Fbg flexible skin omnidirectional bending vector and normal force sensing system and decoupling method thereof

Abstract

The present application relates to a kind of FBG flexible skin omnidirectional bending vector and normal force sensing system and its decoupling method.The system includes sensing module, optical path module, signal processing module and control module;Sensing module includes three intelligent skin array units;Intelligent skin array unit includes skin layer and the measurement FBG sensor arranged in skin layer;Measurement FBG sensor includes first FBG sensor and second FBG sensor arranged in skin layer in the form of cross staggered;Optical path module includes broadband light source and first coupler.Signal conversion module includes second coupler, demodulation FBG sensor, photodetector and signal processing circuit.The present application can solve the deficiency in the prior art, realize omnidirectional bending vector and normal force measurement and decoupling, and obtain higher resolution, better repeatability, higher sensitivity and better stability of measurement performance.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, specifically to an omnidirectional bending vector and normal force sensing system for FBG flexible skin and its decoupling method. Background Technology

[0002] In bionic skin research, most studies employ electrical sensing mechanisms for measuring relevant quantities. Generally, electrical sensing mechanisms offer the following advantages: First, electrical sensors possess high sensitivity and high resolution. They can detect changes in the electrical signals of the omnidirectional bending vector and normal force sensing system of a tiny FBG flexible skin and its decoupling method, capturing minute changes in external stimuli and providing accurate sensory data. This allows the bionic skin to more accurately perceive the characteristics and changes in the external environment. Second, electrical sensors offer real-time performance and embeddability. They can typically be easily embedded into the external structure of artificial skin or robots, allowing the bionic skin to be tightly integrated with mechanical components. This enables real-time acquisition of sensory data and rapid transmission to relevant systems, achieving rapid response to external stimuli. Finally, electrical sensors are multifunctional and easy to integrate. They can be applied to various types of bionic skin to achieve different sensing and response functions, such as simulating tactile temperature sensing. Furthermore, electrical sensors are generally easy to integrate with electronic and computing systems, enabling the processing and analysis of sensory data. However, sensor-like mechanisms are susceptible to common electrical noise and magnetic fields generated by external factors or electrical systems, and are also affected by stray capacitance, thermal noise, and wiring crosstalk. In addition, since each sensor has a wired electrical dipole, this directly leads to wiring complexity, limits the number of components that can be integrated, and thus limits the spatial resolution of large-area sensing skin.

[0003] In optical sensing, fiber optic sensing mechanisms, especially fiber Bragg grating (FBG) sensors, possess significant competitive advantages. Their key feature is the ability to integrate multiple FBG sensors onto a single fiber. Each grating is associated with its nominal wavelength λ and can be flexibly customized in terms of length (from 1 mm to 20 mm) and position (along the fiber), enabling multiplexing and distributed sensing capabilities. This advantage allows for minimizing the number of necessary communication channels, thus reducing cabling management issues, facilitating high-density integration and manufacturing, achieving full coverage of large skin surfaces, and exhibiting high spatial resolution and a wide frequency response range. Furthermore, FBG sensors possess significant advantages such as strong electromagnetic interference resistance (passive magnetoelectric properties), high sensitivity, low hysteresis, wide linear range, high repeatability, fast frequency response, light weight, and long lifespan. In addition, many tactile sensors are typically developed using rigid components, which severely limit their flexibility, deformability, and adaptability to the environment within the limited space of the skin. Fiber optic sensors, on the other hand, are inherently small in size and flexible and bendable, making them easy to integrate into flexible bionic skin substrates, covering the entire body of the robot and meeting the fundamental requirements of future smart skin for robustness, flexibility, and agility.

