Measurement information time synchronization method and system for optical axis pointing calibration of laser terminal

Abstract

The invention provides a measurement information time synchronization method and system for optical axis pointing calibration of a laser terminal. The method comprises the steps that S1, a spaceborne computer receives and caches collected measurement data with time codes; step S2, searching time-aligned satellite attitude data from the satellite attitude data to obtain aligned satellite attitude data; s3, performing recursion on the aligned satellite attitude data by using an attitude kinematics principle to obtain satellite attitude data after recursion; s4, searching the two-dimensional rotation angle data with time alignment from the two-dimensional rotation angle data of the laser terminal to obtain aligned two-dimensional rotation angle data; and S5, performing time synchronization on the aligned two-dimensional corner data through a weighted average interpolation method to obtain synchronized laser terminal optical axis pointing calibration data. According to the time information synchronization method provided by the invention, corresponding time synchronization strategies are designed according to different measurement data, and the reliability is good and the precision is high when the method is implemented on a satellite.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite overall design and attitude control, and in particular to a measurement information time synchronization method and system for laser terminal optical axis pointing calibration. Background Art

[0002] Since the beam angle of laser communication is extremely narrow, in order to ensure that the laser can accurately point to the communication target when establishing an inter-satellite link in orbit, strict requirements are placed on the optical axis pointing measurement accuracy of the laser terminal. The two-dimensional turntable is disturbed by factors such as installation errors, launch vibrations, and on-orbit stress release, which causes the laser terminal to have optical axis pointing deviations. In order to ensure the optical axis pointing accuracy of the laser terminal, a small star sensor is installed at the reference position of the laser terminal, and the optical axis pointing accuracy is calibrated by collecting small star sensor data, satellite attitude information, and two-dimensional rotation angle measurement information of the laser terminal. However, both the satellite platform and the laser terminal are in a highly dynamic operating state, and the above measurement information comes from different subsystems, which will cause the time information to be out of sync, thereby causing optical axis pointing calibration errors.

[0003] The optical axis pointing accuracy is the core indicator of the laser terminal. The communication beam angle of the laser terminal is very small, usually 10 -5 To ensure the laser can accurately point to the communication target and successfully establish communication, it is crucial to accurately measure the laser terminal's optical axis in inertial space. However, the two-dimensional turntable is affected by various factors such as installation errors, launch vibrations, and on-orbit stress release, which can cause the laser terminal's optical axis to deviate from its pointing direction.

[0004] To ensure the optical axis pointing accuracy of the laser terminal, a small star sensor is usually installed on the laser terminal's base. The optical axis pointing accuracy is calibrated by collecting small star sensor data, satellite attitude information, and two-dimensional rotation angle measurement information from the laser terminal. However, both the satellite platform and the laser terminal are in a highly dynamic state, and this measurement information comes from different subsystems. This leads to the problem of time information asynchrony, which ultimately causes optical axis pointing calibration errors. Therefore, in order to further improve the optical axis pointing accuracy of the laser terminal, it is extremely necessary to conduct research on the time synchronization method of the measurement information for the laser terminal's on-orbit optical axis pointing calibration.

[0005] A literature review revealed that the paper "Hermite Spline Curve Attitude Interpolation for Industrial Robots Based on Logarithmic Quaternions" (Journal of Northwestern Polytechnical University, Vol. 37, No. 6, 2019) proposes a method for mapping Cartesian space spline curves to quaternion space based on logarithmic quaternions to achieve smooth interpolation of quaternion multi-attitudes. The paper also elaborates on the multi-attitude interpolation method and steps of mapping Cartesian space Hermite spline curves to quaternion space with examples, verifying the rationality of the method. However, the paper mainly analyzes the interpolation method of satellite platform attitude and does not involve the attitude information time synchronization method based on angular velocity recursion.

[0006] In the paper "Design and Application of a High-Precision Time Synchronization Scheme for Hyperspectral Observation Satellites" (Journal of Naval Aviation University, Vol. 38, No. 3, 2023), a time synchronization scheme that can adapt to various precision requirements is designed to meet the high-precision time synchronization requirements of onboard hyperspectral cameras, full-spectrum spectral imagers, star sensors, and other time-sensitive instruments. However, this paper introduces a time-unified design method from the perspective of the time system and does not address the time synchronization method for measurement information.

[0007] A search of patent documents revealed an invention patent with publication number CN116400390A, which discloses a time synchronization method, apparatus, electronic device, and computer-readable storage medium. The method comprises: determining the internal time information of a processor based on a pulse signal from a satellite module and world time information; determining a time conversion relationship based on the internal time information and the world time information; and synchronizing the satellite module and the sensor module used for measurement based on the time conversion relationship. This application separately determines the internal time of the processor and the external world time, thereby determining the conversion relationship between the two times. This conversion relationship is then used to perform high-precision time synchronization for each module in the measurement system. This method effectively reduces the accumulated error of the high-precision clock within the processor, eliminating the need for additional hardware synchronization. This reduces the cost of time synchronization while enabling synchronized data acquisition across modules, improving the validity of measurement data. This patent primarily applies to visual measurement systems and does not address the time alignment and recursion of satellite attitude and laser terminal angle data.

