SADA turning angle calculation method and system

Abstract

The present invention discloses a SADA angle calculation method, comprising: obtaining attitude information of an on-orbit satellite; determining a parameter to be identified and an identification model according to the type of the on-orbit satellite, wherein the identification model is used to characterize the relationship between the parameter to be identified and the attitude information; and calculating the SADA angle of the on-orbit satellite according to the attitude information, the parameter to be identified and the identification model. The present invention utilizes the inherent resources of the on-orbit satellite to calculate the SADA angle, does not require additional devices, and reduces the calculation cost.

Description

Technical Field

[0001] The present invention relates to the field of satellite design technology, and in particular to a SADA turning angle calculation method and system. Background Art

[0002] The SADA (Solar Array Drive Assembly) of an on-orbit satellite is an actuator that controls the solar array to maintain its orientation to the sun. Its installation position runs through the inner and outer surfaces of the satellite, involving important subsystems such as control and power supply, and is a key single unit on the satellite. Its main function is to drive the sailboard to rotate so that its normal basically coincides with the solar beam to obtain as much solar energy as possible, thereby providing as much electrical energy as possible for the satellite. For satellites in geosynchronous orbit and sun-synchronous orbit, the drive mechanism drives the battery array to rotate continuously relative to the satellite at a negative satellite orbit angular velocity during the satellite's rotation around the earth to achieve the orientation of the battery array to the sun. Its secondary function is the attitude control system of synchronous orbit satellites. The main source of disturbance torque of synchronous satellites is solar radiation pressure. In order to make full use of solar energy and improve the utilization rate of solar energy, the solar panels installed on the on-orbit satellite need to track the sun as much as possible in real time, which mainly relies on the drive mechanism of the solar sail panel to achieve orientation to the sun. Small satellite networking realizes low-orbit IoT communication. The solar angle of its low-inclination orbit changes continuously over time, and it is necessary to accurately monitor the SADA state and feedback the attitude information of the solar sail panel in real time. Due to the small size, low cost and short R&D cycle of microsatellites, it is necessary to develop a targeted SADA angle estimation and monitoring mechanism. Summary of the invention

[0003] In view of this, the present invention provides a SADA angle calculation method and system, which utilizes the inherent resources of the on-orbit satellite to perform SADA angle calculation without the need for additional devices, thereby reducing the calculation cost.

[0004] In a first aspect, the present invention provides a SADA angle calculation method, characterized in that it includes:

[0005] Obtain attitude information of satellites in orbit;

[0006] Determining a parameter to be identified and an identification model according to the type of the on-orbit satellite, wherein the identification model is used to characterize the relationship between the parameter to be identified and the attitude information;

[0007] The SADA angle of the on-orbit satellite is calculated according to the attitude information, the parameters to be identified and the identification model.

[0008] The attitude information includes attitude quaternion, angular velocity and control torque.

[0009] Wherein, determining the parameters to be identified and the identification model according to the type of the on-orbit satellite includes:

[0010] If the on-orbit satellite is a flexible model, the parameter to be identified is determined to be a coupling coefficient matrix of the sailboard translation and rotation, and the identification model is a Lagrangian dynamics mixed coordinate model.

[0011] The expression of the Lagrangian dynamics mixed coordinate model is:

[0012]

[0013] In the formula, J sat is the moment of inertia of the satellite in orbit; m sat is the mass of the satellite in orbit; ν is the linear velocity of the center of mass translation of the satellite in orbit; η is the modal coordinate of the sailboard; Ω is the diagonal matrix of the constrained modal frequency of the sailboard; ε is the diagonal matrix of the damping ratio of the sailboard; B t B is the translational coupling coefficient of the sailboard relative to the center of mass; r is the rotation coupling coefficient of the sailboard relative to the center of mass; F is the external force; T is the control torque; ω is the angular velocity.

[0014] Wherein, determining the parameters to be identified and the identification model according to the type of the on-orbit satellite includes:

[0015] If the satellite is a rigid body model, the parameter to be identified is determined to be the whole satellite moment of inertia matrix, and the identification model is a rigid body satellite dynamics model.