[0004] Current research focuses on developing smart skin capable of sensing various external stimuli, including pressure, temperature, humidity, and deformation. These smart skins, by integrating different types of sensors, enable machines to mimic the sensory capabilities of human skin, providing a more realistic tactile experience. The flexibility and elasticity of smart skin are key characteristics, allowing it to adapt to objects of different shapes and changing environments. Researchers are exploring materials engineering and design methods to achieve highly variable skin structures. The development of novel materials is crucial for the realization of smart skin. Materials with properties such as flexibility, conductivity, and transparency, such as polymers, carbon nanotubes, and metal nanoparticles, are widely used in smart skin research. On the other hand, researchers are also developing data processing methods and models that can decouple complex external stimuli. These methods can extract useful information from sensor data and reproduce and predict human bending. Simultaneously, smart skin has broad application potential in robotics and prosthetics. Flexible skin can make robots interact with humans more safely, while smart prosthetics can provide a more natural tactile and motor experience. The development of smart skin also impacts the fields of human-computer interaction and virtual reality. By providing users with realistic tactile feedback, smart skin can enhance the immersion of virtual reality experiences.

[0005] Overall, research institutions both domestically and internationally have achieved certain results in the field of smart skin that mimics skin structures to sense human curvature. This research is expected to drive the development of smart skin technology and bring more innovative applications to fields such as medicine, robotics, and virtual reality. However, many technical challenges remain, such as improving sensing accuracy and material durability, requiring further research and breakthroughs.

[0006] Therefore, it is necessary to design and implement an omnidirectional bending vector and normal force sensing system for FBG flexible skin and its decoupling method. Summary of the Invention

[0007] The purpose of this invention is to provide an omnidirectional bending vector and normal force sensing system for FBG flexible skin and its decoupling method. This sensing system and its decoupling method can overcome the shortcomings of the prior art, realize the measurement and decoupling of omnidirectional bending vector and normal force, and obtain measurement performance with high resolution, good repeatability, high sensitivity and good stability.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect of the present invention, an omnidirectional bending vector and normal force sensing system for FBG flexible skin is disclosed.

[0009] Specifically, the system includes a sensing module, an optical path module, a signal processing module, and a control module.

[0010] The sensing module includes three intelligent skin array units arranged circumferentially around the structure under test; each intelligent skin array unit includes a skin layer and a measurement FBG sensor disposed in the skin layer; the measurement FBG sensor includes a first FBG sensor and a second FBG sensor arranged in a cross-shaped staggered layer in the skin layer; the three first FBG sensors and the three second FBG sensors are all distributed in an equilateral triangle in the cross-section of the second FBG sensor. The optical path module includes a broadband light source and a first coupler; the output end of the broadband light source is connected to the input end of the first coupler; the output end of the first coupler is connected to the input end of the FBG measurement sensor. The signal conversion module includes a second coupler, a demodulation FBG sensor, a photodetector, and a signal processing circuit; the input terminal of the second coupler is connected to the reflective terminal of the first coupler; the reflective terminal of the second coupler is connected to the input terminal of the photodetector; and the output terminal of the photodetector is connected to the input terminal of the signal processing circuit. The control module includes a data acquisition card and a host computer; the input terminal of the data acquisition card is connected to the output terminal of the signal processing circuit, and the data acquisition card is used to acquire the detection signal of the photodetector and transmit it to the host computer; the host computer is used to receive the detection signal from the data acquisition card and output a gating control signal to the optical switch matrix.

[0011] Furthermore, the number of the intelligent skin array units is three, and the three intelligent skin array units are arranged circumferentially around the structure under test. The three first FBG sensors and the three second FBG sensors are all distributed in an equilateral triangle on the cross-section of the second FBG sensor.

[0012] Furthermore, the smart skin array unit is used for measuring bending and normal forces.

[0013] Furthermore, the skin layer is molded from ecoflex material.

[0014] Furthermore, the first coupler is connected to the first FBG sensor and the second FBG sensor in each smart skin array unit through an optical switch matrix; the first FBG sensor and the second FBG sensor in each smart skin array unit are connected to different output terminals of the optical switch matrix in a one-to-one correspondence; the host computer controls the optical switch matrix to open the corresponding switch, so that the light emitted by the broadband light source passes through the first coupler and is transmitted to the corresponding FBG sensor.

