An embedded method for removing sailboards from non-cooperative targets in infrared space

Abstract

The present invention belongs to the field of aerospace technology, and discloses an embedded method for removing sailboards of non-cooperative infrared space targets, comprising the following steps: S1, merging a target body and its sailboard by utilizing the principle that the infrared radiation characteristics of the target body and its sailboard are similar; S2, removing the target sailboard by utilizing the coaxial characteristics of the body and the sailboard of the non-cooperative target; S3, recalculating the center of mass of the target body by utilizing the four vertex positions of the target body. The present invention calculates the center of mass position of the non-cooperative target body in real time by identifying the features of the infrared non-cooperative target, and can accurately obtain the center of mass of the target body, especially when the sailboard of a large non-cooperative tumbling target exceeds the imaging field of view, thereby solving the problem of rapid tracking stability of large targets and applying it.

Description

Technical Field

[0001] The present invention relates to the field of aerospace technology, and in particular to an identification and tracking method in the field of space on-orbit services. Background Art

[0002] In recent years, space on-orbit service technology has developed rapidly. Space target recognition and tracking is one of the key technologies of space on-orbit service, especially the tracking of non-cooperative targets. Since their motion characteristics are unknown, when approaching the target, how to quickly and accurately identify and stably track the target's center of mass is one of the difficulties.

[0003] The key to short-range relative navigation is to be able to accurately identify the target's motion characteristics, especially for targets that lack prior information. During the approach process, it is necessary to identify the target's shape, identify the sailboard and track it stably in real time, which is crucial to achieving the approach target. Summary of the invention

[0004] In order to solve the problem of sailboards of non-cooperative targets in space exceeding the imaging field of view, especially for tumbling targets, the present invention provides an embedded infrared non-cooperative large target sailboard removal method. This method is used to identify and track moving targets in space without human intervention, and can identify and track the target body in real time and stably. This method has been applied in orbit.

[0005] In order to achieve the above object, the present invention provides the following technical solution: an embedded infrared space non-cooperative target sailboard removal method, comprising the following steps:

[0006] S1. merging the target body and its sailboard by utilizing the principle that the infrared radiation characteristics of the target body and its sailboard are similar;

[0007] S2, using the coaxial characteristics of the main body and the sailboard of the non-cooperative target to remove the target sailboard;

[0008] S3. Recalculate the center of mass of the target body using the four vertex positions of the target body.

[0009] Furthermore, the specific merging method of step S1 is as follows:

[0010] S1.1. When the number of extracted cluster blocks is ≥3, cluster blocks with similar grayscale in cluster block N are re-clustered (grayscale difference ≤ preset value) to form a new cluster block N';

[0011] S1.2. Merge the cluster blocks in the new cluster block N' that satisfy the following formula:

[0012]

[0013] in , , are the weighted centroids of cluster blocks 1, 2, and 3 respectively.

[0014] Furthermore, the method for removing the sailboard in step S2 is as follows:

[0015] S2.1. First, calculate the rotation angle of the target. Use Hough transform to transform a given straight line in the original image space into a point in Hough space by using the duality of point and line. The formula of Hough transform is as follows:

[0016]

[0017] In the formula, and is the polar diameter and polar angle of the point in polar coordinates;

[0018] By fitting all the points on the detected straight line using the least squares method, the rotation angle of the target can be calculated. The specific formula is as follows:

[0019]

[0020] Where N is the number of samples; is the location of each sample;

[0021] S2.2. Calculate the center of mass based on the target's rotation angle k Polar coordinates ;

[0022] S2.3. Traverse the rows within the cluster block to find the valid points in the cluster block. , that is, the gray value of this point ≥ background gray + threshold, and calculate its polar coordinates ;if , then continue until Then exit and record the current ;

[0023] S2.4. Calculate the angle between the centroid and this point, The origin pair Traverse until the boundary is found, that is, the gray value of the previous point ≥ background gray value + threshold, and record the current value;

[0024] S2.5, The origin pair Traverse until the boundary is found, that is, the gray value of the previous point ≥ background gray value + threshold, and record the gray value at this time. ;

[0025] S2.6, when or When , it is considered that the centroid calculated by the clustering block is not on the target body, and it is necessary to remove the sailboard operation for this clustering block, that is, recalculate the centroid in the area after finding the body; when When , it is considered that the target has no sailboard, and there is no need to remove the sailboard from this cluster block;

[0026] S2.7, As the starting point, along the angle Traverse the vertical line on this straight line until the boundary is found, that is, the gray value of the previous point ≥ background gray value + threshold, and record the gray value at this time. ,when When , it is considered that an edge of the target entity is found; record the vertex at this time and ;

[0027] S2.8. Continue traversing until , record the vertex at this time and ; At this point, the positions of the four vertices of the main body have been obtained.

