A navigation and orientation device based on star sensor observation of local atmospheric polarization characteristics

Abstract

This invention discloses a navigation and orientation device based on the observation of local atmospheric polarization characteristics using a star sensor, belonging to the field of navigation. It enables navigation and orientation via the observation of local atmospheric polarization characteristics using a star sensor. The device includes a star sensor, an electrically operated polarizer rotating frame, a polarizer, an electrically adjustable aperture stop, a synchronizer, and a multi-mode satellite navigation receiver module. It primarily utilizes the solar zenith meridian obtained from the observed zenith polarization diagram in the carrier coordinate system X. b OY b Plane and vertical axis Y b The solar azimuth angle is calculated based on the observation date, time, and latitude / longitude, and the heading is obtained by comparing the two. This adds a heading determination function to the star sensor, expanding its application range, improving the real-time performance of heading determination, and providing flexibility and usability in polarization orientation.

Description

Technical Field

[0001] The invention belongs to the field of navigation, and in particular relates to a navigation and orientation device based on a star sensor to observe polarized light characteristics of local atmosphere. Background Art

[0002] Azimuth or heading is the key navigation information required for carrier navigation and target aiming, and deviation in heading has often become the main source of error. Therefore, accurate heading sensing is very important for military and commercial applications. There are generally three ways to determine heading: the first is to use a gyroscope that measures inertial parameters to determine the heading. That is, using the axial stability and precession of the gyroscope, combined with the earth's rotation vector and gravity vector, a gyrocompass is made with control equipment and damping equipment to provide a true north reference instrument. The second is to use a magnetic compass to detect the earth's magnetic field to determine the heading. That is, the magnetic heading is calculated by measuring the earth's magnetic field with a magnetic compass, and the true heading is calculated in combination with the magnetic declination. The third is to use satellite navigation dual antenna direction finding. That is, two satellite measurement antennas are installed along the longitudinal axis of the carrier at a distance, and the baseline vectors determined by the two antennas in the ground-fixed coordinate system are measured by relative positioning of carrier phase difference, and converted to the northeast sky coordinate system to determine the current heading angle information of the carrier. The three orientation methods each have their own advantages and disadvantages. Among them, the gyrocompass can only be used within 70 degrees north and south latitude; the magnetic compass is easily affected by abnormal magnetic field interference; and satellite navigation signals are easily interfered with and deceived.

[0003] Inspired by the powerful navigation and orientation capabilities of organisms, and already used by the Vikings, the directional navigation method based on the atmospheric polarization information naturally existing in nature, namely the polarized light directional navigation method, has the characteristics of strong autonomy, high precision, and strong anti-electromagnetic interference ability. The directional systems using the polarized light directional navigation method are divided into two categories based on the sampling mechanism: point source type and imaging type. The point source directional system consists of a polarizer, a photodiode, and a logarithmic amplifier, etc. It has the characteristics of good real-time performance and high robustness. It can measure the polarization degree of a certain point in the sky, but it is easily affected by the sky environment. The imaging directional system consists of an optical lens, a polarizer, and an image sensor, etc. It can measure the polarization information of the entire sky and is resistant to disturbances in some areas of the sky, but the real-time performance of the system is not good and the image processing process is complicated.

[0004] The star sensor is composed of a sunshade, an optical lens, an image sensor, and a data processing circuit. It is a kind of attitude sensor that obtains the attitude information of the carrier by taking a star map, extracting the coordinates of each star point in the star map, and comparing it with the star map in the star library. It is similar to the imaging polarization orientation system in terms of image capture and processing, and can realize real-time image processing, and has the characteristics of an imaging polarization orientation system. However, the star sensor used in the atmosphere cannot observe the starlight to determine the attitude and thus cannot achieve heading determination during the day due to the influence of solar stray light. Summary of the invention

[0005] In view of the shortcomings of the existing orientation methods, the present invention provides a navigation and orientation device based on a star sensor observing the polarized light characteristics of the local atmosphere, which solves the problem that the star sensor cannot determine the heading during the day due to the inability to observe the stars and determine the attitude, and can realize the star sensor to determine the heading by observing the polarized light characteristics of the local atmosphere for navigation and orientation, thereby providing reliable heading information.

