Rolling angle calibration method for emergency anti-solar time of earth satellite

Abstract

The application discloses a method for calibrating a roll angle of an emergency anti-solar time of a satellite on the earth, which is beneficial to reestablishing a three-axis attitude of the satellite on the earth. Firstly, an angle between a projection of a sun vector on an orbit plane and an orbit system-X axis is calculated; then, whether a current orbit position meets a requirement is determined according to the angle between the projection of the sun vector on the orbit plane and the orbit system-X axis, and whether an absolute attitude reference is available at present is determined, if the current orbit position meets the requirement and the absolute attitude reference is available at present, the roll angle is calibrated at a current control beat; otherwise, the roll angle is not calibrated at the current control beat; if the roll angle is calibrated at the current control beat, the roll angle is calculated based on the absolute attitude reference; if the roll angle is not calibrated at the current control beat, the roll angle is calculated by using gyro inertia angular velocity integration. The application can provide high-precision and reliable attitude information for reestablishing the attitude of the satellite on the earth.

Description

Technical Field

[0001] This invention relates to a method for calibrating the roll angle of an Earth-based satellite during emergency Sun-alignment, belonging to the field of satellite attitude control and orbit calculation technology. Background Technology

[0002] Earth observation satellites operating in sun-synchronous orbits typically operate in a three-axis Earth-orientation mode, with the satellite's coordinate system largely aligned with its orbital coordinate system. Solar panels drive the solar array to align with the sun. To address anomalies such as attitude instability and sensor malfunctions, the satellite's solar orientation is used as an emergency mode to ensure power supply in special circumstances. During emergency solar orientation, the solar array is fixed in the X-axis direction, and the attitude and orbit control subsystem rotates the satellite to align its X-plane with the sun, ensuring reliable power supply. Then, based on ground commands, the satellite re-establishes its three-axis Earth-orientation attitude as needed.

[0003] Star sensors can serve as an attitude reference for emergency sun alignment, but they are often unusable in emergency mode due to limited field of view. Therefore, a solar sensor is chosen as the attitude reference. Initial alignment of the satellite's X-plane is achieved using information from 0-1 type solar sensors installed on various surfaces, followed by precise alignment using information from an analog solar sensor installed on the X-plane. During precise alignment, the analog solar sensor measures the satellite's pitch and yaw angles.

[0004] Analog sun sensors cannot measure the satellite's roll angle, and the satellite's rotation around its roll axis does not affect the alignment of the X-plane with the sun. Therefore, current technology does not impose specific control on the roll angle; instead, it uses the integral angle of the gyroscopic inertial angular velocity to prevent rapid rotation of the roll axis. However, the lack of absolute attitude calibration for the roll angle makes the satellite's Earth-orientation attitude uncertain during emergency sun alignment, potentially causing the star sensor head to point towards Earth and malfunction, thus affecting the satellite's ability to re-establish its Earth-orientation attitude. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a roll angle calibration method for emergency sun alignment of Earth-orbiting satellites. This method can provide high-precision and reliable attitude information for re-establishing the Earth-orbiting attitude of the satellite when the lack of absolute attitude calibration of the roll angle makes the change of the satellite's Earth-orbiting attitude uncertain during emergency sun alignment.

[0006] The technical solution of the present invention is as follows: Firstly, a method for calibrating the roll angle during emergency sun alignment of an Earth-orbiting satellite is provided, comprising:

[0007] S1. Calculate the angle Δθ between the projection of the solar vector onto the orbital plane and the orbital system's -X-axis. s ;

[0008] S2, The included angle Δθ calculated according to step S1 s Determine whether the current track position meets the requirements, and at the same time determine whether there is a usable absolute attitude reference. If the current track position meets the requirements and there is a usable absolute attitude reference, then calibrate the roll angle in the current control cycle; otherwise, do not calibrate the roll angle in the current control cycle.

[0009] S3. Based on the judgment in step S2, if the current control cycle calibrates the roll angle, then the roll angle is calculated based on the absolute attitude reference; if the current control cycle does not calibrate the roll angle, then the roll angle is calculated using the integral of the gyro inertial angular velocity.

[0010] Preferably, in step S1, the angle Δθ between the projection of the solar vector onto the orbital plane and the orbital system's X-axis is... s Calculate based on the following cases:

[0011] If Δθ is chosen s Calibration is performed near 0, Δθ s The calculation method is as follows:

[0012]

[0013] If Δθ is chosen s Calibration is performed when the value is near π, Δθ s The calculation method is as follows:

[0014] Δθ s =arctan2(S oz ,S ox )+π

[0015] Among them, S ox S oz These are the X and Z components of the projection of the solar vector onto the orbital system, calculated based on the current time and orbit. The range "near 0" refers to [-0.01, 0.01], and the range "near π" refers to [π-0.01, π+0.01].

