4D millimeter wave MIMO radar fan blade deformation detection method and system

Abstract

The invention relates to a 4D millimeter wave MIMO radar fan blade deformation detection method and system. According to the method, a 4D millimeter wave MIMO radar antenna after layout optimization is used for transmitting a radio frequency signal to a fan blade, signal processing is carried out on the radio frequency signal reflected by the fan blade, and blade deformation detection is achieved in the horizontal angle direction and the pitch angle direction. The system provided by the invention is used for implementing the method. Compared with the prior art, the method has the advantages that the antenna array is arranged, so that the horizontal angle and the pitch angle of the fan blade are measured at the same time on the premise of minimizing the side lobe influence, the misjudgment risk is avoided, and the precision and the reliability of deformation detection of the fan blade are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation detection, and in particular to a 4D millimeter wave MIMO radar fan blade deformation detection method and system. Background Art

[0002] Under the background of global energy transformation, the demand for clean energy is increasing. As an important renewable energy, wind power generation has broad application prospects. As the core component of wind energy conversion, wind turbine blades are increasing in size with the development of wind power technology, which makes the deformation problem of blades more and more significant. Excessive deformation may not only cause the blade tip to collide with the tower, but also cause the blade to break, resulting in serious economic losses. Therefore, accurate and timely detection of the deformation of wind turbine blades is crucial to ensuring equipment safety and improving wind power operation efficiency. Among them, China's patent application "CN116148832A" provides a method and device for detecting the clearance of wind turbine blades by phased array radar. The patent sets a phased array radar at the tower base, and transmits beams in sequence according to the set time difference through multiple linearly arranged radars. The beams are superimposed to form a main beam of enhanced signals, thereby forming a blade detection area; by synchronously adjusting the elevation angle of the radar transmission beam, the distance measurement data of the blades is collected in real time and the clearance distance of the blades is calculated. Although it can ensure that when one or more radars fail, reliable data can still be obtained. However, it can only measure the pitch angle, that is, only when the blade is parallel to the tower, the detection effect is more ideal. However, in actual applications, the blades of wind turbines are usually continuously rotated by wind. The rotation of the blades causes the angle between them and the tower to change, so that the blades are not always facing the radar. At this time, relying solely on the pitch angle for measurement will not accurately reflect the actual position of the blade. Since the horizontal angle of the blade is not measured, the calculated blade position may deviate from the actual position, which will lead to misjudgment of the blade position. This misjudgment will seriously affect the measurement accuracy, and then produce inaccurate judgments on the actual deformation of the blade.

[0003] Therefore, how to provide a method that can fully realize the deformation detection of wind turbine blades is a technical problem that needs to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide a 4D millimeter wave MIMO radar fan blade deformation detection method and system, which can simultaneously detect the pitch angle and horizontal angle of the fan blade through the 4D millimeter wave MIMO radar, and perform more comprehensive and accurate fan blade deformation detection.

[0005] The purpose of the present invention can be achieved by the following technical solutions: According to a first aspect of the present invention, a 4D millimeter wave MIMO radar fan blade deformation detection method is provided, wherein the method uses the antenna of the 4D millimeter wave MIMO radar after optimized layout to transmit a radio frequency signal to the fan blade, and performs signal processing on the radio frequency signal reflected by the fan blade to realize the fan blade deformation detection, wherein the antenna includes a transmitting antenna array and a receiving antenna array, and the method for optimizing the antenna layout is: Obtaining the maximum pitch angle detection angle range and pitch angle resolution of the 4D millimeter wave MIMO radar, and calculating the minimum vertical spacing between two adjacent receiving units and the vertical aperture of the receiving antenna array based on the maximum pitch angle detection angle range and pitch angle resolution of the 4D millimeter wave MIMO radar; Based on the minimum spacing between the two adjacent receiving units and the antenna array aperture, and based on the limitation of the carrier chip, the antenna arrangement of the receiving antenna array is determined with the goal of minimizing the side lobes; Obtaining the maximum horizontal angle detection range and horizontal angle resolution of the 4D millimeter wave MIMO radar, and calculating the minimum horizontal spacing between two adjacent transmitting units and the horizontal aperture of the transmitting antenna array based on the maximum horizontal angle detection range and horizontal angle resolution of the 4D millimeter wave MIMO radar; Based on the horizontal spacing between the two adjacent transmitting units, the horizontal aperture of the transmitting antenna array, and the limitations of the actual size of the carrier chip and the antenna, the antenna arrangement of the transmitting antenna array is determined with the goal of maximizing the number of horizontally arranged antenna units of the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array.

[0006] As a preferred technical solution, the method for calculating the minimum vertical spacing and the minimum horizontal spacing is: , in, is the maximum detection angle of the millimeter wave radar; is the signal wavelength of millimeter wave radar; is the minimum distance between two adjacent antennas, and , Indicates the minimum horizontal distance between two adjacent transmitting antennas. Indicates the minimum vertical spacing between two adjacent receiving antennas.

[0007] As a preferred technical solution, the method for calculating the vertical aperture of the receiving antenna array and the horizontal aperture of the transmitting antenna array is: , in, is the angular resolution of the millimeter-wave radar, is the signal wavelength of the millimeter-wave radar, is the antenna array aperture, and , represents the horizontal aperture of the transmitting antenna array, Indicates the vertical aperture of the receiving antenna array.

