A vibration isolation platform angular displacement measurement method, device and system

Abstract

The present invention discloses a method, device, and system for measuring the angular displacement of a vibration isolation platform. The method obtains video data of a vibration isolation platform undergoing a vibration test, extracts the video data frame by frame to obtain each frame image and its corresponding shooting time, processes each frame image to obtain the image pixel coordinates of the center of gravity of each target image in an image pixel coordinate system, transforms the image pixel coordinates to obtain the world coordinates of each target in a world coordinate system, and calculates the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system based on the world coordinates. The method solves the technical problems that the angular displacement test of the vibration isolation platform cannot provide data support for the optimized design of the angular displacement response, and that errors are easily introduced during the data processing process due to improper time domain registration.

Description

Technical Field

[0001] The present invention belongs to the field of vibration testing technology, and in particular relates to a method, device and system for measuring the angular displacement of a vibration isolation platform. Background Art

[0002] Aerial cameras, mounted on aircraft, capture and record optical radiation from the Earth's surface and atmosphere. Aircraft flight generates complex mechanical excitations, including atmospheric drag and aerodynamic forces (turbulence and flutter), excitation forces caused by aerodynamic and mechanical imbalances, engine excitation forces, and excitation forces caused by rotor wake acting on other components. These excitations are transmitted to the aerial camera, causing overall vibration and relative vibration of its components. These vibrations affect image quality. The primary mechanism of action is that vibration causes jitter in the camera's line of sight, introducing image motion during exposure and resulting in blurred images.

[0003] Vibration can be categorized into linear and angular vibrations based on their displacement characteristics. Previous studies have shown that angular vibration has a far greater impact on image quality than linear vibration. Therefore, during the development phase, conducting vibration tests on the aerial camera vibration isolation platform, along with simultaneous angular displacement testing, is crucial for verifying the isolation platform's performance and optimizing its design.

[0004] The current angular displacement test schemes for vibration isolation platforms are divided into two categories: indirect and direct. Indirect method: Install an aerial camera on the vibration isolation platform and take pictures of specific targets. By analyzing the degradation of image quality, the performance of the vibration isolation platform can be judged. This method reflects the comprehensive results of multiple factors such as angular vibration, linear vibration and vibration of the internal structure of the aerial camera, and cannot provide direct data for the optimization design of angular displacement response. Direct method: Install a plane mirror on the vibration isolation platform and use an autocollimator to monitor. This method can directly measure angular displacement, but each autocollimator can only monitor the angular displacement in two directions at a certain point on the vibration isolation platform. In order to reflect the overall situation of the vibration isolation platform and establish a quantitative relationship between the vibration input and output ends, multiple autocollimators are needed to monitor multiple directions of multiple measuring points at the same time. The time domain alignment of data from multiple autocollimators will introduce test errors. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for measuring the angular displacement of a vibration isolation platform. A high-speed camera is used to shoot all targets on the vibration isolation platform, and by processing the video data obtained from the shooting, the angular displacement of the input and output ends of the vibration isolation platform relative to the world coordinate system in the three-axis directions is accurately calculated. This solves the technical problems in the prior art that the angular displacement test of the vibration isolation platform cannot provide data support for the optimization design of the angular displacement response and that errors are easily introduced during the data processing process due to improper time domain alignment.

[0006] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for measuring the angular displacement of a vibration isolation platform, which comprises:

[0008] Acquiring video data of a vibration test performed on a vibration isolation platform, wherein the vibration isolation platform is provided with a plurality of targets;

[0009] Extracting the video data frame by frame to obtain each frame image and its corresponding shooting time, wherein each frame image includes a target image of each target at the corresponding shooting time;

[0010] Performing image processing on each frame of the image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system;

[0011] Performing coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system;

[0012] According to the world coordinates, the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system is calculated.

[0013] In one embodiment of the present invention, obtaining video data of a vibration test performed on a vibration isolation platform includes:

[0014] The vibration isolation platform undergoing the vibration test is continuously photographed using a high-speed camera to obtain video data of the vibration isolation platform undergoing the vibration test, wherein the photographing time of the high-speed camera includes the duration of the entire vibration test.

[0015] In one embodiment of the present invention, performing image processing on each frame of the image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system includes:

[0016] Image processing is performed on each frame of the image, and the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system are calculated using a grayscale centroid method, wherein each target image is composed of a plurality of pixel points.

