A tethered airborne opto-electronic imaging target positioning method

Abstract

The application discloses a tethered aerial platform photoelectric imaging target positioning method, which collects ground platform data (geodetic coordinates and attitude angles), aerial platform data (height, translation amount and attitude angles) and photoelectric pod data (target relative distance and turntable attitude angle) at a same time, solves according to a model, obtains geodetic coordinate values of the target, realizes target positioning, and obtains the accurate geodetic coordinates of the target based on the position and direction reference of the aerial platform obtained by the ground positioning navigation device and the video attitude measurement device and the relative position and direction of the target obtained by the photoelectric pod. The application solves the problem of how to obtain reconnaissance and positioning capability under the condition that the attitude control of the tethered aerostat platform is difficult to be fixed and the aerial platform does not carry an inertial navigation device.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectric imaging positioning systems, and relates to a tethered aerial photoelectric imaging target positioning method. BACKGROUND

[0002] Photoelectric imaging is a reconnaissance means with large amount of information acquisition, suitable for human eye presentation characteristics and convenient for target identification and judgment, and is often used for military and police reconnaissance, monitoring, alerting and evidence collection. In order to make the observation range larger and the visual distance longer, the aerial mode can effectively avoid the shelter of ground buildings and trees, transcend the influence of earth curvature on the visual distance, and realize long-distance imaging detection and positioning. However, the aircraft or unmanned aerial vehicle needs to consume energy and cannot work continuously in the air for a long time due to the limitation of carrying capacity, so the development direction is to use the aerial platform to supply power by tethering, that is, to continuously supply power to the aerial platform by the ground power supply system through the cable, and the tethered aerial photoelectric imaging positioning equipment can meet various application requirements.

[0003] The tethered aerial photoelectric imaging positioning equipment generally includes a tethered aerial platform, a photoelectric pod carried by the tethered aerial platform, a tethering cable, a power supply system and a control terminal or equipment with the same function. Since the aerial platform needs to consume power by using a motor to keep the aerial platform hovering in the air, it is an important work in equipment development to reduce unnecessary load as much as possible to improve system reliability and reduce system power consumption.

[0004] The aerial photoelectric imaging positioning generally needs to measure the position (geodetic coordinates) of the system itself, the relative angle and relative distance of the target relative to the system itself, so it often needs to have a positioning navigation device providing a north reference, a laser range finder, a photoelectric pod azimuth angle and pitch angle solver and other sensors.

[0005] Among them, the inertial navigation device with a north measurement accuracy of 1mrad (root mean square error) generally weighs about 5kg and can be carried by the aerial platform, accounting for 50% to 20% of the effective payload (reconnaissance positioning type, effective payload is 10kg, 20kg) of the tethered aerial system. Using the method for measuring the position of the aerial platform described in application No. 202010165921.9 or other similar methods can reduce the load of the aerial platform by about 25% to 50% or more. In this case, the system reliability will be significantly improved and the power consumption will be reduced; however, how to realize accurate angle measurement and positioning of the target becomes an important problem to ensure the performance of the equipment.

[0006] Application No. 201810511325.4 describes a tethered aerial fire reconnaissance platform, which includes a suspended unmanned aerial vehicle fire reconnaissance platform, a tethering cable, a cable automatic winding and unwinding system, a high-voltage power supply system and a ground control center, and does not involve a reconnaissance and positioning scheme.

[0007] Application No. 201611162336.3 describes a vehicle-mounted unmanned aerial vehicle tethered communication reconnaissance system, including a tethered power supply and communication system, and does not involve a reconnaissance scheme.

[0008] Application No. 201910070975.4 describes a multi-baseline GNSS attitude measurement device and method based on a floating platform, including a positioning information solving module, a navigation system position calculation module, a yaw angle and pitch angle calculation module, and a roll angle calculation module. The aircraft attitude is calculated by a satellite positioning device, and the reconnaissance is not involved.

