Photoelectric positioning system for tethered drones without satellite navigation and ranging equipment

Abstract

The invention discloses an optoelectronic positioning system for a tethered unmanned aerial vehicle that does not rely on satellite navigation and ranging equipment. The system comprises: an airborne optical alignment device deployed on the tethered unmanned aerial vehicle, and a ground optical alignment device and a solution positioning module deployed on a ground control station; wherein the airborne optical alignment device comprises an airborne solid-state camera and an airborne laser target, and the ground optical alignment device comprises a ground solid-state camera and a ground laser target; the airborne optical alignment device is used to image the ground laser target through the airborne solid-state camera to obtain the coordinate value of the ground laser target on the target surface of the airborne solid-state camera; the ground optical alignment device is used to image the airborne laser target through the ground solid-state camera to obtain the coordinate value of the airborne laser target on the target surface of the ground solid-state camera; the solution positioning module is used to obtain the position information of the unmanned aerial vehicle by solving the above coordinate values ​​according to the optical geometric relationship, so as to realize positioning.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronic technology, and in particular relates to an optoelectronic positioning system for a tethered unmanned aerial vehicle that does not rely on satellite navigation and ranging equipment. Background Art

[0002] The tethered UAV system connects the UAV platform to the ground control station via a tethered cable. The ground control station transmits power and control instructions to the tethered UAV via the tethered cable. The tethered UAV transmits the acquired status, target location and other information to the ground control station via the tethered cable, thereby realizing functions such as target indication and ground weapon system attack guidance. It has the advantages of long hovering time, high UAV positioning accuracy, long detection distance and high detection accuracy.

[0003] The premise for the tethered UAV system to achieve functions such as high-precision target indication is that the tethered UAV platform itself has high positioning accuracy. At present, differential satellite navigation technology is mainly used to achieve high-precision positioning, especially RTK satellite navigation technology, which can achieve centimeter-level positioning accuracy for the platform and has become a widely used positioning technology for tethered UAV platforms.

[0004] Although differential satellite navigation technology has the advantages of wide application range and extremely high positioning accuracy, it still has many disadvantages that are difficult to overcome in actual use. For example, in densely built areas, GPS signals are easily blocked and reflected by buildings, resulting in the receiver being unable to receive signals or receiving multi-path reflected signals, affecting the real-time and accuracy of positioning; when the RTK base station cannot search for satellites or the data is disconnected, the system will switch to using ordinary single-point satellite navigation mode to provide ordinary positioning data and will no longer be able to maintain the positioning accuracy of the tethered drone; in addition, once the satellite navigation technology is interfered with, the entire system will not work. In summary, there is an urgent need to develop a tethered drone system that does not rely on satellite navigation technology to achieve precise navigation. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of tethered UAV systems using satellite navigation technology, and to propose a tethered UAV photoelectric positioning system that does not rely on satellite navigation and ranging equipment. The coordinate value, heading and pitch of the tethered UAV in the tethered platform coordinate system are accurately determined through photoelectric mutual aiming technology, thereby solving the problem that the UAV platform in previous tethered UAV systems can only rely on satellite navigation technology to achieve high-precision positioning.

[0006] In order to achieve the above-mentioned purpose, a tethered UAV optoelectronic positioning system that does not rely on satellite navigation and ranging equipment is provided, the system comprising: an airborne optical alignment device deployed on the tethered UAV and a ground optical alignment device and a solution positioning module deployed at a ground control station; wherein the airborne optical alignment device comprises an airborne solid-state camera and an airborne laser target, and the ground optical alignment device comprises a ground solid-state camera and a ground laser target;

[0007] The airborne optical alignment device is used to image the ground laser target through the airborne solid-state camera to obtain the coordinate value of the ground laser target on the target surface of the airborne solid-state camera;

[0008] The ground optical alignment device is used to image the airborne laser target through a ground solid-state camera to obtain the coordinate value of the airborne laser target on the target surface of the ground solid-state camera;

[0009] The calculation and positioning module is used to calculate the position information of the UAV from the above coordinate values ​​according to the optical geometric relationship, so as to achieve positioning.

[0010] As an improvement of the above system, the airborne solid-state camera adopts a CMOS or CCD sensor, and the ground solid-state camera adopts a CMOS or CCD sensor. The distance resolution of the airborne solid-state camera and the ground solid-state camera during normal operation is not less than a preset threshold.

[0011] As an improvement of the above system, the airborne laser target includes no less than two light sources, which are respectively installed on the left and right sides of the azimuth axis of the tethered UAV and are equidistant from the azimuth axis of the UAV. The connecting line of the two light sources passes through the geometric center of the tethered UAV, and the light sources are both pointed parallel to the optical axis direction of the airborne solid-state camera.

[0012] The ground laser target includes no less than two light sources, the line between the two light sources passes through the camera optical axis, and the perpendicular bisector of the line between the two light sources passes through the camera optical axis, the geometric center of the ground laser target coincides with the position of the optical axis of the ground solid-state camera, and the direction of the light source reference line is parallel to the optical axis direction of the ground solid-state camera.

