A temperature detection system and method for a rocket

Abstract

The application provides a temperature detection system and method of a rocket, wherein the system comprises a light source, an isolator, a coupler, a photodetector, a control machine and a fiber grating network; the fiber grating network is composed of a plurality of fiber gratings, and the fiber grating network penetrates through the whole rocket body; the photodetector is used for detecting the reflection spectrum of reflected light reflected by the fiber grating network; the control machine is used for processing the reflection spectrum according to a reconstruction algorithm, obtaining a fiber grating reconstruction structure, comparing the fiber grating reconstruction structure with an original fiber grating structure, and then obtaining the temperature change value and the temperature change position of the fiber grating in the fiber grating network which has temperature change. The problems of the prior art, such as the limited detection range of the temperature sensor for the carrier rocket, the large occupied space and the complex temperature information demodulation method, are solved.

Description

Technical Field

[0001] This invention relates to the field of rocket technology, and in particular to a temperature detection system and method for rockets. Background Technology

[0002] Rockets are one of the most important tools for space exploration. The temperature of each electrical unit and structural component in the various compartments of a rocket determines to some extent whether the rocket can fly along its normal trajectory. Therefore, temperature detection has a significant impact on the safety of the entire rocket.

[0003] Traditional rocket temperature detection mainly relies on temperature data collected by temperature sensors in each section, which is then transmitted back to the integrated control unit. The sensors are mostly resistance temperature sensors.

[0004] This detection method still has the following shortcomings:

[0005] (1) Limited detection range: Most temperature sensors used in launch vehicles can only measure the location of the sensor, but a section of the rocket is usually only equipped with a certain number of sensors, which cannot cover the entire section.

[0006] (2) The detection device is large in size, heavy in weight, and has an invariable shape: the space of each section of the rocket is limited, and the traditional temperature detection device has a certain volume because it contains related electronic devices. In addition, each section is equipped with a temperature sensor, so it occupies a lot of space in the section.

[0007] (3) The temperature information demodulation method is complicated: For the widely used resistive temperature sensor, its temperature curve is nonlinear and has no analytical solution. The demodulation of its temperature information relies more on the table lookup method, which is complicated, increases the calculation time, and reduces the calculation efficiency.

[0008] In the prior art, invention patent CN110579227A discloses a time-division / wavelength-division multiplexed fiber optic grating distributed sensing system and method. This method meshes the fiber optic grating and utilizes the difference in reflected light time to locate the position to be detected. However, this method operates on a grating-by-grating basis, resulting in low detection accuracy, and requires comparing each scan result with the initial scan result, leading to a long detection time.

[0009] Chinese patent application CN108895974B discloses a method for detecting the deformation state of a grating by establishing a structural deformation field, thereby achieving environmental monitoring. However, this method is relatively complex and computationally inefficient. Furthermore, the method for establishing the deformation field is an interpolation method, which is a numerical method. Its accuracy depends on the number of iterations, increasing computational complexity and reducing computational efficiency. In addition, the numerical solution itself has limitations in accuracy. Summary of the Invention

[0010] To address the shortcomings of existing technologies, according to embodiments of the present invention, a temperature detection system and method for rockets are provided, which solves the problems of limited detection range, large space occupation, and complex temperature information demodulation methods of existing temperature sensors for launch vehicles.

[0011] In one embodiment, a temperature detection system for a rocket is proposed, the temperature detection system comprising: a light source, an isolator, a coupler, a photodetector, a control unit, and a fiber optic grating network;

[0012] The light source is connected to the first end of the coupler via an isolator, the second end of the coupler is connected to the grating network, the third end of the coupler is connected to the photodetector, and the photodetector is connected to the integrated control unit.

