A kind of star-borne telescope view axis pointing precision control system and method based on multimode smooth switching

Abstract

The application discloses a kind of based on multi-mode smooth switching's satellite-borne telescope visual axis pointing precision control system and method, to the data of star sensor multi-source fusion, combine target and satellite position information, according to satellite working condition or attitude angular velocity determination attitude working condition;Satellite attitude steady state uses star sensor data and gyro data fusion to obtain high-frequency high-precision attitude quaternion, attitude maneuver only with gyro data integral update high-frequency attitude quaternion, avoid star sensor dynamic error influence;When satellite is switched from maneuver to steady state, limit amplitude and linear compensation are carried out to gyro drift error using mode smooth strategy, to avoid visual axis pointing instantaneous jump;According to coordinate conversion and installation matrix, calculate telescope expected azimuth and pitch angle, drive servo system to realize accurate pointing.The application can work stably under the whole working condition of satellite, effectively solve the problem of pointing accuracy decline and image blur during maneuver, significantly improve mode switching smoothness and observation imaging quality.

Description

Technical Field

[0001] This invention belongs to the field of spaceborne telescope line-of-sight pointing control technology, specifically relating to a precise control system and method for spaceborne telescope line-of-sight pointing based on multi-mode smooth switching. Background Technology

[0002] Spaceborne telescopes, with their advantages of being unaffected by the atmosphere, operating in all weather conditions, and covering wide areas, are widely used in fields such as space situational awareness, space debris monitoring, laser communication, and astronomical observation. Line-of-sight (LOS) pointing control technology, as one of the key technologies to ensure stable and clear imaging, is a focus of spaceborne telescope technology research. Generally, spaceborne LOS pointing control methods can be divided into "optical closed-loop based LOS pointing control technology" and "guide information based LOS pointing control technology" based on their operating mode. The line-of-sight pointing control method based on optical closed loop can adapt to both high-dynamic and ground-dynamic conditions by utilizing high-frequency miss information obtained from image sensors. However, its dependence on miss information makes it unable to track faint targets (faint targets require long exposures to obtain image information, making it impossible to extract high-frequency miss information). The line-of-sight pointing control method based on guidance information guides the line-of-sight pointing using known target and local satellite orbit information, satellite attitude information, etc., thereby continuously tracking the target. Although this method is only suitable for low-dynamic conditions, it can provide stable pointing to the target for a long time because it does not rely on miss information to form a control closed loop, making it suitable for long-exposure conditions. In addition, the initial pointing alignment in the acquisition phase of space laser communication also utilizes this technology.

[0003] The line-of-sight pointing (LOS) control method based on optical closed-loop systems originated from ground-based theodolites and has become quite mature after years of development. While the LOS-based ...

[0004] Currently, line-of-sight pointing control methods based on guidance information are generally only applicable to steady-state satellite attitude conditions. This is primarily because the accuracy of satellite attitude measurement drops sharply during satellite attitude maneuvers, failing to provide an accurate attitude reference for telescope line-of-sight pointing. Satellite attitude measurement sensors typically obtain data through the fusion of two or more star sensors; however, time synchronization between star sensors is usually poor, and coupled with the poor dynamic performance of star sensors, the satellite attitude measurement error increases dramatically under maneuvering conditions with rapid changes in satellite attitude angles. To ensure the spaceborne telescope can operate normally under all conditions, this patent proposes a precise line-of-sight pointing control system and method for spaceborne telescopes based on multi-mode smooth switching. Summary of the Invention

[0005] To address the problem in existing technologies where the attitude measurement error of the satellite's own sensors increases sharply during satellite attitude maneuvers, leading to a decrease in the pointing accuracy of the telescope's line of sight based on guidance information and resulting in blurred images, this invention provides a precise control system and method for the pointing of a spaceborne telescope's line of sight based on smooth switching of multiple modes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for precise control of the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching includes the following process: Based on the acquired star-sensor information, multi-source data fusion is performed to obtain the low-frequency attitude quaternion of the satellite attitude. The satellite's attitude is determined to be maneuvering based on its operating conditions or attitude angular velocity; wherein, the satellite operating conditions include the low-frequency attitude quaternion, the target's position information in the inertial coordinate system, and the satellite's position information in the inertial coordinate system. If it is a satellite attitude maneuver, the low-frequency attitude quaternion is updated using the satellite attitude angular velocity as the reference, and the high-frequency attitude quaternion of the satellite attitude is obtained. The desired azimuth and elevation angles of the telescope are calculated using the high-frequency attitude quaternion, the unit vector of the satellite pointing to the target in the satellite body coordinate system, and the satellite and telescope mounting matrix. If the satellite attitude is in a steady state, the high-frequency satellite attitude quaternion is calculated through the fusion mode; Determine whether the satellite attitude has switched from a maneuver to a steady state based on the satellite's operating conditions or attitude angular velocity. If the satellite attitude changes from a maneuver to a steady state, the desired azimuth and elevation angles of the telescope are calculated through mode smoothing; otherwise, the desired azimuth and elevation angles of the telescope are calculated through high-frequency attitude quaternions, the unit vector of the satellite pointing to the target in the satellite body coordinate system, and the satellite and telescope mounting matrix. Determine whether the system is in the mode smoothing phase. If so, calculate the telescope's expected azimuth and elevation angles using mode smoothing. Otherwise, return to the process of determining whether the satellite's attitude is maneuvering based on the satellite's operating conditions or attitude angular velocity. Adjust the telescope's line-of-sight pointing according to the desired azimuth and elevation angles. If the telescope's line-of-sight pointing reaches the preset position, the mission ends; otherwise, return to the process of performing multi-source data fusion based on the acquired star-sensor information to obtain the low-frequency attitude quaternion of the satellite.