[0013] As an improvement of the above system, the specific processing process of the solution positioning module is as follows:

[0014] Establish a coordinate system with the ground control station as the origin;

[0015] The horizontal coordinates m of the two light sources of the airborne laser target on the ground solid-state camera target surface p and n p ;

[0016] The ordinate k of the two light sources of the receiving airborne laser target on the ground solid-state camera target surface p and l p;

[0017] The horizontal coordinate m of the two light sources receiving the ground laser target on the target surface of the airborne solid-state camera d and n d ;

[0018] The ordinate k of the two light sources receiving the ground laser target on the target surface of the airborne solid-state camera d and l d ;

[0019] According to the horizontal axis m p and n p And the vertical coordinate k p and l p , the geometric center position of the airborne laser target deviates from the optical axis of the ground solid-state camera by α d-p and pitch β d-p ;

[0020] According to the horizontal axis m d and n d And the vertical coordinate k d and l d , the position of the geometric center of the ground laser target deviates from the optical axis of the airborne solid-state camera by α p-d and pitch β p-d ;

[0021] Combined with the roll υ output by the onboard inertial navigation device of the tethered UAV, the slant range R of the ground solid-state camera and the onboard solid-state camera is calculated;

[0022] According to the optical geometric relationship, the coordinates, heading and pitch of the tethered UAV are calculated from the azimuth, pitch and slant range.

[0023] As an improvement of the above system, the p and n p And the vertical coordinate k p and l p , the geometric center position of the airborne laser target deviates from the optical axis of the ground solid-state camera by α d-p and pitch β d-p ; Specifically include:

[0024] According to the horizontal axis m p and n p The horizontal coordinate x of the geometric center position of the airborne laser target on the ground solid-state camera target surface is calculated by the following formula: 0-p for:

[0025]

[0026] According to the following formula, the geometric center position of the airborne laser target deviates from the optical axis position of the ground solid-state camera by αd-p for:

[0027] α d-p =x 0-p ·Δθ p

[0028] Among them, Δθ p is the angular resolution of the ground-based solid-state camera, f p is the focal length of the ground solid-state camera, and the size of a single phase element of the ground solid-state camera is N p ×N p ;

[0029] According to the ordinate k p and l p The vertical coordinate y of the geometric center position of the airborne laser target on the ground solid-state camera target surface is calculated by the following formula: 0-p for:

[0030]

[0031] According to the following formula, the pitch β of the geometric center position of the airborne laser target from the optical axis of the ground solid-state camera is calculated: d-p for:

[0032] β d-p =y 0-p ·Δθ p .

[0033] As an improvement of the above system, the d and n d And the vertical coordinate k d and l d , the position of the geometric center of the ground laser target deviates from the optical axis of the airborne solid-state camera by α p-d and pitch β p-d ; Specifically include:

[0034] According to the horizontal axis m d and n d The horizontal coordinate x of the geometric center position of the ground laser target on the target surface of the airborne solid-state camera is calculated by the following formula: 0-d for:

[0035]

[0036] According to the following formula, the geometric center position of the ground laser target deviates from the optical axis position of the airborne solid-state camera by α p-d for:

[0037] α p-d =x 0-d ·Δθ d

[0038] Among them, Δθ d is the angular resolution of the onboard solid-state camera, f d is the focal length of the airborne solid-state camera, and the size of a single phase element of the airborne solid-state camera is N d ×N d ;

[0039] According to the ordinate k d and l d The ordinate y of the geometric center position of the ground laser target on the target surface of the airborne camera is calculated by the following formula: 0-d for:

[0040]

[0041] According to the following formula, the pitch β of the geometric center position of the ground laser target from the optical axis of the airborne solid-state camera is calculated: p-d for:

[0042] β p-d =y 0-d ·Δθ d .

[0043] As an improvement of the above system, the roll υ output by the airborne inertial navigation device of the tethered UAV is combined to calculate the slant distance R of the ground solid-state camera and the airborne solid-state camera; specifically:

[0044]

[0045] Among them, F(·) represents the p-d When and υ are known, the projection length of the distance ρ between the two light sources of the airborne laser target on the plane parallel to the target surface of the ground solid-state camera at the tethered UAV.

[0046] As an improvement of the above system, the coordinates, heading and pitch of the tethered UAV are calculated from the azimuth, pitch and slant range according to the optical geometric relationship; specifically including:

[0047] The coordinates of the tethered drone (x d ,y d ,z d )for:

[0048] x d =R·cos(β 0 +β d-p )·cos(α 0 +α d-p ′)

[0049] y d =R·cos(β 0+β d-p )·sin(α 0 +α d-p ′)

[0050] z d =R·sin(β 0 +β d-p )

[0051] Among them, α d-p ′ is the position of the geometric center of the airborne laser target relative to the ground solid-state camera, α 0 is the azimuth of the optical axis of the ground solid-state camera, β 0 is the pitch angle of the optical axis of the ground solid-state camera, β d-p is the pitch of the geometric center of the airborne laser target from the optical axis of the ground solid-state camera, and R is the slant distance between the ground solid-state camera and the airborne solid-state camera;

[0052] The heading of the tethered UAV relative to the ground control station α d for:

[0053] α d =360°-α p-d '

[0054] Among them, α p-d ' is the position of the geometric center of the ground laser target relative to the airborne solid-state camera;

[0055] Pitch β of tethered drone d for:

[0056] β d =-(-γ 0 -β p-d )

[0057] Among them, γ 0 The pitch of the optical axis of the airborne solid-state camera deviating from the baseline of the tethered drone, -90°≤β d ,β p-d ,γ 0 ≤90°, β d ,β p-d ,γ 0 Deviations from the horizontal plane upward are considered positive, and deviations from the horizontal plane downward are considered negative.