[0008] In summary, in response to the above-mentioned problems of the existing technology, studying a measurement information time synchronization method and system for laser terminal optical axis pointing calibration has become a key task that needs to be solved urgently. Summary of the Invention

[0009] In view of the defects in the prior art, the purpose of the present invention is to provide a method and system for time synchronization of measurement information for optical axis pointing calibration of a laser terminal.

[0010] According to the present invention, a method for time synchronization of measurement information for optical axis pointing calibration of a laser terminal is provided, comprising the following steps:

[0011] Step S1: The onboard computer receives and caches the collected measurement data with time code, where the collected measurement data includes satellite attitude data, small star sensor measurement data, and two-dimensional rotation angle data of the laser terminal;

[0012] Step S2, using the small star sensor measurement data as a reference, searching for time-aligned satellite attitude data from the satellite attitude data to obtain aligned satellite attitude data;

[0013] Step S3, recursively deducing the aligned satellite attitude data using attitude kinematics principles to obtain recursively deduced satellite attitude data;

[0014] Step S4, using the measurement data of the small star sensor as a reference, searching for time-aligned two-dimensional rotation angle data from the two-dimensional rotation angle data of the laser terminal to obtain aligned two-dimensional rotation angle data;

[0015] Step S5: Based on the recursive satellite attitude data, the aligned two-dimensional rotation angle data is time synchronized by weighted average interpolation method to obtain synchronized laser terminal optical axis pointing calibration data.

[0016] Preferably, step S1 includes the following sub-steps:

[0017] Step S1.1, time synchronization reference selection: select the small star sensor measurement data as the time synchronization reference, control the recursion / interpolation time to no more than 0.1 seconds, and output the time synchronization reference signal;

[0018] Step S1.2, building cache information;

[0019] Step S1.3, determine the minimum cache quantity.

[0020] Preferably, step S1.2 includes:

[0021] For the small star sensor measurement data, the cache information includes the exposure time t of the small star sensor ss , the small star sensor measures the quaternion [q s0 q s1 q s2 q s3 ] and availability signs st ss ;

[0022] For satellite attitude data, the cache information includes the satellite attitude measurement time t i , satellite inertial attitude quaternion [q i0 q i1 q i2 q i3] and inertial angular velocity [ω x ω y ω z ] T ;

[0023] For laser terminal angle data, the cache information includes the laser terminal angle sampling time t l , the pitch axis angle α of the laser terminal l , the azimuth axis rotation angle β of the laser terminal l .

[0024] Preferably, step S1.3 includes:

[0025] For the small star sensor measurement data, cache the small star sensor measurement data of the current beat;

[0026] For satellite attitude data, the cache quantity is not less than count i , the calculation formula is as follows:

[0027]

[0028] Among them, T ss is the measurement period of the small star sensor, T i is the measurement period of satellite attitude,

[0029] For laser terminal angle data, the cache quantity is not less than count l , the calculation formula is as follows:

[0030]

[0031] Among them, T ss is the measurement period of the small star sensor, T l is the measurement period of the laser terminal rotation angle.

[0032] Preferably, step S2 includes the following sub-steps:

[0033] Step S2.1, small star sensor data validity determination: the availability flag st in the cache data of the small star sensor measurement data is ss Make a judgment. If it is determined to be available, record the exposure time of the latest cached small star sensor and compare it with the exposure time cached in the previous beat. When the difference between the two exposure times is greater than the cache threshold, the cached data is determined to be valid;

[0034] Step S2.2, posture information search.

[0035] Preferably, step S2.2 includes:

[0036] The current exposure time t in the small star sensor data ssand the satellite attitude measurement time buffer array t i Difference one by one, find the data with the smallest time difference, record the array number c corresponding to the data, and calculate the minimum time difference value Sat_deT:

[0037] Sat_deT=|t ss -t i [c]|

[0038] When the minimum time difference Sat_deT is less than the attitude information recursion threshold, the attitude information found is recorded from the satellite attitude data cache array:

[0039]

[0040] In the above formula, c is the number of the posture information array found, t i q is the satellite attitude measurement time buffer array, i0 The cache array of the first element of the satellite inertial attitude quaternion, q i1 The cache array of the second element of the satellite inertial attitude quaternion, q i2 The cache array of the third element of the satellite inertial attitude quaternion, q i3 is the cache array of the fourth element of the satellite inertial attitude quaternion, ω x is the cache array of the satellite's X-axis inertial angular velocity, ω y is the cache array of the satellite's Y-axis inertial angular velocity, ω z It is the cache array of the satellite's Z-axis inertial angular velocity;

[0041] When the minimum time difference Sat_deT is greater than the posture information recursive threshold, the current processing ends.