[0008] As a preferred technical solution, the method for determining the antenna arrangement of the receiving antenna array is: Determining the number of receiving units in the receiving antenna array based on the limitation of the carrier chip; All receiving units are located in the same vertical layer, and the total length of the receiving antenna array is the vertical aperture of the receiving antenna array; All receiving units in the receiving antenna array are arranged non-uniformly and sparsely, with the goal of minimizing side lobes, and the interval between adjacent receiving units in the same vertical layer is determined, and the interval between adjacent receiving units is an integer multiple of the minimum vertical spacing between the two adjacent receiving antennas.

[0009] As a preferred technical solution, the method for determining the antenna arrangement of the transmitting antenna array is: Determining the number of transmitting units in the transmitting antenna array based on the limitation of the carrier chip; Each transmitting unit is arranged in a separate row, and the horizontal interval between two adjacent transmitting units in the horizontal direction is the minimum horizontal interval between two adjacent transmitting antennas; Within the limitation of the actual antenna size, the vertical spacing between the horizontally arranged antenna units and the adjacent transmitting units in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array is minimized, and the vertical spacing between two adjacent transmitting units in the transmitting antenna array is determined; Within the limitation of the actual antenna size, the number of antenna units horizontally arranged in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array is maximized to determine the vertical aperture of the transmitting antenna array; The vertical arrangement of the emission units is determined based on the vertical spacing and the vertical aperture.

[0010] As a preferred technical solution, the signal processing method is: Converting the radio frequency signal reflected by the fan blades into an intermediate frequency digital signal, and performing a fast Fourier transform in the distance domain on the intermediate frequency digital signal to obtain distance information of the fan blades; Performing a fast Fourier transform in the speed domain on the intermediate frequency digital signal after the fast Fourier transform in the distance domain to obtain the speed information of the fan blades; Based on the speed information, the wind blades to be detected are screened, and the phase difference of the received signals of the wind blades to be detected from different receiving units is obtained to perform angle joint estimation to generate angle information of the wind blades to be detected, wherein the angle information includes horizontal angle information and pitch angle information; Based on the distance information, speed information and angle information, three-dimensional point cloud data is generated, and signal preprocessing is performed to filter out effective point cloud data; wherein the three-dimensional point cloud data is in the form of: , R represents distance information, Indicates the horizontal angle information, Indicates pitch angle information; The valid point cloud data is compared with the pre-stored standard point cloud data, and a detection result is generated.

[0011] As an optimal technical solution, the signal preprocessing method is: using a constant false alarm rate detection algorithm, adaptively filtering the noise and interference in the three-dimensional point cloud data, determining the valid target point cloud, and outputting the filtered valid point cloud data.

[0012] As a preferred technical solution, the method for generating the test results is: Aligning the valid point cloud data with the standard point cloud data in the same coordinate system; Calculate the Euclidean distance between each point cloud in the aligned valid point cloud data and the corresponding point cloud in the standard point cloud data; A detection result is obtained based on the Euclidean distance.

[0013] According to a second aspect of the present invention, a 4D millimeter wave MIMO radar fan blade deformation detection system is provided, comprising a monolithic microwave integrated circuit, an STM32 control module, an FPGA signal processing module, a power amplifier and an antenna generated by the above method, wherein: The monolithic microwave integrated circuit is used to generate a radio frequency signal of a millimeter wave radar, mix the radio frequency signal reflected by the fan blade to be detected with the local oscillator of the millimeter wave radar to generate an intermediate frequency analog signal, and convert the intermediate frequency analog signal into an intermediate frequency digital signal; The power amplifier is located between the monolithic microwave integrated circuit and the antenna, and is used to amplify the radio frequency signal generated by the monolithic microwave integrated circuit; The antenna comprises a transmitting antenna array and a receiving antenna array. The transmitting antenna array is used to transmit the radio frequency signal amplified by the power amplifier, and comprises a plurality of transmitting units. The receiving antenna array is used to receive the radio frequency signal reflected by the wind turbine blade to be detected and transmit it back to the monolithic microwave integrated circuit, and comprises a plurality of receiving units. The transmitting antenna array and the receiving antenna array are located in the same horizontal plane. The STM32 control module is used to control the single-chip microwave integrated circuit to generate radio frequency signals and output detection results; The FPGA signal processing module is used to process the intermediate frequency digital signal output by the monolithic microwave integrated circuit, perform real-time digital processing and transmit the detection result to the STM32 control module.

[0014] As a preferred technical solution, the starting operating frequency of the transmitting unit is 79 GHz, the maximum bandwidth is 1 GHz, and the usable frequency range is 79 GHz-80 GHz; the starting operating frequency of the receiving unit is 79 GHz, the maximum bandwidth is 1 GHz, and the usable frequency range is 79 GHz-80 GHz.

