Carrier three-dimensional attitude determination method based on night polarized light field double-vector characteristics

Abstract

The invention relates to a carrier three-dimensional attitude determination method based on night polarized light field double-vector characteristics, which comprises the following steps: acquiring night sky polarized light field information, and acquiring an image plane coordinate system neutral point coordinate and a moon coordinate based on polarization distribution mode neutral surface characteristics; based on an imaging model, inversely solving a polarization neutral point vector and a moon vector under a carrier coordinate system, and further calculating a carrier system neutral surface normal vector; obtaining a moon vector under the navigation system according to the time information and the geographic position information, and calculating to obtain a normal vector vector of a neutral surface of the navigation system by using a zenith direction vector; constructing an orthogonal coordinate system by using the corresponding moon vector and the normal vector in the carrier system and the navigation system respectively; and calculating an attitude conversion matrix based on the two orthogonal coordinate systems so as to obtain a conversion relation between the carrier system and the navigation system and obtain a three-dimensional attitude angle. According to the invention, autonomous attitude determination based on the sky polarized light field under the condition of no external input is realized, an external error source is removed, and autonomy is improved.

Description

Technical Field

[0001] The invention belongs to the field of attitude determination and relates to a three-dimensional attitude determination method for a carrier based on double-vector characteristics of a nighttime polarized light field. Background Art

[0002] Bionic polarization navigation has the characteristics of passive autonomy and no error accumulation, and has been rapidly developed. As far as current research is concerned, the research on polarization navigation mainly focuses on the polarization of sunlight during the day, and the research on moonlight polarization navigation for nighttime environments is limited. Polarization navigation provides a feasible solution for autonomous navigation at night, especially when satellite navigation signals are limited.

[0003] However, the existing nighttime polarization attitude determination algorithm requires known horizontal attitude information and requires external sensors such as inertial navigation and horizon to provide horizontal attitude references. Therefore, the scope of application is limited to providing heading information for the carrier, and it will introduce external navigation information errors. For example, in Chinese patent ZL201911250896.8 (autonomous heading and attitude determination method based on polarization-astronomical angle information observation), the star sensor provides roll and pitch angle measurement information to solve the three-dimensional attitude of the carrier, but this also introduces errors in the star sensor.

[0004] At the same time, the existing methods for realizing three-dimensional attitude estimation based on polarization information do not take into account factors such as low illumination intensity and poor visibility in night scenes. Chinese patent ZL201310731899.X (Three-dimensional attitude determination method using atmospheric polarized light) can realize three-dimensional attitude determination of aircraft based on the atmospheric polarization distribution pattern, but this method needs to match the polarization information in the horizontal direction and is not suitable for application scenarios with low altitude. Chinese patent ZL201611078923.4 (A large-air polarization three-dimensional attitude determination method based on dual neutral point vectors) relies on the two neutral point vectors obtained from the carrier system and the navigation system to measure and estimate the carrier attitude, but it is difficult to observe the two neutral points at the same time in night scenes, and its applicability is limited. Chinese patent ZL202210828890.X (Three-dimensional attitude determination method based on underwater downlink radiation intensity and polarized light field) can realize the determination of the three-dimensional attitude of underwater carriers, but because it requires the optical refraction characteristics of the atmosphere-water body, this method is not suitable for atmospheric environments. Summary of the invention

[0005] In order to solve the problem that polarization navigation in night scenes requires other sensors to provide horizontal attitude information, and considering that the existing methods for realizing three-dimensional attitude estimation based on polarization information do not take into account the characteristics of night scenes, the present invention proposes a carrier three-dimensional attitude determination method based on the dual-vector characteristics of the night polarization light field, analyzes the main characteristics of the polarization distribution pattern of moonlight at night, and obtains the coordinate conversion relationship between the carrier system and the navigation system based on the measurement of the moon vector and the neutral point vector in the night polarization light field, and solves the three-dimensional attitude angle information. The present invention can provide the three-dimensional attitude estimation result of the carrier by measuring the moon vector and the neutral point vector in the polarization light field of the sky at night, and provide a type of solution for polarization autonomous attitude determination in night scenes that does not rely on external horizontal reference information. The present invention can realize the three-dimensional attitude estimation of the carrier using only polarization navigation information without introducing errors from other sensors, thereby improving the autonomy and accuracy of polarization navigation at night.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A method for three-dimensional attitude determination of a carrier based on double-vector characteristics of polarized light field at night, comprising the following steps:

[0008] The first step is to use an image polarization sensor to obtain the polarized light field of the sky, and obtain the image plane coordinate system based on the neutral point characteristics in the atmospheric polarization distribution pattern. Coordinates of the neutral point in the system ;