[0016] Preferably, the included angle Δθ calculated in step S1 is used. s To determine whether the track position meets the requirements, the specific method is as follows:

[0017] If Δθ is chosen s If calibration is performed near 0, then in the previous control cycle Δθ s >0 and the current control cycle Δθ s When ≤0, the track position of the current control cycle is considered to meet the requirements;

[0018] If Δθ is chosen s If calibration is performed near π, then in the previous control cycle Δθ s>π and the current control cycle Δθ s When ≤π, the track position of the current control cycle is considered to meet the requirements;

[0019] The range referred to as "near 0" is [-0.01, 0.01], and the range referred to as "near π" is [π-0.01, π+0.01].

[0020] Preferably, when determining whether there is an available absolute attitude reference, the absolute attitude reference is the attitude measured by the star sensor or the attitude determined by the dual-vector attitude determination algorithm.

[0021] Preferably, according to the judgment in step S2, if the current control cycle calibrates the roll angle, then the roll angle... The calculation method is as follows:

[0022]

[0023] Where [q0 q1 q2 q3] are the attitude quaternions of the satellite's own system relative to the orbital system based on the absolute attitude reference in step S2.

[0024] Preferably, if the current control cycle does not calibrate the roll angle, then the roll angle... Calculated using the integral of the gyroscope's inertial angular velocity, i.e.:

[0025]

[0026] ω x T is the inertial angular velocity of the satellite's roll axis measured by the gyroscope. c The duration corresponding to a control beat. The satellite roll angle is calculated for the previous control cycle; the initial calculation takes...

[0027] In a second aspect, the present invention provides a terminal device, comprising:

[0028] Memory, used to store at least one instruction executed by a processor;

[0029] The processor executes the instructions stored in the memory to implement the roll angle calibration method for emergency sun alignment of Earth-orbiting satellites as described above.

[0030] Thirdly, the present invention provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores computer instructions, which, when executed on a computer, cause the computer to perform the roll angle calibration method for emergency sun-orbiting of Earth-orbiting satellites as described above.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] This invention improves upon existing technologies by calibrating the roll angle using the sun-satellite-ground position relationship of the satellite at a specific orbital position. It optimizes the pointing of the star sensor when the satellite is flying in the Northern Hemisphere. It can provide high-precision and reliable attitude information for the satellite to re-establish its Earth attitude when the lack of absolute attitude calibration of the roll angle makes the change of the satellite's Earth attitude uncertain during emergency sun alignment. Attached Figure Description

[0033] Figure 1 This is a diagram showing the rotational relationship between the orbital system and the system itself during calibration of this invention;

[0034] Figure 2 This is a flowchart of the algorithm of the present invention. Detailed Implementation

[0035] To address the shortcomings of existing technologies, this invention provides a method for calibrating the roll angle of an Earth-based satellite during emergency Sun alignment. The method aims to optimize the pointing of the star sensor head when the satellite is operating in the Northern Hemisphere during emergency Sun alignment. It determines the optimal roll angle by utilizing the satellite-Earth-Sun position relationship at a specific orbital position and calibrates the integral angle of the inertial angular velocity of the roll axis gyroscope.

[0036] When an Earth observation satellite is operating normally, the yaw axis of this system and the yaw axis of the orbital system are basically aligned and point towards the ground. The star sensor layout is designed in this state to ensure that the star sensor head points towards the sky when the satellite's yaw axis is aligned with the Earth. Therefore, if the yaw axis of this system and the yaw axis of the orbital system are aligned as much as possible during an emergency solar observation period, it can be ensured that the star sensor's field of view avoids the area pointing towards the sky when the Earth is in sight.

[0037] The angle Δθ between the projection of the solar vector onto the orbital plane and the orbital system's X-axis s This is a crucial parameter for determining the solar panel's orientation. After the satellite's solar orientation stabilizes, Δθ s When π = 0 or π, the satellite's X-axis lies within the XOY plane of the orbital system. The orbital system can be aligned with the satellite's X-axis by two rotations around the yaw axis and roll axis, respectively. The rotation angles are the satellite's yaw angle and roll angle relative to the orbital system in the ZYX rotation sequence. In other words, the satellite's X-axis can be aligned with the orbital system's yaw axis by one rotation around the roll axis, and the satellite's roll angle can be calibrated based on this.

[0038] Appendix Figure 1 The two figures in the diagram illustrate the two rotation processes around the yaw axis and the rolling axis, respectively. Figure 1 In the middle, OX o Y o Z o O-X1Y1Z1 represents the orbital system, where O-X1Y1Z1 represents OX. o Y o Z o Coordinate system around Zo Axis rotation α Z The resulting coordinate system, O-X2Y2Z2, represents the O-X1Y1Z1 coordinate system rotated about the X1 axis by α. X The coordinate system after the O-X2Y2Z2 coordinate system is different from the OX coordinate system of our own system. b Y b Z b coincide.

