A fiber-optic macrobend loss based bend sensor and a detection method thereof

Abstract

The application discloses a bending sensor based on macro-bending loss of an optical fiber and a detection method thereof. The bending sensor comprises a light emitting part, a light receiving part, an optical fiber connected between the light emitting part and the light receiving part, and a detection circuit; the optical fiber is arranged in direct or indirect association with an object to be detected and changes in bending state occur with deformation of the object to be detected, so that the macro-bending loss of the optical fiber changes with the deformation of the object to be detected; the light receiving part receives an optical signal transmitted through the optical fiber and outputs a corresponding electrical signal, and the detection circuit outputs a detection signal representing the change in macro-bending loss of the optical fiber according to the electrical signal, and the detection signal is used to determine the deformation parameter or deformation state of the object to be detected. In the calibration stage, the corresponding relationship between the deformation parameter and the normalized voltage change is established, and in the detection stage, the current deformation parameter is obtained according to the real-time output voltage. The application does not depend on complex spectral demodulation equipment and can be used in detection scenes such as robot joints, human joints integrated with clothes and battery bulging.

Description

Technical Field

[0001] This invention relates to the field of bending and deformation detection technology, and in particular to a bending sensor based on optical fiber macrobending loss and its detection method. Background Technology

[0002] Bending and deformation state detection has significant application value in fields such as robot motion perception, human motion recognition, battery state monitoring, flexible mechanism state monitoring, soft actuator deformation characterization, and joint motion detection. In these applications, it is typically necessary to detect changes in the bending angle, curvature, degree of bending, surface bulges, or deformation state of the object under test.

[0003] Existing resistive, capacitive, and strain gauge bending sensors may suffer from susceptibility to electromagnetic interference, limited flexibility, or inconvenience in long-distance signal transmission under complex environments. Optical fibers experience macro-bending loss when bent, and the greater the bend, the lower the light intensity transmitted to the receiving end. Therefore, changes in received light intensity can be used to detect the deformation of the object under test. However, light source attenuation, changes in optical coupling, installation differences, and environmental variations can cause baseline drift in the output signal, affecting long-term detection stability. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a bending sensor based on optical fiber macrobending loss and its detection method, in which the optical fiber is directly or indirectly associated with the object under test and bends with the deformation of the object under test. By detecting the changes in received light intensity and corresponding electrical signals caused by the macrobending loss of the optical fiber, the deformation parameters or deformation state of the object under test can be obtained.

[0005] A bending sensor according to an embodiment of the present invention includes a light-emitting part, a light-receiving part, an optical fiber connecting the light-emitting part and the light-receiving part, and a detection circuit. The light-emitting part is used to couple a detection optical signal into the optical fiber, and the light-receiving part is used to receive the optical signal transmitted through the optical fiber and output a corresponding electrical signal. The optical fiber is used to be directly or indirectly associated with the object under test, and its bending state changes with the deformation of the object under test, causing a corresponding change in macro-bending loss of the transmitted light. The detection circuit is used to output a detection signal characterizing the change in macro-bending loss of the optical fiber based on the electrical signal output by the light-receiving part, and the detection signal is used to determine the deformation parameters or deformation state of the object under test.

[0006] According to the detection method of the present invention, in the calibration stage, the object under test is sequentially placed in multiple known deformation states, the corresponding output voltage is collected, and the normalized voltage change is calculated based on the reference voltage to establish the correspondence between the deformation parameters and the normalized voltage change; in the detection stage, the current normalized voltage change is calculated based on the real-time output voltage, and the current deformation parameters or deformation state of the object under test is obtained based on the correspondence.

[0007] This invention directly utilizes the macro-bending loss generated by the bending of optical fiber as it deforms with the object under test for detection. It eliminates the need for complex spectral demodulation equipment and features a simple structure, small size, resistance to electromagnetic interference, and ease of integration with robot structures, clothing, or other objects under test. Furthermore, by employing normalized voltage changes and reference voltage updates, the impact of absolute light intensity variations and baseline drift on the detection results can be reduced.

[0008] A bending detection system according to an embodiment of the present invention includes a bending sensor 100 and a controller communicatively connected to a detection circuit 4. The controller is configured to perform calibration, reference voltage update, normalized voltage change calculation, and deformation parameter calculation.

