Spaceborne Antenna Embedded Dual-Parameter Fiber Bragg Grating Sensing System and Its Embedding Method in Spaceborne Antenna

Abstract

The present invention provides an embedded dual-parameter fiber Bragg grating sensing system for spaceborne antennas and a pre-embedding method thereof in spaceborne antennas. The dual-parameter sensor includes a high-precision fiber Bragg grating written by femtosecond laser and a packaging material, and the two together form a fiber detection end buried between the upper panel of the spaceborne antenna and the paper honeycomb. First, a temperature reference grating is written based on the femtosecond laser with the fiber core as the center. Secondly, a measurement grating is written with the fiber with the cladding removed, and an integrated temperature and strain dual-parameter sensor is made by combining a sleeve and anti-radiation paint. Then, its full-spectrum signal is demodulated, and finally it is encapsulated and buried in the antenna. This sensing system has the advantages of high freedom, high temperature resistance, anti-space radiation, and real-time monitoring, and is suitable for the health monitoring of spaceborne antennas.

Description

Technical fields:

[0001] This invention belongs to the field of fiber optic sensing technology, specifically relating to a spaceborne antenna embedded dual-parameter fiber optic grating sensing system and its pre-embedding method in the spaceborne antenna, which can be applied to the field of real-time high-precision monitoring of on-orbit antenna deformation. Background technology:

[0002] On-orbit satellite antennas are an indispensable structure in satellite systems and an essential monitoring tool for aerospace satellite systems. In recent years, with the in-depth development of aerospace satellite technology, higher requirements have been placed on the high-precision health monitoring of satellite antennas under long-term operating conditions. Among them, the cellular panel is one of the main forms of antenna and a key component of the satellite system. Currently, high-precision real-time deformation monitoring of on-orbit antennas is a technical problem that urgently needs to be solved. Temperature and strain are the main parameters for monitoring antenna panels. Traditional measurement methods using thermocouples and strain gauges are not conducive to packaging and integration, and are not suitable for high-precision monitoring in extreme environments. Therefore, it is necessary to explore new sensing systems that meet the requirements of lightweight, embedded design, high measurement accuracy, high sampling frequency, and high reliability. Based on this, this invention provides a satellite antenna embedded dual-parameter fiber optic grating sensing system and its pre-embedding method in the satellite antenna to solve the above problems. Summary of the Invention:

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a spaceborne antenna embedded dual-parameter fiber Bragg grating sensing system and its pre-embedding method in the spaceborne antenna. Based on femtosecond laser high-precision writing technology and fiber distributed packaging embedding method, it fabricates a high-precision health monitoring system suitable for real-time deformation and temperature monitoring of on-orbit antennas. It features high integration, high temperature resistance, resistance to space radiation, real-time monitoring capability, and a lightweight, embedded design.

[0004] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution:

[0005] (I) This invention provides a spaceborne antenna embedded dual-parameter fiber optic grating sensing system, comprising a femtosecond laser-written temperature reference fiber optic grating and a measurement fiber optic grating. The temperature reference fiber optic grating and the measurement fiber optic grating are assigned to a sensing node, on which two types of fiber optic gratings, one for temperature reference and one for strain measurement, are installed. The temperature reference fiber optic grating is not affected by strain and is only sensitive to temperature. The temperature reference fiber optic grating and the measurement fiber optic grating are embedded between the upper panel of the spaceborne antenna and the paper honeycomb structure. The temperature and strain of the spaceborne antenna are monitored in real time by using a fiber optic grating temperature and strain monitoring system to demodulate the temperature and strain corresponding to the wavelength change of the fiber optic grating.

[0006] Furthermore, the temperature reference fiber grating and the measurement fiber grating are coated with an anti-space radiation coating to increase the anti-space radiation effect of the sensor and ensure its stability and anti-space radiation characteristics during long-term operation.

