Roll-pitch airborne photoelectric detection equipment overhead tracking method

Abstract

The invention relates to the technical field of photoelectric detection and tracking, in particular to a rolling-pitching airborne photoelectric detection equipment overhead tracking method, which comprises the following steps of: firstly judging whether an aiming line enters an overhead area or not in a tracking mode, if so, indicating that the aiming line enters the overhead area, otherwise, not executing the method; secondly, calculating an initial aiming line and an aiming line angular velocity when entering the overhead area; recalculating an aiming line rotation matrix with a time parameter; calculating an aiming line passing through the vertex and a rolling frame angle again; and finally, the rolling frame moves to the pre-estimated over-top position and waits for the aiming line to exit from the over-top area. After entering the overhead area, the stabilized platform tracks normally, but the roll frame is no longer driven by the azimuth frame.

Description

Technical Field

[0001] The invention relates to the technical field of photoelectric detection and tracking, and in particular to an overhead tracking method for a roll-pitch type airborne photoelectric detection device. Background Art

[0002] The roll-pitch airborne photoelectric detection equipment is an airborne ground-to-ground photoelectric detection system, which generally has a photoelectric imaging component, and its photoelectric imaging component can be used to search, identify and track targets.

[0003] The roll-pitch airborne photoelectric detection equipment uses a roll-pitch-azimuth three-axis universal ring frame to complete the line of sight pointing. The pitch-azimuth frame constitutes a two-axis stable platform, and the line of sight is stabilized by the inertial measurement unit installed in the stable platform. The roll frame is used as an outer frame and moves with the azimuth frame to ensure that the azimuth frame does not hit the mechanical limit.

[0004] However, when the pitch angle is close to 0 degrees, the roll axis and azimuth axis are close to vertical in front of the airborne optoelectronic detection device in the sighting line, that is, in the overhead area. The roll frame lacks the freedom to follow the azimuth frame, which will cause the pod to be out of control. Summary of the invention

[0005] The technical solution of the present invention aims at the problems existing in the existing overhead tracking technology, and proposes an overhead tracking method of the roll-pitch airborne photoelectric detection equipment of the line of sight angular velocity. The main idea of ​​the present invention is to linearly extrapolate the angular velocity of the line of sight tracking, predict the movement of the line of sight in the overhead area, and reversely solve it to the line of sight angle, so as to move the roll frame to the position out of the overhead area in advance.

[0006] The object of the present invention is to provide a roll-pitch type airborne photoelectric detection device overhead tracking method, comprising:

[0007] Step 1: In the tracking mode, determine whether the aiming line of the airborne photoelectric detection device enters the overhead area. If it enters the overhead area, execute step 2; otherwise, continue to execute step 1;

[0008] Step 2, calculating the initial aiming line and aiming line angular velocity entering the overhead area according to the frame angle and frame angular velocity at the moment of entering the overhead area;

[0009] Step 3, calculating the line of sight rotation matrix with time parameters according to the line of sight angular velocity;

[0010] Step 4: Estimate the aiming line and roll frame angle of the over-the-top area based on the angle motion relationship equation at the over-the-top moment;

[0011] Step 5: The roll frame moves to the estimated exit position and waits for the aiming line to exit the overhead area.

[0012] Step 6: After the aiming line enters the overhead area, the stabilized platform tracks normally, but the roll frame is no longer slaved to the azimuth frame;

[0013] Step 7: After the aiming line of the airborne photoelectric detection device leaves the overhead area, the roll frame is driven by the azimuth frame and returns to step 1 to make the next overhead judgment.

[0014] Preferably, in step one, the method for judging whether the aiming line of the airborne photoelectric detection device enters the overhead area is to compare the projection of the aiming line of the base system of the airborne photoelectric detection device in the rolling direction with the size of a threshold value η. When it is greater than the threshold value η, the aiming line enters the overhead area, otherwise it is not in the overhead area.

[0015] Preferably, the threshold value n is related to the range of the overhead angle, specifically:

[0016] η=cosμ

[0017] Where μ is the single-side vertex angle.