[0009] Application No. 201910700894.8 describes an aerial reconnaissance positioning system and method, the system includes an operation platform and a multi-rotor aircraft, which is a kind of aircraft device based on mobile phone positioning and Bluetooth as control channel. The gimbal carries a monitoring device to shoot the geographical environment of the target area. The image transmission device and the flight control device are used to adjust the height and attitude of the multi-rotor aircraft. The GSM mobile phone positioning instrument is used to locate the target mobile phone. The operation platform sends instructions to the GSM mobile phone positioning instrument through the Bluetooth wireless module. The method includes: obtaining the mobile phone number of the target mobile phone and the cell number and public network main frequency of the area where the target mobile phone is located; sending a short message to the target mobile phone to confirm whether the target mobile phone is in the on state; positioning the target mobile phone in different gain modes, including high gain mode, medium gain mode and low gain mode. The self-positioning of this scheme is limited by the communication positioning capability of the mobile phone, and the accuracy is not high. It is difficult to position in the case of weak communication base station coverage in the wild. The system also does not involve tethering and target coordinate positioning function.

[0010] These devices and methods respectively involve optical measurement of the attitude of the airborne platform, satellite positioning device double station measurement, or describe a non-tethered aerial reconnaissance positioning system, and do not involve specific reconnaissance positioning methods based on tethered floating platforms. SUMMARY

[0011] (I) Invention purpose

[0012] The purpose of the present application is to provide a method for positioning a target using a tethered airborne optoelectronic imaging target positioning system, which solves the problem of how to obtain reconnaissance positioning capability in the case of difficult attitude control of the tethered floating platform and the airborne platform without a inertial navigation device.

[0013] (II) Technical scheme

[0014] In order to solve the above technical problems, the present application provides a tethered aerial optoelectronic imaging target positioning method, which is realized based on a tethered aerial optoelectronic imaging target positioning system, the target positioning system comprising a ground platform and an aerial platform, wherein the ground platform comprises a positioning navigation device, a video attitude determination device, a tethering device and a control terminal, the control terminal is operated by an operator, the positioning navigation device is used for measuring the pose of a ground platform installation base, the video attitude determination device obtains pixel coordinates of aerial platform marker points through observation, the video attitude determination device base is fixedly connected with the positioning navigation device, the installation direction is ensured to be consistent with the shaft system of the positioning navigation device, the optical axis of the video attitude determination device can be finely adjusted along the roll axis and the pitch axis direction, and the optical axis is controlled by an inclination sensor to ensure that it is perpendicular to the horizontal plane, i.e. observing straight up; through closed-loop control based on image position deviation, the aerial platform can be kept within the field of view of the video attitude determination device.

[0015] The target positioning method of the present application comprises the following steps:

[0016] Step 1, determining time synchronization of each device in the system or outputting data with time labels;

[0017] Step 2, the operator performs operations through handle keys of the control terminal or keys of control software, searches and selects a target, and triggers the system to collect data of each device at the same time through automatic tracking or manual aiming and pressing a laser ranging key;

[0018] Step 3, reading data of the positioning navigation device on the ground platform as a direction reference and a position reference for target positioning, containing local geodetic coordinates (horizontal position and height), an included angle of the ground platform with the north direction, an azimuth angle, a pitch angle and a roll angle;

[0019] Step 4, reading data of the video attitude determination device, including pixel coordinates (x1, y1, x2, y2, x3, y4…) of several marker points on the aerial platform; reading data of the aerial platform, including a height h, a pitch angle β A , a roll angle ω A of the aerial platform. According to the above data, the lateral translation position (ΔX A0 , ΔY A0 ) of the aerial platform relative to the ground platform and an azimuth angle α A are calculated. Parameters (α A , β A , ω A , ΔX A0 , ΔY A0 , h) are used for coordinate system conversion calculation;

[0020] Step 5, read the relative rotation angle of the azimuth turntable and the elevation turntable when the sensor of the airborne platform optoelectronic pod aims at the target (for the optoelectronic pod with two-axis turntable structure), or the relative rotation angle of the azimuth turntable, the elevation turntable and the roll turntable when the sensor of the airborne platform optoelectronic pod aims at the target (for the optoelectronic pod with three-axis turntable structure), and the relative distance value of the target obtained by the ranging sensor of the optoelectronic pod, as the relative position parameters of the target;

[0021] Step 6, the positioning module component is deployed in the control terminal, and the target coordinate value is calculated according to the mathematical model and the collected data.