[0039] Due to the sun-oriented nature of the system, calibration can only guarantee that the yaw axis of the system coincides with the yaw axis of the orbital system for a limited time before and after calibration. Considering my country's telemetry and control situation, it is better to perform calibration when the satellite is operating in the Northern Hemisphere. For sun-synchronous orbit satellites, Δθ should be selected when the local time of the ascending node is close to noon. s Calibration should be performed when the local time of the ascending node is near 0, and Δθ should be selected when the local time of the ascending node is close to midnight. s Calibration is performed when the π value is near.

[0040] Based on the above analysis, the control flow of the present invention is as follows: Figure 2 As shown, it includes the following steps:

[0041] Step S1: Calculate the angle Δθ between the projection of the solar vector onto the orbital plane and the orbital system's -X-axis. s

[0042] If Δθ is chosen s Calibration is performed near 0, Δθ s The calculation method is as follows:

[0043]

[0044] If Δθ is chosen s Calibration is performed when the value is near π, Δθ s The calculation method is as follows:

[0045] Δθ s =arctan2(S oz ,S ox )+π

[0046] Among them, S ox S oz These are the X and Z components of the projection of the solar vector onto the orbital system, calculated based on the current time and orbit. The range "near 0" refers to [-0.01, 0.01], and the range "near π" refers to [π-0.01, π+0.01].

[0047] Step S2: Determine whether calibration should be performed.

[0048] The following conditions must be met simultaneously to perform calibration: Δθ sReaching the specified angle and having a usable absolute attitude reference. Therefore, it is divided into the following two sub-steps:

[0049] Step S2-1: Determine the satellite's orbital position

[0050] The angle Δθ between the projection of the solar vector onto the orbital plane and the orbital system's X-axis, calculated in step S1, is used as an example. s Determine if the orbital position meets the requirements. If Δθ is selected... s If calibration is performed near 0, then in the previous control cycle Δθ s >0 and the current control cycle Δθ s When ≤0, the track position of the current control cycle is considered to meet the requirements; if Δθ is selected... s If calibration is performed near π, then in the previous control cycle Δθ s >π and the current control cycle Δθ s When ≤π, the track position of the current control cycle is considered to meet the requirements.

[0051] Step S2-2: Determine the absolute attitude reference state

[0052] Determine if there is an available absolute attitude reference. An absolute attitude reference can be a star sensor, a dual-vector attitude determination based on the solar vector and the geomagnetic vector, etc. Integrals based on gyro angular velocity or extrapolation are not considered absolute attitude references.

[0053] If the current control cycle passes the judgments of both of the above sub-steps, the roll angle is calibrated in the current control cycle, and the attitude quaternion of the satellite's own system relative to the orbital system based on the absolute attitude reference is used for subsequent calculations; otherwise, the roll angle is not calibrated in the current control cycle.

[0054] Step S3: Calculate the satellite roll angle

[0055] Based on the judgment in step S2, if the current control cycle calibrates the roll angle, the roll angle is obtained based on the absolute attitude reference, using the satellite's Earth-to-ground roll angle from the ZYX sequence, i.e.

[0056]

[0057] If the current control cycle does not calibrate the roll angle, the roll angle is obtained based on the angular velocity, using the integral of the gyro inertial angular velocity, i.e.:

[0058]

[0059] Where [q0 q1 q2 q3] are the attitude quaternions of the satellite's own system relative to the orbital system based on the available absolute attitude reference in step S2-2, and ω x T is the inertial angular velocity of the satellite's roll axis measured by the gyroscope. cThe duration corresponding to a control beat. This is the satellite roll angle calculated for the previous control cycle. The initial calculation uses...

[0060] Due to the restrictions on satellite orbit position in step S2-1, at most one control cycle per orbit can satisfy the condition for calibrating the roll angle. In most cases, the roll angle is still calculated using the integral of the gyro inertial angular velocity. Therefore, the "calibration" of this invention is manifested in "assigning a value" to the integral of the gyro inertial angular velocity at a specific orbit position, that is, setting the integral value to a specific value, and continuing to integrate based on this specific value.

[0061] In a second aspect, the present invention provides a terminal device, comprising:

[0062] Memory, used to store at least one instruction executed by a processor;

[0063] The processor executes the instructions stored in the memory to implement the roll angle calibration method for emergency sun alignment of Earth-orbiting satellites as described above.

[0064] Thirdly, the present invention provides a computer-readable storage medium, characterized in that the computer-readable storage medium stores computer instructions, which, when executed on a computer, cause the computer to perform the roll angle calibration method for emergency sun-orbiting of Earth-orbiting satellites as described above.

