Vibration isolation platform angular displacement measurement method, device and system

Abstract

The invention discloses a vibration isolation platform angular displacement measuring method, device and system, and the method comprises the steps: obtaining the video data of a vibration test of a vibration isolation platform, carrying out the frame-by-frame extraction of the video data, obtaining each frame of image and a corresponding shooting moment, carrying out the image processing of each frame of image, and obtaining the angular displacement of the vibration isolation platform. And performing coordinate transformation on the image pixel coordinates to obtain the image pixel coordinates of the gravity center 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, and performing calculation according to the world coordinates to obtain the angular displacement of the vibration isolation platform relative to the three axes of the world coordinate system. The method solves the technical problems that the vibration isolation platform angular displacement test cannot provide data support for the optimization design of angular displacement response and errors are easily introduced due to improper time domain registration in the data processing process.

Description

Technical Field

[0001] The invention belongs to the technical field of vibration testing, 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 are mounted on aircraft to capture and record optical radiation information from the ground or the atmosphere. Complex mechanical excitations are generated during the flight of an aircraft, including atmospheric drag and aerodynamic effects (atmospheric turbulence, flutter), excitation forces caused by aerodynamic and mechanical imbalances, excitation forces of the engine, and excitation forces caused by the rotor wake acting on other components. These mechanical excitations are transmitted to the aerial camera, causing the overall vibration of the camera and the relative vibration of each component, which will affect the imaging quality of the camera. Its main mechanism of action is: vibration causes the camera's visual axis to shake, introducing image shift during its exposure process, resulting in blurred imaging.

[0003] Vibration can be divided into linear vibration and angular vibration according to displacement characteristics. Previous studies have shown that angular vibration has a much greater impact on imaging quality than linear vibration. Therefore, during the development phase, vibration tests are carried out on the aerial camera vibration isolation platform, and angular displacement tests are carried out simultaneously, which is of great significance for performance verification of the vibration isolation platform and optimization of design solutions.

[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 reflector 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 of a certain point on the vibration isolation platform in two directions. 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 required to simultaneously monitor multiple directions of multiple measuring points. The time domain alignment of the data of 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, which uses a high-speed camera to shoot all targets on the vibration isolation platform, and by processing the video data obtained from the shooting, accurately calculates the angular displacement of the input and output ends of the vibration isolation platform relative to the world coordinate system in three-axis directions, thereby solving the technical problems in the prior art that the angular displacement test of the vibration isolation platform cannot provide data support for the optimal design of the angular displacement response and that errors are easily introduced due to improper time domain alignment during data processing.

[0006] In order 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 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 of image and its corresponding shooting time, wherein each frame of image includes a target image of each target at a 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 of the targets 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 center of gravity method, wherein each target image is composed of a plurality of pixel points.

[0017] In one embodiment of the present invention, the coordinate transformation of 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 and obtained according to 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 manner:

[0022] The direction in which the aircraft simulated by the vibration test platform points vertically to the ground is taken as the +Z direction, the flight direction of the aircraft simulated by the vibration test platform is taken as 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 three axes of the world coordinate system according to the world coordinate system includes:

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

[0025] According to the angle between the connecting line of 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.

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

[0027] A data acquisition module, 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;

[0028] A data extraction module, used 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;

[0029] A data processing module, used for 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;

[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 its simulated load, 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 effect of the actual flight of the aircraft;

[0033] The vibration isolation platform comprises 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 upper plate of the vibration isolation platform is installed with the aerial camera or its simulated load, 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 of the target adapters, 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, and are used 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 undergoing 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, which 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, so as to obtain each frame of image and its corresponding shooting time, wherein each frame of image includes the target image of each target at the corresponding shooting time, performs image processing on each frame of image, so as 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, so as 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 according to the world coordinates. The method uses a high-speed camera for shooting, and can solve 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, which greatly improves the test efficiency. In addition, since only one high-speed camera is used to shoot all the 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 in the data processing process 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, and the accuracy of angular displacement measurement can be improved. At the same time, an appropriate target adapter is used between the side of the upper plate of the vibration isolation platform and the lower plate 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, so that the target image of the target has a basically symmetrical grayscale distribution, which is convenient for determining and measuring the characteristic size 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 instead of 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 accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying 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 as an exemplary embodiment of the present application.