[0015] Compared with the prior art, the present invention provides a 4D millimeter wave MIMO radar fan blade deformation detection method and system, which optimizes the antenna arrangement to achieve more comprehensive and accurate fan blade deformation detection, and has the following beneficial effects: 1) In the present invention, within the maximum pitch angle range of the millimeter wave radar, with the goal of minimizing the sidelobe influence, the receiving units are non-uniformly and sparsely arranged in the vertical direction according to the antenna array arrangement scheme generated by the method. At the same time, with the goal of having as many horizontally arranged elements as possible in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array, the transmitting units in the antenna are evenly arranged according to the antenna array arrangement scheme generated by the method, ensuring that the receiving antenna array and the transmitting antenna array can work together in the horizontal and vertical directions, and can simultaneously detect the horizontal angle and pitch angle of the target, so that the coverage range of the radio frequency signal emitted by the antenna can fully match the morphological characteristics of the wind turbine blades; that is, the angular resolution and viewing angle of the 4D millimeter-wave MIMO radar are more suitable for the detection of slender targets such as wind turbine blades, and a relatively high pitch angle resolution can be obtained, and at the same time, the side lobes can be effectively suppressed within the maximum pitch angle range of the millimeter-wave radar to avoid angle misjudgment; and the method also uses virtual aperture technology to achieve comprehensive measurement of the horizontal angle and pitch angle during the detection process, and simultaneously obtain the horizontal position and vertical position of the wind turbine blade, so as to more accurately determine the three-dimensional coordinates of the blade, and finally achieve all-round accurate and reliable deformation detection of the wind turbine blade.

[0016] 2) The system provided by the present invention has significant advantages such as all-weather operation, high measurement accuracy, safety and reliability. Specifically, the 4D millimeter wave MIMO radar has strong penetration ability and can work stably under various climatic conditions, including severe weather such as strong winds, rain, snow, fog and haze. Unlike optical sensors, it is not affected by weather changes, which enables the system to continuously monitor and detect wind turbine blades under all-weather conditions. Moreover, due to the use of virtual aperture technology and advanced measurement algorithms, the system can provide extremely high measurement accuracy, ensuring that the detected wind turbine blade position, deformation and health status data are very accurate, providing a reliable basis for wind turbine maintenance and fault warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of the method of the present invention; Figure 2 This is a test result diagram of Example 2 of the present invention; Figure 3 It is a schematic diagram of the arrangement of the receiving antenna array of the present invention; Figure 4 A schematic diagram of a signal receiving virtual aperture of the antenna of the present invention; Figure 5 It is a schematic diagram of the arrangement of the transmitting antenna array of the present invention; Figure 6 A schematic diagram of an antenna array arrangement of the present invention; Figure 7 It is the structural frame of the fan blade deformation detection system of the present invention; Figure 8 The figure is a schematic diagram of the placement position of the millimeter wave radar of the present invention. DETAILED DESCRIPTION

[0018] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0019] Unless otherwise defined, the technical terms or scientific terms involved in this application should be understood by people with ordinary skills in the technical field to which this application belongs. The words "one", "a", "a", "the" and the like involved in this application do not indicate a quantitative limitation, and may represent the singular or plural. The terms "include", "comprise", "have" and any of their variations involved in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like involved in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The "multiple" involved in this application refers to two or more. "And / or" describes the association relationship of associated objects, indicating that there may be three relationships, for example, "A and / or B" can represent: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the objects before and after are in an "or" relationship. The terms "first", "second", "third", etc. involved in this application are only used to distinguish similar objects and do not represent a specific ordering of the objects.

[0020] Example 1 This embodiment aims to provide a 4D millimeter wave MIMO radar fan blade deformation detection method, by using a 4D millimeter wave MIMO radar to transmit a radio frequency signal to the fan blade, and performing signal processing on the radio frequency signal reflected by the fan blade, completing the fan blade deformation detection, and performing more extensive detection and more accurate blade deformation detection. Most of the current MIMO radars are used in automotive scenes, and their design focuses mainly on a shorter detection distance, a large range of field angles, and a small difference in resolution between the horizontal and pitch directions, which is significantly different from the detection requirements of fan blades. In particular, the slender shape of the fan blades makes its detection requirements different from those of the automotive scene. The detection of fan blades does not require an excessively large field angle, but focuses more on the accurate positioning of the target in the pitch direction, and the accuracy requirements for the horizontal direction are relatively low. In addition, the existing radar system is difficult to meet the accuracy requirements of blade detection due to its large field angle and the small difference in resolution between the horizontal and pitch directions. To this end, this embodiment optimizes the configuration of the receiving antenna array and the transmitting antenna array in the antenna of the 4D millimeter wave MIMO radar.

[0021] Specifically, the process of optimizing antenna layout is as follows: Figure 1 As shown, including: A1. Calculate the minimum spacing between two adjacent antenna units and the antenna array aperture.

[0022] In the actual antenna arrangement scenario, the vertical spacing between receiving units and the vertical aperture of the antenna are determined by the maximum detection pitch angle range and the radar pitch angle resolution of the radar. The horizontal spacing between transmitting units and the horizontal aperture of the antenna are determined by the maximum detection horizontal angle range and the radar horizontal angle resolution of the radar.

[0023] The minimum vertical spacing between adjacent receiving units in the receiving antenna and the minimum horizontal spacing between adjacent transmitting units in the transmitting antenna are solved in the same way, which are: ,in, is the maximum detection angle of the millimeter wave radar; is the signal wavelength of millimeter wave radar; is the minimum distance between two adjacent antennas, and , Indicates the minimum horizontal distance between two adjacent transmitting antennas. Indicates the minimum vertical spacing between two adjacent receiving antennas. The vertical aperture of the receiving antenna array and the horizontal aperture of the transmitting antenna array are also solved in the same way: ,in, is the angular resolution of the millimeter-wave radar, is the signal wavelength of the millimeter-wave radar, is the antenna array aperture, and , represents the horizontal aperture of the transmitting antenna array, Indicates the vertical aperture of the receiving antenna array.

