Unmanned aerial vehicle ground control station target positioning and plotting method

Abstract

The application relates to a target positioning and plotting method of a UAV ground control station, mainly comprising the following steps: (1) a target point screen is parallel to and proportional to a target point plane, and target point plane coordinates are calculated from target point screen coordinates according to a proportional relationship; (2) a laser ranging value is taken as an X-axis value, the X-axis value is added to the target point plane coordinates, and target point platform coordinates are obtained; (3) the target point platform coordinates are rotated to obtain target point aircraft coordinates; (4) the target point aircraft coordinates are rotated to obtain target point navigation vector coordinates; (5) a coordinate Z-axis component in the target point navigation vector coordinate system is a relative height value of the aircraft, so that target point navigation position coordinates are obtained; (6) the target point navigation position coordinates are rotated to obtain target point space geodetic rectangular coordinates; (7) the target point space geodetic rectangular coordinates are converted into target point geodetic coordinates; and (8) plotting and display of the target point geodetic coordinates are completed.

Description

Technical Field

[0001] This invention relates to a target positioning and mapping method for UAV ground control stations, and is particularly applicable to UAV system ground control stations equipped with visible light or infrared payload devices. Background Technology

[0002] The function of UAV reconnaissance target localization and mapping is to calculate the location of reconnaissance targets for the UAV's optoelectronic payload and plot it in two-dimensional digital map software, providing the payload operator with a visual impression during UAV flight. UAV reconnaissance area coordinate localization and mapping consists of two parts: target point coordinate localization and map plotting. The target point coordinate localization algorithm is based on the payload image target localization algorithm, while the map plotting method relies on the API interface of the military digital map platform and the Windows graphics device interface to complete the plotting and display of the target localization results. Summary of the Invention

[0003] The main functions of the payload image target localization and plotting method include target localization and plotting: target localization is used to calculate the geodetic coordinates (L, B, H) of any point on the payload image in real time; plotting is used to plot the target location onto a digital map in real time. The algorithm accuracy depends on the accuracy of measurement parameters, such as the GPS positioning accuracy of the aircraft and the angle measurement accuracy of the payload platform, and is also affected by system installation errors, such as payload platform installation errors. In medium-range high-speed applications, the target localization accuracy of visible light images is <80 meters, the target localization accuracy of infrared images is <50 meters, and the localization time is <1 second.

[0004] The target localization algorithm is based on the photogrammetric collinearity condition equation, meaning the image center, image point, and object point lie on a straight line. This algorithm is improved to address the characteristics of UAV payload shooting and the requirements of real-time localization as follows: the external azimuth angle elements of the spatial coordinate transformation are increased from 3 to 5, namely the 3 attitude angles of the aircraft and the 2 attitude angles of the payload platform, which together determine the aerial attitude of the image plane at the moment of shooting. More accurate laser ranging values ​​are used instead of the aircraft's relative altitude for coordinate localization. The algorithm steps can be roughly divided into three steps: first, calculate the coordinates of the image center point and obtain the aircraft's relative altitude; then, calculate the coordinates of any point based on the aircraft's relative altitude. Known values ​​for this method include: target image point screen pixel coordinates, sensor focal length, image pixel size, image screen display size, sensor pixel physical unit, photoelectric platform azimuth angle, pitch angle, laser ranging value, aircraft heading angle, pitch angle, roll angle, and aircraft geodetic coordinates; the solution value for this method is: the geodetic coordinates of the target point P.

[0005] The technical solution adopted in this invention is as follows:

[0006] (1) The target point screen is parallel and proportional to the target point plane. The target point plane coordinates are calculated from the target point screen coordinates based on the proportional relationship.

[0007] (2) Use the laser ranging value as the X-axis value, add the X-axis value to the target point plane coordinates, and obtain the target point platform coordinates;

[0008] (3) The target point platform coordinates are obtained by rotating the platform pitch angle along the Y-axis and rotating the platform azimuth angle along the Z-axis.

[0009] (4) Rotate the aircraft roll angle around the negative X-axis, then rotate the aircraft pitch angle around the negative Y-axis, and then rotate the aircraft heading angle around the negative Z-axis to obtain the target point navigation vector coordinates.

[0010] (5) The Z-axis component of the target point navigation vector coordinate system is the relative altitude of the aircraft, and the navigation position coordinates of the target point are obtained from this.