[0022] (Three) beneficial effects

[0023] The tethered airborne optoelectronic imaging target positioning method provided by the above technical solution has the following beneficial effects:

[0024] First, the target can be effectively imaged and positioned to obtain accurate geodetic coordinates of the target, including horizontal position and height value, even if the airborne platform does not have its own attitude determination and positioning capability.

[0025] Second, when the tethered airborne optoelectronic imaging positioning system is fixed or resident on the ground, the positioning method is not affected by the zero drift of the inertial navigation device, has no position drift, and has high continuous positioning accuracy.

[0026] Third, when the tethered airborne optoelectronic imaging positioning system is used on a vehicle or a ship, the method can also effectively position the target and obtain its accurate geodetic coordinates. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a data acquisition distribution diagram of the tethered airborne optoelectronic imaging positioning system.

[0028] Figure 2 is a schematic diagram of the tethered airborne optoelectronic imaging positioning system.

[0029] Figure 3 is a positioning flow diagram of the tethered airborne optoelectronic imaging positioning system.

[0030] Figure 4 is a positive direction definition of the rotation transformation involved in the present application. DETAILED DESCRIPTION

[0031] In order to make the purpose, content and advantages of the present application more clear, the specific embodiments of the present application are described in detail below in combination with the drawings and examples.

[0032] As Figure 1 , 2As shown in Figure 3, the implementation steps of the tethered aerial photoelectric imaging target localization method in this embodiment are as follows:

[0033] Step 1: Using the clock of the Beidou navigation satellite data receiver in the system positioning and navigation device as the reference time, the timing accuracy of the embodiment is 30ns. Ensure that the time of each electronic device in the system is consistent. Each device in the system outputs data synchronously with Beidou time as the reference, or outputs data with a time tag.

[0034] Step 2: The operator uses the control terminal's handle buttons to operate the electro-optical pod, search for and select the target, and automatically track and lock onto the target; pressing the laser ranging button triggers the control system to collect the time interval (t) at this moment. R Data for each device under )

[0035] Step 3, the control software in the control terminal reads t R Measurement data from the positioning and navigation device on the ground platform, including the local latitude and longitude coordinates (L0, B0, h0) of the ground platform measured by satellite and inertial navigation system. R The inertial navigation device measures the horizontal angle (α0) between the ground platform and the north direction, as well as the azimuth, pitch, and roll attitude angles (α0, β0, ω0) of the ground platform. The geodetic coordinate accuracy of the positioning and navigation device used in the embodiment is 10m horizontal error (CEP), 10m elevation error (PE), 1m north finding accuracy, and 0.08m attitude measurement error.

[0036] Step 4: The video attitude measurement device on the ground platform adjusts itself based on the data feedback from the tilt sensor to make the optical axis perpendicular to the horizontal plane. The perpendicularity error in this embodiment is 0.1 mrad.

