High-precision dynamic pointing calibration method of laser communication system

Abstract

The invention discloses a high-precision dynamic pointing calibration method for a laser communication system, which not only has an online calibration function, but also has a dynamic pointing deviation pre-compensation function, and establishes a compensation reference value (initial calibration is taken as a reference) on the premise of completing the online calibration function. And the deviation value of each online calibration is compensated and corrected on the basis of the reference value. Through the above mode, the laser communication pointing system is successfully converted from a static tool needing manual intervention to a dynamic intelligent agent with self-learning and self-optimization capabilities, and the performance of the laser communication pointing system in a complex and long-distance application scene is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of laser communication technology, and more specifically to a high-precision dynamic pointing calibration method for laser communication systems. Background Technology

[0002] High-precision pointing is a key technology for realizing space laser communication (such as long-distance links between satellite and ground, air and air, air and ground). Currently, high-precision pointing utilizes a combined inertial navigation system to obtain the geographical coordinates and attitude of both ends, calculates the theoretical azimuth and pitch pointing angles through geometric calculations, controls the turntable pointing, and compensates for inherent installation and axis errors through a one-time near-field calibration. However, this method has significant limitations:

[0003] 1) Failure of the fixed bias model: Fixed azimuth and pitch biases calibrated in the near field (e.g., within a few kilometers) can lead to huge pointing deviations when applied to the far field at distances of tens or even hundreds of kilometers due to the arc length effect of the error angle. For example, an uncompensated error of 0.1° can cause a spot shift of about 174 meters at a distance of 100 kilometers, which is enough to cause acquisition and link establishment failure.

[0004] 2) Complex factors are difficult to model: Effects such as Earth's curvature and atmospheric refraction change dynamically with distance, altitude and meteorological conditions. It is extremely difficult to establish an accurate and complex offline error model that covers all working conditions, and it is not adaptable.

[0005] 3) Lack of online optimization capability: Once calibration is completed, the system cannot optimize the pointing accuracy based on the actual link status during subsequent communication. If performance degrades due to external interference (such as vibration or thermal deformation) or environmental changes, the system must interrupt communication and be manually calibrated again, which is inefficient and unreliable.

[0006] Therefore, there is an urgent need for a technology that can automatically and online perform pointing calibration and error compensation over the entire communication distance (from a few kilometers to hundreds of kilometers) to ensure the long-term stability and rapid recovery capability of the laser link. Summary of the Invention

[0007] The present invention aims to solve the problems existing in the pointing calibration methods of existing laser communication systems, and to provide a high-precision dynamic pointing calibration method for laser communication systems.

[0008] To solve the above problems, the present invention is achieved through the following technical solution:

[0009] A high-precision dynamic pointing calibration method for a laser communication system includes the following steps:

[0010] Step 1: At the initial test distance, the laser communication terminal calculates the theoretical azimuth and pitch pointing angle based on the latitude, longitude, altitude, and attitude information obtained by the combined inertial navigation unit. Based on the theoretical azimuth and pitch pointing angle at the initial test distance, the operator adjusts the direction of the azimuth and pitch turntable to make the pixel center coordinates of the visible light camera coincide with the mechanical center coordinates. At this time, the current pixel center coordinates of the visible light camera are defined as the tracking center pixel coordinates, and the azimuth and pitch deviation compensation amount at the initial test distance is recorded. The azimuth and pitch deviation compensation amount at the initial test distance is 0.

[0011] Step 2: Gradually increase the distance between the two laser communication terminals from the initial test distance to the final test distance, and perform the following operations at each current test distance:

[0012] Step 2.1: At the current test distance, the laser communication terminal calculates the current theoretical azimuth and pitch pointing angle based on the latitude, longitude, altitude, and attitude information obtained by the integrated inertial navigation unit;

[0013] Step 2.2: The laser communication terminal calculates the difference between the current pixel center coordinates of the visible light camera and the tracking center pixel coordinates to obtain the centroid difference, and converts the centroid difference into an azimuth pitch adjustment amount to adjust the direction of the azimuth pitch turntable. At this time, the current actual azimuth pitch angle of the azimuth pitch turntable is obtained.