[0042] Preferably, step S3 includes the following sub-steps:

[0043] Step S3.1, construct the angular velocity matrix: the angular velocity matrix ω of the attitude recursion v For a 4×4 matrix, the expression is:

[0044]

[0045] Among them, satω x0 To find the satellite X-axis inertial angular velocity, satω y0 To find the satellite Y-axis inertial angular velocity, satω z0 To find the satellite's Z-axis inertial angular velocity;

[0046] Step S3.2, calculate the quaternion change rate: the quaternion change rate dq is a 4×1 vector, and the expression is:

[0047]

[0048] Among them, satq i0 is the recursive initial value of the first element of the satellite inertial attitude quaternion, satq i1 is the recursive initial value of the second element of the satellite inertial attitude quaternion, satq i2 is the recursive initial value of the third element of the satellite inertial attitude quaternion, satq i3 is the recursive initial value of the fourth element of the satellite inertial attitude quaternion;

[0049] Step S3.3, calculate the quaternion recursion result: the quaternion recursion result expression is:

[0050]

[0051] Among them, sq i0 is the recursive result of the satellite inertial attitude quaternion corresponding to the first element, sq i1 is the recursive result of the second element of the satellite inertial attitude quaternion, sq i2 is the recursive result of the satellite inertial attitude quaternion corresponding to the third element, sq i3 is the recursive result of the fourth element of the satellite inertial attitude quaternion, t ss is the exposure time of the current beat of the small star sensor, and satT0 is the initial value of the satellite attitude measurement time;

[0052] Step S3.4, normalize the recursively calculated quaternion. The expression is as follows:

[0053]

[0054] Among them, sq i It is the attitude information synchronized to the time base of the small star sensor.

[0055] Preferably, step S4 includes the following steps:

[0056] Step S4.1: The current exposure time t of the small star sensor is ss The laser terminal angle sampling time cache array t l Difference one by one, find the two sets of data with the smallest time difference, and record the corresponding array numbers j and k, and also record the time difference:

[0057] las_deTj=t ss -t l [j] abs_deTj=|t ss -t l [j]|

[0058] las_deTk=tss -t l [k] abs_deTk=|t ss -t l [k]|

[0059] Among them, las_deTj is the difference between the j-th sampling time of the laser terminal angle and the current exposure time of the small star sensor, and abs_deTj is the absolute value of the j-th time difference; las_deTk is the difference between the k-th sampling time of the laser terminal angle and the current exposure time of the small star sensor, and abs_deTk is the absolute value of the k-th time difference;

[0060] Step S4.2: When the time difference values ​​abs_deTk and abs_deTj are less than the recursive threshold value of the laser terminal angle information, the found laser terminal angle information is recorded:

[0061]

[0062] Among them, las_α j is the pitch axis angle of the jth beat, las_β j is the azimuth axis rotation angle of the jth beat, las_α k is the pitch axis angle of the kth beat, las_β k is the azimuth axis angle of the kth beat; when the time difference abs_deTk or abs_deTj is greater than the recursive threshold of the laser terminal angle information, the current processing is terminated.

[0063] Preferably, step S5 includes the following sub-steps:

[0064] Step S5.1: Calculate the weight based on the time difference between the two sets of laser terminal angle sampling data. The expression is as follows:

[0065]

[0066] Where deJ is the weight of the j-th beat sampling, deK is the weight of the k-th beat sampling, abs_deTj is the absolute value of the j-th time difference, and abs_deTk is the absolute value of the k-th time difference;

[0067] Step S5.2: Use the weighted average method to perform time synchronization processing on the two sets of laser terminal angle data. The expression is as follows:

[0068] α s =deJ·las_α j +deK·las_α k

[0069] β s =deJ·las_β j+deK·las_β k

[0070] Among them, deJ is the weight of the j-th beat sampling, deK is the weight of the k-th beat sampling, las_α j is the pitch axis angle of the jth beat, las_β j is the azimuth axis rotation angle of the jth beat, las_α k is the pitch axis angle of the kth beat, las_β k is the azimuth axis rotation angle of the kth beat, α s is the pitch angle time synchronization result, β s is the azimuth time synchronization result.

[0071] The present invention also provides a measurement information time synchronization system for laser terminal optical axis pointing calibration, comprising:

[0072] Module M1, the onboard computer receives and caches the collected measurement data with time code, which includes satellite attitude data, small star sensor measurement data and two-dimensional rotation angle data of the laser terminal;

[0073] Module M2, based on the measurement data of the small star sensor, searches for the time-aligned satellite attitude data from the satellite attitude data to obtain the aligned satellite attitude data;

[0074] Module M3 uses the attitude kinematics principle to recursively calculate the aligned satellite attitude data to obtain the recursive satellite attitude data;

[0075] Module M4, based on the measurement data of the small star sensor, searches for the time-aligned two-dimensional rotation angle data from the two-dimensional rotation angle data of the laser terminal to obtain the aligned two-dimensional rotation angle data;

[0076] Module M5, based on the recursive satellite attitude data, performs time synchronization on the aligned two-dimensional rotation angle data through the weighted average interpolation method to obtain the synchronized laser terminal optical axis pointing calibration data.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] 1. The time information synchronization method proposed in the present invention designs corresponding time synchronization strategies based on different measurement data, and has good reliability and high accuracy when implemented on board.

