Cable bending stress detection device and method based on fiber grating sensor

Abstract

The invention relates to the technical field of cable bending stress detection, in particular to a cable bending stress detection device and method based on a fiber grating sensor. The detection device comprises an upper computer, main control end equipment and a cable optical fiber butt joint structure, and further comprises a plurality of optical fiber signal processing devices and optical fiber grating sensors. The upper computer is in communication connection with the main control end equipment through a DDS communication port, and the main control end equipment is in communication connection with the optical fiber signal processing device through a Modbus TCP communication port; wherein one fiber grating sensor is in communication connection with one fiber signal processing device, the other fiber signal processing devices are connected to the cable fiber butt joint structure through the remaining fiber grating sensors, and the cable fiber butt joint structure is installed at the end of the bent cable to be detected. According to the invention, an optical fiber signal processing device carrying an optical fiber grating sensor is taken as hardware, and respective advantages of the DDS and the Modbus TCP are fully utilized, so that the stress value of each cable core of the cable can be accurately obtained in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of cable bending stress detection, and in particular to a cable bending stress detection device and method based on a fiber grating sensor. Background Art

[0002] Aircraft cable assembly is an important quality control link in the aircraft assembly process. After the various cables on board are laid to each cabin according to the specified channels, they are installed and fixed with clamps. After being fixed, the cables will show different degrees of bending due to factors such as their own materials, length margin, and fixing method. Under different bending conditions, the stress conditions of the entire cable vary greatly, and the stress conditions of the wire cores at different positions inside the cable also vary greatly. If the cable continues to be subjected to large bending stress after being bent, the cable core will easily break, the overall service life of the cable will be reduced, and the docking reliability of the electrical connector will be greatly reduced.

[0003] At present, when installing cables on board, only a reference range of technical requirements such as length and curvature is given based on experience. However, due to the complexity of the onboard installation, the stress conditions inside the corresponding cables under different technical requirements are different, and there is no specific data support. In order to detect the reliability of aircraft cable assembly, the stress conditions of the cables must be obtained first. The fiber grating sensor is a sensor that converts the state of the measured object into a measurable optical signal. Its working principle is to send the incident light beam of the light source into the modulation area through the optical fiber. In the modulation area, the interaction with the external measured parameters (bending stress, temperature) causes the optical properties of the light, such as the wavelength, frequency, and phase of the light, to change and become a modulated optical signal. Then, it is sent to the optical fiber conversion and decoding module through the optical fiber. After demodulation, the measured parameters are obtained, and temperature compensation is used to eliminate the temperature influence, and finally the measured bending stress data is obtained. In the whole process, the light beam is introduced through the optical fiber, passes through the modulation area, and then is emitted. The role of the optical fiber is first to transmit the light beam, and secondly to play the role of light modulation.

[0004] At present, some existing technologies have used fiber Bragg grating, resistance strain gauge, vibrating wire strain measurement and other methods to collect bending stress in different scenarios. They can only detect the bending stress of the entire cable as a whole, and cannot measure the force of each core in the cable. However, these methods are inefficient for a large amount of data on aircraft cables, are complex to install, and are greatly affected by temperature. It is still necessary to design a special connection structure and use a more accurate fiber Bragg grating sensor with temperature compensation to further improve the cable bending stress measurement. Summary of the invention

[0005] The purpose of the present invention is to propose a cable bending stress detection device and method based on a fiber grating sensor to solve the problem that the cable bending stress collection measurement points in the aircraft system are huge and the engineering is complex, resulting in delayed data update and slow bending stress collection speed.

[0006] The above objectives are achieved specifically through the following technical solutions:

[0007] A cable bending stress detection device based on fiber grating sensor, comprising a host computer, a main control terminal device, a cable optical fiber docking structure and an optical fiber signal processing device; and A fiber grating sensor group corresponding to each fiber signal processing device, wherein One is a multi-channel optical fiber bending stress sensor, and the remaining one is a single-channel optical fiber temperature sensor;

[0008] The cable optical fiber docking structure is installed at the end of the bent cable to be tested, and includes a docking seat, on which is provided a A group of optical fiber plug-in channels; N is the maximum number of cores of the bending cable to be tested, n is the number of channels of a single group of multi-channel optical fiber bending stress sensors, is a positive integer;

[0009] The main control terminal device integrates a DDS communication port and a Modbus TCP communication port;

[0010] The host computer is connected to the main control terminal device through the DDS communication port for implementing data acquisition control and test operations after data acquisition;

[0011] The main control end device communicates with the A fiber optic signal processing device is communicatively connected to convert the data format of the test instruction through an internal intelligent gateway;

[0012] The single-channel optical fiber temperature sensor is communicatively connected to one of the optical fiber signal processing devices and is used to collect ambient temperature data of the bent cable to be tested;

[0013] Remaining The optical fiber signal processing device is connected to the optical fiber plug-in channel of the cable optical fiber docking structure one by one through a multi-channel optical fiber bending stress sensor, and is used to excite a light beam of a required wavelength for bending stress collection and collect bending stress data of the bent cable to be tested under the control of the ModbusTCP communication protocol.

