Space autonomous positioning and navigation method and system for medium and low orbit aircraft

Abstract

The invention relates to a celestial navigation method and a celestial navigation system, in particular to a spatial autonomous positioning and navigation method and a spatial autonomous positioning and navigation system for a medium-and-low-orbit aircraft, which are used for overcoming the defect that the spatial coordinate positioning task of the medium-and-low-orbit aircraft is difficult to independently complete by celestial navigation due to the limitation of the current celestial navigation technology on accurate spatial positioning. According to the space self-positioning navigation method for the medium and low orbit aircraft, a star sensor and a photogrammetry camera work cooperatively, an attitude rotation matrix is calculated by obtaining time information and a space attitude angle during navigation positioning of the aircraft, and the attitude rotation matrix is calculated by combining image point centroid pixel coordinates extracted by imaging of a high orbit satellite and orbit information of the high orbit satellite. And establishing a linear equation set by using a collinear relation of object points and image points, and finally solving the space coordinates of the medium and low orbit aircraft in the geocentric inertial coordinate system to realize autonomous space positioning navigation.

Description

Technical Field

[0001] The present invention relates to a celestial navigation method and system, and in particular to a space autonomous positioning and navigation method and system for medium and low orbit aircraft. Background Art

[0002] With the rapid growth of global demand for space exploration and satellite applications, the navigation technology of aircraft is facing increasing challenges. The navigation of medium and low orbit aircraft usually relies on radio navigation and satellite navigation (such as GPS and BeiDou, etc.), and also uses astronomical navigation as a supplement. However, as the number of space missions continues to increase, the limited ground station resources are facing excessive pressure, and maintaining the operation of these ground stations requires a lot of manpower and material resources. In special periods, such as natural disasters or communication obstructions, traditional ground-based radio navigation and space-based navigation methods may be restricted, thus affecting the positioning accuracy and safety of medium and low orbit aircraft.

[0003] In contrast, celestial navigation, due to its autonomous characteristics, has become an important means for medium and low orbit aircraft to achieve autonomous navigation. Celestial navigation can help medium and low orbit aircraft to achieve autonomous operation and management in orbit, reducing dependence on ground stations. However, current celestial navigation technology is mainly used for attitude measurement of medium and low orbit aircraft, and has limitations for precise spatial positioning, which makes it difficult for celestial navigation to independently complete the spatial coordinate positioning task of medium and low orbit aircraft. Therefore, how to organically combine celestial navigation with other navigation technologies to solve the problem of spatial positioning of medium and low orbit aircraft has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the current celestial navigation technology has limitations in accurate space positioning, making it difficult for celestial navigation to independently complete the spatial coordinate positioning task of medium and low orbit aircraft, and to provide a method and system for autonomous space positioning and navigation of medium and low orbit aircraft.

[0005] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides the following technical solutions:

[0006] A method for autonomous positioning and navigation of medium and low orbit aircraft in space, which is special in that it includes the following steps:

[0007] Step 1: Obtain the time information T0 of navigation positioning, and assume that the spatial coordinates of the medium and low orbit aircraft in the geocentric inertial coordinate system during navigation positioning are (X S , Y S , Z S );

[0008] Step 2: Use star sensors to measure the spatial attitude angle of the low- and medium-orbit aircraft in the geocentric inertial coordinate system during navigation and positioning, and then obtain the attitude rotation matrix R;

[0009] Step 3: Use a photogrammetric camera fixedly installed with the star sensor to image at least two high-orbit satellites to obtain high-orbit satellite images, and then extract the centroid pixel coordinates (x i ,y i );

[0010] Step 4: Using the time information T0 and the cataloged high-orbit satellite orbit information, calculate the spatial coordinates (X i , Y i , Z i );

[0011] Step 5: Based on the collinear relationship between object points and image points measured by photogrammetry, we can obtain:

[0012]

[0013] Where f is the focal length of the optical system of the photogrammetric camera, a is the pixel size of the imaging sensor chip in the photogrammetric camera, (c x , c y ) is the coordinate of the principal point in the photogrammetric coordinate system, λ is the scaling factor between the object and the image;

[0014] Substitute the posture rotation matrix R obtained in step 2 to obtain the spatial coordinate (X S , Y S , Z S ) of the linear equations, and then calculate the spatial coordinates (X S , Y S , Z S ) to complete the spatial coordinate positioning of medium and low orbit spacecraft.

