CN116091488B - Displacement testing method and displacement testing system for engine swing test - Google Patents
Displacement testing method and displacement testing system for engine swing test Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
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Abstract
The invention discloses a displacement testing method and a displacement testing system for an engine swing test, which relate to the technical field of structural tests, so as to simplify the testing process of the existing engine swing test, save labor cost and time cost and improve testing accuracy. The method comprises the following steps: dividing an untwisted image of an engine structure to be detected, and determining a corresponding target area; determining elliptical sub-pixel level edge coordinates of a preset mark point in a target area based on a swing image of an engine structure to be detected, which is acquired in real time; determining an ellipse center coordinate based on the ellipse sub-pixel level edge coordinate; determining the space coordinates corresponding to the preset mark points by combining the ellipse center coordinates based on the corresponding relation between the pre-stored space coordinate system and the ellipse center coordinates; and determining displacement parameters based on the space coordinates of each preset mark point, wherein the displacement parameters are the displacement of the engine structure to be tested in a swinging state relative to the displacement of the engine structure to be tested in a zero state.
Description
Technical Field
The invention relates to the technical field of structural tests, in particular to a displacement test method and a displacement test system for an engine swing test.
Background
The liquid rocket engine swing test is an important means for checking the compensation capability of a swing device and testing the swing moment. The spatial displacement of the oxidant from the fuel inlet pipe during engine sway is also an important design parameter.
Laser displacement sensors are currently commonly used to measure the displacement of the inlet tube. However, in the contact test method, a fixed reference position is required to be arranged around the engine, only single-point unidirectional displacement can be measured each time, if three-dimensional spatial displacement at a certain position of the engine is required to be tested, at least three laser displacement sensors are required to be arranged, the on-site arrangement is tedious, and more labor cost and time cost can be consumed. In addition, the surface of the engine is mostly a cambered surface, and the laser measuring point of the engine can deviate in the swinging process, so that test errors are introduced, and the accuracy of a swinging test is affected.
Disclosure of Invention
The invention aims to provide a displacement testing method and a displacement testing system for an engine swing test, which are used for simplifying the testing process of the existing engine swing test, saving labor cost and time cost and improving testing accuracy.
In order to achieve the above object, the present invention provides the following technical solutions:
in a first aspect, the present invention provides a displacement testing method for an engine swing test, the displacement testing method comprising:
dividing an untwisted image of an engine structure to be detected, and determining a corresponding target area by taking each preset mark point as a center, wherein a plurality of preset mark points are arranged on the engine structure to be detected;
determining elliptical sub-pixel level edge coordinates of a preset mark point in a target area based on a swing image of an engine structure to be detected, which is acquired in real time;
determining an ellipse center coordinate based on the ellipse sub-pixel level edge coordinate;
determining the space coordinates corresponding to the preset mark points by combining the ellipse center coordinates based on the corresponding relation between the pre-stored space coordinate system and the ellipse center coordinates;
and determining displacement parameters based on the space coordinates of each preset mark point, wherein the displacement parameters are the displacement of the engine structure to be tested in a swinging state relative to the displacement of the engine structure to be tested in a zero state.
Compared with the prior art, in the displacement test method for the engine swing test, after a plurality of preset mark points are stuck on the surface of the engine structure to be tested, the obtained non-swing image of the engine structure to be tested is subjected to segmentation processing, so that a corresponding target area is determined by taking each preset mark point as the center; in the swing image of the engine structure to be detected, which is acquired in real time, the preset mark point can be identified only in the target area, so that the identification efficiency of the swing image can be improved, and the oval sub-pixel level edge coordinates of the preset mark point can be determined. After the oval sub-pixel level edge coordinates of the preset mark points are determined, the oval center coordinates can be accurately extracted through sub-pixel edge detection, the displacement monitoring precision reaches 0.1mm, and the precision of the swing test is improved. And then, based on the corresponding relation between a pre-stored space coordinate system and the ellipse center coordinate, determining the space coordinate corresponding to each preset mark point, and after determining the space coordinate corresponding to each preset mark point, analyzing the space coordinate corresponding to the preset mark point in the swaying image and the space coordinate corresponding to the preset mark point in the non-swaying image, so as to determine the displacement parameter of the engine structure to be tested, thereby completing the swaying test of the engine structure to be tested. Based on the above, in the invention, the structural displacement of the engine mechanism to be tested in the swinging state can be observed through the displacement parameter of each preset mark point, and compared with the prior art that the number of the measuring points is increased by adding the laser displacement sensor, the number of the measuring points can be easily changed without obviously increasing the workload by only increasing or decreasing the number of the preset mark points, and the swinging test time can be shortened.
In addition, because the laser displacement sensor is not required to be used for carrying out the swing test on the engine structure to be tested in the application, namely, the fixed point of the laser displacement sensor is not required to be searched around the engine structure, and the laser displacement sensor is installed and wired, the swing test process is greatly simplified, the swing test efficiency is improved, and the labor cost and the time cost are saved to a certain extent.