[0014] Preferably, it also includes a test bench base plate, and the main control end equipment and the optical fiber signal processing device are installed on the test bench base plate.

[0015] Preferably, a cable fixing clamp is detachably mounted on the bottom plate of the test bench.

[0016] Preferably, each single group of the optical fiber plug-in channels includes n optical fiber plug-in assemblies; the optical fiber plug-in assembly includes a plug-in connector, a bending stress tube, an adapter, a protective shell and a pin with a wire; the two ends of the bending stress tube are respectively inserted into the connector and the adapter, and the two ends of the bending stress tube are respectively inserted with a metallized grating; the pin with a wire is axially inserted into the core of the bent cable to be tested from the end, and is relatively fixed to the core by a retaining spring; the protective shell is wrapped around the outside of the core of the bent cable to be tested and the pin with a wire, one end of which is prevented from detaching from the core by a retaining ring, and the other end is sleeved on the adapter.

[0017] Preferably, the optical fiber signal processing device integrates an optical fiber signal generating module and a transcoding module.

[0018] Preferably, the maximum number of wire cores of the bent cable to be tested is N=128, and the number of channels of a single group of multi-channel optical fiber bending stress sensors is n=4.

[0019] A cable bending stress detection method based on a fiber grating sensor adopts the above-mentioned cable bending stress detection device based on a fiber grating sensor, and comprises the following steps:

[0020] S1, starting the cable bending stress detection device through the host computer and initializing the cable bending stress detection program, including establishing DDS network communication and ModbusTCP network communication, and also initializing database key values ​​and program related variables;

[0021] S2, enter the main loop of the detection program, read the test instruction input by the user through the host computer, and determine whether it is an end-process instruction; if so, exit the main loop and the detection ends; if not, enter step S3;

[0022] S3, execution command function, after receiving the detection command, the main control end device converts the data format of the test command through the internal intelligent gateway, and controls the operation of the optical fiber signal processing device with the ModbusTCP communication protocol, including exciting the light beam of the wavelength required for bending stress collection, and also including collecting the original data of cable bending stress and cable ambient temperature through the multi-channel optical fiber bending stress sensor and the single-channel optical fiber temperature sensor;

[0023] S4, after decoding the original data of cable bending stress and cable ambient temperature, the decoding results are placed in the corresponding queues in the database according to the detection instruction type for the main control terminal device and the host computer to retrieve and manage, and then return to step S2.

[0024] Preferably, in step S1, the cable bending stress detection program calculated and run by the host computer includes operation storage, measurement channel selection, spectrum display, waveform testing, physical quantity testing, initialization temperature compensation and test start and stop.

[0025] Beneficial technical effects brought by the present invention:

[0026] 1) This technical solution proposes a cable bending stress detection device and method based on a fiber grating sensor. The device uses a fiber optic signal processing device equipped with a fiber grating sensor as hardware. In order to simultaneously process a maximum of 128 channels of fiber optic signals, a python driver encapsulation program is designed to communicate and transmit data with the main control end device through the DDS communication protocol. Modbus TCP communication is used to control the fiber grating sensor to obtain the bending stress acquisition and decoding results, and based on this, a certain temperature compensation processing is performed on the stress data to eliminate the influence of temperature on the measurement accuracy of the fiber grating sensor. Finally, the stress value of each cable core can be obtained in real time and accurately, providing a reference for real-time and accurate monitoring of the bending stress state of aircraft cables.

[0027] 2) This technical solution proposes a cable bending stress detection device and method based on a fiber grating sensor, which fully utilizes the respective advantages of DDS and Modbus TCP. The DDS network and Modbus TCP communication protocol form a double-layer structure through an intelligent gateway, building an efficient, real-time, reliable and compatible distributed network. The data acquisition decoding and transmission process of the detection device is accurate and efficient. During the operation of the cable bending stress detection device, the bending stress acquisition algorithm process runs through each device component, which can measure the cable bending stress. Compared with the general fiber grating demodulator, it can better detect the cable bending stress and is more practical. On this basis, the mapping relationship between the physical state of the bent cable and the stress value can be constructed by stress detection of different types of electrical connectors and cables in different bending states, and a cable bending recommendation model library can be established, which can be used to guide the installation of aircraft cables.

[0028] 3) This technical solution proposes a cable bending stress detection device based on a fiber grating sensor, which discloses a cable fiber docking structure that can accurately transmit the cable core deformation to the fiber optic sensor modulation area, is less affected by environmental interference, has high collection accuracy and long service life.

