Star sensor and celestial navigation system

Abstract

The application discloses a star sensor, which comprises a detection lens, a star sensor body frame, a rotating mechanism, a circuit board, a heat-conducting pad, a heating film and a PEEK shell; the detection lens is installed on the star sensor body frame; the rotating mechanism is connected with the star sensor body frame to make the star sensor body frame rotate axially; the circuit board is arranged on the star sensor body frame; the heat-conducting pad is arranged between the circuit board and the star sensor body frame to transfer the heat generated by the chip of the circuit board to the star sensor body frame; the outer side of the circuit board is sequentially provided with the heating film and the PEEK shell; the heating film can heat the circuit board; and the PEEK shell can isolate the radiant heat of the high-temperature environment. The application further discloses an astronomical navigation system. The application can adapt to high and low temperatures, strong radiation and other harsh environments, and ensures the reliability of the equipment.

Description

Technical Field

[0001] This invention belongs to the field of celestial sensors, specifically relating to a star sensor and an astronomical navigation system. Background Technology

[0002] Star sensors are widely used celestial sensors and a crucial component of astronomical navigation systems. They frequently operate in harsh environments, including extreme temperatures and intense radiation. Existing star sensors often lack methods for adjusting their orientation and are frequently affected by solar radiation and stray light interference, impacting their star-measuring capabilities. Furthermore, the circuit boards within star sensors are prone to failure when operating in high and low temperature environments, leading to decreased accuracy or even malfunction. Therefore, a new type of star sensor is urgently needed. Summary of the Invention

[0003] The main objective of this invention is to provide a star sensor and astronomical navigation system that can adapt to harsh environments such as high and low temperatures and strong radiation, ensuring the reliability of the equipment.

[0004] The technical solution adopted in this invention is:

[0005] A star sensor includes a detection lens, a star sensor body frame, a rotating mechanism, a circuit board, a thermal pad, a heating film, and a PEEK housing;

[0006] The detection lens is mounted on the star sensor body frame;

[0007] The rotating mechanism is connected to the star sensor body frame, causing the star sensor body frame to rotate axially;

[0008] The circuit board is mounted on the star sensor body frame; the thermal pad is placed between the circuit board and the star sensor body frame to transfer the heat generated by the chip on the circuit board to the star sensor body frame; a heating film and a PEEK shell are arranged in sequence on the outside of the circuit board. The heating film can heat the circuit board, and the PEEK shell can isolate the radiant heat of the high temperature environment.

[0009] A further proposed solution is that the rotating mechanism includes an azimuth axis, an angle sensor, and a rotary motor;

[0010] The azimuth axis is connected to the star sensor body frame via an azimuth mounting flange;

[0011] The angle sensor is mounted on the azimuth axis; the angle sensor collects the angle data of the azimuth axis and transmits the data to the controller, which controls the rotary motor to work based on the data, and the rotary motor drives the star sensor body frame to rotate axially.

[0012] A further improvement is that the circuit board is mounted on the star sensor body frame with screws, making installation and disassembly very convenient.

[0013] A further improvement is that the thermal pad is attached to the inside of the circuit board to facilitate heat conduction.

[0014] A further improvement is that the thermal pad is a non-metallic thermal pad, preferably a rubber thermal pad, to protect the circuit board and prevent the chips on the circuit board from colliding with the metal materials when in a vibrating environment.

[0015] A further solution is to attach thermal pads to the inner perimeter and bottom of the circuit board, allowing the thermal pads to transfer heat tangentially to the star sensor body frame.

[0016] A further solution is to use a thermal pad with a thermal conductivity of 16 (W / m·℃), which can effectively transfer the heat generated by the chip to the star sensor body frame, thereby reducing the temperature of the circuit board.

[0017] The star sensor's detection lens is mounted on the star sensor's main frame. To maintain the stability and reliability of star measurement, it is necessary to minimize the impact of external vibrations. Therefore, this structure selects higher-strength aerospace-grade aluminum 7075-T651 to increase the resonant frequency at the star sensor's main body, and reinforces the azimuth mounting flange with ribs.

