Method for determining initial direction of laser communication terminal and related equipment

Abstract

The invention relates to the technical field of laser communication, in particular to a method and related equipment for determining the initial direction of a laser communication terminal, and the method aims at the laser communication terminal on a captive balloon platform, obtains two antenna baseline vectors through a double-station GNSS receiver, and calculates a course angle through differential positioning; and meanwhile, attitude information is measured in real time by means of a platform inertial measurement unit, an initial pointing vector is calculated by combining the course angle and the attitude information, and an initial pointing angle containing an azimuth angle and a pitch angle is finally obtained. The method is suitable for the fields of emergency communication, military communication and scientific observation.

Description

Technical Field

[0001] The present invention relates to the field of laser communication technology, and particularly relates to a method for determining the initial pointing of a laser communication terminal and related devices. Background Art

[0002] With the rapid development of laser communication technology, it has shown great application potential and value in many fields such as emergency communication, military communication, and scientific observation. Laser communication has become an ideal choice for ultra-long-distance communication scenarios due to its significant advantages such as high transmission rate, strong anti-interference ability, and good concealment.

[0003] The tethered balloon platform has become an ideal carrier for laser communication due to its unique characteristics of long-term hovering in the air and large-scale coverage. However, when the tethered balloon platform is applied to high-altitude environments for laser communication, it faces many challenges that need to be solved urgently, especially in the aspects of initial pointing and rapid link establishment of laser communication.

[0004] The initial pointing of laser communication refers to the process of accurately aligning the laser beam at the transmitting end with the receiving end before the establishment of the laser communication link. However, the divergence angle of the laser beam in laser communication is extremely small, usually at the micro-radian level, which means that the initial pointing error will have a significant impact on the capture efficiency. Traditional initial pointing methods mainly rely on star observation or beacon light systems. Although star observation can provide relatively high pointing accuracy to a certain extent, this method is severely restricted by weather conditions. Once the weather is poor, such as cloud cover, the observation work cannot be carried out normally, thus affecting the accuracy and timeliness of the initial pointing. Although the beacon light system can also achieve relatively high pointing accuracy, it not only increases the complexity of the system but also increases the power consumption of the system, which is not conducive to the overall optimization and long-term stable operation of the system.

[0005] In addition, the tethered balloon platform is extremely vulnerable to external factors such as wind and temperature changes in high-altitude environments, resulting in unstable platform attitude. This instability further increases the difficulty of initial pointing, making traditional initial pointing methods face greater challenges in practical applications.

[0006] In terms of attitude measurement, existing methods such as single GNSS (Global Navigation Satellite System) or IMU (Inertial Measurement Unit) have obvious deficiencies in accuracy and stability in dynamic environments. Laser communication has extremely high requirements for pointing accuracy, and single GNSS or IMU is difficult to meet this high-precision requirement, resulting in relatively large initial pointing errors and affecting the normal link establishment of laser communication.

[0007] Meanwhile, traditional initial pointing methods usually require complex calibration processes, such as the calibration work involved in stellar observations or beacon light systems. These complex calibration processes result in a longer deployment time and are difficult to meet the requirements of timely communication in scenarios of emergency communication and those requiring quick responses, thus limiting the application effect and development prospects of laser communication on tethered balloon platforms. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for determining the initial pointing of a laser communication terminal and related devices in view of the deficiencies in the above-mentioned prior art, so as to solve the technical problem of low accuracy in determining the initial pointing of the laser communication terminal caused by the unstable attitude of the tethered balloon platform.

[0009] The object of the present invention is achieved by the following technical solutions: In a first aspect, the present invention provides a method for determining the initial pointing of a laser communication terminal, including: Using a dual-station GNSS receiver deployed on the laser communication terminal to obtain the baseline vector between two antennas, and calculating the heading angle of the laser communication terminal by means of differential positioning according to the baseline vector; the laser communication terminal is installed on a tethered balloon platform; Real-time measuring the attitude information of the tethered balloon platform through an inertial measurement unit arranged on the tethered balloon platform, and obtaining the attitude information of the laser communication terminal according to the attitude information; Calculating an initial pointing vector according to the heading angle and attitude information of the laser communication terminal, and obtaining the initial pointing angle of the laser communication terminal according to the initial pointing vector, where the initial pointing angle includes an azimuth angle and a pitch angle.

[0010] As a further improvement of the present invention, calculating the heading angle of the laser communication terminal by means of differential positioning according to the baseline vector specifically includes: The dual-station GNSS receiver synchronously obtains the WGS84 coordinates of two antennas; converting the WGS84 coordinates of the two antennas to the local-level coordinate system and calculating the baseline vector heading angle of the two antennas in the local-level coordinate system; Introducing a vehicle-mounted installation offset to correct the baseline vector heading angle: Using a Kalman filter to fuse multiple groups of differential observations to dynamically compensate the corrected baseline heading angle to obtain the heading angle of the laser communication terminal.

[0011] As a further improvement of the present invention, real-time measuring the attitude information of the tethered balloon platform through an inertial measurement unit arranged on the tethered balloon platform specifically includes: Obtaining angular velocity and acceleration data in real time according to the inertial measurement unit; Based on the angular velocity and acceleration data of the tethered balloon platform, the attitude information of the tethered balloon platform is obtained by combining the Kalman filtering algorithm. The attitude information includes pitch angle, roll angle, and yaw angle; Based on the attitude information of the tethered balloon platform and combined with the installation matrix between the tethered balloon platform and the laser communication terminal, the attitude information of the laser communication terminal is determined. The installation matrix is the relative installation position between the tethered balloon platform and the laser communication terminal.

[0012] As a further improvement of the present invention, the calculation formula of the installation matrix is:

[0013] In the formula, is the installation matrix, is the azimuth angle, representing the angle of rotation of the laser communication terminal around the Z-axis of the tethered balloon platform coordinate system; is the pitch angle, representing the angle of rotation of the laser communication terminal around the Y-axis of the tethered balloon platform coordinate system; is the roll angle, representing the angle of rotation of the laser communication terminal around the X-axis of the tethered balloon platform coordinate system; is the combined projection of the laser communication terminal on the horizontal and vertical planes; is the projection of the laser communication terminal on the horizontal and vertical planes, is the combined projection of the laser communication terminal in the vertical direction, is the projection of the laser communication terminal on the horizontal plane, is the projection of the laser communication terminal on the horizontal and vertical planes, is the combined projection of the laser communication terminal in the vertical direction, is the projection of the laser communication terminal in the vertical direction, is the combined projection of the laser communication terminal on the horizontal and vertical planes, is the combined projection of the laser communication terminal in the vertical direction, is the unit vector of the laser communication terminal in the X-axis direction of the tethered balloon platform coordinate system, is the unit vector of the laser communication terminal in the Y-axis direction of the tethered balloon platform coordinate system, is the unit vector of the laser communication terminal in the Z-axis direction of the tethered balloon platform coordinate system; in the tethered balloon platform coordinate system, the X-axis is defined as pointing to the heading direction of the tethered balloon platform; the Y-axis is defined as pointing to the right side of the tethered balloon platform; the Z-axis is defined as perpendicular to the plane of the tethered balloon platform and pointing downward.