[0016] Among them, the expression of the rigid satellite dynamics model is:

[0017]

[0018] In the formula, J sat is the moment of inertia of the satellite in orbit; ω is the angular velocity; T is the control torque.

[0019] Wherein, the calculating the SADA angle of the on-orbit satellite according to the attitude information, the parameter to be identified and the identification model includes:

[0020] Calculate the parameters to be identified by a preset algorithm according to the posture information and the identification model;

[0021] The SADA angle is calculated according to the parameters to be identified.

[0022] Wherein, when the on-orbit satellite is a flexible model, the preset algorithm is a modal identification algorithm, and the formula for calculating the SADA angle according to the parameters to be identified is:

[0023]

[0024] In the formula, r sa , b t , b r are all constants; Bt is the translational coupling coefficient of the sailboard relative to the center of mass; Br is the rotational coupling coefficient of the sailboard relative to the center of mass; A ba is the rotation matrix of the sailboard relative to the satellite body, that is, the SADA angle.

[0025] Wherein, when the on-orbit satellite is a rigid body model, the preset algorithm is an inertia identification algorithm, and the formula for calculating the SADA angle according to the parameters to be identified is:

[0026]

[0027] In the formula, J body is the moment of inertia of the satellite body, J sail is the moment of inertia of the sailboard in the sailboard coordinate system; A ba is the rotation matrix of the sailboard relative to the satellite body, that is, the SADA angle.

[0028] In a second aspect, the present invention also provides a SADA turning angle calculation system, comprising at least one processor; and at least one memory, wherein the at least one memory is coupled to the at least one processor and stores instructions for execution by the at least one processor, wherein the instructions, when executed by the at least one processor, cause the system to perform the steps of the method described in the first aspect.

[0029] In summary, the present invention provides a SADA angle calculation method, including: obtaining the attitude information of an on-orbit satellite; determining the parameters to be identified and the identification model according to the type of the on-orbit satellite, the identification model is used to characterize the relationship between the parameters to be identified and the attitude information; calculating the SADA angle of the on-orbit satellite according to the attitude information, the parameters to be identified and the identification model. The present invention utilizes the inherent resources of the on-orbit satellite to perform SADA angle calculation, without the need for additional devices, thereby reducing the calculation cost. The present invention is applicable to on-orbit satellites with single-axis and dual-axis SADA configurations, and is not limited by the current attitude mode of the satellite.

[0030] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites a preferred embodiment and describes it in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic flow chart of a SADA turning angle calculation method according to an embodiment of the present invention;

[0032] Figure 2 The figure is a schematic diagram of a specific flow chart of a SADA turning angle calculation method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the present invention is described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0034] Figure 1 FIG. 1 is a flow chart of a SADA angle calculation method according to an embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a SADA angle calculation method, which is applied to a SADA angle calculation system, including:

[0035] Step 201: Acquire attitude information of the satellite in orbit;

[0036] Step 202: Determine the parameters to be identified and the identification model according to the type of the satellite in orbit, where the identification model is used to characterize the relationship between the parameters to be identified and the attitude information;

[0037] Step 203: Calculate the SADA angle of the on-orbit satellite according to the attitude information, the parameters to be identified and the identification model.

[0038] In this embodiment, first, the attitude information of the satellite in orbit is collected, and the attitude information includes attitude quaternion q, angular velocity ω and control torque T. Secondly, some characteristic parameters of the satellite are estimated on orbit. Finally, based on the intrinsic relationship between the satellite characteristic parameters and the SADA angle, the SADA angle is estimated. It should be noted that the method proposed in the present invention considers the applicability of the algorithm and covers the satellite on-orbit SADA angle estimation including rigid body and flexible models. For low-cost commercial satellites, due to volume and cost considerations, adding additional monitoring devices causes complex structures and high costs. The present invention uses the inherent satellite resources on the satellite to identify the SADA angle estimation method of the satellite in orbit, which reduces the complexity of the drive device on the one hand, and improves the on-orbit reliability for the key single point of the SADA mechanism. For different satellite configurations and different orientations of single-axis and dual-axis SADA, the SADA angle calculation method provided by the present invention is applicable to the full-life angle calculation of single-axis and dual-axis on-orbit satellites.