[0017] In one embodiment of the present invention, performing coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system includes:

[0018] Obtaining the coordinate transformation relationship between the world coordinates of the target and its image pixel coordinates;

[0019] The world coordinates of each target in the world coordinate system are calculated based on the image pixel coordinates and the coordinate transformation relationship.

[0020] In one embodiment of the present invention, the coordinate axis direction of the world coordinate system is consistent with the coordinate axis direction of the vibration isolation platform coordinate system;

[0021] The vibration isolation platform coordinate system is established in the following way:

[0022] The direction in which the aircraft simulated by the vibration test platform points vertically to the ground is the +Z direction, the flight direction of the aircraft simulated by the vibration test platform is the +X direction, and the +Y direction is determined according to the right-hand rule to establish the vibration isolation platform coordinate system.

[0023] In one embodiment of the present invention, the step of calculating the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system according to the world coordinate system includes:

[0024] According to the world coordinates, calculate the angle between the line connecting any two targets and the world coordinate system;

[0025] The angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system is calculated based on the angle between the line connecting the two arbitrary targets and the world coordinate system.

[0026] Based on the same inventive concept, another embodiment of the present invention further provides a vibration isolation platform angular displacement measurement device, the device comprising:

[0027] A data acquisition module, configured to acquire video data of a vibration test performed on a vibration isolation platform, wherein the vibration isolation platform is provided with a plurality of targets;

[0028] a data extraction module, configured to extract the video data frame by frame to obtain each frame of image and its corresponding shooting time, wherein each frame of image includes a target image of each target at a corresponding shooting time;

[0029] a data processing module, configured to perform image processing on each frame of the image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system;

[0030] The data calculation module is used to perform coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system, and calculate the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system based on the world coordinates.

[0031] Based on the same inventive concept, another embodiment of the present invention further provides a vibration isolation platform angular displacement measurement system, comprising: a vibration test bench, an aerial camera or a simulated load thereof, a vibration isolation platform, a plurality of target adapters, a plurality of targets, a plurality of acceleration sensors, a high-speed camera, and a computer;

[0032] The vibration test bench is used to simulate the vibration environment effects of a real aircraft flight;

[0033] The vibration isolation platform includes an upper plate of the vibration isolation platform, a plurality of vibration isolators and a lower plate of the vibration isolation platform. The upper plate of the vibration isolation platform and the lower plate of the vibration isolation platform are fixedly connected via a plurality of vibration isolators. The aerial camera or its simulated load is installed on the upper plate of the vibration isolation platform, and the lower plate of the vibration isolation platform is installed on the working table of the vibration test bench.

[0034] A plurality of target adapters are respectively installed on the first side and the second side of the vibration isolation platform, and a corresponding target is installed on each target adapter, wherein the first side and the second side are perpendicular to each other;

[0035] The plurality of acceleration sensors are installed on the working surface of the vibration test platform near the lower plate of the vibration isolation platform to measure the vibration acceleration during the vibration test;

[0036] The high-speed camera is installed on the symmetry axis of the first side and the second side of the vibration isolation platform, and is used to shoot a video of the vibration isolation platform performing a vibration test;

[0037] The computer is used to solve the angular displacement of the vibration isolation platform by using the vibration isolation platform angular displacement measurement method as described in any of the above embodiments.

[0038] In one embodiment of the present invention, the target plane of the target is approximately perpendicular to the optical axis of the high-speed camera.

[0039] In one embodiment of the present invention, the shooting frame rate of the high-speed camera is higher than twice the highest frequency of the input vibration of the vibration test platform.