[0007] Preferably, a multi-source data fusion method is used to obtain the low-frequency attitude quaternion of the satellite attitude by weighted averaging or filtering two or more sets of different star-sensor information.

[0008] Preferably, the process of determining whether the satellite attitude is maneuvering includes: When the satellite's attitude angular velocity is greater than a certain threshold, it is determined that the satellite is undergoing attitude maneuvering; otherwise, it is determined that the satellite's attitude is stable.

[0009] Preferably, if it is a satellite attitude maneuver, the low-frequency attitude quaternion is updated using the satellite attitude angular velocity according to the following formula, based on the start time of the satellite attitude maneuver, to obtain the high-frequency attitude quaternion of the satellite attitude:

[0010]

[0011] in, For low-frequency attitude quaternions, t 0 represents the moment when the satellite's attitude transitions from a steady state to a maneuver. For high-frequency attitude quaternions, t t This is the moment when the satellite's attitude maneuver ends. The derivative of the quaternion is calculated based on the satellite's attitude and angular velocity information. For integration variables, For the satellite's attitude angular velocity, The angular velocity of the satellite's roll axis in the satellite's body coordinate system. The angular velocity of the satellite's pitch axis in the satellite's body coordinate system. This represents the yaw axis angular velocity of the satellite in the satellite's body coordinate system.

[0012] Preferably, the calculation process for the desired azimuth and elevation angles of the telescope includes: The unit vector of the satellite pointing to the target in the inertial frame is projected onto the satellite body coordinate system by using the high-frequency satellite attitude transformation matrix, thus obtaining the unit vector of the satellite pointing to the target in the satellite body coordinate system. By using the satellite and telescope mounting matrix, the unit vector of the satellite pointing to the target in the satellite body coordinate system is projected to the telescope base coordinate system to obtain the unit vector of the satellite pointing to the target in the telescope base coordinate system; Calculate the desired azimuth and elevation angles of the telescope based on the unit vector of the satellite pointing towards the target in the telescope base coordinate system.

[0013] Preferably, the satellite and telescope installation matrix is ​​obtained through calibration.

[0014] Preferably, if the satellite attitude is in a steady state, the process of calculating the high-frequency satellite attitude quaternion through the fusion mode includes: The low-frequency attitude quaternion and satellite attitude angular velocity information are fused using a Kalman filter algorithm to obtain the high-frequency satellite attitude quaternion.

[0015] Preferably, if the satellite attitude changes from a maneuver to a steady state, the specific process of calculating the telescope's desired azimuth and elevation angles through mode smoothing includes: The error caused by integral drift when calculating the desired azimuth and elevation angles of the telescope using high-frequency attitude quaternions is smoothed. The mode smoothing is divided into the following modes:

[0016] in, Indicates time, t 0 represents the moment when the satellite's attitude transitions from a steady state to a maneuver. This refers to the moment when the calculation method for satellite attitude quaternions switches from pure gyroscope mode to fusion mode. For a smooth termination time of the pattern, it is required that ; During mode smoothing The expected azimuth and elevation angles of the telescope calculated using the pure gyro mode are respectively , The expected azimuth and elevation angles of the telescope calculated from the fusion model are respectively , The differences between the desired azimuth angles and the errors between the desired pitch angles are respectively , The details are as follows:

[0017]

[0018] For error , If amplitude limiting is applied, then during mode smoothing... The desired azimuth and elevation angles of the telescope , for:

[0019]

[0020] in, For integration variables, and The error compensation increment for the limited amplitude is calculated as follows:

[0021] in,

[0022] in, , for The expected azimuth and elevation angles of the telescope are calculated using pure gyro mode at specific times. , for The expected azimuth and elevation angles of the telescope are calculated from the fusion model at any given time.