[0039] It should be noted that when determining the parameters to be identified and the identification model according to the type of satellite in orbit, satellites can be divided into two categories: rigid satellites and flexible satellites, both of which include single-axis satellites and dual-axis satellites. A rigid body refers to an object whose shape and size remain unchanged during motion and after being subjected to force, and the relative positions of the internal points remain unchanged. An absolute rigid body does not actually exist, but is just an ideal model. Any object will deform more or less after being subjected to force. If the degree of deformation is extremely small relative to the geometric size of the object itself, the deformation can be ignored when studying the motion of the object. Accordingly, a flexible satellite generally refers to a satellite whose structure consists of a central rigid body and flexible appendages. The measurement and control actuators of this type of satellite attitude are all installed on the central rigid body, and the mass of the central rigid body is much greater than the mass of the flexible appendages. There are many types of flexible appendages for modern satellites, which can be hundreds of meters long or large-area parabolic flexible antennas, or flexible solar panels with a span of tens of meters. In order to reduce the mass of satellite launch, the stiffness and mass of these accessories are very small. The classical rigid body or semi-rigid body dynamics model can no longer accurately describe the dynamic characteristics of this type of satellite.

[0040] In this embodiment, the selection of rigid satellite and flexible satellite models is based on the perceptual cognition, which depends on the size of the satellite's flexible attachment (such as solar panels) relative to the center of the rigid body. Large panels usually use flexible models, while small panels (such as those currently equipped on most domestic commercial satellites) use rigid models. Differentiation from the data: Based on the finite element modal analysis of the satellite structure by the satellite structural designer, the first-order modal frequency of the satellite is given. If the first-order flexible mode is close to the natural frequency of the satellite's on-orbit attitude control, the flexible model must be selected during the satellite's attitude and orbit control design and analysis process. If the first-order flexible mode is much larger than the attitude control frequency, the attitude and orbit control design and analysis can use a rigid model to simplify the analysis. Generally speaking, if the first-order mode is 5 to 10 times larger than the control natural frequency, the control will not cause flexible vibration, and the satellite uses a rigid model.

[0041] In one embodiment, determining the parameters to be identified and the identification model according to the type of the satellite in orbit includes:

[0042] If the satellite in orbit is a flexible model, the parameter to be identified is the coupling coefficient matrix B of the sailboard translation and rotation t and B r , the identification model is the Lagrangian dynamics mixed coordinate model.

[0043] Specifically, the expression of the Lagrangian dynamics mixed coordinate model is:

[0044]

[0045] In the formula, J satis the moment of inertia of the satellite in orbit; m sat is the mass of the satellite in orbit; ν is the linear velocity of the center of mass of the satellite in orbit; η is the modal coordinate of the sailboard; Ω is the diagonal matrix of the constrained modal frequency of the sailboard; ε is the diagonal matrix of the damping ratio of the sailboard; B t B is the translational coupling coefficient of the sailboard relative to the center of mass; r is the rotation coupling coefficient of the sailboard relative to the center of mass; F is the external force; T is the control torque; ω is the angular velocity.

[0046] The dynamic mixed coordinate equation can be linearized as follows during calculation:

[0047]

[0048] Based on the above linearized equations, a variety of modal identification algorithms can be used for unconstrained modal identification, including but not limited to state space method, frequency method, subspace, OKID, OCID, neural network, etc.

[0049] Specifically, X=[r T q T η T ] T , u=[F T T T ] T ,have

[0050] in,

[0051]

[0052] C0=diag[0 0 2εΩ],

[0053] K0=diag[0 0 Ω 2 ],

[0054] B0=[I6 0 6×n ] T

[0055] r is the satellite orbital position, n is the modal η order, I n is the unit matrix of order n.

[0056] And because of the kinematic equation:

[0057]

[0058] make

[0059] Can be calculated back

[0060] Where g(q) is the pseudo-inverse matrix of the matrix f(q).