[0058] As an improvement of the above system, the ground optical alignment device also includes a ground reference platform for initializing and calibrating the optical axis pointing of the ground solid-state camera.

[0059] Compared with the prior art, the advantages of the present invention are:

[0060] 1. High-precision positioning is achieved without relying on satellite navigation technology. The present invention uses photoelectric mutual aiming technology to achieve high-precision positioning, heading and pitch of the tethered UAV relative to the tethered platform, avoiding many defects of using satellite navigation technology solutions, such as the inability to achieve full-time high-precision positioning, RTK base station signal interruption, and interference with satellite navigation equipment;

[0061] 2. It is less affected by environmental factors such as light intensity and foggy weather. It uses a high-definition solid-state camera with a laser target to achieve precise positioning, heading and pitch through air-to-ground mutual aiming. The laser target has extremely high visibility, which can ensure mutual aiming in strong light during the day, at night and under adverse weather conditions;

[0062] 3. The equipment has a simple structure and low cost. The key components are only two high-definition solid-state cameras and matching laser targets. There is no need to install distance measuring equipment. The equipment has a simple structure, low procurement cost, and is easy to install, debug and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is the overall block diagram of the photoelectric positioning system of the tethered UAV of the present invention that does not rely on satellite navigation and ranging equipment;

[0064] Figure 2 is a schematic diagram of an optical alignment device;

[0065] Figure 3 It is a schematic diagram of the working position of the tethered UAV system;

[0066] Figure 4 It is a schematic diagram of the laser target imaging principle;

[0067] Figure 5 It is a schematic diagram of the conversion relationship between the camera target surface azimuth and the real azimuth;

[0068] Figure 6 It is a schematic diagram of the geometric relationship of the airborne laser target projection;

[0069] Figure 7 This is a schematic diagram of the geometric relationship of the airborne laser target imaging on the ground solid-state camera;

[0070] Figure 8 It is a schematic diagram of pitch solution of tethered UAV;

[0071] Fig. 9 It is a schematic diagram of the installation of the airborne optical alignment device;

[0072] Fig.10 It is a schematic diagram of the accuracy with which the system can identify changes in the position of a tethered drone.

[0073] Reference numerals

[0074] 1. Tethered drone 2. Ground control station

[0075] 3. Airborne optical alignment device 4. Ground optical alignment device

[0076] 5. Ground power supply 6. Signal processing equipment

[0077] 7. Airborne solid-state camera 8. Airborne laser target

[0078] 9. Ground solid-state camera 10. Ground laser target

[0079] 11. Ground reference station 12. Mooring cable DETAILED DESCRIPTION

[0080] The present invention proposes an optoelectronic positioning system for a tethered UAV that does not rely on satellite navigation and ranging equipment. The system comprises: an airborne optical alignment device deployed on the tethered UAV and a ground optical alignment device and a solution positioning module deployed on a ground control station; wherein the airborne optical alignment device comprises an airborne solid-state camera and an airborne laser target, and the ground optical alignment device comprises a ground solid-state camera and a ground laser target;

[0081] The airborne optical alignment device is used to image the ground laser target through the airborne solid-state camera to obtain the coordinate value of the ground laser target on the target surface of the airborne solid-state camera;

[0082] The ground optical alignment device is used to image the airborne laser target through a ground solid-state camera to obtain the coordinate value of the airborne laser target on the target surface of the ground solid-state camera;

[0083] The calculation and positioning module is used to calculate the position information of the UAV from the above coordinate values ​​according to the optical geometric relationship, so as to achieve positioning.

[0084] This system uses high-definition solid-state cameras and laser targets installed on the tethered UAV and tethered platform respectively. The tethered UAV and the tethered platform aim at each other, that is, take pictures of each other, to determine the azimuth and pitch of the tethered UAV; the tethered platform observes the laser target carried by the tethered UAV to determine the slant distance between the tethered UAV and the tethered platform. The system calculates and outputs the coordinate value of the tethered UAV in the tethered platform coordinate system through the above information, determines the precise position of the tethered UAV relative to the tethered platform, and provides positioning data for the tethered UAV.

[0085] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0086] Example

[0087] like Figure 1As shown, an embodiment of the present invention proposes a tethered UAV photoelectric positioning system that does not rely on satellite navigation and ranging equipment, and the system includes: a tethered UAV 1, a ground control station 2, an airborne optical alignment device 3, a ground optical alignment device 4, a ground power supply 5, a signal processing device 6, and a tethered cable 12. The tethered UAV 1 is used to carry the airborne optical alignment device 3, and selects a UAV that meets the requirements according to the working requirements of the tethered UAV system, such as the type of mission to be performed, the weight of the load, etc.; the ground control station 2 is used as a carrier of the ground device; the ground power supply 5 is used to power the tethered UAV 1 platform and the load; the signal processing device 6 is used to analyze the angle, distance and other data obtained by the system; the tethered cable 12 is used to connect the tethered UAV 1 and the ground control station 2, transmit control instructions, angle, distance and other information, and transmit power to the tethered UAV 1.

