Airborne photoelectric system installation error air online calibration method based on track constraint

Abstract

The invention provides an airborne photoelectric system installation error air online calibration method based on track constraint. The method comprises the following steps: continuously and stably tracking a known target at a ground position by planning a specific flight track, and resolving a target positioning error in real time through space coordinate transformation according to motion parameters such as the position and attitude of an aerial carrier, the angle of a photoelectric system frame and the like and target position information; and the installation error and the frame zero error of the photoelectric system relative to the aerial carrier are identified from the target positioning error, so that high-precision visual axis pointing and target positioning are realized.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection and positioning, specifically relating to an online aerial calibration method for installation errors of airborne photoelectric systems based on flight path constraints. Background Technology

[0002] Target positioning, a typical function and task of airborne optoelectronic systems, relies heavily on its accuracy as a comprehensive technical indicator for evaluating system performance. Installation errors and frame zero-position errors relative to the carrier aircraft, leading to line-of-sight pointing errors, severely restrict improvements in target positioning accuracy, necessitating calibration compensation. Ground-based target calibration aligns the optoelectronic system's line of sight with the carrier aircraft's axis using a specific target plate. This method requires the aircraft to be horizontally positioned, constrained by the target plate, and lacks roll freedom, thus failing to achieve high-precision positioning across the entire field of view. Therefore, an in-flight online calibration method is needed to compensate for the impact of installation errors and frame zero-position errors on target positioning accuracy, enabling rapid remounting, agile calibration, and precise compensation of the airborne optoelectronic system. Summary of the Invention

[0003] To address the problem of reduced line-of-sight pointing accuracy and consequently low positioning accuracy caused by installation errors and frame zero-position errors in optoelectronic systems, this invention provides an online airborne calibration method for installation errors of airborne optoelectronic systems based on flight path constraints. By planning a specific flight path and continuously and stably tracking a target with a known ground position, and based on motion parameters such as the aircraft's position, attitude, and the optoelectronic system frame angle, along with target position information, the target positioning error is calculated in real time through spatial coordinate transformation. This allows for the identification of the optoelectronic system's installation error relative to the aircraft and the frame zero-position error from the target positioning error, thereby achieving high-precision line-of-sight pointing and target positioning.

[0004] An online in-flight calibration method for installation errors of airborne optoelectronic systems based on flight path constraints, characterized by the following steps:

[0005] Step 1, Flight trajectory planning: Based on the known ground target position (λ) c ,L c ,h c Using (x0, y0, z) as the reference origin, the x-axis points due east, the y-axis points due north, and the z-axis points to the sky along the perpendicular from the target point. The planned aircraft flies from west to east over the ground target from waypoint (x0, y0, z) to waypoint (x1, y1, z), then turns 180° left to waypoint (x2, y2, z), and continues flying from east to west to waypoint (x3, y3, z). The aircraft then adjusts its trajectory to return from waypoint (x3, y3, z) to waypoint (x4, y4, z). The length of segment A is 1 km, satisfying 9.5 km ≤ x A ≤10.5km,|y A |≤5m, track angle 90°; segment B satisfies -0.5km≤x B≤ 0.5 km, |y| ≤ 0.5 km B -10 km, |y| ≤ 5 m, track angle -90°; leg C satisfies -0.5 km ≤ x C ≤ 0.5 km, |y C -10 km, |y| ≤ 5 m, track angle 90°; leg D satisfies 9.5 km ≤ x D ≤ 10.5 km, |y D | ≤ 5 m, track angle -90°;

[0006] The coordinate scale of the real-time position (λ, L, h) of the carrier relative to the reference origin is calculated according to the following formula:

[0007]

