Method and device for measuring and calculating sight line of space target of strapdown platform

Abstract

The invention relates to the technical field of aircraft navigation and detection, and provides a space target sight line measurement and calculation method and device of a strapdown platform. The method comprises the following steps: determining a navigation star catalogue by using a sensitivity requirement and a view field requirement of target detection, determining sight angles of all targets and background fixed stars in a view field relative to a platform system by tracking a task target, and determining inertial system sight directions of all targets and background fixed stars except the task target by using the sight angles; meanwhile, background fixed star map matching is carried out, and the inertial system sight angle of the task target is determined based on the inertial system sight direction vector under the condition of partial matching results, so that the influence of platform attitude measurement errors, information asynchronous errors, installation errors, platform elastic vibration and the like on inertial system sight angle calculation can be isolated; and the inertial system sight angle calculation precision is obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aircraft navigation and detection technology, and in particular to a space target line-of-sight measurement calculation method and device of a strapdown platform. BACKGROUND

[0002] As a target detection device, optical cameras are increasingly used in fields such as Earth spacecraft and deep space exploration. In order to reduce system complexity and improve reliability, most optical cameras are installed on aircraft in a strapdown manner. Through optical imaging and photoelectric information processing, an optical camera can usually measure the line-of-sight angle of a target, but for a strapdown installation, the line-of-sight angle measurement result directly obtained is coupled with the motion information of the installation platform (hereinafter referred to as the platform), and in order to complete functions such as aircraft navigation, target guidance and target identification, the coupled motion of the platform in the measurement result needs to be decoupled to obtain the line-of-sight angle of the target in the inertial reference system.

[0003] In related technologies, the line-of-sight angle of the target relative to the inertial system is obtained by synthesizing the platform attitude angle information and the line-of-sight angle information of the target relative to the platform system. The main advantage of this type of method is that the principle is clear, but there are important problems such as rough modeling and large errors in various types of information used.

[0004] Or by processing the target image in blocks to improve the accuracy of the line-of-sight angle of the target relative to the platform system, and by using multiple sources such as gyroscopes and accelerometers to calculate the platform attitude and making a combined filter to improve the accuracy of the platform attitude data, the purpose of improving the decoupling accuracy of the line-of-sight angle is achieved. This type of method can theoretically improve the accuracy of the results, but the actual performance improvement is limited, because the relative line-of-sight angle can generally achieve high measurement accuracy, and its error is not the main factor affecting the final error; the attitude angle error has a relatively large impact on the result, but the method used in this paper is to average two types of inertial attitude determination, and due to the current industrial level, the accuracy of inertial attitude determination is very limited.

[0005] Or the cross-correlation function method is used to estimate the relative time difference between the seeker data information and the platform attitude angle information, and then the platform attitude data is delayed and decoupled with the seeker to eliminate the significant impact caused by the time delay. This type of method has made significant progress in improving the decoupling accuracy of the line-of-sight angle, but is affected by the estimation accuracy of the delay time, and does not fully consider other possible errors such as the installation error between the camera and the attitude determination system, and the influence of system elastic vibration, so there is potential for further improvement.

[0006] Therefore, there is an urgent need for a more efficient space target line-of-sight measurement calculation method of a strapdown platform to achieve high-precision target detection. SUMMARY

[0007] Therefore, the application provides a space target line-of-sight measurement calculation method and device for a strapdown platform, to solve the problem of insufficient target detection accuracy caused by the influence of platform attitude measurement error, information asynchronization error, installation error, platform elastic vibration and the like on inertial system line-of-sight angle calculation in the prior art.

[0008] In a first aspect, the application provides a space target line-of-sight measurement calculation method for a strapdown platform, comprising:

[0009] obtaining sensitivity requirement and field of view requirement of target detection, determining camera sensitivity capability in the strapdown platform based on the sensitivity requirement, and determining a navigation star table according to the camera sensitivity capability;

[0010] determining a task target through detection, capture and identification, tracking the task target based on an instruction direction of a current optical axis, and determining line-of-sight angles of all targets and background stars in a field of view relative to a platform system in the strapdown platform based on a tracking result;

[0011] obtaining a platform attitude, determining inertial system line-of-sight direction vectors of all targets and background stars except the task target based on the platform attitude and the line-of-sight angles of the platform system;

[0012] performing background star atlas matching based on the field of view requirement and the navigation star table, to obtain an atlas matching result;

[0013] determining an inertial system line-of-sight angle of the task target based on the atlas matching result; wherein at least part of the inertial system line-of-sight angle is determined according to the inertial system line-of-sight direction vectors;

[0014] obtaining an instruction direction of a next frame optical axis, and iteratively performing the steps of tracking the task target, determining the inertial system line-of-sight direction vectors of all targets and background stars except the task target, matching target-star pair information and determining the inertial system line-of-sight angle of the task target, until the tracking task of the task target is completed.

[0015] In a second aspect, the application provides a space target line-of-sight measurement calculation device for a strapdown platform, comprising:

[0016] an obtaining module configured to obtain sensitivity requirement and field of view requirement of target detection, determine camera sensitivity capability in the strapdown platform based on the sensitivity requirement, and determine a navigation star table according to the camera sensitivity capability;

[0017] a tracking module configured to determine a task target through detection, capture and identification, track the task target based on an instruction direction of a current optical axis, and determine line-of-sight angles of all targets and background stars in a field of view relative to a platform system in the strapdown platform based on a tracking result;

[0018] The acquisition module is also configured to acquire the platform attitude and determine the inertial frame line-of-sight vectors of all targets other than the mission target and background stars based on the platform attitude and the line-of-sight angle of the platform system.