[0018] According to the modal frequency calculation formula:

[0019]

[0020] In the formula: ω is the modal frequency; k is the stiffness; m is the mass.

[0021] As shown in the above formula, in addition to increasing the system stiffness, the mass can also be reduced, thereby increasing the modal frequency. Therefore, while adding reinforcing ribs to the flange at the azimuth position, weight reduction was also implemented.

[0022] A further improvement is that the PEEK housing is connected to the circuit board via screws, spring washers, and flat washers, making installation and disassembly very convenient.

[0023] In high-temperature environments: To prevent the outer casing from transferring heat to the circuit board through radiation, this invention sets a shell of low thermal conductivity PEEK material on the outside of the circuit board, and sets high thermal conductivity rubber thermal pads around the circuit board and at the bottom to transfer the heat generated by the chips on the circuit board to the star sensor body bracket.

[0024] In low-temperature environments: To prevent the circuit board from operating normally due to excessively low temperatures, this invention provides a heating film inside the PEEK material shell, which can heat the circuit board in low-temperature environments, enabling it to operate normally.

[0025] The present invention also discloses an astronomical navigation system that uses the aforementioned star sensor.

[0026] The beneficial effects of this invention are as follows:

[0027] By using a PEEK housing, the star sensor can be made suitable for high-temperature environments;

[0028] By incorporating a thermal pad, the star sensor can be adapted to high-temperature environments.

[0029] By setting a heating film on the circuit board, the star sensor can be adapted to low-temperature environments, ensuring that the star sensor can work normally in low-temperature environments. This avoids the problem that the circuit board in the star sensor is prone to failure when operating at low temperatures, which would lead to a decrease in the accuracy of the star sensor or even failure.

[0030] By setting up a rotating mechanism, the star sensor is designed to be radiation resistant, so that the star sensor body frame can avoid the effects of solar radiation and stray light through autonomous rotation (axial rotation), making the star sensor suitable for strong radiation environments.

[0031] This invention employs thermal isolation design from two aspects: reducing radiation temperature rise and heat conduction. This reduces the temperature rise of the circuit board in the star sensor when it operates in a high-temperature environment, reduces the impact of solar radiation on the star measurement function, and prevents the circuit board in the star sensor from easily malfunctioning when operating at high temperatures, which could lead to a decrease in the accuracy of the star sensor or even failure.

[0032] This invention improves the environmental adaptability of star sensors and enhances the reliability of the equipment. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a schematic diagram of the star sensor of the present invention;

[0035] Figure 2 This is a schematic diagram showing the change in the field of view before and after rotation;

[0036] In the diagram: 1. Star sensor body frame, 2. Thermal pad, 3. Circuit board, 4. PEEK housing, 5-7. Screws, spring washers and flat washers, 8. Orientation mounting flange, 9. Orientation shaft, 10. Heating film. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0038] Example 1

[0039] like Figure 1 As shown, a star sensor includes a detection lens, a star sensor body frame 1, a rotating mechanism, a circuit board 3, a thermal pad 2, a PEEK shell, and a heating film 10.

[0040] The detection lens is mounted on the star sensor frame 1. The rotation mechanism includes an azimuth axis 9, an angle sensor, a rotary motor, bearings, etc. The azimuth axis 9 is connected to the star sensor frame 1 via an azimuth mounting flange 8. The azimuth mounting flange 8 has a cutout with reinforcing ribs at the cutout, which improves rigidity, reduces weight, increases modal frequency, reduces the impact of external vibration, and improves the stability and reliability of satellite measurement. The angle sensor is mounted on the azimuth axis 9; the rotary motor is connected to the azimuth axis 9. The angle sensor collects the angle data of the azimuth axis 9 and transmits the data to the controller. The controller controls the rotary motor to operate based on the data, and the rotary motor drives the star sensor frame 1 to rotate axially. In this embodiment, the star sensor frame 1 is made of aviation-grade aluminum 7075-T651, thereby reducing the impact of external vibration and improving the stability and reliability of satellite measurement.