[0008] wherein x, y and z are the eastward, northward and skyward distances of the real-time position of the carrier relative to the ground target; λ c , L c and h c are the longitude, latitude and altitude of the ground target; λ, L and h are the longitude, latitude and altitude of the real-time position of the carrier; R N and R M are the radii of curvature of the prime vertical circle and the meridian at the ground target; x A represents the eastward distance of the carrier from the reference origin when in leg A, y A represents the northward distance of the carrier from the reference origin when in leg A, x B represents the eastward distance of the carrier from the reference origin when in leg B, y B represents the northward distance of the carrier from the reference origin when in leg B, x C represents the eastward distance of the carrier from the reference origin when in leg C, y C represents the northward distance of the carrier from the reference origin when in leg C, x D represents the eastward distance of the carrier from the reference origin when in leg D, y D represents the northward distance of the carrier from the reference origin when in leg D;

[0009] Step 2, target pointing guidance: read the carrier position, attitude and target position information, and calculate the target pointing in the body coordinate system according to the following formula

[0010]

[0011] wherein is the carrier position matrix, determined by the longitude and latitude (λ, L) of the carrier; is the carrier attitude matrix, determined by the attitude angles (ψ, θ, γ) of the carrier; and are the carrier and target earth rectangular coordinate vectors, respectively, whose earth spherical coordinate longitude and latitude are determined by

[0012] The azimuth frame position driving command ψ of the optoelectronic system when the line-of-sight points to the target is calculated by the following formula cmd and the pitch frame position driving command θ cmd :

[0013]

[0014] wherein atan2 represents an inverse tangent function, asin represents an inverse sine function, and represent the three-dimensional components of the target pointing ;

[0015] The line-of-sight is made to point to the target under the action of the position driving commands, and after driving to the position, the line-of-sight is further controlled to accurately track the target by the vernier;

[0016] Step 3, target positioning in the flight section A: when the carrier flies to the flight section A, the known target is positioned, and the positioning error expression is:

[0017]

[0018] wherein δλ a , δL a , δh a are the longitude error, latitude error and height error of the target positioning when the carrier is in the flight section A; R am is the distance of the target relative to the carrier when the carrier is in the center of the flight section A, θ am is the pitch angle of the target relative to the carrier when the carrier is in the center of the flight section A; Δψ, Δθ, Δγ are the true values of the azimuth installation error, pitch installation error and roll installation error of the optoelectronic system relative to the carrier, respectively, and θ0 is the true value of the frame zero position error of the optoelectronic system to be calibrated;

[0019] Step 4, target positioning in the flight section B: when the carrier flies to the flight section B, the known target is positioned, and the positioning error expression is:

[0020]

[0021] wherein δλ b , δL b , δh b are the longitude error, latitude error and height error of the target positioning when the carrier is in the flight section B; R bm is the distance of the target relative to the carrier when the carrier is in the center of the flight section B, θ bm is the pitch angle of the target relative to the carrier when the carrier is in the center of the flight section B;

[0022] Step 5, target positioning in leg C: when the aircraft flies to leg C, the known target is positioned, and its positioning error expression is:

[0023]

[0024] wherein, δλ c , δL c , δh c are longitude error, latitude error and height error of target positioning when the aircraft is in leg C; R cm is the distance of target relative to the aircraft when the aircraft is in the center of leg C, and θ cm is the pitch angle of target relative to the aircraft when the aircraft is in the center of leg C.

[0025] Step 6, target positioning in leg D: when the aircraft flies to leg D, the known target is positioned, and its positioning error expression is:

[0026]

[0027] wherein, δλ d , δL d , δh d are longitude error, latitude error and height error of target positioning when the aircraft is in leg D; R dm is the distance of target relative to the aircraft when the aircraft is in the center of leg D, and θ dm is the pitch angle of target relative to the aircraft when the aircraft is in the center of leg D.

[0028] Step 7, installation error calculation: when planning the flight path, leg A and D are the same observation position, and leg B and C are the same observation position, which satisfies:

[0029]

[0030] The installation error of the photoelectric system is calculated according to the following formula:

[0031]

[0032] wherein, and are the estimated values of azimuth installation error, pitch installation error and roll installation error of the photoelectric system relative to the aircraft, is the estimated value of zero position error of the photoelectric system frame.

[0033] Specifically, the origin of the body coordinate system is located at the center of gravity of the carrier, the x-axis points to the right of the aircraft transverse axis, the y-axis points to the front of the aircraft longitudinal axis, and the z-axis satisfies the right-hand rule and is fixed to the body.

