An all-weather global positioning system and method based on astro-inertial combination

Abstract

The application provides a kind of all-weather global positioning system and method based on astronomical / inertial combination, the positioning system includes astronomical navigation system, inertial navigation system and clock system.The inertial navigation system provides horizontal and azimuth information for star sensor and sun sensor in the astronomical navigation system, for determining the altitude angle and azimuth angle of observed celestial body.The clock system provides high-precision clock and unified time for the positioning system.The astronomical navigation system includes star sensor, sun sensor, polarized light sensor and data processing unit, the astronomical navigation system receives the horizontal and azimuth information of the inertial navigation system, receives the clock of the clock system for system clock synchronization, calculates global absolute position, without any prior knowledge of starting position.It is a kind of all-weather, all-autonomous, all-weather global positioning system and method based on astronomical / inertial combination, solves the technical problem that existing navigation positioning is easy to be disturbed.

Description

Technical Field

[0001] This invention relates to the field of navigation and positioning technology, and in particular to an all-weather global positioning system and method based on a combination of astronomical and inertial navigation. Background Technology

[0002] Navigation Satellite Systems (GNSS) obtain navigation parameters by receiving radio signals from multiple orbiting satellites and calculating them. They offer advantages such as high positioning accuracy, no error accumulation over time, and continuous all-weather navigation. For many years, they have been a widely used navigation and positioning source. However, the risks of GNSS signal interference and spoofing are increasing, impacting various fields including unmanned aerial vehicles (UAVs). Furthermore, for vehicles operating within the atmosphere, such as aircraft, ships, and vehicles, certain extreme situations require stealth, reliability, and real-time navigation and positioning capabilities, thus placing demands on fully autonomous, all-day, and all-weather navigation and positioning systems.

[0003] The main autonomous navigation methods in modern navigation include Inertial Navigation Systems (INS) and Celestial Navigation Systems (CNS). INS relies on its own accelerometers and gyroscopes to measure the acceleration and angular velocity of an object, calculating relevant navigation parameters. It does not depend on external information, does not radiate energy, and is unaffected by weather conditions, possessing advantages such as autonomy and stealth. However, due to the integral calculations used, errors accumulate over time, resulting in high short-term accuracy, but requiring external correction for long-term use. Celestial Navigation Systems (CNS) are an older yet modern navigation method. By observing known celestial bodies or the characteristics of their light in the atmosphere, it determines the altitude and azimuth of the celestial target, calculating navigation parameters such as the vehicle's position and heading based on the laws of celestial motion and time. Celestial navigation offers advantages such as high accuracy, passive operation, wide application, and no error accumulation over time. However, when used within the atmosphere, it is affected by weather conditions, which can cause intermittent navigation parameter output.

[0004] Therefore, by using intermittent high-precision navigation data from a celestial navigation system (CNS) to correct the errors accumulated over time in an inertial navigation system (INS), and combining inertial and celestial data for navigation, positioning, and orientation, the advantages of both systems can be complemented. This not only provides high-precision navigation data but also ensures the concealment, reliability, and real-time performance of the navigation method, meeting the requirements for navigation, positioning, and orientation under extreme conditions.

[0005] Traditional astronomical / inertial integrated navigation systems employ all-weather star sensors to adapt to all-day applications. During the daytime, the sky background is bright, and star energy is relatively weak. To detect faint starlight through stray light in the atmosphere, all-weather star sensors utilize three techniques: First, reducing the optical field of view of the star sensor improves star detection capability; second, spectral filtering is used, which involves selecting specific spectral bands based on the spectral difference between the target and the sky background using appropriate bandpass filters to minimize the impact of background light on the target and improve the signal-to-noise ratio; third, interferometry is used, which involves observing the interference fringes of stars through gratings and then modulating and demodulating them to obtain star coordinates.

[0006] A comprehensive analysis of the three technologies employed in the above-mentioned all-day star sensors reveals that the key challenge lies in observing the faint starlight while avoiding the high-energy background radiation of the sun during daytime operation. This necessitates using observed stars for astronomical navigation, resulting in complex optical structures, large sizes, and high costs. Furthermore, the captured star images exhibit high noise levels and low signal-to-noise ratios, requiring complex star extraction algorithms. A closer analysis reveals that daytime starlight observation is also for the purpose of using known celestial bodies for astronomical navigation. However, the sun's energy is strong and easily observable during the day, and its relative positional changes with Earth are also known, providing the conditions for astronomical navigation. Therefore, daytime astronomical navigation through solar observation is clearly a convenient and effective option. Thus, the starting point of this patent is a global navigation and positioning system that combines astronomical and inertial navigation through daytime solar observation and nighttime star observation.