[0024] In detail, the solution process is as follows: A11. Obtain the maximum detection pitch angle range, pitch angle resolution, maximum detection horizontal angle range and horizontal angle resolution of the millimeter wave radar.

[0025] A12. Calculate the minimum vertical spacing between two adjacent receiving units based on the maximum detection pitch angle range. The expression is: , in, is the maximum detection pitch angle range of the millimeter wave radar, is the signal wavelength of the millimeter-wave radar, is the minimum vertical spacing between two adjacent receiving antennas.

[0026] A13. Calculate the vertical aperture of the receiving antenna array based on the pitch angle resolution of the millimeter wave radar. The expression is: , in, is the angular resolution of the millimeter-wave radar, is the signal wavelength of the millimeter-wave radar, is the vertical aperture of the receiving antenna array.

[0027] A14. Calculate the minimum vertical spacing between two adjacent receiving units based on the maximum detection horizontal angle range. The expression is: , in, is the maximum detection horizontal angle range of the millimeter wave radar, is the signal wavelength of the millimeter-wave radar, is the minimum vertical spacing between two adjacent transmitting antennas.

[0028] A15. The vertical aperture of the receiving antenna array is calculated based on the horizontal angle resolution of the millimeter-wave radar. The expression is: , in, is the angular resolution of the millimeter-wave radar, is the signal wavelength of the millimeter-wave radar, is the vertical aperture of the transmitting antenna array.

[0029] A2. Determine the antenna arrangement of the receiving antenna array.

[0030] A21. Determine the number of receiving units in the receiving antenna array based on the limitation of the carrier chip, that is, the number of receiving units that can be installed on the carrier chip of the antenna unit.

[0031] A22. All receiving units are located in the same vertical layer, and the total length of the horizontal receiving antenna array is the vertical aperture of the horizontal receiving antenna array.

[0032] A23. All receiving units in the receiving antenna array are arranged non-uniformly and sparsely, with the goal of minimizing side lobes. The interval between adjacent receiving units in the same vertical layer is determined, and the interval between adjacent receiving units is an integer multiple of the minimum vertical spacing between two adjacent horizontal receiving antennas.

[0033] A3. Determine the antenna arrangement of the transmitting antenna array.

[0034] In practical applications, wind turbine blades are usually in a rotating state. When the blades enter the detection range of the radar, a certain angle is often formed between the blades and the tower. At this time, if the radar system can only detect the pitch angle but cannot obtain the horizontal angle of the blade, then calculations based on only the distance and pitch angle may lead to errors in the blade position. Therefore, when arranging the transmitting antenna array, the virtual aperture technology is introduced. The goal is to maximize the number of horizontally arranged antenna units of the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array and minimize the vertical spacing between the horizontally arranged antenna units and adjacent transmitting units. The transmitting antenna arrangement in the transmitting antenna array is planned to achieve simultaneous acquisition of the horizontal and vertical positions of the blades, thereby more accurately determining the three-dimensional coordinates of the blades, and accurately detecting the deformation of the wind turbine blades based on the obtained three-dimensional point cloud data of the blades to be detected.

[0035] In detail, the steps include: A31. Determine the number of transmitting units in the transmitting antenna array based on the limitation of the horizontal carrier chip.

[0036] A32. Each transmitting unit is arranged in a separate row, and the horizontal spacing between two adjacent transmitting units in the horizontal direction is the minimum horizontal spacing between two adjacent transmitting antennas.

[0037] A33. Within the limitations of the actual antenna size, the vertical spacing between the horizontally arranged antenna units and adjacent transmitting units in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array is minimized, and the vertical spacing between two adjacent transmitting units in the transmitting antenna array is determined.

[0038] A34. Within the limitation of the actual antenna size, the number of antenna units arranged horizontally in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array is maximized to determine the vertical aperture of the transmitting antenna array.

[0039] A35. Determine the vertical arrangement of the horizontal receiving units based on the horizontal and vertical spacing and the vertical aperture.

[0040] After the arrangement of steps A1 to A3, it can be ensured that within the maximum detection angle range of the radar, the antenna angle resolution is improved, the sidelobe effect can be suppressed, and the angle misjudgment can be effectively avoided; and this design fully conforms to the morphological characteristics of the wind turbine blades (the blades are wider in the horizontal direction and longer in the pitch direction). According to the slender shape of the blades, during actual detection, the main focus is on the accurate positioning of the blades in the pitch direction, and less attention is paid to their accuracy in the horizontal direction. Therefore, by optimizing the antenna layout design, the radar's field of view and resolution are more suitable for slender targets such as wind turbine blades, ensuring that the radar system can accurately obtain the three-dimensional point cloud data of the blades in space, which not only improves the accuracy of radar imaging, but also better adapts to the actual detection needs of wind turbine blades.

[0041] After the antenna layout of the 4D millimeter wave MIMO radar is optimized, the antenna of the 4D millimeter wave MIMO radar with the optimized layout is used to transmit RF signals to the wind turbine blades, and the RF signals reflected by the wind turbine blades are processed, including: S1. Convert the radio frequency signal reflected by the fan blades into an intermediate frequency digital signal, and perform fast Fourier transform of the intermediate frequency digital signal in the distance domain to obtain the distance information of the fan blades.