[0018] Preferably, in step 2, the calculation formula of the initial aiming line when entering the overhead area is:

[0019]

[0020] In the formula, los b0 Initial sighting line when tying the base over the top area;

[0021] The rotation matrix from the stable platform system to the base system is calculated based on the frame angle of the initial entry into the overhead area; los a0 Tie the sight line to stabilize the platform.

[0022] Preferably, in step 2, the calculation formula of the sighting line angular velocity is:

[0023]

[0024] In the formula, ψ, are the azimuth frame angle and angular velocity respectively;

[0025] θ, are the pitch frame angle and angular velocity respectively;

[0026] is the roll frame angular velocity.

[0027] Preferably, in step 3, the calculation formula of the sighting line rotation matrix with time parameters is:

[0028] C(t)=cos(|ω b |t)I+(1-cos(|ω b |t))nnT +sin(|ω b |t)n^

[0029] Where t is the time parameter;

[0030] ω b is the angular velocity vector ω of the line of sight b The amplitude of

[0031] I is the identity matrix;

[0032] n is the angular velocity vector ω of the line of sight b direction;

[0033] n^ is the anti-multiplication matrix formed by n;

[0034] n T is the transpose of n.

[0035] Preferably, in step 4, the angular motion relationship equation at the time of passing the top is specifically:

[0036]

[0037] In the formula, los bt The base system sight line is for the moment of passing the top;

[0038] los bt (1) for loss bt The component in the x direction, i.e., the projection of the base system sighting line in the rolling direction at the moment of passing the top;

[0039] Solving the above equation gives the non-zero time parameter t, which can be used to estimate the base system aiming line of sight los in the overhead region. bt .

[0040] Preferably, in step 4, the step of estimating the roll frame angle of the overhead area is:

[0041] First, calculate the first roll frame angle that passes through the vertex based on the frame coupling relationship:

[0042] φ bt 1=-atan(los bt (2),los bt (3))

[0043] In the formula, los bt (2),los bt (3) are the base system sighting line los at the time of passing the top bt Components in the y and z directions;

[0044] Next, calculate and φ bt1 The second roll frame angle out of the vertex is 180° different;

[0045]

[0046] Finally, φ bt 1. φ bt 2 Compared with the initial roll frame angle entering the overhead area, the value with the smallest angle difference is used as the estimated roll frame angle of the overhead area.

[0047] Preferably, before entering the overhead area, the stable platform composed of the pitch frame and the azimuth frame moves in a closed loop according to the tracking deviation, and the roll frame is driven by the azimuth frame to maintain the angle of the azimuth frame close to zero degrees; after entering the overhead area, the roll frame moves toward the roll frame angle estimated for the overhead area, and the stable platform composed of the pitch frame and the azimuth frame moves in a closed loop according to the tracking deviation; after exiting the overhead area, the control strategy before entering the overhead is restored.

[0048] The present invention has at least the following beneficial effects:

[0049] The present invention provides a method for overhead tracking of a roll-pitch airborne photoelectric detection device. The present invention can plan the frame movement in an overhead area in advance, so that the control system is always in a normal working state, the tracking error is controllable, and the continuity and stability of tracking are guaranteed when entering and exiting the overhead area. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A schematic diagram of the principle of the overhead tracking method of the roll-pitch airborne photoelectric detection equipment provided by the present invention.

[0051] Figure 2 A flow chart of an overhead tracking method for a roll-pitch airborne photoelectric detection device provided by the present invention. DETAILED DESCRIPTION

[0052] In order to illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following is a detailed description in conjunction with embodiments.

[0053] The base system in the present invention is defined as O as the rotation center of the three-axis universal ring frame of roll, pitch and azimuth, OX b Axis pointing to roll axis, OY b Vertical roll axis right, OZ b Perpendicular to the longitudinal axis of the roll-pitch airborne photoelectric detection equipment, it forms the "front right lower" base coordinate system OX b Y b Z b .