[0007] As is well known, for a given date, time, and observation location and direction, the position of a known celestial body in the sky is unique. Therefore, if the azimuth and altitude of a known celestial body can be observed, we can deduce the observer's position, i.e., longitude and latitude, based on the observation date and time.

[0008] In conclusion, when GNSS (Global Navigation Satellite System) is unavailable, or when there are requirements for the stealth, reliability, and real-time performance of the navigation and positioning system, designing a navigation system that utilizes the sun during the day and stars at night, and combines it with inertial navigation for all-day global positioning, has significant theoretical and practical implications. Summary of the Invention

[0009] To address the technical problems raised in the background, this invention provides an all-weather global positioning system and method based on astronomical / inertial navigation, which is an all-weather, fully autonomous, and astronomical / inertial navigation system and method that solves the technical problem that existing navigation and positioning systems are easily interfered with.

[0010] To achieve the above objectives, the present invention employs the following technical solution:

[0011] A global positioning system based on a combination of astronomical and inertial navigation, wherein the positioning system includes an astronomical navigation system, an inertial navigation system, and a clock system.

[0012] The inertial navigation system provides horizontal and azimuth information for the star sensor and solar sensor in the astronomical navigation system, which is used to determine the elevation and azimuth angles of the observed celestial bodies.

[0013] The clock system provides the positioning system with a high-precision clock and unified time.

[0014] The astronomical navigation system includes a star sensor, a sun sensor, a polarization light sensor, and a data processing unit. The astronomical navigation system receives the horizontal and azimuth information from the inertial navigation system, receives the clock from the clock system for system clock synchronization, and calculates the global absolute position without any prior knowledge of the starting position.

[0015] The aforementioned positioning method for an all-weather global positioning system based on an astronomical / inertial navigation system utilizes an inertial navigation system to provide horizontal and azimuth information to star sensors and solar sensors in the astronomical navigation system, used to determine the elevation and azimuth angles of observed celestial bodies; it utilizes a clock system to provide the positioning system with a high-precision clock and unified time; and it utilizes the astronomical navigation system to receive the horizontal and azimuth information from the inertial navigation system, and receives the clock from the clock system for system clock synchronization, calculating the global absolute position without requiring any prior knowledge of the starting position.

[0016] The positioning method described above uses a polarization light sensor for positioning during the day, or a combination of a sun sensor and an inertial sensor for positioning; and uses a combination of a star sensor and an inertial sensor for positioning at night.

[0017] Furthermore, during the daytime, the method for individual positioning using a polarized light sensor specifically includes the following:

[0018] 1) A polarization sensor captures images of the sky, taking pictures of four polarization directions: 0°, 45°, 90°, and 135° each time;

[0019] 2) Calculate the Stokes vectors S0, S1, S2 and the degree of polarization DoLP and polarization angle AoP using the Stokes formula;

[0020] 3) Obtain the sun's position, i.e., azimuth and elevation angle, by performing a Hough transform on the polarization angle AoP image;

[0021] 4) Generate a model of the relative positions of the Sun and Earth based on the current Greenwich Mean Time and solve for it;

[0022] 5) Obtain the latitude and longitude of the observation point.

[0023] Furthermore, during the daytime, the method for achieving positioning using a combination of a sun sensor and inertial measurement units specifically includes the following:

[0024] 1) The solar sensor captures images of the sky, and the centroid of the captured images is extracted according to a given threshold;

[0025] 2) Determine if the sun is within the field of view. If it is, proceed to step 3); otherwise, return to step 1.

[0026] 3) Obtain the solar direction vector in the body coordinate system;

[0027] 4) Based on the horizontal attitude provided by the inertial navigation, convert the solar direction vector obtained in step 3) to the local geographic system to obtain the solar altitude angle and azimuth angle;

[0028] 5) Extract the current world time from the clock system, determine the relative position model of the sun and the earth at this time, and calculate the latitude and longitude based on the solar altitude angle and azimuth angle obtained in step 4);

[0029] 6) Determine the latitude and longitude of the observation point.

[0030] Furthermore, at night, the method for positioning using a combination of star sensors and inertial sensors specifically includes the following:

[0031] 1) Star sensors capture images of the night sky;

[0032] 2) Extract star points from the captured starry sky images according to a given threshold, remove false stars, and send the number of star points and their corresponding coordinates to the data processing unit.

