A remote sensing satellite sky-pointing attitude control method and computer readable medium

Abstract

The application provides a remote sensing satellite sky pointing attitude control method and a computer readable medium. The application obtains star / ground camera configuration and prior information, obtains a sun / earth shadow angle and an installation matrix of the star / ground camera, obtains a satellite pointing earth center and sun direction vector according to a current time and orbit information, calculates an expected attitude quaternion of a satellite body system relative to an inertial system when the satellite points to the sky, and realizes attitude convergence when the satellite points to the sky; combined with on-orbit calibration requirements and constraints, a push-broom angle velocity, a push-broom angle direction and a push-broom time length are obtained, a rotating Euler axis is determined, an expected attitude quaternion and an angle velocity of the satellite when the satellite pushes and scans to the sky are obtained, and the satellite performs sky pushing and scanning. The application can avoid the influence of sunlight and earth reflection stray light on simultaneous imaging of the star / ground camera, is more suitable for processing of remote sensing images after push-broom imaging of the linear array ground camera, and meets the on-orbit calibration requirement of the star / ground camera included angle of the remote sensing satellite.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of remote sensing satellite control system, and particularly relates to a remote sensing satellite sky pointing attitude control method and a computer readable medium. BACKGROUND

[0002] For high-precision remote sensing satellites, geometric positioning and processing gradually break away from the dependence on a large number of ground control points, and develop towards sparse ground control or no ground control. The geometric positioning accuracy depends not only on the ground data processing level, but also on the satellite attitude determination accuracy, and the satellite attitude determination accuracy is the key to ensuring the geometric quality of the image.

[0003] During the satellite on-orbit flight stage, due to the changes of the attitude and the orbit, the sunning condition of the satellite also changes, and the change of the space thermal environment will cause a small angular displacement of the satellite / ground camera included angle, which introduces a low-frequency error term into the attitude determination, and it is difficult to eliminate by the ground calibration. In CN2021112828925, a kind of agile optical remote sensing satellite star / ground camera included angle on-orbit calibration method based on star observation is disclosed, the direction of the star / ground camera in the inertial coordinate system is determined by obtaining the pictures of the star / ground camera imaging on the star, and then the included angle between the two is obtained. When performing geometric calibration, since the ground camera is a linear array camera, the attitude of the satellite needs to be controlled for sky pointing and push scanning, the star / ground camera needs to be simultaneously aligned with the star imaging, and the influence of the sun light and the stray light reflected by the earth needs to be avoided, but CN2021112828925 does not provide a solution for the satellite sky pointing and push scanning attitude control.

[0004] In view of the above problems, under the complex constraint conditions of the star / ground camera sun / earth shielding angle multivariable, according to the geometric relationship of star-ground-sun and the installation angle of the star / ground camera, a remote sensing satellite sky pointing and push scanning attitude control strategy and algorithm is designed, which is an indispensable link for realizing the on-orbit calibration of the remote sensing satellite star / ground camera included angle, and has important research value. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a remote sensing satellite sky pointing attitude control method and a computer readable medium.

[0006] The technical scheme of the method of the present application is a remote sensing satellite sky pointing attitude control method, which comprises the following steps:

[0007] Step 1: Obtain the star / ground camera configuration and prior information to obtain the sun shielding angle of the star camera, the earth shielding angle of the star camera, the sun shielding angle of the ground camera, and the earth shielding angle of the ground camera. According to the current time and the orbit information, the direction vector of the satellite pointing to the earth center and the direction vector of the satellite pointing to the sun are obtained, and the installation matrix of the ground camera, the installation matrix of the star camera A, and the installation matrix of the star camera B are obtained.

[0008] Step 2: calculate the expected attitude quaternion of the satellite body frame relative to the inertial frame when the satellite points to the sky, and realize the attitude convergence when the satellite points to the sky;

[0009] Step 3: obtain the push-scan angular velocity, push-scan angular direction and push-scan time length, and determine the rotation Euler axis, solve the expected attitude quaternion of the satellite body frame relative to the inertial frame when the satellite points to the sky, and the expected attitude angular velocity of the satellite body frame relative to the inertial frame after the satellite pointing to the sky attitude converges, and the satellite performs sky pointing according to the push-scan angular velocity and time length;

[0010] Preferably, the day occultation angle of the star camera in step 1 is defined as λ st_sun ;

[0011] The day occultation angle of the star camera in step 1 is defined as λ st_earth ;

[0012] The day occultation angle of the star camera in step 1 is defined as λ cam_sun ;

[0013] The day occultation angle of the star camera in step 1 is defined as λ cam_earth ;

[0014] The direction vector of the satellite pointing to the center of the earth in step 1 is defined as r e ;

[0015] The direction vector of the satellite pointing to the sun in step 1 is defined as r s ;

[0016] The ground camera of the satellite in step 1 is configured as a ground camera;

[0017] The star camera of the satellite in step 1 is configured as star camera A and star camera B;

[0018] The installation azimuth information of the ground camera in step 1 is that the optical axis is not strictly directed to the+z b axis direction of the satellite body coordinate system ;