[0023] The present invention also provides a precise control system for the line-of-sight pointing of a spaceborne telescope based on multi-mode smooth switching, which is used to implement the precise control method for the line-of-sight pointing of a spaceborne telescope based on multi-mode smooth switching as described above. The system includes a star sensor, a three-axis gyroscope, a space service computer, a telescope computer, a servo control system, a telescope, and a telescope base. The star sensor is used to acquire star information, and the three-axis gyroscope is used to acquire the satellite's attitude angular velocity. The satellite computer is used to perform multi-source data fusion based on the acquired star-sensor information to obtain the low-frequency attitude quaternion of the satellite attitude; and to send the satellite status to the telescope computer. The satellite status includes the low-frequency attitude quaternion, the target's position information in the inertial coordinate system, and the satellite's position information in the inertial coordinate system. The telescope computer is used to determine whether the satellite attitude is maneuvering based on the satellite attitude angular velocity or the satellite operating status sent by the satellite service computer. If it is a satellite attitude maneuver, the telescope computer uses the satellite attitude angular velocity as the reference to update the low-frequency attitude quaternion and obtain the high-frequency attitude quaternion of the satellite attitude. The telescope computer uses the high-frequency attitude quaternion, the unit vector of the satellite pointing to the target in the satellite body coordinate system, and the satellite and telescope mounting matrix to calculate the telescope's expected azimuth and elevation angles. If the satellite is in a steady state, the telescope computer calculates the high-frequency satellite attitude quaternion through a fusion mode. The telescope computer determines whether the satellite attitude has switched from a maneuver to a steady state based on the satellite attitude angular velocity or the satellite operating status sent by the satellite service computer. If the satellite attitude changes from a maneuver to a steady state, the telescope computer calculates the desired azimuth and elevation angles of the telescope through mode smoothing; otherwise, the telescope computer calculates the desired azimuth and elevation angles of the telescope through high-frequency attitude quaternions, the unit vector of the satellite pointing to the target in the satellite body coordinate system, and the satellite and telescope mounting matrix. The telescope computer determines whether it is in the mode smoothing period based on the internal timer. If so, the telescope computer calculates the desired azimuth and elevation angles of the telescope through mode smoothing; otherwise, it returns to the process of the telescope computer determining whether the satellite attitude needs to maneuver based on the satellite's operating conditions or attitude angular velocity. The telescope computer controls the servo control system. The servo control system adjusts the telescope's line of sight pointing according to the desired azimuth and elevation angles. If the telescope's line of sight points to the preset position, the task ends; otherwise, it returns to the process where the satellite computer performs multi-source data fusion based on the acquired star-sensor information to obtain the low-frequency attitude quaternion of the satellite.

[0024] Preferably, the star sensors are installed on the satellite, and the number of star sensors is at least three; the star sensors are communicatively connected to the satellite's operational computer; the telescope base is installed on the satellite, the three-axis gyroscope is installed on or near the telescope base, the telescope is rotatably mounted on the telescope base, and the three-axis gyroscope is communicatively connected to the telescope computer in the satellite's operational computer; the operational computer and the telescope computer are communicatively connected, the telescope computer is communicatively connected to the servo control system, and the servo control system is connected to the telescope to drive the telescope to complete two-dimensional rotation and achieve line-of-sight pointing adjustment.

[0025] The present invention has the following beneficial effects: This invention, based on a multi-mode smooth switching method for precise line-of-sight (LOS) pointing control of spaceborne telescopes, effectively solves the problem that existing LOS pointing control methods based on guidance information can only adapt to steady-state satellite attitude conditions and suffer from decreased LOS pointing accuracy during attitude maneuvers due to a sharp increase in star sensor measurement errors. Its innovation lies in achieving precise LOS pointing control under all operating conditions through precise condition judgment, differentiated attitude updates, and smooth switching design. This method first obtains the low-frequency attitude quaternions of the satellite attitude through multi-source data fusion of star sensor information. Then, it determines whether the satellite attitude is maneuvering by combining the satellite's operating conditions and attitude angular velocity. For maneuvering conditions, using the maneuver start time as a reference, the low-frequency attitude quaternions are updated using the attitude angular velocity to obtain the high-frequency attitude quaternions, thus avoiding the accuracy defects of the star sensor during maneuvers. For steady-state conditions, the high-frequency attitude quaternions are calculated through a fusion mode. This method ensures steady-state pointing accuracy, thus overcoming the limitations of existing technologies in terms of applicable conditions. Simultaneously, it provides attitude switching and mode smoothing judgment steps. During the transition from maneuvering to steady state or mode smoothing, the desired azimuth and elevation angles of the telescope are calculated using mode smoothing, avoiding instantaneous line-of-sight jumps caused by gyro integral drift errors when directly switching modes, thus ensuring the stability of line-of-sight pointing. Furthermore, the entire method constructs a complete closed-loop control process, from low-frequency attitude quaternion acquisition, condition judgment, attitude update, mode switching to line-of-sight adjustment, and accuracy verification. If the preset position is not reached, it performs cyclic correction, enabling real-time response to dynamic changes in satellite attitude, continuously ensuring line-of-sight pointing accuracy, and eliminating reliance on high-frequency miss distance information. This adapts to conditions such as low-light target detection, significantly improving the practicality and accuracy of spaceborne telescope line-of-sight pointing control. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a spaceborne telescope system provided in an embodiment of the present invention.