[0033] 3) The data processing unit determines the number of star points. If the number of star points is greater than or equal to 3, proceed to the next step; otherwise, return to step 1).

[0034] 4) Calculate the diagonal distance between star points based on their coordinates, compare it with the data in the star database, identify the star map using a triangle matching algorithm, and obtain the attitude of the star sensor relative to the inertial space using the ESOQ2 algorithm.

[0035] 5) Calculate the latitude and longitude of the observation point based on the local geographic perpendicular and Greenwich Mean Time provided by the inertial navigation system.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] First: This method uses inertial sensors to provide orientation and celestial targets for positioning based on a date / time clock to calculate the global absolute position without any prior knowledge of the starting position.

[0038] Second: The technology used in this method can operate 24 hours a day.

[0039] Third: This method provides a drift-free positioning solution.

[0040] Fourth: The navigation method used in this method is passive, so it cannot be detected, is not affected by magnetic interference, and cannot be rejected or deceived.

[0041] Fifth: It can operate in various cloud conditions and can operate anywhere on Earth, including high-altitude areas, near the Arctic and Antarctic. Attached Figure Description

[0042] Figure 1 This is a diagram of an all-weather global positioning system based on an astronomical / inertial combination, according to the present invention.

[0043] Figure 2 This is a flowchart of the method for individual positioning using a polarized light sensor according to the present invention;

[0044] Figure 3 This is a flowchart of the method for achieving positioning using a combination of a solar sensor and an inertial sensor, according to the present invention.

[0045] Figure 4 This is a flowchart of the method for achieving positioning using a combination of star sensors and inertial sensors according to the present invention. Detailed Implementation

[0046] The specific embodiments provided by the present invention will be described in detail below with reference to the accompanying drawings.

[0047] like Figure 1 As shown, an all-weather global positioning system based on astronomical / inertial combination includes an astronomical navigation system, an inertial navigation system, and a clock system.

[0048] The inertial navigation system provides horizontal and azimuth information for the star sensor and solar sensor in the astronomical navigation system, which is used to determine the elevation and azimuth angles of the observed celestial bodies.

[0049] The clock system provides the positioning system with a high-precision clock and unified time.

[0050] The astronomical navigation system receives horizontal and azimuth information from the inertial navigation system and clock information from the clock system for system clock synchronization, and calculates the global absolute position without any prior knowledge of the starting position.

[0051] The astronomical navigation system includes a star sensor, a sun sensor, a polarization light sensor, and a data processing unit.

[0052] The star sensor is a nano-type star sensor with a field of view of 14°×14°, operating in the visible light band of 450nm~750nm. The star sensor structure consists of a sunshade, an optical lens, a photodetector, and a focal plane imaging circuit. The sunshade is used to suppress stray light when photographing stars. The optical lens employs a refractive optical system to focus the energy of starlight onto the photodetector at the focal plane. The photodetector converts the focused star energy into an electrical signal, and the focal plane imaging circuit further transmits the electrical signal of the night sky image containing stars, pixel by pixel, to the data processing unit of the astronomical navigation system. The data processing unit extracts stars from the image containing stars, calculates the diagonal distance between stars, searches for them in the star database in memory, performs star image matching and attitude calculation, and obtains the star sensor's attitude relative to inertial space. Based on the local perpendicular provided by the inertial navigation system, as well as the date and time of observation, the local longitude and latitude are calculated, achieving global positioning at night.

[0053] The solar sensor and star sensor operate in two different time periods, differing only in light intensity. Therefore, they share a single hardware system, implemented only by adding a solar filter to the front of the star sensor's sunshade. The filter's opening and closing are controlled by the data processing unit, which issues on / off commands based on the day-night cycle. During the day, the filter is open for observing the sun; at night, it is closed for observing stars. During daytime positioning, if the sun is within the field of view, an image containing the sun is captured, its center of mass is extracted, and its direction vector is calculated. Based on the local geographic level provided by inertial navigation, the solar altitude and azimuth angles are obtained. Finally, the longitude and latitude of the observation point are calculated based on the relative position of the sun and Earth and Greenwich Mean Time.