In a second aspect, the present invention further provides a displacement testing system for an engine swing test, where the displacement testing system uses the displacement testing method for the engine swing test according to the first aspect, where the displacement testing system includes:
the device comprises an engine structure to be tested, a servo mechanism, a light supplementing device, two image acquisition devices and a control device, wherein:
the servo mechanism is arranged on the engine structure to be tested, and the control device is connected with the image acquisition device; the two image acquisition devices are arranged close to the engine structure to be detected at intervals, and a plurality of preset marking points on the engine structure to be detected are completely positioned in the visual field of the image acquisition devices; the light supplementing device is arranged close to the two image acquisition devices and is used for supplementing light to preset mark points on the engine structure to be tested;
The control device is used for dividing the non-swaying image of the engine structure to be detected, and determining a corresponding target area by taking each preset mark point as a center, wherein a plurality of preset mark points are arranged on the engine structure to be detected;
the control device is also used for determining elliptical sub-pixel level edge coordinates of a preset mark point in the target area based on the real-time acquired swing image of the engine structure to be detected;
the control device is also used for determining the center coordinates of the ellipse based on the edge coordinates of the ellipse sub-pixel level;
the control device is also used for determining the space coordinates corresponding to the preset mark points by combining the ellipse center coordinates based on the corresponding relation between the pre-stored space coordinate system and the ellipse center coordinates;
the control device is also used for determining displacement parameters based on the space coordinates of each preset mark point, wherein the displacement parameters are displacement when the engine structure to be tested is in a swinging state relative to the engine structure to be tested in a zero state.
Compared with the prior art, the beneficial effects of the displacement testing system for the engine swing test provided by the invention are the same as those of the displacement testing method for the engine swing test described in the technical scheme, and the description is omitted here.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:
FIG. 1 is a schematic diagram of a displacement testing system according to an embodiment of the present invention;
FIG. 2 is a flow chart of a displacement measurement method according to an embodiment of the present invention;
FIG. 3 is a flowchart of another displacement measurement method according to an embodiment of the present invention;
FIG. 4 is a flowchart of the operation of a displacement measurement system provided in an embodiment of the present invention;
fig. 5 is a schematic diagram illustrating the identification of preset mark points of a first camera according to an embodiment of the present invention;
fig. 6 is a schematic diagram illustrating the identification of preset mark points of a second camera according to an embodiment of the present invention;
fig. 7 is a real-time rocking curve of an engine structure to be tested according to an embodiment of the present invention.
Reference numerals:
101-an engine structure to be tested, 102-a servo mechanism;
103-a light supplementing device, 104-an image acquisition device;
1041-a first camera, 1042-a second camera;
105-preset mark points, 106-control device.
Detailed Description
In order to clearly describe the technical solution of the embodiments of the present invention, in the embodiments of the present invention, the words "first", "second", etc. are used to distinguish the same item or similar items having substantially the same function and effect. For example, the first threshold and the second threshold are merely for distinguishing between different thresholds, and are not limited in order. It will be appreciated by those of skill in the art that the words "first," "second," and the like do not limit the amount and order of execution, and that the words "first," "second," and the like do not necessarily differ.
In the present invention, the words "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.
In the present invention, "at least one" means one or more, and "a plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a alone, a and B together, and B alone, wherein a, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (one) of a, b or c may represent: a, b, c, a and b, a and c, b and c, or a, b and c, wherein a, b, c can be single or multiple.
The liquid rocket engine swing test is an important means for checking the compensation capability of a swing device and testing the swing moment. The spatial displacement of the oxidant from the fuel inlet pipe during engine sway is also an important design parameter.
Laser displacement sensors are currently commonly used to measure the displacement of the inlet tube. However, in practical application, when the contact measurement mode is adopted, a fixed reference position is required to be arranged around the engine for installing the laser displacement sensor, and one laser displacement sensor can only measure single-point unidirectional displacement.
In addition, the surface of the engine structure is mostly an arc surface, and in the process of engine swing, the laser measuring point can deviate, and a test error is introduced, so that the accuracy of a swing test is influenced.
In view of this, in order to solve the above technical problems, as shown in fig. 1, an embodiment of the present invention provides a displacement testing system for an engine swing test, the displacement testing system including: an engine structure 101 to be tested, a servo mechanism 102, a light supplementing device 103, two image acquisition devices 104 and a control device 106.
The servo mechanism 102 is arranged on the engine structure 101 to be tested, and the control device 106 is connected with the image acquisition device 104; the two image acquisition devices 104 are arranged close to the engine structure 101 to be detected at intervals, and a plurality of preset marking points 105 on the engine structure 101 to be detected are completely positioned in the field of view of the image acquisition devices 104; the light supplementing device 103 is arranged close to the two image acquisition devices 104 and is used for supplementing light to a preset mark point 105 on the engine structure 101 to be tested;
the control device 106 is configured to segment the non-swinging image of the engine structure 101 to be tested, and determine a corresponding target area with each preset mark point 105 as a center, where a plurality of preset mark points 105 are disposed on the engine structure 101 to be tested;
the control device 106 is further configured to determine an elliptical sub-pixel level edge coordinate of a preset mark point 105 in the target area based on the swing image of the engine structure 101 to be tested acquired in real time;
the control device 106 is further configured to determine an ellipse center coordinate based on the ellipse sub-pixel level edge coordinate;
the control device 106 is further configured to determine, based on a correspondence between a pre-stored spatial coordinate system and an ellipse center coordinate, a spatial coordinate corresponding to the preset mark point 105 in combination with the ellipse center coordinate;
The control device 106 is further configured to determine a displacement parameter based on the spatial coordinates of each preset mark point 105, where the displacement parameter is a displacement when the engine structure 101 to be tested is in a swinging state relative to the engine structure 101 to be tested in a null state.