[0006] The technical scheme adopted by the present invention is as follows: a navigation orientation device based on observing the polarized light characteristics of local atmosphere by a star sensor, comprising a star sensor, an electric polarizer rotating frame, a polarizer, an electric adjustable aperture diaphragm, a synchronizer and a multi-mode satellite navigation receiver module, wherein the electric polarizer rotating frame is fixedly mounted at the front end of the optical lens of the star sensor, the light-transmitting part of the electric polarizer rotating frame is coaxially assembled with the optical lens, the electric polarizer rotating frame is driven to rotate by a stepping motor, the polarizer is mounted on the polarizer housing through a pressing ring, the polarizer housing is connected to the electric polarizer rotating frame through an SM1 thread, the zero-degree reference direction of the polarizer is aligned with the zero-degree of the electric polarization rotating frame, the electric adjustable aperture diaphragm is fixedly connected to the outer frame of the electric polarizer rotating frame and is located at the front end of the polarizer, the electric adjustable aperture diaphragm adjusts the light-transmitting aperture in response to the aperture adjustment instruction sent by the star sensor, the electric adjustable aperture diaphragm, the electric polarizer rotating frame and the optical lens of the star sensor are coaxial, the electric polarizer rotating frame receives the instruction sent by the synchronizer to rotate the polarizer, thereby realizing the star sensor at different The solar incident light measurement under polarization angle, the multi-mode satellite navigation receiver module includes a BDS navigation and positioning system, a GPS navigation and positioning system and a GLONASS navigation and positioning system, and is used to provide the latitude and longitude position information of the observation point and the observation date and UTC time; the synchronizer includes a timer module and an instruction transceiver module, the timer module receives the date and UTC time provided by the multi-mode satellite navigation receiver module, and converts and corrects the UTC time to obtain the local true solar time, and is used to provide absolute time; the instruction transceiver module is used to receive the electric polarizer rotating frame rotation angle instruction, the electric adjustable aperture diaphragm opening and closing and aperture adjustment instruction sent by the star sensor, and completes the distribution and response of the instruction; the star sensor sends the aperture diaphragm opening minimum instruction to the synchronizer module, and the synchronizer module forwards the instruction to the electric aperture diaphragm controller after receiving the instruction, and returns the response instruction, and the star sensor shoots the sky after receiving the response instruction, and calculates the average grayscale and maximum grayscale of the image, and judges whether the maximum grayscale reaches 90% of the maximum grayscale, and if it meets the requirements, the solar altitude angle h at the observation time is calculated according to the observation date and the latitude φ of the observation location. s and the solar azimuth A s , the formula is as follows:

[0007] sinh s =sinδsinφ+cosδcosφcosτ

[0008]

[0009] Among them, δ is the solar declination angle, φ is the geographical latitude of the observation site, and τ is the solar hour angle at the observation site at the time of observation;

[0010] The star sensor sends polarizer rotation instructions of 0°, 60°, and 120° through a synchronizer, and takes corresponding angle sky polarization images, which are recorded as I(0°), I(60°), and I(120°). For each pixel, the three components I, Q, and U of the Stokes polarization vector are obtained, where I is the unpolarized light intensity, and Q and U represent linear polarized light in two directions, respectively. The formula is as follows:

[0011]

[0012]

[0013]

[0014] Then calculate the degree of polarization DoLP image and polarization angle Aop image of the zenith area.

[0015]

[0016]

[0017] The degree of polarization DoLP image is used to determine the degree of polarization of sunlight in the shooting area. Through this image, it can be determined whether the area is clear, thereby determining the availability of the polarization angle Aop image. If the values ​​of the degree of polarization DoLP image are within a reasonable range, it means that the polarization angle Aop image can be used to determine the heading. Hough transform is used to find the solar zenith meridian in the polarization angle Aop image, and the polarization angle Aop image is obtained in the carrier coordinate system X. b OY b plane, solar zenith meridian and vertical axis Y b The angle is A b ; The solar zenith meridian in the image of the zenith polarization angle Aop observed in the carrier coordinate system is the solar zenith meridian in the geographic coordinate system, that is, the solar zenith meridian is the same meridian; compare the azimuth angle A of the solar zenith meridian in the image of the actual zenith polarization angle Aop observed in the carrier coordinate system b The azimuth A of the solar zenith meridian in the geographic coordinate system calculated according to the solar calendar s , so as to obtain the heading, assuming that the origin of the horizontal plane of the carrier coordinate system coincides with the origin of the local geographic coordinate system, the carrier heading angle

[0018] Furthermore, the zero-degree reference direction of the polarizer is in a straight line with the longitudinal axis direction of the star sensor.

[0019] Furthermore, the rotating disk of the electric polarizer rotating frame is engraved with direct readings, with a graduation of 1° and a vernier accuracy of 5 arc minutes.

[0020] Furthermore, the multi-mode satellite navigation receiver module and synchronizer are integrated in an electrically adjustable aperture diaphragm.