[0061] From the above formula, we can know

[0062] Where Γ=diag[I3 g(q) I n ], I3 is the third-order unit matrix.

[0063] It follows from this

[0064] Substituting the above calculation results into the expression of Lagrangian dynamics mixed coordinate model,

[0065] get

[0066] Considering the actual engineering situation, when the satellite is not in orbit control, the control force in the system can be considered to be only the control torque acting on the satellite itself (the actual normal state in orbit), and x = [q T ω T ] T , u=T as the observed quantity, modal identification can be performed and the rotational coupling coefficient B can be calculated at the same time r .

[0067] In one embodiment, determining the parameters to be identified and the identification model according to the type of the satellite in orbit includes:

[0068] If the satellite is a rigid body model, the parameter to be identified is the whole satellite moment of inertia matrix J sat , the identification model is the rigid satellite dynamics model.

[0069] Specifically, the expression of the rigid satellite dynamics model is:

[0070]

[0071] In the formula, J sat is the moment of inertia of the satellite in orbit; ω is the angular velocity; T is the control torque.

[0072] In this embodiment, for the moment of inertia identification, the recursive least squares method and its various variant algorithms are usually selected, including but not limited to weighted recursive squares, forgetting factor recursive squares, etc.

[0073] In one embodiment, the SADA angle of the on-orbit satellite is calculated according to the attitude information, the parameters to be identified and the identification model, including:

[0074] Calculate the parameters to be identified through a preset algorithm based on the posture information and the identification model;

[0075] Calculate the SADA angle based on the parameters to be identified.

[0076] Specifically, when the on-orbit satellite is a flexible model, the preset algorithm is a modal identification algorithm, and the formula for calculating the SADA angle according to the parameters to be identified is:

[0077]

[0078] In the formula, r sa 、b t 、b r are all constants; Bt is the translational coupling coefficient of the sailboard relative to the center of mass; Br is the rotational coupling coefficient of the sailboard relative to the center of mass; A ba is the rotation matrix of the sailboard relative to the satellite body, that is, the SADA angle.

[0079] It should be noted that under the flexible model, the relationship between the coupling coefficient matrix and the rotation matrix does not involve the relevant parameters of the single-axis and dual-axis, so the model can be applied to both single-axis and dual-axis in-orbit satellites.

[0080] In one embodiment, when the on-orbit satellite is a rigid body model, the preset algorithm is an inertia identification algorithm, and the formula for calculating the SADA angle according to the parameters to be identified is:

[0081]

[0082] In the formula, J sat is the moment of inertia of the satellite in orbit; J body is the moment of inertia of the satellite body, J sail is the moment of inertia of the sailboard in the sailboard coordinate system; A ba is the rotation matrix of the sailboard relative to the satellite body, that is, the SADA angle.

[0083] It should be noted that, under the rigid body model, the moment of inertia of the sailboard is involved in the relationship between the moment of inertia of the whole satellite and the rotation matrix. Therefore, the specific calculation data of the expression can be adjusted according to the number of sailboards on the in-orbit satellite, so that the model can be applied to both single-axis and dual-axis in-orbit satellites.

[0084] The embodiment of the present invention uses the on-board attitude, angular velocity and actuator control information to estimate the SADA real-time rotation angle on-orbit, without the need for additional drive device measurement equipment, thereby improving the satellite's own on-orbit reliability. It is applicable to satellites with single-axis and dual-axis SADA configurations, and the rotation angle algorithm is not limited by the satellite's current attitude mode.

[0085] Figure 2 FIG. 2 is a schematic diagram showing a specific flow chart of a SADA angle calculation method according to an embodiment of the present invention. Figure 2As shown in the figure, firstly, the satellite status information is collected. During the slow rotation of the sailboard and the maneuvering of the whole satellite, the current on-board attitude information is collected to output the attitude quaternion q and angular velocity ω, and the output control torque T of the actuator is obtained. In order to estimate the SADA angle, it is necessary to determine the identification model and the parameters to be identified according to the satellite structure design.