[0014] Step 2.3: The laser communication terminal calculates the difference between the current actual azimuth elevation angle and the current theoretical azimuth elevation pointing angle to obtain the current azimuth elevation deviation.

[0015] Step 2.4: The laser communication terminal determines whether the current azimuth-elevation deviation exceeds the preset azimuth-elevation deviation threshold.

[0016] If the absolute value of the current azimuth pitch deviation exceeds the azimuth pitch deviation threshold, then record the azimuth pitch deviation compensation at the current test distance, and the azimuth pitch deviation compensation at the current test distance is equal to the sum of all current azimuth pitch deviations recorded from the initial test distance to the current test distance; otherwise, do not record.

[0017] Step 3: The laser communication terminal fits the azimuth and pitch deviation compensation amount at the test distance recorded from the initial test distance to the end test distance to obtain the azimuth and pitch error model.

[0018] Step 4: In the actual communication process, the laser communication terminal first calculates the theoretical azimuth and pitch pointing angle at the current communication distance based on the latitude, longitude, altitude, and attitude information obtained by the combined inertial navigation unit; then, based on the current communication distance, it queries the azimuth error model and pitch error model to obtain the azimuth and pitch deviation compensation amount at the current communication distance; finally, it controls the pointing of the azimuth and pitch turntable so that the actual azimuth and pitch angle of the azimuth and pitch turntable is equal to the sum of the theoretical azimuth and pitch pointing angle at the current communication distance and the azimuth and pitch deviation compensation amount at the current communication distance.

[0019] In step 2.4 above, if the absolute value of the current azimuth pitch deviation exceeds the azimuth pitch deviation threshold, or if the absolute value of the current azimuth pitch deviation exceeds the azimuth pitch deviation threshold, then the absolute value of the current azimuth pitch deviation is considered to exceed the azimuth pitch deviation threshold.

[0020] In step 3 above, when fitting the azimuth and pitch deviation compensation amount recorded from the initial test distance to the end test distance, a stepwise fitting method is adopted. In the early stage, a simple linear fitting is used, and in the later stage, it is upgraded to a higher-order polynomial or piecewise function fitting.

[0021] Theoretical azimuth θ a and theoretical pitch angle θ e The calculation formula is:

[0022]

[0023] In the formula, x b y b and z b Let be the three-dimensional position coordinates in the coordinate system of the peer laser communication terminal, where:

[0024]

[0025] In the formula, (X2,Y2,Z2) represents the position coordinates of the local laser communication terminal in the geocentric-geo-fixed coordinate system, and (X1,Y1,Z1) represents the position coordinates of the remote laser communication terminal in the geocentric-geo-fixed coordinate system. Represents the coordinate transformation matrix. Represents the attitude transformation matrix. Represents the installation matrix; where:

[0026]

[0027] In the formula, (L2,B2,H2) represents the latitude, longitude, and altitude of the local laser communication terminal, and (L1,B1,H1) represents the latitude, longitude, and altitude of the remote laser communication terminal; (θ)y ,θ p ,θ r ) represents the attitude data of the local laser communication terminal, namely the heading angle, pitch angle, and roll angle; (α,β,γ) represents the three-axis installation deviation angles between the local laser communication terminal coordinate system and the communication unit coordinate system.

[0028] Compared with the prior art, the present invention has the following characteristics:

[0029] 1. Adaptive and self-learning: The system no longer relies on one-time, fixed calibration, but learns and optimizes itself through continuous work, so that the pointing accuracy continues to improve as the communication process progresses.

[0030] 2. High precision across the entire range: By establishing a functional relationship between error and distance, the problem of large pointing deviations at different distances in the fixed deviation model, which leads to link establishment failure, is effectively solved, achieving high-precision pointing across the entire range from near field to far field.