[0019] The installation azimuth information of the star camera in step 1 is that the star camera A and the star camera B are not strictly mirror symmetric about the Oy b z b plane of the satellite body coordinate system , and the optical axes are all deviated to the+y b direction;

[0020] The installation matrix of the ground camera in step 1 is defined as M B2Cam ;

[0021] The installation matrix of the star camera A in step 1 is defined as MB2STA ;

[0022] The installation matrix of the star camera B mentioned in step 1 is defined as: M B2STB ;

[0023] As a preferred embodiment, the calculation of the expected attitude quaternion of the satellite's own system relative to the inertial frame when the satellite is pointing towards the sky in step 2 is as follows:

[0024] Step 2.1: Obtain the optical axis of the ground camera in the satellite body coordinate system through satellite accuracy testing. coordinates r Cam The optical axis of the star camera A is in the satellite's body coordinate system coordinates r STA The optical axis of the satellite camera B is in the satellite's body coordinate system. coordinates r STB The optical axis of the star camera A is in the satellite's body coordinate system Oy b z b Projected vector r on the plane projSTA The optical axis of the satellite camera B is in the satellite's body coordinate system. Oy b z b Projected vector r on the plane projSTB The optical axes of Star Camera A and Star Camera B are in the satellite's body coordinate system. Oy b z b The direction vector r of the projection vectors on the plane projSTAB ,but:

[0025] r projSTAB =(r projSTA +r projSTB ) / ||r projSTA +r projSTB ||

[0026] Where |||| denotes the second norm of the vector;

[0027] Step 2.2: Consider maximizing the direction vector r between the optical axis and the satellite pointing towards the Earth's center. e The direction vector r of the satellite pointing towards the sun s The angle between the two points causes the satellite's attitude to point towards the sky, r projSTAB With r Cam and r e Coplanar, r projSTAB r Cam The plane formed and r e and r s The planes formed are perpendicular, and r projSTAB r Cam Regarding r e and r sThe plane formed is mirror symmetric, r projSTAB r Cam The included angle is:

[0028] θ = arccos(r) projSTAB ·r Cam )

[0029] Where arccos represents the inverse cosine, and θ represents the optical axes of star camera A and star camera B in the satellite body coordinate system. Oy b z b The direction vector of the projection vector sum on the plane and the optical axis of the ground camera in the satellite body coordinate system The angle between the coordinates;

[0030] r Cam With r e The included angle is 180° - θ / 2, r projSTAB With r e The included angle is 180° - θ / 2;

[0031] r Cam With r s The included angle is greater than θ / 2, r projSTAB With r s The included angle is greater than θ / 2;

[0032] Step 2.3: r s and r e The direction vector of the plane normal is: |||| denotes the 2-norm of a vector;

[0033] r Cam In n se The upper projection is positive, r projSTAB In n se A negative upward projection is defined as a positive projection.

[0034] In the case of forward projection, r Cam The direction vector in the inertial frame can be expressed as:

[0035]

[0036] r Cam In n se The upward projection is negative, r projSTAB In n se A positive upward projection is defined as the case of a negative projection.

[0037] In the case of negative projection, r Cam The direction vector in the inertial frame can be expressed as:

[0038]

[0039] The X-axis coordinate axis direction vector, the Y-axis coordinate axis direction vector, and the Z-axis coordinate axis direction vector of the satellite body coordinate system in the forward projection case are projected in the inertial system as follows:

[0040]

[0041]

[0042]

[0043] The rotation matrix of the inertial system to the satellite body system in the forward projection case is as follows:

[0044] Let the expected attitude quaternion of the satellite when the satellite points to the sky in the forward projection case be q

[0045] According to the relationship between the rotation matrix and the quaternion, the expected attitude quaternion of the satellite body system relative to the inertial system when the satellite points to the sky in the forward projection case can be obtained as follows:

[0046] According to the algebraic correspondence relationship, the expected attitude quaternion of the satellite body system relative to the inertial system when the satellite points to the sky in the forward projection case can be obtained as follows:

[0047]

[0048] The X-axis coordinate axis direction vector, the Y-axis coordinate axis direction vector, and the Z-axis coordinate axis direction vector of the satellite body coordinate system in the backward projection case are projected in the inertial system as follows:

[0049]

[0050]

[0051] The rotation matrix of the inertial system to the satellite body system in the backward projection case is as follows:

[0052] According to the relationship between the rotation matrix and the quaternion in the forward projection case and the algebraic correspondence relationship, the expected attitude quaternion of the satellite body system relative to the inertial system when the satellite points to the sky in the backward projection case can be obtained as follows:

[0053] According to the current satellite attitude q i2b The error quaternion of the expected attitude to the current attitude in the forward projection case is obtained as follows:

[0054]

[0055] ​​​​

[0056] Based on the current satellite attitude q i2b The error quaternion from the desired attitude to the current attitude under negative projection is obtained as follows:

[0057]

[0058] in,() T This represents the conjugate transpose of a quaternion. Represents quaternion multiplication;

[0059] Obtain the Euler angles corresponding to the error quaternion in the positive case. For Δq + The scalar part;

[0060] Obtain the Euler angles corresponding to the error quaternion in the negative case. For Δq - The scalar part;

[0061] Compare the Euler angles corresponding to the error quaternion in the positive case and the Euler angles corresponding to the error quaternion in the negative case. The expected attitude quaternion of the satellite system relative to the inertial frame when the satellite points to the sky in the case with the smaller Euler angle is taken as the final attitude control target.