[0015] Furthermore, the step 2 is specifically as follows:

[0016] Step 2.1, collect star images through the star sensor, extract the measured positions of the stars from the star images, and match them with the pre-stored star catalog to obtain the known positions of the stars;

[0017] Step 2.2, by comparing the known positions of stars with the measured positions, calculate the spatial attitude angle of the low- and medium-orbit spacecraft in the geocentric inertial coordinate system during navigation and positioning;

[0018] Step 2.3, according to the spatial attitude angle obtained in step 2.2, calculate the attitude rotation matrix R as follows:

[0019] R=R x(φ)·R y (θ)·R z (ψ)

[0020] In the formula, R x (φ), R y (θ), R z (ψ) represents the rotation matrix around the x-axis, y-axis, and z-axis of the medium and low orbit spacecraft respectively.

[0021] Furthermore, in step 3, the pixel coordinates (x i ,y i ) is extracted through a sub-pixel segmentation positioning algorithm.

[0022] Furthermore, the step 4 is specifically as follows:

[0023] Step 4.1, according to the cataloged high-orbit satellite orbit information, obtain the six orbital parameters of each high-orbit satellite, including the semi-major axis a, eccentricity e, inclination i0, ascending node right ascension Ω, perigee argument ω, and orbit initial mean anomaly M0;

[0024] Step 4.2: Calculate the spatial coordinates (X i , Y i , Z i ).

[0025] Furthermore, the step 4.2 is specifically as follows:

[0026] Step 4.2.1. Solve the Kepler equation by iterative method and calculate the eccentric anomaly angle E:

[0027]

[0028] M=Ee·sin(E)

[0029] Where M is the current anomaly angle of the orbit, n is the average angular velocity of the high-orbit satellite along the orbit, μ is the standard gravitational parameter of the earth, and T epoch is the epoch time;

[0030] Step 4.2.2: Use the eccentric anomaly angle E to calculate the two-dimensional coordinates (X o , Y o ):

[0031] X o =a+(cosE-e)

[0032]

[0033] Step 4.2.3: The two-dimensional coordinates (X o , Y o ) is converted to the geocentric inertial coordinate system to obtain the spatial coordinate (X i , Y i , Z i );

[0034]

[0035] In the formula, R z , R x They represent the rotation matrices around the z-axis and x-axis of the i-th high-orbit satellite respectively.

[0036] Furthermore, in step 5, the posture rotation matrix R obtained in step 2 is substituted to obtain the spatial coordinate (X S , Y S , Z S ) of the linear equations, and then calculate the spatial coordinates (X S , Y S , Z S ) Specifically:

[0037] Assume the attitude rotation matrix R is:

[0038]

[0039] Then, through deformation, we can get the spatial coordinates (X S , Y S , Z S ) is the linear equation system:

[0040]

[0041] By using the least squares method, we can get (X S , Y S , Z S ).

[0042] At the same time, the present invention also provides a medium- and low-orbit aircraft space autonomous positioning and navigation system, which is used to implement the above-mentioned medium- and low-orbit aircraft space autonomous positioning and navigation method;

[0043] The special feature of the invention is that it comprises a mounting base plate, and a star sensor and a photogrammetry camera arranged on the mounting base plate, and the optical axis of the star sensor is arranged parallel to the optical axis of the photogrammetry camera.

[0044] Furthermore, the star sensor includes a first optical lens, a first light shield, and a first imaging and data processing module; the first optical lens is used for imaging, and is located on the optical axis of the star sensor and in the first light shield;

[0045] The photogrammetric camera comprises a second optical lens, a second light shield and a second imaging and data processing module; the second optical lens is used for imaging, and is located on the optical axis of the photogrammetric camera and in the second light shield;