[0027] Figure 2 This is a control block diagram of a spaceborne telescope system provided in an embodiment of the present invention.

[0028] Figure 3 This is a block diagram of the line-of-sight pointing control logic of a spaceborne telescope system provided in an embodiment of the present invention.

[0029] In the diagram, 1-Telescope (or spaceborne telescope), 2-Telescope line of sight, 3-Three-axis gyroscope, 4-Star sensor, 5-Satellite, 6-Solar panel, 7-Telescope base. Detailed Implementation

[0030] The present invention will now be clearly and completely described with reference to the accompanying drawings and embodiments. The described embodiments are merely a part of the embodiments of the present invention, and not all of them.

[0031] See Figure 1 and Figure 2 This embodiment of a spaceborne telescope line-of-sight pointing precision control system based on multi-mode smooth switching includes a star sensor 4, a three-axis gyroscope 5, a satellite computer, a telescope computer, a servo control system, a telescope 1, and a telescope base 7. The star sensor 4 is mounted on the satellite 5 and is communicatively connected to the satellite computer inside the satellite cabin. The telescope base 7 is mounted on the satellite 5, and the three-axis gyroscope 3 is mounted on or near the telescope base 7. The telescope 1 is rotatably mounted on the telescope base 7, and the three-axis gyroscope 3 is communicatively connected to the telescope computer inside the satellite cabin. The satellite computer and the telescope computer are communicatively connected, and the telescope computer is communicatively connected to the servo control system. The servo control system is connected to the telescope 1 and is used to drive the telescope 1 to complete two-dimensional rotation and achieve line-of-sight pointing adjustment.

[0032] In the above embodiments of the present invention, the number of star sensors 4 and three-axis gyroscopes 3 can be increased or decreased; or the three-axis gyroscopes 3 can be replaced with three single-axis gyroscopes.

[0033] Specifically, in the technical solution of this invention, the star sensor 4 is mainly used to measure satellite attitude information. Typically, a satellite is equipped with 3-4 star sensors for backup, and the accuracy of attitude measurement is improved by fusing information from multiple star sensors. Satellite attitude measurement information is generally low-frequency data (1-4Hz). The three-axis gyroscope is used to sense the satellite's attitude angular velocity and output high-frequency attitude angular velocity information. The telescope computer calculates the desired azimuth angle (A angle) and elevation angle (E angle) based on the satellite attitude angular velocity information provided by the three-axis gyroscope, the target and local satellite coordinate information provided by the satellite's onboard computer, and the satellite's attitude information. Then, through a servo control system, it controls the telescope to rotate in two dimensions to align the line of sight. Figure 3 The precise control method for the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching in this embodiment includes the following steps: 1. Solving for pointing vectors The target and satellite position coordinates provided by the satellite's onboard computer are unified in an inertial coordinate system, namely... and Therefore, the telescope's computer can calculate the unit vector pointing from the satellite to the target in the inertial frame. The calculation formula is as follows: (1) 2. Data fusion to solve high-frequency satellite attitude quaternions Using satellite attitude information provided by the satellite's onboard computer and gyroscope information provided by the three-axis gyroscope, the telescope computer can calculate the high-frequency satellite attitude transformation matrix. The calculation formula is as follows: (2) in, For low-frequency attitude quaternions, It is a scalar. Methods for obtaining the attitude transformation matrix of high-frequency satellites are divided into the following categories based on different satellite maneuvering conditions: 1) Fusion Mode (Satellite Attitude Steady State): The satellite attitude information (low-frequency attitude quaternion) provided by the satellite mission computer and the satellite attitude angular velocity information provided by the three-axis gyroscope are fused to obtain high-frequency, high-precision satellite attitude quaternion. The data fusion method adopts the Kalman filter algorithm.

