Device and method for detecting thermally induced micro strain of energy storage batteries using FP / FBG multiplexing technology

Abstract

The device for detecting thermal microstrain of energy storage battery by using F‑P / FBG multiplexing technology comprises an optical fiber microstrain sensor, wherein the optical fiber connector of the optical fiber microstrain sensor is connected to the optical channel on the optical fiber sensor demodulator; the communication interface end of the optical fiber sensor demodulator is connected to a computer; the manufacturing method of the optical fiber microstrain sensor comprises the following steps: step 1, engraving the optical fiber grating on the tail end of the optical fiber and inserting it into the ceramic pin, and fixing and bonding the two together; step 2, drilling a hole in the center of the cut circular fixing plate with an electric drill, inserting the ceramic pin into the fixing plate with the hole drilled, and fixing and bonding the two together; step 3, fixing the hard piezoelectric ceramic and the fixing plate with the ceramic pin in a metal cylinder, and fixing and bonding them with glue; step 4, welding the lead wire to the hard piezoelectric ceramic to connect the flexible piezoelectric material to complete the manufacturing of the optical fiber microstrain sensor; the device comprises the following steps: step 1, engraving the optical fiber grating on the tail end of the optical fiber and inserting it into the ceramic pin, and fixing and bonding the two together; step 2, drilling a hole in the center of the cut circular fixing plate with an electric drill, inserting the ceramic pin into the fixing plate with the hole drilled, and fixing and bonding the two together; step 3, fixing the hard piezoelectric ceramic and the fixing plate with the ceramic pin in the metal cylinder, and fixing and bonding them with glue; step 4, welding the lead wire to the hard piezoelectric ceramic to connect the flexible piezoelectric material to complete the manufacturing of the optical fiber microstrain sensor; the device comprises the following steps:

Description

Technical Field

[0001] The present invention relates to the field of battery energy storage technology, and specifically to a method and device for detecting thermally induced micro-strain of energy storage batteries using FP / FBG multiplexing technology. Background Art

[0002] With the continuous development of economy, human beings are facing the problems of depletion of non-renewable resources, serious environmental pollution, and climate warming. The research and development of energy storage technology has been paid more and more attention by energy, transportation, power and other departments in various countries. Compared with various energy storage technologies, battery energy storage system is flexible to install and has a short construction period. It is a technology that is more suitable for engineering applications at this stage. Battery container energy storage system has the characteristics of easy installation, small footprint, and flexible mobility. As a new energy storage device, it has been widely valued by more and more people.

[0003] At present, the key technology restricting the development of energy storage systems lies in power batteries, and battery thermal strain is a key factor in evaluating battery performance, safety, and life. Most batteries will generate heat during use. Long-term overheating of the battery will cause the battery to swell. When the expansion reaches a certain degree, the battery needs to be cooled. Therefore, it is necessary to accurately measure the micro-deformation caused by battery heating. Most existing technologies for measuring micro-strains use fiber Bragg gratings for measurement, but their measurement accuracy is easily affected by temperature and cannot be accurately measured when the battery is hot. The intrinsic fiber Fabry-Perot structure has the advantages of high measurement accuracy, simple structure, strong anti-interference ability, fast response speed, and small size, and has attracted people's attention. Summary of the invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the object of the present invention is to provide a device and method for detecting thermally induced microstrain of energy storage batteries using FP / FBG multiplexing technology, which can accurately and effectively measure the temperature and strain of the energy storage battery; it has the advantages of high measurement accuracy, simple structure, strong anti-interference ability, fast response speed and small size.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] The device for detecting thermally induced microstrain of energy storage batteries by using FP / FBG multiplexing technology comprises an optical fiber microstrain sensor, an optical fiber sensor demodulator, and a computer. The optical fiber connector of the optical fiber microstrain sensor is connected to an optical channel on the optical fiber sensor demodulator; and the communication interface end of the optical fiber sensor demodulator is connected to the computer.

[0007] The optical fiber tail end of the optical fiber micro-strain sensor is engraved with a fiber grating (FBG).

[0008] The optical fiber micro-strain sensor comprises a metal cylinder, one end of which is provided with a fixing plate; a ceramic pin is inserted into the fixing plate, and an optical fiber is inserted into the ceramic pin; the other end of the inner cavity of the circular sleeve is provided with a hard piezoelectric ceramic, and the hard piezoelectric ceramic lead is externally connected to a flexible piezoelectric material.

[0009] The diameter of the hard piezoelectric ceramic is 16 cm.

[0010] The inner diameter of the circular sleeve is 18 mm, the outer diameter is 20 mm, and the length is 25 mm.

