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

Abstract

The present invention relates to a 4D millimeter wave MIMO radar fan blade deformation detection method and system. The method uses a 4D millimeter wave MIMO radar antenna with optimized layout to transmit radio frequency signals to the fan blades, and performs signal processing on the radio frequency signals reflected by the fan blades, thereby realizing blade deformation detection from two directions: horizontal angle and pitch angle. The provided system is used to implement the above method. Compared with the prior art, the present invention arranges the antenna array to simultaneously measure the horizontal angle and pitch angle of the fan blade while minimizing the influence of the side lobes, thereby avoiding the risk of misjudgment and improving the accuracy and reliability of fan blade deformation detection.

Description

Technical Field

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

[0002] Under the background of the global energy transition, the demand for clean energy is increasing day by day. As an important renewable energy, wind power generation has broad application prospects. The blades of wind turbines, as the core components for converting wind energy, have been increasing in size with the development of wind power technology, which makes the problem of blade deformation more prominent. Excessive deformation may not only cause the blade tip to collide with the tower barrel, but also lead to blade fracture, resulting in serious economic losses. Therefore, accurately and timely detecting the deformation of wind turbine blades is crucial for ensuring equipment safety and improving the operation efficiency of wind power. Among them, Chinese Patent Application 《CN116148832A》 provides a method and device for detecting the clearance of a wind turbine blade using a phased array radar. In this patent, a phased array radar is set at the tower base, and multiple linearly arranged radars sequentially emit beams at a set time difference. The beams are superimposed to form a main beam of enhanced signal, thereby forming a blade detection area. By synchronously adjusting the elevation angle of the radar emission beam, the ranging data of the blade is collected in real time and the clearance distance of the blade is calculated. Although it can ensure that reliable data can still be obtained when one or several radars fail, it can only measure the pitch angle, that is, when the blade is parallel to the tower barrel, its detection effect is more ideal. However, in actual applications, the blades of wind turbines are usually continuously rotated by the action of wind. The rotation of the blade causes the angle formed between it and the tower barrel to change, so that the blade is not always directly 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, resulting in misjudgment of the blade position. This misjudgment will seriously affect the measurement accuracy and further lead to an inaccurate judgment of the actual deformation of the blade.

[0003] Therefore, how to provide a method for comprehensively detecting the deformation of wind turbine blades is a technical problem to be solved. Summary of the Invention

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

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] According to the first aspect of the present invention, a method for detecting deformation of a wind turbine blade using a 4D millimeter-wave MIMO radar is provided. The method uses the antennas of the 4D millimeter-wave MIMO radar with optimized layout to transmit radio frequency signals to the wind turbine blade, and performs signal processing on the radio frequency signals reflected by the wind turbine blade to achieve deformation detection of the wind turbine blade. Among them, the antennas include a transmitting antenna array and a receiving antenna array, and the method for optimizing the antenna layout is as follows:

[0007] Obtain the maximum elevation angle detection range and elevation angle resolution of the 4D millimeter-wave MIMO radar, and calculate the minimum vertical spacing between two adjacent receiving units and the vertical aperture of the receiving antenna array based on the maximum elevation angle detection range and elevation angle resolution of the 4D millimeter-wave MIMO radar;

[0008] Based on the minimum spacing between the two adjacent receiving units and the antenna array aperture, and based on the limitations of the carrier chip, determine the antenna arrangement of the receiving antenna array with the goal of minimizing sidelobes;

[0009] Obtain the maximum horizontal angle detection range and horizontal angle resolution of the 4D millimeter-wave MIMO radar, and calculate 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;

[0010] Based on the horizontal spacing between the two adjacent transmitting units, the horizontal aperture of the transmitting antenna array, the limitations of the carrier chip and the actual size of the antenna, determine the antenna arrangement of the transmitting antenna array with the goal of maximizing the number of antenna units arranged horizontally in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array.