In this application, the light compensating device 103 may be a light compensating lamp, the control device 106 may be a computer with image processing software installed, the two image capturing devices 104 may be two high-definition cameras, for example, the model of the cameras may be AVT 1800U-1620, and the resolution is 5328×3040. The camera lens adopts a V5028-MPY 50mm fixed focus lens, and the high-definition camera can be connected with a computer through a USB3.0 interface, and the embodiment of the invention is not particularly limited to the above.
In practice, the servo 102 may be mounted on the engine structure 101 to be tested for precisely controlling the wobble of the engine structure 101 to be tested. By sticking a plurality of preset mark points 105 on the surface of the engine structure 101 to be tested, two high-definition cameras are arranged around the engine structure 101 to be tested, and meanwhile, the exposure time of the cameras is adjusted, so that each preset mark point 105 clearly appears in a structural image, and the positions and directions of the two high-definition cameras are adjusted, so that the camera view can cover the areas where the plurality of preset mark points 105 on the engine structure 101 to be tested are located. Thereafter, the focal length of the camera may be adjusted so that the engine structure 101 under test can be clearly imaged on the camera. Further, the computer is in communication connection with the high-definition camera through a USB3.0 interface so as to process the non-swinging image and swinging image shot by the high-definition camera. In this application, the light-compensating lamp may be disposed at a position as shown in fig. 1, that is, between two cameras, to compensate for a plurality of preset mark points 105 on the engine structure 101 to be tested. However, it should be understood that the light-compensating lamp may be disposed at other locations convenient for light compensation, which is not particularly limited in the embodiments of the present invention. When the light supplementing lamp is turned on to supplement light to the preset marking points 105, the exposure time of the camera needs to be synchronously adjusted so as to enhance the contrast of each preset marking point 105 and make the contrast clearer. In practice, the preset mark point 105 may be a circular mark point with a reflective area having a diameter of 20mm, which is not specifically limited in this embodiment of the present invention.
With the above technical solution, after a plurality of preset mark points 105 are stuck on the surface of the engine structure 101 to be tested, the control device 106 may determine a corresponding target area by performing segmentation processing on the obtained non-swaying image of the engine structure 101 to be tested, with each preset mark point 105 as a center; the control device 106 can also identify the preset mark point 105 only in the target area in the swing image of the engine structure 101 to be detected obtained in real time, so that the identification efficiency of the swing image can be improved, and the oval subpixel level edge coordinates of the preset mark point 105 can be determined. After the oval sub-pixel level edge coordinates of the preset mark point 105 are determined, the oval center coordinates can be accurately extracted through sub-pixel edge detection, the displacement monitoring precision reaches 0.1mm, and the precision of the swing test is improved. Then, based on the corresponding relation between the pre-stored space coordinate system and the ellipse center coordinate, the control device 106 can determine the space coordinate corresponding to each preset mark point 105, after determining the space coordinate corresponding to each preset mark point 105, analyze the space coordinate corresponding to the preset mark point 105 in the swinging image and the space coordinate corresponding to the preset mark point 105 in the non-swinging image, and then determine the displacement parameter of the engine structure 101 to be tested, so as to complete the swinging test of the engine structure 101 to be tested. Based on this, in the embodiment of the present invention, through the displacement parameter of each preset mark point 105, the structural displacement of the engine mechanism to be tested in the swinging state can be observed, compared with the prior art that the number of the measuring points is increased by adding the laser displacement sensor, the number of the measuring points can be easily changed without significantly increasing the workload by only increasing or decreasing the number of the preset mark points 105, and the time of the swinging test can be shortened.
In addition, because the laser displacement sensor is not required to be used for carrying out the swing test on the engine structure 101 to be tested in the application, namely, the fixed point of the laser displacement sensor is not required to be searched around the engine structure, and the laser displacement sensor is installed and wired, the swing test process is greatly simplified, the swing test efficiency is improved, and the labor cost and the time cost are saved to a certain extent. And compared with the traditional laser displacement sensor, the hardware cost of the high-definition camera is lower than that of other displacement testing instruments.
Referring to fig. 2, the present application further provides a displacement testing method for an engine static test, where the displacement testing method includes:
step 101: the method comprises the steps of dividing an untwisted image of the engine structure 101 to be detected, and determining a corresponding target area by taking each preset mark point 105 as a center, wherein a plurality of preset mark points 105 are arranged on the engine structure 101 to be detected.
It should be noted that in the present application, the non-rocking image of the engine structure 101 to be measured includes a set of images taken by the two image acquisition devices 104. When the engine structure 101 to be tested is in the non-swaying state, that is, the engine to be tested is in the zero state, the two image acquisition devices 104 shoot the engine structure 101 to be tested to acquire a group of non-swaying images of the engine structure 101 to be tested in the zero state.
Step 102: based on the swing image of the engine structure 101 to be measured acquired in real time, elliptical sub-pixel level edge coordinates of the preset marker point 105 in the target area are determined.