[0062] Step 2 describes how the satellite achieves attitude convergence when pointing towards the sky, as detailed below:

[0063] Attitude control requires simultaneously controlling the satellite's attitude and attitude angular velocity to desired values. Specifically, the satellite's attitude must be controlled to the desired attitude quaternion corresponding to the satellite's own system relative to the inertial frame, and the satellite's attitude angular velocity must be controlled to the desired attitude angular velocity ω. bib_req The desired attitude angular velocity of 0 is also taken as the control target;

[0064] When the satellite points towards the sky, the desired attitude remains unchanged relative to inertial space, and the desired attitude angular velocity ω bib_req It is zero.

[0065] Preferably, step 3, which involves obtaining the push-broom angular velocity, push-broom angular direction, and push-broom duration, is as follows:

[0066] Obtain the push-broom angular velocity ω during skyward push-brooming. r , Push-broom duration Δt;

[0067] The ground camera is a linear array camera, and its push-broom imaging requires the push-broom angular velocity direction to be along the +y direction of the camera coordinate system. c Axial direction;

[0068] Step 3, which involves determining the Euler axis of rotation, is as follows:

[0069] The push-broom direction vector, i.e., the rotating Euler axis, is projected in the camera coordinate system as The push-broom direction vector is projected in the inertial system as:

[0070]

[0071] wherein, denotes quaternion multiplication;

[0072] The expected attitude quaternion of the satellite body coordinate system relative to the inertial system at the time of the sky push-broom, as described in step 3, is specifically as follows:

[0073] The attitude quaternion of the satellite body coordinate system relative to the inertial system at the time t0 of the start of the sky push-broom is

[0074] The installation matrix, i.e., the rotation matrix, of the ground camera is M B2Cam According to the relationship between the rotation matrix and the quaternion described in step 2, the quaternion of the satellite body coordinate system to the camera coordinate system is q b2c The attitude quaternion of the camera coordinate system of the ground camera relative to the inertial system is is

[0075]

[0076] At any time t in the push-broom, the angle θ turned by the satellite can be calculated p = ω r (t-t0);

[0077] The rotation quaternion of the satellite turning through an angle θ c around the +y p axis direction is and the expected attitude quaternion of the camera coordinate system relative to the inertial system is

[0078] Let q c2b = (q b2c ) T , the expected attitude quaternion of the satellite body coordinate system relative to the inertial system is

[0079] The expected angular velocity of the satellite body coordinate system relative to the inertial system, as described in step 3, is specifically as follows:

[0080] According to the size ω r of the push-broom angular velocity and the direction e yi of the push-broom angular velocity at the time of the sky push-broom, the expected angular velocity of the satellite in the inertial system is:

[0081] ω bii_req = ω r ·eyi

[0082] The satellite angular velocity is projected to the camera coordinate system of the earth camera

[0083] Wherein, ω bii_req The satellite angular velocity is projected to the inertial system;

[0084] The satellite angular velocity is projected to the satellite body coordinate system

[0085] The application further provides a computer readable medium, which stores a computer program executed by an electronic device, and when the computer program runs on the electronic device, the steps of the satellite sky pointing attitude control method are executed.

[0086] Compared with the prior art, the application has the advantages that:

[0087] The satellite sky pointing attitude control of the star / earth camera under the complex constraints of the sun / earth blocking angle multi-variable can meet the on-orbit calibration requirement of the earth camera and multiple star cameras, and maximizes the included angle between the optical axis of the star / earth camera and the earth-star and sun-star connecting line, thereby avoiding the influence of the sun light and the earth reflected stray light on the imaging of the star / earth camera.

[0088] The satellite sky pointing push-broom attitude control around the fixed rotating Euler axis controls the satellite attitude angle and the attitude angular velocity, and compared with the conventional satellite angular velocity control which only controls the attitude angular velocity, the attitude control precision is higher, and the method is more suitable for the processing of the remote sensing image after the push-broom imaging of the linear array earth camera.

[0089] The satellite sky pointing and push-broom attitude control method applied to the star / earth camera included angle on-orbit calibration of the remote sensing satellite solves the satellite attitude control problem when the linear array earth camera and the star camera simultaneously image the star, conquers the complex geometric constraint problem based on the sun / earth blocking angle and the star-earth-sun position relationship, and meets the on-orbit calibration requirement of the star / earth camera included angle of the remote sensing satellite. BRIEF DESCRIPTION OF DRAWINGS

[0090] Figure 1 The method flowchart of the embodiment of the application;

[0091] Figure 2 The included angle diagram of the satellite to the sun and to the earth of the embodiment of the application;

[0092] Figure 3 The change process diagram of the included angle to the sun and to the earth of the embodiment of the application; ​

[0093] Figure 4 Figure 1 is a time response curve diagram of a deviation between an actual Euler angle of a satellite and an expected Euler angle of the satellite according to an embodiment of the present application;