[0029] 4) This technical solution proposes a cable bending stress detection device based on a fiber grating sensor. The device has multiple measurement points and good compatibility. A single device can simultaneously measure the stress of a maximum of 128-core aviation cable, and is backward compatible with measuring the stress of cables with less than 128 cores. It can be used to measure cables installed on an aircraft or experimental platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the overall structure of the cable bending stress detection device;

[0031] Figure 2 It is a schematic diagram of the axial structure of the cable optical fiber docking structure;

[0032] Figure 3 It is a schematic diagram of an axial cross-sectional structure of a fiber grating sensor and a cable core connected via a cable optical fiber docking structure;

[0033] Figure 4 It is a schematic diagram of an axial cross-sectional structure of a fiber grating sensor and a cable core connected via a cable optical fiber docking structure;

[0034] Figure 5 Schematic diagram of the theoretical model of cable bending deformation;

[0035] Figure 6 It is a schematic diagram of the relationship between the line connecting any hole position B and the center point hole position A and the axis of the cable bending surface;

[0036] Figure 7 Schematic diagram of the relationship between the bending radius r based on any hole position B and the bending radius R based on the center point hole position A;

[0037] Figure 8 This is a spectrum diagram of a channel equipped with a fiber Bragg grating sensor when it is working;

[0038] Fig. 9 A schematic diagram showing the Modbus TCP data frame format;

[0039] Fig.10 This is the framework diagram of the DDS and Modbus TCP two-layer model for the main control end device;

[0040] Fig.11 It is a basic implementation flow chart of the cable bending stress detection method;

[0041] Fig.12 A schematic diagram showing a data decoding format of a transfer code module.

[0042] In the figure:

[0043] 1. Host computer; 2. Main control terminal equipment; 2.1. DDS communication port; 2.2. Modbus TCP communication port; 3. Cable fiber docking structure; 3.1. Docking seat; 3.2. Fiber optic plug assembly; 3.21. Plug-in connector; 3.22. Bending stress tube; 3.23. Adapter; 3.24. Protective shell; 3.25. Pin with wire; 3.26. Metallized grating; 3.27. Retaining spring; 3.28. Retaining ring; 4. Fiber optic signal processing device; 5. Multi-channel fiber optic bending stress sensor; 6. Single-channel fiber optic temperature sensor; 7. Test bench bottom plate; 8. Cable fixing clamp; 9. Bending cable to be tested; 9.1. Wire core; 9.2. Bending surface axis; 10. Signal / power line; 11. Fiber optic Bragg grating sensor. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0045] Therefore, the following detailed description of the invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Example 1

[0047] This embodiment discloses a cable bending stress detection device based on a fiber grating sensor, as a preferred implementation of the present invention. Figure 1 As shown, it includes a host computer 1, a main control terminal device 2, a cable optical fiber docking structure 3 and An optical fiber signal processing device 4; and A group of fiber grating sensors 11 corresponding to the fiber signal processing devices 4, wherein One is a multi-channel optical fiber bending stress sensor 5, and the remaining one is a single-channel optical fiber temperature sensor 6. The main control terminal device 2 may be an industrial computer, which integrates a DDS communication port 2.1 and a Modbus TCP communication port 2.2.

[0048] The cable optical fiber docking structure 3 is installed at the end of the bent cable 9 to be tested, and includes a docking seat 3.1, on which there are N is the maximum number of cores 9.1 of the bending cable 9 to be tested, n is the number of channels of a single group of multi-channel optical fiber bending stress sensors 5, is a positive integer.

[0049] The host computer 1 is connected to the main control terminal device 2 through the DDS communication port 2.1 for implementing data acquisition control and test operations after data acquisition. Specifically, the cable bending stress detection program / software is installed in the host computer 1, which includes data storage function, measurement channel selection function, spectrum display function, waveform test function, physical quantity test function, initialization temperature compensation function and test start and stop functions. The upper layer of the main control terminal device 2 establishes a remote connection with the host computer 1 through the DDS external network. During the test, the host computer 1 is operated by the user, and each test instruction issued by the user through the host computer 1 is transmitted to the main control terminal device 2 through the DDS external network in a specified interface format.

[0050] The main control device 2 communicates with the After receiving the test instruction from the host computer 1, the main control terminal device 2 converts the data format of the test instruction through the internal intelligent gateway, and then controls the optical fiber signal processing device 4 to excite the light beam of the wavelength required for bending stress collection through the Modbus TCP communication protocol, laying the foundation for subsequent bending stress collection.

[0051] The single-channel optical fiber temperature sensor 6 is connected to one of the optical fiber signal processing devices 4 for collecting the ambient temperature data of the bent cable 9 to be tested. The optical fiber signal processing device 4 is connected to the optical fiber plug-in channel of the cable optical fiber docking structure 3 one by one through the multi-channel optical fiber bending stress sensor 5, and is used to excite the light beam of the required wavelength for bending stress collection and collect the bending stress data of the bent cable 9 to be tested under the control of the Modbus TCP communication protocol.