[0046] The first imaging and data processing module and the second imaging and data processing module are communicatively connected. The first imaging and data processing module is used to calculate the attitude rotation matrix R according to the spatial attitude angle of the medium and low orbit aircraft in the geocentric inertial coordinate system, and send the spatial attitude angle of the medium and low orbit aircraft in the geocentric inertial coordinate system to the second imaging and data processing module. The second imaging and data processing module is used to extract the centroid pixel coordinates of the corresponding image points of at least two high-orbit satellites in the high-orbit satellite image, and convert them into spatial coordinates in the geocentric inertial coordinate system, and then calculate the spatial coordinates of the medium and low orbit aircraft in the geocentric inertial coordinate system during navigation and positioning in combination with the spatial attitude angle of the medium and low orbit aircraft in the geocentric inertial coordinate system.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] (1) The present invention provides a method for autonomous spatial positioning and navigation of medium and low orbit aircraft, which utilizes a star sensor and a photogrammetry camera to work together, obtains the time information and spatial attitude angle of the aircraft during navigation and positioning, calculates the attitude rotation matrix, combines the centroid pixel coordinates of the image points extracted by high-orbit satellite imaging and the orbit information of the high-orbit satellite, and uses the collinear relationship between the object points and the image points to establish a linear equation group, and finally solves the spatial coordinates of the medium and low orbit aircraft in the geocentric inertial coordinate system to achieve autonomous spatial positioning and navigation; the present invention combines high-orbit satellite observations and the medium and low orbit aircraft's own sensor data, does not require ground auxiliary equipment, and has the characteristics of high efficiency and independence.

[0049] (2) The present invention uses star sensors for space attitude positioning, which has the characteristics of high precision (measurement accuracy better than 5"), high refresh rate (better than 10 Hz) and mature technology, and can meet the needs of rapid attitude adjustment of aircraft.

[0050] (3) The present invention uses the known three-dimensional coordinates of high-orbit satellites for positioning through photogrammetry technology. At least two high-orbit satellites are needed to achieve high-precision positioning of medium and low-orbit aircraft. The positioning accuracy is better than 50 meters, and the algorithm has good robustness.

[0051] (4) The present invention provides a space autonomous positioning and navigation system for medium and low orbit aircraft, including a star sensor and a photographic imaging camera. It has a simple design, light weight, and small size, and is suitable for aircraft application scenarios with strict requirements on payload weight and volume.

[0052] (5) The attitudes of the star sensor measurement coordinate system and the photographic imaging camera measurement coordinate system in the present invention can be flexibly designed according to installation requirements, and the attitude relationship between the two can be determined by calibration. It is suitable for a variety of environments and installation requirements and has strong adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a schematic diagram of the structure of an embodiment of a space autonomous positioning and navigation system for medium and low orbit aircrafts of the present invention;

[0054] Figure 2 Schematic diagram of the working principle of the photogrammetry camera in an embodiment of the present invention.

[0055] The reference numerals are as follows: 1. optical axis of star sensor; 2. first light shield; 3. first optical lens; 4. first imaging and data processing module; 5. optical axis of photogrammetry camera; 6. second light shield; 7. second optical lens; 8. second imaging and data processing module; 9. mounting base; 10. imaging sensor chip. DETAILED DESCRIPTION

[0056] The present invention will be further described below in conjunction with the accompanying drawings and exemplary embodiments.

[0057] Reference Figure 1 A space autonomous positioning and navigation system for medium and low orbit aircraft includes a mounting base plate 9, and a star sensor and a photogrammetric camera arranged on the mounting base plate 9; the star sensor optical axis 1 is arranged parallel to the photogrammetric camera optical axis 5, which is convenient for calibrating the three-dimensional attitude relationship between the star sensor measurement coordinate system and the photogrammetric coordinate system.

[0058] The star sensor is a star sensor, which is used to measure the spatial attitude angle of a medium and low orbit aircraft in the geocentric inertial coordinate system, and then obtain the attitude rotation matrix R; the star sensor includes a first optical lens 3, a first light shield 2, and a first imaging and data processing module 4; the first optical lens 3 is used for imaging, which is located on the optical axis 1 of the star sensor and is located in the first light shield 2; the first light shield 2 is used to reduce the influence of stray light on the attitude measurement accuracy, so as to ensure the attitude measurement accuracy.