[0094] Figure 5 Figure 2 is a time response curve diagram of an actual three-axis attitude angular velocity of a satellite, an actual attitude angular velocity and a deviation between the actual attitude angular velocity and an expected attitude angular velocity according to an embodiment of the present application;

[0095] Figure 6 Figure 3 is a time response curve diagram of an actual three-axis attitude angular velocity of a satellite, an actual attitude angular velocity and a deviation between the actual attitude angular velocity and an expected attitude angular velocity according to an embodiment of the present application. DETAILED DESCRIPTION

[0096] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0097] In the implementation, the method proposed by the technical solutions of the present application can be automatically run by computer software technology, and the system device of the method, such as a computer readable storage medium storing the corresponding computer program of the technical solutions of the present application and a computer device including the running of the corresponding computer program, should also be within the protection scope of the present application.

[0098] The specific implementation of the present application will be described below. Figures 1-6 The present application introduces a remote sensing satellite pointing attitude control method.

[0099] As shown in Figure 1 Figure 1 is a flow chart of the method according to an embodiment of the present application, which specifically includes the following steps:

[0100] Step 1: Obtain the day shading angle of the star camera, the day shading angle of the star camera, the day shading angle of the ground camera, the day shading angle of the ground camera, obtain the direction vector of the satellite pointing to the earth center, the direction vector of the satellite pointing to the sun according to the current time and the orbit information, obtain the installation matrix of the ground camera, the installation matrix of the star camera A and the installation matrix of the star camera B;

[0101] The day shading angle of the star camera in step 1 is defined as: λ st_sun ;

[0102] The day shading angle of the star camera in step 1 is defined as: λ st_earth ;

[0103] The day shading angle of the star camera in step 1 is defined as: λ cam_sun ;

[0104] The ground-shading angle of the ground camera in step 1 is defined as λ cam_earth ;

[0105] The direction vector of the satellite pointing to the center of the earth in step 1 is defined as r e ;

[0106] The direction vector of the satellite pointing to the sun in step 1 is defined as r s ;

[0107] The ground camera of the satellite in step 1 is configured as a ground camera;

[0108] The star camera of the satellite in step 1 is configured as a star camera A and a star camera B;

[0109] The installation orientation information of the ground camera in step 1 is that the optical axis is not strictly directed to the +z b axis direction of the satellite body coordinate system;

[0110] The installation orientation information of the star camera in step 1 is that the star camera A and the star camera B are not strictly mirror symmetric about the Oy b z b plane of the satellite body coordinate system, and the optical axes are both deviated to the +y b direction;

[0111] The installation matrix of the ground camera in step 1 is defined as M B2Cam ;

[0112] The installation matrix of the star camera A in step 1 is defined as M B2STA ;

[0113] The installation matrix of the star camera B in step 1 is defined as M B2STB ;

[0114] In this embodiment, the sun-shading angle λ st_sun of the star camera is 30°, the earth-shading angle λ st_earth is 100.4°, the sun-shading angle λ cam_sun of the ground camera is 35°, and the earth-shading angle λ cam_earth is 105.4°. The included angle between the star / ground camera is about 136°, and the included angle between the two star cameras is about 70°.

[0115] In this embodiment, the other required related prior information parameters are as follows:

[0116] Satellite parameters:

[0117] Mass: m = 343 kg,

[0118] Moment of inertia matrix: ​​

[0119] Attitude parameters:

[0120] Initial relative orbit system Euler angles:

[0121] Orbit parameters:

[0122] Semi-major axis: a = 6878.14 km,

[0123] Eccentricity: e = 0,

[0124] Orbit inclination: i = 97.4065°,

[0125] Longitude of ascending node: Ω = 195.436°,

[0126] Argument of perigee: ω = 0,

[0127] True anomaly: f = 0.

[0128] Actuator parameters:

[0129] Reaction flywheel moment of inertia: I x = 0.00636 kg m 2 ,I z = 0.00636 kg m 2 ,I s = 0.00636 kg m 2 ,

[0130] Maximum rotation speed of reaction flywheel:

[0131] Maximum output torque of reaction flywheel: M x,z,s = 0.1 Nm,

[0132] Large torque flywheel moment of inertia: I y = 0.0875 kg m 2 ,

[0133] Maximum rotation speed of reaction flywheel:

[0134] Maximum output torque of reaction flywheel: M y = 1 Nm.

[0135] Sensor parameters:

[0136] Star sensor measurement error: x, y direction ≤ 3.0", z direction ≤ 25",

[0137] Fiber-optic gyroscope zero offset stability: ≤ 0.01° / h (100 s, 1σ).

[0138] See Figure 2, the detailed steps included in step 2 are described in detail below.

[0139] Step 2: Calculate the expected attitude quaternion of the satellite body relative to the inertial system when the satellite points to the sky, and realize the attitude convergence when the satellite points to the sky;

[0140] The calculation of the expected attitude quaternion of the satellite body relative to the inertial system when the satellite points to the sky in step 2 is as follows:

[0141] Step 2.1: Obtain the coordinates of the ground camera optical axis in the ground camera coordinate system as z Camb =(0 01) T , the coordinates of the satellite body coordinate system as r Cam =(M B2Cam ) T ·z Camb , and the rotation quaternion of the satellite body coordinate system to the ground camera coordinate system is q B2Cam .

