Method for synchronously measuring vibration mode slope of rocket by using multiple high-definition cameras

Abstract

The invention provides a method for synchronously measuring the vibration mode slope of a rocket by using a plurality of high-definition cameras. Belongs to the technical field of spaceflight structure vibration testing. According to the method, a plurality of high-definition cameras are arranged outside a rocket structure, image information of different local areas of the structure is collected respectively, and each camera is calibrated in advance so as to establish a corresponding relation between an angle in an image and an actual physical rotation angle. In the vibration process, the instantaneous rotation angle of each local area is extracted through an image processing means, phase comparison is carried out on the instantaneous rotation angle and a reference camera signal arranged at the tail of the rocket, and finally the vibration mode slope change condition in the structure direction is obtained through calculation. The method avoids high cost and high complexity of a traditional high-precision rate gyroscope, has the advantages of being non-contact, low in cost, easy to deploy and the like, and is suitable for rocket structure ground modal testing and flight vibration analysis.

Description

Technical Field

[0001] This invention belongs to the field of aerospace structure vibration testing technology, and more specifically, relates to a method for synchronously measuring the slope of a rocket's vibration mode using multiple high-definition cameras. More specifically, it involves extracting the instantaneous rotation angle of a rocket structure based on visual information, thereby achieving high-precision measurement of the vibration mode slope. This method represents an advanced testing technology for non-contact structural dynamic parameter identification. Background Art

[0002] With the development trend of lightweight and flexible rocket and spacecraft structures, the modal response of structures during flight is becoming increasingly complex. Accurate measurement of structural dynamic characteristics has become one of the core requirements for aircraft design, verification and in-service monitoring. Although traditional vibration testing solutions have been widely used for many years, their limitations are becoming more and more significant against the backdrop of increasing demand for high-frequency dynamic response, high spatial resolution and non-contact measurement. Among the structural vibration measurement methods commonly used in current engineering, fiber optic gyroscopes (FOGs) and mechanical rate gyroscopes are the core means of measuring rocket vibration modes. The technical principle is to indirectly obtain structural rotation angle information through integral calculations through changes in the angular velocity of the sensitive carrier. However, these two traditional methods have fundamental defects in engineering applications: While fiber-optic gyroscopes (FOGs) offer high precision and dynamic response capabilities, making them widely used in inertial navigation and attitude measurement systems, they suffer from several drawbacks: First, they are expensive, significantly increasing overall costs when deployed at multiple locations. Second, their large size and weight hinder their flexible deployment within limited space, such as rocket hulls. Third, their high power consumption makes them unsuitable for resource-constrained platforms. Furthermore, their sensitivity to ambient temperature fluctuations and mechanical shock limits their long-term stable operation during highly dynamic flight missions.

[0003] Mechanical gyroscopes face a series of inherent technical bottlenecks, including long startup times, complex structures, poor vibration resistance, significant impacts on accuracy and stability due to friction and drift, frequent maintenance, and limited service life. Furthermore, their signal bandwidth is insufficient to capture high-frequency vibration responses, making it difficult to meet the stringent high-speed and high-frequency dynamic response testing requirements of modern spacecraft.

[0004] In recent years, non-contact measurement technology based on computer vision has experienced rapid development. By capturing image sequences with high-frame-rate cameras and combining image processing with pose estimation algorithms, dynamic rotation angle extraction of structures can be achieved, providing a new solution for modal slope measurement. Summary of the Invention

[0005] This invention aims to address the problems of the prior art by proposing a method for synchronously measuring the slope of a rocket's vibration mode using multiple high-definition cameras. This method enables non-contact measurement and slope calculation of the instantaneous rotational angle distribution of a rocket structure during vibration, offering advantages such as high precision, low cost, and ease of deployment.

[0006] The present invention is achieved through the following technical solution. The present invention proposes a method for synchronously measuring the slope of a rocket vibration mode using multiple high-definition cameras. The method arranges multiple high-definition cameras outside the rocket structure to respectively collect image information of different local areas of the structure, and pre-calibrates each camera to establish a correspondence between the angle in the image and the actual physical rotation angle; during the vibration process, the instantaneous rotation angle of each local area is extracted by image processing means, and phase comparison is performed with the reference camera signal set at the tail of the rocket, and finally the change in the vibration mode slope along the structural direction is calculated.

[0007] Furthermore, each camera is fixedly installed at a different observation angle on the outside of the rocket structure; one of the cameras is located at the tail of the rocket as a global phase reference, and the remaining cameras are distributed in the middle of the rocket and the key structural areas at the connection between the shell and segments; the camera's shooting frame rate is set to ≥100fps, and the resolution is ≥1920×1080; a recognizable logo pattern is sprayed on the surface of the rocket as a visual corner recognition object.