[0019] The matching module is configured to perform background star map matching based on field of view requirements and navigation star catalog, and record the information of successfully matched target-star pairs;

[0020] The determination module is configured to determine the inertial frame line-of-sight angle of the mission target based on the star map matching results; wherein at least a portion of the inertial frame line-of-sight angle is determined based on the inertial frame line-of-sight direction vector;

[0021] The iterative module is configured to obtain the instruction direction of the optical axis in the next frame, and iteratively execute the steps of tracking the mission target, determining the inertial frame line-of-sight direction vectors of all targets other than the mission target and background stars, matching target-star pair information, and determining the inertial frame line-of-sight angle of the mission target, until the mission target tracking task is completed.

[0022] A third aspect of this application provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the above-described method.

[0023] A fourth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the above-described method.

[0024] The beneficial effects of the embodiments of this application compared with the prior art are:

[0025] This application's embodiments utilize the sensitivity and field-of-view requirements for target detection to determine the navigation star catalog. By tracking the mission target, the line-of-view angles of all targets and background stars within the field of view relative to the platform system are determined. These line-of-view angles are then used to determine the inertial frame line-of-view directions of all targets except the mission target and background stars. Simultaneously, background star map matching is performed. Under partial matching conditions, the inertial frame line-of-view angle of the mission target is determined based on the inertial frame line-of-view direction vector. This approach can isolate the influence of platform attitude measurement errors, information asynchrony errors, installation errors, platform elastic vibrations, etc., on the calculation of the inertial frame line-of-view angle, significantly improving the accuracy of the inertial frame line-of-view angle calculation. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 is a flowchart of a space target line-of-sight measurement calculation method of a strapdown platform provided by an embodiment of the present application.

[0028] Figure 2 is a flowchart of a method for determining a field of view requirement of target detection and camera sensitivity capability provided by an embodiment of the present application.

[0029] Figure 3 is a flowchart of a method for determining a navigation star table according to camera sensitivity capability provided by an embodiment of the present application.

[0030] Figure 4 is an inertial system diagram provided by an embodiment of the present application.

[0031] Figure 5 is a platform system diagram provided by an embodiment of the present application.

[0032] Figure 6 is a flowchart of another space target line-of-sight measurement calculation method of a strapdown platform provided by an embodiment of the present application.

[0033] Figure 7 is a schematic diagram of a space target line-of-sight measurement calculation device of a strapdown platform provided by an embodiment of the present application.

[0034] Figure 8 is a schematic diagram of an electronic device provided by an embodiment of the present application. DETAILED DESCRIPTION

[0035] In the following description, specific details are set forth, such as particular system configurations, techniques, etc., in order to provide a thorough understanding of the embodiments of the present application. However, persons skilled in the art will understand that the present application can be practiced without these specific details. In other instances, well-known structures, devices, circuits, and methods have not been described in detail in order to avoid obscuring the present application.

[0036] A space target line-of-sight measurement calculation method and device of a strapdown platform according to an embodiment of the present application will be described in detail below with reference to the accompanying drawings.

[0037] As mentioned above, most optical cameras on aircrafts currently adopt a strapdown installation method. Among them, "strapdown installation" means that a device is fixedly installed on a platform and the device does not have relative motion capability relative to the platform, typical examples of which include a strapdown installed inertial measurement unit (IMU), a strapdown installed camera or seeker, etc. Taking the IMU as an example, in contrast, there is a platform installed IMU, in which the IMU has self-motion capability relative to the satellite platform.

[0038] For the strapdown installation mode, the line-of-sight angle of the target in the inertial reference system is obtained by decoupling the platform coupling motion in the measurement results. The decoupling methods in the related art are difficult to meet the application requirements in terms of precision.

[0039] In view of this, the embodiments of the present application provide a space target line-of-sight measurement calculation method for a strapdown platform. The navigation star table is determined according to the sensitivity requirement and the field of view requirement of target detection, the line-of-sight angles of all targets and background stars in the field of view relative to the platform system are determined according to the tracking task target, the inertial system line-of-sight directions of all targets and background stars except the task target are determined according to the line-of-sight angles, the background star atlas matching is performed at the same time, and the inertial system line-of-sight angle of the task target is determined based on the inertial system line-of-sight direction vector under the condition of partial matching results. The influence of the platform attitude measurement error, the information asynchronization error, the installation error and the platform elastic vibration on the inertial system line-of-sight angle calculation can be isolated, and the calculation precision of the inertial system line-of-sight angle is significantly improved.

[0040] Figure 1 FIG. 1 is a flowchart of a space target line-of-sight measurement calculation method for a strapdown platform provided by the embodiments of the present application. As shown in FIG. 1, the method comprises the following steps: Figure 1

[0041] In step S101, the sensitivity requirement and the field of view requirement of target detection are obtained, the camera sensitivity capability in the strapdown platform is determined based on the sensitivity requirement, and the navigation star table is determined according to the camera sensitivity capability.

[0042] In step S102, the task target is determined by detection, capture and identification, the task target is tracked based on the instruction direction of the current optical axis pointing, and the line-of-sight angles of all targets and background stars in the field of view relative to the platform system in the strapdown platform are determined based on the tracking result.

[0043] In step S103, the platform attitude is obtained, and the inertial system line-of-sight direction vector of all targets and background stars except the task target is determined based on the platform attitude and the line-of-sight angles of the platform system.

[0044] In step S104, the background star atlas matching is performed based on the field of view requirement and the navigation star table, and the atlas matching result is obtained.

[0045] In step S105, the inertial system line-of-sight angle of the task target is determined based on the atlas matching result.

[0046] At least part of the inertial system line-of-sight angle is determined according to the inertial system line-of-sight direction vector.

[0047] ​In step S106, the next frame optical axis pointing direction is acquired, and the steps of tracking the task target, determining the inertial system line-of-sight direction vectors of all targets and background stars except the task target, matching target-star pair information, and determining the inertial system line-of-sight angle of the task target are iteratively executed until the tracking task of the task target is completed.

[0048] In some embodiments of the present application, the method can be executed by a server or a terminal device with certain processing capability.