[0007] (II) This invention also provides a method for pre-embedding a spaceborne antenna in a spaceborne antenna for a spaceborne antenna-embedded dual-parameter fiber Bragg grating sensing system, specifically including the following steps:

[0008] S1. Determine the pre-embedded position and number of fiber optic gratings on the top panel. The pre-embedded position of the fiber optic gratings is between the top panel of the spaceborne antenna and the paper honeycomb.

[0009] S2. Based on the fiber optic grating pre-embedded positions and number set in step S1, plan the fiber optic arrangement and fix the temperature reference fiber optic grating and the measuring fiber optic grating on the lower surface of the upper plate with glue.

[0010] S3. Fix the top panel, paper honeycomb and bottom panel by hot pressing.

[0011] Furthermore, in S2, the method for fixing the temperature reference fiber grating and the measurement fiber grating on the upper plate is as follows: First, use glue to fix both ends of the measurement fiber grating to the fiber grating pre-embedded position on the upper plate, and apply a certain amount of pre-strain to the grating area of ​​the measurement fiber grating; after the glue dries, use glue to fix one end of the temperature reference fiber grating to the fiber grating pre-embedded position, and try to avoid the other end being affected by the deformation of the upper plate, so that the temperature reference fiber grating is not affected by strain.

[0012] Furthermore, in S2, the fiber coating material of both the temperature reference fiber grating and the measurement fiber grating is polyimide, with an operating temperature range of -50℃ to 300℃ and high mechanical strength. In addition, an anti-space radiation coating (fluoropolymer coating) is applied to both the temperature reference fiber grating and the measurement fiber grating to enhance the sensor's resistance to space radiation, ensuring its stability and anti-space radiation characteristics during long-term operation.

[0013] Furthermore, in step S2, after the temperature reference fiber grating and the measuring fiber grating are fixed to the top plate, the top plate is moved so that the grating areas of the two fiber gratings correspond to the center positions of the regular hexagons of the paper honeycomb. Then, the top plate, the paper honeycomb, and the bottom plate are hot-pressed together to fix them. After hot-pressing, the grating areas of the two fiber gratings correspond to the center positions of the regular hexagons of the paper honeycomb, thereby preventing the paper honeycomb from squeezing and damaging the fiber gratings.

[0014] Furthermore, the cross-section of the paper honeycomb is a regular hexagon, and the distance between the two parallel sides is 2.75 mm. To avoid the two fiber gratings being squeezed and damaged by the honeycomb plate wall, the grating area length of the temperature reference fiber grating and the measuring fiber grating is set to 2 mm.

[0015] Furthermore, since the two fiber gratings are easily subjected to strong shearing forces during the hot pressing process of the three-layer structure of the spaceborne antenna, a protective sleeve is fixedly sleeved on the grating area of ​​the temperature reference fiber grating to protect the grating area and reduce the compression of the fiber grating by the honeycomb plate wall; the protective sleeve is glued to the grating area of ​​the temperature reference fiber grating.

[0016] Furthermore, a circular area with a radius of approximately 2 cm is defined centered on the grating region of the temperature reference fiber optic grating. No curing adhesive is applied to this circular area during the subsequent curing process. The curing adhesive is the adhesive for the three-layer structure of the spaceborne antenna. The purpose of setting up the no-adhesion area is to prevent the curing adhesive from interfering with the temperature reference fiber optic grating.

[0017] Furthermore, when fixing one end of the temperature reference fiber optic grating to the top panel, first cross the pigtails at both ends of the protective sleeve to form an elliptical ring around the outside of the protective sleeve. Then, attach and fix one end of the pigtail to the top panel, and wrap the other end of the pigtail around one or more small loops to increase the dynamic deformation range of the temperature reference fiber optic grating and isolate the deformation interference of the top panel to the greatest extent.

[0018] Furthermore, a groove with a depth of approximately 5 mm is formed on the upper part of the paper honeycomb. The position of the groove is determined on the honeycomb plate according to the preset placement position of the fiber Bragg grating sensor. The groove corresponds to the grating area position of the two fiber Bragg gratings. After the upper panel, paper honeycomb and lower panel are hot-pressed, the groove can completely cover the grating area of ​​the two fiber Bragg gratings fixed on the upper panel. A high-temperature resistant film is provided on the inner surface of the groove to improve the safety of the fiber Bragg grating sensor.