[0042] S2. Performing a fast Fourier transform in the speed domain on the intermediate frequency digital signal after the fast Fourier transform in the distance domain to obtain the speed information of the fan blades.

[0043] S3. Screen the wind blades to be detected based on the speed information, obtain the phase difference of the received signals of the wind blades to be detected from different receiving units, perform angle joint estimation, and generate angle information of the wind blades to be detected, where the angle information includes horizontal angle information and pitch angle information.

[0044] S4. Generate three-dimensional point cloud data based on distance information, speed information and angle information, and perform signal preprocessing to filter effective point cloud data; wherein the three-dimensional point cloud data is in the form of: , R represents the distance information, Indicates the horizontal angle information, Indicates the pitch angle information.

[0045] In detail, the signal preprocessing adopts a constant false alarm rate detection algorithm to perform adaptive filtering on the noise and interference in the three-dimensional point cloud data, determine the valid target point cloud, and output the filtered valid point cloud data.

[0046] S5. Compare the valid point cloud data with the pre-stored standard point cloud data and generate a detection result.

[0047] S51. Align the valid point cloud data and the standard point cloud data in the same coordinate system.

[0048] S52, calculating the Euclidean distance between each point cloud in the aligned valid point cloud data and the corresponding point cloud in the standard point cloud data.

[0049] S53. Generate a deformation statistics table based on the Euclidean distance, record the deviation value, and assign a color value to each point cloud according to the size of the deviation value. Blue represents point clouds with smaller deformation, green represents point clouds with moderate deformation, and red represents point clouds with significant deformation. Generate a three-dimensional heat map to intuitively represent the deformation conditions of various areas on the blade surface. If the deformation deviation exceeds the preset range, the system will issue an alarm signal and record the specific location of the abnormal deformation.

[0050] S54. Obtain detection results based on the thermal map, deformation statistics table and alarm log.

[0051] In addition to steps S1 to S5, in this embodiment, the signal processing method further includes: 1) Pulse accumulation processing: accumulate radar echo signals received from different antennas to improve the signal-to-noise ratio and enhance the detection capability of weak targets.

[0052] 2) Array correction: Correct the amplitude and phase inconsistency of the antenna array to improve the angle estimation accuracy of the angle measurement algorithm, including: B1. Obtain reference signal. First, obtain reference signal by placing a corner reflector 5 meters in front of the radar. The pitch angle of this position is 0° and the horizontal angle is 0°.

[0053] B2. Measure array response. After installing the corner reflectors, the radar antenna array begins to receive the reflected signals and records the amplitude and phase information of the signals received from each antenna.

[0054] B3. Calculation error. Due to factors such as differences in feeder lengths between different antennas and deviations in manufacturing processes, the actual received signals are often inconsistent. In order to quantify these differences, it is necessary to compare the actual measured signals with the theoretical expected values, and then calculate the amplitude error and phase error of each antenna.

[0055] B4. Amplitude and phase correction. Based on the error analysis results, the amplitude and phase correction of the array begins. First, amplitude correction is performed. The amplitude of a certain reference antenna is used as a reference. By correcting the amplitude error of each antenna, the amplitude of all antennas is ensured to be consistent. Subsequently, phase correction is also performed based on the phase of a certain reference antenna. The phase of each antenna is adjusted to eliminate the phase error and ensure that the phase of the signals received by all antennas is consistent.

[0056] B5. Verify the correction effect. To verify whether the correction is successful, use the corner reflector as the signal source again and let the antenna array receive the reflected signal. By comparing with the measured data before correction, check whether the amplitude and phase of the signal received by each antenna have reached the expected ideal state. If the amplitude and phase of all antennas are close to the same at the current moment, it means that the correction has been successful.

[0057] 3) Signal deblurring: For targets with range ambiguity, a deblurring algorithm is used to restore the true range information.

[0058] Example 2 In this embodiment, the antenna arrangement of the MIMO radar with three transmission channels is optimized by the above method. According to the actual measurement requirements, the maximum pitch measurement angle range of the millimeter wave radar is set to And set the pitch angle resolution to 5°, then and According to the calculation, it can be concluded that the minimum vertical spacing between two adjacent receiving units in the receiving antenna array in this embodiment is 1.9 wavelengths, and the vertical aperture of the receiving antenna array is 11.4 wavelengths; the maximum horizontal measurement angle range of the millimeter wave radar is set to And set its horizontal angle resolution to 10°, then the formula and According to the calculation, it can be concluded that the minimum horizontal spacing between two adjacent transmitting units in the transmitting antenna array in this embodiment is 1.9 wavelengths, and the horizontal aperture of the transmitting antenna array is 3.8 wavelengths.

[0059] Given the minimum spacing between two adjacent receiving units and the aperture of the receiving antenna array, it is first determined that the arrangement of the receiving antenna array is such that the spacing between two adjacent transmitting units in the vertical direction is an integer multiple of the minimum vertical spacing of 1.9 wavelengths. In this embodiment, the receiving array includes 4 receiving units. With the goal of minimizing the sidelobe effect, the arrangement of the receiving units is tested to determine the optimal arrangement of the receiving units, and four arrangements are selected, including: Solution 1: The first receiving unit and the second receiving unit are separated by 1 minimum spacing, the first receiving unit and the third receiving unit are separated by 2 minimum spacings, and the first receiving unit and the fourth receiving unit are separated by 6 minimum spacings; Solution 2: The first receiving unit and the second receiving unit are separated by 1 minimum spacing, the first receiving unit and the third receiving unit are separated by 3 minimum spacings, and the first receiving unit and the fourth receiving unit are separated by 6 minimum spacings; Solution 3: The first receiving unit and the second receiving unit are separated by 3 minimum spacings, the first receiving unit and the third receiving unit are separated by 4 minimum spacings, and the first receiving unit and the fourth receiving unit are separated by 6 minimum spacings; Solution 4: The 4 receiving units are arranged linearly.