[0013] The fiber Bragg grating network consists of several fiber Bragg gratings and runs through the entire rocket body;

[0014] The photodetector is used to detect the reflection spectrum of the reflected light obtained after reflection from the fiber grating network;

[0015] The integrated control unit is used to process the reflection spectrum according to the reconstruction algorithm to obtain the reconstructed fiber grating structure, and then compare it with the original fiber grating structure to obtain the temperature change value and temperature change location of the fiber gratings that have undergone temperature changes in the fiber grating network.

[0016] In one embodiment, the light source is a broadband light source;

[0017] The fiber grating is a cascaded fiber grating with different center wavelengths. The fiber grating is a fiber grating within the measurement range and a regular optical fiber outside the measurement range.

[0018] In one embodiment, the fiber Bragg grating is fixed to each section of the rocket by a reinforcement device, and each fiber Bragg grating is interconnected with each other at the disassembly points of the rocket body via connectors.

[0019] In one embodiment, the isolator is used to form unidirectional isolation between the light source and the coupler, reducing the adverse effects of reflected light or signals on the light source.

[0020] In one embodiment, the detection system further includes a data processing module connected to the integrated control unit and the photodetector respectively, the data processing module being used to perform noise reduction processing on the reflectance spectrum obtained by the photodetector.

[0021] In one embodiment, the data processing module includes an amplifier circuit, a filter circuit, a waveform shaping circuit, a data acquisition circuit, and a data processing circuit.

[0022] Secondly, in one embodiment, a temperature detection method based on the temperature detection system described in any one of the above embodiments is proposed, the temperature detection method comprising:

[0023] S1: Install the fiber optic grating network of the temperature detection system in each section of the rocket body;

[0024] S2: Incident light emitted from the light source passes through an isolator and a coupler to reach a fiber optic grating. The fiber optic grating is affected by temperature changes, causing a change in its refractive index, which in turn alters the characteristics of the reflected light.

[0025] S3: The photodetector detects the reflection spectrum of the reflected light obtained after reflection by the fiber optic grating;

[0026] S4: The integrated control unit processes the reflection spectrum and obtains the temperature change value and location of the fiber grating in the fiber grating network that has undergone temperature change through the reconstruction algorithm.

[0027] In one embodiment, step S4 includes:

[0028] S41: Using a reconstruction algorithm, the parameters of the fiber grating structure are reconstructed based on the reflection spectrum;

[0029] S42: Determine the fiber Bragg grating reconstruction structure based on the parameters of the fiber Bragg grating structure;

[0030] S43: Compare the reconstructed fiber Bragg grating structure with the original fiber Bragg grating structure to determine the temperature change value and location of the temperature change.

[0031] In one embodiment, the fiber grating structure is a refractive index perturbation of the fiber grating, and the parameters of the fiber grating structure include the period, length, and amplitude of the refractive index perturbation.

[0032] In one embodiment, the method further includes the following steps prior to step S4:

[0033] The data processing module performs noise reduction on the reflectance spectrum.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. The fiber optic grating network of the temperature sensing system runs through the entire rocket body, covering the entire rocket compartment, enabling temperature detection of the entire rocket and solving the problem of limited detection range of traditional temperature sensors;

[0036] 2. Fiber Bragg gratings in fiber Bragg grating networks are smaller, more scalable, and better able to adapt to the complex spatial structure inside rocket bodies compared to traditional temperature detection devices, solving the problem of difficult installation of traditional temperature detection devices inside rockets.

[0037] 3. This invention utilizes the inherent structural characteristics of fiber gratings to obtain the reconstructed structure of the fiber grating through a reconstruction algorithm. This reconstructed structure is then compared with the original structure of the fiber grating to determine the location and temperature change value of the fiber grating in the fiber grating network affected by temperature. This detection method is in the form of an analytical solution, eliminating the need for numerical iteration and greatly improving computational efficiency. It also solves the problem of complex temperature information demodulation methods in traditional algorithms. Attached Figure Description

[0038] Figure 1 This is an overall structural diagram of the temperature detection system according to an embodiment of the present invention.

[0039] Figure 2 This is a structural diagram of the temperature detection system according to an embodiment of the present invention.

