Distributed fiber bragg grating demodulation device for battery system

Abstract

The invention provides a distributed fiber bragg grating demodulation device for a battery system, which is based on an FBG demodulation scheme of tunable filtering, can realize better compatibility and support for a hybrid multiplexing FBG sensor network, performs targeted optimization for software and hardware architecture of the device, has the advantages of compact overall structure, low power consumption and controllable cost, and is suitable for popularization and application. The high requirements of a new energy automobile power battery and a high-integration-level energy storage system for related indexes can be met, and a practical and feasible solution is provided for safety monitoring and early fault early warning of a battery system. A hybrid multiplexing architecture composed of wavelength division multiplexing and multi-channel multiplexing in the device can realize large-scale and multi-point distributed sensor network deployment under the condition of limited hardware resources, and meet the requirement of multi-source and multi-position information synchronous acquisition in a high-integration battery system, thereby remarkably improving the spatial resolution of battery internal state sensing.

Description

Technical Field

[0001] This invention belongs to the field of battery system sensing and detection technology, and specifically relates to a distributed fiber optic grating demodulation device for battery systems. Background Technology

[0002] Currently, battery management systems (BMS) primarily rely on measuring external electrothermal parameters such as voltage, charging / discharging current, and temperature, combined with built-in models, for monitoring and early warning. However, these external parameter-based methods are insufficient to fully reflect the multi-scale, multi-dimensional state evolution characteristics of battery failure processes, including macroscopic physical changes such as casing bulging, structural deformation, and electrolyte leakage, as well as microscopic and complex internal electrochemical processes such as lithium dendrite growth, micro-short circuits, and SEI film decomposition. This limits the accuracy and timeliness of battery safety early warnings. Existing technologies that incorporate fiber Bragg grating (FBG) sensors in battery systems offer advantages in multi-parameter monitoring and signal multiplexing, improving large-scale safety early warning capabilities, due to their high sensitivity, electrical insulation, electromagnetic interference resistance, corrosion resistance, and high-temperature and high-pressure resistance. However, significant room for improvement remains in system integration, accuracy, and reliability of battery state sensing. Summary of the Invention

[0003] In view of this, and in response to the technical problems existing in this field, the present invention provides a distributed fiber Bragg grating demodulation device for battery systems, which consists of a distributed fiber Bragg grating (FBG) sensor network, a broadband light source, a tunable filter, an optical circulator, a photodetector, a voltage driving module, a signal amplification circuit, and a microcontroller.

[0004] In this system, a broadband light source emits light in a preset frequency band, which is then fed to a tunable filter. The tunable filter, based on a driving voltage provided by a voltage-driven module, modulates the light and outputs narrowband scanning light corresponding to the center wavelength. This narrowband scanning light then enters an optical circulator. The circulator is connected to an optical fiber in an FBG (Fast-Fast Generation) sensor network via n optical switches, each fiber employing the same structure, thus forming n optical channels. The narrowband scanning light is transmitted from the circulator to the FBG sensor network, reflected back through the FBG sensor network, and then transmitted from the circulator to a photodetector. The photodetector converts the reflected light power into a current signal. The signal is amplified by the signal amplification circuit and then sampled and detected by the microcontroller using an ADC. Based on the detected signal peak value, a peak demodulation algorithm is executed to solve for the corresponding driving voltage peak value based on Gaussian fitting. When the Gaussian fitting result is unstable, the weighted centroid method is used to calculate the driving voltage peak value. Finally, the corresponding center wavelength is deduced from the driving voltage. During the peak demodulation process, m FBGs are arranged on each optical fiber in n optical channels, and m light rays with different center wavelengths are transmitted using wavelength division multiplexing, thereby forming an n×m multiplexed FBG sensing network to realize online monitoring and early warning of the internal status of the battery system at the single-cell level.

[0005] Furthermore, the broadband light source specifically selects ASE or SLD broadband light sources, with a wavelength range covering the C+L band (1510nm~1590nm); the tunable filter specifically adopts a grating tunable filter or a Fabry-Perot tunable filter, and the tuning of the transmission center wavelength of the filter is realized through voltage-driven microelectromechanical systems (MEMS) technology; the photodetector adopts a high-speed photodiode PD; the voltage drive module adopts a high-precision DAC chip; the signal amplification circuit specifically adopts a multi-stage amplification circuit composed of a transimpedance amplifier circuit and an operational amplifier circuit; the microcontroller adopts a single-chip microcomputer or DSP, which can be used to control the voltage drive module, acquire the output signal of the signal amplification circuit, run the peak demodulation algorithm, store information, and communicate with the host computer.

