A method for calibrating laser optical axis deviation by target positioning in the air

Abstract

A method for calibrating the deviation of the laser optical axis by positioning the target in the air. The invention relates to the field of error calibration of optoelectronic pods, and specifically to the technical field of a method for calibrating the deviation of the laser optical axis by positioning the target in the air. The present invention searches for appropriate target positioning information to infer the deviation of the laser optical axis. The method comprises the following steps: installing the pod on an aircraft and adjusting relevant configurations; obtaining a target data set with a target height not exceeding 1 meter as a search threshold; performing continuous laser ranging positioning on the target data set to obtain a ranging data set; calculating the true latitude and longitude of the target through the ranging data set; and inferring the deviation of the laser optical axis based on the true latitude and longitude of the target. The method of the present invention overcomes the problem that traditional methods cannot be applied to small optoelectronic pods, and is not subject to interference from other complex factors, so that it can be stably applied to various optoelectronic pods, and ultimately obtains satisfactory correction results.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectric pod error calibration, and in particular to the technical field of a method for calibrating laser optical axis deviation by target positioning in the air. Background Art

[0002] When using electro-optical pods for target positioning and laser guidance, the optical axis of the pod's laser must be aligned with the camera's boresight to ensure the accuracy of these functions. However, during ground assembly and flight, factors such as the assembly process and mechanical vibration during flight can cause the laser optical axis to deviate. Existing calibration methods use specific wavelength bands within the pod to monitor the laser spot and adjust the optical axis. This method is unsuitable for small pods, as they lack the space to accommodate payloads that receive specific wavelengths. For large and medium-sized pods, this method also requires consideration of complex factors such as the geometric characteristics of the spot distribution and the consistency of the boresight between different wavelength bands, limiting its robustness in practical applications. To meet the precision requirements of key electro-optical pod functions such as target positioning and laser guidance, a method is urgently needed to accurately calibrate the laser optical axis deviation in a short period of time during flight, without the need for additional equipment or payloads, and without excessive human intervention. Summary of the Invention

[0003] To address the problems of existing calibration methods being unsuitable for small optoelectronic pods and limited robustness, this paper proposes a method for calibrating laser optical axis deviation in mid-air by using target positioning. By searching for appropriate target positioning information, the laser optical axis deviation can be inferred.

[0004] The method comprises the following steps:

[0005] S1. Install the pod on the aircraft and adjust the relevant configurations;

[0006] S2, taking the target height no more than 1 meter as the search threshold, and obtaining the target data set;

[0007] S3, performing continuous laser ranging positioning on the target data set to obtain a ranging data set;

[0008] The distance measurement data set includes: aircraft inertial navigation position data , aircraft inertial navigation attitude data , attitude data of the pod encoder and laser data ,in, 、 、 、 、 、 、 、 and Respectively represent Aircraft latitude, longitude, altitude, heading, pitch, roll, encoder azimuth, encoder pitch, and laser ranging value at each moment;

[0009] S4. Calculate the target's true latitude and longitude using the ranging data set ;

[0010] The real latitude and longitude of the target are calculated by the ranging data set Specifically:

[0011] S41, initialize the target's real latitude and longitude high setting value , The value of is randomly set by those skilled in the art;

[0012] S42, the aircraft latitude and longitude at each moment 、 The geographic coordinates of the target aligned with the visible light axis in the geodetic rectangular coordinate system Calculate the spatial pointing angle of the pod relative to the target at each moment , the specific calculation formula is:

[0013] ;

[0014] ;

[0015]

[0016] ;

[0017] in, represents the radius of curvature of the earth's ellipsoid. Indicates the first eccentricity of the Earth;

[0018] S43. Calculate the actual spatial pointing angle of the pod relative to the target using the ranging data set. , the specific calculation formula is:

[0019] ;

[0020] ;

[0021] S44. Set optimization function ,in, , Indicates the total time of laser firing. Indicates the time;

[0022] S45. Minimize optimization function ,get The optimal value of

[0023] S46, according to The optimal value of , combined with the calculation formula of step S42, is used to infer the true latitude and longitude , that is, when When taking the minimum value, ;

[0024] S5. According to the actual latitude and longitude of the target, reverse the laser optical axis deviation ;

[0025] According to the actual latitude and longitude of the target, the laser optical axis deviation is reversed Specifically:

[0026] S51. Set the passive positioning function: ,in, represents the focal length of the camera, represents the initial laser optical axis deviation, The value of is randomly set by those skilled in the art;

[0027] S52. Set optimization function ,in, Indicates the target distance at the current moment, ,in, Indicates the latitude and longitude of the target that the laser optical axis is actually aiming at. Indicates time The aircraft is high in latitude and longitude;

[0028] S53, when When it converges to the minimum value, we get The optimal value of

[0029] S54, according to The optimal value of The optimal value of

[0030] Combine The optimal value of and passive positioning function are used to infer the laser optical axis deviation , that is, when When it converges to the minimum .