[0011] (6) Translate the target point navigation position coordinates to the origin of the spatial geodetic rectangular coordinates, rotate it negatively around the Y-axis by π / 2 - latitude, and rotate it around the Z-axis by π + longitude to obtain the spatial geodetic rectangular coordinates of the target point;

[0012] (7) Convert the spatial geodetic rectangular coordinates of the target point into the geodetic coordinates of the target point using a geodetic iterative algorithm;

[0013] (8) Based on the API interface of the military digital map platform and the Windows graphics device interface, the geodetic coordinates of the target point are plotted and displayed.

[0014] The advantages of this invention are as follows: Traditional photogrammetry generally uses a non-real-time and parameter inverse calculation mode to calculate object point coordinates. This involves first using the coordinates of multiple control points to inversely calculate the exterior orientation angle elements, image point and object point coordinate scaling factors (aircraft relative altitude), etc., and then using the calculated parameters to calculate the coordinates of any object point. This method is mature and highly accurate, but it cannot provide real-time positioning and requires a planar ground surface. Current UAV real-time positioning algorithms often assume the ground is parallel to the imaging plane, meaning the aircraft is directly above the target or takes multiple shots of the same target point at different attitudes, using spatial resection for positioning. These methods not only increase the difficulty and cost of reconnaissance but also negatively impact the battlefield survivability of UAVs. This algorithm uses the platform and aircraft attitude angles as exterior orientation elements and uses laser ranging values ​​to calculate the center point coordinates. It not only has real-time positioning capabilities but can also be used on any battlefield terrain. Furthermore, it can obtain the aircraft's relative altitude through laser ranging values, thus allowing the calculation of arbitrary object point coordinates even when the ground is assumed to be planar. Attached Figure Description

[0015] Figure 1This is a flowchart of the target positioning and plotting method for the UAV ground control station of the present invention; Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and actual embodiments. The target localization and mapping method for UAV ground control stations of the present invention mainly includes the following steps.

[0017] (1) Obtain the planar coordinates of the target point from the screen coordinates of the target point;

[0018] The platform coordinates of the target point can be calculated using the collinear equation of the three points: the camera center, the image point, and the object point. However, since the image plane is not necessarily parallel to the target ground, the absolute position of the target point cannot be obtained through the collinear equation; only the planar coordinates of the target point can be obtained.

[0019]

[0020] Wherein: S w S b This refers to the screen display size.

[0021] I w I h Image pixel size;

[0022] pixel is the size of a physical unit of pixels;

[0023] (2) Obtain the platform coordinates of the target point from the plane coordinates of the target point;

[0024] In this step, the absolute position of the image center point can be obtained using the laser ranging value. However, since the image plane is not parallel to the ground, the absolute position of any other point cannot be obtained through the collinearity equation. Therefore, only its vector coordinates can be obtained.

[0025] Transformation of target image point p from planar coordinates to three-dimensional coordinates (Xp, Yp, Zp):

[0026]

[0027] From collinear equations have to:

[0028]

[0029] Where: d is the laser ranging value

[0030] (3) Obtain the aircraft coordinates at the target point from the platform coordinates at the target point;

[0031] Rotate the aircraft coordinates along the ZV axis by azimuth angle Then rotate along the YV axis by the pitch angle ω to obtain the image coordinates. Invert the process to obtain the rotation matrix from platform coordinates to aircraft coordinates.

[0032]

[0033] Then the platform coordinates [x V y V , z V ] T =R V [x, y, z] T have to

[0034]

[0035] (4) Obtain the target point navigation vector coordinates from the target point aircraft coordinates;

[0036] The navigation coordinate system, like the coordinate systems mentioned above, is a relative coordinate system. The origin is located at the aircraft center, the Z-axis points towards the normal to the reference ellipsoid, and the X and Y axes point towards the tangents to the local meridians and parallels of latitude, respectively. To maintain consistency with the INS coordinate system, a right-handed Cartesian coordinate system with true north as the positive X-axis is adopted.