[0034] 2) Pure gyro mode (satellite attitude maneuver): Assume the moment when the satellite's attitude changes from steady state to maneuver is At this time, the high-frequency, high-precision satellite attitude quaternion calculated by the telescope's computer is: During satellite attitude maneuvers, the satellite attitude quaternion in the telescope computer is updated using the following formula: (3) in, The variable to be integrated (i.e., time). This is the moment when the satellite's attitude maneuver ends. The quaternion derivative is calculated by the telescope computer using satellite attitude and angular velocity information provided by a three-axis gyroscope. The specific calculation method is as follows: (4) in The satellite attitude and angular velocity information is sensed by the three-axis gyroscope. The angular velocity of the satellite's roll axis in the satellite's body coordinate system. The angular velocity of the satellite's pitch axis in the satellite's body coordinate system. This represents the yaw axis angular velocity of the satellite in the satellite's body coordinate system.

[0035] 3. Coordinate Transformation The telescope computer uses the satellite attitude transformation matrix to convert the unit vector pointing the satellite at the target in the inertial frame. Projected onto the satellite's body coordinate system, as follows: (5) in, It is the unit vector pointing from the satellite to the target in the satellite body coordinate system, and is a 3×1 matrix; The attitude transformation matrix from the inertial coordinate system to the satellite body coordinate system is obtained from high-frequency, high-precision satellite attitude quaternions.

[0036] Telescope computers utilize satellite and telescope mounting matrices The unit vector pointing from the satellite to the target in the satellite's body coordinate system can be used. Projected onto the telescope base coordinate system, as follows: (6) Among them, satellite and telescope installation matrix It can be obtained through calibration and is a 3×3 matrix; This is the unit vector pointing from the satellite to the target in the telescope base coordinate system; it is a 3×1 vector.

[0037] 4. Solving for the pointing angle The telescope computer uses the unit vector of the satellite pointing at the target in the telescope base coordinate system. The desired azimuth angle of the telescope can be calculated. and pitch angle The details are as follows: (7) 4. Mode smoothing (satellite attitude transition from maneuver to steady state) When a satellite's attitude transitions from a maneuver to a steady state, the calculation method for high-frequency, high-precision satellite attitude quaternions in the telescope's computer switches from "pure gyro mode" to "fusion mode." However, due to the gyroscope's zero-bias instability, the attitude quaternions calculated in "pure gyro mode" inevitably suffer from integral drift. Furthermore, the longer the "pure gyro mode" lasts, the greater the integral drift error. Directly switching from "pure gyro mode" to "fusion mode" would inevitably lead to instantaneous changes in the calculated telescope line-of-sight. Therefore, smoothing is performed to address the error caused by integral drift. Assuming the satellite attitude quaternions... The calculation method switches from "pure gyroscope mode" to "fusion mode" at the following time. The smooth end time of the mode is The specific pattern divisions are as follows: (8) in, To indicate time, requires .

[0038] During mode smoothing The expected azimuth and elevation angles of the telescope calculated using the "pure gyro mode" are respectively , The expected azimuth and elevation angles of the telescope calculated by the "fusion mode" are respectively , Desired azimuth (i.e. and The difference between ) and the expected pitch angle (i.e. and The errors between them are respectively , The details are as follows: (9) If the error is limited, then during mode smoothing... The desired azimuth and elevation angles of the telescope are as follows: (10) in, and The increments for compensation of the expected azimuth error and the expected pitch error, which are subject to sizing limitations, are defined as follows: (11) in, (12) in, , for The telescope's expected azimuth and elevation angles are calculated using the "pure gyro mode" at all times. , for The expected azimuth and elevation angles of the telescope are calculated by the "fusion mode" at any time.

[0039] 6. Servo Control The telescope control computer, via a servo control system, adjusts the telescope's orientation according to the desired azimuth angle. and desired pitch angle Control the telescope to rotate and achieve precise aiming at the target.

[0040] As can be seen from the above scheme, the present invention addresses the problem that spaceborne telescopes cannot perform detection missions normally under satellite maneuvering conditions. It provides a precise control system and method for the line-of-sight pointing of spaceborne telescopes based on smooth switching of multiple modes. Under the steady state of satellite attitude, it uses multi-sensor fusion to calculate the desired azimuth and elevation angles of the telescope. Under the maneuvering conditions of satellite attitude, it uses pure gyro integration to calculate the desired azimuth and elevation angles of the telescope to avoid the adverse effects caused by the reduced measurement accuracy of star sensors. When switching modes, a smoothing strategy is used to eliminate the instantaneous jump problem caused by gyro integration error, so that the spaceborne telescope can point normally for detection missions under all operating conditions of the satellite.