[0031] 3. Strong robustness: It does not need to consider the influence of complex environmental factors such as the curvature of the earth and atmospheric refraction, and does not need to establish a complex physical model in advance. High-precision pointing can be completed based on distance and calibration dataset.

[0032] 4. High reliability and fast recovery: The dynamically updated error model ensures that after a link interruption, the system can match the optimal compensation parameters based on the nearest distance in the dataset for the most effective pointing, which greatly shortens the re-establishment time and improves the overall availability of the system. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a laser communication system.

[0034] Figure 2 This is a flowchart of a high-precision dynamic pointing calibration method for a laser communication system. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0036] See Figure 1This invention relates to a laser communication system comprising two laser communication terminals. Each laser communication terminal is mounted on two mobile platforms (such as vehicles or drones). The laser communication terminals utilize existing technologies, each including an azimuth / elevation turntable, an integrated laser transceiver communication unit, a visible light camera, a combined inertial navigation unit, and a control and processing unit. The azimuth / elevation turntable is mounted on the mobile platform, and its control is based on the deviation between the actual angle of the turntable and the target angle, driving the turntable to perform precise angle correction. The visible light camera and the communication unit are simultaneously mounted on the elevation turntable, with the line of sight of the visible light camera coaxial with the light-receiving axis of the communication unit to ensure calibration accuracy. The visible light camera tracks the target light spot and provides real-time feedback on its center position. The communication unit enables laser communication between the two laser communication terminals. The combined inertial navigation unit is rigidly connected to any position on the laser communication terminals to obtain the terminal's latitude, longitude, altitude (longitude, latitude, altitude) and attitude information (pitch angle, roll angle, heading angle). The control and processing unit is installed at any position in the laser communication terminal and is connected to the azimuth and elevation turntable, the communication unit, the visible light camera, and the integrated inertial navigation unit.

[0037] Considering that existing pointing calibration methods rely on the initial calibration parameters for subsequent pointing scans during actual communication, but lack a pointing deviation compensation model, the pointing accuracy based on a single calibration is difficult to guarantee at different communication distances, leading to a low acquisition probability for reconstructing communication interruptions. Therefore, this invention proposes a high-precision dynamic pointing calibration method for laser communication systems, comprising an initial testing phase and a subsequent communication phase, such as... Figure 2 As shown, the specific process is as follows:

[0038] I. Preliminary Testing Phase (Establishing a Dynamic Deviation Compensation Model):

[0039] (1) Test calibration process: The two laser communication terminals complete the calibration at the initial test distance L0.

[0040] Step 1.1: At the initial test distance L0, the laser communication terminal calculates the theoretical azimuth and pitch pointing angles based on the latitude, longitude, altitude, and attitude information obtained by the integrated inertial navigation unit.

[0041] The initial test distance L0 is the near-field distance, which is generally set to 1 to 5 kilometers.

[0042] The specific process of calculating the theoretical azimuth and elevation pointing angle by a laser communication terminal is as follows: First, the combined inertial navigation unit of the local laser communication terminal acquires its latitude, longitude, altitude, and attitude information, and transmits the latitude, longitude, and altitude information to the remote laser communication terminal via an auxiliary communication link. This auxiliary communication link refers to other communication links besides the laser communication link established by the communication units of the two laser communication terminals, such as data links or other wireless communication links. Then, the local laser communication terminal uses the remote latitude, longitude, and altitude information, as well as its own latitude, longitude, altitude, and attitude information, to calculate the theoretical azimuth and elevation pointing angle (θ) through coordinate calculation. a ,θ e (The theoretical azimuth angle θ) a and theoretical pitch angle θ e The calculation formula is:

[0043]

[0044] In the formula, x b y b and z b Let be the three-dimensional position coordinates in the coordinate system of the peer laser communication terminal, where:

[0045]

[0046] In the formula, (X2,Y2,Z2) represents the position coordinates of the local laser communication terminal in the geocentric-geo-fixed coordinate system, and (X1,Y1,Z1) represents the position coordinates of the remote laser communication terminal in the geocentric-geo-fixed coordinate system. Represents the coordinate transformation matrix. Represents the attitude transformation matrix. Represents the installation matrix; where:

[0047]

[0048] In the formula, (L2,B2,H2) represents the latitude, longitude, and altitude of the local laser communication terminal, and (L1,B1,H1) represents the latitude, longitude, and altitude of the remote laser communication terminal; (θ) y ,θ p ,θ r ) represents the attitude data of the local laser communication terminal, namely the heading angle, pitch angle, and roll angle; (α,β,γ) represents the three-axis installation deviation angles between the local laser communication terminal coordinate system and the communication unit coordinate system.

[0049] Step 1.2: Theoretical azimuth and pitch pointing angle of the operator at the initial test distance L0. Based on this, by visually observing the visible light camera, the center of the beacon laser emitted by the communication unit of the remote laser communication terminal is aligned with the center of the viewfinder of the visible light camera on the local laser communication terminal. This means aligning the pixel center coordinates of the visible light camera with the mechanical center coordinates, thereby adjusting the direction of the azimuth and tilt turntable. At this point, the local laser communication terminal has the maximum receiving power, and it records the current pixel center coordinates of the visible light camera as the tracking center pixel coordinates (u, v).

[0050] Step 1.3: The laser communication terminal records the azimuth and elevation deviation compensation amount at the initial test distance L0. At this point, the azimuth and pitch deviation compensation amount serves as the starting point for subsequent tracking, and its azimuth deviation compensation amount... pitch deviation compensation All are zero, that is

[0051] (2) Test tracking process: The two laser communication terminals gradually increase the distance from the initial test distance L0 to the set end test distance L. N Tracking was maintained throughout the entire pulling process.

[0052] Step 2.1, at the current test distance L i Below, the laser communication terminal calculates the current theoretical azimuth and pitch pointing angle based on the latitude, longitude, altitude, and attitude information obtained by the integrated inertial navigation unit.

[0053] Step 2.2: The laser communication terminal subtracts the current pixel center coordinates (x, y) of the visible light camera from the tracking center pixel coordinates (u, v) to obtain the centroid difference (xu, yv), and converts this centroid difference (xu, yv) into an azimuth-elevation adjustment amount to adjust the direction of the azimuth-elevation turntable. At this time, the laser communication terminal obtains the current actual azimuth-elevation angle of the azimuth-elevation turntable.

[0054] Step 2.3: The laser communication terminal will transmit the current actual azimuth and elevation angle. Compared with the current theoretical azimuth elevation angle The difference is calculated to obtain the current azimuth pitch deviation. in

[0055] Step 2.4: The laser communication terminal determines the azimuth and elevation deviation. Does it exceed the preset azimuth and pitch deviation threshold? in It is a constant value, and based on experience, it is usually taken as >0.6°.

[0056] If the absolute value of the azimuth deviation Exceeding the azimuth deviation threshold Or the absolute value of pitch deviation Exceeding the pitch deviation threshold Right now or When the time is right, record the current test distance L. i Azimuth and pitch deviation compensation At this point, the azimuth and pitch deviation compensation is the cumulative value of the aforementioned compensations, and its azimuth deviation compensation is... Pitch deviation compensation In the above, i = 1, 2, ..., n, where n is the distance from the initial test distance L0 to the current test distance L. i The distance points of all records.

[0057] Otherwise, do not record the current test distance L. i Azimuth and pitch deviation compensation

[0058] (3) Test modeling process: The two laser communication terminals use all recorded azimuth and pitch deviation compensation amounts to model the process.

[0059] Step 3.1: The laser communication terminal obtains the distance from the initial test distance L0 to the end test distance L. N The recorded azimuth and pitch deviation compensation amounts at various test distances are used to obtain the error compensation matrix:

[0060]

[0061] Step 3.2: The laser communication terminal fits the error compensation matrix to obtain the azimuth error model f and the elevation error model g.

