Star sensor and celestial navigation system

Abstract

The invention discloses a star sensor which comprises a detection lens, a star sensor body frame, a rotating mechanism, a circuit board, a heat conduction pad, a heating film and a PEEK shell, the detection lens is mounted on the star sensor body frame; the rotating mechanism is connected with the star sensor body frame, so that the star sensor body frame axially rotates; the circuit board is arranged on the star sensor body frame; the heat conduction pad is arranged between the circuit board and the star sensor body frame and transfers heat generated by a chip of the circuit board to the star sensor body frame; the heating film and the PEEK shell are sequentially arranged on the outer side of the circuit board, the heating film can heat the circuit board, and the PEEK shell can isolate radiation heat in a high-temperature environment. The invention also discloses a celestial navigation system. The device can adapt to severe environments such as high and low temperatures and intense radiation, and the reliability of equipment is ensured.

Description

Technical Field

[0001] The invention belongs to the field of celestial body sensors, and in particular relates to a star sensor and a celestial navigation system. Background Art

[0002] Star sensors are currently widely used celestial sensors and are a very important component of celestial navigation systems. Star sensors often work in harsh environments such as high and low temperatures and strong radiation. Existing star sensors usually lack the means to adjust their orientation and are often interfered by solar radiation and stray light, which affects their star-measuring function. Moreover, the circuit boards in star sensors are prone to failure when working in high and low temperature environments, resulting in reduced accuracy and even malfunction of the star sensor. Therefore, we urgently need a new star sensor. Summary of the invention

[0003] The main purpose of the present invention is to provide a star sensor and celestial navigation system which can adapt to harsh environments such as high and low temperatures, strong radiation, etc. and ensure the reliability of the equipment.

[0004] The technical solution adopted by the present invention is:

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

[0006] The detection lens is installed on the star-sensing body frame;

[0007] The rotating mechanism is connected to the star-sensing main frame to make the star-sensing main frame rotate axially;

[0008] The circuit board is installed on the Xingmin main frame; the thermal pad is placed between the circuit board and the Xingmin main frame to transfer the heat generated by the chip of the circuit board to the Xingmin main frame; the outer side of the circuit board is provided with a heating film and a PEEK shell in sequence, the heating film can heat the circuit board, and the PEEK shell can isolate the radiant heat from the high temperature environment.

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

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

[0011] The angle sensor is installed on the azimuth axis; the angle sensor collects angle data of the azimuth axis and transmits the data to the controller, and the controller controls the rotation motor to work according to the data, and the rotation motor drives the star-sensing body frame to rotate axially.

[0012] A further solution is that the circuit board is mounted on the Xingmin main frame by screws, which makes installation and disassembly very convenient.

[0013] A further solution is that the thermal pad is attached to the inner side of the circuit board to facilitate heat conduction.

[0014] A further solution is that the thermal pad is a non-metallic thermal pad, preferably a rubber thermal pad, for the purpose of protecting the circuit board and preventing the chip of the circuit board from colliding with the metal material in a vibration environment.

[0015] A further solution is to attach the thermal pad around the inner side and bottom of the circuit board so that the thermal pad transfers the heat to the Xingmin main frame along the tangent direction of the circuit board.

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

[0017] The detection lens of the star sensor is installed on the star sensor body frame. In order to maintain the stability and reliability of star measurement, it is necessary to minimize the impact of the external vibration environment. To this end, this structure selects the stronger aviation aluminum 7075-T651 from the perspective of increasing the resonance frequency of the star sensor body, and sets reinforcing ribs at the hollow part of the azimuth mounting flange.

[0018] According to the modal frequency calculation formula:

[0019]

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

[0021] From the above formula, we can know that in addition to improving the system stiffness, we can also reduce the mass, thereby increasing the modal frequency. Therefore, while adding reinforcement ribs to the azimuth mounting flange, we also reduced the weight.

[0022] A further solution is that the PEEK shell is connected to the circuit board through screws, spring washers and flat washers, which is very convenient for installation and disassembly.

[0023] In high temperature environment: In order to prevent the outer cover from transferring heat to the circuit board by radiation in a high temperature environment, the present 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 and on the bottom of the circuit board to transfer the heat generated by the chip of the circuit board to the Xingmin body bracket.