[0008] Furthermore, each camera obtains its internal parameters and installation posture through an offline calibration process; the horizontal line direction uses the gravity reference surface or a dedicated calibration plate as a reference to establish the relationship between the inclination angle in the image and the physical rotation angle.

[0009] Furthermore, the inclination angle of the structural marker is extracted through an image processing algorithm and converted into an instantaneous rotation angle relative to the initial state.

[0010] Furthermore, each camera outputs a time series angle signal, and the time domain phase of each signal is compared with the reference camera signal to obtain the relative phase response curve of each local point.

[0011] Furthermore, the comparison method is specifically as follows: Perform Hilbert transform on each angle signal to extract the instantaneous phase; By calculating the relative phase difference curve, the relative response delay of each measurement point to the reference point is obtained; If the signal is periodic, further analyze its main frequency response phase spectrum.

[0012] Furthermore, based on the known distance between measurement points, the rotation angle differences between adjacent points are differentially processed to obtain the angular gradient of the structure, that is, the distribution of the mode slope. This information is used for rocket modal identification, structural health assessment and control parameter update.

[0013] Furthermore, all cameras are connected to the same synchronization system, which can be GPS clock synchronization, external hardware triggering or software comparison synchronization mechanism based on image frame timestamps, with the error controlled within 1ms.

[0014] The present invention also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements the steps of a method for synchronously measuring the slope of a rocket vibration mode using multiple high-definition cameras.

[0015] The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of a method for synchronously measuring the slope of a rocket vibration mode using multiple high-definition cameras.

[0016] Beneficial effects of the present invention: The present invention proposes a method for synchronously measuring the slope of a rocket's vibration mode using multiple high-definition cameras. This method arranges multiple high-definition cameras on the outside of the rocket structure to collect image information of different local areas of the structure, and pre-calibrates each camera to establish a correspondence between the angle in the image and the actual physical angle of rotation. During the vibration process, the instantaneous angle of rotation of each local area is extracted by image processing, and a phase comparison is performed with the reference camera signal set at the tail of the rocket. Finally, the change in the slope of the vibration mode along the direction of the structure is calculated. This method avoids the high cost and high complexity of traditional high-precision rate gyroscopes, and has the advantages of non-contact, low cost, and easy deployment. It is suitable for ground modal testing and flight vibration analysis of rocket structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0018] Figure 1 This is a schematic diagram of the overall architecture of the system implemented by the method described in the present invention, showing that multiple high-definition cameras are arranged in different parts of the rocket structure, with the tail camera as the reference.

[0019] Figure 2 This is a diagram of the principle of image angle measurement, showing the measured relationship between the inclination angle of the structure in the image and the horizontal line of the picture after camera calibration.

[0020] Figure 3 This is the flow chart for modal slope calculation, including steps such as image acquisition, angle extraction, phase alignment, and slope calculation.

[0021] Figure 4 This is a schematic diagram of the system synchronization mechanism implemented by the method of the present invention, illustrating that GPS synchronization or external trigger signals are used to ensure that the acquisition time of each camera is consistent. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] Specifically, combined Figure 1-Figure 4 The present invention proposes a method for synchronously measuring the slope of a rocket's vibration mode using multiple high-definition cameras. The method arranges multiple high-definition cameras outside the rocket structure to collect image information of different local areas of the structure, and pre-calibrates each camera to establish a correspondence between the angle in the image and the actual physical rotation angle; during the vibration process, the instantaneous rotation angle of each local area is extracted by image processing means, and phase comparison is performed with the reference camera signal set at the tail of the rocket, and finally the change in the vibration mode slope along the structural direction is calculated.

[0024] Each camera is fixedly installed at a different observation angle on the outside of the rocket structure; one of the cameras (for example, camera 1) is located at the tail of the rocket as a global phase reference, and the remaining cameras are distributed in the middle of the rocket and in key structural areas at the connection between the shell and segments; the camera's shooting frame rate is set to ≥100fps and the resolution is ≥1920×1080; a recognizable logo pattern is sprayed on the surface of the rocket as a visual corner recognition object.

[0025] Each camera obtains its internal parameters (focal length, principal point position, etc.) and installation posture through an offline calibration process; the horizontal line direction uses the gravity reference surface or a dedicated calibration plate as a reference to establish the relationship between the inclination angle in the image and the physical rotation angle.

[0026] like Figure 2 The figure shows the principle of angle measurement using camera images. Image processing algorithms (such as Canny edge detection and Hough transform, feature matching, or deep neural network keypoint recognition) are used to extract the inclination of structural landmarks and convert it into an instantaneous rotation angle relative to the initial state.

[0027] Each camera outputs a time series angle signal. The time domain phase of each signal is compared with the reference camera signal (for example, using Hilbert transform to extract the instantaneous phase) to obtain the relative phase response curve of each local point.