[0052] Example 2

[0053] This embodiment discloses a cable bending stress detection device based on a fiber grating sensor, as a preferred implementation of the present invention. Figure 1 As shown, it includes a host computer 1, a main control terminal device 2, a cable optical fiber docking structure 3 and An optical fiber signal processing device 4; and A group of fiber grating sensors 11 corresponding to the fiber signal processing devices 4, wherein One is a multi-channel optical fiber bending stress sensor 5, and the remaining one is a single-channel optical fiber temperature sensor 6. The main control terminal device 2 may be an industrial computer, which integrates a DDS communication port 2.1 and a Modbus TCP communication port 2.2.

[0054] The cable optical fiber docking structure 3 is installed at the end of the bent cable 9 to be tested, and includes a docking seat 3.1, on which there are N is the maximum number of cores 9.1 of the bending cable 9 to be tested, n is the number of channels of a single group of multi-channel optical fiber bending stress sensors 5, is a positive integer.

[0055] The host computer 1 is connected to the main control terminal device 2 through the DDS communication port 2.1 for implementing data acquisition control and test operations after data acquisition.

[0056] The main control device 2 communicates with the The optical fiber signal processing device 4 is communicatively connected to the optical fiber signal processing device 4 and is used to convert the data format of the test instruction through the internal intelligent gateway.

[0057] The single-channel optical fiber temperature sensor 6 is connected to one of the optical fiber signal processing devices 4 for collecting the ambient temperature data of the bent cable 9 to be tested. The optical fiber signal processing devices 4 are connected to the optical fiber plug-in channels of the cable optical fiber docking structure 3 through the multi-channel optical fiber bending stress sensors 5 in a one-to-one correspondence, and are used to excite the light beam of the required wavelength for bending stress collection and collect the bending stress data of the bent cable 9 to be tested under the control of the Modbus TCP communication protocol.

[0058] Furthermore, the test bench bottom plate 7 is included, and the main control end device 2 and the optical fiber signal processing device 4 are installed on the test bench bottom plate 7. By setting the test bench bottom plate 7, the layout of the main control end device 2 and the optical fiber signal processing device 4 is uniformly planned, so that the components of the cable bending stress detection device are clear and easy to maintain.

[0059] Furthermore, a cable fixing clamp 8 is detachably mounted on the bottom plate 7 of the test bench. The cable fixing clamp 8 is used to fix the bending cable 9 to be tested. When performing relevant tests, no human assistance is required, and one person can complete the operation, which provides convenience for the practical application of the cable bending stress detection device.

[0060] Example 3

[0061] This embodiment discloses a cable bending stress detection device based on a fiber grating sensor, as a preferred embodiment of the present invention, combined with Figure 1 As shown, it includes a host computer 1, a main control terminal device 2, a cable optical fiber docking structure 3 and An optical fiber signal processing device 4; and A group of fiber grating sensors 11 corresponding to the fiber signal processing devices 4, wherein The main control terminal device 2 may be an industrial computer, which integrates a DDS communication port 2.1 and a Modbus TCP communication port 2.2. The multi-channel optical fiber bending stress sensor 5 is a multi-channel optical fiber bending stress sensor 5, and the remaining one is a single-channel optical fiber temperature sensor 6. The main control terminal device 2 may be an industrial computer, which integrates a DDS communication port 2.1 and a Modbus TCP communication port 2.2. The multi-channel optical fiber bending stress sensor 5 is a plurality of optical fiber grating sensors 11 wound together for detecting cable bending stress, and the single-channel optical fiber temperature sensor 6 is a optical fiber grating sensor 11 for detecting the ambient temperature of the cable.

[0062] The master control end device 2 integrates a DDS communication port 2.1 and a Modbus TCP communication port 2.2.

[0063] The cable optical fiber docking structure 3 is installed at the end of the bent cable 9 to be tested, and includes a docking seat 3.1, on which there are N is the maximum number of cores 9.1 of the bending cable 9 to be tested, n is the number of channels of a single group of multi-channel optical fiber bending stress sensors 5, is a positive integer.

[0064] The host computer 1 is connected to the main control terminal device 2 through the DDS communication port 2.1 for implementing data acquisition control and test operations after data acquisition.

[0065] The main control device 2 communicates with the The optical fiber signal processing device 4 is communicatively connected to the optical fiber signal processing device 4 and is used to convert the data format of the test instruction through the internal intelligent gateway.

[0066] The single-channel optical fiber temperature sensor 6 is connected to one of the optical fiber signal processing devices 4 for collecting the ambient temperature data of the bent cable 9 to be tested. The optical fiber signal processing devices 4 are connected to the optical fiber plug-in channels of the cable optical fiber docking structure 3 through the multi-channel optical fiber bending stress sensors 5 in a one-to-one correspondence, and are used to excite the light beam of the required wavelength for bending stress collection and collect the bending stress data of the bent cable 9 to be tested under the control of the Modbus TCP communication protocol.