[0028] Furthermore, the specific calculation method of step S3 is as follows:

[0029] S3.1. Take the maximum and minimum values ​​in (x2, y2), (x3, y3), (x4, y4), (x5, y5) to reconstruct the calculation area. The formula is as follows:

[0030] ;

[0031] S3.2, according to the calculation Calculate the centroid within the region using the following formula:

[0032]

[0033] In the formula, is the newly solved center of mass position.

[0034] Compared with the prior art solutions, the present invention has the following beneficial effects:

[0035] This scheme uses the coaxial characteristics of the main body and sailboard of the non-cooperative target to first calculate the rotation angle of the target, and then remove the sailboard of the target according to this angle. The embedded infrared non-cooperative target sailboard removal method of this scheme is passive. When this method identifies the spacecraft on orbit, it can switch between large and small targets autonomously without human intervention and can track large targets stably in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic flow chart of an embedded infrared space non-cooperative target sailboard removal method of the present invention;

[0037] Figure 2 Schematic diagram of the relationship between Cartesian coordinates and polar coordinates in Hough transform in this embodiment;

[0038] Figure 3 Schematic diagram of Hough line transformation in this embodiment;

[0039] Figure 4 A schematic diagram of finding the target subject and removing the sailboard in this embodiment;

[0040] Figure 5 It is a schematic diagram of the application effect of an embedded infrared space non-cooperative target sailboard removal method of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0042] In this embodiment, the size of the target body is 2m 2m, the size of each sailboard is 2m 3m, the target surface is covered by a thermal control multilayer. This embodiment is only used to explain the present invention and cannot be interpreted as limiting the present invention.

[0043] like Figures 1 to 5 As shown, an embedded infrared space non-cooperative target sailboard removal method includes the following steps:

[0044] S1. Merge the target subject and its sailboard based on the principle that the infrared radiation characteristics of the target subject and its sailboard are similar. The specific merging method is as follows:

[0045] S1.1. When the extracted cluster blocks are ≥3, cluster blocks with similar grayscale in cluster block N are re-clustered (grayscale difference ≤ preset value) to form a new cluster block N'.

[0046] S1.2. Merge the cluster blocks in the new cluster block N' that satisfy the following formula:

[0047]

[0048] in , , are the weighted centroids of cluster blocks 1, 2, and 3 respectively.

[0049] S2. Using the coaxial property of the main body and the sailboard of the non-cooperative target, the target sailboard is removed; first, the rotation angle of the target is obtained, and then according to the rotation angle of the target, it is confirmed whether the calculated center of mass is on the target body. If the center of mass is not on the target body, the vertical line on the axis of the target and its sailboard is used for scanning, so as to obtain the positions of the four vertices of the main body and remove the target sailboard.

[0050] The removal method of the sailboard is as follows:

[0051] S2.1. First, calculate the rotation angle of the target. Use Hough transform to transform a given straight line in the original image space into a point in Hough space by using the duality of point and line. The formula of Hough transform is as follows:

[0052]

[0053] In the formula, and is the polar diameter and polar angle of a point in polar coordinates. It's a about , The sine curve of the line is similarly It will also form a group of , Sine curve, so there must be a , Intersection (i.e. perpendicular point ), a straight line can be detected by finding the number of curves that intersect at a point in polar coordinates. If more curves intersect at a point, it means that the straight line represented by this intersection point is composed of more points. By setting the threshold of the points on the straight line, we can define how many curves intersect at a point before we consider that a straight line is detected;

[0054] Then, the rotation angle of the target can be calculated by fitting the line using the least squares method based on all the points on the detected line. The specific formula is as follows:

[0055]

[0056] Where N is the number of samples; is the location of each sample;

[0057] S2.2. Calculate the center of mass based on the target's rotation angle k Polar coordinates ;

[0058] S2.3. Traverse the rows within the cluster block to find the valid points in the cluster block. , that is, the gray value of this point ≥ background gray + threshold, and calculate its polar coordinates ;if , then continue until Then exit and record the current ;

[0059] S2.4. Calculate the angle between the centroid and this point, The origin pair Traverse until the boundary is found (i.e. the gray value of the previous point ≥ background gray value + threshold), and record the current value;

[0060] S2.5, The origin pair Traverse until the boundary is found (i.e. the gray value of the previous point ≥ background gray value + threshold), and record the gray value at this time. ;

[0061] S2.6, when or When , it is considered that the centroid calculated by the clustering block is not on the target body, and it is necessary to remove the sailboard operation for this clustering block, that is, recalculate the centroid in the area after finding the body; when When , it is considered that the target has no sailboard, and there is no need to remove the sailboard from this cluster block;

[0062] S2.7, As the starting point, along the angle Traverse the vertical line on this straight line until the boundary is found (that is, the gray value of the previous point ≥ background gray value + threshold), and record the ,when When , it is considered that an edge of the target entity is found; record the vertex at this time and ;

[0063] S2.8. Continue traversing until , record the vertex at this time and ; At this point, the positions of the four vertices of the main body have been obtained.