[0028] The specific comparison method is: Perform Hilbert transform on each angle signal to extract the instantaneous phase; By calculating the relative phase difference curve, the relative response delay of each measurement point to the reference point is obtained; If the signal is periodic, further analyze its main frequency response phase spectrum.

[0029] Based on the known distance between measurement points, the rotation angle differences of adjacent points are differentially processed to obtain the angular gradient of the structure, that is, the distribution of the modal slope. This information is used for rocket mode identification, structural health assessment and control parameter update.

[0030] like Figure 4 As shown in the figure, to ensure the synchronization of image acquisition, all cameras are connected to the same synchronization system, which can be GPS clock synchronization, external hardware triggering, or a software comparison synchronization mechanism based on image frame timestamps, with the error controlled within 1ms.

[0031] Example The method of the present invention is further described in detail below with reference to the accompanying drawings.

[0032] The present invention proposes a method for synchronously measuring the slope of a rocket's vibration mode using multiple high-definition cameras. The method arranges multiple high-definition cameras outside the rocket structure to respectively collect image information of different local areas of the structure, and pre-calibrates each camera to establish a correspondence between the angle in the image and the actual physical rotation angle; during the vibration process, the instantaneous rotation angle of each local area is extracted by image processing means, and a phase comparison is performed with the reference camera signal set at the tail of the rocket, and finally the change in the vibration mode slope along the structural direction is calculated.

[0033] 1. System composition: Figure 1 and Figure 4 As shown, the system implemented by the method of the present invention is composed of multiple high-definition industrial cameras. The cameras adopt a frame rate of ≥100 fps and a resolution of ≥1920×1080, and have high dynamic range (HDR) imaging capabilities to ensure clear imaging performance even in strong light interference environments such as rocket launches.

[0034] Camera 1 is located at the tail of the rocket, aimed at the engine nozzle area, and serves as a global reference phase reference source.

[0035] Camera 2 and Camera 3 are installed in the high modal response area in the middle section of the rocket body to achieve full coverage perception of the structural response.

[0036] To improve the robustness of image recognition, visible high-contrast marking patterns (such as checkerboards, ArUco codes or special geometric figures) are sprayed at specific locations on the rocket surface as feature references for subsequent image inclination extraction and tracking.

[0037] 2. Camera calibration and attitude determination: To ensure accurate measurement of the structure's rotation angle, each camera must be precisely calibrated offline, including the following steps: Internal parameter calibration: Use Zhang Zhengyou calibration method or structured cursor calibration board to obtain internal imaging parameters such as focal length, principal point, and distortion coefficient.

[0038] External parameter and attitude calibration: Use a laser total station, IMU reference module or a set of feature points with known positions, combined with a three-dimensional reconstruction algorithm, to solve the spatial transformation matrix (R, t) of the camera coordinate system relative to the rocket body coordinate system.

[0039] Tilt angle reference establishment: Using a gravity reference surface, a level, or a calibration plate with tilt angle information, a mapping function between the image pixel coordinate system and the physical world rotation angle is established in the initial static state to achieve accurate conversion of image tilt angle to structural rotation angle.

[0040] 3. Image corner extraction: Figure 2 The following figure shows the principle of angle measurement using camera images. During flight or ground testing, after the camera captures the image, various image processing algorithms are used to extract the tilt angle information of the structural landmark: Basic method: grayscale the image, perform Canny edge detection, Hough line transform, and extract the main edge direction.

[0041] Feature matching method: Use feature point detection and matching algorithms such as SIFT / SURF / ORB to track key points in the pattern and calculate its posture transformation.

[0042] Deep learning method: Through pre-trained lightweight CNN or HRNet structure network, it detects and regresses pattern key corner points, which is suitable for tilt angle extraction under low contrast or complex background conditions.

[0043] The extracted image inclination value can be compared with the image of the initial static state to calculate the instantaneous rotation angle value of the structure at that position at the current moment.

[0044] 4. Phase comparison: The angle signals of each camera form a time series, and are uniformly aligned and compared with the reference angle signal obtained by camera 1. The comparison method is as follows: Perform Hilbert transform on each angle signal to extract the instantaneous phase; By calculating the relative phase difference curve, the relative response delay of each measurement point to the reference point can be obtained; If the signal is periodic (such as under vibration excitation), its main frequency response phase spectrum can be further analyzed.

[0045] This comparison method supports a variety of signal preprocessing strategies, such as bandpass filtering, Savitzky-Golay smoothing, and noise suppression, to improve the accuracy of time-domain phase recognition.

[0046] 5. Modal Slope Calculation: Based on the known distance between measurement points, the angle differences between adjacent points are differentially processed to obtain the structure's angular gradient, or modal slope distribution. This information is used for rocket modal identification, structural health assessment, and control parameter updates.