[0059] Reference Figures 1-2 , the photogrammetric camera is used to image at least two high-orbit satellites and extract the pixel coordinates of the centroid of the corresponding image points; Figure 2 The photogrammetry camera uses a central perspective projection model to image S1 and S2 of two high-orbit satellites in space, and projects them onto the imaging sensor chip 10 to form corresponding image points S1 ′ and S2 ′ respectively.

[0060] The photogrammetric camera includes a second optical lens 7, a second light shield 6 and a second imaging and data processing module. The second optical lens 7 is used for imaging and is located on the optical axis 5 of the photogrammetric camera and in the second light shield 6. The focal length of the second optical lens 7 is determined by the flight altitude of the medium and low orbit aircraft, the flight altitude of the high orbit satellite to be detected, and the pixel size of the imaging sensor chip 10. The second light shield 6 is used to reduce the detection imaging of the high orbit satellite by stray light. The second imaging and data processing module is arranged on the mounting base plate 9, and an imaging sensor chip 10 is arranged in the second imaging and data processing module.

[0061] The first imaging and data processing module 4 and the second imaging and data processing module 8 are communicatively connected. The first imaging and data processing module 4 is used to calculate the attitude rotation matrix R according to the spatial attitude angle of the medium and low orbit aircraft in the geocentric inertial coordinate system, and send the spatial attitude angle of the medium and low orbit aircraft in the geocentric inertial coordinate system to the second imaging and data processing module 8. The second imaging and data processing module 8 is used to extract the centroid pixel coordinates of the corresponding image points of at least two high-orbit satellites in the high-orbit satellite image, and convert them into spatial coordinates in the geocentric inertial coordinate system, and then combine the spatial attitude angle of the medium and low orbit aircraft in the geocentric inertial coordinate system to calculate the spatial coordinates of the medium and low orbit aircraft in the geocentric inertial coordinate system during navigation and positioning.

[0062] A method for autonomous positioning and navigation in space for a medium- and low-orbit aircraft, using the above-mentioned autonomous positioning and navigation system for space for a medium- and low-orbit aircraft, comprises the following steps:

[0063] Step 1: Obtain the time information T0 of navigation positioning, and assume that the spatial coordinates of the medium and low orbit aircraft in the geocentric inertial coordinate system during navigation positioning are (X S , Y S , Z S );

[0064] Step 2: Use star sensors to measure the spatial attitude angle of the low- and medium-orbit aircraft in the geocentric inertial coordinate system during navigation and positioning, and then obtain the attitude rotation matrix R;

[0065] Step 2.1, collect star images through the star sensor, extract the measured positions of the stars from the star images, and match them with the pre-stored star catalog to obtain the known positions of the stars;

[0066] Step 2.2, by comparing the known positions of stars with the measured positions, calculate the spatial attitude angles (roll angle φ, pitch angle θ, yaw angle ψ) of the low- and medium-orbit spacecraft in the geocentric inertial coordinate system during navigation and positioning;

[0067] Step 2.3, according to the spatial attitude angle obtained in step 2.2, calculate the attitude rotation matrix R as follows:

[0068]

[0069] In the formula, R x (φ), R y (θ), R z (ψ) represents the rotation matrix around the x-axis, y-axis, and z-axis of the medium and low orbit spacecraft respectively;

[0070] Step 3: Use a photogrammetric camera to image at least two high-orbit satellites to obtain high-orbit satellite images. The pixel coordinates of the centroid of the corresponding image point of the i-th high-orbit satellite in the high-orbit satellite image are (x i ,y i ), and then extract the pixel coordinates of the centroid of the pixel point (x i ,y i );

[0071] Step 4: Using the time information T0 and the cataloged high-orbit satellite orbit information, calculate the spatial coordinates (X i , Y i , Z i );

[0072] Step 4.1, according to the cataloged high-orbit satellite orbit information, obtain the six orbital parameters of each high-orbit satellite, including the semi-major axis a, eccentricity e, inclination i0, ascending node right ascension Ω, perigee argument ω, and orbit initial mean anomaly M0;

[0073] Step 4.2: Calculate the spatial coordinates (X i , Y i , Z i );

[0074] Step 4.2.1. Solve the Kepler equation by iterative method and calculate the eccentric anomaly angle E:

[0075]

[0076] M=Ee·sin(E)