[0009] The second step is to calculate the carrier system according to the camera imaging model and the polarization distribution pattern information in the image plane coordinate system. The coordinates of the neutral point in the system Coordinates with the moon , get the neutral point vector and moon vector , further solve Normal vector of the neutral plane where the moon is located ;

[0010] The third step is to import the time information and geographic location information into the astronomical calendar to obtain the navigation system Moon vector , based on the zenith direction vector ,get Normal vector of the neutral surface of the line connecting the zenith point and the moon ;

[0011] Step 4: Under the load system, based on the moon vector and the midplane normal vector Construct an orthogonal coordinate system. Similarly, construct a moon vector based on the navigation system. and the midplane normal vector Construct an orthogonal coordinate system;

[0012] Step 5: Based on Department and The two orthogonal coordinate systems under the system are used to obtain the coordinate transformation relationship between the carrier system and the navigation system, and the three-dimensional attitude information is solved.

[0013] Compared with the existing technology, the present invention has the following beneficial effects:

[0014] (1) The present invention only provides three-dimensional attitude information based on the image-based polarization sensor, and the nighttime polarization navigation technology is no longer limited to heading estimation.

[0015] (2) The present invention takes into account the situation that the moon pattern cannot be directly observed in actual application scenarios, and obtains moon information based on global polarization light field information, thereby improving the environmental adaptability of three-dimensional attitude determination using polarization light fields.

[0016] (3) The present invention only uses polarized light navigation technology to solve three-dimensional spatial information, avoiding the introduction of external sensor errors and reducing the impact that external errors may bring. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of a method for three-dimensional attitude determination of a carrier based on dual-vector characteristics of a nighttime polarized light field.

[0018] Figure 2 It is a schematic diagram of the image plane coordinate system involved in the present invention.

[0019] Figure 3 Schematic diagram of the carrier system involved in the present invention.

[0020] Figure 4 It is a schematic diagram of the navigation coordinate system and polarized light field involved in the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] like Figure 1 As shown, a three-dimensional attitude determination method of a carrier based on double-vector features of a nighttime polarized light field according to an embodiment of the present invention comprises the following steps:

[0023] The first step, such as Figure 2As shown in the figure, an image polarization sensor is used to collect the polarized light field of the sky, obtain a polarization image, and solve the polarization angle (AOP) information. Draw the edge contour lines of different polarization angle areas in the polarization angle image, and obtain the image plane coordinate system based on the characteristic that the contour lines of each polarization angle of the polarized light field intersect at the neutral point. Coordinates of the neutral point in the system .

[0024] When the entire moon pattern is visible in the polarization image, the image plane coordinate system is obtained by extracting the centroid. Coordinates of the Moon in the system .

[0025] The second step is to calculate the conversion relationship between the image plane coordinate system and the carrier coordinate system based on the camera model, including: using the calibrated camera model, according to the coordinates of each group of pixels in the image plane coordinate system, calculate the azimuth and zenith angle of the detection point corresponding to the group of pixels in the carrier coordinate system, so as to obtain the azimuth and zenith angle of the detection point in the carrier coordinate system. Based on the coordinates of the neutral point , obtained by solving the camera model Neutral point coordinates . Based on the camera model The coordinate solution process under the system is as follows:

[0026] First, calculate the coordinates of the neutral point of the image plane coordinate system and the image center coordinates obtained by calibrating the camera model The relative position relationship between , considering that the coordinate axis directions of the image plane coordinate system and the carrier coordinate system are different:

[0027] .

[0028] Next, calculate The coordinates of the neutral point are:

[0029] ;

[0030] ;

[0031] .

[0032] in, is the focal length of the camera lens used.

[0033] If we can get Coordinates of the Moon , then the camera model can be used to calculate The moon coordinates in the system .

[0034] like Figure 3 As shown in , if the moon pattern in the polarized image is incomplete or invisible, the perpendicular relationship between the polarized E vector and the moon vector can be used to achieve it. For the polarized image, the AOP corresponding to each group of pixels is , the polarization E vector obtained by solution satisfy ,in, , is the moon vector obtained by connecting the moon and the origin, and the superscript T represents the transpose of the matrix. Based on the effective polarization E vector information and its perpendicular relationship with the moon vector, we can get Tie down the moon vector .

[0035] Neutral point of the system With Moon Position They are all located on the neutral plane of the sky polarized light field and can be determined based on the moon vector and the neutral point vector. Neutral plane ,in , represents the cross product of vectors. Further, based on You can get its normal vector .