[0031] Furthermore, the adjustment-related configuration includes:

[0032] Timing alignment between the aircraft inertial navigation and the various sensors inside the pod;

[0033] Leveling between the aircraft inertial navigation reference plane and the pod boresight zero position;

[0034] Measure and correct the zero position error of the pod encoder.

[0035] Furthermore, the target height is calculated by the formula: Calculate, where Indicates the target height, Indicates the number of pixels that the target occupies on the vertical axis of the current search image. Indicates the height of the current search image. Indicates the current search image field angle, Indicates the pseudorange value to the ground in the current search area;

[0036] The target dataset has no more than .

[0037] further, The calculation formula is:

[0038]

[0039] in, Indicates the true latitude and longitude of the image center.

[0040] The beneficial effects of the method of the present invention are:

[0041] The method described in this paper, which uses target positioning to calibrate laser optical axis deviation, overcomes the limitations of traditional methods (which require monitoring the laser spot with a payload capable of receiving a specific wavelength band to calibrate the optical axis) for small optoelectronic pods. Furthermore, due to its simplicity, its lack of interference from other complex factors, and its ability to be completed quickly during flight, it can be stably applied to various optoelectronic pods, ultimately achieving satisfactory calibration results. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a flow chart of the method described in an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0044] This embodiment provides a method for calibrating the laser optical axis deviation by positioning a target in the air. The flowchart of the method is as follows: Figure 1 , the method comprises the following steps:

[0045] S1. Install the pod on the aircraft and adjust the relevant configurations:

[0046] Complete the timing alignment between the aircraft inertial navigation and the various sensors inside the pod;

[0047] Complete the leveling between the aircraft inertial navigation reference plane and the pod boresight zero position;

[0048] Measure and correct the zero position error of the pod encoder.

[0049] S2. Search for a suitable target dataset when the aircraft is in a stable flight state. The pixel size of each target in the target dataset does not exceed 50×50, and the target height is as small as possible, preferably not exceeding 1m.

[0050] The target height is calculated using the formula: Calculate, where Indicates the target height, Indicates the number of pixels that the target occupies on the vertical axis of the current search image. Indicates the height of the current search image. Indicates the current search image field angle, Indicates the pseudorange value to the ground in the current search area;

[0051] S3. Perform continuous laser ranging and positioning on the target in the target data set, and collect the aircraft inertial navigation, encoder and laser data during this process. Perform continuous laser ranging and positioning on the target data set for 3 to 5 minutes to obtain the ranging data set: aircraft inertial navigation position data , aircraft inertial navigation attitude data , attitude data of the pod encoder and laser data ,in, 、 、 、 、 、 、 、 and Respectively represent The aircraft latitude, longitude, altitude, heading, pitch, roll, encoder azimuth, encoder pitch and laser ranging value at each moment.

[0052] S4. Calculate the target's true latitude and longitude using the ranging data set (using the intersection measurement method) :

[0053] S41. Initialize the target's true latitude, longitude, and altitude ,get , The value of is randomly set by those skilled in the art according to the calibration requirements;

[0054] S42, the aircraft latitude and longitude at each moment 、 The geographic coordinates of the target aligned with the visible light axis in the geodetic rectangular coordinate system Calculate the spatial pointing angle of the pod relative to the target at each moment , the specific calculation formula is shown in formulas (1) to (4):

[0055]

[0056]

[0057]

[0058] in, represents the radius of curvature of the earth's ellipsoid. Indicates the first eccentricity of the Earth;

[0059] S42. Calculate the actual spatial pointing angle of the pod relative to the target using the ranging data set. , the specific calculation formulas are shown in formulas (5) and (6):

[0060]

[0061]

[0062] S43, Setting Optimization Letter:

[0063] in, , Indicates the total time of laser firing. Indicates the time;

[0064] S44. Minimize optimization function ,get The optimal value of

[0065] S45, will Substitute the optimal value of into formula (1) and (2) again, and we can infer The optimal value of

[0066] Will The optimal value of is substituted into formula (4) again to infer the true latitude and longitude height , that is, when When taking the minimum value, .