[0011] As a preferred technical solution, the method for calculating the minimum vertical spacing and the minimum horizontal spacing is as follows:

[0012] ,

[0013] Among them, is the maximum detection angle of the millimeter-wave radar; is the signal wavelength of the millimeter-wave radar; is the minimum spacing between two adjacent antennas, and , represents the minimum horizontal spacing between two adjacent transmitting antennas, represents the minimum vertical spacing between two adjacent receiving antennas.

[0014] 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 as follows:

[0015] ,

[0016] Among them, 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, represents the vertical aperture of the receiving antenna array.

[0017] As a preferred technical solution, the method for determining the antenna arrangement of the receiving antenna array is as follows:

[0018] Determine the number of receiving units in the receiving antenna array based on the limitations of the carrier chip;

[0019] 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;

[0020] The receiving units in the receiving antenna array are arranged non-uniformly and sparsely. With the goal of minimizing the sidelobe, determine the interval between adjacent receiving units in the same vertical layer, and the interval between adjacent receiving units is an integer multiple of the minimum vertical spacing between two adjacent receiving antennas.

[0021] As a preferred technical solution, the method for determining the antenna arrangement of the transmitting antenna array is as follows:

[0022] Determine the number of transmitting units in the transmitting antenna array based on the limitations of the carrier chip;

[0023] Each transmitting unit forms a separate column, and the horizontal interval between two adjacent transmitting units in the horizontal direction is the minimum horizontal spacing between two adjacent transmitting antennas;

[0024] Within the limitation range of the actual antenna size, minimize the vertical spacing between the antenna units arranged horizontally and the adjacent transmitting units in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array, and determine the vertical interval between two adjacent transmitting units in the transmitting antenna array;

[0025] Within the limitation range of the actual antenna size, maximize the number of antenna units arranged horizontally in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array, and determine the vertical aperture of the transmitting antenna array;

[0026] Determine the vertical arrangement of the transmitting units based on the vertical interval and the vertical aperture.

[0027] As a preferred technical solution, the method for signal processing is as follows:

[0028] Convert the radio frequency signal reflected by the fan blade into an intermediate frequency digital signal, and perform a fast Fourier transform in the distance domain on the intermediate frequency digital signal to obtain the distance information of the fan blade;

[0029] Perform a fast Fourier transform in the velocity domain on the intermediate frequency digital signal after performing the fast Fourier transform in the distance domain to obtain the velocity information of the fan blade;

[0030] Based on the velocity information, screen the fan blades to be detected, and obtain the phase differences of the received signals from different receiving units of the fan blades to be detected for joint angle estimation, and generate the angle information of the fan blades to be detected, where the angle information includes horizontal angle information and pitch angle information;

[0031] Generate three-dimensional point cloud data based on the distance information, velocity information, and angle information, and perform signal preprocessing to screen out valid point cloud data; among them, the form of the three-dimensional point cloud data is: , R represents the distance information, represents the horizontal angle information, represents the pitch angle information;

[0032] Compare the valid point cloud data with the pre-stored standard point cloud data, and generate a detection result.

[0033] As a preferred technical solution, the method of signal preprocessing is: adopt 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.

[0034] As a preferred technical solution, the method of generating the detection result is:

[0035] Align the valid point cloud data with the standard point cloud data in the same coordinate system;

[0036] 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;

[0037] Obtain the detection result based on the Euclidean distance.

[0038] According to the second aspect of the present invention, there is provided a 4D millimeter-wave MIMO radar fan blade deformation detection system, including 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, where,

[0039] The described monolithic microwave integrated circuit is used to generate radio frequency signals for millimeter-wave radar, mix the radio frequency signals reflected by the fan blade to be detected with the local oscillator of the millimeter-wave radar to generate intermediate-frequency analog signals, and convert the intermediate-frequency analog signals into intermediate-frequency digital signals;

[0040] The described power amplifier is located between the monolithic microwave integrated circuit and the antenna, and is used to amplify the radio frequency signals generated by the monolithic microwave integrated circuit;

[0041] The described antenna includes a transmitting antenna array and a receiving antenna array. The transmitting antenna array is used to transmit the radio frequency signals amplified by the power amplifier and includes multiple transmitting units; the receiving antenna array is used to receive the radio frequency signals reflected by the fan blade to be detected and transmit them back to the monolithic microwave integrated circuit, and includes multiple receiving units; and the transmitting antenna array and the receiving antenna array are located on the same horizontal plane;

[0042] The described STM32 control module is used to control the monolithic microwave integrated circuit to generate radio frequency signals and output detection results;

[0043] The described FPGA signal processing module is used to process the intermediate-frequency digital signals output by the monolithic microwave integrated circuit, perform real-time digital processing, and transmit the detection results to the STM32 control module.