[0019] Furthermore, the adhesive is an epoxy resin adhesive, which is resistant to high temperatures and can still maintain its stickiness after 48 hours at room temperature.

[0020] The beneficial effects of this invention are:

[0021] (1) The present invention provides a spaceborne antenna embedded dual-parameter fiber grating sensing system, which embeds a customized array fiber grating inside the antenna material to realize online monitoring and data accumulation of the spaceborne antenna, increases the sensor’s strain transmission efficiency, and enhances the protection of the fiber grating sensor.

[0022] (2) Based on the analysis of the temperature field and strain field working conditions of the spaceborne antenna, this invention can simultaneously write multiple gratings on a single optical fiber at a set interval, which reduces the operational difficulty of a single grating splice point and reduces time costs.

[0023] (3) In this invention, when fixing one end of the temperature reference fiber optic grating to the top plate, the pigtails at both ends of the protective sleeve are crossed to form an elliptical ring around the outside of the protective sleeve. Then, one end of the pigtail is pasted and fixed to the top plate, and the other end of the pigtail is wound out one or more small rings. This can increase the dynamic deformation range of the reference fiber optic grating, isolate the deformation interference of the top plate to the greatest extent, and improve the temperature measurement reliability and accuracy of the fiber optic grating.

[0024] (4) Compared with traditional measurement methods, this invention has the advantages of high integration, high temperature resistance, resistance to space radiation, real-time monitoring capability, and lightweight embedded design. This invention can be effectively used in integrated on-orbit antenna real-time deformation monitoring systems to achieve high-precision monitoring of minute deformations of the antenna surface structure. Attached image description:

[0025] Figure 1 This is a schematic diagram of the antenna pre-embedded position according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the sensing device structure according to an embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of the paper honeycomb groove structure according to an embodiment of the present invention;

[0028] Figure 4 This is a distribution diagram of strain gauges and thermocouples in a comparative experiment of an embodiment of the present invention;

[0029] Figure 5 This is a measured temperature-time relationship graph from an embodiment of the present invention.

[0030] Figure 6 This is a measured strain-time relationship diagram from an embodiment of the present invention.

[0031] The labels in the attached diagram are:

[0032] 1. Top panel; 2. Honeycomb panel; 3. Bottom panel; 4. Fiber Bragg grating embedded position; 5. Heating equipment; 6. Measuring fiber Bragg grating; 7. Temperature reference fiber Bragg grating; 8. Protective sleeve; 9. Measuring fiber Bragg grating grating area; 10. Circular non-glued area; 11. Epoxy resin adhesive; 12. Fiber Bragg grating temperature and strain monitoring system; 13. Groove; 14. Strain gauge one; 15. Strain gauge two; 16. Strain gauge three; 17. Thermocouple. Detailed implementation method:

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] This invention proposes a spaceborne antenna embedded dual-parameter fiber Bragg grating sensing system and its pre-embedding method in the spaceborne antenna. Based on the high-precision writing process of femtosecond laser and the fiber distributed packaging embedding method, and combined with the specific advantages of different fiber Bragg gratings, a high-precision health monitoring system suitable for real-time deformation of on-orbit antennas is produced.

[0035] Example 1

[0036] This invention provides a spaceborne antenna embedded dual-parameter fiber optic grating sensing system, comprising a femtosecond laser-written temperature reference fiber optic grating 7 and a measurement fiber optic grating 6. The temperature reference fiber optic grating 7 and the measurement fiber optic grating 6 are assigned to a sensing node, which is equipped with both temperature reference and strain measurement fiber optic gratings. The temperature reference fiber optic grating 7 is not affected by strain and is only sensitive to temperature. The temperature reference fiber optic grating 7 and the measurement fiber optic grating 6 are embedded between the upper panel 1 and the paper honeycomb 2 of the spaceborne antenna. Wavelength data is collected using a fiber optic grating temperature and strain monitoring system 12, and the temperature and strain corresponding to the wavelength change of the fiber optic grating are demodulated to monitor the temperature and strain of the spaceborne antenna in real time.