[0054] The stable platform of the present invention is defined as: the base OX b Yb Z b The coordinate system is obtained by rotating the frame angles around the roll axis, pitch axis and azimuth axis of the optoelectronic pod in sequence, and the positive direction of the x-axis is the visual axis of the optoelectronic pod.

[0055] The direction of the azimuth and elevation angle of the sighting line is determined by the base system OX b Y b Z b The direction is determined by the right hand.

[0056] The method provided by the present invention comprises the following steps:

[0057] Step 1: Before entering the overhead area, the stable platform composed of the pitch frame and the azimuth frame moves in a closed loop according to the tracking deviation, and the roll frame is driven by the azimuth frame to maintain the azimuth frame angle close to zero. In the tracking mode, determine whether the aiming line of sight of the airborne photoelectric detection equipment enters the overhead area. If it enters the overhead area, execute steps 2 and 6, otherwise return to step 1;

[0058] The method for judging whether the aiming line of the airborne photoelectric detection device enters the overhead area is to compare the projection of the aiming line of the base system of the airborne photoelectric detection device in the rolling direction with the size of the threshold η. When it is greater than the threshold η, the aiming line enters the overhead area, otherwise it is not in the overhead area.

[0059] The threshold η is related to the range of the overhead angle, specifically:

[0060] η=cosμ

[0061] Where μ is the single-sided top angle, which should not be greater than the maximum misalignment angle of the stable platform and should leave a certain margin.

[0062] Step 2, calculating the initial aiming line and aiming line angular velocity entering the overhead area according to the frame angle and frame angular velocity at the moment of entering the overhead area;

[0063] The formula for calculating the initial aiming line when entering the overhead area is:

[0064]

[0065] In the formula, los b0 Initial sighting line when tying the base over the top area;

[0066] The rotation matrix from the stable platform system to the base system is calculated based on the frame angle that initially enters the overhead region;

[0067] los a0 Tie the sight line to stabilize the platform.

[0068] The calculation formula of the angular velocity of the line of sight is:

[0069]

[0070] In the formula, ψ, is the azimuth frame angle and angular velocity;

[0071] θ, is the pitch frame angle and angular velocity;

[0072] is the roll frame angular velocity.

[0073] Step 3, calculating the line of sight rotation matrix with time parameters according to the line of sight angular velocity;

[0074] The calculation formula of the line of sight rotation matrix with time parameter is:

[0075] C(t)=cos(|ω b |t)I+(1-cos(|ω b |t))nn T +sin(|ω b |t)n^

[0076] Where t is the time parameter;

[0077] |ω b | is the angular velocity vector ω of the line of sight b The amplitude of

[0078] I is the identity matrix;

[0079] n is the angular velocity vector ω of the line of sight b direction;

[0080] n^ is the anti-multiplication matrix formed by n;

[0081] n T is the transpose of n.

[0082] Step 4: Estimate the aiming line and roll frame angle of the over-the-top area based on the angle motion relationship equation at the over-the-top moment;

[0083] The specific equation of the angular motion relationship at the time of passing the top is:

[0084]

[0085] In the formula, los bt The base system sight line is for the moment of passing the top;

[0086] los bt (1) for loss bt The component in the x direction, i.e., the projection of the base system sighting line in the rolling direction at the moment of passing the top;

[0087] Solving the above equation gives the non-zero time parameter t, which can be used to estimate the base system aiming line of sight los in the overhead region. bt .

[0088] The steps to estimate the roll frame angle of the overhead area are:

[0089] First, calculate the first roll frame angle that passes through the vertex based on the frame coupling relationship:

[0090] φ bt 1=-atan(los bt (2),los bt (3))

[0091] In the formula, los bt (2),los bt (3) are the base system sighting line los at the time of passing the top bt Components in the y and z directions;

[0092] Next, calculate and φ bt 1 The second roll frame angle out of the vertex is 180° different;

[0093]

[0094] Finally, φ bt 1. φ bt 2 Compared with the initial roll frame angle entering the overhead area, the value with the smallest angle difference is used as the estimated roll frame angle of the overhead area.