[0044] As a preferred technical solution, the starting operating frequency of the described transmitting unit is 79 GHz, the maximum bandwidth is 1 GHz, and the available frequency range is 79 GHz - 80 GHz; the starting operating frequency of the described receiving unit is 79 GHz, the maximum bandwidth is 1 GHz, and the available frequency range is 79 GHz - 80 GHz.

[0045] Compared with the prior art, the present invention provides a method and system for detecting the deformation of a fan blade by a 4D millimeter-wave MIMO radar. By optimizing the antenna arrangement, more comprehensive and accurate detection of the deformation of the fan blade can be achieved, and the following beneficial effects are obtained:

[0046] 1), within the maximum pitch angle range of the millimeter-wave radar, aiming to minimize the influence of sidelobes, the receiving units are arranged non-uniformly and sparsely in the vertical direction according to the antenna array arrangement scheme generated by this method. At the same time, aiming to have as many horizontally arranged array 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 arranged uniformly according to the antenna array arrangement scheme generated by this method, ensuring that the receiving antenna array and the transmitting antenna array can work collaboratively in the horizontal and vertical directions, and can detect the horizontal angle and pitch angle of the target simultaneously, so that the coverage range of the radio frequency signal emitted by the antenna can fully fit the morphological characteristics of the wind turbine blade; that is, the angle resolution and viewing angle of the 4D millimeter-wave MIMO radar are more suitable for detecting targets with slender shapes such as wind turbine blades, and a relatively high pitch angle resolution can be obtained, and at the same time, sidelobes can be effectively suppressed within the maximum pitch angle range of the millimeter-wave radar to avoid angle misjudgment; moreover, this 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, and finally achieve all-round accurate and reliable deformation detection of the wind turbine blade.

[0047] 2), the system provided by the present invention has significant advantages such as all-weather operation, high measurement accuracy, and safety and reliability. Specifically, the 4D millimeter-wave MIMO radar has strong penetration ability and can work stably under various climate conditions, including harsh weather such as strong winds, rain, snow, and haze. Different from 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. And due to the adoption of virtual aperture technology and advanced measurement algorithms, the system can provide extremely high measurement accuracy, ensuring that the data on the position, deformation, and health status of the detected wind turbine blade are very accurate, providing a reliable basis for the maintenance and fault warning of the wind turbine. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 is the flowchart of the method of the present invention;

[0049] Figure 2 is the test result diagram of Embodiment 2 of the present invention;

[0050] Figure 3 is the schematic diagram of the arrangement of the receiving antenna array of the present invention;

[0051] Figure 4 is the schematic diagram of the signal receiving virtual aperture of the antenna of the present invention;

[0052] Figure 5 is the schematic diagram of the arrangement of the transmitting antenna array of the present invention;

[0053] Figure 6Schematic diagram of the array arrangement of the antenna of the present invention;

[0054] Figure 7 Structural framework of the deformation detection system for the fan blade of the present invention;

[0055] Figure 8 Schematic diagram of the placement position of the millimeter-wave radar of the present invention. Specific implementation manners

[0056] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0057] Unless otherwise defined, the technical terms or scientific terms involved in this application should have the ordinary meanings understood by those with ordinary skills in the technical field to which this application belongs. The words such as "a", "one", "kind", "the" and the like involved in this application do not represent a quantity limitation and can represent a single or plural number. The terms "including", "comprising", "having" and any variations thereof involved in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or modules (units) is not limited to the listed steps or units, but may further include unlisted steps or units, or may further include other steps or units inherent to these processes, methods, products or devices. The terms "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 "plurality" involved in this application means two or more. "And / or" describes the association relationship of associated objects and indicates that three relationships may exist. For example, "A and / or B" may represent: A exists alone, A and B exist simultaneously, and B exists alone. The character " / " generally represents an "or" relationship between the associated objects before and after. The terms "first", "second", "third" and the like involved in this application are only used to distinguish similar objects and do not represent a specific order for the objects.