[0040] As described above, the present invention provides a method for measuring the angular displacement of a vibration isolation platform. The method obtains video data of a vibration test performed on the vibration isolation platform, wherein the vibration isolation platform is provided with a plurality of targets, extracts the video data frame by frame, and obtains each frame image and its corresponding shooting time, wherein each frame image includes the target image of each target at the corresponding shooting time, performs image processing on each frame image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system, performs coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system, and calculates the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system based on the world coordinates. The method uses a high-speed camera for shooting, and can calculate the angular displacement data of multiple measuring points at the input and output ends of the vibration isolation platform at one time, including frequency and amplitude characteristics, thereby greatly improving the test efficiency. In addition, since only one high-speed camera is used to shoot all targets on the vibration isolation platform, the relative spatial position data of each target is strictly matched in the time domain, and no error is introduced during the data processing due to time domain registration. In addition, by increasing the number of targets and increasing the span between targets, the influence of some system noise and random noise can be suppressed, thereby improving the accuracy of angular displacement measurement. At the same time, appropriate target adapters are used between the side surfaces of the upper and lower plates of the vibration isolation platform and the target, so that the target plane is approximately perpendicular to the optical axis of the high-speed camera, thereby making the target image of the target have a basically symmetrical grayscale distribution, which facilitates the determination and measurement of the characteristic dimensions of the target along the axis of the camera coordinate system, and the image of the target does not deform during the test. In addition, the size of the target allows its image to occupy multiple pixels rather than an isolated pixel, so the grayscale centroid method can be used to calculate the position of the center of gravity of each target image in the image pixel coordinate system. Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 A schematic flow chart of a method for measuring angular displacement of a vibration isolation platform provided as an exemplary embodiment of the present application.

[0043] Figure 2 A schematic structural diagram of an angular displacement measurement system for a vibration isolation platform provided in an exemplary embodiment of the present application.

[0044] Figure 3 A schematic diagram of the angular displacement input curve and output curve of the vibration isolation platform provided by an exemplary embodiment of the present application.

[0045] Figure 4 A schematic structural diagram of an angular displacement measurement device for a vibration isolation platform is provided in accordance with another exemplary embodiment of the present application.

[0046] The reference numerals are as follows:

[0047] 1 Vibration test platform

[0048] 2 Aerial camera or its simulated load

[0049] 3 Vibration isolation platform

[0050] 31 Vibration isolation platform upper plate

[0051] 32 Vibration Isolators

[0052] 33 Vibration isolation platform lower plate

[0053] 4 Target adapter

[0054] 5 Targets

[0055] 6 High-speed cameras

[0056] 7 Computer

[0057] 8 Accelerometer DETAILED DESCRIPTION

[0058] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0059] It should be noted that the illustrations provided in the following embodiments are merely schematic illustrations of the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be changed arbitrarily, and the component layout may also be more complex.

[0060] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the embodiments of the present invention may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring the embodiments of the present invention.

[0061] In order to solve the technical problems in the prior art that the angular displacement test of the vibration isolation platform cannot provide data support for the optimization design of the angular displacement response and that errors are easily introduced during the data processing due to improper time domain registration, the present invention provides a vibration isolation platform angular displacement measurement method. A high-speed camera is used to shoot all targets on the vibration isolation platform. By processing the captured video data, the angular displacement of the input and output ends of the vibration isolation platform relative to the world coordinate system in the three-axis directions is accurately calculated, and errors due to time domain registration are not introduced during the data processing. Please refer to Figure 1 As shown, the vibration isolation platform angular displacement measurement method includes the following steps:

[0062] S100: Acquiring video data of a vibration test performed on a vibration isolation platform, wherein the vibration isolation platform is provided with a plurality of targets;

[0063] S200: extracting the video data frame by frame to obtain each frame image and its corresponding shooting time, wherein each frame image includes a target image of each target at a corresponding shooting time;

[0064] S300: performing image processing on each frame of the image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system;

[0065] S400: performing coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system;

[0066] S500: Calculate and obtain the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system according to the world coordinate system.

[0067] The steps of the above-mentioned vibration isolation platform angular displacement measurement method will be discussed in detail below.

[0068] Before executing step S100, a test platform needs to be built. Figure 2As shown, in an exemplary embodiment of the present application, the test platform includes a vibration test bench 1, an aerial camera or its simulated load 2, a vibration isolation platform 3, several target adapters 4, several targets 5, a high-speed camera 6, a computer 7, and several acceleration sensors 8. The vibration isolation platform 3 further includes an upper plate 31, vibration isolators 32, and a lower plate 33. The upper plate 31 and the lower plate 33 are fixedly connected via several vibration isolators 32. The construction process of the test platform mainly includes the following steps:

[0069] An aerial camera or its simulated load 2 is mounted on the upper plate 31 of the vibration isolation platform. It should be noted that if a simulated load is used instead of a real aerial camera, the simulated load should have the same mass and appearance structural characteristics as the actual aerial camera.

[0070] The vibration isolation platform 3 is placed upright and centrally installed on the working surface of the vibration test bench 1 , so that the lower plate 33 of the vibration isolation platform is fixed to the working surface of the vibration test bench 1 .