[0067] Further, as shown in Figure and Figure 3 As shown, each single group of optical fiber plug-in channels includes n optical fiber plug-in components 3.2; Figure 4As shown, the optical fiber plug-in assembly 3.2 includes a plug-in connector 3.21, a bending stress tube 3.22, an adapter 3.23, a protective shell 3.24 and a wire pin 3.25; the two ends of the bending stress tube 3.22 are respectively inserted into the connector and the adapter 3.23, and the two ends of the bending stress tube 3.22 are respectively inserted into the metallized grating 3.26; the wire pin 3.25 is axially inserted into the core 9.1 of the bending cable 9 to be tested from the end, and is relatively fixed to the core 9.1 by a retaining ring 3.27; the protective shell 3.24 is wrapped around the core 9.1 of the bending cable 9 to be tested and the outside of the wire pin 3.25, one end of which is prevented from detaching from the core 9.1 by a retaining ring 3.28, and the other end is sleeved on the adapter 3.23.

[0068] In this technical solution, the fiber optic grating sensor 11 is connected to the core 9.1 of the bending cable 9 to be tested by setting the fiber optic plug-in assembly 3.2 in the cable fiber optic docking structure 3. The fiber optic plug-in assembly 3.2 is used to transmit the deformation caused by the bending stress of the corresponding single core 9.1 of the bending cable 9 to be tested to the fiber optic grating sensor 11, laying the foundation for the cable bending stress data collection. According to the characteristics of the cable bending arc, the cable bending stress causes the deformation length Among them, Figure 5 , Figure 6 and Figure 7 As shown, the center O of the bending arc is determined based on the bending surface of the bent cable to be tested, and the bending radius r based on the arbitrary hole position B and the bending radius R based on the center point hole position A are further drawn. Therefore, L represents the original line length of the bent cable 9 to be tested based on the center point hole position A; L' represents the line length of the bent cable 9 to be tested based on the arbitrary hole position B after bending; d represents the distance from the arbitrary hole position B to the center point hole position A; θ is the angle between the line connecting the arbitrary hole position B and the center point hole position A and the axis 9.2 of the bending surface of the wire core 9.1; Indicates the bending angle of the wire core 9.1.

[0069] When 0≤θ≤90°, the wire core 9.1 is located inside the curved channel and its length is shortened; when 90°≤θ≤180°, the wire core 9.1 is located outside the curved channel and its length is increased.

[0070] Example 4

[0071] This embodiment discloses a cable bending stress detection device based on a fiber grating sensor, as a preferred implementation of the present invention, that is, based on Embodiment 1, 2 or 3, its fiber optic signal processing device 4 is an n-channel fiber optic signal processing device 4, which integrates a fiber optic signal generating module and a transcoding module.

[0072] That is, the lower layer of the main control terminal device 2 is connected to the n-channel optical fiber signal processing device 4 through a signal line, and standard ModbusTCP communication is used to transmit data. The optical fiber signal processing device 4 acts as a ModbusTCP server, and the main control terminal device 2 acts as a TCP client, and reads data in a responsive manner through a specific function code (FunctionCode). According to the developed ModbusTCP communication function code No. 03, the n-channel optical fiber signal processing device 4 transcodes the received frame represented in hexadecimal form into a decimal form. The communication process is a single frame sending and a single frame receiving. The transcoding module sends a test instruction frame to the fiber grating sensor 11. The fiber grating sensor 11 obtains the original data of the cable bending stress and the original data of the ambient temperature after measurement, and then returns a frame of data to the transcoding module, and then obtains the real value of the bending stress acquisition through the data transcoding module. Each fiber grating sensor 11 carried on the fiber optic signal processing device 4 has a specific Modbus address, and the data frames sent and received have a specific arrangement format. It is a continuous string of hexadecimal data streams, and the data stream needs to be acquired and decoded according to the communication protocol. For each data frame, it is necessary to extract information by bytes in sequence according to the specified arrangement format to complete the test process of the fiber optic signal generation and transcoding module. The real acquisition value is transmitted back to the main control terminal device 2 via the ModbusTCP communication protocol, and after the data format is converted by the intelligent gateway of the main control terminal device 2, it is sent back to the host computer 1 via the DDS external network and displayed and stored for users to read and manage.

[0073] The fiber Bragg grating sensor 11 is mounted on the n-channel fiber signal processing device 4 as the equipment hardware for collecting bending stress and ambient temperature, and is used to collect the original data of bending stress and ambient temperature. channels, front Each channel has n fiber Bragg grating sensors 11 for measuring bending stress, and the last channel contains only one fiber Bragg grating sensor 11 for measuring ambient temperature for temperature compensation. The light beam incident from the optical fiber signal generating module is sent to the modulation area via the optical fiber. The light interacts with the external measured parameters (bending stress, ambient temperature) in the modulation area, causing the optical properties of the light (such as the wavelength of the light) to change and become a modulated optical signal. The light signal is then sent to the optical fiber signal conversion and decoding module via the optical fiber, and the measured parameters are obtained after demodulation. The central wavelength of the fiber Bragg grating λ=2mΛ, where m is the effective refractive index of the optical fiber core, and Λ is the modulation period of the refractive index of the optical fiber core. The central wavelength λ of the fiber Bragg grating changes under the action of strain ε and temperature T, that is, the change in the central wavelength λ of the fiber Bragg grating Δλ=λ(K ε ε+K T ΔT); where K ε Indicates the strain coefficient; K Trepresents the temperature variation coefficient; ΔT represents the temperature variation.