[0058] Embodiment 1

[0059] This embodiment aims to provide a method for detecting the deformation of fan blades using a 4D millimeter-wave MIMO radar. By transmitting radio frequency signals to the fan blades using the 4D millimeter-wave MIMO radar and performing signal processing on the radio frequency signals reflected by the fan blades, the detection of the deformation of the fan blades is completed, enabling more extensive detection and more accurate detection of blade deformation. Most current MIMO radars are applied to automotive scenarios, with their design focus mainly on a short detection range, a large field of view angle, and a relatively small difference in resolution between the horizontal and elevation directions, which is significantly different from the detection requirements of fan blades. In particular, the slender shape characteristics of fan blades result in detection requirements different from those in automotive scenarios. The detection of fan blades does not require a large field of view angle but rather focuses more on the accurate positioning of the target in the elevation direction, with relatively lower accuracy requirements in the horizontal direction. Moreover, existing radar systems, due to their large field of view angle and small difference in resolution between the horizontal and elevation directions, are difficult to meet the accuracy requirements for blade detection. Therefore, 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.

[0060] Specifically, the process of optimizing the antenna layout is as Figure 1 shown, including:

[0061] A1. Calculate the minimum spacing between two adjacent antenna elements and the antenna array aperture.

[0062] 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 elevation angle range and the elevation angle resolution of the radar, and the horizontal spacing between transmitting units and the horizontal aperture of the antenna are determined by the maximum detection horizontal angle range and the horizontal angle resolution of the radar.

[0063] Among them, the method for solving 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 is the same, both being: , where is the maximum detection angle of the millimeter-wave radar; is the signal wavelength of the millimeter-wave radar; is the minimum spacing between two adjacent antennas, and , represents the minimum horizontal spacing between two adjacent transmitting antennas, represents the minimum vertical spacing between two adjacent receiving antennas. And the method for solving the vertical aperture of the receiving antenna array and the horizontal aperture of the transmitting antenna array is also the same, both being: , where is the angle 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, represents the vertical aperture of the receiving antenna array.

[0064] Specifically, the solution process is as follows:

[0065] 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.

[0066] A12. Calculate the minimum vertical spacing between two adjacent receiving units based on the maximum detection pitch angle range. The expression is:

[0067] ,

[0068] where, 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.

[0069] A13. Calculate the vertical aperture of the receiving antenna array based on the pitch angle resolution of the millimeter-wave radar. The expression is:

[0070] ,

[0071] where, is the angle resolution of the millimeter-wave radar, is the signal wavelength of the millimeter-wave radar, is the vertical aperture of the receiving antenna array.

[0072] A14. Calculate the minimum vertical spacing between two adjacent receiving units based on the maximum detection horizontal angle range. The expression is:

[0073] ,

[0074] where, 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.

[0075] A15. Calculate the vertical aperture of the receiving antenna array based on the horizontal angle resolution of the millimeter-wave radar. The expression is:

[0076] ,

[0077] where, is the angle resolution of the millimeter-wave radar, is the signal wavelength of the millimeter-wave radar, is the vertical aperture of the transmitting antenna array.

[0078] A2. Determine the antenna arrangement of the receiving antenna array.

[0079] A21. Based on the limitation of the carrier chip, i.e., the number of receiving units that can be installed on the carrier chip of the antenna element, determine the number of receiving units in the receiving antenna array.

[0080] 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.

[0081] A23. The receiving units in the receiving antenna array are arranged non-uniformly and sparsely. With the goal of minimizing the sidelobe, determine the interval between adjacent receiving units in the same vertical layer, and the interval between adjacent receiving units is an integer multiple of the minimum vertical distance between two adjacent receiving antennas horizontally.