[0041] The line-of-sight pointing control execution logic block diagram of the spaceborne telescope system in this embodiment is as follows: Figure 3 As shown The following will combine Figure 3 The technical solutions in the embodiments of the present invention will be clearly and completely described. The precise control method for the line-of-sight pointing of a spaceborne telescope based on multi-mode smooth switching in this embodiment specifically includes the following steps: Step 1: Based on the collected star sensor information, the satellite computer selects two star sensor data to perform multi-source data fusion, obtains the low-frequency attitude quaternion of the satellite attitude, and sends the low-frequency attitude quaternion of the satellite attitude, the target's position information in the J2000 coordinate system, and the local satellite's position information in the J2000 coordinate system to the telescope computer.

[0042] Step 2: The telescope computer determines whether the satellite attitude is maneuvering based on the satellite status or gyroscope data sent by the satellite service computer (i.e., if the satellite attitude angular velocity is greater than a certain threshold, the satellite attitude is maneuvering; otherwise, the satellite attitude is stable).

[0043] Step 3: If it is a satellite attitude maneuver, the telescope computer uses the satellite attitude maneuver start time as a reference and uses gyroscope data to update the attitude quaternion according to equations (3) and (4) in the above embodiment to obtain the satellite high-frequency attitude quaternion.

[0044] Step 4: The telescope computer calculates the desired azimuth and elevation angles of the telescope using equations (5), (6), and (7) in the above embodiments; if it is a steady-state satellite attitude condition, the telescope computer calculates the high-frequency satellite attitude quaternion through the "fusion mode".

[0045] Step 5: The telescope computer determines whether the satellite attitude has switched from a maneuver to a steady state based on the satellite status or gyroscope data sent by the satellite service computer. If the satellite attitude has switched from a maneuver to a steady state, the telescope computer calculates the desired azimuth and elevation angles of the telescope through "mode smoothing"; otherwise, the telescope computer calculates the desired azimuth and elevation angles of the telescope through equations (5), (6), and (7) in the above embodiments.

[0046] Step 7: The telescope computer determines whether it is in the "mode smoothing" period based on the internal timer. If so, the telescope computer calculates the desired azimuth and elevation angles of the telescope through "mode smoothing"; otherwise, it returns to Step 2.

[0047] Step 8: The telescope computer controls the telescope to complete two-dimensional rotation and adjust the direction of the line of sight through the servo control system.

[0048] Step 9: The telescope computer determines whether the mission is over based on the instructions from the satellite computer. If so, the mission ends; otherwise, Steps 1 through 9 continue to be executed.

[0049] In the above-described scheme of this invention, in the "fusion mode," the information fusion algorithm for high-frequency attitude quaternions includes the Kalman filter algorithm, but can also be replaced by other data fusion algorithms conventional in the art, such as extended Kalman filter, unscented Kalman filter, particle filter, weighted least squares fusion, optimal linear fusion, complementary filter, etc.

[0050] In the system proposed in this invention, the calculation of the desired azimuth and elevation angles of the telescope can be transferred from the telescope computer to the satellite computer.

[0051] The control system and method proposed in this invention can be extended to satellites in more operating conditions, such as steady-state attitude, low-speed attitude maneuvering, and high-speed attitude maneuvering.

[0052] As can be seen from the above solutions, the technical solution of the present invention has the following advantages: 1. In response to the problem of decreased telescope line-of-sight pointing accuracy caused by the sharp increase in attitude measurement error of the satellite's own sensors during satellite attitude maneuvers, this invention is applicable to both attitude maneuvers and steady-state conditions, unlike traditional methods which are only applicable to stable attitude conditions.

[0053] 2. The technical solution provided by this invention employs a "fusion mode" under steady-state satellite attitude conditions. This involves fusing satellite-provided attitude measurement data (low frequency, typically 1-4 Hz) with gyroscope data (high frequency) mounted on the telescope base to obtain high-precision, high-frequency satellite attitude information. The fused satellite attitude data is then used as a reference to calculate the telescope's line-of-sight pointing. Under satellite attitude maneuver conditions, a "pure gyroscope mode" is employed. This mode uses only gyroscope data to integrate the initial attitude (the fused satellite attitude information at the moment the satellite begins attitude maneuvering) to obtain high-precision, high-frequency satellite attitude information, which is then used as a reference to calculate the telescope's line-of-sight pointing.

[0054] 3. Due to the drift error of gyro integration, if the satellite attitude information calculation method is directly switched from "pure gyro mode" to "fusion mode" after the satellite enters steady state from attitude maneuver, it will inevitably cause an instantaneous jump in the telescope's line-of-sight (the magnitude of the jump depends on the magnitude of the gyro integration drift error), resulting in image blurring. Therefore, when correcting the error caused by gyro integration, amplitude limiting is performed to extend the pull-back action of the line-of-sight from instantaneous to tens of seconds or even minutes, thereby achieving smooth guidance of the line-of-sight pointing and smoothly pulling the target back to the center of the field of view, avoiding image quality degradation.