[0014] As a further improvement of the present invention, the calculation formula of the attitude information of the laser communication terminal is:

[0015] In the formula, is the attitude information of the tethered balloon platform, is the installation matrix, is the attitude information of the laser communication terminal.

[0016] As a further improvement of the present invention, calculating an initial pointing vector according to the heading angle and attitude information of the laser communication terminal specifically includes: Obtaining the own GNSS information and the GNSS information of the other party in the dual-station GNSS receiver; Calculating the relative distance and azimuth angle between the two tethered balloon platforms according to the own GNSS information and the GNSS information of the other party, and obtaining a relative position vector according to the relative distance and azimuth angle between the two tethered balloon platforms; Converting the relative position vector to the laser communication terminal coordinate system with the laser communication terminal as the origin to obtain the initial pointing vector of the laser communication terminal; The X-axis in the laser communication terminal coordinate system is defined as pointing to the emission direction of the laser communication terminal; the Y-axis is defined as pointing to the right side of the laser communication terminal; the Z-axis is defined as perpendicular to the laser communication terminal plane and pointing downward.

[0017] As a further improvement of the present invention, obtaining the initial pointing angle of the laser communication terminal according to the initial pointing vector, and the calculation formula of the initial pointing angle is:

[0018]

[0019] In the formula, is the azimuth angle, is the x-axis component of the initial pointing vector, is the y-axis component of the initial pointing vector, is the z-axis component of the initial pointing vector, is the pitch angle, is the arctangent function.

[0020] As a further improvement of the present invention, after obtaining the initial pointing angle of the laser communication terminal, it further includes error correction of the initial pointing angle, specifically including: Taking the calculated initial pointing angle as a control command and inputting it into the turntable control system on the tethered balloon platform to control the turntable in the turntable control system to rotate to the target position; Real-time monitoring the position of the target tethered balloon platform, comparing the monitored position of the target tethered balloon platform with the initial pointing angle, and calculating the error between the current initial pointing angle and the target position; The error correction algorithm is adopted to correct the error of the initial pointing angle. When the error reaches the set threshold, the corrected command angle is used as the control command to control the turntable to rotate to the position of the target tethered balloon platform.

[0021] In a second aspect, the present invention provides a system for determining the initial pointing of a laser communication terminal, which is used to implement the method for determining the initial pointing of the laser communication terminal as described above, and includes: A dual-station GNSS receiver module, which is deployed on the laser communication terminal; the dual-station GNSS receiver module is used to obtain the baseline vector between two antennas, and calculate the heading angle of the laser communication terminal by using the differential positioning method according to the baseline vector; the laser communication terminal is installed on the tethered balloon platform; An inertial measurement unit, which is arranged on the tethered balloon platform; the inertial measurement unit measures the attitude information of the tethered balloon platform in real time, and obtains the attitude information of the laser communication terminal according to the attitude information; An initial pointing angle determination module, which calculates the initial pointing vector according to the heading angle and attitude information of the laser communication terminal, and obtains the initial pointing angle of the laser communication terminal according to the initial pointing vector, where the initial pointing angle includes the azimuth angle and the elevation angle.

[0022] In a third aspect, the present invention provides a computer-readable storage medium storing one or more programs, where the one or more programs include instructions that, when executed by a computing device, cause the computing device to execute the method for determining the initial pointing of the laser communication terminal as described above.

[0023] In a fourth aspect, the present invention provides a computing device, including: One or more processors, a memory, and one or more programs, where the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include instructions for executing the method for determining the initial pointing of the laser communication terminal as described above.

[0024] The beneficial effects of the present invention are as follows: The method for determining the initial pointing of the laser communication terminal provided by the present invention calculates the heading angle through a dual-station GNSS receiver using the baseline vector. Combining with differential positioning technology, it eliminates common errors and enables the positioning accuracy to reach the centimeter level, thereby providing a high-precision reference for heading angle calculation. At the same time, this embodiment takes into account the influence of the tethered balloon platform on the attitude of the laser communication terminal, measures the attitude of the tethered balloon platform through an inertial measurement unit, and then compensates for the attitude deviation of the laser communication terminal caused by the shaking or deformation of the tethered balloon platform, further improving the calculation accuracy of the pointing angle. The present invention integrates GNSS data information and inertial measurement unit data information, can provide stable reference data under complex meteorological conditions, ensure high precision and stability of the system in a dynamic environment, and at the same time, the calculated initial pointing accuracy can reach the sub-milliradian level, thereby significantly improving the establishment efficiency of the laser communication link. Brief Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic flowchart of the method for determining the initial pointing of the laser communication terminal in the embodiment of the present invention; Figure 2 It is a schematic diagram of the installation relationship between the tethered balloon and the laser terminal in the embodiment of the present invention; Figure 3 It is a schematic diagram of the relative position relationship between the own terminal and the other terminal in the embodiment of the present invention; Figure 4 It is a schematic diagram of the structure of the electronic device in the embodiment of the present invention; In the figure, 1 is the tethered balloon platform; 2 is the laser communication terminal; 21 is the dual-station GNSS receiver; 22 is the first receiving antenna; 23 is the second receiving antenna; 60 is the computer device; 61 is the processor; 62 is the memory; 63 is the computer program. Detailed Embodiments

[0027] In order to make the objectives and technical solutions of the present invention clearer and easier to understand. The following further details the present invention in combination with the drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] The following will clearly and completely describe the technical solutions of the present invention in combination with the drawings and specific embodiments. Among them, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0029] Example 1 As Figure 1 shown, this embodiment provides a method for determining the initial pointing of a laser communication terminal. This method combines dual-station GNSS and an inertial measurement unit to achieve rapid deployment and high-precision initial pointing, significantly shortening the establishment time of the laser communication link. The following are the specific implementation manners.

[0030] First, use the dual-station GNSS receiver 21 deployed on the laser communication terminal 2 to obtain the baseline vector between the two antennas, and calculate the heading angle of the laser communication terminal 2 according to the baseline vector using differential positioning; the laser communication terminal 2 is installed on the tethered balloon platform 1. The tethered balloon platform 1 in this embodiment includes a tethered balloon and a platform for carrying the laser communication terminal 2.