[0082] A3. Determine the antenna arrangement of the transmitting antenna array.

[0083] In practical applications, the fan blade is usually in a rotating state. When the blade enters the detection range of the radar, there is often a certain angle between the blade and the tower barrel. At this time, if the radar system can only detect the pitch angle and cannot obtain the horizontal angle of the blade, then calculating 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. With the goal of maximizing the number of antenna elements arranged horizontally in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array and minimizing the vertical distance between the horizontally arranged antenna elements and adjacent transmitting units, plan the arrangement of the transmitting antennas in the transmitting antenna array to simultaneously obtain the horizontal position and vertical position of the blade, so as to more accurately determine the three-dimensional coordinates of the blade. According to the obtained three-dimensional point cloud data of the blade to be detected, perform accurate deformation detection of the fan blade.

[0084] Specifically, the steps include:

[0085] A31. Based on the limitation of the horizontal carrier chip, determine the number of transmitting units in the transmitting antenna array.

[0086] A32. Each transmitting unit forms a separate column, and the horizontal interval between two adjacent transmitting units in the horizontal direction is the minimum horizontal distance between two adjacent transmitting antennas.

[0087] A33. Within the limitation of the actual antenna size, with the goal of minimizing the vertical distance between the horizontally arranged antenna elements and adjacent transmitting units in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array, determine the vertical interval between two adjacent transmitting units in the transmitting antenna array.

[0088] A34. Maximize the number of horizontally arranged antenna elements in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array within the limits of the actual antenna size, and determine the vertical aperture of the transmitting antenna array.

[0089] A35. Determine the vertical arrangement of the horizontal receiving units based on the horizontal and vertical spacings and the vertical aperture.

[0090] After the arrangement in steps A1 - A3, it can be ensured that within the maximum detection angle range of the radar, not only the angular resolution of the antenna is improved, but also the sidelobe effect can be suppressed, effectively avoiding angle misjudgment; and this design fully conforms to the morphological characteristics of the wind turbine blade (the blade is wider horizontally and longer in the pitch direction). According to the slender shape of the blade, during actual detection, the main focus is on the accurate positioning of the blade in the pitch direction, and less attention is paid to its accuracy in the horizontal direction. Therefore, by optimizing the antenna layout design, the field of view angle and resolution of the radar are more suitable for targets with the slender shape of the wind turbine blade, ensuring that the radar system can accurately obtain the three-dimensional point cloud data of the blade in space, not only improving the accuracy of radar imaging, but also better adapting to the actual detection requirements of the wind turbine blade.

[0091] After completing the optimization of the antenna layout of the 4D millimeter-wave MIMO radar, use the antennas of the optimized 4D millimeter-wave MIMO radar to transmit radio frequency signals to the wind turbine blade, and perform signal processing on the radio frequency signals reflected by the wind turbine blade, including:

[0092] S1. Convert the radio frequency signal reflected by the wind turbine blade into an intermediate frequency digital signal, and perform a fast Fourier transform in the distance domain on the intermediate frequency digital signal to obtain the distance information of the wind turbine blade.

[0093] S2. Perform a fast Fourier transform in the velocity domain on the intermediate frequency digital signal after the fast Fourier transform in the distance domain to obtain the velocity information of the wind turbine blade.

[0094] S3. Screen the wind turbine blades to be detected based on the velocity information, and obtain the phase differences of the received signals from different receiving units of the wind turbine blades to be detected for joint angle estimation, generating the angle information of the wind turbine blades to be detected, where the angle information includes horizontal angle information and pitch angle information.

[0095] S4. Generate three-dimensional point cloud data based on the distance information, velocity information, and angle information, and perform signal preprocessing to screen the valid point cloud data; among them, the form of the three-dimensional point cloud data is:

[0096] ,

[0097] R represents the distance information, represents the horizontal angle information, Indicates the pitch angle information.