[0074] Example 5

[0075] This embodiment discloses a cable bending stress detection method based on a fiber Bragg grating sensor. As a preferred embodiment of the present invention, a cable bending stress detection device based on a fiber Bragg grating sensor according to Embodiment 1, 2, 3 or 4 is adopted. Fig.11 As shown, the following steps are included:

[0076] S1, start the cable bending stress detection device through the host computer 1, and initialize the cable bending stress detection program (python driver encapsulation program), including establishing DDS network communication and Modbus TCP network communication, and also including initializing database key values ​​and program related variables. Further, the cable bending stress detection program calculated and run by the host computer 1 includes operation storage, measurement channel selection, spectrum display, waveform test, physical quantity test, initialization temperature compensation and test start and stop.

[0077] S2, enter the main loop of the detection program, read the test instruction input by the user through the upper computer 1, and determine whether it is an end-process instruction; if so, exit the main loop and the detection ends; if not, enter step S3.

[0078] S3, execute the instruction function. After the main control end device 2 receives the detection instruction, it converts the data format of the test instruction through the internal intelligent gateway, and controls the operation of the optical fiber signal processing device 4 with the ModbusTCP communication protocol, including exciting the light beam of the required wavelength for bending stress collection, and also including collecting the original data of cable bending stress and cable ambient temperature through the multi-channel optical fiber bending stress sensor 5 and the single-channel optical fiber temperature sensor 6.

[0079] S4, after decoding the original data of cable bending stress and cable ambient temperature, the decoding results are placed in the corresponding queues in the database according to the detection instruction type, so that the main control terminal device 2 and the host computer 1 can retrieve and manage them, and then return to step S2.

[0080] Example 6

[0081] This embodiment discloses a cable bending stress detection device and method based on a fiber grating sensor 11. As a preferred embodiment of the present invention, the cable bending stress detection device includes a host computer 1, a main control terminal device 2, a cable fiber docking structure 3 and 33 fiber signal processing devices 4; it also includes 33 fiber grating sensor 11 groups corresponding to the fiber signal processing devices 4, 32 of which are 4-channel fiber bending stress sensors, and the remaining 1 is a single-channel fiber temperature sensor 6. The 4-channel fiber bending stress sensor includes 4 fiber grating sensors 11, and the single-channel fiber temperature sensor 6 includes 1 fiber grating sensor 11. The main control terminal device 2 integrates a DDS communication port 2.1 and a Modbus TCP communication port 2.2.

[0082] The cable optical fiber docking structure 3 is installed at the end of the bent cable 9 to be tested, and includes a docking seat 3.1, on which 32 sets of optical fiber plug-in channels are arranged. The upper computer 1 is connected to the main control terminal device 2 through the DDS communication port 2.1 for implementing data acquisition control and test operations after data acquisition. The main control terminal device 2 is connected to the 33 optical fiber signal processing devices 4 through the Modbus TCP communication port 2.2 for converting the data format of the test instructions through the internal intelligent gateway.

[0083] The single-channel optical fiber temperature sensor 6 is connected to one of the optical fiber signal processing devices 4 in communication, and is used to collect the ambient temperature data of the bending cable 9 to be tested; the remaining 32 optical fiber signal processing devices 4 are connected to the optical fiber plugging channels of the cable optical fiber docking structure 3 through the multi-channel optical fiber bending stress sensor 5, and are used to excite the light beam of the required wavelength for bending stress collection and collect the bending stress data of the bending cable 9 to be tested by being controlled by the Modbus TCP communication protocol. The optical fiber signal processing device 4 is a 4-channel optical fiber signal processing device 4, which integrates an optical fiber signal generation module and a transcoding module.

[0084] Based on this, in practical application:

[0085] First, a bending cable 9 to be tested with no more than 128 cores 9.1 is installed through the cable fiber docking structure 3. The technical solution is compatible with measuring cables with less than 128 cores 9.1. This embodiment takes a 128-core cable as an example of a bending cable 9 to be tested. The bending cable 9 to be tested can be a cable installed in an aircraft cabin or a cable installed on a laboratory table. Secondly, 129 fiber grating sensors 11 are connected to 33 4-channel fiber optic signal processing devices 4 through optical fibers. A combination plug is then set at the end of 128 of the fiber grating sensors 11, that is, for each single fiber grating sensor 11, the plug-in connector 3.21, the metallized grating 3.26 and the bending stress tube 3.22 are connected to the wire pin 3.25 through an adapter 3.23 to form a combination plug. The remaining fiber grating sensor 11 is placed in the air near the cable to measure the ambient temperature as temperature compensation.

