CN118603141A - A method for pod system error calibration without knowing the ground position - Google Patents

Abstract

The present invention proposes a pod system error calibration method without the need for a known ground position. It belongs to the technical field of optoelectronic pod error calibration. The method includes step one, pod installation and timing alignment, step two, starting image tracking for any target, step three, obtaining multiple sets of spatial pointing angle errors, and step four, calculating the attitude angle compensation value. The method solves the limitation of previous methods that some means are needed to extract and obtain the precise geographical location of the ground target point, and at the same time, it does not require the participation of complex detour routes and laser ranging, which greatly improves the convenience, timeliness and concealment of pod error calibration during flight, and provides support for subsequent high-precision target positioning and geographic guidance and tracking functions during the current flight. It not only greatly reduces the difficulty of calibration and the complexity of the process, but also brings great convenience to practical applications.

Description

A method for pod system error calibration without knowing the ground position

Technical Field

The invention belongs to the technical field of photoelectric pod error calibration, and in particular relates to a pod system error calibration method without the need to know the ground position.

Background Art

When an airborne optoelectronic pod locates or geographically guides a ground target, the system error (generally speaking, the installation error between the aircraft and the pod and the zero position error of the pod optical axis) has a great impact on the accuracy. The methods used in the past, such as using GPS differential equipment or satellite maps of the corresponding area to obtain the precise geographical location information of the ground target points to be observed during the flight in advance, locating the calibrated ground target points when the aircraft flies on a planned complex detour route, and obtaining the system error by comparing with the true value, all require the accurate geographical location information of the known target points to be collected in advance, and supplemented by the corresponding detour route. This type of method requires auxiliary work to be completed before the pod is installed on the aircraft and begins to perform the mission, including carrying equipment to go specifically or collecting satellite maps to calibrate the target points, planning detour routes, etc., so the convenience and timeliness are poor. In addition, most of the solutions in the previous methods require the participation of laser ranging, which also easily exposes the position of the aircraft during flight and does not meet the needs of covert flight. Considering the above problems, there is an urgent need for an optoelectronic pod system error calibration method that does not require a known ground target position, a complex detour route, and laser ranging.

Summary of the invention

The purpose of the present invention is to solve the problem that the previous methods require complex route planning and long-term observation and data collection, and propose a pod system error calibration method without knowing the ground position.

The present invention is implemented by the following technical scheme. The present invention proposes a pod system error calibration method without knowing the ground position, and the method comprises the following steps:

Step 1: Pod installation and timing alignment: Install the pod on the aircraft's mounting base. Then, export the timestamp information of the aircraft's inertial navigation and pod encoders through the protocol to align the timing between the sensors.

Step 2: Enable image tracking for any target: When the aircraft is in a stable flight state, lock the pitch encoder to -30°, adjust the azimuth axis angle in sequence, and perform image tracking for any target in the field of view; after tracking the target for a certain period of time, lock the pitch encoder to -60°, adjust the encoder azimuth according to the angle, and perform image tracking for any target in the field of view;

Step 3: Obtain multiple sets of spatial pointing angle errors: After completing multiple image tracking operations, multiple sets of spatial pointing angle errors are calculated using the aircraft inertial navigation position and attitude data, encoder angle data, and the pixel offset of the target in the current image relative to the first frame image. ,in, and Respectively represent The spatial azimuth pointing angle error and spatial pitch pointing angle error obtained by secondary image tracking;

Step 4: Calculate the attitude angle compensation value: Substitute the position attitude information of the aircraft inertial navigation and the pod encoder information during each image tracking, as well as the spatial pointing angle error, into the least squares program to obtain five attitude angle compensation values, and substitute them into the subsequent target positioning and geographic tracking solutions.

Furthermore, in step 2, the azimuth axis angles are adjusted in sequence to 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°.

Furthermore, the certain period of time is 5 minutes.

Furthermore, in step 2, when there is no suitable target for image tracking in the field of view after the encoder is rotated to the specified angle, the azimuth axis and pitch axis of the pod move ±1°, that is, to search for a suitable target in the eight adjacent field of view areas of the current field of view. If there is still no suitable target in the field of view after the movement, the image tracking operation is abandoned.

Furthermore, in step 3, after image tracking is turned on, the Lucas-Kanade optical flow method is used to obtain the pixel offset of the target and convert it into the angle of the encoder:

in, Indicates The time when the image is tracked The pixel offset of the target in the image at time θ relative to that in the image at time 0, and Indicates the width and height of the image. Indicates the field of view of the current image, Indicates the calculated angular offset.