[0071] A vibration isolation platform coordinate system is established for the vibration isolation platform 3. The direction perpendicular to the ground, as simulated by the vibration test platform 1, is defined as the +Z direction. The direction of flight, as simulated by the vibration test platform 1, is defined as the +X direction. The +Y direction is determined using the right-hand rule. The X and Y sides of the vibration isolation platform 3 are determined based on the established vibration isolation platform coordinate system.

[0072] The high-speed camera 6 is mounted on the symmetric axes of the X and Y sides of the vibration isolation platform 3. It should be noted that the mounting position of the high-speed camera 6 must ensure that it can clearly capture both the X and Y sides of the vibration isolation platform 3. It is worth noting that the high-speed camera 6 must be mounted securely and reliably, and must be effectively isolated from any potential interference from the excitation source of the vibration test bench 1.

[0073] At least two targets 5 are mounted on the X and Y sides of the upper plate 31 and the lower plate 31, respectively. To ensure that the target plane is perpendicular to the optical axis of the high-speed camera 6, target adapters 4 are used to connect the targets 5 to the side surfaces of the upper plate 31 and the lower plate 33. It should be noted that the total Y span of the X-side targets of the upper plate 31 and the lower plate 33 should be maximized. The X-side targets 5 of the upper plate 31 are numbered sequentially according to the +Y direction of the vibration isolation platform coordinate system as XA1, XA2, ..., XAn. The X-side targets of the lower plate 33 are numbered sequentially according to the +Y direction of the vibration isolation platform coordinate system as XB1, XB2, ..., XBn. The total X-direction span of the Y-side targets of the upper plate 31 and the lower plate 33 of the vibration isolation platform should be increased as much as possible, and the Y-side targets 5 of the upper plate 31 of the vibration isolation platform are numbered in sequence as YA1, YA2...YAn according to the +X direction of the vibration isolation platform coordinate system, and the Y-side targets of the lower plate 33 of the vibration isolation platform are numbered in sequence as YB1, YB2...YBn according to the +X direction of the vibration isolation platform coordinate system.

[0074] Several accelerometers 8 are installed on the work surface of the vibration test bench 1 near the lower plate 33 of the vibration isolation platform to measure the input vibration acceleration to achieve closed-loop feedback. It should be noted that the measurement direction of the accelerometers 8 should be consistent with the vibration direction of the vibration test bench 1.

[0075] It should be noted that by increasing the number of targets 5 and increasing the spacing between targets 5, the effects of some system noise and random noise can be suppressed, improving the accuracy of subsequent angular displacement measurements of the vibration isolation platform. Furthermore, because a single high-speed camera 6 is used to capture all targets 5, the relative spatial position data of each target 5 is strictly matched in the time domain. Therefore, errors introduced during data processing due to time-domain registration are eliminated.

[0076] After the above test platform is built, the vibration test of the vibration isolation platform begins.

[0077] First, step S100 is executed, that is, video data of a vibration test performed on a vibration isolation platform is acquired, wherein the vibration isolation platform is provided with a plurality of targets.

[0078] In an exemplary embodiment of the present application, obtaining video data of a vibration isolation platform undergoing a vibration test includes: continuously photographing the vibration isolation platform undergoing the vibration test using a high-speed camera to obtain the video data of the vibration isolation platform undergoing the vibration test, wherein the photographing time of the high-speed camera includes the duration of the entire vibration test. In addition, the photographing frame rate of the high-speed camera is higher than twice the highest frequency of the vibration input to the vibration test platform.

[0079] For details, please refer to Figure 2 As shown, when the vibration test is performed, the high-speed camera 6 continuously shoots the X side and Y side of the vibration isolation platform 3, and the shooting time covers the duration of the entire vibration test. After the shooting is completed, the shot video data is uploaded to the computer 7 for storage.

[0080] Next, step S200 is executed, that is, the video data is extracted frame by frame to obtain each frame image and its corresponding shooting time, wherein each frame image includes the target image of each target at the corresponding shooting time.

[0081] It should be noted that before processing each frame of image, the coordinate system of the target and the target image needs to be defined based on the basic principles of photogrammetry.