[0142] The coordinates of the star camera A optical axis in the star camera A body coordinate system are z STAb =(0 0 1) T , and the coordinates in the satellite body coordinate system are r STA =(M B2STA ) T ·z STAb .

[0143] The coordinates of the star camera B optical axis in the star camera B body coordinate system are z STBb =(0 0 1) T , and the coordinates in the satellite body coordinate system are r STB =(M B2STB ) T ·z STBb .

[0144] The projection of the star camera A optical axis in the satellite body coordinate system Oy b z b plane is r projSTA =r STA +x b ·cos<-r STA ,x b >=r STA +(-r STA ·x b )x b , and the projection of the star camera B optical axis in the satellite body coordinate system Oy b z bThe projection on the plane is r projSTB =r STB -x b ·cos<-r STB ,-x b >=r STB -(r STB ·x b )x b .

[0145] The optical axes of Star Camera A and Star Camera B in the satellite's body coordinate system Oy b z b The direction vector r of the projection vectors on the plane projSTAB ,but:

[0146] r projSTAB =(r projSTA +r projSTB ) / ||r projSTA +r projSTB ||

[0147] Where |||| denotes the second norm of the vector;

[0148] Step 2.2: See Figure 2 To ensure that the optical axes of the Earth camera and star cameras A and B avoid the Earth and the Sun, their optical axes are aligned with r. e r s The included angle must be no less than the corresponding sun / earth shading angle.

[0149] Consider maximizing the direction vector r between the optical axis and the satellite pointing towards the Earth's center. e The direction vector r of the satellite pointing towards the sun s The angle between the two points causes the satellite's attitude to point towards the sky, r projSTAB With r Cam and r e Coplanar, r projSTAB r Cam The plane formed and r e and r s The planes formed are perpendicular, and r projSTAB r Cam Regarding r e and r s The plane formed is mirror symmetric, r projSTAB r Cam The included angle is:

[0150] θ = arccos(r) projSTAB ·r Cam )

[0151] Where arccos represents the inverse cosine, and θ represents the optical axes of star camera A and star camera B in the satellite body coordinate system. Oy b z b The direction vector of the projection vector sum on the plane and the optical axis of the ground camera in the satellite body coordinate system The angle between the coordinates;

[0152] r Cam With r e The included angle is 180° - θ / 2, r projSTAB With r e The included angle is 180° - θ / 2;

[0153] r Cam With r s The included angle is greater than θ / 2, r projSTAB With r s The included angle is greater than θ / 2;

[0154] See Figure 3 In this embodiment, when the satellite is in the sky-pointing attitude described above, and the angle between the sun and the ground varies within the range of 1° to 179°, the minimum angle between the ground camera and the sun is 68.0° and the angle between the ground camera and the ground is 112.1°. The minimum angle between the two satellite cameras and the sun is 49.0° and the angle between the satellite cameras and the ground is 107.9°, all of which are greater than the corresponding sun / ground obscuration angle.

[0155] Step 2.3: r s and r e The direction vector of the plane normal is: |||| denotes the 2-norm of a vector;

[0156] r Cam In n se The upper projection is positive, r projSTAB In n se A negative upward projection is defined as a positive projection.

[0157] In the case of forward projection, r Cam The direction vector in the inertial frame can be expressed as:

[0158]

[0159] r Cam In n se The upward projection is negative, r projSTAB In n se A positive upward projection is defined as the case of a negative projection.

[0160] In the case of negative projection, r Cam The direction vector in the inertial frame can be expressed as:

[0161]

[0162] In the forward projection case, the X-axis coordinate axis direction vector, the Y-axis coordinate axis direction vector and the Z-axis coordinate axis direction vector of the satellite body coordinate system in the inertial system are respectively:

[0163]

[0164]

[0165]

[0166] In the forward projection case, the rotation matrix from the inertial system to the satellite body coordinate system is:

[0167] Let the desired attitude quaternion of the satellite when pointing to the sky in the forward projection case be

[0168] According to the relationship between the rotation matrix and the quaternion, it can be obtained that:

[0169] According to the algebraic correspondence relationship, the desired attitude quaternion of the satellite body coordinate system relative to the inertial system when the satellite points to the sky in the forward projection case can be solved as

[0170] In the negative projection case, the X-axis coordinate axis direction vector, the Y-axis coordinate axis direction vector and the Z-axis coordinate axis direction vector of the satellite body coordinate system

[0171] in the inertial system are respectively:

[0172]

[0173]

[0174]

[0175] In the negative projection case, the rotation matrix from the inertial system to the satellite body coordinate system is:

[0176] According to the relationship between the rotation matrix and the quaternion in the forward projection case and the algebraic correspondence relationship, the desired attitude quaternion of the satellite body coordinate system relative to the inertial system when the satellite points to the sky in the negative projection case can be solved as

[0177] According to the current satellite attitude q i2b , the error quaternion of the desired attitude relative to the current attitude in the forward projection case is:

[0178] ​​

[0179]

[0180] Based on the current satellite attitude q i2b The error quaternion from the desired attitude to the current attitude under negative projection is obtained as follows:

[0181]

[0182] in,() T This represents the conjugate transpose of a quaternion. Represents quaternion multiplication;

[0183] Obtain the Euler angles corresponding to the error quaternion in the positive case. For Δq + The scalar part;

[0184] Obtain the Euler angles corresponding to the error quaternion in the negative case. For Δq - The scalar part;

[0185] Compare the Euler angles corresponding to the error quaternion in the positive case and the Euler angles corresponding to the error quaternion in the negative case. The expected attitude quaternion of the satellite system relative to the inertial frame when the satellite points to the sky in the case with the smaller Euler angle is taken as the final attitude control target.