[0031] In this embodiment, a dual-station GNSS receiver 21 is installed on the body of the laser communication terminal 2, and the dual-station GNSS receiver 21 measures the baseline vector between the first receiving antenna 22 and the second receiving antenna 23. Among them, there is a certain installation distance and the distance is known between the two GNSS receiving antennas in this embodiment, and the GNSS antennas maintain a fixed relationship with the axis of the laser communication terminal 2. Calculate the heading angle of the laser communication terminal 2 based on the baseline vector and differential positioning technology. The differential positioning technology of dual-station GNSS can significantly improve the measurement accuracy of the heading angle, usually reaching within 0.1°. The two GNSS receivers are both deployed at two positions of the own terminal, and the connection direction of the two installed GNSS receivers is the terminal heading angle direction. The installation position spacing is greater than 1m.

[0032] The specific steps for obtaining the heading angle of the laser communication terminal 2 include: The dual-station GNSS receiver 21 synchronously obtains the WGS84 coordinates (World Geodetic System 1984, coordinates of the 1984 World Geodetic System) of the two antennas; Convert the WGS84 coordinates of the two antennas to the local-level coordinate system and calculate the baseline vector heading angle of the two antennas in the local-level coordinate system; Introduce the carrier installation offset to correct the baseline vector heading angle: Use a Kalman filter to fuse multiple groups of differential observations to dynamically compensate the corrected baseline heading angle to obtain the heading angle of the laser communication terminal 2.

[0033] Exemplarily, as Figure 2 shown, the dual-station GNSS receiver 21 synchronously obtains the WGS84 coordinates of antenna A and antenna B: among them, the coordinates of antenna A point: , the coordinates of antenna B point: ( ).

[0034] The WGS84 coordinates of the two antennas are converted to the local coordinate system. Specifically, the conversion formula is as follows:

[0035]

[0036]

[0037] In the formula, is the radius of curvature of the prime vertical, e is the eccentricity of the earth, is the coordinate difference in the x - direction of the local coordinate system caused by the longitude difference, is the latitude of antenna A, is the longitude of antenna A, is the ellipsoidal height of antenna A, W is the latitude of antenna B, is the longitude of antenna B, is the ellipsoidal height of antenna B, is the coordinate difference in the y - direction of the local coordinate system caused by the latitude difference, is the coordinate difference in the z - direction of the local coordinate system corresponding to the height difference. is to convert the latitude of antenna A into the x - direction component in the local coordinate system, is to convert the latitude of antenna A into the y - direction component in the local coordinate system.

[0038] Furthermore, the calculation expression for the heading angle of the baseline vector is:

[0039] In the formula, is the heading angle of the baseline vector. When , . When , .

[0040] After introducing the carrier installation offset correction, the calculation expression for the heading angle of the baseline vector is:

[0041] In the formula, is the corrected heading angle of the baseline vector, is the baseline vector and the theoretical installation deviation angle between the carrier longitudinal axis.

[0042] The Kalman filter is used to fuse multiple sets of differential observations and is iteratively updated by the following formula:

[0043] In the formula, is the state estimation value at the k-th moment, is the state estimation value at the (k - 1)-th moment, is the observation value at the k-th moment, is the observation matrix, is the Kalman gain at the k-th moment.

[0044] The bistatic GNSS receiver 21 refers to a cooperative working system composed of two GNSS (Global Navigation Satellite System, such as GPS (Global Positioning System), Beidou, GLONASS (Global Navigation Satellite System), Galileo (Galileo satellite navigation system), etc.) receivers, and the two receivers are respectively deployed at different positions.

[0045] Fuse the heading angle measured by the bistatic GNSS with the installation relationship of the laser communication terminal 2 to obtain the initial heading information of the laser communication terminal 2.

[0046] Specifically, first define the vehicle coordinate system and the GNSS baseline coordinate system. The vehicle coordinate system is defined with the centroid of the laser communication terminal 2 as the origin, the X-axis along the longitudinal axis of the vehicle (forward direction), the Y-axis perpendicular to the X-axis to the right, and the Z-axis perpendicular downward. The GNSS baseline coordinate system is defined by the connection direction of the two antennas (antenna A / antenna B), and the baseline vector is b AB =[Δx L , Δy L , Δz L T .

[0047] Then measure the installation offset angle, the heading installation offset angle Δψ: the fixed angle between the baseline vector and the vehicle X-axis (which needs to be obtained through a calibration experiment):

[0048] In the formula, is the horizontal component of the baseline vector in the vehicle coordinate system.

[0049] Therefore, the initial heading information of the laser communication terminal 2 can be obtained as:

[0050] Where, is the heading angle output in real time through bistatic GNSS differential positioning.

[0051] Secondly, the attitude information of the tethered balloon platform 1 is measured in real time by the inertial measurement unit set on the tethered balloon platform 1, and the attitude information of the laser communication terminal 2 is obtained according to the attitude information.

[0052] ​Specifically, by using the inertial measurement unit on the tethered balloon platform 1, the attitude information of the platform (including pitch angle, roll angle, and yaw angle) is measured in real time. The specific steps include: Obtain angular velocity and acceleration data in real time according to the inertial measurement unit; According to the angular velocity and acceleration data of the tethered balloon platform 1, combined with the Kalman filtering algorithm, solve the attitude information of the tethered balloon platform 1 in real time; According to the attitude information of the tethered balloon platform 1, combined with the installation matrix between the tethered balloon platform 1 and the laser communication terminal 2, determine the attitude information of the laser communication terminal 2.

[0053] In this embodiment, the installation matrix is the relative installation position between the tethered balloon platform 1 and the laser communication terminal 2. The installation matrix in this embodiment is calculated according to the installation angles. The installation angles include azimuth , pitch , roll in three directions. The coordinate system where the installation angles are located is the tethered balloon platform coordinate system.

[0054] Furthermore, the definition of the tethered balloon platform coordinate system is as follows: Taking the center of the tethered balloon platform 1 as the origin, the X-axis is defined as pointing forward of the tethered balloon platform 1 (i.e., the course direction); the Y-axis is defined as pointing to the right side of the tethered balloon platform 1; the Z-axis is defined as perpendicular to the plane of the tethered balloon platform 1 and pointing downward.

[0055] Then, the azimuth angle , pitch angle , roll angle in the installation angles are respectively defined as: The azimuth angle is the angle by which the laser communication terminal 2 rotates around the Z-axis of the tethered balloon platform coordinate system, indicating the deflection of the terminal in the horizontal plane; the pitch angle is the angle by which the laser communication terminal 2 rotates around the Y-axis of the tethered balloon platform coordinate system, indicating the up and down inclination of the terminal in the vertical plane; the roll angle is the angle by which the laser communication terminal 2 rotates around the X-axis of the tethered balloon platform coordinate system, indicating the rotation of the terminal around its own emission axis.