[0024] In a low temperature environment: In order to prevent the circuit board from being affected by excessively low temperature in a low temperature environment, a heating film is arranged on the inner side of the PEEK material shell in the present invention, so that the circuit board can be heated in a low temperature environment so that it can work normally.

[0025] The invention also discloses a celestial navigation system, which adopts the star sensor.

[0026] The beneficial effects of the present invention are:

[0027] By setting up a PEEK shell, the star sensor can be used in high temperature environments;

[0028] By setting a thermal pad, the star sensor can be used in high temperature environment;

[0029] By setting a heating film at the circuit board, the star sensor can be applied to low temperature environment, ensuring that the star sensor can work normally in low temperature environment, avoiding the problem that the circuit board in the star sensor is prone to failure when working in low temperature, resulting in reduced accuracy or even failure of the star sensor;

[0030] By setting a rotating mechanism, the star sensor is designed to resist radiation, so that the star sensor frame can avoid the influence of solar radiation and stray light by autonomous rotation (axial rotation), so that the star sensor can be used in strong radiation environments.

[0031] The present invention performs thermal isolation design from two aspects of reducing radiation temperature rise and heat conduction, so as to reduce the temperature rise of the circuit board in the star sensor when working in a high temperature environment, reduce the influence of solar radiation on the star measurement function, and prevent the circuit board in the star sensor from easily malfunctioning when working in a high temperature, resulting in the problem of reduced accuracy or even malfunction of the star sensor;

[0032] The invention improves the environmental adaptability of the star sensor and improves the reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

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

[0036] In the figure: 1. Xingmin main frame, 2. Thermal pad, 3. Circuit board, 4. PEEK shell, 5-7. Screws, spring washers and flat washers, 8. Azimuth mounting flange, 9. Azimuth axis, 10. Heating film. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present 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-sensing body frame 1. The rotating mechanism includes an azimuth axis 9, an angle sensor, a rotating motor, bearings, etc. The azimuth axis 9 is connected to the star-sensing body frame 1 through an azimuth mounting flange 8. The azimuth mounting flange 8 is provided with a hollow portion, and reinforcing ribs are provided at the hollow portion, which increases the rigidity and reduces the weight, increases the modal frequency, reduces the impact of the external vibration environment, and improves the stability and reliability of star measurement. The angle sensor is mounted on the azimuth axis 9; the rotating motor is connected to the azimuth axis 9, and the angle sensor collects the angle data of the azimuth axis 9 and transmits the data to the controller. The controller controls the rotating motor to work according to the data, and the rotating motor drives the star-sensing body frame 1 to rotate axially. In this embodiment, the star-sensing body frame 1 is made of aviation aluminum 7075-T651, thereby reducing the impact of the external vibration environment and improving the stability and reliability of star measurement.

[0041] Note: The rotating motor is a torque motor, whose stator is fixedly connected to the outer shell of the star sensor, and the rotor is connected to the azimuth shaft through a key, which transmits the torque to the azimuth shaft, drives the azimuth shaft to rotate, and is fixed to the azimuth shaft by means of a pressing ring.

[0042] The circuit board 3 is installed on the Xingmin body frame 1 by screws. The thermal pad 2 is placed between the circuit board 3 and the Xingmin body frame 1, and is attached to the inner sides and bottom of the circuit board 3 to transfer the heat generated by the chip of the circuit board 3 to the Xingmin body 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 shell 4 is connected to the circuit board 3 through screws 5, spring washers 6, and flat washers 7. The PEEK shell 4 can isolate the radiant heat of the high temperature environment. The heating film 10 is placed between the PEEK shell 4 and the circuit board 3, and the heating film 10 can heat the circuit board 3.

[0044] The principle is:

[0045] 1) When the solar radiation and stray light are strong, the rotating 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 sensor star measurement. Figure 2 At certain angles, solar radiation will hit the housing on the circuit board side. By rotating the shaft system, the strong stray light from the sun is avoided and the solar radiation is reduced.

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

[0047] The present invention attaches the thermal pad 2 to the chip of the circuit board 3, and transfers the heat generated by the chip to the Xingmin main frame 1 through the thermal pad 2. The radiant heat from the external high temperature environment is isolated by the PEEK shell.