[0077] Where M is the current anomaly angle of the orbit, n is the average angular velocity of the high-orbit satellite along the orbit, μ is the standard gravitational parameter of the earth, and T epoch is the epoch time;

[0078] Step 4.2.2: Use the eccentric anomaly angle E to calculate the two-dimensional coordinates (X o , Y o ):

[0079] X o=a+(cos Ee)

[0080]

[0081] Step 4.2.3: The two-dimensional coordinates (X o , Y o ) is converted to the geocentric inertial coordinate system to obtain the spatial coordinate (X i , Y i , Z i );

[0082]

[0083] In the formula, R z , R x Respectively represent the rotation matrices around the z-axis and x-axis of the i-th high-orbit satellite;

[0084] Step 5: Since the star sensor is fixedly mounted with the photogrammetric camera, the spatial attitude of the medium and low orbit aircraft obtained by the star sensor is the attitude of the photogrammetric camera itself;

[0085] Assume that the focal length of the optical system of the photogrammetric camera is f, the pixel size of the imaging sensor chip 10 is a, and the coordinates of the principal point in the photogrammetric coordinate system are (c x , c y ), according to the collinear relationship between object points and image points in photogrammetry, we can get:

[0086]

[0087] In the above formula, the focal length of the optical system is f, the pixel size is a, and the principal point (c x , c y ) is the internal parameter of the photogrammetric camera, which is a known quantity; the spatial coordinates of the i-th high-orbit satellite (X i , Y i , Z i ), the attitude rotation matrix R of the medium and low orbit aircraft is a known quantity; the photography center is the coordinate of the medium and low orbit aircraft in the space coordinate system (X S , Y S , Z S ) is the object to be solved, λ is the scaling factor between the object and the image;

[0088] Assume the attitude rotation matrix R is:

[0089]

[0090] Then, through deformation, we can get the spatial coordinate (X S , Y S , Z S ) is the linear equation system:

[0091]

[0092] When there are two or more high-orbit satellites as cooperative targets for simultaneous imaging, this system of equations is an overdetermined system of equations and can be solved by the least squares method to obtain (X S , Y S , Z S ) to complete the spatial coordinate positioning of medium and low orbit spacecraft.

Claims

1. A method for autonomous positioning and navigation of medium and low orbit aircraft in space, characterized in that: The following steps are involved: Step 1: Obtain the time information T0 of navigation positioning, and assume that the spatial coordinates of the medium and low orbit aircraft in the geocentric inertial coordinate system during navigation positioning are (X S , Y S , Z S ); Step 2: Use star sensors to measure the spatial attitude angle of the low- and medium-orbit aircraft in the geocentric inertial coordinate system during navigation and positioning, and then obtain the attitude rotation matrix R; Step 3: Use a photogrammetric camera fixedly installed with the star sensor to image at least two high-orbit satellites to obtain high-orbit satellite images, and then extract the centroid pixel coordinates (x i ,y i ); Step 4: Using the time information T0 and the cataloged high-orbit satellite orbit information, calculate the spatial coordinates (X i , Y i , Z i ); Step 5: Based on the collinear relationship between object points and image points measured by photogrammetry, we can obtain: Wherein, f is the focal length of the optical system of the photogrammetric camera, a is the pixel size of the imaging sensor chip (10) in the photogrammetric camera, (c x , c y ) is the coordinate of the principal point in the photogrammetric coordinate system, λ is the scaling factor between the object and the image; Substitute the posture rotation matrix R obtained in step 2 to obtain the spatial coordinate (X S , Y S , Z S ) of the linear equations, and then calculate the spatial coordinates (X S , Y S , Z S ) to complete the spatial coordinate positioning of medium and low orbit spacecraft.

2. The method for autonomous positioning and navigation of a medium- and low-orbit aircraft in space according to claim 1, characterized in that: The step 2 is specifically as follows: Step 2.1, collect star images through the star sensor, extract the measured positions of the stars from the star images, and match them with the pre-stored star catalog to obtain the known positions of the stars; Step 2.2, by comparing the known positions of stars with the measured positions, calculate the spatial attitude angle of the low- and medium-orbit spacecraft in the geocentric inertial coordinate system during navigation and positioning; Step 2.3, according to the spatial attitude angle obtained in step 2.2, calculate the attitude rotation matrix R as follows: R=R x (φ)·R y (θ)·R z (ψ) In the formula, R x (φ), R y (θ), R z (ψ) represents the rotation matrix around the x-axis, y-axis, and z-axis of the medium and low orbit spacecraft respectively.