[0082] The image pixel coordinate system (u, v) is a rectangular coordinate system established with the upper left corner of each extracted image frame as the origin and pixels as the coordinate unit. The coordinates of an image point in the image pixel coordinate system are expressed as (U, V), where U and V represent the column and row number of the image point in the digital image, respectively.

[0083] The image physical coordinate system (x, y) is a rectangular coordinate system established in millimeters, with the intersection of the high-speed camera's optical axis and the image plane as its origin. Its x and y axes are parallel to the axes of the image pixel coordinate system. The coordinates of an image point in the image physical coordinate system are expressed as (X, Y).

[0084] Camera coordinate system (x c ,y c ,z c ), whose origin is the optical center of the high-speed camera, z c The axis coincides with the optical axis of the high-speed camera, and the photographic direction is taken as the positive direction. c 、y c The axis is parallel to the x and y axes of the image physical coordinate system. The coordinates of a point in the camera coordinate system are expressed as (X C ,Y C ,Z C ).

[0085] World coordinate system (x w ,y w ,z w ), a three-dimensional space coordinate system can be arbitrarily defined by the user so that its coordinate axis direction is consistent with the vibration isolation platform coordinate system. The coordinates of a point in the world coordinate system are expressed as (X W ,Y W ,Z W ).

[0086] It should be noted that, in this embodiment, the origin of the world coordinate system coincides with the origin of the camera coordinate system. c axis and z c The axes are all located in the x-axis of the world coordinate system. w y w In the plane, and z c Axis along x w Axis and y w The angle bisector of .

[0087] Next, step S300 is executed, that is, image processing is performed on each frame of image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system.

[0088] In an exemplary embodiment of the present application, image processing is performed on each frame of image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system, including: performing image processing on each frame of image, and calculating the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system using a grayscale center of gravity method, wherein each target image is composed of multiple pixel points.

[0089] Specifically, each image frame is preprocessed, including noise filtering and linear enhancement. The grayscale centroid method is then used to calculate the position of the center of gravity of each target image in the image pixel coordinate system, thereby obtaining the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system. It should be noted that the target 5 can be a variety of forms, such as white dots on a black background or black dots on a white background. The size of the target 5 should be such that its image occupies multiple pixels, rather than a single isolated pixel.

[0090] In addition, the target image should have a substantially symmetrical grayscale distribution and be convenient for determining and measuring the target 5 along the camera coordinate system x c 、y c Therefore, an appropriate target adapter 4 is used between the side surfaces of the upper and lower plates 31 and 33 of the vibration isolation platform and the target 5, so that the target plane is approximately perpendicular to the optical axis of the high-speed camera and the target image does not deform during the vibration test.

[0091] Next, step S400 is executed, that is, coordinate transformation is performed on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system.

[0092] In an exemplary embodiment of the present application, performing coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system further includes the following steps:

[0093] Obtaining the coordinate transformation relationship between the world coordinates of the target and its image pixel coordinates;

[0094] The world coordinates of each target in the world coordinate system are calculated based on the image pixel coordinates and the coordinate transformation relationship.

[0095] Specifically, first, determine the relationship between the world coordinates of the target and its image pixel coordinates. World coordinates (X W ,Y W ,Z W ) and the camera coordinates (X C ,Y C ,Z C ) is expressed in homogeneous coordinate and matrix form as follows:

[0096]

[0097] Among them, M E It is determined by the camera's orientation relative to the world coordinate system, that is, the camera's external parameters, and:

[0098]

[0099] Image physical coordinates (X, Y) and camera coordinates (X C ,Y C ,Z C ) is expressed in homogeneous coordinate and matrix form as follows:

[0100]

[0101] Where f is the focal length of the camera.

[0102] The transformation relationship between image pixel coordinates (U, V) and image physical coordinates (X, Y) is expressed in homogeneous coordinate and matrix form as follows:

[0103]

[0104] Among them, U0, V0 represent the coordinates of the image center (the intersection of the optical axis and the image plane), s x , s y are the sampling frequencies in the x and y directions, that is, the number of pixels per unit length.

[0105] Define f x , f y are the equivalent focal lengths in the x and y directions, respectively, and f x =s x f, f y =s y f. f x , f y, U0, V0 and other four parameters are only related to the internal structure of the camera, so these parameters are called camera internal parameters.

[0106] Define M I is the matrix determined by the internal parameters of the camera:

[0107]

[0108] Combining the relationships between the above four coordinate systems, we can obtain the relationship between the world coordinates of the target and its image pixel coordinates:

[0109]

[0110] Let M = M I M E , M is called the projection matrix.