[0056] Furthermore, the calculation formula of the installation matrix is:

[0057] In the formula, is the installation matrix, and the installation matrix is a rotation matrix, is the azimuth angle, indicating the angle by which the laser communication terminal 2 rotates around the Z-axis of the tethered balloon platform coordinate system; is the pitch angle, indicating the angle by which the laser communication terminal 2 rotates around the Y-axis of the tethered balloon platform coordinate system; is the roll angle, indicating the angle by which the laser communication terminal 2 rotates around the X-axis of the tethered balloon platform coordinate system; is the combined projection of the laser communication terminal 2 on the horizontal and vertical planes; is the projection of the laser communication terminal 2 on the horizontal and vertical planes, is the combined projection of the laser communication terminal 2 in the vertical direction, is the projection of the laser communication terminal 2 on the horizontal plane, is the projection of the laser communication terminal 2 on the horizontal and vertical planes, is the combined projection of the laser communication terminal 2 in the vertical direction, is the projection of the laser communication terminal 2 in the vertical direction, is the combined projection of the laser communication terminal 2 on the horizontal and vertical planes, is the combined projection of the laser communication terminal 2 in the vertical direction, is the unit vector of the laser communication terminal 2 in the X-axis direction of the tethered balloon platform coordinate system, is the unit vector of the laser communication terminal 2 in the Y-axis direction of the tethered balloon platform coordinate system, is the unit vector of the laser communication terminal 2 in the Z-axis direction of the tethered balloon platform coordinate system; in the tethered balloon platform coordinate system, the X-axis is defined as pointing to the heading direction of the tethered balloon platform 1; the Y-axis is defined as pointing to the right side of the tethered balloon platform 1; the Z-axis is defined as perpendicular to the plane of the tethered balloon platform 1 and pointing downward.

[0058] Assume that the attitude of the laser communication terminal 2 in the laser communication terminal coordinate system is , then the calculation formula for the attitude information of the laser communication terminal 2 in the tethered balloon platform coordinate system is:

[0059] In the formula, is the attitude information of the tethered balloon platform 1, is the installation matrix, is the attitude information of the laser communication terminal 2.

[0060] Finally, according to the heading angle and attitude information of the laser communication terminal 2, the initial pointing vector is calculated, and the initial pointing angle of the laser communication terminal 2 is obtained according to the initial pointing vector, where the initial pointing angle includes the azimuth angle and the pitch angle. Specifically, the steps are as follows: Obtain the own GNSS information and the GNSS information of the other party in the dual-station GNSS receiver 21, and use the GNSS information of the other party as the target position.

[0061] The GNSS information in this embodiment is the position information obtained in the GNSS coordinate system, including latitude, longitude, and elevation.

[0062] Calculate the relative distance and azimuth angle between the two moored balloon platforms 1 based on the GNSS information of one's own side and the GNSS information of the other side, and obtain the relative position vector based on the relative distance and azimuth angle between the two moored balloon platforms 1.

[0063] The relative position vector in this embodiment is data in the geodetic coordinate system. For the convenience of subsequent calculations, this embodiment first converts the position data of both sides in the geodetic coordinate system to the geocentric rectangular coordinate system. The conversion formula is:

[0064] Among them,

[0065] In the formula, is the semi-major axis of the earth, is the eccentricity of the earth, is the latitude (in radians), is the longitude (in radians), is the elevation, P is the position vector of the laser communication terminal 2, x is the eastward distance of the data point on the earth's surface in the geocentric rectangular coordinate system, y is the northward distance of the data point on the earth's surface in the geocentric rectangular coordinate system, z is the height of the data point on the earth's surface in the geocentric rectangular coordinate system, N is the radius of curvature of the normal section arc, is the influence of latitude and longitude on the eastward distance, is the influence of latitude and longitude on the northward distance, is the correction term considering the shape of the earth's oblate spheroid.

[0066] Then, the relative position vector is:

[0067] Among them, is the relative position vector, is the position of the other terminal in the rectangular coordinate system, is the position of one's own terminal in the rectangular coordinate system.

[0068] Convert the relative position vector to the laser communication terminal coordinate system with the laser communication terminal 2 as the origin to obtain the initial pointing vector of the laser communication terminal 2.

[0069] In this embodiment, the X-axis in the laser communication terminal coordinate system is defined as pointing in the emission direction of the laser communication terminal 2; the Y-axis is defined as pointing to the right of the laser communication terminal 2; the Z-axis is defined as perpendicular to the plane of the laser communication terminal 2 and pointing downward.

[0070] The relative position vector in the laser communication terminal coordinate system is:

[0071] Among them,

[0072] In the formula, and are the rotation matrices around the Z-axis and Y-axis respectively, is the relative position vector in the coordinate system of the laser communication terminal.

[0073] Furthermore, based on the relative position vector in the coordinate system of the laser communication terminal, the initial pointing vector of the laser communication terminal 2 is calculated as follows:

[0074] Based on the initial pointing vector, the initial pointing angles are calculated, where the initial pointing angles include the azimuth initial pointing angle and the elevation initial pointing angle.

[0075] The azimuth initial pointing angle is:

[0076] The elevation initial pointing angle is:

[0077] In the formula, is the azimuth, with a range of , is the x-axis component of the initial pointing vector, is the y-axis component of the initial pointing vector, is the z-axis component of the initial pointing vector, is the elevation, with a range of , is the arctangent function.

[0078] After obtaining the initial pointing angles of the laser communication terminal 2, there are also steps to correct the errors of the initial pointing angles, specifically including: Taking the calculated initial pointing angles as control commands and inputting them into the turntable control system on the tethered balloon platform 1 to control the turntable in the turntable control system to rotate to the target position; among them, the turntable is mainly used to carry the laser communication terminal 2 and rotate, so that the laser can be incident on the target position, and thus communication can be achieved. The control accuracy of the turntable directly affects the accuracy of the initial pointing, so it is necessary to ensure that the control system of the turntable can accurately execute the input azimuth and elevation angles.

[0079] Real-time monitor the position of the target tethered balloon platform 1, compare the monitored position of the target tethered balloon platform 1 with the initial pointing angles, and calculate the error between the current initial pointing angles and the target position; The error correction algorithm is adopted to correct the error of the initial pointing angle, gradually reducing the error. When the error reaches the set threshold, the corrected command angle is used as the control command to control the turntable to rotate to the position of the tethered balloon platform 1 of the target. After the error reaches the acceptable range, the rapid establishment of the laser communication link is started. Through rapid scanning and fine tracking technologies, the stability and reliability of the laser communication link are ensured.

[0080] In this embodiment, the error correction algorithm can adopt the least squares method or the Kalman filtering method.