[0095] Step 5: The roll frame moves to the estimated exit position and waits for the aiming line to exit the overhead area.

[0096] Step 6: After the aiming line enters the overhead area, the stable platform tracks normally, but the roll frame is no longer slaved to the azimuth frame; the stable platform composed of the pitch frame and the azimuth frame performs closed-loop control according to the tracking image deviation;

[0097] Step 7: After the aiming line of the airborne photoelectric detection device leaves the over-the-top area, the control strategy before entering the over-the-top is restored. The roll frame is driven by the azimuth frame, and returns to step 1 to make the next over-the-top judgment.

[0098] In order to illustrate the overhead tracking method of a roll-pitch airborne photoelectric detection device provided by the present invention, it is further described in conjunction with the accompanying drawings.

[0099] See also Figure 1As shown, 101 is a roll-pitch airborne photoelectric detection device and its carrier, and 102 is the cone angle of the cone corresponding to the overhead area, that is, the overhead angle. The unilateral overhead angle should not be greater than the maximum misalignment angle of the stable platform and a certain margin should be left. For a preferred embodiment of the present invention, the maximum misalignment angle range of the stable platform is ±5°, the unilateral overhead angle is set to 4.5°, and the overhead angle is 9°, that is, the overhead area of ​​the preferred embodiment of the present invention is within a 9° cone directly in front of the sighting line of the base system.

[0100] Before entering the overhead area, the stable platform composed of the pitch frame and the azimuth frame moves in a closed loop according to the tracking deviation, and the roll frame is driven by the azimuth frame to maintain the angle of the azimuth frame close to zero. At a certain moment, the projection of the sight line 103 on the roll axis is just greater than the threshold η, indicating that it has entered the overhead area. The value of the threshold is the cosine of the unilateral overhead angle. When it is greater than the projection of the sight line on the roll axis is greater than the threshold η, for a preferred embodiment of the present invention, the unilateral overhead angle is 4.5°, then the threshold η is

[0101] η=cosμ=0.9969

[0102] The aiming line 103 is the initial aiming line for entering the overhead area. The initial aiming line and the aiming line angular velocity 104 for entering the overhead area are calculated according to the frame angle and frame angular velocity at the time of entering the overhead area:

[0103]

[0104] In the formula, ψ, is the azimuth frame angle and angular velocity;

[0105] θ, is the pitch frame angle and angular velocity;

[0106] is the roll frame angular velocity.

[0107] Given the angular velocity, multiply it by time to get the rotation vector, and then substitute it into the Rodriguez formula to get the line of sight rotation matrix related to the time parameter:

[0108] C(t)=cos(|ω b |t)I+(1-cos(|ω b |t))nn T +sin(|ω b |t)n^

[0109] Where t is the time parameter;

[0110] |ω b | is the angular velocity vector ω of the line of sight b The amplitude of

[0111] I is the identity matrix;

[0112] n is the angular velocity vector ω of the line of sight b direction;

[0113] n^ is the anti-multiplication matrix formed by n;

[0114] n T is the transpose of n.

[0115] After t time, the aiming line moves to the 105 position in the overhead area. According to the initial aiming line and the aiming line rotation matrix, the aiming line at the 105 position satisfies the following equation:

[0116] los bt =C(t)los b0

[0117] At position 105, the aiming line is still in the over-the-top area, so the following relationship is satisfied:

[0118] los bt (1) = η

[0119] In the formula, los bt The base is aimed at the moment of passing the top.