[0049] In some embodiments of the present application, the sensitivity requirement and the field of view requirement of target detection can be acquired, the camera sensitivity capability in the strapdown platform is determined based on the sensitivity requirement, and the navigation star catalog is determined according to the camera sensitivity capability.

[0050] In some embodiments of the present application, the task target can also be determined through detection, capture, and identification, the task target is tracked based on the instruction direction of the current optical axis pointing direction, and the line-of-sight angles of all targets and background stars in the field of view relative to the platform system in the strapdown platform are determined based on the tracking result.

[0051] In some embodiments of the present application, the sensitivity requirement and the field of view requirement of target detection can be acquired, the camera sensitivity capability in the strapdown platform is determined based on the sensitivity requirement, and the navigation star catalog is determined according to the camera sensitivity capability.

[0052] In some embodiments of the present application, the platform attitude can be acquired, and the inertial system line-of-sight direction vectors of all targets and background stars except the task target are determined based on the platform attitude and the line-of-sight angles of the platform system.

[0053] Meanwhile, background star atlas matching can also be performed based on the field of view requirement and the navigation star catalog to obtain a star atlas matching result. Then, the inertial system line-of-sight angle of the task target is determined based on the star atlas matching result. Under the condition of part of the star atlas matching result, the inertial system line-of-sight angle can be determined according to the inertial system line-of-sight direction vector. Under the condition of another star atlas matching result, the inertial system line-of-sight angle can be determined according to the platform attitude.

[0054] In some embodiments of the present application, the next frame optical axis pointing direction can also be acquired, and the steps of tracking the task target, determining the inertial system line-of-sight direction vectors of all targets and background stars except the task target, matching target-star pair information, and determining the inertial system line-of-sight angle of the task target are iteratively executed until the tracking task of the task target is completed.

[0055] According to the technical scheme provided in the embodiments of the present application, the navigation star table is determined according to the sensitivity requirement and the field of view requirement of target detection, the line of sight angle of all targets and background stars in the field of view relative to the platform system is determined through tracking the mission target, the line of sight direction of all targets and background stars except the mission target in the inertial system is determined according to the line of sight angle, and the line of sight angle of the mission target in the inertial system is determined based on the line of sight direction vector under the condition of partial matching results in the background star map matching, so that the influence of the platform attitude measurement error, information asynchronization error, installation error and platform elastic vibration on the calculation of the line of sight angle in the inertial system is isolated, and the calculation precision of the line of sight angle in the inertial system is significantly improved.

[0056] Figure 2 is a flowchart of a method for determining the field of view requirement and the camera sensitivity capability of target detection provided in the embodiments of the present application. As shown in Figure 2 , the method comprises the following steps:

[0057] In step S201, the initial field of view requirement and the background star detection quantity requirement of target detection are acquired.

[0058] In step S202, the camera sensitivity capability is determined based on the sensitivity requirement of target detection.

[0059] In step S203, the minimum field of view requirement of the camera is determined according to the camera sensitivity capability and the background star detection quantity requirement.

[0060] In step S204, the maximum value between the initial field of view requirement and the minimum field of view requirement is determined as the comprehensive field of view requirement.

[0061] In step S205, in response to determining that the comprehensive field of view requirement is greater than a preset field of view threshold, the camera sensitivity capability is increased, and the comprehensive field of view requirement of the camera is re-determined using the increased sensitivity capability and the background star detection quantity requirement, until the re-determined comprehensive field of view requirement is less than or equal to the preset field of view threshold.

[0062] In step S206, the comprehensive field of view requirement less than or equal to the preset field of view threshold is determined as the field of view requirement of target detection, and the sensitivity capability corresponding to the comprehensive field of view requirement less than or equal to the preset field of view threshold is determined as the camera sensitivity capability.

[0063] In some embodiments of the present application, the initial field of view requirement and the background star detection quantity requirement of target detection can be acquired first, and the camera sensitivity capability is determined based on the sensitivity requirement of target detection.

[0064] Then, the minimum field of view requirement of the camera is determined according to the camera sensitivity capability and the background star detection quantity requirement, and the maximum value between the initial field of view requirement and the minimum field of view requirement is determined as the comprehensive field of view requirement.

[0065] If the total field of view requirement is greater than the preset field of view threshold, the camera sensitivity capability can be increased, and the total field of view requirement of the camera is re-determined using the increased sensitivity capability and the background star detection number requirement, until the re-determined total field of view requirement is less than or equal to the preset field of view threshold.

[0066] Finally, the total field of view requirement less than or equal to the preset field of view threshold is determined as the field of view requirement of the target detection, and the sensitivity capability corresponding to the total field of view requirement less than or equal to the preset field of view threshold is the camera sensitivity capability.

[0067] In the embodiments of the present application, it is required that the camera field of view includes two or more detectable background stars.

[0068] In some examples, for a task target of interest, if the expected detection distance is set to be not less than 600 km, it is calculated that the equivalent apparent magnitude of the target at 600 km is 5.8, therefore, the sensitivity requirement of the target detection should be not less than 5.8, and a certain margin is reserved, and the sensitivity requirement is set to be 6. At the same time, the initial field of view requirement of the target detection can be obtained according to the platform navigation error, target position prediction error and other target capture influencing factors, and the initial field of view requirement of the target detection is not less than , that is, the initial field of view requirement of the target detection .

[0069] It is assumed that the camera sensitivity capability is equal to the above-determined sensitivity requirement 6, and the number of background stars in the camera field of view is 2.5 by reserving a certain margin, that is, the background star detection number requirement is 2.5, then the minimum field of view angle requirement for detecting the background stars can be calculated by the formula , wherein ; wherein is the camera sensitivity capability, is the background star detection number requirement.

[0070] can be calculated , and is obtained. If the is less than the preset field of view threshold, the calculation is stopped, and the is taken as the field of view requirement of the target detection, and the camera sensitivity capability is not adjusted any more.

[0071] In other examples, if the calculated is too large, for example, greater than or equal to the preset field of view threshold, the camera sensitivity capability can be appropriately increased, and the above steps are returned to re-calculate the total field of view requirement , until the requirement is met.

