurement range; the expression for the displacement measurement result is: In the formula, This represents the displacement measurement result at time t. The corrected dynamic echo I signal, This is the corrected dynamic echo Q signal.

9. The short-range millimeter-wave radar displacement measurement system according to claim 1, characterized in that, The period of the first static echo signal for: In the formula, For a fixed rate of change of distance between the millimeter-wave radar and the object being measured, For millimeter-wave radar wavelength, The frequency of the first static echo signal is denoted as .

Images