[0111] By calibrating the internal and external parameters of the camera, f x ,f y ,U0,V0,r ij (i,j=0,1,2),t x ,t y ,t z , the projection matrix M can be determined.

[0112] Next, determine the Z of each target. c The measured target is along the camera coordinate system x c 、y c Axial characteristic dimension D x and D y (such as diameter, side length, etc.). Perform image processing and calculate the target image along x c 、y c The number of pixels occupied by the axis N x and N y . Calculation yields:

[0113]

[0114] To improve the calculation accuracy, the following methods can be used:

[0115] Because the relative distances between target points can be guaranteed by mechanical manufacturing or accurately measured, the relative distances between targets XA1 and XAk, YA1 and YAk, XB1 and XBk, and YB1 and YBk are known and are represented by the symbol ΔZ. C_XAk , ΔZ C_YAk , ΔZ C_XBk , ΔZ C_YBk represents the distance, where k = 2, 3, ... n. For the target on the X-side vibration isolation platform, n-1 equations can be obtained:

[0116] Z C_XAk -Z C_XA1 =ΔZ C_XAk (k=2,3,…n)

[0117] Solve the equations using the least squares method to obtain the Z of each target. C The same method is used for the targets on the upper plate of the X-side vibration isolation platform, the upper plate of the Y-side vibration isolation platform, and the lower plate of the Y-side vibration isolation platform.

[0118] Get Z C After the value of , the world coordinates (X W ,Y W ,Z W ).

[0119] Finally, step S500 is executed, that is, according to the world coordinates, the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system is calculated.

[0120] In an exemplary embodiment of the present application, calculating the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system according to the world coordinate system includes:

[0121] According to the world coordinates, calculate the angle between the line connecting any two targets and the world coordinate system;

[0122] The angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system is calculated based on the angle between the line connecting the two arbitrary targets and the world coordinate system.

[0123] Specifically, the angle between the line connecting the two targets and the world coordinate system is solved. For any two targets i and j, their world coordinates are expressed as (X Wi ,Y Wi ,Z Wi ) and (X Wj ,Y W2j ,Z W2j ). The line connecting the two points is at x w y w In-plane and x w The angle between the axes is

[0124]

[0125] The line connecting the two points is at y w z w In-plane and y w The angle between the axes is

[0126]

[0127] The line connecting the two points is at x w zw In-plane and x w The angle between the axes is

[0128]

[0129] Calculate the upper and lower plates of the vibration isolation platform relative to the world coordinate system x w 、y w 、z w Angular displacement of three axes:

[0130] The upper plate of the vibration isolation platform is relative to x w The angular displacement of the shaft is:

[0131]

[0132] Note: Symbol Indicates rounding up, the symbol Indicates rounding down.

[0133] The lower plate of the vibration isolation platform is relative to x w The angular displacement of the shaft is:

[0134]

[0135] The upper plate of the vibration isolation platform is relative to y w The angular displacement of the shaft is:

[0136]

[0137] The lower plate of the vibration isolation platform is relative to y w The angular displacement of the shaft is:

[0138]

[0139] The upper plate of the vibration isolation platform is relative to z w The angular displacement of the shaft is:

[0140]

[0141] The lower plate of the vibration isolation platform is relative to z w The angular displacement of the shaft is:

[0142]

[0143] See also Figure 3 As shown in the figure, the angular displacement input curve and output curve of the vibration isolation platform are obtained, with the shooting time of each frame image as the horizontal coordinate and θ as the horizontal coordinate. x,A ,θ y,A ,θ z,A As the vertical coordinates, the angular displacement output curve of the vibration isolation platform is obtained; the shooting time of each frame image is used as the horizontal coordinate, and θ x,B ,θy,B ,θ z,B As the vertical coordinates, the angular displacement input curve of the vibration isolation platform is obtained.

[0144] The angular displacement data is preprocessed and analyzed, and algorithms such as data smoothing and filtering are used to eliminate random noise in the data curve. Algorithms such as data segment fitting, Fourier analysis, and empirical mode analysis are used for data analysis to solve the frequency and amplitude characteristics of the angular displacement input and output of the vibration isolation platform, and further determine the angular displacement response characteristics of the vibration isolation platform.