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

[0045] Figure 4 A schematic structural diagram of an angular displacement measuring device for a vibration isolation platform is provided as 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 isolator

[0052] 33 Vibration isolation platform lower plate

[0053] 4 Target adapter

[0054] 5 Target

[0055] 6 High-speed cameras

[0056] 7 Computer

[0057] 8 Accelerometer DETAILED DESCRIPTION

[0058] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways 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 without conflict.

[0059] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and thus the drawings only show components related to the present invention rather than being 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 complicated.

[0060] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0061] In order to solve the technical problems that the angular displacement test of the vibration isolation platform in the prior art cannot provide data support for the optimization design of the angular displacement response and that errors are easily introduced due to improper time domain registration during data processing, the present invention provides a vibration isolation platform angular displacement measurement method, which uses a high-speed camera to shoot all targets on the vibration isolation platform, and by processing the video data obtained from the shooting, accurately calculates the angular displacement of the input and output ends of the vibration isolation platform relative to the world coordinate system in the three-axis direction, and no errors are introduced in the data processing due to time domain registration. Please refer to Figure 1 As shown, the vibration isolation platform angular displacement measurement method includes the following steps:

[0062] S100: 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;

[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 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, a plurality of target adapters 4, a plurality of targets 5, a high-speed camera 6, a computer 7 and a plurality of acceleration sensors 8, and the vibration isolation platform 3 includes a vibration isolation platform upper plate 31, a vibration isolator 32 and a vibration isolation platform lower plate 33, and the vibration isolation platform upper plate 31 and the vibration isolation platform lower plate 33 are fixedly connected by a plurality of 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 aerial camera actually used.

[0070] The vibration isolation platform 3 is placed upright and installed centrally 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, that is, the direction of the aircraft simulated by the vibration test platform 1 pointing vertically to the ground is taken as the +Z direction, the flight direction of the aircraft simulated by the vibration test platform 1 is taken as the +X direction, and the +Y direction is determined according to the right-hand rule. According to the established vibration isolation platform coordinate system, the X side and the Y side of the vibration isolation platform 3 are determined.

[0072] The high-speed camera 6 is installed on the symmetric axis of the X side and the Y side of the vibration isolation platform 3. It should be noted that the installation position of the high-speed camera 6 needs to ensure that the X side and the Y side of the vibration isolation platform 3 can be clearly photographed at the same time. It is worth noting that the high-speed camera 6 needs to be installed stably and reliably, and any potential interference from the excitation source of the vibration test bench 1 must be effectively isolated.

[0073] At least two targets 5 are installed on the X side and Y side of the upper plate 31 of the vibration isolation platform and the X side and Y side of the lower plate 31 of the vibration isolation platform. In order to make the target plane perpendicular to the optical axis of the high-speed camera 6, a target adapter 4 is used to connect the side of the upper plate 31 of the vibration isolation platform and the lower plate 33 of the vibration isolation platform and the target 5. It should be noted that the total Y-direction span of the X-side targets of the upper plate 31 of the vibration isolation platform and the lower plate 33 of the vibration isolation platform should be increased as much as possible, and the X-side targets 5 of the upper plate 31 of the vibration isolation platform are numbered in sequence according to XA1, XA2...XAn according to the +Y direction of the vibration isolation platform coordinate system, and the X-side targets of the lower plate 33 of the vibration isolation platform are numbered in sequence according to XB1, XB2...XBn according to the +Y direction of the vibration isolation platform coordinate system. The total X-direction span of the Y-side targets of the upper plate 31 of the vibration isolation platform 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 acceleration sensors 8 are installed on the working 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 acceleration sensor 8 should be consistent with the vibration direction input by the vibration test bench 1.

[0075] It should be noted that by increasing the number of targets 5 and increasing the span between targets 5, the influence of some system noise and random noise can be suppressed, and the accuracy of subsequent angular displacement measurement of the vibration isolation platform can be improved. At the same time, since a high-speed camera 6 is used to shoot all targets 5, the relative spatial position data of each target 5 is strictly matched in the time domain, so no error is introduced in data processing due to time domain registration.