[0060] The test results are as follows Figure 2 As shown in Figure 2, it can be found that when a non-uniform layout is used (such as Scheme 2), the side lobes mainly appear in In the direction of, while for scheme 1, the side lobe appears For detection scenarios, these two layouts are affected by side lobes, which can cause potential problems, because the detection area requires accurate detection of The blade targets within the range, and within this range, the fan blades may appear and If the side lobes appear at these angles, it is easy to produce false target detection, which will lead to misjudgment of angles and affect the detection results. This is very unfavorable for the detection of wind turbine blades. In contrast, the side lobes of Scheme 3 appear at location, and This is almost the maximum angle the blade can reach. Under normal circumstances, the blade will not reach this angle. There are side lobes in the direction, but because the blades rarely appear in this angle range in the context of this embodiment, these side lobes will not interfere with the detection results, nor will they lead to misjudgment. This makes the antenna layout of Scheme Three more suitable for actual wind blade detection applications, and can provide more accurate and reliable detection performance. Compared with the linear array arrangement, it can be seen that the antenna after optimization and arrangement according to the method provided in the above embodiment can significantly reduce the 3dB beam width, improve the angular resolution, and is suitable for wind blade detection tasks. In summary, the arrangement of Scheme Three is more stable, can significantly reduce the 3dB beam width, improve the angular resolution, and at the same time In order to effectively suppress the side lobes within the angle range and avoid angle misjudgment, the original receiving antenna array was arranged as follows Figure 3 as shown. After determining the arrangement of the receiving antenna array, arrange the transmitting antenna array. With the goal of maximizing the number of horizontally arranged antenna units of the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array and minimizing the vertical spacing between the horizontally arranged antenna units and the adjacent transmitting units, plan the arrangement of the transmitting antenna array in the transmitting antenna array to achieve simultaneous acquisition of the horizontal and vertical positions of the blades. First, determine the vertical spacing between adjacent transmitting units in the transmitting antenna array. The number of horizontally arranged antenna units in the virtual aperture array is maximized to 3. When arranging, it is necessary to meet the requirement that the virtual aperture must have at least one row of antenna units of 3 in the horizontal direction. Based on the actual antenna size, it can be obtained that the size of a single transmitting antenna is 5 wavelengths in the vertical direction, that is, the vertical spacing between the two transmitting antennas must be at least greater than 5 wavelengths, and the horizontal spacing between the two transmitting units is 1.9 wavelengths, that is, this spacing does not allow adjacent transmitting units to be located on the same horizontal line. Therefore, it can be obtained that the virtual aperture array arrangement should be as follows Figure 4 As shown, the corresponding transmit antenna array arrangement should be as follows Figure 5 As shown, the vertical interval between adjacent transmitting units should be 5.7 wavelengths and the vertical aperture should be 11.4 wavelengths.

[0061] After separately determining the arrangement of the antenna units in the transmitting antenna array and the receiving antenna array, place the receiving antenna array and the transmitting antenna array on the same horizontal plane, and place the receiving antenna array and the second transmitting unit in the transmitting antenna array on the same vertical line, such as Figure 6 As shown. After this arrangement, the receiving antenna array and the transmitting antenna array can work together in the horizontal and vertical directions, and can detect the horizontal angle and pitch angle of the target at the same time, so that the coverage range of the RF signal sent by the antenna can fully match the morphological characteristics of the wind turbine blades; that is, the angular resolution and viewing angle of the 4D millimeter wave MIMO radar are more suitable for the detection of slender targets such as wind turbine blades, and can obtain a relatively high pitch angle resolution, and can also effectively suppress the side lobes within the maximum pitch angle range of the millimeter wave radar to avoid angle misjudgment; and the method also uses virtual aperture technology to achieve comprehensive measurement of the horizontal angle and pitch angle during the detection process, and obtain the horizontal position and vertical position of the wind turbine blade at the same time, so as to more accurately determine the three-dimensional coordinates of the blade, thereby achieving all-round accurate and reliable deformation detection of the wind turbine blade.

[0062] Example 3 This embodiment provides a 4D millimeter wave MIMO radar fan blade deformation detection system, the framework is as follows Figure 7 As shown, it includes a monolithic microwave integrated circuit, an STM32 control module, an FPGA signal processing module, a power amplifier and the antenna provided in Example 2, and the functions implemented by each module are as follows: The monolithic microwave integrated circuit is used to generate the radio frequency signal of the millimeter wave radar, mix the radio frequency signal reflected by the wind turbine blade to be detected with the local oscillator of the millimeter wave radar to generate an intermediate frequency analog signal, and convert the intermediate frequency analog signal into an intermediate frequency digital signal.

[0063] The power amplifier is located between the monolithic microwave integrated circuit and the antenna, and is used to amplify the radio frequency signal generated by the monolithic microwave integrated circuit.