It can be appreciated that after the swing image of the engine structure 101 to be tested is obtained in real time, the elliptical sub-pixel level edge coordinates of the preset mark points 105 can be quickly determined in the target area determined in the previous step, so that the recognition efficiency of the plurality of preset mark points 105 is further improved, the algorithm time for determining the elliptical sub-pixel level edge coordinates is reduced, the algorithm efficiency is improved, and the time cost of the swing test is reduced.
Step 103: an ellipse center coordinate is determined based on the ellipse sub-pixel level edge coordinates.
Specifically, after the oval sub-pixel level edge coordinates are determined, the oval center coordinates can be accurately extracted through sub-pixel edge detection, so that the displacement monitoring precision of the swing test reaches 0.1mm, and the precision of the swing test is improved.
Step 104: based on the corresponding relation between the pre-stored space coordinate system and the ellipse center coordinate, the space coordinate corresponding to the preset mark point 105 is determined by combining the ellipse center coordinate.
In practice, by calibrating the two image acquisition devices 104, the corresponding relationship between the space coordinate system and the ellipse center coordinate may be determined, and the corresponding relationship between the space coordinate system and the ellipse center coordinate is pre-stored in the control device 106 in the above embodiment, and then the space coordinate corresponding to each preset mark point 105 is calculated by combining the ellipse center coordinate determined in the previous step.
Step 105: based on the spatial coordinates of each preset mark point 105, a displacement parameter is determined, wherein the displacement parameter is the displacement when the engine structure 101 to be tested is in a swinging state relative to the engine structure 101 to be tested in a zero state.
In the application, by determining the space coordinates of each preset mark point 105, the space displacement of each preset mark point 105 can be determined, so that the displacement parameter of the engine structure 101 to be tested in a swinging state relative to the displacement parameter in a zero state is determined, and the real-time monitoring of the swinging test of the engine structure 101 to be tested is realized.
As can be seen from the displacement testing method of the engine swing test provided in the above embodiment, after a plurality of preset mark points 105 are stuck on the surface of the engine structure 101 to be tested, the obtained non-swing image of the engine structure 101 to be tested is subjected to segmentation processing, so that a corresponding target area is determined with each preset mark point 105 as the center; in the swing image of the engine structure 101 to be detected, which is acquired in real time, the preset mark point 105 can be identified only in the target area, so that the identification efficiency of the swing image can be improved, and the elliptical sub-pixel level edge coordinates of the preset mark point 105 can be determined. After determining the oval sub-pixel level edge coordinates of the preset mark point 105, the oval center coordinates can be extracted accurately through sub-pixel edge detection, the displacement monitoring accuracy reaches 0.1mm, and the accuracy of the swing test can be improved. And then, based on the corresponding relation between the pre-stored space coordinate system and the ellipse center coordinate, determining the space coordinate corresponding to each preset mark point 105, and after determining the space coordinate corresponding to each preset mark point 105, analyzing the space coordinate corresponding to the preset mark point 105 in the swaying image and the space coordinate corresponding to the preset mark point 105 in the non-swaying image, thereby determining the displacement parameter of the engine structure 101 to be tested so as to complete the swaying test of the engine structure 101 to be tested. Based on this, in the embodiment of the present invention, through the displacement parameter of each preset mark point 105, the structural displacement of the engine mechanism to be tested in the swinging state can be observed, compared with the prior art that the number of the measuring points is increased by adding the laser displacement sensor, the number of the measuring points can be easily changed without significantly increasing the workload by only increasing or decreasing the number of the preset mark points 105, and the time of the swinging test can be shortened.
In addition, because the laser displacement sensor is not required to be used for carrying out the swing test on the engine structure 101 to be tested in the application, namely, the fixed point of the laser displacement sensor is not required to be searched around the engine structure, and the laser displacement sensor is installed and wired, the swing test process is greatly simplified, the swing test efficiency is improved, and the labor cost and the time cost are saved to a certain extent.
The embodiment of the application also provides another displacement testing method for the engine swing test, as shown in fig. 3, the displacement testing method comprises the following steps:
step 201: the parameter matrices corresponding to the two image acquisition apparatuses 104, and the rotation matrix and the translation matrix between the two image acquisition apparatuses 104 are determined, respectively.
Step 202: based on the parameter matrix, the rotation matrix and the translation matrix, a corresponding relation between the space coordinate system and the ellipse center coordinate is established.
In practical applications, the two image acquisition devices 104 may be calibrated using a checkerboard pattern calibration plate to achieve a transformation of the ellipse center coordinates into a spatial coordinate system. For example, two image acquisition devices 104 are calibrated using a 300mm x 300mm checkerboard calibration plate. And shooting images of a plurality of groups of checkerboard calibration plates at different angles and different spatial positions, for example, shooting 8 groups of images to 20 groups of images, processing the image groups by using a Matlab binocular camera calibration tool box to obtain an internal reference matrix of the camera, and obtaining an external reference matrix, a rotation matrix and a translation matrix between the two cameras according to the matching relation between the image groups shot by the two cameras.
Then, a conversion relationship between the space coordinate system and the ellipse center coordinate may be determined based on the internal reference matrix, the external reference matrix, the rotation matrix, and the translation matrix.
Step 203: the method comprises the steps of dividing an untwisted image of the engine structure 101 to be detected, and determining a corresponding target area by taking each preset mark point 105 as a center, wherein a plurality of preset mark points 105 are arranged on the engine structure 101 to be detected.