Furthermore, in step 3, multiple sets of spatial pointing angle errors The calculation method is: When tracking any target, the position data of the aircraft inertial navigation , posture data , encoder angle data Angle offset data from the target Substitute it into the optimization function solving program to find the true value of the geographical location of the target tracked by this image In the above data, , , , , , , , , and Respectively represent The time when the image is tracked The aircraft's latitude, longitude, altitude, heading angle, pitch angle, roll angle, encoder azimuth angle, pitch angle, relative offset of the target on the x-axis and relative offset of the y-axis in the field of view.

Furthermore, in step three, a program with an optimization function is used to solve the true value of the geographic location of the target tracked by the image, specifically: construct an optimization function:

By solving Get the true value of the target of this image tracking, and calculate the error of the spatial pointing angle .

Furthermore, in step 4, the true latitude and longitude of the center of each image and the latitude and longitude of the aircraft at the same time are converted to coordinates in the geodetic coordinate system and subtracted to obtain the difference:

in, For the coordinate conversion from geographic coordinate system to geodetic rectangular coordinate system ECEF,

The heading component of the installation error between the aircraft and the pod , , , zero position error with the pod optical axis , Written into the corresponding matrix in the error calibration algorithm:

in, is the transformation matrix from the NEA coordinate system to the ECEF coordinate system, is the transformation matrix from the aircraft's body coordinate system to the north-east ground coordinate system, is the installation error matrix between the pod and the aircraft, substitute here , , ; is the transformation matrix from the pod coordinate system to the body coordinate system under ideal conditions, is the zero position error matrix of the optical axis inside the pod, substitute it here , ; The expression is:

in, represents the function cosine, Represents the function sin; further, using the following equation:

The following least squares formula is obtained through transformation:

in, and The equations are The input matrix and output vector of the sampled data after form conversion; the five required error angle values can be obtained through the above formula.

The present invention proposes an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of a pod system error calibration method without knowing the ground position are implemented.

The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of a pod system error calibration method without knowing the ground position.

Beneficial effects of the present invention:

The pod system error calibration method without the need for a known ground position solves the limitation of the previous method that the precise geographical location of the ground target point needs to be extracted by some means, and does not require the participation of complex detour routes and laser ranging, which greatly improves the convenience, timeliness and concealment of pod error calibration during flight, and provides support for subsequent high-precision target positioning, geographic guidance and tracking functions in the current flight. It not only greatly reduces the difficulty of calibration and the complexity of the process, but also brings great convenience to practical applications.

The method of the present invention can be applied in the field of error calibration of optoelectronic pods and the field of target positioning, geographic guidance and tracking of optoelectronic pods.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

FIG1 is a schematic diagram showing a pod rotating regularly and collecting images in a pod system error calibration method without knowing the ground position according to the present invention.

FIG2 is an overall flow chart of a pod system error calibration method without knowing the ground position described in the present invention.

DETAILED DESCRIPTION

The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

In conjunction with FIG. 1 and FIG. 2 , the present invention proposes a pod system error calibration method without knowing the ground position, the method comprising the following steps:

Step 1: Pod installation and timing alignment: Install the pod on the aircraft's mounting base. Then, export the timestamp information of the aircraft's inertial navigation and pod encoders through the protocol to align the timing between the sensors.

Step 2: Enable image tracking for any target: When the aircraft is in a stable flight state, lock the pitch encoder to -30°, adjust the azimuth axis angle in sequence, and perform image tracking for any target in the field of view; after tracking the target for a certain period of time, lock the pitch encoder to -60°, adjust the encoder azimuth according to the angle, and perform image tracking for any target in the field of view; in step 2, adjust the azimuth axis angle to 0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315° in sequence. The certain period of time is 5 minutes.

In step 2, when there is no suitable target for image tracking in the field of view after the encoder rotates to the specified angle, the azimuth axis and pitch axis of the pod move ±1°, that is, to search for a suitable target in the eight adjacent field of view areas of the current field of view. If there is still no suitable target in the field of view after the movement, the image tracking operation is abandoned.

Step 3: Obtain multiple sets of spatial pointing angle errors: After completing multiple image tracking operations, multiple sets of spatial pointing angle errors are calculated using the aircraft inertial navigation position and attitude data, encoder angle data, and the pixel offset of the target in the current image relative to the first frame image. ,in, and Respectively represent The spatial azimuth pointing angle error and spatial pitch pointing angle error obtained by secondary image tracking;

In step 3, after image tracking is turned on, the Lucas-Kanade optical flow method is used to obtain the pixel offset of the target and convert it into the angle of the encoder:

in, Indicates The time when the image is tracked The pixel offset of the target in the image at time θ relative to that in the image at time 0, and Indicates the width and height of the image. Indicates the field of view of the current image, Indicates the calculated angular offset.

In step 3, multiple sets of spatial pointing angle errors The calculation method is: When tracking any target, the position data of the aircraft inertial navigation , posture data , encoder angle data Angle offset data from the target Substitute it into the optimization function solving program to find the true value of the geographical location of the target tracked by this image In the above data, , , , , , , , , and Respectively represent The time when the image is tracked The aircraft's latitude, longitude, altitude, heading angle, pitch angle, roll angle, encoder azimuth angle, pitch angle, relative offset of the target on the x-axis and relative offset of the y-axis in the field of view.