[0040] Figure 3 This is an overall flowchart of the temperature detection method according to an embodiment of the present invention.

[0041] Figure 4 This is a flowchart illustrating the specific process of obtaining the location and value of temperature change in the temperature detection method according to an embodiment of the present invention. Detailed Implementation

[0042] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] Firstly, in one embodiment, such as Figure 1 and Figure 2 As shown, a temperature detection system for a rocket is proposed, which includes: a light source, an isolator, a coupler, a photodetector, a control unit, and a fiber optic grating network;

[0044] The light source is connected to the first end of the coupler via an isolator, the second end of the coupler is connected to the grating network, the third end of the coupler is connected to the photodetector, and the photodetector is connected to the integrated control unit.

[0045] The fiber Bragg grating network consists of several fiber Bragg gratings and runs through the entire rocket body;

[0046] The photodetector is used to detect the reflection spectrum of the reflected light obtained after reflection from the fiber grating network;

[0047] The integrated control unit is used to process the reflection spectrum according to the reconstruction algorithm to obtain the reconstructed fiber grating structure, and then compare it with the original fiber grating structure to obtain the temperature change value and temperature change location of the fiber gratings that have undergone temperature changes in the fiber grating network.

[0048] In the above embodiments, the fiber Bragg grating network is used to detect the temperature of the rocket body. Compared with other temperature detection sensors, the wavelength modulation characteristics of the fiber Bragg grating can eliminate interference caused by various light intensity fluctuations. Therefore, the temperature detection system composed of fiber Bragg gratings has higher reliability and stability. In addition, the self-reference characteristics of the grating fiber make it possible to use it for absolute measurement of temperature and the location of temperature changes.

[0049] The fiber optic grating network of the temperature sensing system runs through the entire rocket body, covering the entire rocket compartment, enabling temperature detection of the entire rocket and solving the problem of limited detection range of traditional temperature sensors.

[0050] The fiber Bragg gratings in the fiber Bragg grating network are smaller, more scalable, and better able to adapt to the complex spatial structure inside the rocket body compared to traditional temperature detection devices, solving the problem of difficult installation of traditional temperature detection devices inside the rocket.

[0051] By utilizing the inherent structural characteristics of fiber Bragg gratings (FBGs), the reconstructed FBG structure obtained through a reconstruction algorithm is compared with the original FBG structure to determine the location and temperature change value of FBGs affected by temperature changes within the FBG network. This detection method is in the form of an analytical solution, eliminating the need for numerical iteration and significantly improving computational efficiency. It also solves the problem of complex temperature information demodulation methods in traditional algorithms.

[0052] In one embodiment, the light source is a broadband light source;

[0053] The fiber grating is a cascaded fiber grating with different center wavelengths. The fiber grating is a fiber grating within the measurement range and a regular optical fiber outside the measurement range.

[0054] In the above embodiments, broadband light sources are a commonly used light source in fiber optic grating sensor networks. A broadband light source is a thermal light source with a spectral width greater than 30nm, including light-emitting diodes, superluminescent light-emitting diodes, and amplified spontaneous emission light sources.

[0055] In most optical detection systems, optical signals are converted into electrical signals by photodetectors for further processing. At the same time, the noise of the light source is also converted into electrical noise by photodetectors. Broadband light sources have two basic noise characteristics: first, the greater the light intensity of the light source, the greater the noise signal of the light source; second, the noise level of the light source is inversely proportional to the spectral width of the light source, that is, the smaller the spectral width of the light source, the greater the noise of the light source. In wavelength division multiplexing, the second characteristic is particularly important.

[0056] Multiple cascaded fiber Bragg gratings with different center wavelengths are written into the same fiber, which can distinguish different temperature measurement points and is more flexible than the integrated design of ordinary fiber Bragg gratings.