[0072] Figure 3is a flowchart of a method for determining a navigation star table according to camera sensitivity capability provided by an embodiment of the present application. As shown in Figure 3 the method comprises the following steps:

[0073] In step S301, a basic navigation star table is acquired.

[0074] wherein the limiting magnitude in the basic navigation star table is greater than or equal to the visual magnitude value corresponding to the camera sensitivity capability; the limiting magnitude is the maximum magnitude value in the basic navigation star table, and the magnitude value of a star is negatively related to the brightness.

[0075] In step S302, the stars in the basic navigation star table with the magnitude value greater than or equal to the visual magnitude value corresponding to the camera sensitivity capability are removed to obtain the navigation star table.

[0076] In some embodiments of the present application, when the navigation star table is determined, the basic navigation star table can be acquired first; the limiting magnitude in the basic navigation star table is greater than or equal to the visual magnitude value corresponding to the camera sensitivity capability; the limiting magnitude is the maximum magnitude value in the basic navigation star table, and the magnitude value of a star is negatively related to the brightness.

[0077] For example, the visual magnitude value corresponding to the camera sensitivity capability can be determined, and the basic star table with the darkest limiting magnitude not lower than the visual magnitude value corresponding to the camera sensitivity capability is selected, such as the SAO star table and the HIP star table prepared by the Smithsonian Astrophysical Observatory.

[0078] Then the stars in the basic navigation star table with the magnitude value greater than the visual magnitude value corresponding to the camera sensitivity capability are removed to obtain the navigation star table.

[0079] If the visual magnitude value corresponding to the camera sensitivity capability is 5th magnitude, the stars in the basic navigation star table with the magnitude value greater than 5th magnitude are all darker than 5th magnitude, and thus cannot be detected by the camera, so these stars can be removed from the basic navigation star table to obtain the navigation star table.

[0080] In some embodiments of the present application, the line-of-sight angles of all target and background stars in the field of view relative to the platform system in the strapdown platform include the elevation line-of-sight angle and the azimuth line-of-sight angle of the mission target relative to the platform system, and the elevation line-of-sight angle and the azimuth line-of-sight angle of all target and background stars except the mission target relative to the platform system, wherein N is the total number of all target and background stars except the mission target, and all target and background stars except the mission target are denoted as .

[0081] The line-of-sight direction vector of the inertial system is determined in the following manner: wherein, is the line-of-sight direction vector of the inertial system, is the line-of-sight direction vector of the inertial system, is the line-of-sight direction vector of the inertial system, is the direction vector in the platform system, is the platform inertial system attitude quaternion corresponding coordinate conversion matrix.

[0082] That is, one task target and N other targets or background stars may be obtained from the tracking image processing result. The altitude and azimuth line-of-sight angles of the task target relative to the platform system are The altitude and azimuth line-of-sight angles of the other N targets relative to the platform system are .

[0083] In some examples, the inertial system can be the J2000 equatorial inertial system. Referring to Figure 4 , the origin is located at the center of the Earth, XOY is located on the equatorial plane, X points to the direction of the equinox point in the inertial space, and Z is perpendicular to the equatorial plane and points to the North Pole.

[0084] The platform system refers to Figure 5 , the Z axis points to the center of the Earth during flight, the X axis points to the front, and the Y axis points to the right; the axes of the camera system are installed in parallel corresponding to the axes of the platform system, the optical axis is along the +X direction, and the rotation around the +Y axis is the positive direction of the altitude relative line-of-sight angle, and the rotation around the +Z axis is the positive direction of the azimuth relative line-of-sight angle.

[0085] The true value of the attitude quaternion of the platform relative to the inertial system is set as , and the corresponding coordinate conversion matrix is ; the true value of the direction vector of the optical axis in the inertial system is , and the corresponding right ascension and declination are . Combined with the camera field of view and detection sensitivity, the true value information of the task target and visible background stars in the field of view is set as shown in Table 1:

[0086] Table 1 True value information of all targets in the field of view of a frame target detection

[0087]

[0088] According to the camera detection and image processing accuracy, the maximum measurement error of the relative line-of-sight angle is set to about 10″ (0.0028°), and the measurement error is randomly generated to obtain one task target and three other targets or background stars The relative platform system height, azimuth, and line-of-sight angle measurement values are shown in Table 2:

[0089] Table 2. Relative line-of-sight angles of all targets obtained by processing a frame of image

[0090]

[0091] Thus, the line-of-sight angles of all targets and background stars in the field of view relative to the line-of-sight angles of the strapdown platform system can be determined.

[0092] Further, let the platform inertial system attitude quaternion be The direction vector of the target in the platform system can be obtained from the relative line-of-sight angle of the target , denoted as The direction vector of the target in the inertial system is : ; wherein represents the coordinate transformation matrix corresponding to the attitude quaternion . This is the line-of-sight direction vector of all targets and background stars in the inertial system except for the task target.

[0093] In some examples, due to measurement errors, installation errors, and various factors such as the camera measurement time not being synchronized, the maximum error ultimately reflected in the platform attitude navigation result can be about 0.15°. Accordingly, a random attitude error is generated, and the platform relative inertial system attitude quaternion navigation value is , and the corresponding coordinate transformation matrix is ; the direction vector of the target in the platform system is obtained by combining the attitude coordinate transformation matrix and the relative line-of-sight angle measurement value. The direction vector of the target in the inertial system is shown in Table 3. The information of the task target is also calculated for subsequent comparison of accuracy.

[0094] Table 3. Navigation calculation results of the direction vectors of the targets in the platform system and the inertial system

[0095]

[0096] Next, background star atlas matching can be performed. In some embodiments, if , then the background star atlas matching can not be performed, and the subsequent step of determining the inertial system line-of-sight angle of the task target can be directly executed.