[0079] 2. The present invention can effectively solve the problem of time asynchrony of measurement information during the laser terminal optical axis pointing calibration process, and is of key significance to improving the laser terminal optical axis pointing accuracy.

[0080] 3. The measurement information time synchronization method for laser terminal optical axis pointing calibration proposed in the present invention can effectively solve the problem of measurement information time asynchrony among the onboard laser terminal two-dimensional turntable, satellite platform and small star sensor in a large dynamic environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0082] Figure 1 Schematic diagram of the measurement information time synchronization method for on-orbit optical axis pointing calibration of the laser terminal. DETAILED DESCRIPTION

[0083] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, without departing from the scope of the present invention, a number of variations and improvements may be made by those skilled in the art. These all fall within the scope of protection of the present invention.

[0084] Example 1:

[0085] Figure 1 Schematic diagram of the measurement information time synchronization method for on-orbit optical axis pointing calibration of the laser terminal.

[0086] like Figure 1 As shown, this embodiment provides a method for time synchronization of measurement information for optical axis pointing calibration of a laser terminal, including the following steps:

[0087] In step S1, the onboard computer receives and caches the collected measurement data with time code. In order to meet the calibration requirements of the on-orbit optical axis pointing of the laser terminal, the collected measurement data includes satellite attitude data, small star sensor measurement data and two-dimensional rotation angle data of the laser terminal.

[0088] Specifically, step S1 includes the following sub-steps:

[0089] Step S1.1, time synchronization reference selection.

[0090] In this embodiment, in order to improve the accuracy of data synchronization, it is generally required that the difference or recursion time is as short as possible, so it is necessary to select data with a low data update frequency as the time synchronization reference. Among the three measurement information of the laser terminal optical axis pointing: the principle of the two-dimensional rotation angle of the laser terminal is generally a code disk or an inductive synchronizer, and the measurement frequency is very high, generally reaching 50 to 100 Hz; the high-precision attitude measurement principle of the satellite platform usually adopts a star sensor and a gyroscope for joint attitude determination, and the measurement data of the high-bandwidth gyroscope can achieve a satellite attitude measurement frequency of 10 to 20 Hz; and according to the measurement principle of the small star sensor, when the small star sensor is used alone, the measurement frequency is about 1 Hz. According to the above analysis, the measurement and data transmission frequency of the small star sensor is the lowest, so the measurement data of the small star sensor is selected as the reference for time synchronization, and the recursion / interpolation time is controlled not to exceed 0.1 seconds (corresponding to 10 Hz sampling) to ensure the accuracy of time synchronization. On the contrary, the recursion / interpolation time may reach 1 second (corresponding to 1 Hz), and the time synchronization reference signal is output;

[0091] Step S1.2, build cache information.

[0092] Furthermore, step S1.2 includes:

[0093] For the small star sensor measurement data, the cache information includes the exposure time t of the small star sensor ss , the small star sensor measures the quaternion [q s0 q s1 q s2 q s3 ] and availability signs st ss , where the exposure time t ss It is the main reference data for time synchronization, and uses the acquisition time of multi-source information for recursion and difference; the small star sensor measures the quaternion [q s0 q s1 q s2 q s3 ] represents the conversion relationship between the inertial reference system and the small star sensor measurement coordinate system, which is the measurement information of the small star sensor; the small star sensor availability mark st ss It represents the availability of the small star sensor. Because the small star sensor is constrained by its layout in orbit, it may be affected by sunlight reflection and ground light, resulting in failure to measure normally. Therefore, it needs to be marked.

[0094] For satellite attitude data, the cache information includes the satellite attitude measurement time t i , satellite inertial attitude quaternion [q i0 q i1 q i2 q i3 ] and inertial angular velocity [ω x ω y ωz ] T Among the cached information of the satellite platform attitude, the inertial attitude quaternion of the satellite platform is selected for caching because the measurement data of the small star sensor is relative to the inertial reference system; at the same time, the inertial attitude angular velocity of the satellite platform is selected for quaternion recursion.

[0095] For laser terminal angle data, the cache information includes the laser terminal angle sampling time t l , the pitch axis angle α of the laser terminal l , the azimuth axis rotation angle β of the laser terminal l .

[0096] Step S1.3, determine the minimum cache quantity.

[0097] Furthermore, step S1.3 includes:

[0098] For the small star sensor measurement data, the small star sensor measurement data of the current beat is cached.

[0099] In this embodiment, the amount of data cache directly impacts the efficiency of time synchronization. Excessive data cache capacity can lead to excessive satellite cache resources and increase the computational complexity of the search. Excessive data cache capacity can lead to mismatches between multi-source measurement data, reducing matching accuracy. Therefore, the onboard cache capacity must be optimized based on the frequency and time delay characteristics of data transmission.

[0100] For the small star sensor, since the small star sensor is the benchmark for time synchronization, it is only necessary to cache the small star sensor data of the current beat.