[0006] Furthermore, the specific process for peak demodulation of a single FBG includes:

[0007] First, the discrete data (U) obtained by ADC sampling is processed. drive,i U PD,i Preprocessing is performed to ensure the stability of subsequent calculations; where U drive,i with U PD,i The driving voltage and photodetector signal are at i sampling times;

[0008] Then perform the following Gaussian fitting:

[0009] Assuming driving voltage U drive The corresponding photodetector signal U PDIt approximately follows a Gaussian distribution near the peak, and its mathematical expression is:

[0010]

[0011] Where A is the peak amplitude, μ is the peak position, and σ is the distribution width;

[0012] Taking the natural logarithm of both sides of the above equation yields the following linearized form:

[0013]

[0014] in,

[0015]

[0016] The coefficients a, b, and c are solved using the least squares method. Assuming the number of sampling points is N, the following system of equations is constructed:

[0017]

[0018] By constructing and solving the normal equations in the least squares method, the corresponding coefficients are calculated:

[0019]

[0020] Using the least squares method to apply ln(U) PD ) and U drive The quadratic relationship is fitted to obtain coefficients a, b, and c, thereby calculating the peak value U of the photodetector signal. PD,peak Corresponding tunable filter drive voltage U drive,peak :

[0021]

[0022] The stability of the Gaussian fitting process is determined based on matrix M. When the determinant of matrix M is too small (1×10⁻⁶), the stability is determined by... -8 At this point, the weighted centroid algorithm is used to calculate the driving voltage U. drive,peak The specific calculation formula is as follows:

[0023]

[0024] After obtaining the driving voltage U drive,peak Then, based on its correspondence with the center wavelength, the corresponding center wavelength can be obtained, and finally FBG demodulation is completed.

[0025] Furthermore, in wavelength division multiplexing mode, the following additional peak tracking and matching are performed on a single fiber:

[0026] For photodetector signal U PDPerform real-time monitoring and match the set threshold U PD,th When comparing, if three consecutive sample values ​​are all greater than U PD,th At that time, the U-wavelength of the optical fiber was recorded. PD Value and corresponding driving voltage U drive ; when U PD Less than U PD,th Recording stops when the specified time is reached; data recorded within that interval (U) drive,i U PD,i And input it into the peak demodulation algorithm to obtain the center wavelength of the k-th FBG in the optical fiber; when U PD Surpassing U again PD,th At that time, demodulation of the (k+1)th FBG begins.

[0027] The distributed fiber Bragg grating demodulation device for battery systems provided by the present invention, based on a tunable filter FBG demodulation scheme, achieves good compatibility and support for hybrid multiplexed FBG sensor networks. Targeted optimizations have been made to the device's hardware and software architecture, resulting in a compact overall structure, low power consumption, and controllable cost. It meets the high requirements of new energy vehicle power batteries and highly integrated energy storage systems for relevant indicators, providing a practical solution for battery system safety monitoring and early fault warning. The hybrid multiplexing architecture, composed of wavelength division multiplexing and multi-channel multiplexing, enables large-scale, multi-point distributed sensor network deployment under limited hardware resources, meeting the needs of synchronous acquisition of multi-source, multi-location information in highly integrated battery systems, thereby significantly improving the spatial resolution of battery internal state perception. Attached Figure Description

[0028] Figure 1 This is a general framework diagram of the distributed fiber Bragg grating demodulation device for battery systems provided by the present invention.

[0029] Figure 2 This is an optional structural diagram of the voltage drive module;

[0030] Figure 3 This is a schematic diagram of an optional structure for a signal amplification circuit.

[0031] Figure 4 This is a diagram illustrating the wavelength division multiplexing (WDM) scheme of an FBG sensor network.

[0032] Figure 5 Here is a flowchart of the peak demodulation algorithm;

[0033] Figure 6 This is a schematic diagram of the demodulation process in wavelength division multiplexing mode. Detailed Implementation

[0034] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0035] The distributed fiber Bragg grating demodulation device for battery systems provided by this invention, such as... Figure 1 As shown, it consists of a distributed fiber Bragg grating (FBG) sensor network, a broadband light source, a tunable filter, an optical circulator, a photodetector, a voltage drive module, a signal amplification circuit, and a microcontroller.