[0097] In other embodiments, if​ Then the camera optical axis direction vector in the inertial system can be determined based on the platform inertial system attitude quaternion , camera mounting mode and the direction of the camera optical axis in the body system . The right ascension of the optical axis direction is calculated by inverse trigonometric calculation and the declination .

[0098] Then all the stars in the navigation star catalog that meet the following conditions are determined as backup matching stars: ; wherein is the field of view requirement, represents the platform attitude pointing accuracy, is the right ascension of the star in the navigation star catalog, is the declination of the star in the navigation star catalog, is a positive integer greater than or equal to 1 and less than or equal to the number of stars in the navigation star catalog.

[0099] The inertial system direction vector of each backup matching star is determined based on the right ascension and declination of each backup matching star . And is matched with each backup matching star, and a match is confirmed to be successful when the following conditions are met: ; wherein represents the angle between the vectors and , and represents a preset matching judgment threshold. Finally, the target-star pair information of the matching successful target-star pair is recorded as , is the number of matching successful target-star pairs, is the backup matching star matched with .

[0100] In some examples, if it is assumed that , then the background star map matching can be performed. The direction vector of the camera optical axis in the platform system is , and combined with the platform attitude coordinate conversion matrix, its navigation component in the inertial system can be obtained and expressed as , the corresponding right ascension and declination are . A certain margin is reserved, and the pointing error is taken to perform matching navigation star rough selection, and a total of 27 backup matching stars that meet the conditions are obtained, the right ascension, declination and inertial system direction vector of each star are as shown in Table 4:

[0101] Table 4 Backup matching stars for a frame star map matching

[0102] The matching threshold is set by comprehensively considering the platform attitude measurement error and the camera measurement error level The star map matching is performed, and the matching results are shown in Table 5, and a total of 3 target-star matching pairs are completed.

[0103] Table 5: Star map matching results of a frame

[0104]

[0105] That is, according to the true value information of the target and the background star in the current field of view of the camera given in Table 1, it can be known that if it is a star, the corresponding star number HIP, in addition, the text below Table 1 records the target in Table 1 as , and the three background stars are recorded as .

[0106] Subsequently, Table 2 obtains the high and low, azimuth line-of-sight angle measurement values of the target and the three background stars relative to the platform system according to the true value and the platform attitude of Table 1. At the same time, Table 4 gives the backup matching stars selected from the navigation star map library. Since the information is obtained from the star library, there is also the star number HIP information.

[0107] The process of star map matching is to pair with , and whether the pairing result is correct is determined by whether the two correspond to the same HIP number. Because HIP is a non-repeating number of all stars in the whole sky area, taking the first matching result in Table 5 as an example, it can be seen from Table 1 that (the background star 1 in Table 1) has a HIP number of 26385, and it can be seen from Table 4 that also has a HIP number of 26385, and the two are consistent, so the first matching result is correct; the other two matching results in Table 5 are similar.

[0108] Therefore, by comparing the information in Table 1 and Table 4, especially the HIP information, it can be determined that the matching results in Table 5 are correct.

[0109] In some embodiments of the present application, the line-of-sight angle of the target in the inertial system can be determined based on the star map matching result.

[0110] ​In some embodiments, the platform attitude matrix of the backup matching star can be determined based on the star map matching result first.

[0111] On one hand, if , the platform attitude matrix of the backup matching star can be determined directly as the coordinate conversion matrix .

[0112] On the other hand, if , the key matrix of the backup matching star can be determined first as ; wherein, is the key matrix, is the inertial system direction vector of the backup matching star ; then singular value decomposition is performed on the key matrix to obtain ; wherein, is the left singular vector matrix, is the singular value matrix, is the right singular vector matrix; finally, the platform attitude matrix of the backup matching star is determined based on the singular value decomposition result; wherein, , denotes the determinant of the calculation matrix.

[0113] Further, the direction vector of the task target under the platform system can be determined based on the line-of-sight angle of the task target relative to the platform system , and the high-precision direction vector of the task target under the inertial system ; wherein, is the high-precision direction vector.

[0114] Finally, the high-precision high-low line-of-sight angle and the high-precision azimuth line-of-sight angle of the task target can be obtained by performing inverse trigonometric calculation on the high-precision direction vector.

[0115] Still taking the number of matching successful "target-star pairs" as an example, the high-precision platform attitude coordinate conversion matrix and the inertial system high-low and azimuth line-of-sight angle calculation can be performed. According to the "target-star pair" information matched successfully in the last step, the key matrix is defined and singular value decomposition is performed thereon, and the result is:

[0116] ;

[0117] ;

[0118] ​​ ;

[0119] Computing platform attitude matrix , the result is:

[0120] ;

[0121] According to the task target The relative line-of-sight angle Get its direction vector under the platform system , and then get The high-precision direction vector in the inertial system is . Check the error between the navigation value obtained in Table 3 and the true value given in Table 1, the result is as follows:

[0122] ;

[0123] ;

[0124] Therefore, the calculation accuracy of the embodiments of the application is much higher than that of the conventional method.

[0125] Further, with reference to Figure 4 , for the taken inertial system, define the rotation around the -Y axis as the positive direction of the high-low line-of-sight angle, and the rotation around the +Z axis as the positive direction of the azimuth line-of-sight angle, based on the definition, for Using inverse trigonometric calculation, the target The high-precision high-low and azimuth line-of-sight angle results in the inertial system are .

[0126] In some embodiments of the application, the instruction direction of the next frame optical axis pointing can also be calculated. Wherein, the next frame optical axis pointing needs to meet that the deviation of the task target and the matching successful background star from the center of the camera field of view is less than a preset deviation threshold.

[0127] A recommended instruction direction calculation method of the next frame optical axis pointing can be ; wherein is the instruction direction vector of the next frame optical axis pointing, represents the weight of the optical axis pointing task target , and the typical value can be .

[0128] In some examples, the recommended optical axis instruction direction calculation method can be used, the weight of the optical axis pointing task target is taken as , and the inertial system optical axis instruction direction calculation result is , which is realized by the attitude control of the platform.