[0065] Example:

[0066] Taking a sun-synchronous orbit satellite with an ascending node local time of 13:30 as an example, since the satellite's ascending node local time is closer to noon, calibration is performed near 0. Following step S1 above, the angle between the projection of the solar vector onto the orbital plane and the orbital system's X-axis is calculated.

[0067]

[0068] An analog sun sensor mounted on the X-plane of the satellite measures its pitch and yaw angles. In most cases, the roll angle is measured using the integral of the gyroscopic inertial angular velocity.

[0069]

[0070] Where, ω x T is the inertial angular velocity of the satellite's roll axis measured by the gyroscope. c The duration corresponding to a control beat. The satellite roll angle is calculated for the previous control cycle. The initial value is zero.

[0071] Following step S2 above, in the previous control cycle Δθ s>0 and the current Δθ s When the value is ≤0, determine if there is a usable absolute attitude reference. Prioritize checking if the star sensor is available; secondly, consider absolute attitude references such as dual-vector attitude determination using the solar vector and geomagnetic vector. If a usable absolute attitude reference is available, calculate the satellite's attitude quaternion q = [q0 q1 q2 q3] relative to the orbital system based on the absolute attitude reference, and assign values ​​to the integral of the gyro inertial angular velocity.

[0072]

[0073] Subsequently, the roll angle is further calibrated using the integral of the gyroscopic inertial angular velocity, with the roll angle calculated using quaternions as the initial value. Then, a control algorithm is used to bring the roll angle closer to zero.

[0074] Although the present invention has been described in detail through the foregoing examples, it should be understood that the above description should not be considered as a limitation of the invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the foregoing. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0075] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A method for calibrating the roll angle of an Earth-based satellite during emergency sun-alignment, characterized in that... include: S1. Calculate the angle between the projection of the solar vector onto the orbital plane and the orbital system's X-axis. ; S2, the included angle calculated according to step S1 Determine whether the current track position meets the requirements, and at the same time determine whether there is an available absolute attitude reference. If the current track position meets the requirements and there is an available absolute attitude reference, then calibrate the roll angle in the current control cycle. Otherwise, the current control cycle will not calibrate the roll angle; S3. Based on the judgment in step S2, if the current control cycle calibrates the roll angle, then the roll angle is calculated based on the absolute attitude reference; if the current control cycle does not calibrate the roll angle, then the roll angle is calculated using the integral of the gyro inertial angular velocity. In step S1, the angle between the projection of the solar vector onto the orbital plane and the orbital system's X-axis is... Calculate based on the following cases: If you choose Calibration is performed when the value is near 0. The calculation method is as follows: If you choose exist Calibration is performed when the location is nearby. The calculation method is as follows: in, , These are the X and Z components of the projection of the solar vector onto the orbital system, calculated based on the current time and orbit. The range indicated by "near 0" is... " The area referred to as "nearby" is ; The included angle calculated in step S1 To determine whether the track position meets the requirements, the specific method is as follows: If you choose If calibration is performed near 0, then in the previous control cycle... And the current control rhythm At that time, it is considered that the track position of the current control cycle meets the requirements; If you choose exist If calibration is performed nearby, it will be done in the previous control cycle. And the current control rhythm At that time, it is considered that the track position of the current control cycle meets the requirements; The range referred to as "near 0" is " The area referred to as "nearby" is .

2. The method for calibrating the roll angle of an emergency Earth-orbiting satellite for sun alignment according to claim 1, characterized in that: When determining whether there is an available absolute attitude reference, the absolute attitude reference is the attitude measured by the star sensor or the attitude determined by the two-vector attitude determination algorithm.

3. The method for calibrating the roll angle of an emergency Earth-orbiting satellite for sun alignment according to claim 1, characterized in that: Based on the judgment in step S2, if the current control cycle calibrates the roll angle, then the roll angle... The calculation method is as follows: in, The attitude quaternion of the satellite system relative to the orbital system is based on the absolute attitude reference in step S2.

4. The method for calibrating the roll angle of an emergency Earth-orbiting satellite for sun alignment according to claim 1, characterized in that: If the current control cycle does not calibrate the roll angle, then the roll angle Calculated using the integral of the gyroscope's inertial angular velocity, i.e.: The inertial angular velocity of the satellite's roll axis measured by the gyroscope. The duration corresponding to a control beat. The satellite roll angle is calculated for the previous control cycle; the initial calculation takes... .

5. A terminal device, characterized in that, include: Memory, used to store at least one instruction executed by a processor; A processor for executing instructions stored in memory to implement the method as described in any one of claims 1-4.

6. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions that, when executed on a computer, cause the computer to perform the method as described in any one of claims 1-4.

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