[0081] In summary, this embodiment does not require a complex star observation or beacon light system. Only by combining the dual-station GNSS and the inertial measurement unit, the initial pointing accuracy calculated can reach the sub-milliradian level, significantly improving the establishment efficiency of the laser communication link. This method can complete the initial pointing and link establishment in a short time and is applicable to emergency communication and rapid response scenarios. At the same time, the method can provide stable reference data under complex meteorological conditions to ensure the high precision and stability of the system in a dynamic environment.

[0082] Embodiment 2 A dual-station GNSS receiver 21 is installed on the laser communication terminal 2 body, and the heading angle is measured by differential positioning technology with an accuracy of 0.1°.

[0083] An inertial measurement unit is installed on the tethered balloon platform 1 to measure the attitude information (pitch angle, roll angle, heading angle) of the platform in real time.

[0084] In the carrier coordinate system, the origin is the centroid of the laser communication terminal 2, the X-axis is along the longitudinal axis of the carrier (forward direction), the Y-axis is perpendicular to the X-axis and to the right, and the Z-axis is perpendicular downward. The heading angle ψ is 0° to 360° (due north is up), the pitch angle θ is -90° to +90° (upward pitch is positive), and the roll angle φ is -180° to +180° (right roll is positive).

[0085] Combined with the installation relationship between the laser communication terminal 2 and the tethered balloon platform 1, the attitude of the laser communication terminal 2 is calculated.

[0086] In this embodiment, the own GPS information: . The other party's GPS information: . Based on the formula in Embodiment 1, the attitude vector of the laser communication terminal 2 is calculated as v = [0.1, 0.2, 0.3] T .

[0087] Furthermore, the relative position vector is calculated and the relative position vector in the platform coordinate system . The initial pointing vector is calculated .

[0088] Calculate the initial pointing angle of the laser communication terminal 2, where the azimuth angle and the elevation angle .

[0089] Input the initial pointing angle and into the turntable control system to control the turntable to rotate to the target position. Through the fast scanning and fine tracking systems, quickly establish the laser communication link. Through the error correction algorithm, correct the initial pointing angle and gradually reduce the error.

[0090] Embodiment 3 This embodiment provides a system for determining the initial pointing of a laser communication terminal, which is used to implement the method for determining the initial pointing of the laser communication terminal in Embodiment 1. This system specifically includes: A dual-station GNSS receiver module, deployed on the laser communication terminal 2; among them, the dual-station GNSS receiver 21 module is used to obtain the baseline vector between the two antennas, and calculate the heading angle of the laser communication terminal 2 by using the differential positioning method according to the baseline vector; the laser communication terminal 2 is installed on the tethered balloon platform 1; The specific steps for obtaining the heading angle of the laser communication terminal 2 include: The dual-station GNSS receiver 21 synchronously obtains the WGS84 coordinates (World Geodetic System 1984 coordinates) of the two antennas; Convert the WGS84 coordinates of the two antennas to the local tangent plane coordinate system and calculate the heading angle of the baseline vector of the two antennas in the local tangent plane coordinate system; Introduce the carrier installation offset to correct the baseline vector heading angle: Use a Kalman filter to fuse multiple groups of differential observations to dynamically compensate the corrected baseline heading angle to obtain the heading angle of the laser communication terminal 2.

[0091] Exemplarily, as Figure 2 shown, the dual-station GNSS receiver 21 synchronously obtains the WGS84 coordinates of antenna A and antenna B: among them, the coordinates of point A of antenna A: , and the coordinates of point B of antenna B: ( ).

[0092] Converting the WGS84 coordinates of the two antennas to the local tangent plane coordinate system, the specific conversion formula is:

[0093]

[0094]

[0095] In the formula, is the radius of curvature of the prime vertical circle, and e is the eccentricity of the Earth. is the coordinate difference in the x - direction of the local - level coordinate system caused by the longitude difference. is the latitude of antenna A. is the longitude of antenna A. is the ellipsoidal height of antenna A. W is the latitude of antenna B. is the longitude of antenna B. is the ellipsoidal height of antenna B. is the coordinate difference in the y - direction of the local - level coordinate system caused by the latitude difference. is the coordinate difference in the z - direction of the local - level coordinate system corresponding to the height difference. is to convert the latitude of antenna A into the x - direction component in the local - level coordinate system. is to convert the latitude of antenna A into the y - direction component in the local - level coordinate system.

[0096] Furthermore, the calculation expression for the heading angle of the baseline vector is:

[0097] In the formula, is the heading angle of the baseline vector. When , . When , .

[0098] After introducing the carrier - mounting bias correction, the calculation expression for the heading angle of the baseline vector is:

[0099] In the formula, is the corrected heading angle of the baseline vector, is the baseline vector and the theoretical mounting deviation angle between the carrier's longitudinal axis.

[0100] Using the Kalman filter to fuse multiple sets of differential observations, it is iteratively updated through the following formula:

[0101] In the formula, is the state estimate value at the k - th moment, is the state estimate value at the (k - 1)-th moment, is the observation value at the k - th moment, is the observation matrix, is the Kalman gain at the k - th moment.

[0102] A bistatic GNSS receiver 21 refers to a collaborative working system composed of two GNSS (Global Navigation Satellite System, such as GPS (Global Positioning System), Beidou, GLONASS (Global Navigation Satellite System), Galileo, etc.) receivers, and the two receivers are respectively deployed at different positions.

[0103] Fuse the heading angle measured by the bistatic GNSS with the installation relationship of the laser communication terminal 2 to obtain the initial heading information of the laser communication terminal 2.

[0104] Specifically, first define the vehicle coordinate system and the GNSS baseline coordinate system. The vehicle coordinate system is defined with the centroid of the laser communication terminal 2 as the origin, the X-axis along the longitudinal axis of the vehicle (forward direction), the Y-axis perpendicular to the X-axis and to the right, and the Z-axis perpendicular downward. The GNSS baseline coordinate system is defined by the connection direction of the two antennas (antenna A / antenna B), and the baseline vector is b AB =[Δx L ,Δy L ,Δz L T .

[0105] Then measure the installation offset angle, the heading installation offset angle Δψ: the fixed angle between the baseline vector and the vehicle X-axis (obtained through a calibration experiment):

[0106] In the formula, is the horizontal component of the baseline vector in the vehicle coordinate system.

[0107] Therefore, the initial heading information of the laser communication terminal 2 can be obtained as:

[0108] Among them, is the heading angle output in real time through bistatic GNSS differential positioning.