[0036] In this process, a broadband light source emits light in a preset frequency band, which is then fed to a tunable filter. The tunable filter modulates the light based on the driving voltage provided by the voltage-driven module and outputs narrowband scanning light corresponding to the center wavelength. This narrowband scanning light then enters an optical circulator. The circulator is connected to an optical fiber in an FBG sensing network via n optical switches, each fiber employing the same structure, thus forming n optical channels. The narrowband scanning light is transmitted from the circulator to the FBG sensing network, reflected back to the circulator, and then transmitted to a photodetector. The photodetector converts the reflected light power into a current signal, which is amplified by a signal amplifier circuit and then sampled and detected by an ADC by a microcontroller. Based on the detected signal peak value, a peak demodulation algorithm is executed. The corresponding driving voltage peak value is calculated based on Gaussian fitting, and if the Gaussian fitting result is unstable, a weighted centroid method is used to calculate the driving voltage peak value. Finally, the corresponding center wavelength is deduced from the driving voltage. During peak demodulation, m FBGs are arranged on each optical fiber in the n optical channels, using a method such as... Figure 4 The wavelength division multiplexing method shown transmits m light rays with different center wavelengths, thereby forming an n×m multiplexed FBG sensor network to realize online monitoring and early warning of the internal status of the battery system at the single-cell level.

[0037] In a preferred embodiment of the present invention, the broadband light source is specifically selected from ASE or SLD broadband light sources, with a wavelength range covering the C+L band (1510nm~1590nm); the tunable filter specifically adopts a grating tunable filter or a Fabry-Perot tunable filter, and the tuning of the filter's transmission center wavelength is achieved through voltage-driven microelectromechanical systems (MEMS) technology; the photodetector adopts a high-speed photodiode PD; the voltage driving module adopts... Figure 2 The high-precision DAC chip shown; the signal amplification circuit specifically adopts a transimpedance amplifier circuit and an operational amplifier circuit as follows. Figure 3The multi-stage amplifier circuit shown is used; the microcontroller is a single-chip microcomputer or DSP, which can be used to control the voltage drive module, acquire the output signal of the signal amplification circuit, run the peak demodulation algorithm, store information, and communicate with the host computer.

[0038] In a preferred embodiment of the present invention, such as Figure 5 As shown, the specific process of peak demodulation for a single FBG includes:

[0039] First, the discrete data (U) obtained by ADC sampling is processed. drive,i U PD,i Preprocessing is performed to ensure the stability of subsequent calculations; where U drive,i with U PD,i The driving voltage and photodetector signal are at i sampling times;

[0040] Then perform the following Gaussian fitting:

[0041] Assuming driving voltage U drive The corresponding photodetector signal U PD It approximately follows a Gaussian distribution near the peak, and its mathematical expression is:

[0042]

[0043] Where A is the peak amplitude, μ is the peak position, and σ is the distribution width;

[0044] Taking the natural logarithm of both sides of the above equation yields the following linearized form:

[0045]

[0046] in,

[0047]

[0048] The coefficients a, b, and c are solved using the least squares method. Assuming the number of sampling points is N, the following system of equations is constructed:

[0049]

[0050] By constructing and solving the normal equations in the least squares method, the corresponding coefficients are calculated:

[0051]

[0052] Using the least squares method to apply ln(U) PD ) and U drive The quadratic relationship is fitted to obtain coefficients a, b, and c, thereby calculating the peak value U of the photodetector signal. PD,peak Corresponding tunable filter drive voltage U drive,peak:

[0053]

[0054] The stability of the Gaussian fitting process is determined based on matrix M. When the determinant of matrix M is too small (1×10⁻⁶), the stability is determined by... -8 At this point, the weighted centroid algorithm is used to calculate the driving voltage U. drive,peak The specific calculation formula is as follows:

[0055]

[0056] After obtaining the driving voltage U drive,peak Then, based on its correspondence with the center wavelength, the corresponding center wavelength can be obtained, and finally FBG demodulation is completed.

[0057] In a preferred embodiment of the present invention, such as Figure 6 As shown, in wavelength division multiplexing mode, the following additional peak tracking and matching are performed for a single fiber:

[0058] For photodetector signal U PD Perform real-time monitoring and match the set threshold U PD,th When comparing, if three consecutive sample values ​​are all greater than U PD,th At that time, the U-wavelength of the optical fiber was recorded. PD Value and corresponding driving voltage U drive ; when U PD Less than U PD,th Recording stops when the specified time is reached; data recorded within that interval (U) drive,i U PD,i And input it into the peak demodulation algorithm to obtain the center wavelength of the k-th FBG in the optical fiber; when U PD Surpassing U again PD,th At that time, demodulation of the (k+1)th FBG begins.