[0062] To simplify the fitting process, the laser communication terminal employs a stepwise fitting method for the error compensation matrix. This means fitting is performed after a certain number of data points have been collected, rather than waiting until all data points have been acquired. Initially, a simple linear fitting, such as Δθ, can be used. a =f(D,θ) a ,…) and Δθ e =g(D,θ) eAs the number of data points increases, the model can be upgraded to a higher-order polynomial or piecewise function to capture more complex nonlinear relationships. That is, the azimuth error model f and pitch error model g can be functions obtained through linear regression, polynomial fitting, or machine learning algorithms. As tracking progresses, new effective calibration points are continuously added to the dataset, and the azimuth error model f and pitch error model g are periodically or triggered for refitting. This allows the error compensation capability to continuously evolve and optimize as the system operates for longer periods. This enables the system to be in a link-breaking state at different distances, and by obtaining the current distance between the two ends of the equipment, the most suitable compensation amount can be found. This invention treats each successful laser link establishment as an effective calibration opportunity, dynamically establishing and updating the functional relationship between pointing error and communication distance (and other relevant parameters), thereby achieving online, real-time error compensation based on the current communication state.

[0063] II. Later Communication Stage: In the actual communication process, the two laser communication terminals achieve high-precision pointing based on the azimuth error model f and elevation error model g constructed in the previous testing stage.

[0064] Step 4.1: The two laser communication terminals calculate the theoretical azimuth and pitch pointing angles at the current communication distance based on the latitude, longitude, altitude, and attitude information obtained by the combined inertial navigation unit.

[0065] Step 4.2: Based on the current communication distance, the two laser communication terminals query the azimuth error model f and the pitch error model g to obtain the azimuth and pitch deviation compensation amount under the current communication distance.

[0066] Step 4.3: The two laser communication terminals control the movement of the azimuth and pitch turntable based on the theoretical azimuth and pitch pointing angle at the current communication distance and the azimuth and pitch deviation compensation amount at the current communication distance, so that the actual azimuth and pitch angle is equal to the sum of the theoretical azimuth and pitch pointing angle at the current communication distance and the azimuth and pitch deviation compensation amount at the current communication distance.

[0067] This invention not only features online calibration but also dynamic pointing deviation pre-compensation. After completing online calibration, it creates a compensation benchmark (using the initial calibration as the benchmark) and compensates for each online calibration deviation based on this benchmark. Through this method, the invention successfully transforms the laser communication pointing system from a static tool requiring manual intervention into a dynamic intelligent agent with self-learning and self-optimization capabilities, significantly improving its performance in complex, long-distance application scenarios.

[0068] It should be noted that although the embodiments described above are illustrative, they are not intended to limit the invention. Therefore, the invention is not limited to the specific embodiments described above. Any other embodiments obtained by those skilled in the art under the guidance of this invention without departing from its principles are considered to be within the protection scope of this invention.