[0101] For satellite attitude data, there is a beat delay according to the measurement data of the small star sensor, and the cache quantity is not less than count i , the calculation formula is as follows:

[0102]

[0103] Among them, T ss is the measurement period of the small star sensor, T i is the measurement period of the satellite attitude. In this embodiment, the number of cached satellite platform attitude information should be no less than 40 beats.

[0104] For the laser terminal angle data, there is a beat delay according to the measurement data of the small star sensor, and the cache quantity is not less than count l , the calculation formula is as follows:

[0105]

[0106] Among them, T ssis the measurement period of the small star sensor, T l is the measurement period of the laser terminal turning angle. In this embodiment, the cache quantity of the laser terminal turning angle information should be no less than 200 beats.

[0107] Step S2: Using the small star sensor measurement data as a reference, searching for time-aligned satellite attitude data from the satellite attitude data to obtain aligned satellite attitude data.

[0108] Specifically, step S2 includes the following sub-steps:

[0109] Step S2.1: To ensure the correctness of the time synchronization calculation, the validity of the small star sensor data is determined: the availability flag st in the cache data of the small star sensor measurement data is set. ss A determination is made, and only when the measurement data is valid will the next determination proceed. If the determination is valid, the latest cached small star sensor exposure time is recorded and compared with the exposure time cached in the previous tick. If the difference between the two exposure times is greater than a cache threshold, the cached data is considered valid. In this embodiment, the cache threshold is selected as half of the small star sensor measurement cycle.

[0110] Step S2.2, posture information search.

[0111] Each time the measurement data of the small star sensor is received, the satellite attitude information search and time synchronization are started.

[0112] Specifically, step S2.2 includes:

[0113] The current exposure time t in the small star sensor data ss and the satellite attitude measurement time buffer array t i Difference one by one, find the data with the smallest time difference, record the array number c corresponding to the data, and calculate the minimum time difference value Sat_deT:

[0114] Sat_deT=|t ss -t i [c]|

[0115] When the minimum time difference Sat_deT is less than the attitude information recursion threshold, the attitude information found is recorded from the satellite attitude data cache array:

[0116]

[0117] In the above formula, c is the number of the posture information array found, t i q is the satellite attitude measurement time buffer array, i0 The cache array of the first element of the satellite inertial attitude quaternion, q i1The cache array of the second element of the satellite inertial attitude quaternion, q i2 The cache array of the third element of the satellite inertial attitude quaternion, q i3 is the cache array of the fourth element of the satellite inertial attitude quaternion, ω x is the cache array of the satellite's X-axis inertial angular velocity, ω y is the cache array of the satellite's Y-axis inertial angular velocity, ω z A cache array of the satellite's Z-axis inertial angular velocity.

[0118] In this embodiment, the attitude information recursion threshold is related to the working mode of the satellite. To ensure the accuracy of attitude recursion, for agile maneuvering satellites, the attitude information recursion threshold is set to less than 0.2 seconds. For three-axis stabilized satellites, the attitude information recursion threshold is relaxed to more than 1 second.

[0119] When the minimum time difference Sat_deT is greater than the attitude information recursion threshold, it indicates that the time synchronization process has failed and the process ends.

[0120] Step S3: recursively infer the aligned satellite attitude data using attitude kinematics principles to obtain recursively inferred satellite attitude data.

[0121] Due to the large inertia of the satellite platform, its attitude changes are relatively slow compared with the rotation mechanism. Therefore, the attitude angular velocity information can be used to perform high-precision attitude recursion to achieve time synchronization between the satellite attitude information and the measurement information of the small star sensor.

[0122] Specifically, step S3 includes the following sub-steps:

[0123] Step S3.1, construct the angular velocity matrix: the angular velocity matrix ω of the attitude recursion v For a 4×4 matrix, the expression is:

[0124]

[0125] Among them, satω x0 To find the satellite X-axis inertial angular velocity, satω y0 To find the satellite Y-axis inertial angular velocity, satω z0 To find the satellite's Z-axis inertial angular velocity;

[0126] Step S3.2, calculate the quaternion change rate: the quaternion change rate dq is a 4×1 vector, and the expression is:

[0127]

[0128] Among them, satq i0 is the recursive initial value of the first element of the satellite inertial attitude quaternion, satqi1 is the recursive initial value of the second element of the satellite inertial attitude quaternion, satq i2 is the recursive initial value of the third element of the satellite inertial attitude quaternion, satq i3 is the recursive initial value of the fourth element of the satellite inertial attitude quaternion;

[0129] Step S3.3, calculate the quaternion recursion result: the quaternion recursion result expression is:

[0130]

[0131] Among them, sq i0 is the recursive result of the satellite inertial attitude quaternion corresponding to the first element, sq i1 is the recursive result of the second element of the satellite inertial attitude quaternion, sq i2 is the recursive result of the satellite inertial attitude quaternion corresponding to the third element, sq i3 is the recursive result of the fourth element of the satellite inertial attitude quaternion, t ss is the exposure time of the current beat of the small star sensor, and satT0 is the initial value of the satellite attitude measurement time;

[0132] Step S3.4, normalize the recursively calculated quaternion. The expression is as follows:

[0133]

[0134] Among them, sq i It is the attitude information synchronized to the time base of the small star sensor.