[0059] It should be understood that the sequence number of each step in the embodiments of the present invention does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0060] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A distributed fiber Bragg grating demodulation device for battery systems, characterized in that: It consists of a distributed FBG sensor network, a broadband light source, a tunable filter, an optical circulator, a photodetector, a voltage drive module, a signal amplification circuit, and a microcontroller. In this system, a broadband light source emits light in a preset frequency band, which is then fed to a tunable filter. The tunable filter, based on a driving voltage provided by a voltage-driven module, modulates the light and outputs narrowband scanning light corresponding to the center wavelength. This narrowband scanning light then enters an optical circulator. The circulator is connected to one optical fiber in a distributed FBG sensor network via n optical switches, each fiber employing the same structure, thus forming n optical channels. The narrowband scanning light is transmitted from the circulator to the distributed FBG sensor network, reflected back to the circulator, and then transmitted to a photodetector. The photodetector converts the reflected light power... The signal is converted to a current signal, amplified by a signal amplification circuit, and then sampled and detected by an ADC by a microcontroller. Based on the detected signal peak value, a peak demodulation algorithm is executed to solve for the corresponding driving voltage peak value based on Gaussian fitting. When the Gaussian fitting result is unstable, the weighted centroid method is used to calculate the driving voltage peak value. Finally, the corresponding center wavelength is deduced from the driving voltage. During the peak demodulation process, m FBGs are arranged on each optical fiber in n optical channels, and m light rays with different center wavelengths are transmitted using wavelength division multiplexing, thereby forming an n×m multiplexed FBG sensing network to realize online monitoring and early warning of the internal status of the battery system at the single-cell level.

2. The distributed fiber Bragg grating demodulation device for battery systems as described in claim 1, characterized in that: The broadband light source is specifically selected from ASE or SLD broadband light sources, with a wavelength range covering the C+L band; the tunable filter is specifically a grating tunable filter or a Fabry-Perot tunable filter, and the center wavelength of the filter transmission is tuned through MEMS technology; the photodetector is a high-speed photodiode PD; the voltage drive module is a high-precision DAC chip; the signal amplification circuit is specifically a multi-stage amplification circuit composed of a transimpedance amplifier circuit and an operational amplifier circuit; the microcontroller is a single-chip microcomputer or DSP.

3. The distributed fiber Bragg grating demodulation device for battery systems as described in claim 1, characterized in that: The specific process for peak demodulation of a single FBG includes: First, the discrete data (U drive,i , U PD,i ) obtained by ADC sampling is preprocessed to ensure the stability of subsequent calculation; wherein U drive,i and U PD,i are driving voltage and photodetector signal at i sampling moments; Then perform the following Gaussian fitting: Assuming a driving voltage U drive The corresponding photodetector signal U PD Near the peak, the distribution is approximately Gaussian, with the mathematical expression: Where A is the peak amplitude, μ is the peak position, and σ is the distribution width; Taking the natural logarithm of both sides of the above equation yields the following linearized form: in, The coefficients a, b, and c are solved using the least squares method. Assuming the number of sampling points is N, the following system of equations is constructed: By constructing and solving the normal equations in the least squares method, the corresponding coefficients are calculated: The quadratic relationship of ln(U PD ) and U drive is fitted by the least square method, i.e. the coefficients a, b, c are obtained, so that the peak value U PD,peak of the photoelectric detector signal corresponding to the driving voltage U drive,peak of the tunable filter is calculated. Based on the matrix M, it is determined whether the Gaussian fitting process is stable, and when the determinant of the matrix M is too small, a weighted centroid algorithm is used to calculate the driving voltage U drive,peak The specific calculation formula is as follows: After obtaining the driving voltage U drive,peak Then, based on its correspondence with the center wavelength, the corresponding center wavelength can be obtained, and finally FBG demodulation is completed.

4. The distributed fiber Bragg grating demodulation device for battery systems as described in claim 1, characterized in that: In wavelength division multiplexing mode, the following additional peak tracking and matching are performed on a single fiber: For photodetector signal U PD Perform real-time monitoring and match the set threshold U PD,th When comparing, if three consecutive sample values ​​are all greater than U PD,th At that time, the U-wavelength of the optical fiber was recorded. PD Value and corresponding driving voltage U drive ; when U PD Less than U PD,th Recording stops when the specified time is reached; data recorded within that interval (U) drive,i U PD,i And then incorporate the peak demodulation algorithm to obtain the center wavelength of the k-th FBG in the optical fiber; When U PD Surpassing U again PD,th At that time, demodulation of the (k+1)th FBG begins.

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