[0055] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for precise control of the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching, characterized in that, The process includes the following: Based on the acquired star-sensor information, multi-source data fusion is performed to obtain the low-frequency attitude quaternion of the satellite attitude. The satellite's attitude is determined to be maneuvering based on its operating conditions or attitude angular velocity; wherein, the satellite operating conditions include the low-frequency attitude quaternion, the target's position information in the inertial coordinate system, and the satellite's position information in the inertial coordinate system. If it is a satellite attitude maneuver, the low-frequency attitude quaternion is updated using the satellite attitude angular velocity as the reference, and the high-frequency attitude quaternion of the satellite attitude is obtained. The desired azimuth and elevation angles of the telescope are calculated using the high-frequency attitude quaternion, the unit vector of the satellite pointing to the target in the satellite body coordinate system, and the satellite and telescope mounting matrix. If the satellite attitude is in a steady state, the high-frequency satellite attitude quaternion is calculated through the fusion mode; Determine whether the satellite attitude has switched from a maneuver to a steady state based on the satellite's operating conditions or attitude angular velocity. If the satellite attitude changes from a maneuver to a steady state, the desired azimuth and elevation angles of the telescope are calculated through mode smoothing; otherwise, the desired azimuth and elevation angles of the telescope are calculated through high-frequency attitude quaternions, the unit vector of the satellite pointing to the target in the satellite body coordinate system, and the satellite and telescope mounting matrix. Determine whether the system is in the mode smoothing phase. If so, calculate the telescope's expected azimuth and elevation angles using mode smoothing. Otherwise, return to the process of determining whether the satellite's attitude is maneuvering based on the satellite's operating conditions or attitude angular velocity. Adjust the telescope's line-of-sight pointing according to the desired azimuth and elevation angles. If the telescope's line-of-sight pointing reaches the preset position, the mission ends; otherwise, return to the process of performing multi-source data fusion based on the acquired star-sensor information to obtain the low-frequency attitude quaternion of the satellite.

2. The method for precise control of the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching according to claim 1, characterized in that, By using a multi-source data fusion method that combines two or more sets of different star-sensor information with weighted averaging or filtering, the low-frequency attitude quaternion of the satellite attitude can be obtained.

3. The method for precise control of the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching according to claim 1, characterized in that, The process of determining whether a satellite's attitude has maneuvered includes: When the satellite's attitude angular velocity is greater than a certain threshold, it is determined that the satellite is undergoing attitude maneuvering; otherwise, it is determined that the satellite's attitude is stable.

4. The method for precise control of the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching according to claim 1, characterized in that, For satellite attitude maneuvers, using the start time of the maneuver as a reference, the low-frequency attitude quaternions are updated using the satellite attitude angular velocity according to the following formula to obtain the high-frequency attitude quaternions: in, For low-frequency attitude quaternions, t 0 represents the moment when the satellite's attitude transitions from a steady state to a maneuver. For high-frequency attitude quaternions, t t This is the moment when the satellite's attitude maneuver ends. The derivative of the quaternion is calculated based on the satellite's attitude and angular velocity information. For integration variables, For the satellite's attitude angular velocity, The angular velocity of the satellite's roll axis in the satellite's body coordinate system. The angular velocity of the satellite's pitch axis in the satellite's body coordinate system. This represents the yaw axis angular velocity of the satellite in the satellite's body coordinate system.

5. The method for precise control of the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching according to claim 1, characterized in that, The calculation process for the desired azimuth and elevation angles of the telescope includes: The unit vector of the satellite pointing to the target in the inertial frame is projected onto the satellite body coordinate system by using the high-frequency satellite attitude transformation matrix, thus obtaining the unit vector of the satellite pointing to the target in the satellite body coordinate system. By using the satellite and telescope mounting matrix, the unit vector of the satellite pointing to the target in the satellite body coordinate system is projected to the telescope base coordinate system to obtain the unit vector of the satellite pointing to the target in the telescope base coordinate system; Calculate the desired azimuth and elevation angles of the telescope based on the unit vector of the satellite pointing towards the target in the telescope base coordinate system.

6. The precise control of the line-of-sight pointing of a spaceborne telescope based on multi-mode smooth switching as described in claim 5, characterized in that, The satellite and telescope installation matrix is ​​obtained through calibration.

7. The method for precise control of the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching according to claim 1, characterized in that, If the satellite attitude is in a steady state, the process of calculating the high-frequency satellite attitude quaternion through the fusion mode includes: The low-frequency attitude quaternion and satellite attitude angular velocity information are fused using a Kalman filter algorithm to obtain the high-frequency satellite attitude quaternion.