[0037] The control software in the control terminal reads t R The video attitude measurement device on the ground platform outputs the pixel coordinates of the launch platform marker points. In this embodiment, the video array pixel size is 4088×4088. The correspondence between the marker points is determined based on feature matching, and the two marker points with the best contrast and the largest pixel distance (x, y, y) are selected. i y i x j y j In the example, for two points with a pixel distance greater than 2044, the marker point vector is calculated based on the perspective projection relationship and the relative position parameters of the marker points in physical space. The azimuth angle α in the attitude measurement coordinate system ijv Based on the azimuth deviation δ between the attitude measurement coordinate system and the inertial coordinate system (δ is a small angular quantity, as the two axes can be kept basically parallel through installation), the azimuth angle is transformed into the inertial coordinate system and denoted as α. ijg Then the azimuth angle α of the launch platform relative to the inertial coordinate system is...AG =α ijg -α ij0 In the formula, α ij0 For the marker point vector The azimuth deflection relative to the zero position of the launch platform; read t R The altitude h of the launch platform relative to the ground, measured by the flight control components on the launch platform, is output by the launch platform. In this embodiment, the altitude of the launch platform is in the range of 50m to 300m, with an altitude error of 0.1m. The lateral translation position of the launch platform (ΔX) is also considered. A0 ΔY A0 It can be calculated using the following formula:

[0038]

[0039] In the formula, M x M represents the horizontal pixel count of the video attitude measurement device (4088 in this example). y The vertical pixel count of the video pose measurement device (4088 in this example), r i The vector formed by the mounting position point o of the optoelectronic payload on the launch platform and the marker point i The length of x A o A y A Projection on the plane, α i The direction angle of the projection is fov, and the field of view angle of the video attitude measuring device is fov.

[0040] Read t R The pitch angle β output by the launch platform A , roll angle ω A The pitch and roll angle errors are 0.3 mrad;

[0041] Step 5: After the electro-optical pod on the launch platform aims at the target, the control software in the control terminal reads the data. R When the optoelectronic pod sensor of the launch platform aims at the target, the relative rotation angle (α) of the azimuth turntable and the pitch turntable is... P ,β P ), or measure the azimuth turntable (α) P ), pitch turntable (β) P ), and the relative rotation angle (α) of the roll turntable. P ,β P ,ω P (For a three-axis electro-optical pod), the electro-optical pod in this embodiment is a two-axis inertial stabilized structure (weight 18kg, azimuth and pitch measurement errors are 0.1mrad); the electro-optical pod ranging sensor t R The relative distance value (D) of the target obtained at that time. In this embodiment, the optoelectronic pod uses a 1.54μm laser rangefinder, and the ranging error is 5m.

[0042] Step 6, parameters (L0, B0, h0), (a0), h, (a AG , b A , w A ), (AX A0 , AY A0 ), (a P , b P ), D, the installation error angle (a e , b e , w e ) of the photoelectric coordinate system relative to the airborne coordinate system, the azimuth deviation δ of the attitude determination coordinate system and the inertial coordinate system are input into the positioning software component of the control terminal control software, and the target coordinate calculation is completed according to the mathematical model defined by formulas (2)-(11):

[0043] The calculation process of the rotation transformation matrix is as follows:

[0044] 1) Calculate the coordinates of the target in the photoelectric coordinate system

[0045]

[0046] 2) Convert the target coordinates to the airborne coordinate system

[0047] [x A ,y A ,z A ] T =A1 -1 [x P ,y P ,z P ] T (3)

[0048] In the formula, A1 is calculated by the rotation transformation formula (4), wherein a, b, and w are substituted by (a e , b e , w e ).

[0049]

[0050] In the formula, a, b, and w are the azimuth, pitch, and roll amounts of the Euler angle defined in the zyx order, and the positive direction of the angle is shown in the following figure. Figure 4

[0051] 3) Transfer the north reference of the inertial coordinate system to the airborne coordinate system

[0052] The north reference of the inertial coordinate system is transferred to the airborne coordinate system according to the following formula, and the Euler angle (a A , b A , w A ) of the airborne coordinate system relative to the north-west-sky coordinate system is obtained.

[0053] ​Alpha A = Alpha AG + Alpha0 (5)

[0054] 4) Target coordinates are converted to the north-west celestial coordinate system

[0055] [x N ,y N ,z N ] T = A2 -1 [x A ,y A ,z A ] T (6)

[0056] A1 is calculated from equation (1) where (alpha, beta, omega) are substituted for (alpha A , beta A , omega A ) respectively.