[0145] In summary, the present invention provides a method for measuring the angular displacement of a vibration isolation platform, which obtains video data of a vibration test on the vibration isolation platform, wherein the vibration isolation platform is provided with a plurality of targets, extracts the video data frame by frame to obtain each frame image and its corresponding shooting time, wherein each frame image includes the target image of each target at the corresponding shooting time, performs image processing on each frame image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system, performs coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system, and calculates the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system based on the world coordinates. The method uses a high-speed camera for shooting, and can calculate the angular displacement data of multiple measuring points at the input and output ends of the vibration isolation platform at one time, including frequency and amplitude characteristics, thereby greatly improving the test efficiency. In addition, since only one high-speed camera is used to shoot all targets on the vibration isolation platform, the relative spatial position data of each target is strictly matched in the time domain, and no error is introduced during the data processing due to time domain alignment. In addition, by increasing the number of targets and the distance between them, the effects of some system noise and random noise can be suppressed, improving the accuracy of angular displacement measurements. At the same time, appropriate target adapters are used between the sides of the upper and lower plates of the vibration isolation platform and the targets, ensuring that the target plane is approximately perpendicular to the optical axis of the high-speed camera. This ensures that the target image has a substantially symmetrical grayscale distribution, facilitating the determination and measurement of the target's characteristic dimensions along the axis of the camera coordinate system, and that the target image does not deform during the test. Furthermore, the size of the target allows its image to occupy multiple pixels, rather than a single isolated pixel. Therefore, the grayscale centroid method can be used to calculate the position of the center of gravity of each target image in the image pixel coordinate system.

[0146] Based on the same inventive concept, please refer to Figure 4 As shown, another embodiment of the present invention further provides a vibration isolation platform angular displacement measuring device 11, the device comprising:

[0147] The data acquisition module 111 is used to acquire video data of a vibration test performed on a vibration isolation platform, wherein the vibration isolation platform is provided with a plurality of targets;

[0148] A data extraction module 112 is configured to extract the video data frame by frame to obtain each frame image and its corresponding shooting time, wherein each frame image includes a target image of each target at a corresponding shooting time;

[0149] The data processing module 113 is configured to perform image processing on each frame of the image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system;

[0150] The data calculation module 114 is used to perform coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system, and calculate the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system based on the world coordinates.

[0151] Based on the same inventive concept, another embodiment of the present invention further provides a vibration isolation platform angular displacement measurement system, the system comprising: a vibration test bench, an aerial camera or a simulated load thereof, a vibration isolation platform, a plurality of target adapters, a plurality of targets, a plurality of acceleration sensors, a high-speed camera, and a computer;

[0152] The vibration test bench is used to simulate the vibration environment effects of a real aircraft flight;

[0153] The vibration isolation platform includes an upper plate of the vibration isolation platform, a plurality of vibration isolators and a lower plate of the vibration isolation platform. The upper plate of the vibration isolation platform and the lower plate of the vibration isolation platform are fixedly connected via a plurality of vibration isolators. The aerial camera or its simulated load is installed on the upper plate of the vibration isolation platform. The lower plate of the vibration isolation platform is fixedly installed on the working table of the vibration test bench.

[0154] A plurality of target adapters are respectively installed on the first side and the second side of the vibration isolation platform, and a corresponding target is installed on each target adapter, wherein the first side and the second side are perpendicular to each other;

[0155] The plurality of acceleration sensors are installed on the working surface of the vibration test platform near the lower plate of the vibration isolation platform to measure the vibration acceleration during the vibration test;

[0156] The high-speed camera is installed on the symmetry axis of the first side and the second side of the vibration isolation platform, and is used to shoot a video of the vibration isolation platform performing a vibration test;

[0157] The computer is used to solve the angular displacement of the vibration isolation platform by using the vibration isolation platform angular displacement measurement method as described in any of the above embodiments.

[0158] It should be noted that, in this embodiment, the first side of the vibration isolation platform is the X side, and the second side of the vibration isolation platform is the Y side.

[0159] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for measuring angular displacement of a vibration isolation platform, characterized in that: include: Using a high-speed camera to capture video data of a vibration test performed on a vibration isolation platform, wherein the vibration isolation platform is provided with a plurality of targets; Extracting the video data frame by frame to obtain each frame image and its corresponding shooting time, wherein each frame image includes a target image of each target at the corresponding shooting time; Performing image processing on each frame of the image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system; Performing coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system; According to the world coordinates, the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system is calculated.