[0057] In one embodiment, the fiber Bragg grating is fixed to each section of the rocket by a reinforcement device, and each fiber Bragg grating is interconnected with each other at the disassembly points of the rocket body via connectors.

[0058] In one embodiment, the isolator is used to form unidirectional isolation between the light source and the coupler, reducing the adverse effects of reflected light or signals on the light source.

[0059] In one embodiment, the detection system further includes a data processing module connected to the integrated control unit and the photodetector respectively, the data processing module being used to perform noise reduction processing on the reflectance spectrum obtained by the photodetector.

[0060] In one embodiment, the data processing module includes an amplifier circuit, a filter circuit, a waveform shaping circuit, a data acquisition circuit, and a data processing circuit.

[0061] Secondly, in one embodiment, such as Figure 3 As shown, a temperature detection method based on any one of the temperature detection systems described in the above embodiments is proposed, the temperature detection method comprising:

[0062] S1: Install the fiber optic grating network of the temperature detection system in each section of the rocket body;

[0063] S2: Incident light emitted from the light source passes through an isolator and a coupler to reach a fiber optic grating. The fiber optic grating is affected by temperature changes, causing a change in its refractive index, which in turn alters the characteristics of the reflected light.

[0064] S3: The photodetector detects the reflection spectrum of the reflected light obtained after reflection by the fiber optic grating;

[0065] S4: The integrated control unit processes the reflection spectrum and obtains the temperature change value and location of the fiber grating in the fiber grating network that has undergone temperature change through the reconstruction algorithm.

[0066] In one embodiment, such as Figure 4 As shown, step S4 includes:

[0067] S41: Using a reconstruction algorithm, the parameters of the fiber grating structure are reconstructed based on the reflection spectrum;

[0068] The fiber grating structure is a refractive index perturbation of the fiber grating, and the parameters of the fiber grating structure include the period, length and amplitude of the refractive index perturbation.

[0069] According to coupled-mode theory, the reflection spectrum of a fiber optic grating is:

[0070]

[0071] The effective refractive index of a fiber Bragg grating is determined by its length, amplitude, and period. κ represents the transverse coupling coefficient.

[0072] Based on the characteristics of the reflection spectrum, the period with refractive index can be obtained as follows:

[0073]

[0074] Where n m and n s These are the cladding refractive index and the core refractive index of the fiber grating;

[0075] The effective refractive index amplitude is:

[0076]

[0077] The length of the effective refractive index is:

[0078]

[0079] Equation (4)

[0080] S42: Determine the fiber Bragg grating reconstruction structure based on the parameters of the fiber Bragg grating structure;

[0081] Before reconstruction, the fiber Bragg gratings in the fiber Bragg grating network are segmented into i1, i2, i3...in segments. The refractive index perturbation of each fiber Bragg grating segment can be expressed as Δn. i1 (z), the structural parameters of the refractive index perturbation are expressed as Λ i1 L i1 ,δn 0i1 Its reflection spectrum can be expressed as R i ;

[0082] Based on equations (1), (2), and (3), the reconstructed structural parameters are obtained as follows: Λ i2 L i2 ,δn 0i2Since the refractive index perturbation Δn(z) is determined by Λ, L, and δn0, the refractive index perturbation Δn after reconstruction of each fiber grating segment can be obtained. i2 (z) is equation (5):

[0083]

[0084] S43: Compare the reconstructed fiber Bragg grating structure with the original fiber Bragg grating structure to determine the temperature change value and location of the temperature change.

[0085] The original structure of the grating fiber is known, as shown in equation (6):

[0086]

[0087] Where δn0 is the amplitude of the refractive index perturbation; b is the fringe visibility; q(z) is the slowly varying envelope of the refractive index perturbation, often referred to as the apodization function; Λ is the period. This is the phase shift point.