[0021] Beneficial effects and advantages of the present invention:

[0022] First, the present invention enables the star sensor to observe the polarization characteristics of sunlight in the zenith area when it is not possible to observe stars and determine the attitude during the day, thereby realizing heading determination. The heading determination function of the star sensor is increased, and the application scope of the star sensor is expanded.

[0023] Second: When determining the heading, the high-speed image processing capability of the star sensor is utilized to shorten the processing time of the zenith polarization image and improve the real-time performance of heading determination.

[0024] Third: The heading can be determined by observing the local atmospheric polarization characteristics in the zenith area. As long as the zenith area is clear, the heading can be determined, which is flexible and usable in polarization orientation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a structural exploded view of Example 1 of the present invention;

[0026] Figure 2 This is a flow chart of heading determination according to Embodiment 1 of the present invention;

[0027] Figure 3 This is a diagram of a method for obtaining a heading according to Embodiment 1 of the present invention; DETAILED DESCRIPTION

[0028] The present invention is further described below with reference to the accompanying drawings:

[0029] Example 1

[0030] like Figure 1As shown, a navigation orientation device based on a star sensor for observing polarized light characteristics of local atmosphere comprises a star sensor 1, an electric polarizer rotating frame 2, a polarizer 3, an electric adjustable aperture diaphragm 4, a synchronizer and a multi-mode satellite navigation receiver module, wherein the electric polarizer rotating frame 2 is fixedly mounted at the front end of the optical lens of the star sensor, the light-transmitting part of the electric polarizer rotating frame 2 is coaxially assembled with the optical lens, the electric polarizer rotating frame 2 is driven to rotate by a stepping motor, the polarizer 3 is mounted on a polarizer housing, the polarizer housing is connected to the electric polarizer rotating frame 2 via an SM1 thread, the zero-degree reference direction of the polarizer 3 is aligned with the zero-degree of the electric polarizer rotating frame 2, the zero-degree reference direction of the polarizer 3 is in a straight line with the longitudinal axis direction of the star sensor 1, the electric adjustable aperture diaphragm 4 is fixedly connected to the outer frame of the electric polarizer rotating frame 2 and is located at the front end of the polarizer 3, and the electric adjustable aperture diaphragm 4 adjusts the aperture direction emitted by the star sensor 1 The electric adjustable aperture diaphragm 4, the electric polarizer rotating frame 2 and the optical lens of the star sensor 1 are coaxial, the electric polarizer rotating frame 2 receives the instruction sent by the synchronizer to rotate the polarizer 3 so as to measure the solar incident light of the star sensor 1 at different polarization angles, the multi-mode satellite navigation receiver module includes a BDS navigation and positioning system, a GPS navigation and positioning system and a GLONASS navigation and positioning system, which are used to provide the latitude and longitude position information of the observation point and the observation date and UTC time; the synchronizer includes a timer module and an instruction transceiver module, the timer module receives the date and UTC time provided by the multi-mode satellite navigation receiver module, and converts and corrects the UTC time to obtain the local true solar time, which is used to provide the absolute time; the instruction transceiver module is used to receive the rotation angle instruction of the electric polarizer rotating frame 2, the opening and closing instruction of the electric adjustable aperture diaphragm 4 and the aperture adjustment instruction sent by the star sensor 1, and complete the distribution and response of the instruction.

[0031] Among them, star sensor 1 uses a 1-inch CMOS chip CMV4000, and the optical lens has a light aperture of 25mm. There are 4 M3 threaded holes with a spacing of 30mm on the shell of star sensor 1, which can be used to install 30mm cage optical system connecting rods. The electric polarization rotating frame 2 uses a K10CR1 stepper motor to provide smooth, high-precision, high-repeatability and high-stability 360° bidirectional rotation. The rotating part of the disk has laser engraved scales, and the rotating disk of the main dial is engraved with direct readings, with a division of 1° and a vernier accuracy of 5 arc minutes. It is equipped with SM1 threads (1.035"-40) for installation inch lens tube, each side is equipped with four 4-40 threaded holes, which can be fixed in a 30mm cage optical cage system. The model of polarizer 3 is LPVISC100-MP2, equipped with an SM1 threaded housing. The threaded housing indicates the zero-degree polarization direction of the polarizer, and can be directly installed on the electric polarization rotation frame 2. After installation, align the zero degree of polarizer 3 with the zero degree of electric polarization rotation frame 2. The electric adjustable aperture diaphragm 4 adopts a 20 stepper motor and a precision-ground transmission structure, with small backlash, bidirectional precise limit, and continuously adjustable light aperture. The light aperture can be adjusted quickly and accurately when repeated back and forth adjustments are made. In order to adapt to the variable aperture range of the 1-inch optical diaphragm, it is set at The electric adjustable aperture diaphragm 4 is mounted on the outer frame of the electric polarizer rotating frame 2 through a stud, and the aperture diaphragm is coaxially assembled with the polarizer adjustment frame and the optical lens of the star sensor. The synchronizer and the high-performance BDS / GPS / GNSS multi-mode satellite positioning and navigation receiver SOC module GP-01 are integrated in the electric adjustable aperture diaphragm 4.