Specifically, an untwisted image of the engine structure 101 to be tested may be obtained, an oxford threshold segmentation process is performed on the untwisted image to obtain a first binarized image, a plurality of connected regions of the first binarized image are determined, a connected region matched with the roundness characteristic parameters of the plurality of connected regions and the first roundness characteristic parameters is determined as a first target region, the center of gravity of each first target region is taken as the center, the equivalent diameter of a preset multiple is taken as the side length, and a plurality of target regions with square shapes are divided.
In the present application, the specific numerical value of the first roundness feature parameter is not limited, and may be specifically set according to an actual application scenario.
In a specific implementation, the two image acquisition devices 104 capture an untwisted image of the engine structure 101 to be tested in a zero state, and then send the untwisted image to the control device 106 communicatively connected with the image acquisition devices 104, and the control device 106 performs an oxford threshold segmentation process on the untwisted image to obtain a processed first binarized image. Calculating each connected region, extracting the outline of each connected region, and determining the connected region with the roundness being greater than or equal to 0.85 as a first target region according to the roundness characteristic parameter, wherein the first roundness characteristic parameter is that the roundness characteristic is greater than or equal to 0.85. Taking the center of gravity of each first target area as the center of gravity, dividing a plurality of target areas with square shapes according to the preset multiple of the equivalent diameter of the communication area as the side length (for example, 1.5 times of the equivalent diameter is the side length), wherein the calculation mode of the equivalent diameter is as follows:
Where d represents the equivalent diameter and S represents the area of the communication region.
It should be noted that since the image capturing devices 104 are two, the first camera 1041 and the second camera 1042 are included. The non-rocking image of the zero state thus acquired should be a set of images taken by the first camera 1041 and the second camera 1042. After the target area is determined, the first image captured by the first camera 1041 and the second image captured by the second camera 1042 are respectively numbered according to the pixel distance of the center of gravity of the communication area from the upper left corner of the image, the preset mark points 105 corresponding to the first image and the second image are matched, and the matching relation of the preset mark points 105 between the first image captured by the first camera 1041 and the second image captured by the second camera 1042 is determined, so that the external parameter matrix calibrated by the first camera 1041 and the second camera 1042 can be corrected, thereby avoiding the measurement error caused by the deviation of the installation position of the cameras.
Step 204: acquiring a swing image of the engine structure 101 to be tested; and performing the Ojin threshold segmentation processing on the swing image in the target area to obtain a second binarized image.
Specifically, the two image acquisition devices 104 capture a swing image of the engine structure 101 to be tested in a swing state, and then send the swing image to the control device 106 communicatively connected to the image acquisition devices 104, where the control device 106 performs an oxford threshold segmentation process on the swing image, so as to obtain a processed second binarized image.
Step 205: a plurality of connected regions of the second binarized image are determined.
Specifically, each communication region may be calculated, and the contour of each communication region may be extracted.
Step 206: and sequencing the connected regions matched with the roundness characteristic parameters and the second roundness characteristic parameters of the plurality of connected regions according to the area, and determining the connected region with the largest area as a mark point binarization image corresponding to the preset mark point 105.
The specific numerical value of the second roundness characteristic parameter is not limited, and may be specifically set according to an actual application scenario.
Confirming a connected region with the roundness of more than or equal to 0.75 as a sub-target region according to the roundness characteristic parameter, wherein the second roundness characteristic parameter is that the roundness characteristic is more than or equal to 0.75, then sorting the sub-target region according to the area, and determining that the connected region with the largest area in the sub-target region is a mark point binarized image corresponding to a preset mark point 105.
It should be understood that the above operation should be performed in target areas, in which there is a possibility that more than one connected area is connected, and only the sub-target area having the largest area in the current target area may be the mark point binarized image corresponding to the preset mark point 105, with the roundness being greater than or equal to 0.75.
Step 207: based on the marker binarized image, elliptical sub-pixel level edge coordinates of the preset marker 105 are determined.
In this application, the implementation procedure of the step 207 may include the following substeps:
substep A1: and carrying out morphological expansion treatment on the mark point binarized image to obtain a morphological expansion result.
Substep A2: based on the sobel edge detection result and the morphological dilation result in the target area, elliptical pixel-level edge coordinates of the preset marker points 105 in each target area are determined.
Substep A3: the elliptical sub-pixel level edge coordinates of the preset mark point 105 are determined based on the elliptical pixel level edge coordinates.
In specific implementation, the binarized image of the marker point determined in step 206 is subjected to morphological expansion processing to obtain a morphological expansion result, and then the morphological expansion result can be intersected with the sobel edge detection result in the target area,obtaining elliptic pixel level edge coordinates of preset mark points 105 in each target area
Then using sub-pixel edge detection in combination with elliptic pixel level edge coordinates>
Determining oval subpixel level edge coordinates +.>
. And the image processing is only carried out in the target area by real-time analysis, and the detection efficiency can be greatly improved by adopting the Sobel edge detection algorithm.
In particular, a specific implementation of the sub-step A3 may include the following sub-steps:
substep B1: and determining the gradient direction of the pixel point corresponding to the elliptic pixel level edge coordinate by using the Sobel operator.
In the application, the gradient value of the swing image in the width direction and the gradient value in the height direction can be determined by using the sobel operator, and further, the gradient direction of the pixel point is determined based on the gradient value in the width direction and the gradient value in the height direction.