[0011] The ceramic pin end surface and the hard piezoelectric ceramic end surface in the circular sleeve form a Fabry-Perot cavity with air as the medium.

[0012] The initial cavity length of the Fabry-Perot cavity is 0.5 mm to 0.6 mm.

[0013] One end of the hard piezoelectric ceramic is optically processed to form a high-reflection surface.

[0014] The flexible piezoelectric material is a square with a side length of 50 mm.

[0015] The optical fiber sensor demodulator is an optical fiber sensor demodulator suitable for FP and FBG.

[0016] A method for manufacturing an optical fiber micro-strain sensor comprises the following steps:

[0017] Step 1, engrave a fiber Bragg grating (FBG) on the tail end of the optical fiber and insert it into the ceramic pin, and then fix and bond the two with glue;

[0018] Step 2, cut the fixing plate into a circle with the same inner diameter as the metal cylinder, use an electric drill to drill a hole in the center of the cut circular fixing plate (the hole diameter is the same as the specification of the ceramic pin), insert the ceramic pin into the fixing plate with the hole drilled, and fix and bond the two together;

[0019] Step 3, fix the hard piezoelectric ceramic and the fixing plate with the ceramic pin in the metal cylinder, adjust the cavity length formed by the ceramic pin and the hard piezoelectric ceramic end face, and select the best cavity length for the interference signal between 0.5mm and 0.6mm, and finally fix and bond them with glue.

[0020] Step 4, welding leads to the hard piezoelectric ceramics to connect the flexible piezoelectric material to complete the production of the optical fiber micro-strain sensor.

[0021] The beneficial effects of the present invention are:

[0022] The present invention uses FP and FBG sensor multiplexing technology to achieve simultaneous transmission of optical signals of different spectral modes of two parameters, ultrasonic signal and temperature, on the same optical fiber. Fiber multiplexing technology solves the problem of the sensor detecting the strain signal in real time while synchronously detecting the current ambient temperature, comprehensively considers the performance of the battery from multiple parameters, simplifies the structure of the sensor, expands the range of ambient temperature of the sensor, and improves the stability of the sensor.

[0023] The present invention uses two kinds of piezoelectric materials, flexible and rigid, for sensing, respectively utilizing the positive piezoelectric effect and the inverse piezoelectric effect of the piezoelectric material. The flexible piezoelectric material can more accurately measure and feed back the signal to the rigid piezoelectric material for sensing.

[0024] The device of the present invention has the advantages of small size, simple production, high precision, good stability, strong anti-interference ability, etc. It can be widely used in engineering measurement and scientific research fields, and provides a good experimental basis for research in various fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a fiber optic micro strain sensor

[0026] Figure 2 This is an enlarged cross-sectional view of a single-mode optical fiber engraved with a fiber grating.

[0027] Figure 3 Schematic diagram of the system structure of the present invention

[0028] In the figure: 1-optical fiber, 2-ceramic pin, 3-rigid piezoelectric ceramic, 4-metal cylinder, 5-fixed plate, 6-optical fiber grating, 7-flexible piezoelectric material, 8-optical fiber micro strain sensor, 9-optical fiber sensor demodulator, 10-computer. DETAILED DESCRIPTION

[0029] The structural principle and working principle of the present invention are further described in detail below in conjunction with the accompanying drawings and embodiments.

[0030] See also Figure 1-3 The device for detecting thermally induced microstrain of energy storage batteries using FP / FBG multiplexing technology is characterized in that it includes an optical fiber microstrain sensor 8, an optical fiber sensor demodulator 9, and a computer 10. The optical fiber connector of the optical fiber microstrain sensor 8 is connected to the optical channel on the optical fiber sensor demodulator 9; the communication interface end of the optical fiber sensor demodulator 9 is connected to the computer 10.

[0031] The optical fiber tail end of the optical fiber micro-strain sensor is engraved with an optical fiber grating 6 .

[0032] The optical fiber micro-strain sensor comprises a metal cylinder 4, one end of which is provided with a fixing 5; a ceramic pin 2 is plugged into the fixing plate 5, and an optical fiber 1 is plugged into the ceramic pin; a hard piezoelectric ceramic 3 is provided at the other end of the inner cavity of the metal cylinder 4, and the hard piezoelectric ceramic 3 is connected to a flexible piezoelectric material 7 through a lead wire.

[0033] The diameter of the hard piezoelectric ceramic is 16 cm.

[0034] The inner diameter of the metal cylinder 4 is 18 mm, the outer diameter is 20 mm, and the length is 25 mm. The metal cylinder 4 is a circular sleeve.