[0009] In some embodiments of the present invention, the optical fiber is a step-index multimode optical fiber, the light-emitting part includes a transmitting housing and a light-emitting diode disposed in the transmitting housing, and the light-receiving part includes a receiving housing and a photodiode disposed in the receiving housing.

[0010] In some embodiments of the present invention, the transmitting housing and / or the receiving housing are provided with a connecting groove, and the end of the optical fiber is disposed in the connecting groove and fixed with glue.

[0011] In some embodiments of the present invention, the detection circuit includes a light-emitting circuit for driving the light-emitting diode to emit light, a light-receiving circuit for converting the electrical signal output by the photodiode into an output voltage, and a measurement circuit for acquiring and processing the output voltage.

[0012] In some embodiments of the present invention, the measurement circuit includes a signal acquisition and processing unit, which is used to perform one or more of the following: output voltage acquisition, filtering, conversion, averaging, outlier removal, normalized voltage change calculation, and deformation parameter calculation.

[0013] In some embodiments of the present invention, the two ends of the optical fiber are respectively disposed on two adjacent robot joints that can rotate relative to each other, and the optical fiber changes its bending state as the angle between the two robot joints changes.

[0014] In some embodiments of the present invention, the optical fiber is disposed on the surface of the battery to be tested or at a position adjacent to the surface of the battery to be tested, so as to change its bending state as the battery surface bulges or rises.

[0015] In some embodiments of the present invention, the optical fiber is disposed in clothing, protective gear or wearable carrier by at least one of the following methods: sewing, weaving, bonding and sleeve fixing, and crosses the joint area of ​​the human body so as to change the bending state as the human joint bends. Attached Figure Description

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the general structure, detection method, and application embodiments of the invention in conjunction with the following drawings, wherein: Figure 1 This is a perspective view of the bending sensor of the present invention; Figure 2 This is a partial exploded view of the bending sensor of the present invention; Figure 3 This is an installation diagram illustrating the application of the present invention to robot joint detection; Figure 4 This is a schematic diagram comparing the reference state and the bulging state of the present invention for battery bulging detection; Figure 5 This is a flowchart of the fiber macrobending loss detection method of the present invention; Figure 6 This is a circuit diagram of the detection circuit of the present invention.

[0017] Figure label: 100. Bending sensor; 1. Light-emitting part; 11. Emitting housing; 12. Light-emitting diode; 13. Connecting groove; 2. Light-receiving part; 21. Receiving housing; 22. Photodiode; 3. Optical fiber; 4. Detection circuit; 41. Light-emitting circuit; 411. Light-emitting power supply; 412. Protective resistor; 42. Light-receiving circuit; 421. Light-receiving power supply; 422. Resistor; 423. Capacitor; 43. Measurement circuit; 431. Signal acquisition and processing unit; 200. Robot joint components; 301. A battery in normal condition; 302. Batteries that are bulging. Detailed Implementation

[0018] The specific embodiments of the present invention are described in detail below, and related schematic diagrams are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The specific embodiments and application examples described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The following is for reference. Figures 1-6 The present invention describes the general structure of the bending sensor 100 based on the macro-bending loss of optical fiber 3 and its detection method.

[0022] like Figure 1 and Figure 6 As shown, the bending sensor 100 includes a light-emitting part 1, a light-receiving part 2, an optical fiber 3, and a detection circuit 4. The light-emitting part 1 is used to couple a detection optical signal to the optical fiber 3, the light-receiving part 2 is used to receive the detection optical signal transmitted through the optical fiber 3 and output a corresponding electrical signal, and the detection circuit 4 is used to drive the light-emitting part 1 to output the detection optical signal and convert the electrical signal output by the light-receiving part 2 into an output voltage.

[0023] Optical fiber 3 is used to be directly or indirectly associated with the object under test, and its bending state changes with the deformation of the object under test. The closer optical fiber 3 is to a straight state, the smaller the macro-bending loss, the greater the light intensity received by the light receiving part 2, and the greater the output voltage obtained by the detection circuit 4. When the degree of bending of optical fiber 3 increases, the macro-bending loss increases, the light intensity received by the light receiving part 2 decreases, and the corresponding output voltage decreases.

[0024] This invention directly utilizes the change in macrobending loss of optical fiber 3 caused by the deformation of the object under test for detection. Optical fiber 3 has advantages such as light weight, small size, strong resistance to electromagnetic interference, corrosion resistance, and long-distance transmission capability, making it suitable for integration with robot structures, flexible mechanisms, clothing, battery surfaces, or other objects under test.