[0098] Specifically, the signal preprocessing is to use a constant false alarm rate detection algorithm to adaptively filter the noise and interference in the three-dimensional point cloud data, determine the effective target point cloud, and output the filtered effective point cloud data.

[0099] S5. Compare the effective point cloud data with the pre-stored standard point cloud data and generate a detection result.

[0100] S51. Align the effective point cloud data and the standard point cloud data in the same coordinate system.

[0101] S52. Calculate the Euclidean distance between each point cloud in the aligned effective point cloud data and the corresponding point cloud in the standard point cloud data.

[0102] S53. Generate a deformation statistical 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 the point cloud with less deformation, green represents the point cloud with moderate deformation, and red represents the point cloud with significant deformation, generating a three-dimensional heat map for visually representing the deformation situation of each area on the blade surface; if the deformation deviation exceeds the preset range, the system will send an alarm signal and record the specific location of the abnormal deformation.

[0103] S54. Obtain the detection result based on the heat map, deformation statistical table, and alarm log.

[0104] In addition to steps S1 to S5, in this embodiment, the signal processing method further includes:

[0105] 1). Pulse accumulation processing, which accumulates the radar echo signals received from different antennas to improve the signal-to-noise ratio of the signal and enhance the detection ability of weak targets.

[0106] 2). Array calibration, which corrects the amplitude and phase inconsistencies of the antenna array to improve the angle estimation accuracy of the angle measurement algorithm, including:

[0107] B1. Obtain a reference signal. First, place a corner reflector 5 meters in front of the radar to obtain a reference signal. The pitch angle at this position is 0°, and the horizontal angle is 0°.

[0108] B2. Measure the array response. After installing the corner reflector, the radar antenna array starts to receive the reflected signals and records the amplitude and phase information of the signals received from each antenna.

[0109] B3. Calculation error. Due to factors such as the difference in feeder lengths between different antennas and the deviation in manufacturing processes, the actually received signals often show inconsistencies. To quantify these differences, it is necessary to compare the actually measured signals with the theoretically expected values, and then calculate the amplitude error and phase error of each antenna.

[0110] B4. Amplitude and phase correction. According to the results of error analysis, start the amplitude and phase correction of the array. First, perform amplitude correction. Taking the amplitude of a certain reference antenna as a reference, by correcting the amplitude errors of each antenna, ensure that the amplitudes of all antennas tend to be consistent. Subsequently, for phase correction, also taking the phase of a certain reference antenna as a standard, adjust the phases of each antenna to eliminate the phase errors and ensure that the phases of the signals received by all antennas are consistent.

[0111] 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 measurement data before correction, check whether the amplitudes and phases of the signals received by each antenna reach the expected ideal state. If the amplitudes and phases of all antennas are close to being consistent at the current moment, it indicates that the correction has been successful.

[0112] 3). Signal deblurring. For targets with range ambiguity, use a deblurring algorithm to restore the true range information.

[0113] Embodiment 2

[0114] In this embodiment, the above method is used to optimize the layout of the antenna arrangement of the three-channel transmitting MIMO radar. According to the actual measurement requirements, the maximum elevation measurement angle range of the millimeter-wave radar is set to and its elevation angle resolution is set to 5°. Then, through the calculation of formula and , it can be obtained that in this embodiment, the minimum vertical spacing between two adjacent receiving units in the receiving antenna array 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 its horizontal angle resolution is set to 10°. Then, through the calculation of formula and , it can be obtained that in this embodiment, the minimum horizontal spacing between two adjacent transmitting units in the transmitting antenna array is 1.9 wavelengths, and the horizontal aperture of the transmitting antenna array is 3.8 wavelengths.

[0115] 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. Four arrangements are selected, including:

[0116] Scheme 1: The first receiving unit is spaced 1 minimum distance from the second receiving unit, the first receiving unit is spaced 2 minimum distances from the third receiving unit, and the first receiving unit is spaced 6 minimum distances from the fourth receiving unit; Scheme 2: The first receiving unit is spaced 1 minimum distance from the second receiving unit, the first receiving unit is spaced 3 minimum distances from the third receiving unit, and the first receiving unit is spaced 6 minimum distances from the fourth receiving unit; Scheme 3: The first receiving unit is spaced 3 minimum distances from the second receiving unit, the first receiving unit is spaced 4 minimum distances from the third receiving unit, and the first receiving unit is spaced 6 minimum distances from the fourth receiving unit; Scheme 4: 4 receiving units are arranged linearly.