[0015] Furthermore, the broadband light source is an ASE broadband light source.

[0016] In a second aspect of the invention, a method for decoupling the above-described FBG flexible skin omnidirectional bending vector and normal force sensing system is disclosed.

[0017] Specifically, the method includes: The light emitted by the broadband light source enters the different FBG sensors in each smart skin array unit through the optical switch matrix in a time-division manner. After being reflected by the FBG sensor, the light enters the demodulation FBG sensor. The demodulation FBG sensor demodulates the measurement signal of the FBG sensor to obtain the measurement value of each FBG sensor. The bending vector and normal force are determined based on the measurement value.

[0018] Furthermore, the demodulation FBG sensor demodulates the measurement signal of the FBG sensor to obtain the measurement value of each FBG sensor, including: The measurement signal of only one FBG sensor at any given time is demodulated using the demodulated FBG sensor. The optical switch matrix is ​​used to demodulate the six FBG sensors in the three smart skin array units in a time-division manner, so that the measurement value of each FBG sensor can be obtained. The host computer outputs a signal to control the six switches in the optical switch matrix connected to the FBG sensor to switch in a set order. The three first FBG sensors form a group, and the three second FBG sensors form a group. The time interval between each switch is t seconds. After each switch, there is a delay of T seconds for data acquisition. The data acquisition time for each switch is (tT) seconds. A data is acquired within the time interval of (tT). One cycle of switching is defined as the six switches in the optical switch matrix connected to the FBG measurement sensors switching in a set sequence, and one cycle takes 6t seconds; that is, the system performs a complete measurement within 6t seconds, obtaining the measurement values ​​of the six FBG sensors. .

[0019] Furthermore, determining the bending vector and normal force based on the measured values ​​includes: A decoupling model is established based on the measured values, and the bending vector and normal force are determined through the decoupling model.

[0020] Furthermore, the determination of the bending vector and normal force through the decoupling model includes: The magnitudes B and F of the pure bending and normal forces are solved using the following model: Direction of pure bending and normal force The solution is obtained from the following model: Where B represents the magnitude of the pure bending force, and F represents the magnitude of the normal force. These represent the directions of pure bending and normal forces, respectively. These are the measured values ​​from the three first FBG sensors, respectively; These are the measurement values ​​from the three second FBG sensors, respectively. The bending sensitivity of the three second FBG sensors are respectively; These are the normal force sensitivities of the three second FBG sensors, respectively. These are the bending components of the three second FBG sensors, respectively; These are the normal force components of the three second FBG sensors.

[0021] Compared with the prior art, the advantages of the present invention are: (1) This invention uses a fiber Bragg grating sensor to sense the omnidirectional bending vector and normal force of the smart skin. Compared with strain gauge, piezoresistive, and capacitive electrical sensors, it has excellent anti-electromagnetic interference capability and can achieve higher sensitivity and accuracy. The innovation of this invention lies in the fact that by distributing three smart skin array units in an equilateral triangle in the circumferential direction, it realizes the measurement of the bending magnitude and the identification of the bending direction in 360° omnidirectional direction, while decoupling the magnitude and direction of the normal force.

[0022] (2) The present invention proposes that the intelligent skin array unit adopts the staggered cross method to embed two FBG sensors into the soft skin layer, and the three intelligent skin array units are arranged in an equilateral triangle structure. By using three intelligent skin array units and 6 measuring FBG sensors, the omnidirectional bending vector and normal force can be measured, which greatly simplifies the measurement process and reduces the complexity of subsequent data processing.