[0088] The center wavelength of the fiber optic grating is:

[0089] λ0=Λ(n m +n s +2δ0) Equation (7)

[0090] When subjected to a temperature change ΔT, the change in center wavelength Δλ0 satisfies

[0091] Δλ0=λ0(α+σ)ΔT Equation (8)

[0092] Where α represents the thermo-optic coefficient of the fiber grating, and σ represents the thermal expansion coefficient of the fiber grating.

[0093] Δn in equation (5) i2 (z) and Δn in equation (6) i1 Subtracting z from z gives Δ(z). For Δ(z), the non-zero values ​​at z points represent temperature changes, which can be used to determine the location of the temperature change.

[0094] In one embodiment, the method further includes the following steps prior to step S4:

[0095] The data processing module performs noise reduction on the reflectance spectrum.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A temperature detection system for a rocket, characterized by, The detection system comprises a light source, an isolator, a coupler, a photodetector, a control machine and a fiber grating network. The light source is connected to the first end of the coupler through an isolator, the second end of the coupler is connected to the grating network, the third end of the coupler is connected to the photodetector, and the photodetector is connected to the control machine. The fiber grating network is composed of a plurality of fiber gratings, and the fiber grating network penetrates through the entire rocket body. The photodetector is used to detect the reflection spectrum of the reflected light reflected by the fiber grating network. The control machine is used to process the reflection spectrum according to a reconstruction algorithm to obtain a fiber grating reconstruction structure, and then compare the fiber grating reconstruction structure with an original fiber grating structure to obtain a temperature change value and a temperature change position of the fiber grating in the fiber grating network that has undergone temperature change. The fiber grating structure is a refractive index perturbation of the fiber grating, and the parameters of the fiber grating structure include the period, length and amplitude of the refractive index perturbation. The reflection spectrum of the fiber grating is as follows: Formula (1) wherein is the transverse coupling coefficient; The effective refractive index of the fiber grating is determined by the length, amplitude and period; through the characteristics of the reflection spectrum, the period of the effective refractive index is obtained as follows: Formula (2) wherein and ncl and nc are the cladding and core refractive indices of the fiber grating. The amplitude of the effective refractive index is as follows: Formula (3) The length of the effective refractive index is as follows: Formula (4) The fiber grating network is segmented before reconstruction, sequentially i1, i2, i3…in, the refractive index perturbation of each segment of fiber grating can be expressed as Δ n i1 (z), the structural parameters of refractive index perturbation are expressed as period Λ i1 , length L i1 , amplitude δn 0i1 , and its reflection spectrum can be expressed as R i ; according to formula (1), (2), (3), (4), the structural parameters after reconstruction are respectively period Λ i2 , length L i2 , amplitude δn 0i2 ; the reconstructed refractive index perturbation Δ of each fiber grating n i2 (z) is of formula (5): Formula (5) The original structure of the grating fiber is a known quantity, as shown in formula (6): Equation (6) wherein is the amplitude of the refractive index perturbation; b is the fringe visibility; q z is the slowly varying envelope of the refractive index perturbation, often also referred to as an apodization or apodization function; Λ i1 Λ i2 are the periods of the fiber Bragg grating before and after reconstruction, respectively; is the phase shift point;​ Δ in equation (5) n i2 (z) and Δ in equation (6) n i1 Subtracting (z) gives Δ(z). For Δ(z), the non-zero values ​​at z points represent temperature changes, thus determining the location of the temperature change. The center wavelength of the fiber grating is: wherein is a change in temperature, represents a change in center wavelength, represents a thermo-optic coefficient of the fiber grating, represents a thermal expansion coefficient of the fiber grating.

2. The temperature detection system of the rocket according to claim 1, characterized in that: The light source is a wide-spectrum light source; The fiber gratings are cascaded fiber gratings with different center wavelengths, and the fiber gratings are fiber gratings in the measurement range and ordinary optical fibers in the non-measurement range.

3. The temperature detection system of the rocket according to claim 1, characterized in that: The fiber gratings are fixed on each cabin section of the rocket through a reinforcing device, and each fiber grating is connected to each other through a plug-in piece at the decomposition of the rocket body.