Specifically, the gradient value dx of the swing image in the width direction and the gradient value dy in the height direction may be calculated by using the sobel operator, and the gradient direction θ may be calculated based on the gradient value dx in the width direction and the gradient value dy in the height direction:
。
substep B2: and respectively expanding a preset number of pixel points along two sides of the gradient direction by taking the pixel point as a center to obtain a target pixel point set.
The number of the preset pixels may be 2, or may be 3, which is not specifically limited in the embodiment of the present application.
For example, with the current pixel point
As the center, along the gradientAnd respectively expanding 2 pixel points on two sides of the direction to obtain a target pixel point set of 5 pixel points including the current pixel point.
Substep B3: and determining the gradient value of the target pixel point set by utilizing the bilinear difference value.
For example, after the target set of pixels is obtained, gradient values for the 5 pixels may be calculated using a bilinear difference algorithm.
Substep B4: the elliptical subpixel level edge coordinates of the preset mark point 105 are determined based on the gradient values of the target set of pixel points.
Specifically, based on the gradient value of the target pixel point set, the coordinate of each point in the target pixel point set is taken as an independent variable, the gradient value of the target pixel point set is taken as a function value, quadratic curve interpolation calculation is performed, and the vertex abscissa of the parabola corresponding to the target pixel point set is determined; the elliptical subpixel level edge coordinates of the preset mark point 105 are determined based on the vertex abscissa.
For example, 5 pixels in the target pixel set are used, coordinates-2, -1, 0, 1 and 2 are used as independent variables, gradient values of the target pixel set are used as function values, quadratic curve interpolation calculation is performed, and the vertex abscissa of the parabola corresponding to the target pixel set is determined
The method comprises the steps of carrying out a first treatment on the surface of the According to the vertex abscissa->
Computing oval sub-pixel edge points +.>
The calculation formula is as follows:
from the above, it can be seen that the abscissa of the vertex of the parabola in the gradient direction θ is determined 
After that, it canAnd determining the edge coordinates of the elliptical sub-pixels according to the edge coordinates of the elliptical pixel level.
Step 208: an ellipse center coordinate is determined based on the ellipse sub-pixel level edge coordinates.
For example, a plurality of fitting coefficients in a plane ellipse equation can be determined by a least square fitting method based on the ellipse sub-pixel level edge coordinates, and the center coordinates of the plane ellipse equation are determined based on the correspondence between the plurality of fitting coefficients and the ellipse center coordinates.
Specifically, in each target area, using the edge coordinates of the elliptic sub-pixel level determined in the previous step, and adopting a least square fitting method to calculate a plane elliptic equation
To determine the center coordinates of the ellipse by fitting coefficients A, B, C, D and E>
The correspondence between the center coordinates of the ellipse and the fitting coefficients A, B, C, D and E is as follows:
it can be understood that, in practical application, when acquiring the swing image of the engine structure 101 to be measured, in order to ensure the accuracy of measurement, the two image acquisition devices 104 may be in a continuous shooting mode, after determining the center coordinates corresponding to the preset mark point 105 in the previous frame, the current frame may update the target area with the center coordinates determined by the previous frame, so as to further reduce the range of the target area, thereby improving the recognition rate of the preset mark point 105 and further enhancing the real-time performance of the application.
Step 209: based on the corresponding relation between the pre-stored space coordinate system and the ellipse center coordinate, the space coordinate corresponding to the preset mark point 105 is determined by combining the ellipse center coordinate.
In practice, by calibrating the two image acquisition devices 104, the corresponding relationship between the space coordinate system and the ellipse center coordinate is determined, and the corresponding relationship between the space coordinate system and the ellipse center coordinate is pre-stored in the control device 106 in the above embodiment, and then the space coordinate corresponding to each preset mark point 105 is calculated by combining the ellipse center coordinate determined in the previous step.
Step 210: based on the spatial coordinates of each preset mark point 105, a displacement parameter is determined, wherein the displacement parameter is the displacement when the engine structure 101 to be tested is in a swinging state relative to the engine structure 101 to be tested in a zero state.
In the application, by determining the space coordinates of each preset mark point 105, the space displacement of each preset mark point 105 can be determined, so that the displacement parameter of the engine structure 101 to be tested in a swinging state relative to the displacement parameter in a zero state is determined, and the real-time monitoring of the swinging test of the engine structure 101 to be tested is realized.
The following will describe in detail the specific implementation process of the displacement test system for the engine static test provided by the invention with reference to fig. 1, 4 to 6.
And (5) constructing a displacement testing system in the first step. First, the servo 102 is mounted on the engine structure 101 to be tested. Then, the first camera 1041 and the second camera 1042 and the light compensating lamp are arranged around the engine structure 101 to be tested, and the positions and directions of the two cameras are adjusted so that the fields of view of the two cameras cover the main observation area of the engine structure 101 to be tested. The focal length is adjusted so that the engine structure 101 to be tested is imaged clearly in the camera. A plurality of high-reflection circular marking points are stuck on the surface main observation area of the engine structure 101 to be detected to serve as preset marking points 105 (for example, 5 high-reflection circular marking points are stuck), a light supplementing lamp is turned on to supplement light to the preset marking points 105, and the exposure time of a camera is adjusted, so that each preset marking point 105 is clearer.