[0035] The ceramic pin end surface and the hard piezoelectric ceramic end surface in the metal cylinder 4 form a Fabry-Perot cavity with air as the medium; the initial cavity length of the Fabry-Perot cavity is 0.5 mm to 0.6 mm.

[0036] One end of the hard piezoelectric ceramic is optically processed to form a high-reflection surface.

[0037] The flexible piezoelectric material is a square with a side length of 50 mm.

[0038] The optical fiber sensor demodulator is an optical fiber sensor demodulator suitable for FP and FBG.

[0039] The working principle of the present invention is:

[0040] When the battery generates heat, the fiber grating on the fiber optic micro-strain sensor will produce corresponding deformation due to the change in temperature. The signal is demodulated by the fiber optic sensor demodulator to demodulate the optical signal returned by the fiber optic Bragg grating sensor. Through calibration, the temperature measurement can be achieved. When the battery generates micro-strain, the flexible piezoelectric ceramics fixed on the surface of the battery will generate electrical signals through the positive piezoelectric effect and then transmit them to the hard piezoelectric ceramics. The hard piezoelectric ceramics will deform through the inverse piezoelectric effect. The distance between the two reflecting surfaces of the optical probe end face and the upper surface of the hard piezoelectric ceramics changes, resulting in changes in the intensity and interference phase of the light, generating a changing light signal, which is transmitted through the optical fiber and converted into a photoelectric signal by the fiber optic sensor demodulator. The data is processed by a computer to realize the sensor's measurement of the battery's micro-strain.

[0041] See also Figure 1 The optical fiber micro strain sensor 8 comprises a circular sleeve 4, a fixing plate 5 is provided in the inner cavity of the metal cylinder 4; a ceramic pin 2 is plugged into the fixing plate 5, and an optical fiber 1 is plugged into the left end of the ceramic pin 2; an optical fiber grating (FBG) 6 is engraved on the optical fiber 1; a hard piezoelectric ceramic 3 is provided at one end of the metal cylinder 4, and a flexible piezoelectric material 7 is connected to the hard piezoelectric ceramic 3 by a lead wire.

[0042] The method for manufacturing an optical fiber micro strain sensor comprises the following steps:

[0043] Step 1: Select 8 / 125 single-mode optical fiber with FC / APC interface type, strip off the coating layer at the tail end of the optical fiber to expose the core part of the optical fiber, and then cut or polish the end face of the optical fiber;

[0044] Step 2, insert the processed optical fiber into the ceramic pin and fix the two with glue, and cut the fixing sheet into a circle with the same diameter as the hard piezoelectric ceramic;

[0045] Step 3, use an electric drill to drill a hole in the center of the cut circular fixing plate (the hole diameter is the same as the specification of the ceramic pin), insert the ceramic pin into the fixing plate with the drilled hole and fix the two together;

[0046] Step 4. Under the premise of ensuring the parallelism of the hard piezoelectric ceramic and the optical fiber end face, the demodulation system can be used to obtain the interference signal generated by the reflected light of the optical fiber end face and the reflected light of the hard piezoelectric ceramic, fine-tune the distance between the optical fiber end face and the hard piezoelectric ceramic, and select a suitable cavity length range to optimize the quality of the interference signal. Finally, glue is used to bond and fix, and finally the flexible piezoelectric material is connected to the hard piezoelectric ceramic lead to complete the sensor production.

[0047] The tail end of the single-mode optical fiber is engraved with a fiber grating (FBG), and the fiber grating (FBG) is partially encapsulated in the cladding.

[0048] See also Figure 2 , is an enlarged cross-sectional view of a single-mode optical fiber engraved with a fiber Bragg grating according to the present invention. The optical fiber adopts a 9 / 125 single-mode optical fiber, and its interface type is FC / APC. The single-mode optical fiber has a fiber Bragg grating (FBG) engraved on the fiber core at the end.

[0049] Temperature changes will also affect the performance of the battery. Adding a fiber grating module to the fiber micro-strain sensor can detect the current ambient temperature, detect the heat and micro-strain of the energy storage battery, and reflect the performance of the battery.

[0050] When the ambient temperature changes, the wavelength shift of the fiber Bragg grating is Δθ B It will change with the change of ambient temperature, so the wavelength shift of fiber Bragg grating caused by temperature can be expressed as Δλ B =λ B (a th +ξ)·ΔT=K' T ·ΔT; where Δλ B is the wavelength shift of the fiber Bragg grating, λ B is the central wavelength of the fiber Bragg grating, a th =0.55×10 -6 / ℃ is the thermal expansion coefficient, ξ=8.0×10 -6 / ℃ is the thermo-optic coefficient, ΔT is the change in temperature, K' Tis the total temperature sensitivity of the FBG sensor.