[0057] 5) Target coordinates are converted to the geocentric coordinate system

[0058] The ground station coordinates are converted to the rectangular coordinate quantities (X0, Y0, Z0) in the geocentric coordinate system by substituting (L0, B0, h0) into the variables (L, B, h) in equation (8) respectively.

[0059]

[0060] In the equation, a = 6378137.0, e = 0.0066943800229

[0061] 6) The transformation relationship between the north-west celestial coordinate system and the geocentric coordinate system is determined according to the following equation.

[0062] [x e ,y e ,z e ,1] T = A3 -1 [z a ,-y a ,x a ,1] T (9)

[0063] In the equation, A3 is calculated by substituting (L0, B0, X0, Y0, Z0) into the variables (L, B, X, Y, Z) in the equation respectively.

[0064]

[0065] 7) The geocentric coordinates of the target are converted to the latitude and longitude representation

[0066] The following equation is used for the calculation:

[0067]

[0068] Wherein, the latitude B is calculated by using a recursive algorithm.

[0069] Thus, the target coordinate is obtained.

[0070] The above merely describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A method of locating a tethered aerial opto-electronic imaging target, the method comprising: The application discloses a target positioning method based on a tethered aerial photoelectric imaging target positioning system, and relates to the technical field of target positioning. The target positioning method comprises the following steps: Step 1, determining the time synchronization of each device or outputting data with a time label; Step 2, an operator searches and selects a target through the operation of a control terminal, and triggers the system to collect the data of each device at the same time by pressing a laser ranging key through automatic tracking or manual aiming; Step 3, reading the data of a positioning navigation device on the ground platform as the direction reference and position reference for target positioning, which comprises local geodetic coordinates, horizontal position and height, the included angle between the ground platform and the north direction, the azimuth angle, the pitch angle and the roll attitude angle; Step 4: Read the data from the video attitude measurement device, including the pixel coordinates of several marker points on the launch platform (x1, y1, x2, y2, x3, y4…); read the launch platform data, including the platform's height h and pitch angle β. A , roll angle ω A Based on the above data, calculate the lateral translation position (ΔX) of the launch platform relative to the ground platform. A0 ΔY A0 ), azimuth angle α A ; Parameter (α) A ,β A ω A ΔX A0 ΔY A0 , h), used for coordinate system transformation calculations; Step 5, reading the relative rotation angle of a turret of a photoelectric pod when the photoelectric pod aims at the target, and the relative distance value of the target obtained by a ranging sensor of the photoelectric pod; the relative distance value of the target obtained by the ranging sensor of the photoelectric pod is used as the relative position parameter of the target; Step 6, deploying a positioning module component in the control terminal, and calculating the coordinate value of the target according to the mathematical model and the collected data; In step 4, the correspondence of the landmark points is determined based on feature matching, two landmark points (x i , y i , x j , y j ) with the best contrast and the largest pixel distance are selected, and the landmark point vector is calculated according to the perspective projection relationship and the relative position parameters of the landmark points in the physical space. ijv The azimuth angle α ijg in the inertial coordinate system is converted from the azimuth angle α ijv in the measurement coordinate system according to the azimuth deviation δ between the measurement coordinate system and the inertial coordinate system, and is recorded as α AG , wherein the azimuth angle α ijg of the aerial platform relative to the inertial coordinate system is α ij0 = α ijg - α AG , and in the formula, α ij0 is the azimuth deviation of the landmark point vector relative to the azimuth zero position of the aerial platform; the height h of the aerial platform relative to the ground is read at t R , which is measured by the flight control component on the aerial platform, and the lateral translation position (ΔX A0 , ΔY A0 ) of the aerial platform is calculated according to the following formula: (1) In the formula, M x M represents the number of horizontal pixels in the video attitude measurement device. y r represents the vertical pixel count of the video pose measurement device. i The vector formed by the mounting position point o of the optoelectronic payload on the launch platform and the marker point i The length of x A o A y A Projection on the plane, α i Let fov be the orientation angle of the projection, and t be the field of view angle of the video attitude measuring device; read t R The pitch angle β output by the launch platform A , roll angle ω A .