And secondly, calibrating the binocular camera to realize transformation from the elliptical center coordinates to a space coordinate system. And shooting a plurality of groups of images of different angles and different spatial positions of the checkerboard pattern calibration plates by adopting the checkerboard pattern calibration plates, and guiding the shot images into a Matlab binocular camera calibration tool box to obtain a camera internal reference matrix, a rotation matrix and a translation matrix.
The third step acquires the non-rocking image as a reference image. The control device 106 is used for controlling the two cameras to shoot a group of images of the engine structure 101 to be tested, and the acquired non-swaying images are transmitted to the control device 106. The control device 106 performs an oxford threshold segmentation process on the images captured by the first camera 1041 and the second camera 1042, binarizes the target image to obtain a first binarized image, calculates a connected region in the image, uses the connected region with the roundness being greater than or equal to 0.85 as a first target region, divides the square target region by taking the center of gravity as the center and according to the equivalent diameter of 1.5 times, then numbers the pixel distance of the center of gravity of each target region from the upper left corner of the image, and matches the image captured by the first camera 1041 with a corresponding preset mark point 105 in the image captured by the second camera 1042. For example, 1 and 2 … L connected regions in the image captured by the first camera 1041, and 1 and 2 … R connected regions in the image captured by the second camera 1042, and the corresponding preset mark points 105 in the first camera 1041 and the second camera 1042 are matched to obtain N mark point pairs, where N is less than or equal to L and N is less than or equal to R. And updating the parameter of the external parameter matrix calibrated by the camera according to the matching relation.
The fourth step is to collect swing images, control the two cameras by using the control device 106 to shoot a group of images of the engine structure 101 to be tested, and transmit the collected swing images to the control device 106. The control device 106 performs the oxford threshold segmentation processing on the images captured by the first camera 1041 and the second camera 1042, binarizes the target image to obtain a second binarized image, calculates the connected areas in the image, orders the connected areas with the roundness being greater than or equal to 0.75 according to the areas in the target area, determines that the connected area with the largest area is the mark point binarized image corresponding to the preset mark point 105, performs the morphological expansion processing on the mark point binarized image to obtain a morphological expansion result, crosses the morphological expansion result with the sobel edge detection result, determines the oval pixel level edge coordinates of the preset mark point 105 in each target area, and then determines the oval sub-pixel level edge coordinates by utilizing sub-pixel edge detection and combining the oval pixel level edge coordinates.
And fifthly, fitting an ellipse by using a least square method, and determining the center coordinates of the ellipse corresponding to each preset mark point 105. And in each target area, utilizing the edge coordinates of the elliptic sub-pixel level determined in the last step, and adopting a least square fitting method to calculate the fitting coefficient of a plane elliptic equation so as to determine the center coordinates of the ellipse.
And sixthly, binocular stereo matching is carried out. Center coordinates of ellipses in the swing images photographed by the first camera 1041 and the second camera 1042 are matched. As shown in fig. 5 and 6, fig. 5 is a diagram showing 6 ellipse center points fitted in the swing image captured by the first camera 1041, and fig. 6 is a diagram showing 6 ellipse center points fitted in the swing image captured by the second camera 1042.
The seventh step is to preset the displacement calculation of the mark point 105 in real time. And determining the neutral real-time space coordinates of each preset mark point 105 according to the pre-stored internal reference matrix, external reference matrix, rotation matrix and translation matrix of the camera.
Fig. 7 illustrates a real-time rocking curve of the engine structure 101 to be tested, the horizontal axis representing time in seconds, and the vertical axis representing displacement distance of the engine structure 101 to be tested in millimeters. The three curves represent rocking curves of the engine structure 101 under test in the X-direction, Y-direction, and Z-direction, respectively, in the spatial coordinate system.