[0129] Figure 6 is another flow diagram of a space target line-of-sight measurement calculation method of a strapdown platform provided by an embodiment of the present application. As shown in Figure 6 , the method can include two stages. In the first stage, the sensitivity requirement and the field of view requirement of target detection can be acquired, and then the comprehensive field of view requirement can be calculated. When it is judged that the comprehensive field of view requirement obtained in the last step is too large, the comprehensive field of view requirement can be calculated again after the sensitivity capability of the camera is improved, until a reasonable comprehensive field of view requirement is obtained. Then the camera sensitivity capability can be used to complete the design of the navigation star table, and target detection can be performed to complete the capture and identification of the mission target.

[0130] In the second stage, target tracking and image processing can be performed to obtain the background star relative line-of-sight angle of all targets in the field of view, and the inertial system line-of-sight direction vector can be calculated according to the platform attitude. Then the background star atlas matching is performed, and the mission target inertial system line-of-sight angle is calculated according to the star atlas matching result and the mission target relative line-of-sight angle.

[0131] After the instruction direction of the optical axis pointing of the current frame is completed, the steps in the second stage can be iteratively executed to calculate the instruction direction of the optical axis pointing of the next frame in turn.

[0132] All the optional technical solutions described above can be combined to form optional embodiments of the present application, which will not be described one by one here.

[0133] The following is a device embodiment of the present application, which can be used to execute the method embodiments of the present application. For details not disclosed in the device embodiments of the present application, please refer to the method embodiments of the present application.

[0134] Figure 7 is a schematic diagram of a space target line-of-sight measurement calculation device of a strapdown platform provided by an embodiment of the present application. As shown in Figure 7 , the device includes:

[0135] The acquisition module 701 is configured to acquire the sensitivity requirement and the field of view requirement of target detection, determine the sensitivity capability of the camera in the strapdown platform based on the sensitivity requirement, and determine the navigation star table according to the sensitivity capability of the camera.

[0136] The tracking module 702 is configured to determine the mission target by detection, capture and identification, track the mission target based on the instruction direction of the current optical axis pointing, and determine the line-of-sight angle of all targets and background stars in the field of view relative to the platform system in the strapdown platform based on the tracking result.

[0137] The acquisition module 701 is further configured to acquire the platform attitude, and determine the inertial system line-of-sight direction vector of all targets and background stars except the mission target based on the platform attitude and the line-of-sight angle of the platform system.

[0138] The matching module 703 is configured to perform background star map matching based on the field of view requirement and the navigation star catalog, and record the target-star pair information of successful matching.

[0139] The determining module 704 is configured to determine the inertial system line-of-sight angle of the task target based on the star map matching result; wherein at least part of the inertial system line-of-sight angle is determined according to the inertial system line-of-sight direction vector.

[0140] The iteration module 705 is configured to obtain the instruction direction of the optical axis pointing of the next frame, and iteratively perform the steps of tracking the task target, determining the inertial system line-of-sight direction vector of all targets and background stars except the task target, matching the target-star pair information, and determining the inertial system line-of-sight angle of the task target, until the tracking task of the task target is completed.

[0141] According to the technical scheme provided in the embodiments of the present application, the navigation star catalog is determined by using the sensitivity requirement and the field of view requirement of target detection, and the line-of-sight angle of all targets and background stars in the field of view relative to the platform system is determined by tracking the task target, and the inertial system line-of-sight direction of all targets and background stars except the task target is determined by using the line-of-sight angle; at the same time, the background star map matching is performed, and under the condition of part of the matching result, the inertial system line-of-sight angle of the task target is determined based on the inertial system line-of-sight direction vector, which can isolate the influence of platform attitude measurement error, information asynchronization error, installation error, platform elastic vibration, etc. on the calculation of the inertial system line-of-sight angle, and significantly improve the calculation precision of the inertial system line-of-sight angle.

[0142] In some embodiments, the field of view requirement and the camera sensitivity capability of target detection are determined in the following manner: obtaining the initial field of view requirement of target detection and the background star detection quantity requirement; determining the camera sensitivity capability based on the sensitivity requirement of target detection; determining the minimum field of view requirement of the camera according to the camera sensitivity capability and the background star detection quantity requirement; determining the maximum value of the initial field of view requirement and the minimum field of view requirement as the comprehensive field of view requirement; in response to determining that the comprehensive field of view requirement is greater than a preset field of view threshold, increasing the camera sensitivity capability, and re-determining the comprehensive field of view requirement of the camera using the increased sensitivity capability and the background star detection quantity requirement, until the re-determined comprehensive field of view requirement is less than or equal to the preset field of view threshold; determining the comprehensive field of view requirement less than or equal to the preset field of view threshold as the field of view requirement of target detection, and the sensitivity capability corresponding to the comprehensive field of view requirement less than or equal to the preset field of view threshold as the camera sensitivity capability.

[0143] In some implementations, determining the navigation star catalog based on camera sensitivity capability includes: acquiring a basic navigation star catalog; the limiting magnitude in the basic navigation star catalog being greater than or equal to the apparent magnitude corresponding to the camera sensitivity capability; the limiting magnitude being the maximum magnitude value in the basic navigation star catalog, where the magnitude value of a star is negatively correlated with its brightness; and removing stars in the basic navigation star catalog whose magnitude values ​​are greater than the apparent magnitude corresponding to the camera sensitivity capability to obtain the navigation star catalog.

[0144] In some implementations, the line-of-sight angles of all targets and background stars within the field of view relative to the platform system in the strapdown platform include the elevation and elevation line-of-sight angles of the mission target relative to the platform system. and azimuth line of sight The high and low line-of-sight angles of all targets except the mission objective and background stars relative to the platform system. and azimuth line of sight , , This refers to the total number of all targets other than the mission objective and the background stars. All targets and background stars other than the mission objective are represented as follows: ; The inertial frame line-of-sight direction vector is determined in the following way: ,in, for The inertial frame of reference line of sight vector, for Direction vector within the platform system, For the platform's inertial frame attitude quaternion The corresponding coordinate transformation matrix.