[0036] Step 3: Carrier Coordinate System Zenith direction vector under the system and moon vector Determine the neutral plane normal vector in the carrier coordinate system, including:

[0037] like Figure 4 As shown, the time information and longitude and latitude information are input into the astronomical calendar to obtain the moon vector in the navigation system n. . The zenith point of the system is directly above the carrier, with coordinates , we can get the zenith direction vector . The moon and the zenith point are located on the moon-antimoon meridian, which is included in the neutral plane of the polarized light field. and It can be determined Neutral plane . Further, the corresponding normal vector can be obtained .

[0038] Step 4: Use the moon vector and the neutral surface normal as anchor vectors to construct orthogonal coordinate systems in the carrier system and navigation system, including:

[0039] According to the definitions of the moon vector and the neutral plane normal vector, these two vectors must be non-parallel, and can therefore be used as the basic vectors for constructing an orthogonal coordinate system.

[0040] exist Based on the moon vector and the normal vector The orthogonal matrix can be constructed as follows:

[0041] ;

[0042] in, and Represent two vectors used to construct an orthogonal matrix, , and are three mutually perpendicular unit vectors obtained by calculation and point to one direction of the coordinate axis respectively.

[0043] Similarly, in The system can be based on the moon vector and the normal vector Construct the following orthogonal matrix:

[0044] ;

[0045] in, and Represent two vectors used to construct an orthogonal matrix, , and are three mutually perpendicular unit vectors obtained by calculation and point to one direction of the coordinate axis respectively.

[0046] The coordinate transformation relationship matrix A can be obtained:

[0047] ;

[0048] in, and is the anchor vector, and To calculate the vector, select and The coordinate transformation relationship matrix calculated as the anchor vector is: Similarly, select and The coordinate transformation relationship matrix calculated as the anchor vector is: .

[0049] Step 5: Select the standard deviation (SD) of the anchor vector as the coordinate transformation matrix. and The accuracy measure is used to establish the weight coefficient. The attitude matrix obtained by using the moon vector as the anchor vector SD corresponding to the moon vector measurement , similarly, using the normal vector as the pose matrix of the anchor vector SD corresponding to normal vector measurement .

[0050] Based on SD as the accuracy weight, the attitude transformation matrix can be obtained The linear unbiased minimum variance estimate of for:

[0051] ;

[0052] Using the unknown SD with error and Instead of exact and , we can get:

[0053] ;

[0054] The weights of the two attitude transformation matrices are obtained by SD, and the weights are defined as , They are:

[0055] ;

[0056] That is .

[0057] definition for The variance of is:

[0058] ;

[0059] From the above formula, we can see that the smallest You can select weights When obtained.

[0060] Based on and The posture transformation matrix with the minimum variance is obtained as:

[0061] ;

[0062] in, To be superior to and The pose transformation matrix estimation result.

[0063] Based on the attitude transformation matrix, the three-dimensional attitude information of the carrier - pitch angle, roll angle and heading angle - can be calculated.

[0064] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

[0065] The above description is only a specific implementation mode of the present invention, so that those skilled in the art can understand the present invention, but the protection scope of the present invention is not limited thereto, and any other changes or substitutions that can be easily thought of by those skilled in the art should be included in the protection scope of the present invention.

Claims

1. A three-dimensional attitude determination method for a carrier based on the dual-vector characteristics of polarized light field at night, characterized in that: The steps include: The first step is to use an image polarization sensor to obtain the polarized light field of the sky, and obtain the image plane coordinate system based on the neutral point characteristics in the atmospheric polarization distribution pattern. Coordinates of the neutral point in the system ; The second step is to calculate the carrier system according to the camera imaging model and the polarization distribution pattern information in the image plane coordinate system. The coordinates of the neutral point in the system Coordinates with the moon , get the neutral point vector and moon vector , further solve Normal vector of the neutral plane where the moon is located ; The third step is to import the time information and geographic location information into the astronomical calendar to obtain the navigation system Moon vector , based on the zenith direction vector ,get Normal vector of the neutral surface of the line connecting the zenith point and the moon ; Step 4: Under the load system, based on the moon vector and the midplane normal vector Construct an orthogonal coordinate system. Similarly, construct a moon vector based on the navigation system. and the midplane normal vector Construct an orthogonal coordinate system; Step 5: Based on Department and The two orthogonal coordinate systems under the system are used to obtain the coordinate transformation relationship between the carrier system and the navigation system, and the three-dimensional attitude information is solved.

2. According to claim 1, a method for determining the three-dimensional attitude of a carrier based on the double-vector characteristics of polarized light field at night, characterized in that: The first step comprises: Use an image polarization sensor to collect the polarized light field of the sky to obtain a polarization image, calculate the polarization angle information, draw the edge contour lines of different polarization angle areas in the polarization angle image, and obtain the image plane coordinate system based on the characteristic that the contour lines of each polarization angle of the polarized light field intersect at the neutral point. Coordinates of the neutral point in the system ; When the entire moon pattern is visible in the polarization image, the image plane coordinate system is obtained by extracting the centroid. Coordinates of the Moon in the system .