2. The tethered aerostat photo imaging target location method of claim 1 wherein, In step 5, for the photoelectric pod with a two-axis turret structure, the relative rotation angle of the turret comprises the relative rotation angles of the azimuth turret and the pitch turret; for the photoelectric pod with a three-axis turret structure, the relative rotation angle of the turret comprises the relative rotation angles of the azimuth turret, the pitch turret and the roll turret.

3. The tethered aerostat photo imaging target location method of claim 2 wherein, In step 1, the clock of a Beidou navigation satellite data receiver in the system positioning navigation device is used as the reference time to determine the time synchronization of each electronic device, and each electronic device synchronously outputs data with the Beidou time as the reference or outputs data with a time label.

4. The tethered aerostat photo imaging target positioning method of claim 3 wherein, In step 3, the control terminal reads the consistent time t R The measurement data of the positioning and navigation device on the ground platform at time t, including the local longitude and latitude coordinates (L0, B0, h0) of the ground platform measured by the satellite and inertial navigation combined navigation, t R The horizontal angle (α0) of the ground platform to the north direction measured by the inertial navigation device, and the azimuth, pitch and roll attitude angles (α0, β0, ω0) of the ground platform.

5. The tethered aerostat photo imaging target positioning method of claim 4 wherein, In step 5, after the photoelectric pod on the ascending platform aims at the target, the control terminal reads the relative rotation angles (α R , β P ) of the azimuth rotation table and the elevation rotation table, or measures the relative rotation angles (α P , β P , ω P ) of the azimuth rotation table, the elevation rotation table, and the roll rotation table, and the relative distance value D of the target obtained by the photoelectric pod ranging sensor at t P . R ​ 6. The tethered aerostat photo imaging target positioning method of claim 5 wherein, In step 6, the parameters (L0, B0, h0), (a0), h, (a AG , b A , w A ), (AX A0 , AY A0 ), (a P , b P ), D, the installation error angles (a e , b e , w e ) of the photoelectric coordinate system relative to the lift-off coordinate system, and the azimuth deviation d of the attitude determination coordinate system relative to the inertial coordinate system are input into the control terminal, and the target coordinate is calculated according to the mathematical model defined by the formulas (2)-(11). 1) calculating the coordinates of the target in the photoelectric coordinate system (2) 2) converting the target coordinates to the aerial coordinate system (3) In the formula, A1 is calculated by the rotation transformation formula (4), where α, β, ω are substituted into (α... e , β e , ω e ); In the formula, alpha, beta and omega are the azimuth, pitch and roll amounts of the Euler angles defined according to the zyx order; 3) transferring the north direction reference of the inertial coordinate system to the aerial coordinate system The north reference of the inertial coordinate system is transferred to the airborne coordinate system according to the following formula to obtain the Euler angles (α A , β A , ω A ) of the airborne coordinate system relative to the north-west-sky coordinate system; α A= α AG+ α0 (5) 4) converting the target coordinates to the north-western sky coordinate system (6) A2 is calculated from formula (6) where a, β, ω are substituted for (a A , β A , ω A ) respectively; 5) converting the target coordinates to the geocentric coordinate system (L0, B0, h0) are substituted into the variables (L, B, h) in formula (8) respectively, and the coordinates (X0, Y0, Z0) of the ground platform in the geocentric coordinate system are converted; (8) 6) determining the conversion relationship between the north-western sky coordinate system and the geocentric coordinate system according to the following formula (9) In the formula, A3 is calculated by substituting (L0, B0, X0, Y0, Z0) into the variables (L, B, X, Y, Z) of the formula (10) respectively; 7) Convert the geocentric coordinates of the target into longitude and latitude The following formula is used for calculation: (11) Where the latitude B is calculated using a recursive algorithm; Thus, the target coordinates are obtained.

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