[0088] like Figure 2 As shown, the airborne optical alignment device 3 includes: an airborne solid-state camera 7, which is used to aim at the ground laser target 10 and measure the azimuth α of the center position of the ground laser target 10 deviating from the optical axis direction of the airborne solid-state camera 7 p-d and pitch β p-d ; Airborne laser target 8, used for observation by ground solid-state camera 9.

[0089] The ground optical alignment device 4 includes: a ground solid-state camera 9, which is used to aim at the airborne laser target 8 and measure the position α of the center position of the airborne laser target 8 from the optical axis direction of the ground solid-state camera 9. d-p , pitch β d-p , and the slant distance R between the tethered UAV 1 and the ground control station; a ground laser target 10 for observation by the airborne solid-state camera 7; and a ground reference station 11 for initializing and calibrating the optical axis pointing of the ground solid-state camera 9.

[0090] The airborne solid-state camera 7 is a high-definition camera, and the camera sensor can be CMOS or CCD. The solution adopted in this example is used to replace the RTK satellite navigation technology to achieve accurate positioning of the tethered UAV 1, so the system positioning accuracy should not be less than the positioning accuracy of the RTK satellite navigation technology, that is, the distance resolution Δd between the airborne solid-state camera 7 and the ground solid-state camera 9 at the slant distance R should satisfy Δd| R ≤0.1m. In addition, it should be ensured that the airborne solid-state camera 7 and the ground solid-state camera 9 can easily achieve mutual aiming, that is, the opposite laser target should be able to easily enter the camera field of view, and the field of view of the solid-state camera at the slant distance R should be large enough. The camera resolution is H×V, the focal length is f, and the size of a single phase element is N×N. The angular resolution of this type of solid-state camera is

[0091]

[0092] Horizontal field of view

[0093] θ H =H·Δθ

[0094] Vertical field of view

[0095] θ V =V·Δθ

[0096] Similarly, the angular resolution of the ground solid-state camera can be calculated based on the relevant parameters of the ground solid-state camera.

[0097] The airborne laser target 8 is a device composed of several light sources, the light source can be a diode laser, and an optical lens is installed outside the laser to narrow the divergence angle of the laser. Figure 2 As shown, the airborne laser target 8 includes no less than two light sources. This example takes the case of two light sources as an example. The two light sources are installed on the left and right sides of the tethered UAV 1, respectively, and are equidistant from the azimuth axis of the UAV. The method in which the line connecting the two light sources passes through the geometric center of the tethered UAV 1 is the optimal solution, which can ensure that the spatial position of the light source is least affected by the posture change of the tethered UAV 1. When the light source is installed in other ways, attention should be paid to calibration compensation. When the two light sources are installed and calibrated, it should be ensured that the light source is pointed parallel to the optical axis direction of the airborne solid-state camera 7. In order to facilitate the ground solid-state camera 9 to observe the airborne laser target 8, the distance R is calculated by comparing the spacing ρ' of the image of the airborne laser target 8 on the target surface of the ground solid-state camera 9 and the actual spacing ρ of the two light sources on the aircraft. The spacing ρ of the two light sources should be large enough, but the installation position should also be considered comprehensively in combination with the actual conditions of the tethered UAV 1 such as the load and counterweight. In order to ensure that the image of the light source on the target surface of the ground solid-state camera 9 is less than 1 pixel, the light source size should meet d 0 ≤Δd| R To ensure that the solid-state camera can observe the light source facing the laser target within the field of view, the light source divergence angle should satisfy Ψ≥max(θ H ,θ V ). In addition, in order to ensure that the ground solid-state camera 9 can observe the light source of the laser target without being damaged due to excessive received light intensity, the laser target light source should be set with appropriate power.

[0098] The ground solid-state camera 9, with reference to the airborne solid-state camera 7, should keep the horizontal axis of the camera target surface horizontal during installation and calibration.

[0099] The ground laser target 10 is a device composed of a plurality of light sources. The ground laser target 10 includes at least two light sources. This example takes two light sources as an example. The line connecting the two light sources passes through the optical axis of the camera, and the perpendicular bisector of the line connecting the two light sources passes through the optical axis of the camera. Figure 2As shown, at this time, the geometric center of the ground laser target 10 coincides with the optical axis position of the ground solid-state camera 9, and the direction of the light source reference line should be parallel to the optical axis of the ground solid-state camera 9. In order to facilitate the airborne solid-state camera 7 to calculate the geometric center position of the ground laser target 10 by capturing the light source, the distance between the two light sources is 1 Dimension d of light source 0 It is better to be at least one order of magnitude larger, but it is not limited to be greater than one order of magnitude.

[0100] The specific processing process of the system includes the following steps:

[0101] Step 1: Establish a coordinate system with ground control station 2 as the origin.

[0102] like Figure 3 As shown, a coordinate system is established with the position of the ground laser target 10 as the origin, the coordinate origin is O, the xOy plane is the horizontal plane, and the y-axis is pointed to the relative due north of the coordinate system.

[0103] Step 2: The airborne solid-state camera 7 and the ground solid-state camera 9 aim at each other, and by identifying the laser target, the azimuth and pitch of the geometric center of the laser target deviating from the optical axis of the opposite camera are calculated.