[0064] The antenna includes a transmitting antenna array and a receiving antenna array, both of which use horizontally polarized microstrip antennas. The transmitting antenna array is used to transmit the radio frequency signal amplified by the power amplifier, including multiple transmitting units, with a starting operating frequency of 79GHz, a maximum bandwidth of 1GHz, and a usable frequency range of 79GHz-80GHz; the receiving antenna array is used to receive the radio frequency signal reflected by the wind turbine blades to be detected and transmit it back to the monolithic microwave integrated circuit, including multiple receiving units, with a starting operating frequency of 79GHz, a maximum bandwidth of 1GHz, and a usable frequency range of 79GHz-80GHz. And due to the special antenna array arrangement, the transmitting antenna array and the receiving antenna array will form a signal receiving virtual aperture in the horizontal direction. This technology is used to detect the azimuth information in the vertical and horizontal directions to achieve comprehensive measurement of the horizontal angle and pitch angle.

[0065] The STM32 control module is used to control the single-chip microwave integrated circuit to generate radio frequency signals and output detection results.

[0066] The FPGA signal processing module is used to process the intermediate frequency digital signal output by the monolithic microwave integrated circuit, perform real-time digital processing and transmit the detection results to the STM32 control module.

[0067] In actual application, the wind turbine blade deformation detection system provided in this embodiment is placed on the side of the tail of the nacelle of the wind turbine, so that the beam of the millimeter wave radar is tilted to point to the blade, so as to obtain the blade point cloud information. Figure 8 As shown, after the placement is completed, an instruction is sent to the system, so that the system performs the following steps: C1, STM32 control module enables the single-chip microwave integrated circuit to generate a radio frequency signal and amplify the radio frequency signal through a power amplifier, and then send it to the wind turbine blade to be detected by the transmitting antenna array.

[0068] After amplification by the power amplifier, the maximum distance that the millimeter-wave radar can measure the target is: , Among them, Pt is the signal transmission power, Gt is the transmitting antenna gain, Gr is the receiving antenna gain, RCS is the radar reflection cross-sectional area, λ is the wavelength of the radar signal, and Smin is the minimum detectable power of the radar receiver.

[0069] C2. The receiving antenna array receives the radio frequency signal reflected by the wind turbine blade to be detected and sends it to the monolithic microwave integrated circuit.

[0070] C3. The radio frequency signal reflected by the wind turbine blade to be detected is converted into an intermediate frequency analog signal by a single-chip microwave integrated circuit, and the intermediate frequency analog signal is converted into an intermediate frequency digital signal and then sent to the FPGA signal processing module.

[0071] C4, FPGA signal processing module performs signal processing on the intermediate frequency digital signal, executes steps S1 to S5 in Example 1, as well as pulse accumulation processing, array correction and signal deblurring process, which will not be repeated here.

[0072] C5, STM32 control module obtains the detection results from the FPGA signal processing module and outputs them.

[0073] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A 4D millimeter wave MIMO radar fan blade deformation detection method, characterized in that: The method uses the optimized layout of the 4D millimeter wave MIMO radar antenna to transmit radio frequency signals to the wind turbine blades, and performs signal processing on the radio frequency signals reflected by the wind turbine blades to realize deformation detection of the wind turbine blades, wherein the antenna includes a transmitting antenna array and a receiving antenna array, and the method for optimizing the antenna layout is: Obtaining the maximum pitch angle detection angle range and pitch angle resolution of the 4D millimeter wave MIMO radar, and calculating the minimum vertical spacing between two adjacent receiving units and the vertical aperture of the receiving antenna array based on the maximum pitch angle detection angle range and pitch angle resolution of the 4D millimeter wave MIMO radar; Based on the minimum spacing between the two adjacent receiving units and the antenna array aperture, and based on the limitation of the carrier chip, the antenna arrangement of the receiving antenna array is determined with the goal of minimizing the side lobes; Obtaining the maximum horizontal angle detection range and horizontal angle resolution of the 4D millimeter wave MIMO radar, and calculating the minimum horizontal spacing between two adjacent transmitting units and the horizontal aperture of the transmitting antenna array based on the maximum horizontal angle detection range and horizontal angle resolution of the 4D millimeter wave MIMO radar; Based on the horizontal spacing between the two adjacent transmitting units, the horizontal aperture of the transmitting antenna array, and the actual size limitations of the carrier chip and the antenna, the antenna arrangement of the transmitting antenna array is determined with the goal of maximizing the number of horizontally arranged antenna units of the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array; The arranged receiving antenna array and transmitting antenna array are combined and arranged.

2. A 4D millimeter wave MIMO radar fan blade deformation detection method according to claim 1, characterized in that: The method for calculating the minimum vertical spacing and the minimum horizontal spacing is: ， in, is the maximum detection angle of the millimeter wave radar; is the signal wavelength of millimeter wave radar; is the minimum distance between two adjacent antennas, and , Indicates the minimum horizontal distance between two adjacent transmitting antennas. Indicates the minimum vertical spacing between two adjacent receiving antennas.

3. The 4D millimeter wave MIMO radar fan blade deformation detection method according to claim 1 is characterized in that: The method for calculating the vertical aperture of the receiving antenna array and the horizontal aperture of the transmitting antenna array is: ， in, is the angular resolution of the millimeter-wave radar, is the signal wavelength of the millimeter-wave radar, is the antenna array aperture, and , represents the horizontal aperture of the transmitting antenna array, Indicates the vertical aperture of the receiving antenna array.