[0023] (3) This invention compares and processes the measured values ​​of the first FBG sensor and the second FBG sensor in the intelligent skin array unit, and designs a corresponding mathematical model to decouple the output value of the measured FBG, ultimately realizing the decoupled measurement of the bending vector and the normal force. The decoupling mechanism of the omnidirectional bending vector and the normal force proposed in this invention has fewer parameters and the model is simple and easy to understand. Attached Figure Description

[0024] Figure 1 This is a diagram showing the composition of the FBG flexible skin omnidirectional bending vector and normal force sensing system in this invention. Figure 2 This is a schematic diagram of the intelligent skin array unit in this invention; Figure 3 The above are simulation diagrams of the strain of the first FBG sensor and the second FBG sensor when the intelligent skin array is bent in different directions in this invention.

[0025] in: 1. ASE broadband light source, 2. First coupler, 3. Optical switch matrix, 4. Measurement FBG sensor, 5. Second coupler, 6. Demodulation FBG sensor, 7. Photodetector, 8. Data acquisition card, 9. Host computer. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings: like Figure 1 The FBG flexible skin omnidirectional bending vector and normal force sensing system shown is designed based on the FBG sensing principle and includes a sensing module, an optical path module, a signal processing module, and a control module.

[0027] like Figure 2As shown, the sensing module includes multiple smart skin array units; the smart skin array units are used for measuring bending and normal forces. Each smart skin array unit includes a skin layer and a measurement FBG sensor 4 disposed within the skin layer; the measurement FBG sensor 4 includes a first FBG sensor 10 and a second FBG sensor 11 arranged in a cross-shaped staggered layer within the skin layer. The first FBG sensor is an optical fiber arranged along the X-axis, and the second FBG sensor is an optical fiber arranged along the Y-axis. The skin layer is molded from ecoflex material. In this embodiment, the number of smart skin array units is three, arranged circumferentially around the structure under test. The three first FBG sensors 10 and the three second FBG sensors 11 are all distributed in an equilateral triangle pattern on the cross-section of the second FBG sensor (11).

[0028] In some embodiments, the optical path module includes a broadband light source 1 and a first coupler 2; the output of the broadband light source 1 is connected to the input of the first coupler 2; the output of the first coupler 2 is connected to the input of the measurement FBG sensor 4. The broadband light source 1 is an ASE broadband light source. The first FBG sensors and second FBG sensors of the three smart skin array units are connected in a one-to-one correspondence to different outputs of the optical switch matrix 3. After passing through the first coupler 2, the broadband light source 1 is controlled by the host computer 9 to open different switches of the optical switch matrix 3, and the six measurement FBG sensors receive light from the first coupler 2 and perform measurements sequentially. The first coupler is connected to the first FBG sensor 10 and the second FBG sensor 11 in each smart skin array unit through the optical switch matrix; the first FBG sensor 10 and the second FBG sensor 11 in each smart skin array unit are connected in a one-to-one correspondence to different outputs of the optical switch matrix 3; the host computer 9 controls the optical switch matrix 3 to open the corresponding switches, so that the light emitted by the broadband light source passes through the first coupler 2 and is transmitted to the corresponding FBG sensor. Light emitted from broadband light source 1 enters different FBG sensors in a time-division manner through optical switch matrix 3. After being reflected by measurement FBG sensor 4, it enters the demodulation optical path. The measurement signal of only one measurement FBG sensor is set at any given time to be demodulated in the optical path module using the demodulation FBG sensor. The optical switch matrix 3 can realize time-division demodulation of six FBG sensors, and obtain the measurement value of each FBG sensor, thereby realizing omnidirectional bending vector measurement and normal force decoupling.

[0029] In some embodiments, the signal conversion module includes a second coupler 5, a demodulation FBG sensor 6, a photodetector 7, and a signal processing circuit; the input terminal of the second coupler 5 is connected to the transmitting terminal of the first coupler 2; the reflecting terminal of the second coupler 5 is connected to the input terminal of the photodetector 7; and the output terminal of the photodetector 7 is connected to the input terminal of the signal processing circuit. The first and second couplers are used for beam splitting. The demodulation FBG sensor provides a reference signal for demodulation, extracts environmental influences, and performs temperature error compensation. The signal processing circuit amplifies and filters the measured signal. The demodulation FBG sensor is used in combination with the measurement FBG sensor for demodulation.