[0037] Example 2

[0038] This invention provides a method for pre-embedding a spaceborne antenna in a spaceborne antenna for a spaceborne antenna-embedded dual-parameter fiber Bragg grating sensing system, specifically as follows:

[0039] (I) Determination of fiber Bragg grating embedding locations, number of fiber Bragg gratings, and preprocessing of fiber Bragg gratings:

[0040] Based on the antenna reconfiguration model, the fiber optic grating pre-embedded position 4 and the number of fiber optic gratings are determined on the upper panel 1 of the antenna. The fiber optic grating pre-embedded position 4 is located between the upper panel 1 of the spaceborne antenna and the paper honeycomb 2.

[0041] The fiber coating material of the temperature reference fiber grating 7 is polyimide, with an operating temperature range of -50℃ to 300℃ and high mechanical strength. Furthermore, both the temperature reference fiber grating 7 and the measurement fiber grating 6 are coated with an anti-space radiation coating (fluoropolymer coating) to enhance the sensor's resistance to space radiation, ensuring its long-term operational stability and anti-space radiation characteristics.

[0042] Protective sleeves 8 are fixedly fitted onto the grating areas (2mm) of the temperature reference fiber grating 7 and the measuring fiber grating 6 to protect the grating areas and reduce the pressure of the honeycomb plate 2 wall on the fiber gratings. The protective sleeves 8 are glued to the outer surfaces of the grating areas of the temperature reference fiber grating 7 and the measuring fiber grating 6 with epoxy resin.

[0043] (II) Performing the internal embedding operation:

[0044] The fiber optic cable layout is planned based on the pre-embedded locations and number of fiber optic gratings. For example... Figure 2 As shown, a temperature reference fiber grating 7 and a measurement fiber grating 6 are placed on the upper panel 1 of the antenna.

[0045] During the embedding operation, the method for fixing the temperature reference fiber grating 7 and the measuring fiber grating 6 to the upper plate 1 is as follows: First, use glue (epoxy resin) to fix both ends of the measuring fiber grating 6 to the fiber grating pre-embedded position 4 on the upper plate 1, and apply a certain amount of pre-strain to the grating area 9 of the measuring fiber grating, and wait for the glue to air dry. Then, use glue (epoxy resin) to fix one end of the temperature reference fiber grating 7 to the fiber grating pre-embedded position 4. In order to avoid the temperature reference fiber grating 7 being interfered with by the deformation of the upper plate 1 and to increase the temperature measurement stability and reliability of the temperature reference fiber grating 7, in other embodiments of the present invention, when fixing the temperature reference fiber grating 7, the pigtails at both ends of the protective sleeve 8 can be crossed around the outer periphery of the protective sleeve 8 to form an elliptical ring. Then, one end of the pigtail is glued to the upper plate 1, and the other end of the pigtail is wound into one or more small loops to increase the dynamic deformation range of the temperature reference fiber grating 7, which can isolate the deformation interference of the upper plate 1 to the greatest extent.

[0046] A circular non-adhesive area 10 with a radius of approximately 2 cm is defined with the grating region of the temperature reference fiber optic grating 7 as the center. No curing adhesive is poured into the circular non-adhesive area 10 during the subsequent curing process. The curing adhesive is the adhesive for the three-layer structure of the spaceborne antenna. The purpose of setting the non-adhesive area 10 is to prevent the curing adhesive from interfering with the temperature reference fiber optic grating 7.

[0047] A groove 13 with a depth of about 5mm is dug in the paper honeycomb 2. The groove 13 corresponds to the grating area of ​​the two fiber optic gratings. After the upper panel 1, the paper honeycomb 2 and the lower panel 3 are hot-pressed, the groove 13 can completely cover the grating area of ​​the two fiber optic gratings fixed on the upper panel 1, further avoiding the squeezing damage of the gratings by the paper honeycomb 2. A high-temperature resistant film is provided on the inner surface of the groove 13 to improve the safety of the fiber optic grating sensor.