[0041] Note: A rotary motor is a torque motor. Its stator is fixed to the housing of the star sensor, and the rotor is connected to the azimuth axis via a key. The rotor transmits torque to the azimuth axis, causing the azimuth axis to rotate. It is fixed to the azimuth axis by a pressure ring.

[0042] The circuit board 3 is mounted on the star sensor frame 1 with screws. A thermal pad 2 is placed between the circuit board 3 and the star sensor frame 1, and is attached to the inner perimeter and bottom of the circuit board 3 to transfer the heat generated by the chip on the circuit board 3 to the star sensor frame 1. In this embodiment, the thermal pad 2 is a non-metallic thermal pad with a thermal conductivity of 16 (W / m·℃).

[0043] The PEEK housing 4 is connected to the circuit board 3 via screws 5, spring washers 6, and flat washers 7. The PEEK housing 4 can isolate radiant heat from high-temperature environments. A heating film 10 is placed between the PEEK housing 4 and the circuit board 3, and the heating film 10 can heat the circuit board 3.

[0044] The principle is as follows:

[0045] 1) When solar radiation and stray light are strong, the rotary motor drives the azimuth axis 9, the azimuth mounting flange 8, and the star sensor body frame 1 to rotate, thereby avoiding the influence of strong stray light and improving the accuracy of star measurement by the star sensor. The change in field of view before and after rotation is as follows: Figure 2 As shown. At certain angles, solar radiation can reach the outer casing on the side of the circuit board. By rotating the shaft system, strong stray sunlight is avoided, thus reducing solar radiation.

[0046] 2) Since the star sensor operates in a high-altitude environment with thin air, its main heat transfer methods are thermal conduction and radiative heat transfer. When the star sensor operates in a high-temperature environment, in order to reduce the temperature rise of circuit board 3, it is necessary to transfer the heat generated by the chip in circuit board 3 as much as possible, and then minimize the amount of heat transferred to circuit board 3 by the external environment through radiative heat transfer.

[0047] This invention attaches a thermal pad 2 to the chip on the circuit board 3, transferring the heat generated by the chip to the star sensor body frame 1 via the thermal pad 2. A PEEK shell isolates the radiant heat from the high-temperature external environment.

[0048] The fundamental law of heat transfer is that heat flows from a high-temperature region to a low-temperature region. The basic formula for its calculation is: Q = KAΔt. Where Q is the heat flow rate (W), and K is the heat transfer coefficient (W / m³). 2 ·℃), A is the heat exchange area (m²) 2 Δt is the temperature difference (°C) between the hot and cold fluids. Heat conduction is the heat transfer phenomenon between the same or different media due to temperature differences. The fundamental law of heat conduction is Fourier's law, which represents the heat flow rate through a given area per unit time. The heat flow rate of conduction is proportional to the temperature gradient and the cross-sectional area perpendicular to the direction of heat conduction. The expression for heat conduction is:

[0049] In the formula, Q is the heat flux (W), λ is the thermal conductivity of the material (W / m·℃), and A is the cross-sectional area perpendicular to the heat conduction direction (m²). 2 ), This represents the temperature gradient (°C / m) along the normal direction of the isothermal surface.

[0050] As can be seen from the above formula, to increase the heat transfer Q, materials with high thermal conductivity need to be selected. Generally, metals have high thermal conductivity, followed by non-metals, liquids have low thermal conductivity, and gases have the lowest. For the purpose of protecting circuit board 3, the chip on circuit board 3 cannot be directly bonded to metal materials for heat conduction, to avoid collisions between the chip and the metal material in a vibrating environment. Therefore, a non-metallic thermal pad is used for heat transfer between the star-sensor frame and the chip on circuit board 3. The thermal pad is a rubber thermal pad made of carbon fiber with high thermal conductivity, uniformly and vertically filled with silicone rubber. Its thermal conductivity can reach 16 (W / m·℃), which can effectively transfer the heat generated by the chip to the star-sensor frame 1, thereby reducing the temperature of circuit board 3.