[0030] In some embodiments, the control module includes a data acquisition card 8 and a host computer 9. The input terminal of the data acquisition card 8 is connected to the output terminal of the signal processing circuit. The data acquisition card 8 is used to acquire the detection signal from the photodetector 7 and transmit it to the host computer 9. The host computer 9 is used to receive the detection signal from the data acquisition card 8 and output a gating control signal to the optical switch matrix 3. The host computer 9 outputs a signal to control the six switches in the optical switch matrix 3 connected to the FBG measurement sensors to switch in a determined order. Three first FBG measurement sensors 10 form a group, and three second FBG measurement sensors 11 form a group. The time interval between each switch is t seconds, and data acquisition is performed after a delay of T seconds after each switch. The data acquisition duration for each switch is (tT) seconds, and one data point is acquired within the duration of (tT). One cycle of switching is defined by switching the six switches connected to the FBG measurement sensors in the optical switch matrix 3 in a set order. One cycle takes 6t seconds; that is, the system performs a complete measurement within 6t seconds, obtaining the measurement values ​​from the six FBG measurement sensors. The bending vector and normal force can be obtained by decoupling the model.

[0031] like Figure 1 As shown, the decoupling method for the above-mentioned FBG flexible skin omnidirectional bending vector and normal force sensing system is as follows: The light emitted by the broadband light source 1 enters the different FBG sensors in each smart skin array unit through the optical switch matrix 3 times. After being reflected by the FBG sensor, it enters the demodulation FBG sensor 6. The demodulation FBG sensor 6 demodulates the measurement signal of the FBG sensor to obtain the measurement value of each FBG sensor. The bending vector and normal force are determined based on the measurement value.

[0032] Furthermore, the demodulation FBG sensor 6 demodulates the measurement signal of the FBG sensor to obtain the measurement value of each FBG sensor, including: The measurement signal of only one FBG sensor at any given time is demodulated using the demodulated FBG sensor 6. The optical switch matrix 3 is used to demodulate the six FBG sensors in the three smart skin array units in a time-division manner, so that the measurement value of each FBG sensor can be obtained. The host computer 9 outputs signals to control the six switches in the optical switch matrix 3 connected to the FBG measurement sensors to switch in a set order. Three first FBG sensors 10 form one group, and three second FBG sensors 11 form another group. The time interval between each switch is t seconds, followed by a delay of T seconds for data acquisition. The data acquisition duration for each switch is (tT) seconds, and one data point is acquired within this (tT)-second time. One complete cycle of switching the six switches in the optical switch matrix 3 connected to the FBG measurement sensors in the set order constitutes one cycle of switching, and one cycle takes 6t seconds. That is, the system performs one complete measurement within 6t seconds, obtaining the measurement values ​​from the six FBG sensors. .

[0033] Furthermore, determining the bending vector and normal force based on the measured values ​​includes: A decoupling model is established based on the measured values, and the bending vector and normal force are determined through the decoupling model.

[0034] Furthermore, the determination of the bending vector and normal force through the decoupling model includes: The magnitudes B and F of the pure bending and normal forces are solved using the following model: Direction of pure bending and normal force The solution is obtained from the following model: The implementation process of the above decoupling method includes the following steps: S1. Conduct a qualitative analysis of the intelligent skin array unit and verify the feasibility of the system solution through simulation.