[0120] By combining the above two equations, the aiming line angle of the overhead area can be estimated. And the corresponding roll frame angle can be calculated by further calculating the aiming line angle of the overhead area. For roll-pitch airborne photoelectric detection equipment, since the pitch frame can move in both positive and negative directions, the overhead area corresponds to two roll frame angles, and the difference between the two roll frame angles is 180°, and the corresponding pitch frame angles are opposite in sign. Therefore, the first roll frame angle is calculated first:

[0121] φ bt 1=-atan(los bt (2),los bt (3))

[0122] Next, calculate and φ bt 1 The second roll frame angle out of the vertex is 180° different;

[0123]

[0124] Finally, φ bt 1. φ bt2Compared with the roll frame angle when entering the overhead area, the value with the smallest angle difference is used as the estimated roll frame angle of the overhead area. The advantage of this is that the roll rotation angle is minimized, ensuring that the roll can rotate to the specified position at the fastest speed when flying over the top at a high speed. After entering the overhead area, the roll frame moves in accordance with the roll frame angle estimated for the overhead area, and the stable platform composed of the pitch frame and azimuth frame moves in a closed loop according to the tracking deviation; after leaving the overhead area, the control strategy before entering the overhead is restored.

[0125] In order to further illustrate the specific embodiments of the present invention, Figure 2 The process of the present invention is described in detail.

[0126] Step 200, when the airborne photoelectric detection device is in tracking mode and before entering the overhead area, the stable platform composed of the pitch frame and the azimuth frame moves in a closed loop according to the tracking deviation, and the roll frame is driven by the azimuth frame to maintain the azimuth frame angle close to zero degrees;

[0127] Step 201, determining whether the aiming line of the airborne photoelectric detection device enters the overhead area, if so, executing step 202 and step 6, otherwise returning to executing step 208;

[0128] The method for judging whether the aiming line of the airborne photoelectric detection device enters the overhead area is to compare the projection of the aiming line of the base system of the airborne photoelectric detection device in the rolling direction with the size of the threshold η. When it is greater than the threshold η, the aiming line enters the overhead area, otherwise it is not in the overhead area.

[0129] The threshold η is related to the range of the overhead angle, specifically:

[0130] η=cosμ

[0131] Wherein, μ is the unilateral pass angle, which should not be greater than the maximum misalignment angle of the stable platform and leave a certain margin. For a preferred embodiment of the present invention, the maximum misalignment angle range of the stable platform is ±5°, the unilateral pass angle is set to 4.5°, and the pass angle is 9°, that is, the line of sight of the base system is within a 9° cone directly in front of the pass area of ​​the preferred embodiment of the present invention.

[0132] Step 202, calculating the initial aiming line entering the overhead area according to the frame angle at the time of entering the overhead area;

[0133] The formula for calculating the initial aiming line when entering the overhead area is:

[0134]

[0135] In the formula, los b0 Initial sighting line when tying the base over the top area;

[0136] The rotation matrix from the stable platform system to the base system is calculated based on the frame angle that initially enters the overhead region;

[0137] los a0 Tie the sight line to stabilize the platform.

[0138] Step 203, calculating the angular velocity of the line of sight entering the overhead area according to the frame angle and frame angular velocity at the time of entering the overhead area; the calculation formula of the angular velocity of the line of sight is:

[0139]

[0140] In the formula, ψ, is the azimuth frame angle and angular velocity;

[0141] θ, is the pitch frame angle and angular velocity;

[0142] is the roll frame angular velocity.

[0143] Step 204, calculate the line of sight rotation matrix with time parameters according to the line of sight angular velocity; the specific algorithm is to multiply the known angular velocity by time to obtain the rotation vector, and then substitute it into the Rodriguez formula to obtain the line of sight rotation matrix with relevant time parameters:

[0144] C(t)=cos(|ω b |t)I+(1-cos(|ω b |t))nn T +sin(|ω b |t)n^

[0145] Where t is the time parameter;

[0146] |ω b | is the angular velocity vector ω of the line of sight b The amplitude of

[0147] I is the identity matrix;

[0148] n is the angular velocity vector ω of the line of sight b direction;

[0149] n^ is the anti-multiplication matrix formed by n;

[0150] n T is the transpose of n.

[0151] Step 205, based on the angle motion relationship equation at the time of passing the top, estimate the aiming line of the top area; the angle motion relationship equation at the time of passing the top is specifically:

[0152]

[0153] In the formula, los bt It is the angle of the base system sight line at the moment of passing the top;

[0154] los bt (1) It is the projection of the base system sighting line in the rolling direction at the moment of passing the top.