[0051] See also Figure 3 , a device for detecting thermally induced micro-strain of energy storage batteries using FP / FBG multiplexing technology, including an optical fiber micro-strain sensor 8, an optical fiber sensor demodulator 9, and a computer 10. The optical fiber micro-strain sensor fixes the flexible piezoelectric material 7 on the surface of the energy storage battery. When the battery generates micro-strain, the flexible piezoelectric ceramic fixed on the surface of the battery generates an electrical signal through the positive piezoelectric effect and then transmits it to the hard piezoelectric ceramic 3. The hard piezoelectric ceramic 3 will deform through the inverse piezoelectric effect, and the distance between the two reflective surfaces of the optical probe end face and the upper surface of the hard piezoelectric ceramic will change, resulting in changes in the intensity and interference phase of the light. The relationship is as follows:

[0052]

[0053] Where: is the phase difference between any two beams of light, R is the reflectivity of the two end surfaces, and n is the refractive index of the medium in the FP cavity, L is the cavity length, λ is the wavelength of the incident light, θ is the angle between the reflected light and the normal of the reflection plane, I 0 is the incident light intensity;

[0054] The changing light signal is transmitted through the optical fiber and converted into the photoelectric signal by the optical fiber sensor demodulator. The data is processed by the computer to realize the sensor's measurement of the strain of the hard piezoelectric ceramic. The potential generated by the flexible piezoelectric material can be obtained through the strain of the hard piezoelectric ceramic, and the strain of the battery can be inferred from the potential of the flexible piezoelectric material. The relationship is as follows:

[0055]

[0056] Where: S is the strain tensor, d 33 is the piezoelectric coefficient, U is the voltage, and D is the material thickness.

Claims

1. A device for detecting thermally induced microstrain of energy storage batteries using FP / FBG multiplexing technology, characterized in that: It comprises an optical fiber micro-strain sensor (8), an optical fiber sensor demodulator (9), and a computer (10); the optical fiber connector of the optical fiber micro-strain sensor (8) is connected to an optical channel on the optical fiber sensor demodulator (9); and the communication interface end of the optical fiber sensor demodulator (9) is connected to the computer (10); The optical fiber tail end of the optical fiber micro-strain sensor is engraved with an optical fiber grating (6); The optical fiber micro-strain sensor comprises a metal cylinder (4), one end of the inner cavity of the metal cylinder (4) is provided with a fixing plate (5); a ceramic pin (2) is plugged into the fixing plate (5), and an optical fiber (1) is plugged into the ceramic pin; the other end of the inner cavity of the metal cylinder (4) is provided with a hard piezoelectric ceramic (3), and the hard piezoelectric ceramic (3) is externally connected to a flexible piezoelectric material (7) through a lead wire; The diameter of the hard piezoelectric ceramic is 16 cm; The inner diameter of the metal cylinder (4) is 18 mm, the outer diameter is 20 mm, and the length is 25 mm. The metal cylinder (4) is a circular sleeve; The ceramic pin end surface and the hard piezoelectric ceramic end surface in the metal cylinder (4) form a Fabry-Perot cavity with air as the medium; the initial cavity length of the Fabry-Perot cavity is 0.5 mm to 0.6 mm; The hard piezoelectric ceramic is optically processed at one end to form a high reflective surface; The flexible piezoelectric material is a square with a side length of 50 mm; The optical fiber sensor demodulator is an optical fiber sensor demodulator suitable for FP and FBG.

2. A method for manufacturing an optical fiber micro strain sensor, characterized in that: The following steps are involved: Step 1, engrave a fiber grating (6) on the tail end of the optical fiber (1) and insert it into the ceramic pin (2), and then fix and bond the two with glue; Step 2, cut the fixing plate (5) into a circle with the same inner diameter as the metal cylinder (4), drill a hole in the center of the cut circular fixing plate with an electric drill, insert the ceramic pin into the fixing plate with the drilled hole, and fix and bond the two together; Step 3, fix the hard piezoelectric ceramic (3) and the fixing plate (5) with the ceramic pin (2) in the metal cylinder, adjust the cavity length formed by the ceramic pin and the end face of the hard piezoelectric ceramic, and select the cavity length with the best interference signal between 0.5 mm and 0.6 mm, and finally fix and bond them with glue; Step 4, welding leads to the hard piezoelectric ceramics to connect the flexible piezoelectric material to complete the production of the optical fiber micro-strain sensor.

Images