[0117] The test results are as follows Figure 2 As shown in , it can be found that when a non-uniform layout (such as Scheme 2) is adopted, the side lobes mainly appear in direction, while for scheme 1, the side lobe appears in . For detection scenarios, these two layouts are affected by side lobes and cause potential problems, because the detection area requires accurate detection of Blade targets within the range, and within this range, fan blades may appear in 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 three appear at 's location, while is almost the maximum angle that the blade can reach. Under normal circumstances, the blade will not reach this angle. Therefore, although ​There are sidelobes in the direction, but since the blades rarely appear in this angular range in the context of this embodiment, these sidelobes will not interfere with the detection results or cause misjudgment. This makes the antenna layout of Solution 3 more suitable for actual fan blade detection applications and can provide more accurate and reliable detection performance. Comparing with the linear array arrangement, it can be seen that the antenna optimized and arranged according to the method provided in the above embodiment can significantly reduce the 3dB beamwidth, improve the angular resolution, and is suitable for the fan blade detection task. In summary, the arrangement form of Solution 3 has a more stable effect, can more significantly reduce the 3dB beamwidth, improve the angular resolution, and at the same time Figure 3 effectively suppresses sidelobes within the

[0118] angular range to avoid angular misjudgment. Therefore, the original arrangement form of the receiving antenna array is as Figure 4 shown. Figure 5 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 elements in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array and minimizing the vertical distance between the horizontally arranged antenna elements and adjacent transmitting elements, plan the arrangement of the transmitting antenna array in the transmitting antenna array to simultaneously obtain the horizontal and vertical positions of the blade. First, determine the vertical distance between adjacent transmitting elements in the transmitting antenna array. The maximum number of horizontally arranged antenna elements in the virtual aperture array is 3, so when arranging, it is necessary to ensure that there is at least one row of antenna elements with a number of 3 in the horizontal direction of the virtual aperture. Based on the actual antenna size, the size of a single transmitting antenna in the vertical direction is 5 wavelengths, that is, the vertical distance between two transmitting antennas should be at least greater than 5 wavelengths, and the horizontal distance between two transmitting elements is 1.9 wavelengths, that is, this distance does not allow adjacent transmitting elements to be on the same horizontal line. Therefore, the arrangement of its virtual aperture array should be as

[0119] shown, and the corresponding arrangement of the transmitting antenna array should be as Figure 6As shown in the figure. 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 the pitch angle of the target at the same time, so that the coverage range of the RF signal transmitted by the antenna can fully fit the morphological characteristics of the fan blade; that is, the angle resolution and viewing angle of the 4D millimeter-wave MIMO radar are more suitable for the detection of targets with slender shapes such as fan blades, and a relatively high pitch angle resolution can be obtained. At the same time, the sidelobes can be effectively suppressed within the maximum pitch angle range of the millimeter-wave radar to avoid angle misjudgment; moreover, this method also uses the virtual aperture technology to comprehensively measure the horizontal angle and the pitch angle during the detection process, and obtain the horizontal position and vertical position of the fan blade at the same time, so as to more accurately determine the three-dimensional coordinates of the blade, so as to realize all-round accurate and reliable deformation detection of the fan blade.

[0120] Embodiment 3

[0121] This embodiment provides a 4D millimeter-wave MIMO radar fan blade deformation detection system, the framework of which is as Figure 7 shown, including a monolithic microwave integrated circuit, an STM32 control module, an FPGA signal processing module, a power amplifier and the antenna provided in Embodiment 2. The functions realized by each module are as follows:

[0122] The monolithic microwave integrated circuit is used to generate the RF signal of the millimeter-wave radar, and mix the RF 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.