[0034] Specifically, the aircraft position matrix is calculated according to It is determined by the longitude λ and latitude L of the carrier aircraft.

[0035] Specifically, the carrier attitude matrix mentioned in step 2 according to It is determined by the aircraft's heading angle ψ, pitch angle θ, and roll angle γ.

[0036] Specifically, the rectangular coordinate vectors of the carrier aircraft and the target Earth mentioned in step 2 and The calculation formulas are as follows:

[0037]

[0038] Among them, R Na L represents the radius of curvature of the Earth's circumference at the location of the aircraft. a Indicates the latitude of the carrier aircraft, λ a Indicates the longitude of the aircraft, h a R indicates the aircraft's altitude. Nm L represents the radius of curvature of the Earth's geoid at the location of the target. m Indicates the target latitude, λ m Indicates the target longitude, h m The value represents the target altitude, and 'e' represents the Earth's oblateness.

[0039] The beneficial effects of this invention are as follows: By continuously and stably tracking a target at a known location using a planned specific flight path, the invention achieves online aerial calibration of the relative installation error of the optoelectronic system to the carrier aircraft and the zero-position error of the frame without changing the hardware composition, effectively improving the line-of-sight pointing accuracy and target positioning accuracy; This invention achieves coarse locking of a known target through geographical tracking, fine locking by manipulating the vernier, and autonomous flight according to the planned flight path, with a high degree of automation in the operation process, realizing rapid replacement and automatic calibration compensation of the airborne optoelectronic system. Attached Figure Description

[0040] Figure 1 This is a flowchart of the airborne online calibration method for installation errors of airborne optoelectronic systems based on flight path constraints, according to the present invention.

[0041] Figure 2 This is a schematic diagram of the airborne optoelectronic system for online calibration and flight trajectory planning in an embodiment of the present invention. Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments. The present invention includes, but is not limited to, the following embodiments.

[0043] The purpose of this invention is to provide an online in-flight calibration method for installation errors of airborne optoelectronic systems based on flight path constraints, specifically involving the following coordinate systems:

[0044] Earth coordinate system: origin at the center of the earth, x-axis at the equatorial plane pointing to the Greenwich meridian, z-axis pointing to the north pole of the earth, y-axis satisfying the right-hand rule and fixed to the earth.

[0045] Geographic coordinate system: origin at the center of the earth, x-axis at the equatorial plane pointing to the Greenwich meridian, z-axis pointing to the north pole of the earth, y-axis satisfying the right-hand rule and fixed to the earth.

[0046] Body coordinate system: origin at the center of the earth, x-axis at the equatorial plane pointing to the Greenwich meridian, z-axis pointing to the north pole of the earth, y-axis satisfying the right-hand rule and fixed to the earth.

[0047] The specific implementation process of the present application is shown in Figure 1 , including the following steps:

[0048] Step 1, flight path planning: taking the known target position (λ c ,L c ,h c ) as the reference origin, x-axis along the east direction, y-axis along the north direction, z-axis along the target plumb line pointing to the sky, planning the flight path of the aircraft, as shown in Figure 2 : the aircraft flies from waypoint 0 (x0, y0, z) over the ground target from west to east to waypoint 1 (x1, y1, z), turns left 180° to waypoint 2 (x2, y2, z), continues to fly from east to west to waypoint 3 (x3, y3, z), adjusts the flight path of the aircraft from waypoint 3 (x3, y3, z) to return to waypoint 4 (x4, y4, z) along the original route; the length of the flight segment A is 1km, which satisfies 9.5km≤x A ≤10.5km, |y A |≤5m, flight angle 90°; flight segment B satisfies -0.5km≤x B ≤0.5km, |y B -10km|≤5m, flight angle -90°; flight segment C satisfies -0.5km≤x C ≤0.5km, |y C -10km|≤5m, flight angle 90°; flight segment D satisfies 9.5km≤x D ≤10.5km, |y D |≤5m, flight angle -90°.