[0104] The ground solid-state camera 9 captures the light source of the airborne laser target 8, and the imaging on the camera target surface is as follows: Figure 4 As shown in the figure, the horizontal coordinate values ​​of the two light sources on the target surface of the ground solid-state camera 9 are m and n respectively, then the horizontal coordinate value of the geometric center position of the airborne laser target 8 on the target surface of the ground solid-state camera 9 is

[0105]

[0106] In practical engineering applications, in order to reduce the error, the method of taking the average value of multiple measurements can be used. In this example, for the convenience of description, x 0 =(m+n) / 2. From this, the position of the geometric center of the airborne laser target 8 deviating from the optical axis of the ground solid-state camera 9 can be calculated.

[0107] α d-p =x 0 ·Δθ

[0108] like Figure 5 As shown, point A is the preset working position of the tethered drone 1, point B is the actual position of the tethered drone 1, A' and B' are the projections of point A and point B on the xOy plane, respectively, then ∠AOB=α d-p , ∠AOA′=∠BOB′=β 0 Assume AA'=BB'=h, OA=OB=R, and the orientation of the geometric center of the airborne laser target 8 relative to the ground solid-state camera 9 is ∠A'OB'=α d-p′, then the coordinates of point A are (0,h·tanβ 0 ,h), the coordinates of point B are (h·tanβ 0 ·sinα d-p ′,h·tanβ 0 ·cosα d-p ′,h). According to the geometric relationship of vectors, we have

[0109]

[0110] It can be deduced

[0111]

[0112] Similarly, the ordinate values ​​of the 2 light sources of the airborne laser target 8 on the target surface of the ground solid-state camera 9 are k and l respectively, so the ordinate of the geometric center position of the airborne laser target 8 on the target surface of the ground solid-state camera 9 is

[0113]

[0114] From this, the pitch of the geometric center position of the airborne laser target 8 from the optical axis of the ground solid-state camera 9 can be calculated.

[0115] β d-p =y 0 ·Δθ

[0116] The method for the airborne solid-state camera 7 to obtain the azimuth and pitch of the geometric center position of the ground laser target 10 deviating from the optical axis of the airborne solid-state camera 7 is consistent with the above description. Similarly, the azimuth α of the geometric center position of the ground laser target 10 deviating from the optical axis of the airborne solid-state camera 7 is measured. p-d , pitch β p-d .

[0117] Similarly, the geometric center position of the ground laser target 10 relative to the tethered drone 1

[0118]

[0119] Step 3: By comparing the distance between the images of the airborne laser target 8 on the target surface of the ground solid-state camera 9 and the actual distance between the two light sources on the aircraft, the distance R is calculated using the roll υ of the tethered drone 1 output by the airborne inertial navigation device.

[0120] The distance between the images of 82 light sources of the airborne laser target on the 9 target surfaces of the ground solid-state camera

[0121]

[0122] Similarly, in actual engineering applications, in order to reduce errors, the method of taking the average value of multiple measurements can be used.

[0123] like Figure 6 As shown, E is light source 1, H is light source 2, then EH = ρ, plane ξ is the horizontal plane where the tethered drone 1 is located, E' is the projection point of light source 1 on plane ξ, O is the position of the ground solid-state camera, OF is the direction of the optical axis of the ground solid-state camera 9, and a perpendicular line is drawn through point H to OF, intersecting OF at point P and OE at point K. At this time, HK⊥OF. p-d When and υ are known, the projection length ρ of ρ on the plane parallel to the target surface of the ground solid-state camera at the tethered UAV is 0 =HK is expressed as

[0124] ρ 0 =F(ρ,α p-d ,υ)

[0125] like Figure 7 As shown, according to the optical geometric relationship, we have

[0126]

[0127] Available

[0128]

[0129] Step 4: Calculate the position, heading and pitch of the tethered UAV 1 relative to the ground control station 2 by using the acquired distance, azimuth and pitch information.

[0130] Depend on Figure 3 The geometric relationship shown, the x coordinate of the tethered drone 1

[0131] x d =R·cos(β 0 +β d-p )·cos(α 0 +α d-p ′)

[0132] The y coordinate of tethered drone 1

[0133] y d =R·cos(β 0 +β d-p )·sin(α 0 +α d-p ′)

[0134] The z coordinate of tethered drone 1

[0135] z d =R·sin(β 0 +β d-p )

[0136] The heading of the tethered UAV 1 relative to the ground control station 2

[0137] α d=360°-α p-d '

[0138] like Figure 8 As shown, the pitch of the tethered drone 1

[0139] β d =-(-γ 0 -β p-d )

[0140] where γ 0 is the pitch of the optical axis of the airborne solid-state camera 7 from the baseline of the tethered drone 1, -90°≤β d ,β p-d ,γ 0 ≤90°, β d ,β p-d ,γ 0 Deviations from the horizontal plane upward are considered positive, and deviations from the horizontal plane downward are considered negative.