[0051] Furthermore, since circuit board 3 is typically a composite material consisting of FR4 and multiple layers of copper foil, and the distribution of each copper foil layer is uneven, the circuit board exhibits anisotropic thermal conductivity. Different circuit boards have different thermal conductivity, but most circuit boards have a low normal thermal conductivity, approximately 0.4 (W / m·℃), and tangential thermal conductivity coefficients of approximately 30–40 (W / m·℃). Based on the anisotropic thermal conductivity characteristics of the circuit board, thermal pads 2 are used around circuit board 3 to transfer heat tangentially along the circuit board 3, ultimately transferring it to the star-sensor body frame 1 via the thermal pads 2.

[0052] Besides the heat generated by the chip, the high temperature of the star sensor casing continuously radiates heat into the interior, causing the temperature of circuit board 3 to rise. Unlike conduction and convection heat transfer, the process by which an object transfers energy outward in the form of electromagnetic waves is called thermal radiation. Any object above absolute zero radiates energy outward at a certain wavelength and also receives energy radiated from the outside. Thermal radiation does not require any medium, can transfer energy in the air, and the energy can be converted, i.e., thermal energy is converted into radiant energy or radiant energy is converted into thermal energy. This invention uses a special engineering plastic—PEEK (polyetheretherketone) material—to mount the casing on the outside of the circuit board to reduce the temperature rise caused by radiation. PEEK material has a low thermal conductivity of only 0.3 (W / m·℃), and the energy passing through PEEK material per unit time is relatively small, allowing a large temperature difference to be maintained between the outer and inner surfaces of the PEEK material. This reduces the heat radiated from the inner surface of the PEEK material to the circuit board, thereby reducing the temperature rise of the circuit board.

[0053] (3) When the ambient temperature is low and the internal temperature of the star sensor is lower than the set temperature Tset, the heating film 10 starts to work, so that the circuit board 3 works within the normal temperature range.

[0054] This invention improves the environmental adaptability of existing star sensors by modifying them.

[0055] Example 2

[0056] An astronomical navigation system employing the star sensor described in Example 1.

[0057] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0058] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A star sensor, characterized in that: Includes a detection lens, star sensor body frame, rotation mechanism, circuit board, thermal pad, heating film, and PEEK housing; The detection lens is mounted on the star sensor body frame; The rotating mechanism is connected to the star sensor body frame, causing the star sensor body frame to rotate axially; The circuit board is mounted on the star sensor frame; a thermal pad is placed between the circuit board and the star sensor frame to transfer the heat generated by the chips on the circuit board to the star sensor frame; the thermal pad is attached to the inner perimeter and bottom of the circuit board, allowing it to transfer heat tangentially along the circuit board to the star sensor frame; a heating film and a PEEK shell are sequentially arranged on the outer side of the circuit board. The heating film heats the circuit board, and the PEEK shell isolates the radiant heat from the high-temperature environment; the thermal conductivity of the PEEK shell is 0.

3. ).

2. The star sensor according to claim 1, characterized in that: The rotating mechanism includes an azimuth axis, an angle sensor, and a rotary motor; The azimuth axis is connected to the star sensor body frame via an azimuth mounting flange; The angle sensor is mounted on the azimuth axis; the angle sensor collects the angle data of the azimuth axis and transmits the data to the controller, which controls the rotary motor to work based on the data, and the rotary motor drives the star sensor body frame to rotate axially.

3. The star sensor according to claim 1, characterized in that: The circuit board is mounted on the star sensor body frame with screws.

4. The star sensor according to claim 1, characterized in that: The thermal pad is attached to the inside of the circuit board.

5. The star sensor according to claim 1, characterized in that: The thermal pad is a non-metallic thermal pad.

6. The star sensor according to claim 1, characterized in that: The thermal conductivity of the thermal pad is 16 ( ).

7. The star sensor according to claim 1, characterized in that: The PEEK housing is connected to the circuit board via screws, spring washers, and flat washers.

8. The star sensor according to claim 2, characterized in that: The mounting flange has a perforation, and reinforcing ribs are provided in the perforation; The star sensor body frame is made of aviation aluminum 7075-T651.

9. An astronomical navigation system, characterized in that: The astronomical navigation system employs a star sensor as described in any one of claims 1-8.

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