[0135] Step S4: Using the measurement data of the small star sensor as a reference, searching for time-aligned two-dimensional rotation angle data from the two-dimensional rotation angle data of the laser terminal to obtain aligned two-dimensional rotation angle data.

[0136] In this embodiment, the two-dimensional rotation angle data of the laser terminal is searched, and the two sets of data with the smallest time difference are first found. When the posture information time synchronization is successful, the laser terminal rotation angle information search phase is entered.

[0137] Specifically, step S4 includes the following steps:

[0138] Step S4.1: The current exposure time t of the small star sensor is ss The laser terminal angle sampling time cache array t l Difference one by one, find the two sets of data with the smallest time difference, and record the corresponding array numbers j and k, and also record the time difference:

[0139] las_deTj=t ss -t l[j] abs_deTj=|t ss -t l [j]|

[0140] las_deTk=t ss -t l [k] abs_deTk=|t ss -t l [k]|

[0141] Among them, las_deTj is the difference between the j-th sampling time of the laser terminal angle and the current exposure time of the small star sensor, and abs_deTj is the absolute value of the j-th time difference; las_deTk is the difference between the k-th sampling time of the laser terminal angle and the current exposure time of the small star sensor, and abs_deTk is the absolute value of the k-th time difference;

[0142] Step S4.2: When the time difference values ​​abs_deTk and abs_deTj are less than the recursive threshold value of the laser terminal angle information, the found laser terminal angle information is recorded:

[0143]

[0144] Among them, las_α j is the pitch axis angle of the jth beat, las_β j is the azimuth axis rotation angle of the jth beat, las_α k is the pitch axis angle of the kth beat, las_β k is the azimuth axis angle at the kth beat. In this embodiment, the laser terminal rotates quickly, so the laser terminal angle recursion threshold is recommended to be set to less than 0.1 seconds. If the time difference abs_deTk or abs_deTj is greater than the laser terminal angle recursion threshold, the time synchronization process fails and the process ends.

[0145] Step S5: Based on the recursive satellite attitude data, the aligned two-dimensional rotation angle data is time synchronized by weighted average interpolation method to obtain synchronized laser terminal optical axis pointing calibration data.

[0146] In this embodiment, a weighted average interpolation algorithm is used to synchronize the two-dimensional rotation angle of the laser terminal. The laser terminal rotates at a high speed on orbit, and it is difficult to ensure synchronization accuracy through angular velocity recursion. Based on the high frequency of laser terminal rotation angle acquisition, this patent uses a weighted average interpolation algorithm to synchronize the laser terminal's rotation angle information.

[0147] Specifically, step S5 includes the following sub-steps:

[0148] Step S5.1: Calculate the weight based on the time difference between the two sets of laser terminal angle sampling data. The expression is as follows:

[0149]

[0150] Where deJ is the weight of the j-th beat sampling, deK is the weight of the k-th beat sampling, abs_deTj is the absolute value of the j-th time difference, and abs_deTk is the absolute value of the k-th time difference;

[0151] Step S5.2: Use the weighted average method to perform time synchronization processing on the two sets of laser terminal angle data. The expression is as follows:

[0152] α s =deJ·las_α j +deK·las_α k

[0153] β s =deJ·las_β j +deK·las_β k

[0154] Among them, deJ is the weight of the j-th beat sampling, deK is the weight of the k-th beat sampling, las_α j is the pitch axis angle of the jth beat, las_β j is the azimuth axis rotation angle of the jth beat, las_α k is the pitch axis angle of the kth beat, las_β k is the azimuth axis rotation angle of the kth beat, α s is the pitch angle time synchronization result, β s is the azimuth time synchronization result.

[0155] Example 2:

[0156] The present invention also provides a measurement information time synchronization system for laser terminal optical axis pointing calibration. The measurement information time synchronization system for laser terminal optical axis pointing calibration can be implemented by executing the process steps of the measurement information time synchronization method for laser terminal optical axis pointing calibration. That is, those skilled in the art can understand the measurement information time synchronization method for laser terminal optical axis pointing calibration as a preferred implementation of the measurement information time synchronization system for laser terminal optical axis pointing calibration.

[0157] Specifically, the measurement information time synchronization system for the laser terminal optical axis pointing calibration includes:

[0158] Module M1, the onboard computer receives and caches the collected measurement data with time code, which includes satellite attitude data, small star sensor measurement data and two-dimensional rotation angle data of the laser terminal;

[0159] Module M2, based on the measurement data of the small star sensor, searches for the time-aligned satellite attitude data from the satellite attitude data to obtain the aligned satellite attitude data;

[0160] Module M3 uses the attitude kinematics principle to recursively calculate the aligned satellite attitude data to obtain the recursive satellite attitude data;

[0161] Module M4, based on the measurement data of the small star sensor, searches for the time-aligned two-dimensional rotation angle data from the two-dimensional rotation angle data of the laser terminal to obtain the aligned two-dimensional rotation angle data;

[0162] Module M5, based on the recursive satellite attitude data, performs time synchronization on the aligned two-dimensional rotation angle data through the weighted average interpolation method to obtain the synchronized laser terminal optical axis pointing calibration data.