[0141] The system configuration steps are as follows:

[0142] Step 1: Select tethered drone 1 and preset the relative coordinates of the working position of tethered drone 1

[0143] Select a suitable drone according to the mission requirements and preset the working position of the tethered drone 1. The working position of the tethered drone 1 is A, and the projection point of point A on the xOy plane is B. In this example, AB is preset to 200m. For the convenience of calculation, OB is set to 200m. Then

[0144] Step 2: Determine the specifications of the solid-state camera and laser target

[0145] Select two solid-state cameras with a resolution of H×V=1920×1080, a focal length of f=135mm, and a single phase element size of N×N=4×4μm. Then the angular resolution of this type of solid-state camera is

[0146]

[0147] Horizontal field of view

[0148] θ H =H·Δθ=1920×0.0296mrad≈3.256°

[0149] Vertical field of view

[0150] θ V =V·Δθ=1080×0.0296mrad≈1.832°

[0151] At this time, the distance resolution of the solid-state camera at a distance of R = 282.8m

[0152] Δd|R＝282.8m =R·Δθ=282.8m×0.0296mrad≈8.37mm

[0153] Select the light source size d of the laser target 0 =5mm, light source divergence angle Ψ≥max(θ H ,θ V )=3.256°, the spacing ρ between 82 light sources of the airborne laser target is based on the actual installation situation. In this example, ρ=2000mm is assumed, and the spacing between 102 light sources of the ground laser target is ρ 1 =150mm.

[0154] Step 3: Calibrate the fixed ground optical alignment device 4

[0155] Install the ground laser target 10 on the outer edge of the ground solid-state camera 9 lens, install the ground solid-state camera 9 on the ground reference platform 11, calibrate the horizontal axis of the ground solid-state camera 9 target surface to be horizontal, and adjust the elevation angle β of the optical axis of the ground solid-state camera 9 0 ,like Figure 3 As shown, when β 0 When adjusted to ∠AOB = 45°, the pitch of the optical axis of the ground solid-state camera 9 is locked; the direction of the ground reference platform 11 is adjusted so that the optical axis azimuth of the ground solid-state camera 9 is α 0 Pointing to B, ∠BOy=ζ, when α 0 When adjusted to z, the orientation of the ground reference platform 11 is locked. At this time, the ground optical alignment device 4 is calibrated and fixed, and the optical axis of the ground solid-state camera 9 points to A.

[0156] Step 4: Calibrate and install the onboard optical alignment device 3

[0157] The 82 light sources of the airborne laser target are respectively installed on the left and right sides of the tethered UAV 1, and the pitch γ of the optical axis of the airborne solid-state camera 7 deviating from the reference line AJ of the tethered UAV 1 is determined according to the preset coordinates of the tethered UAV 1. 0 ,like Fig. 9 As shown, the optical axis orientation of the airborne solid-state camera 7 should be the same as AJ, γ 0 =-∠OAO'=-45°, Figure 8 AK is the direction of the optical axis after the airborne optical alignment device 3 is fixedly installed, and the light source of the airborne laser target 8 is calibrated to be parallel to AK.

[0158] Step 5: The tethered UAV 1 is launched into the air and aims at the ground control station 2. The system obtains the relative position, pitch and distance information between the air and the ground.

[0159] The tethered UAV 1 is powered on and launched, heading for a preset working position, and adjusting the bow direction of the tethered UAV 1 so that the light sources of the ground laser target 102 fall into the field of view of the airborne solid-state camera 7, thereby achieving air-to-ground mutual aiming.

[0160] The ground solid-state camera 9 captures the light source of the airborne laser target 8, and the imaging on the camera target surface is as follows: Figure 4 As shown in the figure, the horizontal coordinate values ​​of the two light sources on the target surface of the ground solid-state camera 9 are m 0 and n 0 , then the horizontal coordinate of the geometric center position of the airborne laser target 8 on the target surface of the ground solid-state camera 9 is

[0161]

[0162] From this, the position of the geometric center of the airborne laser target 8 deviating from the optical axis of the ground solid-state camera 9 can be calculated.

[0163]

[0164] The position α of the geometric center of the airborne laser target 8 relative to the ground solid-state camera 9 d-p ′=φ 0 ′.

[0165] The ordinate values ​​of the 82 light sources of the airborne laser target on the target surface of the ground solid-state camera 9 are l 0 and k 0 , then the ordinate of the geometric center position of the airborne laser target 8 on the target surface of the ground solid-state camera 9 is

[0166]

[0167] From this, the pitch of the geometric center position of the airborne laser target 8 from the optical axis of the ground solid-state camera 9 can be calculated.

[0168]

[0169] The method for the airborne solid-state camera 7 to obtain the azimuth and pitch of the geometric center position of the ground laser target 10 deviating from the optical axis of the airborne solid-state camera 7 is consistent with the above description. The azimuth α of the geometric center position of the ground laser target 10 deviating from the optical axis of the airborne solid-state camera 7 is measured. p-d =φ 1 , pitch The position α of the geometric center of the ground laser target 10 relative to the airborne solid-state camera 7 p-d ′=φ 1 ′.

[0170] The distance between the images of 82 light sources of the airborne laser target on the 9 target surfaces of the ground solid-state camera

[0171]

[0172] like Figure 6 As shown, the airborne inertial navigation device outputs the roll of the tethered UAV 1 as υ=υ 0 ,have

[0173] ρ 0 =F(ρ,φ 1 ,v 0 )=ρ 0d

[0174] Depend on Figure 6 In the geometric relationship, there is

[0175]

[0176] Available

[0177]

[0178] Step 6: Calculate the precise coordinates, heading, and pitch of the tethered drone 1 relative to the ground control station 2 by using the acquired azimuth, pitch, and distance information.