4. The 4D millimeter wave MIMO radar fan blade deformation detection method according to claim 2 is characterized in that: The method for determining the antenna arrangement of the receiving antenna array is: Determining the number of receiving units in the receiving antenna array based on the limitation of the carrier chip; All receiving units are located in the same vertical layer, and the total length of the receiving antenna array is the vertical aperture of the receiving antenna array; All receiving units in the receiving antenna array are arranged non-uniformly and sparsely, with the goal of minimizing side lobes, and the interval between adjacent receiving units in the same vertical layer is determined, and the interval between adjacent receiving units is an integer multiple of the minimum vertical spacing between the two adjacent receiving antennas.

5. The 4D millimeter wave MIMO radar fan blade deformation detection method according to claim 1 is characterized in that: The method for determining the antenna arrangement of the transmitting antenna array is: Determining the number of transmitting units in the transmitting antenna array based on the limitation of the carrier chip; Each transmitting unit is arranged in a separate row, and the horizontal interval between two adjacent transmitting units in the horizontal direction is the minimum horizontal interval between two adjacent transmitting antennas; Within the limitation of the actual antenna size, the vertical spacing between the horizontally arranged antenna units and the adjacent transmitting units in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array is minimized, and the vertical spacing between two adjacent transmitting units in the transmitting antenna array is determined; Within the limitation of the actual antenna size, the number of antenna units horizontally arranged in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array is maximized to determine the vertical aperture of the transmitting antenna array; The vertical arrangement of the emission units is determined based on the vertical spacing and the vertical aperture.

6. The 4D millimeter wave MIMO radar fan blade deformation detection method according to claim 1, characterized in that: The signal processing method is: Converting the radio frequency signal reflected by the fan blades into an intermediate frequency digital signal, and performing a fast Fourier transform in the distance domain on the intermediate frequency digital signal to obtain distance information of the fan blades; Performing a fast Fourier transform in the speed domain on the intermediate frequency digital signal after the fast Fourier transform in the distance domain to obtain the speed information of the fan blades; Based on the speed information, the wind blades to be detected are screened, and the phase difference of the received signals of the wind blades to be detected from different receiving units is obtained to perform angle joint estimation to generate angle information of the wind blades to be detected, wherein the angle information includes horizontal angle information and pitch angle information; Based on the distance information, speed information and angle information, three-dimensional point cloud data is generated, and signal preprocessing is performed to filter out effective point cloud data; wherein the three-dimensional point cloud data is in the form of: , R represents distance information, Indicates the horizontal angle information, Indicates pitch angle information; The valid point cloud data is compared with the pre-stored standard point cloud data, and a detection result is generated.

7. A 4D millimeter wave MIMO radar fan blade deformation detection method according to claim 6, characterized in that: The signal preprocessing method is: using a constant false alarm rate detection algorithm, performing adaptive filtering on noise and interference in three-dimensional point cloud data, determining a valid target point cloud, and outputting filtered valid point cloud data.

8. The 4D millimeter wave MIMO radar fan blade deformation detection method according to claim 6 is characterized in that: The method for generating the test result is: Aligning the valid point cloud data with the standard point cloud data in the same coordinate system; Calculate the Euclidean distance between each point cloud in the aligned valid point cloud data and the corresponding point cloud in the standard point cloud data; A detection result is obtained based on the Euclidean distance.

9. A 4D millimeter wave MIMO radar fan blade deformation detection system, characterized in that: The method comprises a monolithic microwave integrated circuit, an STM32 control module, an FPGA signal processing module and a power amplifier, and is characterized in that it also comprises an antenna generated by the method described in any one of claims 1 to 8, wherein: The monolithic microwave integrated circuit is used to generate a radio frequency signal of a millimeter wave radar, mix the radio frequency signal reflected by the fan blade to be detected with the local oscillator of the millimeter wave radar to generate an intermediate frequency analog signal, and convert the intermediate frequency analog signal into an intermediate frequency digital signal; The power amplifier is located between the monolithic microwave integrated circuit and the antenna, and is used to amplify the radio frequency signal generated by the monolithic microwave integrated circuit; The antenna comprises a transmitting antenna array and a receiving antenna array. The transmitting antenna array is used to transmit the radio frequency signal amplified by the power amplifier, and comprises a plurality of transmitting units. The receiving antenna array is used to receive the radio frequency signal reflected by the wind turbine blade to be detected and transmit it back to the monolithic microwave integrated circuit, and comprises a plurality of receiving units. The transmitting antenna array and the receiving antenna array are located in the same horizontal plane. The STM32 control module is used to control the single-chip microwave integrated circuit to generate radio frequency signals and output detection results; The FPGA signal processing module is used to process the intermediate frequency digital signal output by the monolithic microwave integrated circuit, perform real-time digital processing and transmit the detection result to the STM32 control module.

10. A 4D millimeter wave MIMO radar fan blade deformation detection system according to claim 9, characterized in that: The starting operating frequency of the transmitting unit is 79 GHz, the maximum bandwidth is 1 GHz, and the usable frequency range is 79 GHz-80 GHz; the starting operating frequency of the receiving unit is 79 GHz, the maximum bandwidth is 1 GHz, and the usable frequency range is 79 GHz-80 GHz.

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