[0086] Third, 33 4-channel fiber optic signal processing devices 4 are connected to a master control device 2 through signal / power lines 10, and the communication protocol is Modbus TCP; the master control device 2 is connected to the host computer 1 through a network cable, and the communication standard is the DDS protocol; the DDS network of the master control device 2 and the Modbus TCP communication protocol form a double-layer heterogeneous network structure through an intelligent gateway.

[0087] Fourth, the host computer 1 inputs the initialization temperature compensation instruction, measures the ambient temperature through the last fiber grating sensor 11, and performs initialization temperature compensation on the other 128 fiber grating sensors 11. The host computer 1 inputs the bending stress measurement instruction, and transmits it to the optical fiber signal processing device 4 through the main control terminal device 2 and the communication cable. The light source emits a light beam of a specified wavelength (such as 1500-1600nm) and enters the signal modulation area through the optical fiber. In the modulation area, the interaction with the external measured parameters (deformation bending stress, ambient temperature) causes the wavelength of the light beam to change and become a modulated optical signal, which is then reflected back to the optical fiber conversion and decoding module through the optical fiber. After demodulation, the measured parameters are obtained, and finally the measured bending stress data is obtained.

[0088] The spectrum generated in the above process is a binary relationship diagram between the optical fiber wavelength (unit: nm) and the optical power (unit: dBm), indicating the optical properties of the fiber grating sensor 11 during operation. Figure 8As shown in the figure, the curve represents the spectrum of the four fiber grating sensors 11 carried by the 17th fiber signal processing device 4 when they are working. Each peak represents that a fiber grating sensor 11 is connected and working, and their grating center wavelength values ​​are 1530.5nm, 1542.2nm, 1547.9nm and 1554.0nm respectively. When the fiber grating sensor 11 is connected and working, due to the change of optical properties inside it and the incidence and emission of light, the optical power is significantly higher than the measuring point where the fiber grating sensor 11 is not connected, generating a peak. The horizontal coordinate value corresponding to the peak is the grating center wavelength value of the fiber grating sensor 11, which is generally 1500-1600nm.

[0089] Fifth, Modbus TCP communication frame definition, the developed Modbus TCP communication uses 03 function code to transmit data, with frame as the unit, single frame sending and single frame receiving. Fig. 9 The figure shows the frame-by-frame sending and receiving data monitored by the Modbus TCP communication debugging assistant. The format of the sending frame is as follows (the 03 function code is fixed):

[0090]

[0091] The above sample instruction indicates to read 4 WORD type data starting from Modbus data address 0000H from the device with address 1, that is, to read 2 consecutive sensor data, numbered 00101 and 00102. A and B in the table are the command serial numbers sent by the host computer 1.

[0092] After reading the data from the fiber grating sensor 11, the data frame format sent back by the fiber signal processing device 4 is as follows:

[0093]

[0094] Among them, the returned data is the key data, which is the hexadecimal representation of the deformation bending stress signal collected. Every 4 bytes represent the original bending stress data collected by the fiber grating sensor 11. According to the 03 function code transmission regulations of the developed Modbus TCP communication, the decoding format of these returned data is as follows: Fig.12 shown.

[0095] Regulations: After the 4-byte bending stress raw data is converted to decimal, it must be divided by 10000 to obtain the actual bending stress acquisition value. Fig. 9The content presented reads only one acquisition value of a fiber Bragg grating sensor 11 each time, so the bending stress acquisition value represented by frame 000001-Tx is 321.6789, and the bending stress acquisition value represented by frame 000003-Tx is 12.3456. Therefore, the two measured values ​​returned by the example data are 12.3456 and 321.6789 respectively. The reason for the uncertain length of the returned data is that in the read instruction sent by the host computer 1, the number of fiber Bragg grating sensors 11 read at a time is determined by the user. In the example, the bending stress data of two fiber Bragg grating sensors 11 are read. A and B are the command serial numbers sent by the host computer 1, which are used to identify the order of this frame.

[0096] Finally, after measuring the bending stress value of the core 9.1 at the end of the cable plug, the bending stress data is recorded and analyzed in the upper computer 1 to determine whether the bending stress value exceeds the bending stress limit of the cable. If it exceeds the bending stress limit of the core 9.1 of this type, the risk of the core 9.1 breaking is high, so it is determined that the cable installation bending radius is unreasonable. It is also possible to measure a large number of installation cables with different numbers of cores 9.1 and different bending radii, establish an installation cable bending stress database, extract the installation cable process requirements, and use them to guide the installation of cables on aircraft.