[0086] Determine whether the satellite is a flexible model. If so, for the satellite structure of a large flexible sailboard, consider that the satellite is in a slow rotation state, select the sailboard translation and rotation coupling coefficient matrix as the parameters to be identified, and select the general Lagrangian dynamics mixed coordinate as the identification model, the formula is:

[0087]

[0088] In the formula, J sat is the moment of inertia of the satellite in orbit; m sat is the mass of the satellite in orbit; ν is the linear velocity of the center of mass of the satellite in orbit; η is the modal coordinate of the sailboard; Ω is the diagonal matrix of the constrained modal frequency of the sailboard; ε is the diagonal matrix of the damping ratio of the sailboard; B t B is the translational coupling coefficient of the sailboard relative to the center of mass; r is the rotation coupling coefficient of the sailboard relative to the center of mass; F is the external force; T is the control torque; ω is the angular velocity.

[0089] Based on the satellite state and flexibility model, the modal identification algorithm is used to perform unconstrained modal identification of the entire satellite on orbit:

[0090] Let x = [q T ω T ] T , u=T, the dynamic mixed coordinate equation can be linearized as

[0091]

[0092] Based on the linearized equations of this step, a variety of modal identification algorithms can be used for unconstrained modal identification, including but not limited to state space method, frequency method, subspace, OKID, OCID, neural network, etc.

[0093] Based on the above content, the sailboard coupling coefficient matrix B t , B r , estimate the rotation matrix A of the sailboard relative to the satellite body ba Since the rotation matrix is ​​the primitive rotation expression of the SADA angle, the satellite on-orbit SADA angle estimation result under the flexible model is obtained.

[0094] In this step, the coupling coefficient matrix and the rotation matrix A ba The relationship is:

[0095]

[0096] In the formula, r sa , b t , b r are all constants and can be pre-fixed on the satellite; Bt is the translational coupling coefficient of the sailboard relative to the center of mass; Br is the rotational coupling coefficient of the sailboard relative to the center of mass; A ba is the rotation matrix of the sailboard relative to the satellite body, that is, the SADA angle.

[0097] If the satellite is not a flexible model, the SADA angle of the satellite in orbit is calculated according to the rigid body model. Specifically, for rigid body satellites, since the satellite structure is different from that of large flexible sailboard satellites, it is necessary to re-determine the identification parameters and identification model. The moment of inertia of the whole satellite can be selected as sat As the parameters to be identified, the general rigid satellite dynamics equation is selected as the identification model. Its expression is:

[0098]

[0099] J sat is the moment of inertia of the satellite in orbit; ω is the angular velocity; T is the control torque.

[0100] For the moment of inertia identification, the recursive least squares method and its various variants are usually selected, including but not limited to weighted recursive squares, forgetting factor recursive squares, etc.

[0101] Based on the above content, the whole star inertia matrix J sat , estimate the rotation matrix of the sailboard relative to the satellite body, that is, estimate the SADA angle.

[0102] Specifically, according to the moment of inertia J of the entire satellite sat With the rotation matrix A ba The SADA estimated turning angle is obtained by identifying the relationship between the two:

[0103]

[0104] In the formula, J sat is the moment of inertia of the satellite in orbit; J body is the moment of inertia of the satellite body, J sail is the moment of inertia of the sailboard in the sailboard coordinate system; A ba is the rotation matrix of the sailboard relative to the satellite body, that is, the SADA angle.

[0105] The SADA angle calculation method of the embodiment of the present invention obtains the attitude information of the on-orbit satellite; determines the parameters to be identified and the identification model according to the type of the on-orbit satellite, and the identification model is used to characterize the relationship between the parameters to be identified and the attitude information; and calculates the SADA angle of the on-orbit satellite according to the attitude information, the parameters to be identified and the identification model. The present invention uses the inherent resources of the on-orbit satellite to calculate the SADA angle, does not need to add additional devices, and reduces the calculation cost.