In step 3, a program with an optimization function is used to solve the true value of the geographic location of the target tracked by the image. Specifically, an optimization function is constructed:

By solving Get the true value of the target of this image tracking, and calculate the error of the spatial pointing angle .

Step 4: Calculate the attitude angle compensation value: Substitute the position attitude information of the aircraft inertial navigation and the pod encoder information during each image tracking, as well as the spatial pointing angle error, into the least squares program to obtain five attitude angle compensation values, and substitute them into the subsequent target positioning and geographic tracking solutions.

In step 4, the true latitude and longitude of the center of each image and the latitude and longitude of the aircraft at the same time are converted to coordinates in the geodetic coordinate system and subtracted to obtain the difference:

in, For the coordinate conversion from geographic coordinate system to geodetic rectangular coordinate system ECEF,

The heading component of the installation error between the aircraft and the pod , , , zero position error with the pod optical axis , Written into the corresponding matrix in the error calibration algorithm:

in, is the transformation matrix from the NEA coordinate system to the ECEF coordinate system, is the transformation matrix from the aircraft's body coordinate system to the north-east ground coordinate system, is the installation error matrix between the pod and the aircraft, substitute here , , ; is the transformation matrix from the pod coordinate system to the body coordinate system under ideal conditions, is the zero position error matrix of the optical axis inside the pod, substitute it here , ; The expression is:

in, represents the function cosine, Represents the function sin; further, using the following equation:

The following least squares formula is obtained through transformation:

in, and The equations are The input matrix and output vector of the sampled data after form conversion; the five required error angle values can be obtained through the above formula.

The present invention proposes a pod system error calibration method without knowing the ground position. It includes the following steps: 1. Install the pod on the aircraft to complete the timing alignment between the aircraft inertial navigation and the pod encoder; 2. When the aircraft is in a stable flight state, rotate the pod visual axis according to a regular pattern to perform image tracking of any target in the field of view; 3. Through multiple image tracking, obtain the spatial pointing angle error during multiple image tracking ,in, and Respectively represent The spatial azimuth pointing angle error and spatial pitch pointing angle error obtained by multiple image tracking; Fourth, according to the position and attitude data of the aircraft inertial navigation and the pod encoder data during multiple image tracking, as well as the spatial pointing angle error data, substitute them into the least squares method to calculate the five attitude angles that need to be compensated , and substitute these five attitude angle compensation values into the target positioning and geographic tracking program. The present invention avoids the cumbersome conditional restrictions such as the need to accurately measure ground control points and plan a specific flight route in advance, or the need to prepare a high-precision satellite map database in advance in the previous methods. Without any known ground position information and calibration operations, the error calibration and correction of the aircraft and the pod, and multiple axis systems inside the pod can be completed in a short time when the aircraft is in a stable flight state, providing technical support for achieving accurate target positioning and geographic tracking in the subsequent process of the same flight.

The present invention proposes an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of a pod system error calibration method without knowing the ground position are implemented.

The present invention also proposes a computer-readable storage medium for storing computer instructions, which, when executed by a processor, implement the steps of a pod system error calibration method without knowing the ground position.

The memory in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read only memory (ROM), a programmable read only memory (PROM), an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchlink DRAM (SLDRAM), and direct rambus RAM (DR RAM). It should be noted that the memory of the method described in the present invention is intended to include, but is not limited to, these and any other suitable types of memory.

In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented by software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a digital video disc (DVD)), or a semiconductor medium (eg, a solid state disc (SSD)).

In the implementation process, each step of the above method can be completed by an integrated logic circuit of hardware in a processor or an instruction in the form of software. The steps of the method disclosed in conjunction with the embodiment of the present application can be directly embodied as a hardware processor for execution, or a combination of hardware and software modules in a processor for execution. The software module can be located in a storage medium mature in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor reads the information in the memory and completes the steps of the above method in conjunction with its hardware. To avoid repetition, it is not described in detail here.

It should be noted that the processor in the embodiment of the present application may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method embodiment can be completed by an integrated logic circuit of hardware in the processor or an instruction in the form of software. The above processor may be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The methods, steps and logic block diagrams disclosed in the embodiments of the present application can be implemented or executed. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc. The steps of the method disclosed in the embodiment of the present application may be directly embodied as being executed by a hardware decoding processor, or may be executed by a combination of hardware and software modules in a decoding processor. The software module may be located in a mature storage medium in the art such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in a memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.