[0186] Step 2 describes how the satellite achieves attitude convergence when pointing towards the sky, as detailed below:

[0187] Attitude control requires simultaneously controlling the satellite's attitude and attitude angular velocity to the desired values. This means controlling the satellite's attitude to the attitude corresponding to the desired attitude quaternion of the satellite's own system relative to the inertial frame, and controlling the satellite's attitude angular velocity to the desired attitude angular velocity.

[0188] When the satellite points towards the sky, the desired attitude remains unchanged relative to inertial space, and the desired attitude angular velocity ω bib_req It is zero.

[0189] In this embodiment, as Figure 4 As shown, the satellite completed attitude control from ground orientation to sky orientation within 120 seconds, with attitude maneuvering exceeding 100°, and the satellite's three-axis attitude control accuracy was better than 0.05° (3σ).

[0190] In this embodiment, as Figure 5 As shown, the satellite's attitude angular velocity toward the sky converged after 120 seconds, and the satellite's three-axis attitude control stability was better than 0.001° / s (3σ).

[0191] Step 3: After the satellite's orientation towards the sky converges, the push-broom angular velocity, push-broom direction, and push-broom duration are obtained in accordance with the requirements and constraints of the on-orbit calibration. The Euler axis of rotation is determined, and the desired attitude quaternion of the satellite's own system relative to the inertial frame and the desired attitude angular velocity of the satellite's own system relative to the inertial frame are solved during the satellite's sky push-broom. The satellite performs sky push-broom according to the push-broom angular velocity and duration.

[0192] Step 3, which involves obtaining the push-broom angular velocity, push-broom angular direction, and push-broom duration, is detailed below:

[0193] Obtain the push-broom angular velocity ω during skyward push-brooming. r , Push-broom duration Δt;

[0194] The ground camera is a linear array camera, and its push-broom imaging requires the push-broom angular velocity direction to be along the +y direction of the camera coordinate system. c Axial direction;

[0195] Step 3, which involves determining the Euler axis of rotation, is as follows:

[0196] The push-broom direction vector, i.e., the Euler axis of rotation, is projected onto the camera coordinate system as follows: The projection of the push-broom direction vector onto the inertial frame is:

[0197]

[0198] in, Represents quaternion multiplication;

[0199] The desired attitude quaternion of the satellite's own system relative to the inertial frame during the satellite's sky-penetrating sweep, as described in step 3, is as follows:

[0200] At the start time t0 of the sky sweep, the attitude quaternion of the satellite's body coordinate system relative to the inertial frame is:

[0201] The mounting matrix, or rotation matrix, of the ground camera is M. B2Cam Based on the relationship between the rotation matrix and quaternions described in step 2, the quaternion from the satellite body coordinate system to the camera coordinate system can be obtained as q. b2c The camera's attitude quaternion relative to the inertial frame is: for

[0202]

[0203] At any time t during push-broom operation, the angle θ that the satellite has rotated through can be calculated. p =ω r (t-t0);

[0204] The satellite orbits +y c Rotate θ in the axial direction p angular rotation quaternion and the desired attitude quaternion of the camera coordinate system relative to the inertial frame.

[0205] Let q c2b =(q b2c ) T Satellite body coordinate system Desired attitude quaternion relative to the inertial frame

[0206] Step 3, which involves determining the desired attitude angular velocity of the satellite relative to the inertial frame, is as follows:

[0207] Based on the magnitude of the angular velocity ω during the sky sweeping process r and the direction of the push-broom angular velocity e yi The projection of the satellite's expected angular velocity in the inertial frame can be obtained as:

[0208] ω bii_req =ω r ·e yi

[0209] Projecting the desired angular velocity of the satellite onto the camera coordinate system of the ground camera yields...

[0210] Where, ω bii_req The satellite's expected angular velocity is projected onto the inertial frame;

[0211] Project the desired angular velocity of the satellite onto the satellite body coordinate system. have to

[0212] In this embodiment, as Figure 6 As shown, the satellite travels along the y-axis of the Earth camera coordinate system. c The satellite was pushed and swept in the sky at an angular velocity of 0.3° / s for 20s. The attitude angular velocity of the satellite converged within 2.5s, and the attitude control stability was 0.00080° / s (3σ) for the X-axis, 0.00052° / s (3σ) for the Y-axis, and 0.00053° / s (3σ) for the Z-axis.