[0067] S5. According to the actual latitude and longitude of the target, reversely calculate the laser optical axis deviation:

[0068] Applying the passive geolocation algorithm based on the earth ellipsoid model, we first assume that the pixel offset is ,in is the horizontal axis offset pixel, To offset the vertical axis pixel, initialize the laser optical axis deviation (pixel offset), and get And substitute it into the passive positioning function:

[0069] Among them, The value of is randomly set by those skilled in the art according to the calibration requirements. is the focal length of the camera, which is used to calculate the geographic coordinates of the actual aiming point of the laser optical axis at this moment , and substitute it into formula (9) to solve the geographic coordinates of the target aimed by the assumed laser optical axis in the geodetic rectangular coordinate system :

[0070]

[0071] Set the optimization function:

[0072] in, Represents the target distance at the current moment, and the calculation formula is shown in formula (11):

[0073]

[0074] in, It represents the latitude and longitude of the target actually aimed at by the laser optical axis. The calculation formula is shown in formula (12):

[0075]

[0076] Indicates time The aircraft's latitude and longitude are high; when When it converges to the minimum value, we get The optimal value of

[0077] Will Substitute the optimal value of into formula (11) again and inversely deduce The optimal value of

[0078] Will Substitute the optimal value of into formula (9) again and inversely deduce The optimal value of

[0079] Will The optimal value is substituted into formula (8) again to infer the laser optical axis deviation , that is, when When it converges to the minimum .

Claims

1. A method for calibrating laser optical axis deviation by target positioning in the air, characterized in that: The method comprises the following steps: S1. Install the pod on the aircraft and adjust the relevant configurations; S2, taking the target height no more than 1 meter as the search threshold, and obtaining the target data set; S3, performing continuous laser ranging positioning on the target data set to obtain a ranging data set; The distance measurement data set includes: aircraft inertial navigation position data , aircraft inertial navigation attitude data , attitude data of the pod encoder and laser data ,in, 、 、 、 、 、 、 、 and Respectively represent Aircraft latitude, longitude, altitude, heading, pitch, roll, encoder azimuth, encoder pitch, and laser ranging value at each moment; S4. Calculate the target's true latitude and longitude using the ranging data set ; The real latitude and longitude of the target are calculated by the ranging data set Specifically: S41, initialize the target's real latitude and longitude high setting value , The value of is randomly set by those skilled in the art; S42, the aircraft latitude and longitude at each moment 、 The geographical coordinates of the target aligned with the visible light axis in the geodetic rectangular coordinate system Calculate the spatial pointing angle of the pod relative to the target at each moment , the specific calculation formula is: ； ； ； in, represents the radius of curvature of the earth's ellipsoid. Indicates the first eccentricity of the Earth; S43. Calculate the actual spatial pointing angle of the pod relative to the target using the ranging data set. , the specific calculation formula is: ； ； S44. Set optimization function ,in, , Indicates the total time of laser firing. Indicates the time; S45. Minimize optimization function ,get of optimal value; S46, according to The optimal value of the real latitude and longitude is deduced by combining the calculation formula of step S42. , that is, when When taking the minimum value, ; S5. According to the actual latitude and longitude of the target, reverse the laser optical axis deviation ; According to the actual latitude and longitude of the target, the laser optical axis deviation is reversed Specifically: S51. Set the passive positioning function: ,in, represents the focal length of the camera, represents the initial laser optical axis deviation, The value of is randomly set by those skilled in the art; S52. Set optimization function ,in, Indicates the target distance at the current moment, ,in, Indicates the latitude and longitude of the target that the laser optical axis is actually aiming at. Indicates time The aircraft is high in latitude and longitude; S53, when When it converges to the minimum value, we get The optimal value of S54, according to The optimal value of The optimal value of Combine The optimal value of and passive positioning function are used to infer the laser optical axis deviation , that is, when When it converges to the minimum .

2. The method for calibrating the laser optical axis deviation by target positioning in the air according to claim 1, characterized in that: The adjustment-related configuration includes: Timing alignment between the aircraft inertial navigation and the various sensors inside the pod; Leveling between the aircraft inertial navigation reference plane and the pod boresight zero position; Measure and correct the zero position error of the pod encoder.

3. The method for calibrating the laser optical axis deviation by target positioning in the air according to claim 2, characterized in that: The target height is given by the formula: Calculate, where Indicates the target height, Indicates the number of pixels that the target occupies on the vertical axis of the current search image. Indicates the height of the current search image. Indicates the current search image field of view, Indicates the pseudorange value to the ground in the current search area; The target dataset has no more than .

4. The method for calibrating laser optical axis deviation by target positioning in the air according to claim 1, characterized in that: The calculation formula is: in, Indicates the true latitude and longitude of the image center.

Images