[0064] S3. Recalculate the centroid of the target body using the four vertex positions of the target body, find the maximum and minimum values ​​from the four vertex positions of the body to recompose the calculation area, and finally recalculate the centroid of the target body within this area.

[0065] The specific calculation method is as follows:

[0066] S3.1. Take the maximum and minimum values ​​in (x2, y2), (x3, y3), (x4, y4), (x5, y5) to reconstruct the calculation area. The formula is as follows:

[0067] ;

[0068] S3.2, according to the calculation Calculate the centroid within the region using the following formula:

[0069]

[0070] In the formula, is the newly solved center of mass position.

[0071] In this embodiment, codes such as for loops, multiple loops, and if judgment statements are optimized to facilitate better processing by the DSP processor.

[0072] This solution calculates the center of mass of the non-cooperative target in real time by identifying the features of the infrared non-cooperative target. In particular, when the sailboard of a non-cooperative rolling target exceeds the imaging field of view, the center of mass of the target can be accurately obtained, solving the problem of stability in fast tracking of large targets and applying it. The experimental results of the embedded infrared non-cooperative target removal method proposed by the present invention are shown in Figure 1. Figure 5 As shown in FIG. 1 , the left side is the center of mass calculated without using this method, and the right side is the center of mass calculated with this method. It can be seen from the figure that the center of mass calculated with this method can completely fall on the target body.

[0073] The above is only an embodiment of the present invention, and the common knowledge such as the known specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the technical solution of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. An embedded infrared space non-cooperative target sailboard removal method, characterized in that: The steps include: S1. merging the target body and its sailboard by utilizing the principle that the infrared radiation characteristics of the target body and its sailboard are similar; S2. Using the coaxial characteristics of the main body and the sailboard of the non-cooperative target, remove the target sailboard, including: S2.

1. First, calculate the rotation angle of the target. Use Hough transform to transform a given straight line in the original image space into a point in Hough space by using the duality of point and line. The formula of Hough transform is as follows: ； In the formula, and is the polar diameter and polar angle of the point in polar coordinates; The rotation angle of the target can be calculated by fitting all the points on the detected straight line using the least squares method. The specific formula is as follows: ； Where N is the number of samples; is the location of each sample; S2.

2. Calculate the center of mass based on the target's rotation angle k Polar coordinates ; S2.

3. Traverse the range of the cluster block to find the valid points in the cluster block , that is, the gray value of this point ≥ background gray + threshold, and calculate its polar coordinates ;if , then continue until Then exit and record the current ; S2.

4. Calculate the angle between the centroid and this point, The origin pair Traverse until the boundary is found, that is, the gray value of the previous point ≥ background gray value + threshold, and record the current value; S2.5, The origin pair Traverse until the boundary is found, that is, the gray value of the previous point ≥ background gray value + threshold, and record the gray value at this time. ; S2.6, when or When , it is considered that the centroid calculated by the clustering block is not on the target body, and it is necessary to remove the sailboard operation for this clustering block, that is, recalculate the centroid in the area after finding the body; when When , it is considered that the target has no sailboard, and there is no need to remove the sailboard from this cluster block; S2.7, As the starting point, along the angle Traverse the vertical line on this straight line until the boundary is found, that is, the gray value of the previous point ≥ background gray value + threshold, and record the gray value at this time. ,when When , it is considered that an edge of the target entity is found; record the vertex at this time and ; S2.

8. Continue traversing until , record the vertex at this time and ; At this point, the positions of the four vertices of the subject have been obtained; S3. Recalculate the center of mass of the target body using the four vertex positions of the target body.

2. The embedded infrared space non-cooperative target sailboard removal method according to claim 1, characterized in that: The specific merging method of step S1 is as follows: S1.

1. When the number of extracted cluster blocks is ≥3, cluster blocks with similar grayscale in cluster block N are re-clustered according to the grayscale difference ≤ the preset value of the grayscale difference to form a new cluster block N'; S1.

2. Merge the cluster blocks in the new cluster block N' that satisfy the following formula: ； in , , are the weighted centroids of cluster blocks 1, 2, and 3 respectively.

3. The embedded infrared space non-cooperative target sailboard removal method according to claim 1, characterized in that: The specific calculation method of step S3 is as follows: S3.

1. Take the maximum and minimum values ​​in (x2, y2), (x3, y3), (x4, y4), (x5, y5) to reconstruct the calculation area. The formula is as follows: ； S3.2, according to the calculation Calculate the centroid within the region using the following formula: ； In the formula, is the newly solved center of mass position.

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