[0035] like Figure 3 As shown, for an intelligent skin array composed of three intelligent skin array units, the first column is a schematic diagram of the application of bending and normal forces and the results. In the second column, the solid lines, dashed lines, and dotted lines are the strain diagrams of the three second FBG sensors, respectively. The third column is the horizontal axis... The points correspond to the strain values ​​of the three first FBG sensors. Applying bending and normal forces in different directions results in the strains of the first and second measuring FBG sensors changing according to a certain pattern. The magnitude of the applied bending and normal forces is only reflected by the second measuring FBG sensor; that is, the magnitude of the bending and normal forces can be solved solely from the output value of the second measuring FBG sensor. The direction of bending can also be solved from the proportional relationship of the output values ​​of the second measuring FBG sensor. The radial angle of the applied normal force mainly needs to be reflected in the output of the first measuring FBG sensor, but it also contributes to the second FBG sensor. Therefore, the influence of bending needs to be decoupled during decoupling.

[0036] S2. Perform individual sensitivity calibration of pure bending amount and normal force for the 6 FBG sensors in the array.

[0037] In this embodiment, to calibrate the output voltage-bending and output voltage-normal force relationships of the FBG array system, the standard bending quantity is provided by the standard bending model, and the standard normal force quantity is provided by weights.

[0038] The simulation results show that the magnitude of the bending and normal forces, as well as the direction of the bending, can be determined from the second FBG sensor. Therefore, the output value of the second FBG sensor should be used first. Perform calibration. Assume the second measurement is performed using the FBG sensor output value. Let the sensitivity coefficients of each second FBG sensor to bending and normal forces be respectively... Apply bending individually Each The output of the second FBG sensor is recorded as follows: Then we have equation (1): Applying normal force alone The output of each second FBG sensor is recorded as follows: Then we have equation (2): It can be solved .

[0039] Similarly, the output value of the first FBG sensor is measured. After calibration, the sensitivity coefficients of each first FBG sensor to bending and normal forces can be obtained as follows: .

[0040] S3. Measurement is performed by an array sensing module composed of intelligent skin array units.

[0041] In this embodiment, the output signals of the first and second FBG sensors are measured. The data is transmitted from the acquisition card to the host computer.

[0042] S4. Decouple the output signals of the first and second FBG sensors obtained by the host computer.

[0043] In this embodiment, the host computer receives the output signals from the first and second FBG sensors of the data acquisition card. Then, according to equation (3): The magnitudes B and F of the pure bending and normal forces can be solved.

[0044] Substituting F into the equation to decouple the influence of the normal force F, only the pure bending B affects the output of each FBG sensor, thus obtaining the pure bending quantity outputs of the three second FBG sensors. As shown in equation (4): This leads to the bending angle vector, as shown in equation (5): Similarly, for the first FBG sensor, Substituting B into the equation, and decoupling the effect of pure bending B, only the normal force F affects the output of each FBG sensor, yielding the pure normal force outputs of the three first FBG sensors. As shown in equation (6): This leads to the radial application angle of the normal force. As shown in equation (7): Ultimately, the decoupled measurement of bending vector and normal force is achieved.