4. The temperature detection system of the rocket according to claim 1, characterized in that: The isolator is used to form one-way isolation between the light source and the coupler, and reduce the adverse effects of the reflected light or signal on the light source.

5. A temperature sensing system for a rocket as defined in claim 1, wherein The detection system further comprises a data processing module connected to the control machine and the photodetector, respectively, and the data processing module is used to perform denoising processing on the reflection spectrum obtained by the photodetector.

6. A temperature sensing system for a rocket as claimed in claim 5 wherein, The data processing module comprises an amplification circuit, a filter circuit, a waveform shaping circuit, a data acquisition circuit and a data processing circuit.

7. A temperature detection method based on the temperature detection system of the rocket according to claim 1, characterized by, The detection method comprises: S1: installing the fiber grating network of the temperature detection system in each cabin section of the rocket body; S2: emitting incident light from the light source, passing through the isolator and the coupler to reach the fiber grating, and changing the refractive index of the fiber grating due to temperature change, thereby changing the characteristics of the reflected light; S3: detecting the reflection spectrum of the reflected light reflected by the fiber grating by the photodetector; S4: processing the reflection spectrum by the control machine to obtain the temperature change value and the temperature change position of the fiber grating in the fiber grating network that has undergone temperature change through a reconstruction algorithm, and the step S4 comprises: S41: using a reconstruction algorithm, reconstructing the parameters of the fiber grating structure according to the reflection spectrum; The fiber grating structure is a refractive index perturbation of the fiber grating, and the parameters of the fiber grating structure include the period, length and amplitude of the refractive index perturbation; The reflection spectrum of the fiber grating is: Formula (1) The effective refractive index of the fiber grating is determined by length, amplitude and period; wherein is a transverse coupling coefficient; Through the characteristics of the reflection spectrum, the period of the effective refractive index is obtained: Formula (2) wherein and ncl and nc are the cladding and core refractive indices of the fiber grating. The amplitude of the effective refractive index is: Formula (3) The length of the effective refractive index is: Formula (4) S42: determining the fiber grating reconstruction structure according to the parameters of the fiber grating structure; The fiber grating network is segmented before reconstruction, sequentially i1, i2, i3…in, the refractive index perturbation of each segment of fiber grating can be expressed as Δ n i1 (z), the structural parameters of refractive index perturbation are expressed as period Λ i1 , length L i1 , amplitude δn 0i1 , and the reflection spectrum can be expressed as R i ; According to formula (1), (2), (3), (4), the reconstructed structure parameters are respectively period Λ i2 , length L i2 , amplitude δn 0i2 ; since the refractive index perturbation Δ n (z) is determined by Λ, L , δn 0, the reconstructed refractive index perturbation Δ n i2 (z) of each fiber grating is obtained as formula (5): Formula (5) S43: comparing the fiber grating reconstruction structure and the fiber grating original structure to determine the temperature change value and the temperature change position of the fiber grating; The grating fiber original structure is a known quantity, as shown in formula (6): Formula (6) wherein is the amplitude of the refractive index perturbation; b is the fringe visibility; q ( z ) is a slowly varying envelope of the refractive index perturbation, often also referred to as an apodization or apodization function; Λ i1 , Λ i2 are the periods of the fiber Bragg grating before and after reconstruction, respectively; is the phase shift point; Δ in equation (5) n i2 (z) and Δ in equation (6) n i1 Subtracting (z) gives Δ(z). For Δ(z), the non-zero values ​​at z points represent temperature changes, thus determining the location of the temperature change. The center wavelength of the fiber grating is: wherein is a change in temperature, represents a change in center wavelength, represents a thermo-optic coefficient of the fiber grating, represents a thermal expansion coefficient of the fiber grating.

8. The temperature detecting method according to claim 7, wherein The step S4 further includes: The data processing module performs denoising processing on the reflection spectrum.

Images