3. According to claim 1, a method for determining the three-dimensional attitude of a carrier based on the double-vector characteristics of the nighttime polarized light field is characterized in that: The second step includes: Using the calibrated camera model, according to the coordinates of each group of pixels in the image plane coordinate system, the azimuth and zenith angle of the detection point corresponding to the group of pixels in the carrier coordinate system are calculated, so as to obtain the position of the point in the carrier coordinate system. Coordinates of the system; based on the neutral point coordinates , obtained by solving the camera model Neutral point coordinates ; Camera model based The coordinate solution process under the system is as follows: First, calculate the coordinates of the neutral point of the image plane coordinate system and the image center coordinates obtained by calibrating the camera model The relative position relationship between , considering that the coordinate axes of the image plane coordinate system and the carrier coordinate system are in different directions: ； Next, calculate The coordinates of the neutral point are: ； ； ； in, is the focal length of the camera lens used.

4. The method for three-dimensional attitude determination of a carrier based on double-vector characteristics of polarized light field at night according to claim 3 is characterized in that: If in the first step Moon coordinates , then the camera model is used to calculate Set the moon coordinates ; When the moon pattern in the polarized image is incomplete or invisible, the perpendicular relationship between the polarized E vector and the moon vector is used to achieve this; For polarized images, the polarization angle corresponding to each group of pixels is , the polarization E vector obtained by solution satisfy ,in, , The moon vector is obtained by connecting the moon and the origin. Based on the effective polarization E vector information and its perpendicular relationship with the moon vector, it is solved to get Tie down the moon vector ; Neutral point With Moon Position They are all located on the neutral plane of the sky polarized light field, determined based on the moon vector and the neutral point vector Neutral plane ,in ; based on Get its normal vector .

5. The method for three-dimensional attitude determination of a carrier based on double-vector characteristics of polarized light field at night according to claim 1 is characterized in that: The third step comprises: Input the time information and longitude and latitude information into the astronomical calendar to obtain the moon vector in the navigation system n ; The zenith point of the system is directly above the carrier, with coordinates , that is, to obtain the zenith direction vector ; The moon and the zenith point are located on the moon-antimoon meridian, and the moon-antimoon meridian is located on the neutral plane of the polarized light field. and Sure Neutral plane , thus obtaining the corresponding normal vector .

6. The method for three-dimensional attitude determination of a carrier based on double-vector characteristics of polarized light field at night according to claim 1 is characterized in that: The fourth step comprises: exist Based on the moon vector and the normal vector Construct the following orthogonal matrix: ； in, and Represent two vectors used to construct an orthogonal matrix, , and are three mutually perpendicular unit vectors obtained by calculation and each points to a direction of the coordinate axis; exist Based on the moon vector and the normal vector Construct the following orthogonal matrix: ； in, and Represent two vectors used to construct an orthogonal matrix, , and are three mutually perpendicular unit vectors obtained by calculation and each points to a direction of the coordinate axis; Thus, the coordinate transformation relationship matrix A is obtained: ； in, and is the anchor vector, and To calculate the vector; select and The coordinate transformation relationship matrix calculated as the anchor vector is: ;choose and The coordinate transformation relationship matrix calculated as the anchor vector is: .

7. The method for three-dimensional attitude determination of a carrier based on double-vector characteristics of polarized light field at night according to claim 1 is characterized in that: The fifth step comprises: Select the error standard deviation corresponding to the anchor vector as the coordinate transformation relationship matrix obtained by solving it and Accuracy measure, establish weight coefficient; use the moon vector as the anchor vector to get the attitude matrix Corresponding to the standard deviation of the error of the moon vector measurement , using the normal vector as the pose matrix of the anchor vector Corresponding to the standard deviation of the normal vector measurement error .

8. The method for three-dimensional attitude determination of a carrier based on double-vector characteristics of polarized light field at night according to claim 7, characterized in that: Get the attitude transformation matrix based on the error standard deviation as the accuracy weight The linear unbiased minimum variance estimate of is: ； Use the unknown error standard deviation with error and Instead of exact and ,get: ； The weights of the two attitude transformation matrices are obtained by the error standard deviation, and the weights are defined as: ； That is ; definition for The variance of is: ； From the above formula, we can get the minimum In the selection weight When you get; Based on and The posture transformation matrix with the minimum variance is obtained as: ； in, To be superior to and The pose transformation matrix estimation result; Based on the attitude conversion matrix, the three-dimensional attitude information of the carrier is calculated, and the three-dimensional attitude information includes the pitch angle, roll angle and heading angle.

Images