Although the invention is described herein in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
Although the invention has been described in connection with specific features and embodiments thereof, it will be apparent that various modifications and combinations can be made without departing from the spirit and scope of the invention. Accordingly, the specification and drawings are merely exemplary illustrations of the present invention as defined in the appended claims and are considered to cover any and all modifications, variations, combinations, or equivalents that fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (5)
1. A displacement test method for an engine sway test, the displacement test method comprising:
dividing an untwisted image of an engine structure to be detected, and determining a corresponding target area by taking each preset mark point as a center, wherein a plurality of preset mark points are arranged on the engine structure to be detected;
determining elliptical sub-pixel level edge coordinates of the preset mark points in the target area based on the swing image of the engine structure to be detected, which is acquired in real time;
Determining ellipse center coordinates based on the ellipse sub-pixel level edge coordinates;
determining the space coordinates corresponding to the preset mark points by combining the ellipse center coordinates based on the corresponding relation between a pre-stored space coordinate system and the ellipse center coordinates;
determining displacement parameters based on the space coordinates of each preset mark point, wherein the displacement parameters are displacements when the engine structure to be tested is in a swinging state and is in a zero state relative to the engine structure to be tested;
the determining, based on the swing image of the engine structure to be tested obtained in real time, the elliptical sub-pixel level edge coordinates of the preset mark point in the target area includes,
acquiring the swing image of the engine structure to be tested;
performing Ojin threshold segmentation processing on the swing image in the target area to obtain a second binarized image;
determining a plurality of connected regions of the second binarized image;
sorting the connected areas matched with the roundness characteristic parameters and the second roundness characteristic parameters of the plurality of connected areas according to the area, and determining the connected area with the largest area as a mark point binarization image corresponding to the preset mark point;
Determining elliptical sub-pixel level edge coordinates of the preset mark points based on the mark point binarized image;
determining elliptical subpixel level edge coordinates of the preset mark point based on the mark point binarized image, including:
performing morphological expansion treatment on the mark point binarized image to obtain a morphological expansion result;
determining elliptical pixel level edge coordinates of the preset mark points in each target area based on the Sobel edge detection result and the morphological expansion result in the target area;
determining the elliptic sub-pixel level edge coordinates of the preset mark point based on the elliptic pixel level edge coordinates;
the determining the elliptic sub-pixel level edge coordinates of the preset mark point based on the elliptic pixel level edge coordinates includes:
determining the gradient direction of the pixel point corresponding to the elliptic pixel level edge coordinate by utilizing a Sobel operator;
respectively expanding a preset number of pixel points along two sides of the gradient direction by taking the pixel point as a center to obtain a target pixel point set;
determining gradient values of the target pixel point set by utilizing bilinear difference values;
determining elliptical sub-pixel level edge coordinates of the preset mark points based on gradient values of the target pixel point set;
The determining the gradient direction of the pixel point corresponding to the elliptic pixel level edge coordinate by using the sobel operator comprises the following steps:
determining gradient values of the swing image in the width direction and gradient values of the swing image in the height direction by utilizing the Sobel operator;
determining a gradient direction of the pixel point based on the gradient value in the width direction and the gradient value in the height direction;
the determining the elliptical sub-pixel level edge coordinates of the preset mark point based on the gradient value of the target pixel point set comprises the following steps:
based on the gradient value of the target pixel point set, taking the coordinate of each point in the target pixel point set as an independent variable, taking the gradient value of the target pixel point set as a function value, performing quadratic curve interpolation calculation, and determining the vertex abscissa of a parabola corresponding to the target pixel point set;
and determining the elliptical sub-pixel level edge coordinates of the preset mark point based on the vertex abscissa.
2. The displacement testing method of the engine swing test according to claim 1, wherein the dividing the non-swing image of the engine structure to be tested, and determining the corresponding target area with each preset mark point as a center, includes:
Acquiring the non-swinging image of the engine structure to be tested;
performing Ojin threshold segmentation processing on the non-swaying image to obtain a first binarized image;
determining a plurality of connected regions of the first binarized image;
determining a communication region matched with the first roundness characteristic parameters in the roundness characteristic parameters of the plurality of communication regions as a first target region;
and dividing a plurality of target areas with a square shape by taking the center of gravity of each first target area as the center and taking the equivalent diameter of a preset multiple as the side length.
3. The displacement testing method of engine rocking test according to claim 1, wherein,
the determining the ellipse center coordinate based on the ellipse sub-pixel level edge coordinate includes:
based on the elliptic subpixel level edge coordinates, a least square fitting method is adopted to determine a plurality of fitting coefficients in a plane elliptic equation;
and determining the center coordinates of the plane elliptic equation based on the corresponding relation between the fitting coefficients and the center coordinates of the ellipse.
4. The displacement testing method of an engine rocking test according to claim 1, wherein before the spatial coordinates corresponding to the preset mark point are determined in conjunction with the elliptical center coordinates based on the correspondence between the pre-stored spatial coordinate system and the elliptical center coordinates, the method further comprises:
Respectively determining a parameter matrix corresponding to the two image acquisition devices, and a rotation matrix and a translation matrix between the two image acquisition devices;
and establishing a corresponding relation between the space coordinate system and the ellipse center coordinate based on the parameter matrix, the rotation matrix and the translation matrix.
5. A displacement testing system for an engine sway test, using the displacement testing method for the engine sway test according to any one of claims 1 to 4, characterized in that the displacement testing system comprises: the device comprises an engine structure to be tested, a servo mechanism, a light supplementing device, two image acquisition devices and a control device, wherein:
the servo mechanism is arranged on the engine structure to be tested, and the control device is connected with the image acquisition device; the two image acquisition devices are arranged close to the engine structure to be detected at intervals, and a plurality of preset mark points on the engine structure to be detected are completely positioned in the visual field of the image acquisition devices; the light supplementing device is arranged close to the two image acquisition devices and is used for supplementing light to the preset mark points on the engine structure to be tested;
The control device is used for dividing the non-swaying image of the engine structure to be detected, and determining a corresponding target area by taking each preset mark point as a center, wherein a plurality of preset mark points are arranged on the engine structure to be detected;
the control device is further used for determining elliptical sub-pixel level edge coordinates of the preset mark point in the target area based on the swing image of the engine structure to be detected, which is acquired in real time;
the control device is also used for determining an ellipse center coordinate based on the ellipse sub-pixel level edge coordinate;
the control device is further used for determining the space coordinates corresponding to the preset mark points by combining the ellipse center coordinates based on the corresponding relation between the pre-stored space coordinate system and the ellipse center coordinates;
the control device is further used for determining displacement parameters based on the space coordinates of each preset mark point, wherein the displacement parameters are displacement when the engine structure to be tested is in a swinging state relative to the engine structure to be tested in a zero state.
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