[0054] A polarization sensor is a system used to measure the characteristics of atmospheric polarized light, acquiring atmospheric polarization maps. It includes filters, optical lenses, a four-channel polarizer, a photoelectric sensor, and a focal plane array. The filters are bandpass filters in the 500nm to 550nm wavelength range. The optical lens is a series of optical components that divide the incident field of view into four identical fields, projected onto four polarizers in front of the photoelectric detector. The polarization angles of the four polarizers are 0°, 45°, 90°, and 135°, respectively. The energy from the four fields of view passing through the polarizers converges in the four quadrants of the photoelectric detector, and the captured images are the sky polarization maps in four directions. The focal plane array transmits the electrical signals of the photoelectric detector image pixel by pixel to the data processing unit of the astronomical navigation system. The data processing unit, pixel by pixel, calculates the Stokes vectors S0, S1, S2, the degree of polarization DoLP, and the polarization angle AoP based on the sky polarization map of the observation point, and uses the Hough transform principle to obtain the solar altitude angle and azimuth angle. Using the current relative position model of the Sun and Earth, and combined with the Greenwich Mean Time of the observation point, the longitude and latitude of the observation point are obtained.

[0055] The data processing unit in the astronomical navigation system includes an embedded DSP processor and data storage (Flash and SRAM). It transmits data to the star sensor, sun sensor, polarization sensor, inertial system, and clock system via an extended RS422 serial port. The embedded DSP processor is responsible for tasks such as: star point extraction, star map matching, and attitude calculation from the star sensor; centroid extraction, solar direction vector calculation, and coordinate system transformation from the sun sensor; calculation of Stokes vectors S0, S1, S2, polarization degree DoLP, polarization angle AoP, and solar position from the polarization sensor; receiving horizontal and azimuth information from the inertial navigation system; receiving the clock and Greenwich Mean Time from the clock system for system clock synchronization; and opening and closing the solar filter. The Flash memory stores a navigation star database of stars with a magnitude greater than 6.5 across the entire celestial sphere, a model of the relative positions of the Sun and Earth, and other data.

[0056] The inertial navigation system is a strapdown inertial navigation system that provides horizontal and azimuth information for star sensors and sun sensors to determine the elevation and azimuth angles of observed celestial objects.

[0057] The clock system includes a temperature-controlled crystal oscillator and a Greenwich Mean Time (GMT) timing circuit, providing the system with a high-precision clock and unified time.

[0058] The aforementioned positioning method for an all-weather global positioning system based on an astronomical / inertial navigation system utilizes an inertial navigation system to provide horizontal and azimuth information to star sensors and solar sensors in the astronomical navigation system, used to determine the elevation and azimuth angles of observed celestial bodies; it utilizes a clock system to provide the positioning system with a high-precision clock and unified time; and it utilizes the astronomical navigation system to receive the horizontal and azimuth information from the inertial navigation system, and receives the clock from the clock system for system clock synchronization, calculating the global absolute position without requiring any prior knowledge of the starting position.

[0059] The positioning method described above uses a polarization light sensor for positioning during the day, or a combination of a sun sensor and an inertial sensor for positioning; and uses a combination of a star sensor and an inertial sensor for positioning at night.

[0060] like Figure 2 As shown, during the day, the method for individual positioning using a polarization sensor specifically includes the following:

[0061] 1) A polarization sensor captures images of the sky, taking pictures of four polarization directions: 0°, 45°, 90°, and 135° each time;

[0062] 2) Calculate the Stokes vectors S0, S1, S2 and the degree of polarization DoLP and polarization angle AoP using the Stokes formula;

[0063] 3) Obtain the sun's position, i.e., azimuth and elevation angle, by performing a Hough transform on the polarization angle AoP image;

[0064] 4) Generate a model of the relative positions of the Sun and Earth based on the current Greenwich Mean Time and solve for it;

[0065] 5) Obtain the latitude and longitude of the observation point.

[0066] like Figure 3 As shown, during the day, the method for achieving positioning using a combination of a sun sensor and inertial sensors specifically includes the following:

[0067] 1) The solar sensor captures images of the sky, and the centroid of the captured images is extracted according to a given threshold;

[0068] 2) Determine if the sun is within the field of view. If it is, proceed to step 3); otherwise, return to step 1.

[0069] 3) Obtain the solar direction vector in the body coordinate system;

[0070] 4) Based on the horizontal attitude provided by the inertial navigation, convert the solar direction vector obtained in step 3) to the local geographic system to obtain the solar altitude angle and azimuth angle;

[0071] 5) Extract the current world time from the clock system, determine the relative position model of the sun and the earth at this time, and calculate the latitude and longitude based on the solar altitude angle and azimuth angle obtained in step 4);

[0072] 6) Determine the latitude and longitude of the observation point.