[0145] In some implementations, background star map matching is performed based on field-of-view requirements and the navigation star catalog, including: in response to determining... Based on the platform's inertial frame attitude quaternion The camera mounting method and the direction of the camera's optical axis within its own system determine the direction vector of the camera's optical axis in the inertial frame. and to The right ascension of the optical axis is obtained by inverse trigonometric calculation. and declination All stars in the navigation star catalog that meet the following conditions are identified as backup matching stars: ;in, For field of view requirements, This indicates the platform's attitude pointing accuracy. For stars in the navigation star catalog The right ascension, For stars in the navigation star catalog declination, is a positive integer greater than or equal to 1 and less than or equal to the number of stars in the navigation star catalogue; determining an inertial system direction vector of the backup matching star based on the right ascension and declination of the backup matching star ; matching the target with each backup matching star and confirming a match is successful when the following condition is met: ; wherein, represents the included angle between the vectors and , represents a preset matching judgment threshold; recording the target-star pair information of the successful match as , , is the number of target-star pairs of the successful match, is the backup matching star matched with ; or, in response to determining , not performing the background star map matching.

[0146] In some embodiments, determining the inertial system line-of-sight angle of the mission target based on the star map matching result includes: in response to determining , determining the platform attitude matrix of the backup matching star as the coordinate conversion matrix ; in response to determining , determining the key matrix of the backup matching star as ; wherein, is the key matrix, is the inertial system direction vector of the backup matching star ; singular value decomposition is performed on the key matrix to obtain ; wherein, is the left singular vector matrix, is the singular value matrix, is the right singular vector matrix; determining the platform attitude matrix of the backup matching star based on the singular value decomposition result; wherein, , represents the determinant of the calculation matrix; determining the direction vector of the mission target in the platform system based on the line-of-sight angle of the mission target relative to the platform system, and determining the high-precision direction vector of the mission target in the inertial system; wherein, is the high-precision direction vector; performing inverse trigonometric calculation on the high-precision direction vector to obtain the high-precision high-low line-of-sight angle and the high-precision azimuth line-of-sight angle of the mission target.

[0147] In some embodiments, the next frame optical axis is directed to the center of the camera field of view with a deviation less than a preset deviation threshold from the center of the camera field of view of all background stars that need to be matched successfully.

[0148] It should be understood that the size of the serial number of each step in the above embodiments does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0149] Figure 8 FIG. 1 is a schematic diagram of an electronic device according to an embodiment of the present application. As shown in the figure, the electronic device 8 according to the embodiment of the present application includes a processor 801, a memory 802, and a computer program 803 stored in the memory 802 and executable on the processor 801. Figure 8 When the processor 801 executes the computer program 803, the steps in each of the above method embodiments are implemented. Alternatively, when the processor 801 executes the computer program 803, the functions of each module / unit in each of the above device embodiments are implemented.

[0150] The electronic device 8 can be a desktop computer, a notebook, a palm computer, a cloud server, and the like. The electronic device 8 can include but is not limited to the processor 801 and the memory 802. Those skilled in the art can understand that the electronic device 8 can include more or fewer components than those shown, or different components. Figure 8 The electronic device 8 is merely an example and does not constitute a limitation on the electronic device 8, and can include more or fewer components than those shown, or different components.

[0151] The processor 801 can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc.

[0152] The memory 802 can be an internal storage unit of the electronic device 8, for example, a hard disk or a memory of the electronic device 8. The memory 802 can also be an external storage device of the electronic device 8, for example, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. equipped on the electronic device 8. The memory 802 can also include both the internal storage unit and the external storage device of the electronic device 8. The memory 802 is used to store computer programs and other programs and data required by the electronic device.

[0153] It should be clearly understood by those skilled in the art that, for the convenience and brevity of description, only the above division of functional units and modules is exemplified, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit, and the integrated unit can be realized in the form of hardware or in the form of software functional unit.

[0154] The integrated module / unit, if realized in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on this understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. When the processor executes the computer program, the steps of the above-mentioned various method embodiments can be implemented. The computer program can include computer program code, which can be in the form of source code, object code, executable file or some intermediate form, etc. The computer readable medium can include any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier wave signal, telecommunication signal and software distribution medium, etc.

[0155] The above examples are only used to illustrate the technical solutions of the present application, but not limit the same; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent ones; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for measuring and calculating the line of sight to a spatial target on a strapdown platform, characterized in that, include: The sensitivity requirements and field of view requirements for target detection are obtained, the camera sensitivity capability in the strapdown platform is determined based on the sensitivity requirements, and the navigation satellite catalog is determined based on the camera sensitivity capability. The mission target is determined by detection, capture and identification, the mission target is tracked based on the command direction of the current optical axis, and the line-of-sight angle of all targets and background stars in the field of view is determined relative to the platform system in the strapdown platform based on the tracking results; Obtain the platform attitude, and based on the platform attitude and the line-of-sight angle of the platform system, determine the inertial frame line-of-sight direction vectors of all targets other than the mission target and background stars; Based on the field of view requirements and the navigation star catalog, a background star map matching is performed to obtain the star map matching result; The inertial frame line-of-sight angle of the mission target is determined based on the star map matching results; wherein, at least a portion of the inertial frame line-of-sight angle is determined based on the inertial frame line-of-sight direction vector; Obtain the instruction direction of the optical axis in the next frame, and iteratively execute the steps of tracking the mission target, determining the inertial frame line-of-sight direction vectors of all targets other than the mission target and background stars, matching target-star pair information, and determining the inertial frame line-of-sight angle of the mission target, until the mission target tracking task is completed.