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

[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 test performed on a vibration isolation platform includes: continuously photographing the vibration isolation platform during the vibration test using a high-speed camera to obtain video data of the vibration test performed on the vibration isolation platform, 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 2 times the highest frequency of the input vibration of 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 the 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 frame of the extracted image as the origin and the pixel 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 numbers 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 optical axis and the image plane as the origin. Its x and y axes are parallel to the two 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 that can be arbitrarily defined by the user, so that the direction of its coordinate axis 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 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 the 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 frame of the image is preprocessed, the preprocessing includes filtering out noise, linear enhancement, etc., and then the grayscale centroid method is used to calculate the position of the centroid of each target image in the image pixel coordinate system, thereby obtaining the image pixel coordinates of the centroid of each target image in the image pixel coordinate system. It should be noted that the target 5 can be in various forms such as white dots on a black background or black dots on a white background, and the size of the target 5 should be such that its image can occupy multiple pixels rather than an isolated pixel.

[0090] In addition, the target image should have a substantially symmetrical grayscale distribution and facilitate determination and measurement of 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 plate 31 and the lower plate 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, coordinate transformation is performed on the image pixel coordinates to obtain the world coordinates of each target in the world coordinate system, further comprising 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 of the targets in the world coordinate system are calculated and obtained according to 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 coordinates 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, i.e. 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 coordinates 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 They 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] Definition M I is the matrix determined by the internal parameters of the camera:

[0107]

[0108] Combining the above four coordinate system relationships, we can get the relationship between the target's world coordinates 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 Characteristic dimension D in the axial direction 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 . The calculation can be obtained:

[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) of the corresponding target can be calculated according to a set of image pixel coordinates (U, V). 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 and obtaining 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 and obtain the angle between the line connecting any two targets and the world coordinate system;

[0122] According to the angle between the connecting line of 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.

[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 plate and lower plate 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 axis 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 axis is:

[0134]

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

[0136]

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

[0138]

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

[0140]

[0141] The lower plate of the vibration isolation platform is relative to z w The angular displacement of the axis 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 ordinate, the angular displacement output curve of the vibration isolation platform is obtained; the shooting time of each frame of image is used as the abscissa, and θ x,B ,θy,B ,θ z,B They are used as the ordinates to obtain the angular displacement input curve of the vibration isolation platform.

[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, so as to obtain each frame of image and its corresponding shooting time, wherein each frame of image includes the target image of each target at the corresponding shooting time, performs image processing on each frame of image, so as 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, so as 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 according to the world coordinates. The method uses a high-speed camera for shooting, and can solve 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, which greatly improves the test efficiency. In addition, since only one high-speed camera is used to shoot all the 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 in the data processing process 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, and the accuracy of angular displacement measurement can be improved. At the same time, an appropriate target adapter is used between the side of the upper plate of the vibration isolation platform and the lower plate 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, so that the target image of the target has a basically symmetrical grayscale distribution, which is convenient for determining and measuring the characteristic size 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 instead of 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.

[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 used 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 used 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 its simulated load, 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 effect of the actual flight of the aircraft;

[0153] The vibration isolation platform comprises 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 upper plate of the vibration isolation platform is installed with the aerial camera or its simulated load, and 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 of the target adapters, 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, and are used 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 undergoing 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 familiar with 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still 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: 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; Extracting 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; 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 of the targets 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 the vibration test performed on the 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 center of gravity method, wherein each target image is composed of a plurality of pixel points.

4. The vibration isolation platform angular displacement measurement method according to claim 1, characterized in that: The step of 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 and obtained according to 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 manner: The direction in which the aircraft simulated by the vibration test platform points vertically to the ground is taken as the +Z direction, the flight direction of the aircraft simulated by the vibration test platform is taken as 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 three axes of the world coordinate system according to the world coordinate system includes: According to the world coordinates, calculate and obtain the angle between the line connecting any two targets and the world coordinate system; According to the angle between the connecting line of 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.

7. A vibration isolation platform angular displacement measuring device, characterized in that: The device comprises: A data acquisition module, 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; A data extraction module, used 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; A data processing module, used for 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; 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 effect of the actual flight of the aircraft; The vibration isolation platform comprises 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 upper plate of the vibration isolation platform is installed with the aerial camera or its simulated load, and 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 of the target adapters, 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, and are used 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 undergoing 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 twice the highest frequency of the input vibration of the vibration test platform.

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