3. The method for autonomous positioning and navigation of a medium- and low-orbit aircraft in space according to claim 1, characterized in that: In step 3, the pixel coordinates (x i ,y i ) is extracted through a sub-pixel segmentation positioning algorithm.

4. A method for autonomous positioning and navigation of a medium- and low-orbit aircraft in space according to any one of claims 1 to 3, characterized in that: The step 4 is specifically as follows: Step 4.1, according to the cataloged high-orbit satellite orbit information, obtain the six orbital parameters of each high-orbit satellite, including the semi-major axis a, eccentricity e, inclination i0, ascending node right ascension Ω, perigee argument ω, and orbit initial mean anomaly M0; Step 4.2: Calculate the spatial coordinates (X i , Y i , Z i ).

5. The method for autonomous positioning and navigation of medium and low orbit aircraft in space according to claim 4, characterized in that: The step 4.2 is as follows: Step 4.2.

1. Solve the Kepler equation by iterative method and calculate the eccentric anomaly angle E: M=Ee·sin(E) Where M is the current anomaly angle of the orbit, n is the average angular velocity of the high-orbit satellite along the orbit, μ is the standard gravitational parameter of the earth, and T epoch is the epoch time; Step 4.2.2: Use the eccentric anomaly angle E to calculate the two-dimensional coordinates (X o , Y o ): X o =a+(cosE-e) Step 4.2.3: The two-dimensional coordinates (X o , Y o ) is converted to the geocentric inertial coordinate system to obtain the spatial coordinate (X i , Y i , Z i ); In the formula, R z , R x They represent the rotation matrices around the z-axis and x-axis of the i-th high-orbit satellite respectively.

6. The method for autonomous positioning and navigation of medium and low orbit aircraft in space according to claim 5, characterized in that: In step 5, the posture rotation matrix R obtained in step 2 is substituted to obtain the spatial coordinate (X S , Y S , Z S ) of the linear equations, and then calculate the spatial coordinates (X S , Y S , Z S ) specifically: Assume the attitude rotation matrix R is: Then, through deformation, we can get the spatial coordinates (X S , Y S , Z S ) is the linear equation system: By using the least squares method, we can get (X S , Y S , Z S ).

7. A low-orbit aircraft space autonomous positioning and navigation system, used to implement the low-orbit aircraft space autonomous positioning and navigation method according to claim 1; Features: It comprises a mounting base plate (9), and a star sensor and a photogrammetry camera arranged on the mounting base plate (9); the optical axis (1) of the star sensor is arranged parallel to the optical axis (5) of the photogrammetry camera.

8. The space autonomous positioning and navigation system for medium and low orbit aircraft according to claim 7, characterized in that: The star sensor comprises a first optical lens (3), a first light shield (2), and a first imaging and data processing module (4); the first optical lens (3) is used for imaging and is located on the optical axis (1) of the star sensor and inside the first light shield (2); The photogrammetric camera comprises a second optical lens (7), a second light shield (6) and a second imaging and data processing module (8); the second optical lens (7) is used for imaging and is located on the optical axis (5) of the photogrammetric camera and inside the second light shield (6); The first imaging and data processing module (4) and the second imaging and data processing module (8) are communicatively connected. The first imaging and data processing module (4) is used to calculate the attitude rotation matrix R according to the spatial attitude angle of the medium and low orbit aircraft in the geocentric inertial coordinate system, and send the spatial attitude angle of the medium and low orbit aircraft in the geocentric inertial coordinate system to the second imaging and data processing module (8). The second imaging and data processing module (8) is used to extract the centroid pixel coordinates of the corresponding image points of at least two high orbit satellites in the high orbit satellite image, and convert them into spatial coordinates in the geocentric inertial coordinate system, and then calculate the spatial coordinates of the medium and low orbit aircraft in the geocentric inertial coordinate system during navigation and positioning in combination with the spatial attitude angle of the medium and low orbit aircraft in the geocentric inertial coordinate system.

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