[0032] The device of this embodiment is used to implement the navigation and orientation method of observing the local atmospheric polarization characteristics by a star sensor, which mainly obtains the solar zenith meridian in the carrier coordinate system X according to the observed zenith polarization map. b OY b Plane and vertical axis Y b The angle is calculated based on the observation date, time and longitude and latitude to calculate the solar azimuth in the local geographic coordinate system, and the heading is obtained by comparing the two. Figure 2 As shown, the specific implementation steps are as follows (taking the static horizontal method as an example):

[0033] Step 1: Adjusting the aperture diaphragm is to adjust the energy entering the star sensor 1. The aperture diaphragm opening diameter is divided into 16 levels from the smallest to the largest. Star sensor 1 sends the command of opening the aperture diaphragm to the synchronizer module. After receiving the command, the synchronizer command module forwards it to the electric aperture diaphragm controller and returns the response command. After receiving the response command, star sensor 1 takes a picture of the sky and calculates the average grayscale and maximum grayscale of the image. Determine whether the maximum grayscale reaches 90% of the maximum grayscale. If it is satisfied, proceed to the next step, otherwise modify the aperture opening and closing command and repeat this step.

[0034] Step 2: Calculate the solar altitude angle h at the time of observation based on the observation date and time and the latitude φ of the observation location s and the solar azimuth A s .

[0035] sinh s =sinδsinφ+cosδcosφcosτ

[0036]

[0037] Among them, δ is the solar declination angle, φ is the geographical latitude of the observation site, and τ is the solar hour angle at the observation site at the time of observation.

[0038] Step 3: Calculate the actual polarization angle diagram at the zenith of the observation point. The star sensor sends the polarizer rotation instructions of 0°, 60°, and 120° through the synchronizer, and takes the corresponding sky polarization diagrams, which are recorded as I(0°), I(60°), and I(120°). For each pixel, the three components of the Stokes polarization vector I, Q, and U are calculated, where I is the unpolarized light intensity, and Q and U represent the linear polarized light in two directions, respectively.

[0039]

[0040]

[0041]

[0042] The degree of polarization DoLP image and the angle of polarization Aop image of the zenith area are further calculated according to the formula.

[0043]

[0044]

[0045] The degree of polarization DoLP image is used to determine the degree of polarization of sunlight in the shooting area. Through this image, it can be determined whether the area is clear, and thus determine the availability of the polarization angle Aop image. If the values ​​of the degree of polarization DoLP image are within a reasonable range, it means that the polarization angle Aop image can be used to determine the heading.

[0046] Use Hough transform to find the solar zenith meridian in the polarization angle Aop image. b OY b plane, solar zenith meridian and vertical axis Y b The angle is A b .

[0047] Step 4: The solar zenith meridian in the zenith polarization angle Aop image observed in the carrier coordinate system is the solar zenith meridian in the geographic coordinate system, that is, the solar zenith meridian is the same meridian. Therefore, the azimuth angle A of the solar zenith meridian in the actual observed zenith polarization angle Aop image in the carrier coordinate system is compared. b The azimuth A of the solar zenith meridian in the geographic coordinate system calculated according to the solar calendar s , thereby obtaining the heading. Assume that the origin of the horizontal plane of the carrier coordinate system coincides with the origin of the local geographic coordinate system, such as Figure 3 , carrier heading angle