[0037] According to the definition in aviation standard ARINC 705, the attitude of the INS coordinate system within the navigation coordinate system is described by the heading angle, pitch angle, and roll angle. The heading angle, ψ, is the angle between the XV axis of the INS coordinate system and true north, with rightward deviation being positive. The pitch angle, θ, is the angle between the XV axis of the INS coordinate system and the horizontal line, with the positive XV axis pointing upwards being positive. The roll angle, φ, is the angle between the YV axis of the INS coordinate system and the horizontal line, with the positive YV axis pointing downwards being positive.

[0038] Rotating the aircraft coordinate system to the navigation coordinate system requires three rotations around a fixed axis:

[0039] √ Rotate INS around the XV axis by a roll angle φ;

[0040] √ Rotate around the negative YV axis by a pitch angle θ;

[0041] √ Rotate around the ZV axis in the negative direction by the heading angle ψ;

[0042] Therefore, the rotation matrix from the aircraft coordinate system to the navigation coordinate system is:

[0043]

[0044] Then [X] J y J , z J ] T =R VJ [X V y V , z V ] T

[0045] Note: Because the China Southern Airlines aircraft coordinate system differs from the aircraft coordinate system defined by Changguang in the above diagram, its Y-axis and Z-axis are opposite, resulting in an opposite definition of the roll angle. Therefore, the roll angle is a positive rotation in the rotation of the above coordinate system.

[0046] (5) Obtain the navigation position coordinates of the target point from the target point navigation vector coordinate system;

[0047] As defined by coordinates, the Z-axis component in the navigation coordinate system represents the aircraft's relative altitude. The relative altitude H of the aircraft can be obtained from the Z-axis component of the image center point's coordinates in the navigation coordinate system. From this, the absolute position coordinates of any point can be obtained.

[0048] Where: Z J =H

[0049] have to:

[0050] (6) Obtain the spatial rectangular coordinates of the target point from its navigation position coordinates;

[0051] Transformation matrix from navigation coordinates to spatial geodetic rectangular coordinates:

[0052]

[0053] Then [X] P Y P Z P ] T =R JP [X J Y J Z J ] T +[X A Y A Z A ] T

[0054] Where: [X] A Y A Z A ] T The coordinates are the aircraft's geodetic rectangular coordinates, which are obtained by converting the aircraft's geodetic coordinates (BA, LA, HA).

[0055] (7) Convert the spatial geodetic rectangular coordinates of the target point into the geodetic coordinates of the target point using a geodetic iterative algorithm;

[0056]

[0057]

[0058] The iterative method is used to find B and H, with the initial values ​​as follows:

[0059] N0 = a

[0060]

[0061] Iteration is performed according to the following formula:

[0062]

[0063] Until B i -B i-1 and H i -H i-1 Until the value is less than the required limit. Generally, if the accuracy of H is required to be 0.001m and the accuracy of B is required to be 0.00001″, it needs to be iterated 4 times.

[0064] (8) Based on the API interface of the military digital map platform and the Windows graphics device interface, the geodetic coordinates of the target point are plotted and displayed.

Claims

1. A method for target localization and plotting at a UAV ground control station, characterized in that... Includes the following steps: (1) The target point screen is parallel and proportional to the target point plane. The target point plane coordinates are calculated from the target point screen coordinates based on the proportional relationship. (2) Use the laser ranging value as the X-axis value, add the X-axis value to the target point plane coordinates, and obtain the target point platform coordinates; (3) The target point platform coordinates are obtained by rotating the platform pitch angle along the Y-axis and rotating the platform azimuth angle along the Z-axis. (4) The target point UAV coordinates are obtained by rotating the UAV roll angle around the negative X-axis, then rotating the UAV pitch angle around the negative Y-axis, and then rotating the UAV heading angle around the negative Z-axis. (5) The Z-axis component of the target point navigation vector coordinate system is the relative altitude value of the UAV, and the navigation position coordinates of the target point are obtained from this. (6) Translate the target point navigation position coordinates to the origin of the spatial geodetic rectangular coordinates, rotate it negatively around the Y-axis by π / 2 - latitude, and rotate it around the Z-axis by π + longitude to obtain the spatial geodetic rectangular coordinates of the target point; (7) Convert the spatial geodetic rectangular coordinates of the target point into the geodetic coordinates of the target point using a geodetic iterative algorithm; (8) Based on the API interface of the military digital map platform and the Windows graphics device interface, the geodetic coordinates of the target point are plotted and displayed.

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