[0109] An inertial measurement unit is set on the tethered balloon platform 1; among them, the inertial measurement unit measures the attitude information of the tethered balloon platform 1 in real time, and obtains the attitude information of the laser communication terminal 2 according to the attitude information; Using the inertial measurement unit on the tethered balloon platform 1, measure the attitude information of the platform in real time (including pitch angle, roll angle, yaw angle), and the specific steps include: Obtain angular velocity and acceleration data in real time according to the inertial measurement unit; According to the angular velocity and acceleration data of the tethered balloon platform 1, combined with the Kalman filter algorithm, solve the attitude information of the tethered balloon platform 1 in real time; ​Based on the attitude information of the tethered balloon platform 1 and combined with the installation matrix between the tethered balloon platform 1 and the laser communication terminal 2, the attitude information of the laser communication terminal 2 is determined.

[0110] In this embodiment, the installation matrix is the relative installation position between the tethered balloon platform 1 and the laser communication terminal 2. The installation matrix in this embodiment is calculated based on the installation angles. The installation angles include the azimuth , pitch , and roll in three directions. The coordinate system where the installation angles are located is the tethered balloon platform coordinate system.

[0111] Furthermore, the definition of the tethered balloon platform coordinate system is as follows: taking the center of the tethered balloon platform 1 as the origin, the X-axis is defined as pointing forward of the tethered balloon platform 1 (i.e., the course direction); the Y-axis is defined as pointing to the right of the tethered balloon platform 1; the Z-axis is defined as perpendicular to the plane of the tethered balloon platform 1 and pointing downward.

[0112] Then, the azimuth angle , pitch angle , and roll angle in the installation angles are respectively defined as: the azimuth angle is the angle by which the laser communication terminal 2 rotates around the Z-axis of the tethered balloon platform coordinate system, indicating the deflection of the terminal in the horizontal plane; the pitch angle is the angle by which the laser communication terminal 2 rotates around the Y-axis of the tethered balloon platform coordinate system, indicating the up and down inclination of the terminal in the vertical plane; the roll angle is the angle by which the laser communication terminal 2 rotates around the X-axis of the tethered balloon platform coordinate system, indicating the rotation of the terminal around its own emission axis.

[0113] Furthermore, the calculation formula of the installation matrix is:

[0114] In the formula, is the installation matrix, and the installation matrix is a rotation matrix. is the azimuth angle, indicating the angle by which the laser communication terminal 2 rotates around the Z-axis of the tethered balloon platform coordinate system; is the pitch angle, indicating the angle by which the laser communication terminal 2 rotates around the Y-axis of the tethered balloon platform coordinate system; is the roll angle, indicating the angle by which the laser communication terminal 2 rotates around the X-axis of the tethered balloon platform coordinate system; is the combined projection of the laser communication terminal 2 on the horizontal and vertical planes; is the projection of the laser communication terminal 2 on the horizontal and vertical planes. is the combined projection of the laser communication terminal 2 in the vertical direction; is the projection of the laser communication terminal 2 on the horizontal plane; is the projection of the laser communication terminal 2 on the horizontal and vertical planes, is the combined projection of the laser communication terminal 2 in the vertical direction, is the projection of the laser communication terminal 2 in the vertical direction, is the combined projection of the laser communication terminal 2 on the horizontal and vertical planes, is the combined projection of the laser communication terminal 2 in the vertical direction, is the unit vector of the laser communication terminal 2 in the X-axis direction of the tethered balloon platform coordinate system, is the unit vector of the laser communication terminal 2 in the Y-axis direction of the tethered balloon platform coordinate system, is the unit vector of the laser communication terminal 2 in the Z-axis direction of the tethered balloon platform coordinate system; in the tethered balloon platform coordinate system, the X-axis is defined as pointing to the heading direction of the tethered balloon platform 1; the Y-axis is defined as pointing to the right side of the tethered balloon platform 1; the Z-axis is defined as perpendicular to the plane of the tethered balloon platform 1 and pointing downward.

[0115] Assume that the attitude of the laser communication terminal 2 in the laser communication terminal coordinate system is , then the calculation formula for the attitude information of the laser communication terminal 2 in the tethered balloon platform coordinate system is:

[0116] In the formula, is the attitude information of the tethered balloon platform 1, is the installation matrix, is the attitude information of the laser communication terminal 2.

[0117] The initial pointing angle determination module calculates the initial pointing vector according to the heading angle and attitude information of the laser communication terminal 2, and obtains the initial pointing angle of the laser communication terminal 2 according to the initial pointing vector. The initial pointing angle includes the azimuth angle and the pitch angle.

[0118] The initial pointing angle includes the azimuth angle and the pitch angle. Specifically, the steps are as follows: Obtain the own GNSS information and the GNSS information of the other party in the dual-station GNSS receiver 21, and use the GNSS information of the other party as the target position.

[0119] The GNSS information in this embodiment is the position information obtained in the GNSS coordinate system, including latitude, longitude, and elevation.

[0120] Calculate the relative distance and azimuth angle between the two tethered balloon platforms 1 according to the own GNSS information and the GNSS information of the other party, and obtain the relative position vector according to the relative distance and azimuth angle between the two tethered balloon platforms 1.

[0121] The relative position vector in this embodiment is data in the geodetic coordinate system. For the convenience of subsequent calculations, in this embodiment, the position data of both parties in the geodetic coordinate system is first converted to the geocentric rectangular coordinate system, and the conversion formula is:

[0122] Where,

[0123] In the formula, is the semi-major axis of the earth, is the eccentricity of the earth, is the latitude (in radians), is the longitude (in radians), is the elevation, P is the position vector of the laser communication terminal 2, x is the eastward distance of the data point on the earth's surface in the geocentric rectangular coordinate system, y is the northward distance of the data point on the earth's surface in the geocentric rectangular coordinate system, z is the height of the data point on the earth's surface in the geocentric rectangular coordinate system, N is the radius of curvature of the normal section arc, is the influence of latitude and longitude on the eastward distance, is the influence of latitude and longitude on the northward distance, is the correction term considering the shape of the earth's oblate spheroid.

[0124] Then, the relative position vector is:

[0125] Where, is the relative position vector, is the position of the other terminal in the rectangular coordinate system, is the position of one's own terminal in the rectangular coordinate system.

[0126] The relative position vector is converted to the laser communication terminal coordinate system with the laser communication terminal 2 as the origin to obtain the initial pointing vector of the laser communication terminal 2.

[0127] In this embodiment, the X-axis in the laser communication terminal coordinate system is defined as pointing in the emission direction of the laser communication terminal 2; the Y-axis is defined as pointing to the right of the laser communication terminal 2; the Z-axis is defined as perpendicular to the plane of the laser communication terminal 2 and pointing downward.

[0128] The relative position vector in the laser communication terminal coordinate system is:

[0129] Where,

[0130] In the formula, and Rotation matrices about the Z-axis and Y-axis respectively, is the relative position vector in the coordinate system of the laser communication terminal.