The above is a detailed introduction to the pod system error calibration method proposed in the present invention that does not require a known ground position. This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims (10)

1. A method of calibrating error in a nacelle system without knowing the position of the ground, said method comprising the steps of:

Step one, pod installation and timing alignment: mounting the pod on the mounting base of the aircraft, and subsequently deriving time stamp information of the inertial navigation of the aircraft and the pod encoder by means of a protocol, thereby aligning the timing between the individual sensors;

Step two, image tracking is started for any target: when the aircraft is in a stable flight state, locking a pitching encoder to be-30 degrees, sequentially adjusting the azimuth axis angle, and carrying out image tracking on any target in a view field; after a target is tracked for a certain time, locking a pitching encoder to be-60 degrees, adjusting the azimuth of the encoder according to an angle, and performing image tracking operation on any target in a view field;

Step three, obtaining a plurality of groups of space pointing angle errors: after the image tracking operation is completed for a plurality of times, a plurality of groups of space pointing angle errors are calculated through the position and posture data of airplane inertial navigation, the angle data of an encoder and the pixel offset of a target in a current image relative to the first frame image Wherein, the method comprises the steps of, wherein,AndRespectively represent the firstA space azimuth pointing angle error and a space pitching pointing angle error obtained by secondary image tracking;

Step four, calculating to obtain an attitude angle compensation value: and substituting the position attitude information and pod encoder information of the airplane inertial navigation during each image tracking and the space pointing angle error into a least square method program to obtain five attitude angle compensation values, and substituting the five attitude angle compensation values into subsequent target positioning and geographic tracking calculation.

2. The method according to claim 1, wherein in step two, the azimuth axis angles are sequentially adjusted to 0 °, 45 °, 90 °, 135 °, 180 °, 225 °, 270 °, 315 °.

3. The method of claim 1, wherein the certain time is 5 minutes.

4. The method according to claim 1, wherein in the second step, when the encoder rotates to a specified angle and there is no suitable target for image tracking in the field of view, the nacelle azimuth axis and the pitch axis move ±1°, that is, a suitable target is found in the adjacent eight field of view areas of the current field of view, and if there is still no suitable target in the field of view after the movement, the image tracking operation is abandoned.

5. The method of claim 1, wherein in step three, after image tracking is turned on, the pixel offset of the target is obtained by Lucas-Kanade optical flow method and converted into the encoder angle:

Wherein, Represent the firstTime of day when secondary image trackingThe object in the image at time is offset relative to its pixels in the image at time 0,AndRepresenting the width and height of the image,Representing the angle of view of the current image,Representing the calculated angular offset.

6. The method of claim 5, wherein in step three, the plurality of sets of spatial pointing angle errorsThe calculation method of (1) is as follows: when the first isWhen any one target is tracked by image, the position data of airplane inertial navigation is obtainedAttitude dataAngle data of encoderAnd angular offset data of the targetSubstituting the true value into an optimization function solving program to obtain the true value of the geographic position of the target tracked by the image; In the above-mentioned data, the data,、、、、、、、、AndRespectively represent the firstTime of day when secondary image trackingAircraft latitude, longitude, altitude, heading angle, pitch angle, roll angle, encoder azimuth angle, pitch angle, relative offset of the target in the x-axis and relative offset of the target in the field of view.

7. The method according to claim 6, characterized in that in step three, the geographical position truth of the object tracked by the image is solved by means of a program with an optimization function, in particular: constructing an optimization function:

by solving for Obtaining true value of the target tracked by the image and simultaneously solving error of the space pointing angle。

8. The method according to claim 7, wherein in the fourth step, the true longitude and latitude of the center of each image and the longitude and latitude of the plane at the same time are converted to coordinates in the geodetic coordinate system and subtracted to obtain a difference value:

Wherein, For the coordinate conversion from the geographical coordinate system to the geodetic rectangular coordinate system ECEF,

Heading component of installation error of aircraft and nacelle、、Zero error with nacelle optical axis、Writing into corresponding matrixes in an error calibration algorithm:

Wherein, For the transformation matrix of the northeast coordinate system to the ECEF coordinate system,Is a transformation matrix from a machine body coordinate system of the airplane to a north east ground coordinate system,For the installation error matrix between the nacelle and the plane, substituted therein、、；Is a transformation matrix from a nacelle coordinate system to a body coordinate system in an ideal state,Is a zero error matrix of the optical axis inside the nacelle, substituted therein、；The expression of (2) is:

Wherein, The function cos is represented as a function of,Representing a function sin; further, the following equation is used:

The following least square formula is obtained through transformation:

Wherein, AndRespectively is equationAn input matrix and an output vector of the sampling data after the form conversion are carried out; the required five error angle values can be obtained through the formula.

9. An electronic device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor implements the steps of the method of any of claims 1-8 when the computer program is executed.

10. A computer readable storage medium storing computer instructions which, when executed by a processor, implement the steps of the method of any one of claims 1-8.