Claims

1. A cable bending stress detection device based on a fiber grating sensor, characterized in that: The invention comprises a host computer (1), a main control terminal device (2), a cable optical fiber docking structure (3) and N / n+1 optical fiber signal processing devices (4); and A group of fiber grating sensors (11) corresponding one to one with the fiber signal processing devices (4), wherein One is a multi-channel optical fiber bending stress sensor (5), and the remaining one is a single-channel optical fiber temperature sensor (6); The cable optical fiber docking structure (3) is installed at the end of the bent cable (9) to be tested, and comprises a docking seat (3.1) on which a group of optical fiber plug-in channels; N is the maximum number of cores 9.1 of the bending cable 9 to be tested, n is the number of channels of a single group of multi-channel optical fiber bending stress sensors (5), is a positive integer; The main control terminal device (2) integrates a DDS communication port (2.1) and a Modbus TCP communication port (2.2); The host computer (1) is connected to the main control terminal device (2) through the DDS communication port (2.1) for implementing data acquisition control and test operations after data acquisition; The master control terminal device (2) communicates with the A fiber optic signal processing device (4) is communicatively connected and used for converting the data format of the test instruction through an internal intelligent gateway; The single-channel optical fiber temperature sensor (6) is communicatively connected to one of the optical fiber signal processing devices (4) and is used to collect ambient temperature data of the bent cable (9) to be tested; Remaining The optical fiber signal processing device (4) is connected to the optical fiber plug-in channel of the cable optical fiber docking structure (3) in a one-to-one correspondence via a multi-channel optical fiber bending stress sensor (5), and is used to excite a light beam of a required wavelength for bending stress collection and collect bending stress data of the bending cable (9) to be tested under the control of the Modbus TCP communication protocol.

2. A cable bending stress detection device based on a fiber grating sensor (11) as claimed in claim 1, characterized in that: It also comprises a test bench bottom plate (7), on which the main control terminal equipment (2) and the optical fiber signal processing device (4) are installed.

3. A cable bending stress detection device based on a fiber grating sensor (11) as claimed in claim 2, characterized in that: A cable fixing clamp (8) is also detachably mounted on the test bench bottom plate (7).

4. A cable bending stress detection device based on a fiber grating sensor (11) as claimed in claim 1, characterized in that: Each single group of optical fiber plug-in channels comprises n optical fiber plug-in assemblies (3.2); the optical fiber plug-in assembly (3.2) comprises a plug-in connector (3.21), a bending stress tube (3.22), an adapter (3.23), a protective housing (3.24) and a lead pin (3.25); the two ends of the bending stress tube (3.22) are respectively inserted into the connector and the adapter (3.23), and the two ends of the bending stress tube (3.22) are respectively inserted into a metallized grating ( 3.26); the lead pin (3.25) is axially inserted into the core (9.1) of the bent cable (9) to be tested from the end, and is relatively fixed to the core (9.1) by a retaining spring (3.27); the protective shell (3.24) is wrapped around the core (9.1) of the bent cable (9) to be tested and the outside of the lead pin (3.25), one end of which is provided with a retaining ring (3.28) to prevent the core (9.1) from being separated, and the other end is sleeved on the adapter (3.23).

5. A cable bending stress detection device based on a fiber grating sensor (11) as claimed in claim 1, characterized in that: The optical fiber signal processing device (4) integrates an optical fiber signal generating module and a transcoding module.

6. A cable bending stress detection device based on a fiber grating sensor (11) as claimed in claim 1, characterized in that: The maximum number N of the wire cores (9.1) of the bending cable (9) to be measured is 128, and the number of channels of a single group of multi-channel optical fiber bending stress sensors (5) is n=4.

7. A cable bending stress detection method based on a fiber grating sensor (11), characterized in that: A cable bending stress detection device based on a fiber grating sensor (11) according to any one of claims 1 to 6 is adopted, comprising the following steps: S1, starting the cable bending stress detection device through the host computer (1), and initializing the cable bending stress detection program, including establishing DDS network communication and ModbusTCP network communication, and also initializing database key values ​​and program related variables; S2, enter the main loop of the detection program, read the test instruction input by the user through the upper computer (1), and determine whether it is an end-process instruction; if so, exit the main loop and the detection ends; if not, enter step S3; S3, executing the command function, after receiving the detection command, the main control end device (2) converts the data format of the test command through the internal intelligent gateway, and controls the optical fiber signal processing device (4) to work by using the ModbusTCP communication protocol, including exciting the light beam of the wavelength required for bending stress collection, and also including collecting the original data of cable bending stress and the original data of cable ambient temperature through the multi-channel optical fiber bending stress sensor (5) and the single-channel optical fiber temperature sensor (6); S4, after decoding the original data of cable bending stress and cable ambient temperature, the decoding results are placed in the corresponding queues in the database according to the detection instruction type, so that the main control terminal device (2) and the host computer (1) can retrieve and manage them, and then return to step S2.

8. A cable bending stress detection method based on a fiber grating sensor (11) as claimed in claim 7, characterized in that: In the step S1, the cable bending stress detection program calculated and run by the host computer (1) includes operation storage, measurement channel selection, spectrum display, waveform test, physical quantity test, initialization temperature compensation and test start and stop.

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