2. The vibration isolation platform angular displacement measurement method according to claim 1, characterized in that: The acquisition of video data of a vibration test performed on a vibration isolation platform includes: The vibration isolation platform undergoing the vibration test is continuously photographed using a high-speed camera to obtain video data of the vibration isolation platform undergoing the vibration test, wherein the photographing time of the high-speed camera includes the duration of the entire vibration test.

3. The vibration isolation platform angular displacement measurement method according to claim 1, characterized in that: The performing image processing on each frame of the image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system includes: Image processing is performed on each frame of the image, and the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system are calculated using a grayscale centroid method, wherein each target image is composed of a plurality of pixel points.

4. The method for measuring angular displacement of a vibration isolation platform according to claim 1, wherein: The performing coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system includes: Obtaining the coordinate transformation relationship between the world coordinates of the target and its image pixel coordinates; The world coordinates of each target in the world coordinate system are calculated based on the image pixel coordinates and the coordinate transformation relationship.

5. The vibration isolation platform angular displacement measurement method according to claim 1, characterized in that: The coordinate axis direction of the world coordinate system is consistent with the coordinate axis direction of the vibration isolation platform coordinate system; The vibration isolation platform coordinate system is established in the following way: The direction in which the aircraft simulated by the vibration test platform points vertically to the ground is the +Z direction, the flight direction of the aircraft simulated by the vibration test platform is the +X direction, and the +Y direction is determined according to the right-hand rule to establish the vibration isolation platform coordinate system.

6. The vibration isolation platform angular displacement measurement method according to claim 1, characterized in that: The step of calculating the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system according to the world coordinate system includes: According to the world coordinates, calculate the angle between the line connecting any two targets and the world coordinate system; The angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system is calculated based on the angle between the line connecting the two arbitrary targets and the world coordinate system.

7. A vibration isolation platform angular displacement measuring device, characterized in that: The device comprises: a data acquisition module, configured to use a high-speed camera to capture video data of a vibration test performed on a vibration isolation platform, wherein the vibration isolation platform is provided with a plurality of targets; a data extraction module, configured to extract the video data frame by frame to obtain each frame of image and its corresponding shooting time, wherein each frame of image includes a target image of each target at a corresponding shooting time; a data processing module, configured to perform image processing on each frame of the image to obtain the image pixel coordinates of the center of gravity of each target image in the image pixel coordinate system; The data calculation module is used to perform coordinate transformation on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system, and calculate the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system based on the world coordinates.

8. A vibration isolation platform angular displacement measurement system, characterized in that: include: Vibration test bench, aerial camera or its simulated load, vibration isolation platform, several target adapters, several targets, several acceleration sensors, high-speed camera and computer; The vibration test bench is used to simulate the vibration environment effects of a real aircraft flight; The vibration isolation platform includes an upper plate of the vibration isolation platform, a plurality of vibration isolators and a lower plate of the vibration isolation platform. The upper plate of the vibration isolation platform and the lower plate of the vibration isolation platform are fixedly connected via a plurality of vibration isolators. The aerial camera or its simulated load is installed on the upper plate of the vibration isolation platform. The lower plate of the vibration isolation platform is fixedly installed on the working table of the vibration test bench. A plurality of target adapters are respectively installed on the first side and the second side of the vibration isolation platform, and a corresponding target is installed on each target adapter, wherein the first side and the second side are perpendicular to each other; The plurality of acceleration sensors are installed on the working surface of the vibration test platform near the lower plate of the vibration isolation platform to measure the vibration acceleration during the vibration test; The high-speed camera is installed on the symmetry axis of the first side and the second side of the vibration isolation platform, and is used to shoot a video of the vibration isolation platform performing a vibration test; The computer is used to solve the angular displacement of the vibration isolation platform by using the vibration isolation platform angular displacement measurement method according to any one of claims 1 to 6.

9. The vibration isolation platform angular displacement measurement system according to claim 8, characterized in that: The target plane of the target is approximately perpendicular to the optical axis of the high-speed camera.

10. The vibration isolation platform angular displacement measurement system according to claim 8, characterized in that: The shooting frame rate of the high-speed camera is higher than 2 times the highest frequency of the input vibration of the vibration test platform.

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