[0048] (III) Hot pressing fixation:

[0049] After the internal embedding operation is completed, the upper panel 1, paper honeycomb 2 and lower panel 3 are hot-pressed and fixed to form the pre-embedding.

[0050] Example 3

[0051] The measurement accuracy of the fiber optic sensing system after pre-embedding in Example 2 was tested.

[0052] Specifically, the spaceborne antenna board is cut into small antenna sub-boards, which are used as sensing media. Thermocouples and strain gauge systems are used to detect the measurement accuracy of the fiber optic sensing system.

[0053] The specific parameters of the fiber optic sensing system include: the center wavelength of the reflection peak of the temperature reference fiber grating 7 is in the 1505nm band, the center wavelength of the reflection peak of the measurement fiber grating 6 is in the 1570nm band, the full width at half maximum (FWHM) of the two grating reflection peaks is about 0.24nm, and the signal-to-noise ratio of the grating can reach 27.7dB.

[0054] The curing adhesive used is epoxy resin, which can withstand high temperatures and maintain its tack for more than 48 hours at room temperature.

[0055] The heating device 5 was placed at the bottom of the antenna sub-board and heated from room temperature to 80°C, then held at that temperature for about 1 minute to ensure that the maximum temperature of the fiber optic grating sensor and thermocouple remained constant and the maximum strain value of the antenna sub-board remained stable. Finally, the wavelength data was demodulated using the fiber optic grating temperature and strain monitoring system 12, with a data acquisition frequency of 1 kHz, and the data was saved as an average of 10 times.

[0056] By heating the antenna sub-board, a temperature / strain-time relationship graph was obtained, such as... Figure 5 and Figure 6 As shown. The comparison measurement settings are as follows. Figure 4 As shown, thermocouple 17 is attached to the upper panel corresponding to the fiber optic grating and is used to monitor temperature changes. Strain gauge 14, strain gauge 2 15, and strain gauge 3 16 are used to monitor the strain of the antenna sub-board at this location.

[0057] Temperature change experimental data such as Figure 5 The wavelength data is the result of 10 averages (testing one sensor node). The temperature is calculated using its respective calibration coefficients and compared with the value of thermocouple 17. The temperature data is processed according to the temperature reference fiber optic grating calibration coefficients. Figure 5 As can be seen, the temperature change curve of the fiber optic grating matches the curve of thermocouple 17 quite well, and their trends are similar. The temperature difference between the two may originate from internal temperature measurement in one case and external measurement in the other. The slight shift in the positions of the two highest temperature points is due to the different response times of the grating and strain gauge to temperature. The abrupt change in the curve during the final natural cooling process is caused by the removal of the insulation material from the antenna surface.

[0058] Strain test data such as Figure 6The strain is calculated using a fiber Bragg grating and compared with the values ​​measured by the compensated strain gauge. For example... Figure 6 As can be seen, when demodulated using the temperature of the fiber Bragg grating as a reference, the strain measured by strain gauge two after compensation is almost identical to the strain curve measured by the fiber Bragg grating. The main reason for the difference between the strain measured by strain gauge one and strain gauge three after compensation and the demodulated fiber Bragg grating strain value is the difference in the bonding position on the upper panel, but the trend of their strain values ​​is consistent. During the cooling process of the antenna honeycomb panel, a small abrupt change occurred in the curve, which was caused by the removal of the insulation material covering the upper surface of the antenna honeycomb panel.

[0059] Therefore, the spaceborne antenna embedded dual-parameter fiber optic grating sensing system of the present invention has good measurement accuracy and can be effectively used in an integrated on-orbit antenna real-time deformation monitoring system to achieve high-precision monitoring of minute deformations of the antenna surface structure.