8. The method for precise control of the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching according to claim 1, characterized in that, If the satellite attitude changes from a maneuver to a steady state, the specific process of calculating the telescope's desired azimuth and elevation angles through mode smoothing includes: The error caused by integral drift when calculating the desired azimuth and elevation angles of the telescope using high-frequency attitude quaternions is smoothed. The mode smoothing is divided into the following modes: in, Indicates time, t 0 represents the moment when the satellite's attitude transitions from a steady state to a maneuver. This refers to the moment when the calculation method for satellite attitude quaternions switches from pure gyroscope mode to fusion mode. For a smooth termination time of the pattern, it is required that ; During mode smoothing The expected azimuth and elevation angles of the telescope calculated using the pure gyro mode are respectively , The expected azimuth and elevation angles of the telescope calculated from the fusion model are respectively , The differences between the desired azimuth angles and the errors between the desired pitch angles are respectively , The details are as follows: For error , If amplitude limiting is applied, then during mode smoothing... The desired azimuth and elevation angles of the telescope , for: in, For integration variables, and The error compensation increment for the limited amplitude is calculated as follows: in, in, , for The expected azimuth and elevation angles of the telescope are calculated using pure gyro mode at specific times. , for The expected azimuth and elevation angles of the telescope are calculated from the fusion model at any given time.

9. A precise axis pointing control system for a spaceborne telescope based on multi-mode smooth switching, characterized in that, The method for precise control of the line-of-sight pointing of a spaceborne telescope based on smooth multi-mode switching as described in any one of claims 1-8 includes a star sensor, a three-axis gyroscope, a space service computer, a telescope computer, a servo control system, a telescope, and a telescope base. The star sensor is used to acquire star information, and the three-axis gyroscope is used to acquire the satellite's attitude angular velocity. The satellite computer is used to perform multi-source data fusion based on the acquired star-sensor information to obtain the low-frequency attitude quaternion of the satellite attitude; and to send the satellite status to the telescope computer. The satellite status includes the low-frequency attitude quaternion, the target's position information in the inertial coordinate system, and the satellite's position information in the inertial coordinate system. The telescope computer is used to determine whether the satellite attitude is maneuvering based on the satellite attitude angular velocity or the satellite operating status sent by the satellite service computer. If it is a satellite attitude maneuver, the telescope computer uses the satellite attitude angular velocity as the reference to update the low-frequency attitude quaternion and obtain the high-frequency attitude quaternion of the satellite attitude. The telescope computer uses the high-frequency attitude quaternion, the unit vector of the satellite pointing to the target in the satellite body coordinate system, and the satellite and telescope mounting matrix to calculate the telescope's expected azimuth and elevation angles. If the satellite is in a steady state, the telescope computer calculates the high-frequency satellite attitude quaternion through a fusion mode. The telescope computer determines whether the satellite attitude has switched from a maneuver to a steady state based on the satellite attitude angular velocity or the satellite operating status sent by the satellite service computer. If the satellite attitude changes from a maneuver to a steady state, the telescope computer calculates the desired azimuth and elevation angles of the telescope through mode smoothing; otherwise, the telescope computer calculates the desired azimuth and elevation angles of the telescope through high-frequency attitude quaternions, the unit vector of the satellite pointing to the target in the satellite body coordinate system, and the satellite and telescope mounting matrix. The telescope computer determines whether it is in the mode smoothing period based on the internal timer. If so, the telescope computer calculates the desired azimuth and elevation angles of the telescope through mode smoothing; otherwise, it returns to the process of the telescope computer determining whether the satellite attitude needs to maneuver based on the satellite's operating conditions or attitude angular velocity. The telescope computer controls the servo control system. The servo control system adjusts the telescope's line of sight pointing according to the desired azimuth and elevation angles. If the telescope's line of sight points to the preset position, the task ends; otherwise, it returns to the process where the satellite computer performs multi-source data fusion based on the acquired star-sensor information to obtain the low-frequency attitude quaternion of the satellite.

10. A precise control system for the line-of-sight pointing of a spaceborne telescope based on multi-mode smooth switching as described in claim 9, characterized in that, The star sensor (4) is installed on the satellite (5), and the number of star sensors (4) is at least 3. The star sensor (4) is connected to the satellite computer in the satellite cabin. The telescope base (7) is installed on the satellite (5), and the three-axis gyroscope (3) is installed on or near the telescope base (7). The telescope (1) is mounted on the telescope base (7) in a two-dimensional rotatable manner. The three-axis gyroscope (3) is connected to the telescope computer in the satellite cabin. The satellite computer is connected to the telescope computer in a communication relationship. The telescope computer is connected to the servo control system in a communication relationship. The servo control system is connected to the telescope (1) to drive the telescope (1) to complete two-dimensional rotation and realize the line-of-sight pointing adjustment.

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