[0048] The basic law of heat transfer is that heat is transferred from a high temperature area to a low temperature area. The basic calculation formula is: Q = KAΔt. In the formula, Q is the heat flow (W), K is the heat transfer coefficient (W / m 2 ·℃), A is the heat exchange area (m 2 ), Δt is the temperature difference between the hot and cold fluids (℃). Heat conduction is the heat transfer phenomenon caused by temperature difference between the same medium or different media. The basic law of heat conduction is given by Fourier's law, which expresses the heat flow through a given area per unit time. The heat flow of conduction is proportional to the temperature gradient and the cross-sectional area perpendicular to the heat conduction direction. The expression of heat conduction is:

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

[0050] It can be seen from the above formula that in order to increase the heat Q transferred by heat conduction, it is necessary to select materials with high thermal conductivity. Generally speaking, metals have higher thermal conductivity, followed by non-metals, lower liquids, and the smallest gas. For the purpose of protecting the circuit board 3, the chip of the circuit board 3 cannot be directly bonded to the metal material for heat conduction to avoid collision between the chip and the metal material when in a vibration environment. Therefore, heat is transferred between the Xingmin main frame and the chip of the circuit board 3 through a non-metallic thermal pad. The thermal pad is a rubber thermal pad uniformly filled with carbon fiber with high thermal conductivity 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 Xingmin main frame 1, thereby reducing the temperature of the circuit board 3.

[0051] In addition, since the circuit board 3 is usually a composite material composed of FR4 and multiple layers of copper foil, and the distribution of each layer of copper foil is different, the circuit board exhibits anisotropic thermal conductivity. Different circuit boards have different thermal conductivities, but the normal thermal conductivity of most circuit boards is low, about 0.4 (W / m·℃), and the two tangential derivative coefficients are about 30-40 (W / m·℃). According to the anisotropic thermal conductivity characteristics of the circuit board, thermal pads 2 are used around the circuit board 3 to transfer heat along the tangential direction of the circuit board 3, and finally transferred to the Xingmin main frame 1 through the thermal pads 2.

[0052] In addition to the heat generated by the chip, the high temperature of the star sensor housing will continue to radiate heat to the inside, causing the temperature of the circuit board 3 to rise. Unlike conduction and convection heat transfer, the process by which an object transfers energy to the outside in the form of electromagnetic waves is called thermal radiation. Any object above absolute zero radiates energy to the outside at a certain wavelength, and also receives energy radiated to it from the outside. Thermal radiation does not require any medium, can transfer energy in the air, and the energy can be converted, that is, thermal energy is converted to radiation energy or radiation energy is converted to thermal energy. The present invention uses a special engineering plastic-PEEK (polyetheretherketone) material housing installed on the outside of the circuit board to reduce the temperature rise caused by radiation. The thermal conductivity of PEEK material is low, only 0.3 (W / m·℃), and the energy passing through PEEK material per unit time is small, so that the outer surface and inner surface of the PEEK material can maintain a large temperature difference, which can reduce 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 a normal temperature range.

[0054] The present invention improves the environmental adaptability of the star sensor by improving the existing star sensor.

[0055] Example 2

[0056] A celestial navigation system adopts the star sensor in embodiment 1.

[0057] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

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

Claims

1. A star sensor, characterized in that: Including detection lens, star-sensing body frame, rotating mechanism, circuit board, thermal pad, heating film, PEEK shell; The detection lens is installed on the star-sensing body frame; The rotating mechanism is connected to the star-sensing main frame to make the star-sensing main frame rotate axially; The circuit board is installed on the Xingmin main frame; the thermal pad is placed between the circuit board and the Xingmin main frame to transfer the heat generated by the chip of the circuit board to the Xingmin main frame; the outer side of the circuit board is provided with a heating film and a PEEK shell in sequence, the heating film can heat the circuit board, and the PEEK shell can isolate the radiant heat from the high temperature environment.

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

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

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

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

6. The star sensor according to claim 1, 4 or 5, characterized in that: The thermal pad is attached to the inner sides and bottom of the circuit board so that the thermal pad transfers the heat to the Xingmin main frame along the tangent direction of the circuit board.

7. The star sensor according to claim 6, characterized in that: The thermal conductivity of the thermal pad is 16 (W / m·℃).

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

9. The star sensor according to claim 2, characterized in that: A hollow is provided on the azimuth mounting flange, and reinforcing ribs are provided at the hollow; The Xingmin main frame is made of aviation aluminum 7075-T651.

10. A celestial navigation system, characterized in that: The celestial navigation system adopts the star sensor described in any one of claims 1-9.

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