[0049] The coordinates of the real-time position (λ, L, h) of the aircraft relative to the reference origin are calculated according to the following formula:

[0050]

[0051] where x, y and z are the eastward, northward and skyward distances of the real-time position of the aircraft relative to the ground target; λ c , L cand h c respectively the longitude, latitude and altitude of the ground target; λ, L and h respectively the longitude, latitude and altitude of the carrier in real time; R N and R M respectively the meridian and prime vertical radii of curvature at the location of the target; x A denotes the eastward distance from the reference origin when the carrier is in the leg A, y A denotes the northward distance from the reference origin when the carrier is in the leg A, x B denotes the eastward distance from the reference origin when the carrier is in the leg B, y B denotes the northward distance from the reference origin when the carrier is in the leg B, x C denotes the eastward distance from the reference origin when the carrier is in the leg C, y C denotes the northward distance from the reference origin when the carrier is in the leg C, x D denotes the eastward distance from the reference origin when the carrier is in the leg D, y D denotes the northward distance from the reference origin when the carrier is in the leg D.

[0052] Step 2, target pointing guidance: read the carrier position, attitude and target position information, calculate the target pointing in the carrier body coordinate system according to the following formula

[0053]

[0054] wherein, is the carrier position matrix, determined by the carrier longitude and latitude (λ, L):

[0055]

[0056] is the carrier attitude matrix, determined by the carrier attitude angles (ψ, θ, γ):

[0057]

[0058] and are respectively the carrier and target Cartesian coordinate vectors, determined by their spherical coordinates longitude, latitude and altitude:

[0059]

[0060] wherein, R Na denotes the prime vertical radius of curvature at the location of the carrier, L a denotes the carrier latitude, λ a denotes the carrier longitude, h a denotes the carrier altitude, R Nm denotes the prime vertical radius of curvature at the location of the target, L mdenotes the target latitude, λ m denotes the target longitude, h m denotes the target altitude, e denotes the earth flattening.

[0061] The azimuth frame position driving command ψ of the photoelectric system when the line-of-sight points to the target is calculated according to the following formula cmd and the pitch frame position driving command θ cmd :

[0062]

[0063] wherein atan2 denotes the inverse tangent function, asin denotes the inverse sine function, and respectively denote the three-dimensional components of the target pointing .

[0064] The line-of-sight is made to point to the target under the action of the position driving commands, and after being driven to the position, the line-of-sight is further controlled to accurately track the target through the vernier.

[0065] Step 3, target positioning in the flight section A: when the aircraft flies to the flight section A, the known target is positioned, and the positioning error expression is as follows:

[0066]

[0067] wherein δλ a , δL a , δh a respectively denote the longitude error, the latitude error and the altitude error of the target positioning when the aircraft is in the flight section A; R am denotes the distance of the target relative to the aircraft when the aircraft is in the center of the flight section A, θ am denotes the pitch angle of the target relative to the aircraft when the aircraft is in the center of the flight section A; Δψ, Δθ, Δγ respectively denote the true values of the azimuth installation error, the pitch installation error and the roll installation error of the photoelectric system relative to the aircraft, and θ0 denotes the true value of the frame zero error of the photoelectric system to be calibrated.

[0068] Step 4, target positioning in the flight section B: when the aircraft flies to the flight section B, the known target is positioned, and the positioning error expression is as follows:

[0069]

[0070] wherein δλ b , δL b , δh b respectively denote the longitude error, the latitude error and the altitude error of the target positioning when the aircraft is in the flight section B; R bm denotes the distance of the target relative to the aircraft when the aircraft is in the center of the flight section B, θ bm denotes the pitch angle of the target relative to the aircraft when the aircraft is in the center of the flight section B.

[0071] Step 5, target positioning in leg C: when the aircraft flies to leg C, the known target is positioned, and its positioning error expression is:

[0072]

[0073] wherein, δλ c , δL c , δh c are the longitude error, latitude error and height error of the target positioning when the aircraft is in leg C, respectively; R cm is the distance of the target relative to the aircraft when the aircraft is in the center of leg C, and θ cm is the pitch angle of the target relative to the aircraft when the aircraft is in the center of leg C.