[0123] The power amplifier is located between the monolithic microwave integrated circuit and the antenna, and is used to amplify the RF signal generated by the monolithic microwave integrated circuit.

[0124] The antenna includes a transmitting antenna array and a receiving antenna array, both of which adopt horizontally polarized microstrip antennas. The transmitting antenna array is used to transmit the RF signal amplified by the power amplifier, including multiple transmitting units, whose starting operating frequency is 79 GHz, the maximum bandwidth is 1 GHz, and the available frequency range is 79 GHz - 80 GHz; the receiving antenna array is used to receive the RF signal reflected by the fan blade to be detected and transmit it back to the monolithic microwave integrated circuit, including multiple receiving units, whose starting operating frequency is 79 GHz, the maximum bandwidth is 1 GHz, and the available frequency range is 79 GHz - 80 GHz. And due to the special arrangement form of the antenna array, a signal receiving virtual aperture will be formed in the horizontal direction between the transmitting antenna array and the receiving antenna array. This technology is used to detect the azimuth information in the vertical and horizontal directions and realize the comprehensive measurement of the horizontal angle and the pitch angle.

[0125] The STM32 control module is used to control the monolithic microwave integrated circuit to generate RF signals and output detection results.

[0126] 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.

[0127] In actual application, place the fan blade deformation detection system provided in this embodiment at the side of the tail of the nacelle of the wind turbine, so that the beam of the millimeter-wave radar is tilted towards the blade to facilitate obtaining the blade point cloud information. Its placement is as Figure 8 shown. After the placement is completed, send an instruction to the system to make the system execute the following steps:

[0128] C1. The STM32 control module causes the monolithic microwave integrated circuit to generate a radio frequency signal, and after amplifying the radio frequency signal by the power amplifier, it is sent by the transmitting antenna array to the fan blade to be detected.

[0129] After being amplified by the power amplifier, the maximum distance measured by the millimeter-wave radar is:

[0130] ,

[0131] where Pt is the signal transmission power, Gt is the transmitting antenna gain, Gr is the receiving antenna gain, RCS is the radar cross section, λ is the wavelength of the radar signal, and Smin is the minimum detectable power of the radar receiver.

[0132] C2. The receiving antenna array receives the radio frequency signal reflected by the fan blade to be detected and sends it to the monolithic microwave integrated circuit.

[0133] C3. The monolithic microwave integrated circuit converts the radio frequency signal reflected by the fan blade to be detected into an intermediate frequency analog signal, and after converting the intermediate frequency analog signal into an intermediate frequency digital signal, it is sent to the FPGA signal processing module.

[0134] C4. The FPGA signal processing module performs signal processing on the intermediate frequency digital signal, executes steps S1~S5 in Embodiment 1, as well as pulse accumulation processing, array correction, and signal deblurring processes, which will not be elaborated here.

[0135] C5. The STM32 control module obtains the detection result from the FPGA signal processing module and outputs it.

[0136] As described above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or replacements, and these modifications or replacements should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to 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, the carrier chip and the actual size of the antenna, the antenna arrangement of the transmitting antenna array is determined with the goal of maximizing the number of antenna units horizontally arranged in the MIMO virtual aperture array formed by the transmitting antenna array and the receiving antenna array; in detail, the method for determining the antenna arrangement of the transmitting antenna array is as follows: the number of transmitting units in the transmitting antenna array is determined based on the limitation of the carrier chip; each transmitting unit is arranged in a separate column, and the horizontal spacing between two adjacent transmitting units in the horizontal direction is the minimum horizontal spacing 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 vertical aperture of the transmitting antenna array is determined with 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; the vertical arrangement of the transmitting units is determined based on the vertical spacing and vertical aperture; 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 elements 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 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.

6. A 4D millimeter wave MIMO radar fan blade deformation detection method according to claim 5, 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.

7. The 4D millimeter wave MIMO radar fan blade deformation detection method according to claim 5, 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.

8. 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 7, 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.

9. The 4D millimeter wave MIMO radar fan blade deformation detection system according to claim 8, 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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