[0179] Depend on Figure 3 The geometric relationship shown, the x coordinate of the tethered drone 1

[0180]

[0181] The y coordinate of tethered drone 1

[0182]

[0183] The z coordinate of tethered drone 1

[0184]

[0185] The heading of the tethered UAV 1 relative to the ground control station 2

[0186] α d =360°-α p-d ′=360°-φ 1 '

[0187] like Figure 7 As shown, the pitch of the tethered drone 1

[0188]

[0189] Feasibility analysis:

[0190] Without considering the impact of terrain shielding, the horizontal coverage of the camera at a slant distance of R = 282.8m

[0191]

[0192] Vertical Coverage

[0193]

[0194] It can be considered that the selected solid-state camera has a sufficiently large field of view at R = 282.8 m, and the airborne solid-state camera 7 and the ground solid-state camera 9 can easily aim at each other, that is, the opposite laser targets should be able to enter the camera field of view more easily.

[0195] like Fig.10 As shown, point O is the location of the ground solid-state camera 9, point A is the working position of the tethered drone 1, plane ξ is the horizontal plane where the tethered drone 1 is located, and straight line AB is the intersection line of the horizontal field of view of the ground solid-state camera 9 and plane ξ. OA⊥AB, in this example, ∠BAx=45°. The tethered drone 1 moves in the AB direction Δd| R＝282.8m = 8.37 mm, the ground solid-state camera 9 can identify the corresponding x-axis direction offset

[0196]

[0197] Similarly, the offset of the tethered drone in the y-axis and z-axis directions Δy≈11.84mm, Δz≈11.84mm, that is, as long as the offset of the tethered drone 1 in the x-, y-, and z-axis directions is greater than 11.84mm, the system can recognize it and send the recognized offset to the flight control system of the tethered drone 1, which is sufficient to ensure the stability of the tethered drone 1.

[0198] According to the parameters given in this example, the system's ranging accuracy for tethered drone 1 at R = 282.8m

[0199]

[0200] In practical applications, the ground solid-state camera 9 can use a zoom lens. Under the premise that the tethered UAV 1 is stably hovering at the working position and the air-ground sighting is achieved, the focal length of the ground solid-state camera 9 is adjusted. For example, the focal length is adjusted to f = 270mm. At this time, the horizontal coverage range of the ground solid-state camera 9 at the tethered UAV 1 is Vertical Coverage It can still ensure that the tethered UAV 1 is within the field of view of the ground solid-state camera 9, and the camera distance resolution can be increased to 2 times of the original; in addition, the ground solid-state camera 9 can use algorithms such as sub-pixel recognition to locate the airborne laser target 8, which can continue to increase the camera distance resolution to 4 times of the original. By using the above two methods at the same time, the ranging accuracy of the tethered UAV 1 at R = 282.8m can be increased to I R ≈0.148m. The positioning accuracy of the tethered UAV 1 given by the system is comparable to that of the RTK satellite navigation technology.