[0047] 6. Synchronization mechanism: such as Figure 4 As shown in the figure, to ensure the synchronization of image acquisition, all cameras are connected to the same synchronization system, which can be GPS clock synchronization, external hardware triggering, or a software comparison synchronization mechanism based on image frame timestamps, with the error controlled within 1ms.

[0048] The present invention also proposes an electronic device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, it implements the steps of a method for synchronously measuring the slope of a rocket vibration mode using multiple high-definition cameras.

[0049] The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of a method for synchronously measuring the slope of a rocket vibration mode using multiple high-definition cameras.

[0050] The memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. The non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct RAM bus RAM (DR RAM). It should be noted that the memory used in the methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0051] In the above embodiments, all or part of the embodiments can be implemented using software, hardware, firmware, or any combination thereof. When implemented using software, all or part of the embodiments can be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that can be accessed by a computer, or a data storage device such as a server or data center that integrates one or more available media. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a high-density digital video disc (DVD)), or a semiconductor medium (eg, a solid state disc (SSD)).

[0052] During implementation, each step of the above method can be completed by an integrated logic circuit of the hardware in the processor or by instructions in the form of software. The steps of the method disclosed in conjunction with the embodiments of the present application can be directly embodied as being executed by a hardware processor, or can be executed by a combination of hardware and software modules in the processor. The software module can be located in a storage medium mature in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in conjunction with its hardware. To avoid repetition, it will not be described in detail here.

[0053] It should be noted that the processor in the embodiments of the present application can be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above-described method embodiments can be completed by hardware integrated logic circuits in the processor or by software instructions. The above-described processor can be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic device, or discrete hardware components. The methods, steps, and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor can be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of the present application can be directly implemented and executed by a hardware decoding processor, or by a combination of hardware and software modules in the decoding processor. The software modules can be located in a storage medium well-known in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, etc. The storage medium is located in the memory, and the processor reads the information in the memory and, in conjunction with its hardware, completes the steps of the above-described method.

[0054] The above is a detailed introduction to the method proposed in the present invention for synchronously measuring the slope of a rocket vibration mode using multiple high-definition cameras. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for synchronously measuring the slope of a rocket's vibration mode using multiple high-definition cameras, characterized in that: The method arranges multiple high-definition cameras on the outside of the rocket structure to collect image information of different local areas of the structure, and pre-calibrates each camera to establish a correspondence between the angle in the image and the actual physical rotation angle. During the vibration process, the instantaneous rotation angle of each local area is extracted through image processing, and phase comparison is performed with the reference camera signal set at the tail of the rocket. Finally, the change in the slope of the vibration mode along the structural direction is calculated.

2. The method according to claim 1, characterized in that Each camera is fixedly installed on the outside of the rocket structure at different observation angles; one of the cameras is located at the tail of the rocket as a global phase reference, and the remaining cameras are distributed in the middle of the rocket and in key structural areas at the connection between the shell and segments; the camera's shooting frame rate is set to ≥100fps, and the resolution is ≥1920×1080; a recognizable logo pattern is sprayed on the surface of the rocket as a visual corner recognition object.

3. The method according to claim 1, characterized in that Each camera obtains its internal parameters and installation posture through an offline calibration process; the horizontal line direction uses the gravity reference surface or a dedicated calibration plate as a reference to establish the relationship between the inclination angle in the image and the physical rotation angle.

4. The method according to claim 1, wherein The inclination angle of the structural marker is extracted through image processing algorithms and converted into an instantaneous rotation angle relative to the initial state.

5. The method according to claim 1, wherein Each camera outputs a time series angle signal. The time domain phase of each signal is compared with the reference camera signal to obtain the relative phase response curve of each local point.

6. The method according to claim 5, characterized in that The specific comparison method is: Perform Hilbert transform on each angle signal to extract the instantaneous phase; By calculating the relative phase difference curve, the relative response delay of each measurement point to the reference point is obtained; If the signal is periodic, further analyze its main frequency response phase spectrum.

7. The method according to claim 1, characterized in that Based on the known distance between measurement points, the rotation angle differences of adjacent points are differentially processed to obtain the angular gradient of the structure, that is, the distribution of the modal slope. This information is used for rocket mode identification, structural health assessment and control parameter update.

8. The method according to claim 1, characterized in that All cameras are connected to the same synchronization system, which can be GPS clock synchronization, external hardware triggering or software comparison synchronization mechanism based on image frame timestamps, with the error controlled within 1ms.

9. An electronic device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 8 are implemented.

10. A computer-readable storage medium for storing computer instructions, characterized in that: When the computer instructions are executed by a processor, the steps of the method according to any one of claims 1 to 8 are implemented.

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