[0155] Solving the above equation gives the non-zero time parameter t, which can be used to estimate the base system aiming line of sight los in the overhead region. bt .

[0156] The basic principle of this step is that after the initial moment of the overhead area, t time has passed and the aiming line becomes lo bt =C(t)los b0 If the position is out of the top area, then it should also satisfy the loss bt (1)=η.

[0157] After the two equations are combined and eliminated, a transcendental equation about time t is obtained. The numerical solution can be obtained by numerical method or the universal formula can be used to convert it into a quadratic algebraic equation to obtain an exact solution. The solution of t = 0 is the initial time of entering the over-the-top region and should be discarded.

[0158] Step 206, calculating the roll frame angle of the over-the-top area according to the aiming line of the over-the-top area; the steps of calculating the roll frame angle of the over-the-top area are:

[0159] First, calculate the first roll frame angle that passes through the vertex based on the frame coupling relationship:

[0160] φ bt 1=-atan(los bt (2),los bt (3))

[0161] Next, calculate and φ bt 1 The second roll frame angle out of the vertex is 180° different;

[0162]

[0163] Finally, φ bt 1. φ bt 2 Compared with the initial roll frame angle entering the overhead area, the value with the smallest angle difference is used as the estimated roll frame angle of the overhead area.

[0164] The reason for calculating two roll frame angles in this step is that for roll-pitch airborne photoelectric detection equipment, since the pitch frame can move in both positive and negative directions relative to 0 degrees straight ahead, the sight line in the overhead area corresponds to two sets of roll and pitch frame angles, where the two roll frame angles differ by 180°, and the corresponding pitch frame angles are opposite in sign. These two sets of roll and pitch frame angles can complete the same sight line pointing. bt 1. φ bt 2 Compared with the roll frame angle when entering the overhead area initially, the value with the smallest angle difference is used as the estimated roll frame angle in the overhead area to minimize the roll frame rotation angle, ensuring that the roll can rotate to the specified position at the fastest speed when flying overhead at a high speed.

[0165] In step 207, the roll frame moves to the estimated exit overhead position and waits for the aiming line to exit the overhead area, and then enters step 209; this step can adopt a direct closed-loop method to control the roll frame, and a speed feed-forward method can be adopted according to the angle to ensure the rapidity of the roll frame in place.

[0166] Step 208, after the aiming line enters the overhead area, the stabilized platform tracks normally, but the roll frame is no longer slaved to the azimuth frame; the stabilized platform composed of the pitch frame and the azimuth frame performs closed-loop control according to the tracking image deviation; because the unilateral overhead angle in the overhead area is not greater than the maximum misalignment angle of the stabilized platform and a certain margin is left, even if the roll frame is not slaved to the azimuth frame, the stabilized platform can track the target normally in the overhead area without colliding with the limit.

[0167] Step 209, determine whether the aiming line has exited the overhead area. If so, proceed to step 210; otherwise, return to step 208, the roll frame maintains its position unchanged, and the stable platform continues to track the target.

[0168] Step 210, after the aiming line of the airborne photoelectric detection device leaves the over-the-top area, the control strategy before entering the over-the-top is restored, the roll frame is driven by the azimuth frame, and the process returns to step 201 to determine the next over-the-top.

[0169] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A roll-pitch airborne photoelectric detection device overhead tracking method, characterized in that: include: Step 1: In the tracking mode, determine whether the aiming line of the airborne photoelectric detection device enters the overhead area. If it enters the overhead area, execute step 2; otherwise, continue to execute step 1; Step 2, calculating the initial aiming line and aiming line angular velocity entering the overhead area according to the frame angle and frame angular velocity at the moment of entering the overhead area; Step 3, calculating the line of sight rotation matrix with time parameters according to the line of sight angular velocity; Step 4: Estimate the aiming line and roll frame angle of the over-the-top area based on the angle motion relationship equation at the over-the-top moment; Step 5: The roll frame moves to the estimated exit position and waits for the aiming line to exit the overhead area. Step 6: After the aiming line enters the overhead area, the stabilized platform tracks normally, but the roll frame is no longer slaved to the azimuth frame; Step 7: After the aiming line of the airborne photoelectric detection device leaves the overhead area, the roll frame is driven by the azimuth frame and returns to step 1 to make the next overhead judgment.