[0131] Furthermore, the initial pointing vector of the laser communication terminal 2 is calculated based on the relative position vector in the coordinate system of the laser communication terminal:

[0132] The initial pointing angle is calculated based on the initial pointing vector, where the initial pointing angle includes the azimuth initial pointing angle and the elevation initial pointing angle.

[0133] The azimuth initial pointing angle is:

[0134] The elevation initial pointing angle is:

[0135] In the formula, is the azimuth, and the range is , is the x-axis component of the initial pointing vector, is the y-axis component of the initial pointing vector, is the z-axis component of the initial pointing vector, is the elevation, and the range is , is the arctangent function.

[0136] After obtaining the initial pointing angle of the laser communication terminal 2, error correction of the initial pointing angle is also included, specifically including: Taking the calculated initial pointing angle as a control command and inputting it into the turntable control system on the tethered balloon platform 1 to control the turntable in the turntable control system to rotate to the target position; wherein, the turntable is mainly used to carry the laser communication terminal 2 and rotate, so that the laser can be incident on the target position, and thus communication can be achieved. The control accuracy of the turntable directly affects the accuracy of the initial pointing. Therefore, it is necessary to ensure that the control system of the turntable can accurately execute the input azimuth and elevation angles.

[0137] Real-time monitor the position of the target tethered balloon platform 1, compare the monitored position of the target tethered balloon platform 1 with the initial pointing angle, and calculate the error between the current initial pointing angle and the target position; The error correction algorithm is used to correct the error of the initial pointing angle and gradually reduce the error. When the error reaches the set threshold, the corrected command angle is used as the control command to control the turntable to rotate to the position of the tethered balloon platform 1 of the target. After the error reaches the acceptable range, the rapid establishment of the laser communication link is started. Through the rapid scanning and fine tracking technology, the stability and reliability of the laser communication link are ensured.

[0138] The error correction algorithm in this embodiment can adopt the least squares method or the Kalman filtering method.

[0139] In summary, this embodiment does not require a complex star observation or beacon light system. Only through the combination of dual-station GNSS and inertial measurement unit, the initial pointing accuracy calculated can reach the sub-milliradian level, significantly improving the establishment efficiency of the laser communication link. This method can complete the initial pointing and link establishment in a short time and is applicable to emergency communication and rapid response scenarios. At the same time, the method can provide stable reference data under complex meteorological conditions to ensure the high precision and stability of the system in a dynamic environment.

[0140] Embodiment 4 In another embodiment of the present invention, a computer-readable storage medium is provided, which is used as a storage component in the terminal device and its function is to store programs and data. It should be noted that the computer-readable storage medium here not only covers the built-in storage components of the terminal device, but also includes the extended storage components supported by the device. Its essence is a tangible medium that can contain or store programs, and these programs can be called by an instruction execution system, device or device, or operate in cooperation with them. This storage medium provides a storage area for the operating system of the terminal and stores one or more instructions suitable for the processor to load and run at the same time. These instructions can form one or more computer programs containing program codes.

[0141] Specifically, examples (non-exclusive list) of computer-readable storage media include: electrical connections with one or more wires, portable disks, hard disks, random access memories, read-only memories, erasable programmable read-only memories, optical fibers, portable compact disc read-only memories, optical storage devices, magnetic storage devices, or any reasonable combination of the above types.

[0142] The storage medium may also include a data signal propagated as part of a baseband or a carrier wave, which carries the readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any reasonable combination of the two. In addition, the computer-readable storage medium may also refer to other readable media other than the traditional readable storage media, which can send, propagate, or transmit programs for use or in cooperation with an instruction execution system, device, or component. The program code on the storage medium can be transmitted through any suitable medium, including but not limited to wireless, wired, optical cable, etc., or any reasonable combination thereof.

[0143] The program code for implementing the operations of the present invention can be written in any combination of one or more programming languages, including object-oriented programming languages such as Java and C++, as well as conventional procedural programming languages such as the "C" language. The execution modes of the program code include: running entirely on the user's computing device, running partially on the user's device and being an independent software package, running partially in a distributed manner on the user's device and a remote computing device, or running entirely on the remote computing device or server. When it comes to the remote computing device, the device can be connected to the user's computing device through any type of network such as a local area network or a wide area network, or connected to an external computing device through the Internet via an Internet service provider.

[0144] The processor is capable of loading and running one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the method for determining the initial pointing of the laser communication terminal described in Embodiment 1.

[0145] Embodiment 5 Referring to Figure 4 , another embodiment of the present invention provides a terminal device, specifically a computer device 60. This computer device 60 mainly consists of three parts, namely a processor 61, a memory 62, and a computer program 63 stored in the memory 62 and capable of running on the processor 61. Among them, the responsibility of the processor 61 is to execute the computer program to implement the method for determining the initial pointing of the laser communication terminal described in Embodiment 1. The memory 62 is used to store the computer program and other programs and data required for the operation of the device. When the computer program 63 runs on the processor 61, it can implement the method for determining the initial pointing of the laser communication terminal. To avoid repetition of content, relevant details are not elaborated here.

[0146] The computer device 60 has various different forms. It can be a desktop computer, a laptop computer, a handheld computer, or a computing device such as a cloud server.

[0147] The processor 61 can be a central processing unit or other types of general-purpose processors, central processors, graphics processors, digital signal processors, application-specific integrated circuits, field-programmable gate arrays, or other programmable logic devices, discrete gate or transistor logic devices, quantum-computing-based data processing logic units, discrete hardware components, etc. The general-purpose processor mentioned here refers to a microprocessor or any conventional processor.

[0148] The memory 62 can be either an internal storage unit of the computer device 60, such as the hard disk or memory of the computer device 60, or an external storage device of the computer device 60, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc. equipped with the computer device 60. The function of the memory 62 is not only to store computer programs but also to store other programs and data required for the operation of the device, and at the same time, it will also temporarily store the data that has been output or is about to be output.

[0149] In each of the embodiments provided by the present invention, the reference to a memory, database, or other medium will cover at least one of non-volatile memory and volatile memory. There are many types of non-volatile memory, including read-only memory, magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random-access memory, magnetoresistive random-access memory, ferroelectric memory, phase-change memory, graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. It should be noted that RAM has various forms, such as static random access memory or dynamic random access memory, etc.

Claims

1. A method for determining the initial pointing of a laser communication terminal, characterized in that, Including: Using a dual-station GNSS receiver deployed on a laser communication terminal to obtain the baseline vector between two antennas, and calculating the heading angle of the laser communication terminal by means of differential positioning according to the baseline vector; the laser communication terminal is installed on a tethered balloon platform; Real-time measuring the attitude information of the tethered balloon platform through an inertial measurement unit arranged on the tethered balloon platform, and obtaining the attitude information of the laser communication terminal according to the attitude information; Calculating an initial pointing vector according to the heading angle and attitude information of the laser communication terminal, and obtaining the initial pointing angle of the laser communication terminal according to the initial pointing vector, where the initial pointing angle includes an azimuth angle and a pitch angle.