Claims

1. A high-precision dynamic pointing beacon calibration method for a laser communication system, characterized in that, The steps include the following: Step 1, at the initial test distance, the laser communication terminal calculates the theoretical azimuth-elevation pointing angle based on the latitude and longitude high information and the attitude information obtained by the combined inertial navigation unit; the operator adjusts the pointing of the azimuth-elevation turntable to make the pixel center coordinates of the visible light camera coincide with the mechanical center coordinates based on the theoretical azimuth-elevation pointing angle at the initial test distance, at this time, the current pixel center coordinates of the visible light camera are defined as the tracking center pixel coordinates, and the azimuth-elevation deviation compensation at the initial test distance is recorded, and the azimuth-elevation deviation compensation at the initial test distance is 0; Step 2, the distance between the two laser communication terminals is gradually increased from the initial test distance to the end test distance, and the following operations are performed at each current test distance: Step 2.1, at the current test distance, the laser communication terminal calculates the current theoretical azimuth-elevation pointing angle based on the latitude and longitude high information and the attitude information obtained by the combined inertial navigation unit; Step 2.2, the laser communication terminal obtains the centroid difference by subtracting the current pixel center coordinates of the visible light camera from the tracking center pixel coordinates, and converts the centroid difference into an azimuth-elevation adjustment amount to adjust the pointing of the azimuth-elevation turntable, at this time, the current actual azimuth-elevation angle of the azimuth-elevation turntable is obtained; Step 2.3, the laser communication terminal obtains the current azimuth-elevation deviation amount by subtracting the current actual azimuth-elevation angle from the current theoretical azimuth-elevation pointing angle; Step 2.4, the laser communication terminal judges whether the current azimuth-elevation deviation amount exceeds the preset azimuth-elevation deviation amount threshold: If the absolute value of the current azimuth-elevation deviation amount exceeds the azimuth-elevation deviation amount threshold, the azimuth-elevation deviation compensation at the current test distance is recorded, and the azimuth-elevation deviation compensation at the current test distance is equal to the cumulative value of all current azimuth-elevation deviation amounts recorded from the initial test distance to the current test distance; Otherwise, no record is made; Step 3, the laser communication terminal fits the azimuth-elevation deviation compensation at the test distance recorded from the initial test distance to the end test distance to obtain the azimuth-elevation error model; Step 4, in the actual communication process, the laser communication terminal first calculates the theoretical azimuth-elevation pointing angle at the current communication distance based on the latitude and longitude high information and the attitude information obtained by the combined inertial navigation unit; Then, based on the current communication distance, the azimuth error model and the elevation error model are queried to obtain the azimuth-elevation deviation compensation at the current communication distance; the pointing of the azimuth-elevation turntable is controlled so that the actual azimuth-elevation angle of the azimuth-elevation turntable is equal to the sum of the theoretical azimuth-elevation pointing angle at the current communication distance and the azimuth-elevation deviation compensation at the current communication distance.

2. The method of claim 1, wherein the method further comprises: determining a pointing error of the laser communication system; and adjusting the pointing error of the laser communication system. In step 2.4, the azimuth-elevation deviation amount is considered to exceed the azimuth-elevation deviation amount threshold if the absolute value of the current azimuth deviation amount of the current azimuth-elevation deviation amount exceeds the azimuth deviation amount threshold of the azimuth-elevation deviation amount threshold, or the absolute value of the current elevation deviation amount of the current azimuth-elevation deviation amount exceeds the elevation deviation amount threshold of the azimuth-elevation deviation amount threshold.

3. The method of claim 1, wherein the method further comprises: determining a pointing error of the laser communication system; and adjusting the pointing error of the laser communication system. In step 3, when fitting the azimuth-elevation deviation compensation quantity at the test distances recorded from the initial test distance to the end test distance, a step-by-step fitting method is adopted, and a simple linear fitting is used in the early stage, and a higher-order polynomial or a segmented function fitting is upgraded in the later stage.

4. The method of claim 1, wherein the method further comprises: determining a pointing error of the laser communication system; and adjusting the pointing error of the laser communication system. Theoretical azimuth angle θ a And the calculation formula of the theoretical pitch angle θ e is: where x b , y b , and z b are three-dimensional position coordinates in a coordinate system of the terminal at the other end of the laser communication, wherein: In the formula, (X2, Y2, Z2) represents the position coordinates of the local laser communication terminal in the geocentric and geostationary coordinate system, and (X1, Y1, Z1) represents the position coordinates of the opposite end laser communication terminal in the geocentric and geostationary coordinate system. represents a coordinate conversion matrix, represents a posture conversion matrix, represents a mounting matrix; wherein: In the formula, (L2, B2, H2) is the longitude, latitude and height data of the local laser communication terminal, (L1, B1, H1) is the longitude, latitude and height data of the opposite laser communication terminal; (θ y ,θ p ,θ r ) is the attitude data of the local laser communication terminal, i.e. the heading angle, the pitch angle and the roll angle; (α, β, γ) is the three-axis installation deviation angle of the local laser communication terminal coordinate system and the communication unit coordinate system.

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