[0045] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A flexible FBG skin omnidirectional bending vector and normal force sensing system, characterized in that, The system includes a sensing module, an optical path module, a signal processing module, and a control module; The sensing module includes three smart skin array units arranged circumferentially around the structure under test; the smart skin array unit includes a skin layer and a measurement FBG sensor (4) disposed in the skin layer; the measurement FBG sensor (4) includes a first FBG sensor (10) and a second FBG sensor (11) arranged in a cross-shaped staggered layer in the skin layer; the three first FBG sensors (10) and the three second FBG sensors (11) are all distributed in an equilateral triangle on the cross section of the second FBG sensor (11); The optical path module includes a broadband light source (1) and a first coupler (2); the output end of the broadband light source is connected to the input end of the first coupler (2); the output end of the first coupler (2) is connected to the input end of the measurement FBG sensor (4); The signal processing module includes a second coupler (5), a demodulation FBG sensor (6), a photodetector (7), and a signal processing circuit; the input terminal of the second coupler (5) is connected to the output terminal of the measurement FBG sensor (4); the reflective terminal of the second coupler (5) is connected to the input terminal of the photodetector (7); and the output terminal of the photodetector (7) is connected to the input terminal of the signal processing circuit. The control module includes a data acquisition card (8) and a host computer (9); the input terminal of the data acquisition card (8) is connected to the output terminal of the signal processing circuit, and the data acquisition card (8) is used to acquire the detection signal of the photodetector (7) and transmit it to the host computer (9); the host computer (9) is used to receive the detection signal from the data acquisition card (8) and output the gating control signal to the optical switch matrix (3); The first coupler is connected to the first FBG sensor (10) and the second FBG sensor (11) in each smart skin array unit through an optical switch matrix; the first FBG sensor (10) and the second FBG sensor (11) in each smart skin array unit are connected to different output terminals of the optical switch matrix (3) in a one-to-one correspondence; the host computer (9) controls the optical switch matrix (3) to open the corresponding switch, so that the light emitted by the broadband light source passes through the first coupler (2) and is transmitted to the corresponding FBG sensor; the measurement signal of only one FBG sensor at any time is demodulated by the demodulating FBG sensor (6), and the optical switch matrix (3) is used to demodulate the six FBG sensors in the three smart skin array units in a time-division manner to obtain the measurement value of each FBG sensor.

2. The sensing system according to claim 1, characterized in that, The intelligent skin array unit is used for decoupled measurement of bending and normal forces.

3. The sensing system according to claim 1, characterized in that, The skin layer is molded from ecoflex material.

4. The sensing system according to claim 1, characterized in that, The broadband light source (1) adopts the ASE broadband light source.

5. A decoupling method for the omnidirectional bending vector and normal force sensing system of FBG flexible skin as described in any one of claims 1 to 4, characterized in that, The method includes: The light emitted by the broadband light source (1) enters the different FBG sensors in each smart skin array unit through the optical switch matrix (3) in a time-division manner. After being reflected by the FBG sensor, it enters the demodulation FBG sensor (6). The demodulation FBG sensor (6) demodulates the measurement signal of the FBG sensor to obtain the measurement value of each FBG sensor. The bending vector and normal force are determined based on the measurement value.

6. The decoupling method according to claim 5, characterized in that, The demodulation FBG sensor (6) demodulates the measurement signal of the FBG sensor to obtain the measurement value of each FBG sensor, including: The host computer (9) outputs a signal to control the six switches in the optical switch matrix (3) connected to the FBG sensor to switch in a set order. The three first FBG sensors (10) are in a group, and the three second FBG sensors (11) are in a group. The time interval between each switch is t seconds. After each switch, there is a delay of T seconds for data acquisition. The data duration of each switch is (tT) seconds. A data is acquired within the duration of (tT). One cycle of switching is achieved by switching the six switches connected to the FBG sensors in the optical switch matrix (3) in a set order. One cycle of switching takes 6t seconds; that is, the system performs a complete measurement within 6t time and obtains the measurement values ​​of the six FBG sensors. .

7. The decoupling method according to claim 6, characterized in that, The step of determining the bending vector and normal force based on the measured values ​​includes: A decoupling model is established based on the measured values, and the bending vector and normal force are determined through the decoupling model.

8. The decoupling method according to claim 7, characterized in that, The determination of the bending vector and normal force through the decoupling model includes: The magnitudes B and F of the pure bending and normal forces are solved using the following model: Direction of pure bending and normal force The solution is obtained from the following model: Where B represents the magnitude of the pure bending force, and F represents the magnitude of the normal force. These represent the directions of pure bending and normal forces, respectively. These are the measured values ​​from the three first FBG sensors, respectively; These are the measurement values ​​from the three second FBG sensors, respectively. The bending sensitivity of the three second FBG sensors are respectively; These are the normal force sensitivities of the three second FBG sensors, respectively. These are the bending components of the three second FBG sensors, respectively; These are the normal force components of the three second FBG sensors.

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