[0213] The above Figures 4 to 6 The simulation results verified the remote sensing satellite's sky-pointing and push-broom attitude control method for on-orbit calibration of the star / ground camera angle proposed in this invention. It realizes that while controlling the satellite's attitude for sky-pointing and push-brooming, the star / ground camera simultaneously aligns with the star for imaging, and avoids the influence of sunlight and stray light reflected from the Earth, which can meet the requirements of on-orbit calibration tasks.

[0214] A specific embodiment of the present invention also provides a computer-readable medium.

[0215] The computer-readable medium is a server workstation;

[0216] The server workstation stores a computer program executed by the electronic device, which, when running on the electronic device, causes the electronic device to execute the steps of the remote sensing satellite pointing and push-broom attitude control method of the embodiments of the present application.

[0217] It should be understood that parts not described in detail in the specification are all part of the prior art.

[0218] It should be understood that the above description of the preferred embodiments is more detailed and is not considered as a limitation to the scope of patent protection of the present application. Any substitution or modification made by those skilled in the art without departing from the scope of the claims of the present application shall fall within the scope of protection of the present application. The scope of patent protection of the present application shall be subject to the appended claims.

Claims

1. A method for controlling the pointing attitude of a remote sensing satellite, characterized in that: Obtain the installation matrix of the ground camera, the installation matrix of satellite camera A, and the installation matrix of satellite camera B; Calculate the expected attitude quaternion of the satellite's own system relative to the inertial frame when the satellite is pointing towards the sky, and achieve attitude convergence when the satellite is pointing towards the sky; Solve for the desired attitude quaternion of the satellite's own system relative to the inertial frame and the desired attitude angular velocity of the satellite's own system relative to the inertial frame during satellite sky sweeping. The satellite performs sky sweeping according to the sweeping angular velocity and duration. Specifically, the following steps are included: Step 1: Obtain the configuration and prior information of the satellite / ground camera, and obtain the solar occlusion angle of the satellite camera, the ground occlusion angle of the satellite camera, the solar occlusion angle of the ground camera, and the ground occlusion angle of the ground camera. Based on the current time and orbit information, obtain the direction vector of the satellite pointing to the center of the Earth and the direction vector of the satellite pointing to the sun. Obtain the installation matrix of the ground camera, the installation matrix of satellite camera A, and the installation matrix of satellite camera B. Step 2: Calculate the desired attitude quaternion of the satellite's own system relative to the inertial frame when the satellite is pointing towards the sky, and achieve attitude convergence when the satellite is pointing towards the sky; Step 3: After the satellite's orientation towards the sky converges, the push-broom angular velocity, push-broom direction, and push-broom duration are obtained in accordance with the requirements and constraints of the on-orbit calibration. The Euler axis of rotation is determined, and the desired attitude quaternion of the satellite's own system relative to the inertial frame and the desired attitude angular velocity of the satellite's own system relative to the inertial frame are solved during the satellite's sky push-broom. The satellite performs sky push-broom according to the push-broom angular velocity and duration. The solar occlusion angle of the star camera mentioned in step 1 is defined as follows: ; The ground obscuration angle of the satellite camera mentioned in step 1 is defined as follows: ; The solar shading angle of the ground camera mentioned in step 1 is defined as follows: ; The ground shading angle of the ground camera mentioned in step 1 is defined as follows: ; The direction vector of the satellite pointing towards the Earth's center, as described in step 1, is defined as follows: ; The direction vector of the satellite pointing towards the sun in step 1 is defined as follows: ; The satellite's ground camera, as described in step 1, is configured as a ground camera; The satellite's camera configuration in step 1 is camera A and camera B; The azimuth information of the ground camera mentioned in step 1 is such that the optical axis does not strictly point to the satellite body coordinate system. of Axial direction; The satellite camera installation orientation information mentioned in step 1 refers to the coordinates of satellite camera A and satellite camera B relative to the satellite body coordinate system. of The plane is not strictly mirror-symmetric, and the optical axes are all biased. direction; The installation matrix of the ground camera mentioned in step 1 is defined as follows: ; The installation matrix of star camera A mentioned in step 1 is defined as follows: ; The installation matrix of star camera B mentioned in step 1 is defined as follows: ; Step 2, which calculates the desired attitude quaternion of the satellite's own system relative to the inertial frame when the satellite is pointing towards the sky, is as follows: Step 2.1: Obtain the optical axis of the ground camera in the satellite body coordinate system through satellite accuracy testing. coordinates The optical axis of the star camera A is in the satellite's body coordinate system coordinates The optical axis of the satellite camera B is in the satellite's body coordinate system. coordinates The optical axis of the star camera A is in the satellite's body coordinate system of Projected vector on the plane The optical axis of the satellite camera B is in the satellite's body coordinate system. of Projected vector on the plane The optical axes of Star Camera A and Star Camera B are in the satellite's body coordinate system. of The direction vector of the projection vector on the plane ,but: in, The second norm of a vector; Step 2.2: Consider maximizing the direction vector between the optical axis and the satellite pointing towards the Earth's center. The direction vector of the satellite pointing to the sun The angle between the two points determines when the satellite's attitude is pointing towards the sky. and and coplanar, , The plane formed and and The planes formed are perpendicular, and , about and The resulting plane is mirror symmetric. , The