[0074] Step 6, target positioning in leg D: when the aircraft flies to leg D, the known target is positioned, and its positioning error expression is:

[0075]

[0076] wherein, δλ d , δL d , δh d are the longitude error, latitude error and height error of the target positioning when the aircraft is in leg D, respectively; R dm is the distance of the target relative to the aircraft when the aircraft is in the center of leg D, and θ dm is the pitch angle of the target relative to the aircraft when the aircraft is in the center of leg D.

[0077] Step 7, installation error calculation: when planning the flight path, make leg A and D the same observation position, and make leg B and C the same observation position, satisfying:

[0078]

[0079] The installation error of the photoelectric system is calculated as follows:

[0080]

[0081] wherein, and are the estimated values of the azimuth installation error, pitch installation error and roll installation error of the photoelectric system relative to the aircraft, respectively, is the estimated value of the zero position error of the photoelectric system frame.

Claims

1. A method for online airborne calibration of installation errors of airborne optoelectronic systems based on flight path constraints, characterized in that... The steps are as follows: Step 1, Flight trajectory planning: Based on the known ground target position (λ) c ,L c ,h c Using (x0, y0, z) as the reference origin, the x-axis points due east, the y-axis points due north, and the z-axis points to the sky along the perpendicular from the target point. The planned aircraft flies from west to east over the ground target from waypoint (x0, y0, z) to waypoint (x1, y1, z), then turns 180° left to waypoint (x2, y2, z), and continues flying from east to west to waypoint (x3, y3, z). The aircraft then adjusts its trajectory to return from waypoint (x3, y3, z) to waypoint (x4, y4, z). The length of segment A is 1 km, satisfying 9.5 km ≤ x A ≤10.5km,|y A |≤5m, track angle 90°; segment B satisfies -0.5km≤x B ≤0.5km, |y B -10km|≤5m, track angle -90°; segment C satisfies -0.5km≤x C ≤0.5km, |y C -10km|≤5m, track angle 90°; segment D satisfies 9.5km≤x D ≤10.5km, |y D |≤5m, track angle -90°; The coordinate scale of the aircraft's real-time position (λ, L, h) relative to the reference origin is calculated using the following formula: Where x, y, and z are the eastward, northward, and skyward distances of the aircraft's real-time position relative to the ground target, respectively; λ c L c and h c λ represents the longitude, latitude, and altitude of the ground target; L, λ, and h represent the real-time longitude, latitude, and altitude of the carrier aircraft; R N and R M These are the radii of curvature of the lateral and meridional circles at the ground target, respectively; x A This represents the eastward distance of the aircraft from the reference origin when it is in flight segment A. A x represents the northward distance from the reference origin when the aircraft is in flight segment A. B This represents the eastward distance of the aircraft from the reference origin when it is in flight segment B. B This represents the northward distance from the reference origin when the aircraft is in flight segment B, x. C This represents the eastward distance of the aircraft from the reference origin when it is in flight segment C. C This represents the northward distance from the reference origin when the aircraft is in flight segment C, x. D This indicates the eastward distance of the aircraft from the reference origin when it is in flight segment D. D This indicates the distance north of the reference origin when the aircraft is in flight segment D; Step 2, Target Pointing Guidance: Read the aircraft position, attitude, and target position information, and point the target in the computer's body coordinate system according to the following formula. in, The aircraft position matrix is ​​determined by the aircraft's longitude and latitude (λ, L); The aircraft attitude matrix is ​​determined by the aircraft attitude angles (ψ,θ,γ). and These are the rectangular coordinate vectors of the carrier aircraft and the target Earth, respectively, determined by their latitude, longitude, and altitude coordinates on the Earth's spherical surface. The following formula is used to calculate the position drive command ψ of the photoelectric system's azimuth frame when the line of sight points to the target. cmd and pitch frame position drive command θ cmd : Where atan2 represents the arctangent function and asin represents the arcsine function. and They represent the target directions respectively. The three-dimensional components; Under the action of the position drive command, the line of sight is pointed to the target, and after the drive is in place, the line of sight is further controlled by the vernier to accurately track the target; Step 3, Target localization for segment A: When the aircraft flies to segment A, it locates the known target. The localization error expression is as follows: Where, δλ a δL a δh a These represent the target positioning longitude error, latitude error, and altitude error when the aircraft is in flight segment A; R am θ represents the distance between the target and the aircraft when the aircraft is at the center of flight segment A. am Δψ, Δθ, and Δγ are the true values ​​of the azimuth, pitch, and roll installation errors of the electro-optical system relative to the aircraft when the aircraft is at the center of flight segment A, respectively; θ0 is the true value of the zero-position error of the electro-optical system frame to be calibrated. Step 4, Target localization for segment B: When the aircraft flies to segment B, it locates the known target. The localization error expression is as follows: Where, δλ b δL b δh b These represent the target positioning longitude error, latitude error, and altitude error when the aircraft is in flight segment B; R bm θ represents the distance between the target and the aircraft when the aircraft is at the center of flight segment B. bm The target's pitch angle relative to the carrier aircraft when the carrier aircraft is at the center of segment B; Step 5, Target localization in segment C: When the aircraft flies to segment C, it locates the known target. The localization error expression is as follows: Where, δλ c δL c δh c These represent the target positioning longitude error, latitude error, and altitude error when the aircraft is in flight segment C; R cm θ represents the distance between the target and the aircraft when the aircraft is at the center of flight segment C. cm The target's pitch angle relative to the aircraft when the aircraft is at the center of flight segment C; Step 6, Target localization in segment D: When the aircraft flies to segment D, it locates the known target. The localization error expression is as follows: Where, δλ d δL d δh d These are the expressions for the target positioning longitude error, latitude error, and altitude error when the aircraft is in flight segment D, respectively; R dm θ represents the distance between the target and the aircraft when the aircraft is at the center of flight segment D. dm The target's pitch angle relative to the aircraft when the aircraft is at the center of flight segment D; Step 7, Installation Error Calculation: When planning the flight path, ensure that segments A and D are at the same observation position, and segments B and C are at the same observation position, satisfying the following: The installation error of the optoelectronic system is calculated using the following formula: in, and The values ​​are, in order, estimated values ​​for the installation errors of the optoelectronic system relative to the carrier aircraft's azimuth, pitch, and roll relative to the aircraft. This is an estimate of the zero-position error of the optoelectronic system frame.