2. The method according to claim 1, characterized in that, The target detection field of view requirements and camera sensitivity capabilities are determined as follows: The initial field of view required for target detection and the number of background stars required for detection; The camera sensitivity capability is determined based on the sensitivity requirements for target detection; The minimum field of view requirement for the camera is determined based on the camera's sensitivity capability and the required number of background stars to be detected. The maximum value between the initial field of view requirement and the minimum field of view requirement is determined as the comprehensive field of view requirement; In response to determining that the overall field of view requirement is greater than a preset field of view threshold, the camera sensitivity capability is increased, and the increased sensitivity capability and the background star detection quantity requirement are used to redetermine the camera's overall field of view requirement until the redetermined overall field of view requirement is less than or equal to the preset field of view threshold. The comprehensive field of view requirement that is less than or equal to the preset field of view threshold is determined as the field of view requirement for target detection, and the sensitivity capability corresponding to the comprehensive field of view requirement that is less than or equal to the preset field of view threshold is determined as the camera sensitivity capability.

3. The method according to claim 1, characterized in that, The navigation star catalog is determined based on camera sensitivity capabilities, including: Obtain a basic navigation star catalog; the limiting magnitude in the basic navigation star catalog is greater than or equal to the apparent magnitude corresponding to the camera's sensitivity capability; the limiting magnitude is the maximum magnitude value in the basic navigation star catalog, and the magnitude value of a star is negatively correlated with its brightness; The navigation star catalog is obtained by removing stars whose magnitudes in the basic navigation star catalog are greater than the apparent magnitudes corresponding to the camera's sensitivity capability.

4. The method according to claim 1, characterized in that, The line-of-sight angles of all targets and background stars within the field of view relative to the platform system in the strapdown platform include the elevation and elevation line-of-sight angles of the mission targets relative to the platform system. and azimuth line of sight The high and low line-of-sight angles of all targets except the mission objective and background stars relative to the platform system. and azimuth line of sight , , This refers to the total number of all targets other than the mission objective and the background stars. All targets and background stars other than the mission objective are represented as follows: ; The inertial frame line-of-sight direction vector is determined in the following way: ,in, for The inertial frame of reference line of sight vector, for Direction vector within the platform system, For the platform's inertial frame attitude quaternion The corresponding coordinate transformation matrix.

5. The method according to claim 4, characterized in that, Background star map matching based on the stated field of view requirements and the stated navigation star catalog includes: Response to determination Based on the platform's inertial frame attitude quaternion The camera mounting method and the direction of the camera's optical axis within its own system determine the direction vector of the camera's optical axis in the inertial frame. and the above The right ascension of the optical axis is obtained by inverse trigonometric calculation. and declination ; All stars in the navigation star catalog that meet the following conditions are identified as backup matching stars: ;in, For the aforementioned field of view requirements, This indicates the platform's attitude pointing accuracy. For stars in the navigation star catalog The right ascension, For stars in the navigation star catalog declination, A positive integer greater than or equal to 1 and less than or equal to the number of stars in the navigation star catalog; The inertial frame direction vector of the current backup matching star is determined based on the right ascension and declination of each backup matching star. ; Will Match with each of the backup matching stars, and confirm a successful match when the following conditions are met: ;in, Represents vector and The angle between them This indicates the preset matching threshold; Record the information of successfully matched target-star pairs. , To match the target - the number of star pairs, To and A successfully matched backup star; Or, in response to determination Background star map matching is not performed.

6. The method according to claim 5, characterized in that, Determining the inertial frame line-of-sight angle of the mission target based on the star map matching results includes: Response to determination Identify alternative matching stars Platform attitude matrix The coordinate transformation matrix ; Response to determination Identify alternative matching stars The key matrix is ;in, The key matrix, For the backup matching star The direction vector of the inertial frame; Perform singular value decomposition on the key matrix to obtain ;in, It is a left singular vector matrix. It is a singular value matrix. It is a right singular vector matrix; The alternative matching stars were determined based on the singular value decomposition results. Platform attitude matrix ;in, , Represents the calculation of the determinant of a matrix; Based on the line of sight of the task objective relative to the platform system Determine the direction vector of the mission objective within the platform architecture. And determine the high-precision orientation vector of the mission target in the inertial system. ;in, This refers to the high-precision direction vector; By performing inverse trigonometric calculations on the high-precision direction vector, the high-precision elevation and elevation line-of-sight angles of the mission target are obtained. and high-precision azimuth line of sight .

7. The method according to claim 1, characterized in that, The optical axis pointing in the next frame must ensure that the deviation between the target and all successfully matched background stars and the center of the camera's field of view is less than a preset deviation threshold.

8. A spatial target line-of-sight measurement and calculation device for a strapdown platform, characterized in that, include: The acquisition module is configured to acquire the sensitivity requirements and field of view requirements for target detection, determine the camera sensitivity capability in the strapdown platform based on the sensitivity requirements, and determine the navigation satellite catalog based on the camera sensitivity capability. The tracking module is configured to determine the mission target by detecting, capturing and identifying it, track the mission target based on the command direction of the current optical axis, and determine the line-of-sight angle of all targets and background stars in the field of view relative to the platform system in the strapdown platform based on the tracking results. The acquisition module is also configured to acquire the platform attitude and determine the inertial frame line-of-sight direction vectors of all targets other than the mission target and background stars based on the platform attitude and the line-of-sight angle of the platform system. The matching module is configured to perform background star map matching based on the field of view requirements and the navigation star catalog, and record the information of successfully matched target-star pairs; The determination module is configured to determine the inertial frame line-of-sight angle of the mission target based on the star map matching result; wherein at least a portion of the inertial frame line-of-sight angle is determined according to the inertial frame line-of-sight direction vector; The iterative module is configured to obtain the instruction direction of the optical axis in the next frame, and iteratively execute the steps of tracking the mission target, determining the inertial frame line-of-sight direction vectors of all targets other than the mission target and background stars, matching target-star pair information, and determining the inertial frame line-of-sight angle of the mission target, until the mission target tracking task is completed.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 7.

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