[0073] like Figure 4 As shown, the method for positioning using a combination of star sensors and inertial sensors at night specifically includes the following:

[0074] 1) Star sensors capture images of the night sky;

[0075] 2) Extract star points from the captured starry sky images according to a given threshold, remove false stars, and send the number of star points and their corresponding coordinates to the data processing unit.

[0076] 3) The data processing unit determines the number of star points. If the number of star points is greater than or equal to 3, proceed to the next step; otherwise, return to step 1).

[0077] 4) Calculate the diagonal distance between star points based on their coordinates, compare it with the data in the star database, identify the star map using a triangle matching algorithm, and obtain the attitude of the star sensor relative to the inertial space using the ESOQ2 algorithm.

[0078] 5) Calculate the latitude and longitude of the observation point based on the local geographic perpendicular and Greenwich Mean Time provided by the inertial navigation system.

[0079] This method utilizes inertial sensors for orientation and celestial targets for positioning based on a date / time clock to calculate a global absolute position without any prior knowledge of the starting position. The technology employed allows for 24-hour operation. This method provides a drift-free positioning solution. The navigation method is passive, therefore undetectable, unaffected by magnetic interference, and cannot be rejected or spoofed. It can operate in various cloud cover conditions and can function anywhere on Earth, including high altitudes, near the Arctic and Antarctic.

[0080] The above embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the above embodiments. Unless otherwise specified, the methods used in the above embodiments are conventional methods.

Claims

1. A positioning method based on an all-weather global positioning system using a combination of astronomical and inertial navigation, characterized in that, The positioning system includes an astronomical navigation system, an inertial navigation system, and a clock system; The inertial navigation system provides horizontal and azimuth information for the star sensors and solar sensors in the astronomical navigation system, which is used to determine the elevation and azimuth angles of the observed celestial bodies. The clock system provides the positioning system with a high-precision clock and unified time. The astronomical navigation system includes a star sensor, a sun sensor, a polarization light sensor, and a data processing unit. The astronomical navigation system receives the horizontal and azimuth information from the inertial navigation system, receives the clock from the clock system for system clock synchronization, and calculates the global absolute position without any prior knowledge of the starting position. The positioning method described above uses a polarization light sensor alone for positioning during the day, or a combination of a sun sensor and an inertial sensor for positioning; and uses a combination of a star sensor and an inertial sensor for positioning at night. During the daytime, the method for achieving positioning using a combination of a sun sensor and inertial sensors specifically includes the following: 1) The solar sensor captures images of the sky, and the centroid of the captured images is extracted according to a given threshold; 2) Determine if the sun is within the field of view. If it is, proceed to step 3); otherwise, return to step 1. 3) Obtain the solar direction vector in the body coordinate system; 4) Based on the horizontal attitude provided by the inertial navigation, convert the solar direction vector obtained in step 3) to the local geographic system to obtain the solar altitude angle and azimuth angle; 5) Extract the current world time from the clock system, determine the relative position model of the sun and the earth at this time, and calculate the latitude and longitude based on the solar altitude angle and azimuth angle obtained in step 4); 6) Determine the latitude and longitude of the observation point; At night, the method for positioning using a combination of star sensors and inertial sensors specifically includes the following: 1) Star sensor captures images of the night sky; 2) Extract star points from the captured starry sky images according to a given threshold, remove false stars, and send the number of star points and their corresponding coordinates to the data processing unit; 3) The data processing unit determines the number of star points. If the number of star points is greater than or equal to 3, proceed to the next step; otherwise, return to step 1). 4) Calculate the diagonal distance between star points based on their coordinates, compare it with the data in the star database, perform star map recognition using a triangle matching algorithm, and obtain the attitude of the star sensor relative to the inertial space using the ESOQ2 algorithm. 5) Calculate the latitude and longitude of the observation point based on the local geographic perpendicular and Greenwich Mean Time provided by the inertial navigation system.

2. The positioning method of an all-weather global positioning system based on astronomical / inertial combination according to claim 1, characterized in that, During the daytime, the method for individual positioning using a polarization light sensor specifically includes the following: 1) A polarization sensor captures images of the sky, taking images at four polarization directions: 0°, 45°, 90°, and 135° each time; 2) Calculate the Stokes vectors S0, S1, S2 and the degree of polarization DoLP and polarization angle AoP using the Stokes formula; 3) Obtain the sun's position, i.e., azimuth and elevation angle, by performing a Hough transform on the polarization angle AoP image; 4) Generate a model of the relative positions of the Sun and Earth based on the current Greenwich Mean Time and solve for it; 5) Obtain the latitude and longitude of the observation point.

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