[0163] Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, and units provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same functions of the system and its various devices, modules, and units provided by the present invention in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; the devices, modules, and units for implementing various functions can also be considered as both software modules implementing the method and structures within the hardware component.

[0164] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. A method for time synchronization of measurement information for laser terminal optical axis pointing calibration, characterized in that: The following steps are involved: Step S1, the onboard computer receives and caches the collected measurement data with time code, wherein the collected measurement data includes satellite attitude data, small star sensor measurement data and two-dimensional rotation angle data of the laser terminal; Step S2, using the small star sensor measurement data as a reference, searching for time-aligned satellite attitude data from the satellite attitude data to obtain aligned satellite attitude data; Step S3, recursively deducing the aligned satellite attitude data using attitude kinematics principles to obtain recursively deduced satellite attitude data; Step S4, using the measurement data of the small star sensor as a reference, searching for time-aligned two-dimensional rotation angle data from the two-dimensional rotation angle data of the laser terminal to obtain aligned two-dimensional rotation angle data; Step S5: Based on the recursively derived satellite attitude data, the aligned two-dimensional rotation angle data is time synchronized by a weighted average interpolation method to obtain synchronized laser terminal optical axis pointing calibration data.

2. The method for time synchronization of measurement information for laser terminal optical axis pointing calibration according to claim 1, characterized in that: The step S1 includes the following sub-steps: Step S1.1, time synchronization reference selection: select the measurement data of the small star sensor as the time synchronization reference, control the recursion / interpolation time to no more than 0.1 seconds, and output the time synchronization reference signal; Step S1.2, building cache information; Step S1.3, determine the minimum cache quantity.

3. The method for time synchronization of measurement information for optical axis pointing calibration of a laser terminal according to claim 2, characterized in that: The step S1.2 includes: For the small star sensor measurement data, the cache information includes the exposure time t of the small star sensor ss , the small star sensor measures the quaternion [q s0 q s1 q s2 q s3 ] and availability signs st ss ; For satellite attitude data, the cache information includes the satellite attitude measurement time t i , satellite inertial attitude quaternion [q i0 q i1 q i2 q i3 ] and inertial angular velocity [ω x ω y ω z ] T ; For laser terminal angle data, the cache information includes the laser terminal angle sampling time t l , the pitch axis angle α of the laser terminal l , the azimuth axis rotation angle β of the laser terminal l .

4. The method for time synchronization of measurement information for laser terminal optical axis pointing calibration according to claim 2, characterized in that: The step S1.3 includes: For the small star sensor measurement data, cache the small star sensor measurement data of the current beat; For the satellite attitude data, the cache quantity is not less than count i , the calculation formula is as follows: Among them, T ss is the measurement period of the small star sensor, T i is the measurement period of satellite attitude, For laser terminal angle data, the cache quantity is not less than count l , the calculation formula is as follows: Among them, T ss is the measurement period of the small star sensor, T l is the measurement period of the laser terminal rotation angle.

5. The measurement information time synchronization method for laser terminal optical axis pointing calibration according to claim 1 is characterized in that: The step S2 includes the following sub-steps: Step S2.1, small star sensor data validity determination: the availability flag st in the cache data of the small star sensor measurement data is ss Make a judgment. If it is determined to be available, record the exposure time of the latest cached small star sensor and compare it with the exposure time cached in the previous beat. When the difference between the two exposure times is greater than the cache threshold, the cached data is determined to be valid; Step S2.2, posture information search.

6. The measurement information time synchronization method for laser terminal optical axis pointing calibration according to claim 5 is characterized in that: The step S2.2 includes: The current exposure time t in the small star sensor data ss The satellite attitude measurement time buffer array t i Difference one by one, find the data with the smallest time difference, record the array number c corresponding to the data, and calculate the minimum time difference value Sat_deT: Sat_deT=|t ss -t i [c]| When the minimum time difference Sat_deT is less than the attitude information recursion threshold, the attitude information found is recorded from the satellite attitude data cache array: In the above formula, c is the number of the attitude information array found, t i q is the satellite attitude measurement time buffer array, i0 The cache array of the first element of the satellite inertial attitude quaternion, q i1 The cache array of the second element of the satellite inertial attitude quaternion, q i2 The cache array of the third element of the satellite inertial attitude quaternion, q i3 is the cache array of the fourth element of the satellite inertial attitude quaternion, ω x is the cache array of the satellite's X-axis inertial angular velocity, ω y is the cache array of the satellite's Y-axis inertial angular velocity, ω z It is the cache array of the satellite's Z-axis inertial angular velocity; When the minimum time difference Sat_deT is greater than the posture information recursive threshold, the current processing is terminated.