included angle is: Where arccos represents the inverse cosine, and θ represents the optical axes of star camera A and star camera B in the satellite body coordinate system. of The direction vector of the projection vector sum on the plane and the optical axis of the ground camera in the satellite body coordinate system The angle between the coordinates; and The included angle is , and The included angle is ; and The included angle is greater than , and The included angle is greater than ; Step 2.3: and The direction vector of the plane normal is: , The second norm of a vector; Will exist The upper projection is positive. exist A negative upward projection is defined as a positive projection. In the case of forward projection, The direction vector in the inertial frame can be expressed as: Will exist The upper projection is negative. exist A positive upward projection is defined as the case of a negative projection. In the case of negative projection, The direction vector in the inertial frame can be expressed as: In the case of orthographic projection, the satellite body coordinate system The projections of the X-axis direction vector, Y-axis direction vector, and Z-axis direction vector in the inertial frame are, in order: In the case of forward projection, the inertial frame to the satellite's own frame The rotation matrix is: Given the satellite pointing towards the sky under orthogonal projection, what is the desired attitude quaternion? From the relationship between rotation matrices and quaternions, we can obtain: Based on algebraic correspondence, the solvable expected attitude quaternion of the satellite's own system relative to the inertial frame when pointing towards the sky under the forward projection case is... ; In the case of negative projection, the satellite body coordinate system The projections of the X-axis direction vector, Y-axis direction vector, and Z-axis direction vector in the inertial frame are, in order: In the case of negative projection, the inertial frame to the satellite's own frame The rotation matrix is: Based on the relationship between the rotation matrix and quaternions in the positive projection case, and the algebraic correspondence, the expected attitude quaternion of the satellite's own system relative to the inertial frame when the satellite points towards the sky in the negative projection case can be obtained. ; Based on the current satellite attitude The error quaternion from the desired attitude to the current attitude under forward projection is obtained as follows: Based on the current satellite attitude The error quaternion from the desired attitude to the current attitude under negative projection is obtained as follows: in, This represents the conjugate transpose of a quaternion. Represents quaternion multiplication; Obtain the Euler angles corresponding to the error quaternion in the positive case. , for The scalar part; Obtain the Euler angles corresponding to the error quaternion in the negative case. , for The scalar part; Compare the Euler angles corresponding to the error quaternion in the positive case and the Euler angles corresponding to the error quaternion in the negative case. The expected attitude quaternion of the satellite system relative to the inertial frame when the satellite points to the sky in the case with the smaller Euler angle is taken as the final attitude control target. Step 2 describes how the satellite achieves attitude convergence when pointing towards the sky, as detailed below: Attitude control requires simultaneously controlling the satellite's attitude and attitude angular velocity to desired values. Specifically, the satellite's attitude must be controlled to the desired attitude quaternion corresponding to the satellite's own system relative to the inertial frame, and the satellite's attitude angular velocity must be controlled to the desired attitude angular velocity. The desired attitude angular velocity of 0 is also taken as the control target; When the satellite points towards the sky, the desired attitude remains unchanged relative to inertial space, and the desired attitude angular velocity is... Zero; Step 3, which involves obtaining the push-broom angular velocity, push-broom angular direction, and push-broom duration, is detailed below: Obtain the push-broom angular velocity during skyward push-brooming , sweeping duration ; The ground camera is a linear array camera, and its push-broom imaging requires the push-broom angular velocity direction to be along the camera coordinate system. Axial direction; Step 3, which involves determining the Euler axis of rotation, is as follows: The push-broom direction vector, i.e., the Euler axis of rotation, is projected onto the camera coordinate system as follows: The projection of the push-broom direction vector onto the inertial frame is: in, Represents quaternion multiplication; The desired attitude quaternion of the satellite's own system relative to the inertial frame during the satellite's sky-penetrating sweep, as described in step 3, is as follows: Sky sweeping start time The attitude quaternion of the satellite's body coordinate system relative to the inertial frame is: ; The mounting matrix of the ground camera, i.e., the rotation matrix, is as follows: Based on the relationship between the rotation matrix and quaternions described in step 2, the quaternion from the satellite body coordinate system to the camera coordinate system can be obtained as follows: The camera's attitude quaternion relative to the inertial frame is: for At any moment during push-broom The angle through which the satellite has rotated can be calculated. ; Satellite orbit Rotation in the axial direction angular rotation quaternion and the expected attitude quaternion of the camera coordinate system relative to the inertial frame. ; make Satellite body coordinate system Desired attitude quaternion relative to the inertial frame ; Step 3, which involves determining the desired attitude angular velocity of the satellite relative to the inertial frame, is as follows: Based on the magnitude of the angular velocity during skyward sweeping and the direction of the push sweep angular velocity The projection of the satellite's expected angular velocity in the inertial frame can be obtained as: Projecting the desired angular velocity of the satellite onto the camera coordinate system of the ground camera yields... ; in, The satellite's expected angular velocity is projected onto the inertial frame; Project the desired angular velocity of the satellite onto the satellite body coordinate system. have to .

2. A computer-readable medium, characterized in that, It stores a computer program executed by an electronic device, which, when run on the electronic device, causes the electronic device to perform the steps of the method as described in claim 1.

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