[0201] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. An optoelectronic positioning system for tethered drones that does not rely on satellite navigation and ranging equipment, characterized in that: The system comprises: an airborne optical alignment device deployed on a tethered UAV and a ground optical alignment device and a solution positioning module deployed on a ground control station; wherein the airborne optical alignment device comprises an airborne solid-state camera and an airborne laser target, and the ground optical alignment device comprises a ground solid-state camera and a ground laser target; The airborne optical alignment device is used to image the ground laser target through the airborne solid-state camera to obtain the coordinate value of the ground laser target on the target surface of the airborne solid-state camera; The ground optical alignment device is used to image the airborne laser target through a ground solid-state camera to obtain the coordinate value of the airborne laser target on the target surface of the ground solid-state camera; The calculation and positioning module is used to calculate the position information of the UAV from the above coordinate values ​​according to the optical geometric relationship, so as to achieve positioning; The airborne laser target includes no less than two light sources, which are respectively installed on the left and right sides of the tethered UAV azimuth axis and are equidistant from the UAV azimuth axis. The connecting line of the two light sources passes through the geometric center of the tethered UAV, and the light sources are both pointed in parallel with the optical axis direction of the airborne solid-state camera. The ground laser target includes no less than two light sources, the line between the two light sources passes through the optical axis of the camera, and the perpendicular bisector of the line between the two light sources passes through the optical axis of the camera, the geometric center of the ground laser target coincides with the position of the optical axis of the ground solid-state camera, and the direction of the light source reference line is parallel to the direction of the optical axis of the ground solid-state camera; The specific processing process of the solution positioning module is as follows: Establish a coordinate system with the ground control station as the origin; The horizontal coordinates m of the two light sources of the airborne laser target on the ground solid-state camera target surface p and n p ; The ordinate k of the two light sources of the airborne laser target on the ground solid-state camera target surface p and l p ; The horizontal coordinate m of the two light sources receiving the ground laser target on the target surface of the airborne solid-state camera d and n d ; The ordinate k of the two light sources receiving the ground laser target on the target surface of the airborne solid-state camera d and l d ; According to the horizontal axis m p and n p And the vertical coordinate k p and l p , the geometric center position of the airborne laser target deviates from the optical axis of the ground solid-state camera by α d-p and pitch β d-p ; According to the horizontal axis m d and n d And the vertical coordinate k d and l d , the position of the geometric center of the ground laser target deviates from the optical axis of the airborne solid-state camera by α p-d and pitch β p-d ; Combined with the roll υ output by the onboard inertial navigation device of the tethered UAV, the slant range R of the ground solid-state camera and the onboard solid-state camera is calculated; According to the optical geometric relationship, the coordinates, heading and pitch of the tethered UAV are calculated from the azimuth, pitch and slant range; According to the horizontal coordinate m p and n p And the vertical coordinate k p and l p , the geometric center position of the airborne laser target deviates from the optical axis of the ground solid-state camera by α d-p and pitch β d-p ; Specifically include: According to the horizontal axis m p and n p The horizontal coordinate x of the geometric center position of the airborne laser target on the ground solid-state camera target surface is calculated by the following formula: 0-p for: According to the following formula, the geometric center position of the airborne laser target deviates from the optical axis position of the ground solid-state camera by α d-p for: a d-p =x 0-p ·Dth p Among them, Δθ p is the angular resolution of the ground-based solid-state camera, f p is the focal length of the ground solid-state camera, and the size of a single phase element of the ground solid-state camera is N p ×N p ; According to the ordinate k p and l p The vertical coordinate y of the geometric center position of the airborne laser target on the ground solid-state camera target surface is calculated by the following formula: 0-p for: According to the following formula, the pitch β of the geometric center position of the airborne laser target from the optical axis of the ground solid-state camera is calculated: d-p for: b d-p =y 0-p ·Dth p ; According to the horizontal coordinate m d and n d And the vertical coordinate k d and l d , the position of the geometric center of the ground laser target deviates from the optical axis of the airborne solid-state camera by α p-d and pitch β p-d ; Specifically include: According to the horizontal axis m d and n d The horizontal coordinate x of the geometric center position of the ground laser target on the target surface of the airborne solid-state camera is calculated by the following formula: 0-d for: According to the following formula, the geometric center position of the ground laser target deviates from the optical axis position of the airborne solid-state camera by α p-d for: a p-d =x 0-d ·Dth d Among them, Δθ d is the angular resolution of the onboard solid-state camera, f d is the focal length of the airborne solid-state camera, and the size of a single phase element of the airborne solid-state camera is N d ×N d ; According to the ordinate k d and l d The ordinate y of the geometric center position of the ground laser target on the target surface of the airborne camera is calculated by the following formula: 0-d for: According to the following formula, the pitch β of the geometric center position of the ground laser target from the optical axis of the airborne solid-state camera is calculated: p-d for: b p-d =y 0-d ·Dth d ; The slant distance R between the ground solid-state camera and the airborne solid-state camera is calculated by combining the roll υ output by the airborne inertial navigation device of the tethered UAV; specifically: Among them, F(·) represents the p-d When and υ are known, the projection length of the distance ρ between the two light sources of the airborne laser target on the plane parallel to the target surface of the ground solid-state camera at the tethered UAV; The coordinates, heading and pitch of the tethered UAV are calculated from the azimuth, pitch and slant range according to the optical geometric relationship; specifically including: Coordinates of the tethered drone (x d ,y d ,z d )for: x d =R·cos(β0+β d-p )·cos(α0+α d-p ′) y d =R·cos(β0+β d-p )·sin(α0+α d-p ′) z d =R·sin(β0+β d-p ) Among them, α d-p ′ is the position of the geometric center of the airborne laser target relative to the ground solid-state camera, α0 is the azimuth angle of the optical axis of the ground solid-state camera, β0 is the pitch angle of the optical axis of the ground solid-state camera, and β d-p is the pitch of the geometric center of the airborne laser target from the optical axis of the ground solid-state camera, and R is the slant distance between the ground solid-state camera and the airborne solid-state camera; The heading of the tethered UAV relative to the ground control station α d for: α d ＝360°-α p-d ' Among them, α p-d ' is the position of the geometric center of the ground laser target relative to the airborne solid-state camera; Pitch β of tethered drone d for: b d =-(-γ0-β p-d ) Where γ0 is the pitch of the optical axis of the airborne solid-state camera away from the baseline of the tethered drone, -90°≤β d ,β p-d ,γ0≤90°,β d ,β p-d ,γ0 is taken as positive when it deviates from the horizontal plane upward and negative when it deviates from the horizontal plane downward.

2. The photoelectric positioning system for tethered unmanned aerial vehicles that does not rely on satellite navigation and ranging equipment according to claim 1 is characterized in that: The airborne solid-state camera adopts a CMOS or CCD sensor, and the ground solid-state camera adopts a CMOS or CCD sensor. The distance resolution of the airborne solid-state camera and the ground solid-state camera during normal operation is not less than a preset threshold.

3. The photoelectric positioning system for tethered unmanned aerial vehicles according to claim 1, which does not rely on satellite navigation and ranging equipment, is characterized in that: The ground optical alignment device also includes a ground reference platform, which is used to realize the initialization calibration of the optical axis pointing of the ground solid-state camera.

Images