7. The measurement information time synchronization method for laser terminal optical axis pointing calibration according to claim 1 is characterized in that: The step S3 includes the following sub-steps: Step S3.1, construct angular velocity matrix: angular velocity matrix ω of attitude recursion v For a 4×4 matrix, the expression is: Among them, satω x0 To find the satellite X-axis inertial angular velocity, satω y0 To find the satellite Y-axis inertial angular velocity, satω z0 To find the satellite's Z-axis inertial angular velocity; Step S3.2, calculate the quaternion change rate: the quaternion change rate dq is a 4×1 vector, and the expression is: Among them, satq i0 is the recursive initial value of the first element of the satellite inertial attitude quaternion, satq i1 is the recursive initial value of the second element of the satellite inertial attitude quaternion, satq i2 is the recursive initial value of the third element of the satellite inertial attitude quaternion, satq i3 is the recursive initial value of the fourth element of the satellite inertial attitude quaternion; Step S3.3, calculate the quaternion recursion result: the quaternion recursion result expression is: Among them, sq i0 is the recursive result of the first element of the satellite inertial attitude quaternion, sq i1 is the recursive result of the second element of the satellite inertial attitude quaternion, sq i2 is the recursive result of the satellite inertial attitude quaternion corresponding to the third element, sq i3 is the recursive result of the fourth element of the satellite inertial attitude quaternion, t ss is the exposure time of the current beat of the small star sensor, and satT0 is the initial value of the satellite attitude measurement time; Step S3.4, normalize the recursively calculated quaternion. The expression is as follows: Among them, sq i It is the attitude information synchronized to the time base of the small star sensor.

8. The measurement information time synchronization method for laser terminal optical axis pointing calibration according to claim 1 is characterized in that: The step S4 comprises the following steps: Step S4.1: The current exposure time t of the small star sensor is ss The laser terminal angle sampling time cache array t l Difference one by one, find the two sets of data with the smallest time difference, and record the corresponding array numbers j and k, and also record the time difference: las_deTj=t ss -t l [j] abs_deTj=|t ss -t l [j]| las_deTk=t ss -t l [k] abs_deTk=|t ss -t l [k]| Among them, las_deTj is the difference between the j-th sampling time of the laser terminal angle and the current exposure time of the small star sensor, and abs_deTj is the absolute value of the j-th time difference; las_deTk is the difference between the k-th sampling time of the laser terminal angle and the current exposure time of the small star sensor, and abs_deTk is the absolute value of the k-th time difference; Step S4.2: When the time difference values ​​abs_deTk and abs_deTj are less than the recursive threshold value of the laser terminal angle information, the found laser terminal angle information is recorded: Among them, las_α j is the pitch axis angle of the jth beat, las_β j is the azimuth axis rotation angle of the jth beat, las_α k is the pitch axis angle of the kth beat, las_β k is the azimuth axis angle of the kth beat; when the time difference abs_deTk or abs_deTj is greater than the recursive threshold of the laser terminal angle information, the current processing is terminated.

9. The measurement information time synchronization method for laser terminal optical axis pointing calibration according to claim 1 is characterized in that: The step S5 includes the following sub-steps: Step S5.1: Calculate the weight based on the time difference between the two sets of laser terminal angle sampling data. The expression is as follows: Where deJ is the weight of the j-th beat sampling, deK is the weight of the k-th beat sampling, abs_deTj is the absolute value of the j-th time difference, and abs_deTk is the absolute value of the k-th time difference; Step S5.2: Use the weighted average method to perform time synchronization processing on the two sets of laser terminal angle data. The expression is as follows: α s =deJ·las_α j +deK·las_α k β s =deJ·las_β j +deK·las_β k Among them, deJ is the weight of the j-th beat sampling, deK is the weight of the k-th beat sampling, las_α j is the pitch axis angle of the jth beat, las_β j is the azimuth axis rotation angle of the jth beat, las_α k is the pitch axis angle of the kth beat, las_β k is the azimuth axis rotation angle of the kth beat, α s is the pitch angle time synchronization result, β s is the azimuth time synchronization result.

10. A measurement information time synchronization system for laser terminal optical axis pointing calibration, characterized in that: include: Module M1, the onboard computer receives and caches the collected measurement data with time code, the collected measurement data includes satellite attitude data, small star sensor measurement data and two-dimensional rotation angle data of the laser terminal; Module M2, based on the measurement data of the small star sensor, searches for time-aligned satellite attitude data from the satellite attitude data to obtain aligned satellite attitude data; Module M3, recursively deduces the aligned satellite attitude data using attitude kinematics principles to obtain recursively deduced satellite attitude data; Module M4, based on the measurement data of the small star sensor, searches for time-aligned two-dimensional rotation angle data from the two-dimensional rotation angle data of the laser terminal to obtain aligned two-dimensional rotation angle data; Module M5, based on the recursively derived satellite attitude data, performs time synchronization on the aligned two-dimensional rotation angle data by weighted average interpolation method to obtain synchronized laser terminal optical axis pointing calibration data.

Images