2. The method for determining the initial pointing of a laser communication terminal according to claim 1, wherein Calculating the heading angle of the laser communication terminal by means of differential positioning according to the baseline vector, specifically including: The dual-station GNSS receiver synchronously obtains the WGS84 coordinates of two antennas; converting the WGS84 coordinates of the two antennas to the local-level coordinate system, and calculating the baseline vector heading angle of the two antennas in the local-level coordinate system; Introducing a vehicle-mounted installation offset to correct the baseline vector heading angle: Using a Kalman filter to fuse multiple groups of differential observations to dynamically compensate the corrected baseline heading angle to obtain the heading angle of the laser communication terminal.

3. The method for determining the initial pointing of the laser communication terminal according to claim 1, wherein Real-time measuring the attitude information of the tethered balloon platform through an inertial measurement unit arranged on the tethered balloon platform, specifically including: Obtaining angular velocity and acceleration data in real time according to the inertial measurement unit; Combining the angular velocity and acceleration data of the tethered balloon platform and using the Kalman filtering algorithm to obtain the attitude information of the tethered balloon platform, where the attitude information includes a pitch angle, a roll angle, and a yaw angle; Determining the attitude information of the laser communication terminal according to the attitude information of the tethered balloon platform and combining the installation matrix between the tethered balloon platform and the laser communication terminal, where the installation matrix is the relative installation position between the tethered balloon platform and the laser communication terminal.

4. The method for determining the initial pointing of a laser communication terminal according to claim 3, characterized in that, The calculation formula of the installation matrix is: Wherein, is the installation matrix, is the azimuth angle, representing the angle by which the laser communication terminal rotates about the Z-axis of the tethered balloon platform coordinate system; is the pitch angle, representing the angle by which the laser communication terminal rotates about the Y-axis of the tethered balloon platform coordinate system; is the roll angle, representing the angle by which the laser communication terminal rotates about the X-axis of the tethered balloon platform coordinate system; is the combined projection of the laser communication terminal on the horizontal and vertical planes; is the projection of the laser communication terminal on the horizontal and vertical planes, is the combined projection of the laser communication terminal in the vertical direction, is the projection of the laser communication terminal on the horizontal plane, is the projection of the laser communication terminal on the horizontal and vertical planes, is the combined projection of the laser communication terminal in the vertical direction, is the projection of the laser communication terminal in the vertical direction, is the combined projection of the laser communication terminal on the horizontal and vertical planes, is the combined projection of the laser communication terminal in the vertical direction, is the unit vector of the laser communication terminal in the X-axis direction of the tethered balloon platform coordinate system, is the unit vector of the laser communication terminal in the Y-axis direction of the tethered balloon platform coordinate system, is the unit vector of the laser communication terminal in the Z-axis direction of the tethered balloon platform coordinate system; in the tethered balloon platform coordinate system, the X-axis is defined as pointing in the heading direction of the tethered balloon platform; the Y-axis is defined as pointing to the right side of the tethered balloon platform; The Z-axis is defined as pointing downward perpendicular to the plane of the tethered balloon platform.

5. The method for determining the initial pointing of a laser communication terminal according to claim 4, wherein The calculation formula of the attitude information of the laser communication terminal is: In the formula, is the attitude information of the tethered balloon platform, is the installation matrix, is the attitude information of the laser communication terminal.

6. The method for determining the initial pointing of a laser communication terminal according to claim 1, characterized in that, Calculating the initial pointing vector according to the heading angle and attitude information of the laser communication terminal, specifically including: Obtaining the own GNSS information and the GNSS information of the other party in the dual-station GNSS receiver; Calculating the relative distance and azimuth angle between the two tethered balloon platforms according to the own GNSS information and the GNSS information of the other party, and obtaining a relative position vector according to the relative distance and azimuth angle between the two tethered balloon platforms; Converting the relative position vector to the laser communication terminal coordinate system with the laser communication terminal as the origin to obtain the initial pointing vector of the laser communication terminal; The X-axis in the laser communication terminal coordinate system is defined as pointing in the transmission direction of the laser communication terminal; the Y-axis is defined as pointing to the right side of the laser communication terminal; the Z-axis is defined as pointing downward perpendicular to the plane of the laser communication terminal.

7. The method for determining the initial pointing of a laser communication terminal according to claim 6, wherein The calculation formula of the initial pointing angle of the laser communication terminal is: In the formula, is the azimuth angle, is the x-axis component of the initial pointing vector, is the y-axis component of the initial pointing vector, is the z-axis component of the initial pointing vector, is the pitch angle, is the arctangent function.

8. The method for determining the initial pointing of a laser communication terminal according to claim 1, characterized in that, After obtaining the initial pointing angle of the laser communication terminal, it further includes error correction for the initial pointing angle, specifically including: Use the calculated initial pointing angle as a control command and input it into the turntable control system on the tethered balloon platform to control the turntable in the turntable control system to rotate to the target position; Real-time monitor the position of the target tethered balloon platform, compare the monitored position of the target tethered balloon platform with the initial pointing angle, and calculate the error between the current initial pointing angle and the target position; Adopt an error correction algorithm to correct the error of the initial pointing angle. When the error reaches the set threshold, use the corrected command angle as the control command to control the turntable to rotate to the position of the target tethered balloon platform.

9. A laser communication terminal initial pointing determination system for implementing the laser communication terminal initial pointing determination method according to any one of claims 1 to 8, characterized in that, Comprising: A dual-station GNSS receiver module deployed on the laser communication terminal; The dual-station GNSS receiver module is used to obtain the baseline vector between the two antennas, and calculate the heading angle of the laser communication terminal by using the differential positioning method according to the baseline vector; the laser communication terminal is installed on the tethered balloon platform; An inertial measurement unit is arranged on the tethered balloon platform; the inertial measurement unit measures the attitude information of the tethered balloon platform in real time, and obtains the attitude information of the laser communication terminal according to the attitude information; An initial pointing angle determination module calculates an initial pointing vector according to the heading angle and attitude information of the laser communication terminal, and obtains the initial pointing angle of the laser communication terminal according to the initial pointing vector, where the initial pointing angle includes an azimuth angle and a pitch angle.

10. A computing device, characterized in that, Comprising: One or more processors, a memory, and one or more programs, wherein the one or more programs are stored in the memory and configured to be executed by the one or more processors, and the one or more programs include a method for determining the initial pointing of the laser communication terminal according to any one of claims 1 to 8.

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