2. The method for online airborne calibration of installation errors of airborne optoelectronic systems based on flight path constraints as described in claim 1, characterized in that: The origin of the aforementioned body coordinate system is located at the center of gravity of the carrier, the x-axis points to the right of the aircraft's transverse axis, the y-axis points forward of the aircraft's longitudinal axis, and the z-axis satisfies the right-hand rule and is fixedly connected to the body.

3. The method for online airborne calibration of installation errors of an airborne optoelectronic system based on flight path constraints as described in claim 1, characterized in that: The carrier position matrix mentioned in step 2 according to It is determined by the longitude λ and latitude L of the carrier aircraft.

4. The method for online airborne calibration of installation errors of airborne optoelectronic systems based on flight path constraints as described in claim 1, characterized in that: The carrier aircraft attitude matrix mentioned in step 2 according to It is determined by the aircraft's heading angle ψ, pitch angle θ, and roll angle γ.

5. The method for online airborne calibration of installation errors of an airborne optoelectronic system based on flight path constraints as described in claim 1, characterized in that: The rectangular coordinate vectors of the carrier aircraft and the target Earth mentioned in step 2 and The calculation formulas are as follows: Among them, R Na L represents the radius of curvature of the Earth's circumference at the location of the aircraft. a Indicates the latitude of the carrier aircraft, λ a Indicates the longitude of the aircraft, h a R indicates the aircraft's altitude. Nm L represents the radius of curvature of the Earth's geoid at the location of the target. m Indicates the target latitude, λ m Indicates the target longitude, h m The value represents the target altitude, and 'e' represents the Earth's oblateness.

Images