2. The overhead tracking method of a roll-pitch airborne photoelectric detection device according to claim 1, characterized in that: In step one, the method for judging whether the aiming line of the airborne photoelectric detection device enters the overhead area is to compare the projection of the aiming line of the base system of the airborne photoelectric detection device in the rolling direction with the size of the threshold η. When it is greater than the threshold η, the aiming line enters the overhead area, otherwise it is not in the overhead area.

3. The overhead tracking method of a roll-pitch airborne photoelectric detection device according to claim 2, characterized in that: The threshold η is related to the range of the overhead angle, specifically: η=cosμ Where μ is the single-side vertex angle.

4. The overhead tracking method of a roll-pitch airborne photoelectric detection device according to claim 1, characterized in that: In step 2, the calculation formula for the initial aiming line when entering the overhead area is: In the formula, los b0 Initial sighting line when tying the base over the top area; The rotation matrix from the stable platform system to the base system is calculated based on the frame angle of the initial entry into the overhead area; los a0 Tie the sight line to stabilize the platform.

5. The overhead tracking method of a roll-pitch airborne photoelectric detection device according to claim 1, characterized in that: In step 2, the calculation formula of the angular velocity of the line of sight is: In the formula, ψ, are the azimuth frame angle and angular velocity respectively; θ, are the pitch frame angle and angular velocity respectively; is the roll frame angular velocity.

6. The overhead tracking method of a roll-pitch airborne photoelectric detection device according to claim 1, characterized in that: In step 3, the calculation formula of the aiming line rotation matrix with time parameters is: C(t)=cos(|ω b |t)I+(1-cos(|ω b |t))nn T +sin(|ω b |t)n^ Where t is the time parameter; |ω b | is the angular velocity vector ω of the line of sight b The amplitude of I is the identity matrix; n is the angular velocity vector ω of the line of sight b direction; n^ is the anti-multiplication matrix formed by n; n T is the transpose of n.

7. The overhead tracking method of a roll-pitch airborne photoelectric detection device according to claim 1, characterized in that: In step 4, the angle motion relationship equation at the time of passing the top is specifically: In the formula, los bt The base system sight line is set for the moment of passing the top; los bt (1) for loss bt The component in the x direction, i.e., the projection of the base system sighting line in the rolling direction at the moment of passing the top; Solving the above equation gives the non-zero time parameter t, which can be used to estimate the base system aiming line of sight los in the overhead region. bt .

8. The overhead tracking method of a roll-pitch airborne photoelectric detection device according to claim 1, characterized in that: In step 4, the steps to estimate the roll frame angle of the overhead area are: First, calculate the first roll frame angle that passes through the vertex based on the frame coupling relationship: φ bt 1=-atan(los bt (2),loose bt (3)) In the formula, los bt (2),los bt (3) are the base system sighting line los at the time of passing the top bt Components in the y and z directions; Next, calculate and φ bt 1 The second roll frame angle out of the vertex is 180° different; Finally, φ bt 1. φ bt 2 Compared with the initial roll frame angle entering the overhead area, the value with the smallest angle difference is used as the estimated roll frame angle of the overhead area.

9. The overhead tracking method of a roll-pitch airborne photoelectric detection device according to claim 1, characterized in that: Before entering the over-the-top area, the stable platform composed of the pitch frame and the azimuth frame moves in a closed-loop according to the tracking deviation, and the roll frame is driven by the azimuth frame to maintain the azimuth frame angle close to zero; after entering the over-the-top area, the roll frame moves toward the roll frame angle estimated in the over-the-top area, and the stable platform composed of the pitch frame and the azimuth frame moves in a closed-loop according to the tracking deviation; after leaving the over-the-top area, the control strategy before entering the over-the-top is restored.

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