Claims

1. A navigation and orientation device based on a star sensor for observing polarized light characteristics of local atmosphere, comprising a star sensor, an electric polarizer rotating frame, a polarizer, an electric adjustable aperture diaphragm, a synchronizer and a multi-mode satellite navigation receiver module, characterized in that: The electric polarizer rotating frame is fixedly installed at the front end of the optical lens of the star sensor, the light-transmitting part of the electric polarizer rotating frame is coaxially assembled with the optical lens, and the electric polarizer rotating frame is driven to rotate by a stepping motor. The polarizer is mounted on the polarizer housing through a pressing ring, the polarizer housing is connected to the electric polarizer rotating frame through an SM1 thread, and the zero-degree reference direction of the polarizer is aligned with the zero-degree of the electric polarization rotating frame. The electrically adjustable aperture diaphragm is fixedly connected to the outer frame of the electrically driven polarizing plate rotating frame and is located at the front end of the polarizing plate. The electrically adjustable aperture diaphragm adjusts the light aperture in response to the aperture adjustment instruction sent by the star sensor. The electric adjustable aperture diaphragm, the electric polarizer rotating frame and the optical lens of the star sensor are coaxial, and the electric polarizer rotating frame receives the instruction sent by the synchronizer to rotate the polarizer so as to realize the measurement of solar incident light of the star sensor at different zenith polarization angles. The multi-mode satellite navigation receiver module includes a BDS navigation and positioning system, a GPS navigation and positioning system, and a GLONASS navigation and positioning system, which are used to provide the latitude and longitude position information of the observation point, the observation date, and the UTC time; The synchronizer includes a timer module and a command transceiver module. The timer module receives the date and UTC time provided by the multi-mode satellite navigation receiver module, and converts and corrects the UTC time to obtain the local true solar time, which is used to provide absolute time. The command transceiver module is used to receive the rotation angle instruction of the electric polarizer rotating frame, the opening and closing of the electric adjustable aperture diaphragm and the aperture adjustment instruction sent by the star sensor, and completes the distribution and response of the instruction. The star sensor sends a minimum aperture diaphragm opening instruction to the synchronizer module. After receiving the instruction, the synchronizer module forwards it to the electric aperture diaphragm controller and returns a response instruction. After receiving the response instruction, the star sensor shoots the sky and calculates the average grayscale and maximum grayscale of the image, and determines whether the maximum grayscale reaches 90% of the maximum grayscale. If it meets the requirement, the solar altitude angle h at the observation time is calculated according to the observation date and the latitude φ of the observation location. s and the azimuth A of the solar zenith meridian in the geographic coordinate system s , the formula is as follows: born s =sinδsinφ+cosδcosφcosτ Wherein, δ is the solar declination angle, φ is the latitude of the observation location, and τ is the solar hour angle at the observation location at the observation time; the star sensor sends instructions for the polarizer to rotate 0°, 60°, and 120° respectively through the synchronizer, and takes pictures of the sky polarization images at the corresponding angles, which are recorded as I (0°) ,I (60°) ,I (120°) , for each pixel, the three components of the Stokes polarization vector I, Q, and U are calculated, where I is the unpolarized light intensity, and Q and U represent the linearly polarized light in two directions, respectively. The formula is as follows: Then calculate the degree of polarization DoLP image and the zenith polarization angle Aop image of the zenith area. The degree of polarization DoLP image is used to determine the degree of polarization of sunlight in the shooting area. Through this image, it can be determined whether the area is clear, thereby determining the availability of the zenith polarization angle Aop image. If the values ​​of the degree of polarization DoLP image are within a reasonable range, it means that the zenith polarization angle Aop image can be used to determine the heading; Use Hough transform to find the solar zenith meridian in the zenith polarization angle Aop image, in the carrier coordinate system X b OY b plane, solar zenith meridian and vertical axis Y b The angle is A b ; The solar zenith meridian in the image of the zenith polarization angle Aop observed in the carrier coordinate system is the solar zenith meridian in the geographic coordinate system, that is, the solar zenith meridian is the same meridian; compare the angle A in the image of the zenith polarization angle Aop actually observed in the carrier coordinate system b The azimuth A of the solar zenith meridian in the geographic coordinate system calculated according to the solar calendar s , so as to obtain the heading, assuming that the origin of the horizontal plane of the carrier coordinate system coincides with the origin of the local geographic coordinate system, the carrier heading angle 2. A navigation and orientation device based on star sensor observation of local atmospheric polarization characteristics according to claim 1, characterized in that: The zero-degree reference direction of the polarizer is in a straight line with the longitudinal axis direction of the star sensor.

3. A navigation and orientation device based on star sensor observation of local atmospheric polarization characteristics according to claim 1, characterized in that: The rotating disk of the electric polarizer rotating frame is engraved with direct readings, with a graduation of 1° and a vernier accuracy of 5 arc minutes.

4. A navigation and orientation device based on star sensor observation of local atmospheric polarization characteristics according to claim 1, characterized in that: The multi-mode satellite navigation receiver module and synchronizer are integrated in an electrically adjustable aperture diaphragm.

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