[0060] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for embedding a satellite-borne antenna embedded dual-parameter fiber grating sensing system in a satellite-borne antenna, characterized in that, include: S1. Determine the fiber optic grating pre-embedded position (4) and the number of fiber optic gratings on the top plate (1). The fiber optic grating pre-embedded position (4) is between the top plate (1) of the spaceborne antenna and the paper honeycomb (2). S2. Based on the fiber optic grating pre-embedded position (4) and number set in step S1, plan the fiber optic arrangement and fix the temperature reference fiber optic grating (7) and the measuring fiber optic grating (6) on the lower surface of the top plate (1). S3. The upper panel (1), paper honeycomb (2) and lower panel (3) are fixed by hot pressing; In S2, the method for fixing the temperature reference fiber grating (7) and the measurement fiber grating (6) on the top plate (1) is as follows: First, use glue to fix both ends of the measurement fiber grating (6) to the fiber grating pre-embedded position (4) on the top plate (1), and give the grating area (9) of the measurement fiber grating a certain amount of pre-strain; after the glue dries, use glue to fix one end of the temperature reference fiber grating (7) to the fiber grating pre-embedded position (4); the grating area of ​​the temperature reference fiber grating (7) is fixedly sleeved with a protective sleeve (8), and the protective sleeve (8) is glued to the grating area of ​​the temperature reference fiber grating (7); when fixing one end of the temperature reference fiber grating (7) to the top plate (1), first cross the pigtails at both ends of the protective sleeve (8) to form an elliptical ring around the protective sleeve (8), then glue one end of the pigtail to the top plate (1), and the other end of the pigtail is wound out one or more small rings to increase the dynamic deformation range of the temperature reference fiber grating (7); The embedded dual-parameter fiber optic grating sensing system for a spaceborne antenna includes a temperature reference fiber optic grating (7), a measurement fiber optic grating (6), and a fiber optic grating temperature and strain monitoring system (12). The temperature reference fiber optic grating (7) and the measurement fiber optic grating (6) are assigned to a sensing node, which is equipped with two types of fiber optic gratings: a temperature reference grating and a strain measurement grating. The temperature reference fiber optic grating (7) and the measurement fiber optic grating (6) are coated with anti-space radiation coating. The temperature reference fiber optic grating (7) and the measurement fiber optic grating (6) are embedded between the upper panel (1) and the paper honeycomb (2) of the spaceborne antenna. The fiber optic grating temperature and strain monitoring system (12) collects and demodulates the wavelength, thereby demodulating the temperature and strain corresponding to the change in the fiber optic grating wavelength and realizing real-time monitoring of the temperature and strain of the spaceborne antenna.

2. The pre-embedded method according to claim 1, characterized in that: The fiber coating material of both the temperature reference fiber grating (7) and the measurement fiber grating (6) is polyimide, and the operating temperature range is -50℃ to 300℃.

3. The pre-embedded method according to claim 1, characterized in that: In S2, after the temperature reference fiber grating (7) and the measuring fiber grating (6) are fixed on the top plate (1), the top plate (1) is moved so that the grating area of ​​the two fiber gratings corresponds to the center position of the regular hexagon of the paper honeycomb (2).

4. The pre-embedded method according to claim 1, characterized in that: The paper honeycomb (2) has a groove (13) on its upper part. The groove (13) corresponds to the grating area of ​​the two fiber optic gratings and completely covers the grating area of ​​the two fiber optic gratings. A high-temperature resistant film is provided on the inner surface of the groove (13).

5. The pre-embedded method according to claim 1, characterized in that: The paper honeycomb (2) has a regular hexagonal cross section and a distance of 2.75 mm between two parallel sides. The grating length of the temperature reference fiber optic grating (7) and the measuring fiber optic grating (6) is 2 mm.

6. The pre-embedded method according to claim 1, characterized in that: A circular non-insertion area (10) is defined with the grating area of ​​the temperature reference fiber grating (7) as the center. The circular non-insertion area (10) is not filled with curing adhesive.

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