[0106] An embodiment of the present invention also provides a SADA turning angle calculation system, comprising at least one processor; and at least one memory, wherein the at least one memory is coupled to the at least one processor and stores instructions for execution by the at least one processor, and when the instructions are executed by the at least one processor, the system executes the SADA turning angle calculation method as described above.

[0107] The specific process of executing the above method steps in this embodiment is detailed in the relevant description of the above embodiment, which will not be repeated here.

[0108] An embodiment of the present invention further provides a computer storage medium having computer program instructions stored thereon; when the computer program instructions are executed by a processor, the SADA turning angle calculation method as described above is implemented.

[0109] The specific process of executing the above method steps in this embodiment is detailed in the relevant description of the above embodiment, which will not be repeated here.

[0110] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0111] In this document, the terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of elements other than those listed and may also include additional elements not expressly listed.

[0112] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A SADA angle calculation method, characterized in that: include: Acquiring attitude information of the satellite in orbit, wherein the attitude information includes attitude quaternion, angular velocity and control torque; Determining a parameter to be identified and an identification model according to the type of the on-orbit satellite, wherein the identification model is used to characterize the relationship between the parameter to be identified and the attitude information; Calculating the SADA angle of the on-orbit satellite according to the attitude information, the parameter to be identified and the identification model; The step of determining the parameters to be identified and the identification model according to the type of the on-orbit satellite comprises: If the on-orbit satellite is a flexible model, the parameter to be identified is determined to be a coupling coefficient matrix of the sailboard translation and rotation, and the identification model is a Lagrangian dynamics mixed coordinate model; If the satellite is a rigid body model, the parameter to be identified is determined to be the whole satellite moment of inertia matrix, and the identification model is a rigid body satellite dynamics model; The calculating the SADA angle of the on-orbit satellite according to the attitude information, the parameter to be identified and the identification model comprises: Calculate the parameters to be identified by a preset algorithm according to the posture information and the identification model; The SADA angle is calculated according to the parameters to be identified.

2. The SADA angle calculation method according to claim 1, characterized in that: The expression of the Lagrangian dynamics mixed coordinate model is: In the formula, J sat is the moment of inertia of the satellite in orbit; m sat is the mass of the satellite in orbit; ν is the linear velocity of the center of mass translation of the satellite in orbit; η is the modal coordinate of the sailboard; Ω is the diagonal matrix of the constrained modal frequency of the sailboard; ε is the diagonal matrix of the damping ratio of the sailboard; B t B is the translational coupling coefficient of the sailboard relative to the center of mass; r is the rotation coupling coefficient of the sailboard relative to the center of mass; F is the external force; T is the control torque; ω is the angular velocity.

3. The SADA angle calculation method according to claim 1, characterized in that: The expression of the rigid satellite dynamics model is: In the formula, J sat is the moment of inertia of the satellite in orbit; ω is the angular velocity; T is the control torque.

4. The SADA angle calculation method according to claim 1, characterized in that: When the on-orbit satellite is a flexible model, the preset algorithm is a modal identification algorithm, and the formula for calculating the SADA angle according to the parameters to be identified is: In the formula, r sa , b t , b r are all constants; Bt is the translational coupling coefficient of the sailboard relative to the center of mass; Br is the rotational coupling coefficient of the sailboard relative to the center of mass; A ba is the rotation matrix of the sailboard relative to the satellite body, that is, the SADA angle.

5. The SADA angle calculation method according to claim 1, characterized in that: When the on-orbit satellite is a rigid body model, the preset algorithm is an inertia identification algorithm, and the formula for calculating the SADA angle according to the parameters to be identified is: In the formula, J body is the moment of inertia of the satellite body, J sail is the moment of inertia of the sailboard in the sailboard coordinate system; A ba is the rotation matrix of the sailboard relative to the satellite body, that is, the SADA angle.

6. A SADA turning angle calculation system, characterized in that: comprising at least one processor; and at least one memory, the at least one memory being coupled to the at least one processor and storing instructions for execution by the at least one processor, the instructions, when executed by the at least one processor, causing the system to perform the steps of the method according to any one of claims 1 to 5.

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