[0025] like Figure 5 As shown, the detection methods include: S1. The optical fiber 3 is directly or indirectly associated with the object under test, so that the optical fiber 3 bends as the object under test deforms. Direct association may include fixing, bonding, or abutting the optical fiber 3 to the object under test; indirect association may include placing the optical fiber 3 on clothing, protective gear, flexible substrate, sleeve, or mounting component that moves synchronously with the object under test. S2. When the object under test is in a reference deformation state and the output voltage of the detection circuit 4 meets the preset stability condition, the output voltage of the detection circuit 4 is collected as the reference voltage. The reference deformation state can be the extended state of a robot joint or a human joint, the state where the battery is not bulging, the predetermined initial posture, or other predefined reference states; S3. Place the object under test in multiple known deformation states in sequence, and collect the calibration voltage V corresponding to each known deformation state; the known deformation states can be determined by an encoder, angle sensor, external angle ruler, angle platform, displacement sensor, thickness measuring device, standard shim, displacement platform or other measuring device. S4, based on the reference voltage and the calibration voltage corresponding to each known deformation state Calculate the normalized voltage change respectively. ; S5. Establish deformation parameters With normalized voltage change Correspondence between Within a certain detection range, the correspondence can be a linear relationship; within a larger detection range, the correspondence can be a piecewise linear relationship or a nonlinear relationship. S6. Acquire the real-time output voltage V, based on the reference voltage. and real-time output voltage Calculate the current normalized voltage change. And according to the corresponding relationship Obtain the current deformation parameters or deformation state of the object under test; S7. When the object under test returns to the reference deformation state and the output voltage meets the preset stability condition, update the reference voltage; when the updated detection deviation exceeds the preset deviation threshold, repeat S2 to S5.

[0026] The above method establishes a correspondence between deformation parameters by normalizing the voltage change, which reduces the dependence of the detection results on absolute light intensity. By updating the reference voltage, it can compensate for baseline drift caused by light source attenuation, changes in optical coupling, and environmental changes. Deformation parameters can be bending angle, curvature, bending radius, or degree of bending. When it is necessary to determine the deformation state, the normalized voltage change or the level classified according to the normalized voltage change can also be used as the characterization quantity of the deformation state.

[0027] During calibration and / or real-time detection, the output voltage of detection circuit 4 can be sampled multiple times continuously, and the sampling results can be processed by at least one of averaging and outlier removal to obtain a stable output voltage value. Preset stability conditions may include the range, variance, or rate of change of multiple consecutive sampled values ​​being less than a corresponding threshold.

[0028] like Figure 1 and Figure 2 As shown, in one specific structure, the optical fiber 3 is a step-index multimode fiber. The light-emitting part 1 includes a transmitting housing 11 and a light-emitting diode 12 disposed within the transmitting housing 11. The light-receiving part 2 includes a receiving housing 21 and a photodiode 22 disposed within the receiving housing 21. The light-emitting diode 12 is optically coupled to one end of the optical fiber 3, and the photodiode 22 is optically coupled to the other end of the optical fiber 3, so that the light emitted by the light-emitting diode 12 can reach the photodiode 22 after being transmitted through the optical fiber 3. Step-index multimode fibers have the advantages of simple structure, convenient optical coupling, and significant macro-bending loss changes under bending conditions.

[0029] like Figure 2 As shown, in a specific structure, the interior of the transmitting housing 11 and / or the receiving housing 21 is provided with a connecting groove 13. After the optical fiber 3 extends into the transmitting housing 11 and / or the receiving housing 21, part of the optical fiber 3 is disposed in the connecting groove 13. The connecting groove 13 is filled with glue to realize the connection between the optical fiber 3 and the transmitting housing 11 and / or the receiving housing 21.

[0030] like Figure 6 As shown, in a specific circuit structure, the detection circuit 4 includes a light-emitting circuit 41, a light-receiving circuit 42, and a measurement circuit 43. The light-emitting circuit 41 includes a light-emitting power supply 411 and a protective resistor 412 connected in series with the light-emitting diode 12, which is used to provide operating current for the light-emitting diode 12; the light-receiving circuit 42 includes a light-receiving power supply 421 and a resistor 422 connected in series with the photodiode 22; the measurement circuit 43 uses the voltage across the resistor 422 as the output voltage.

[0031] The greater the light intensity received by photodiode 22, the greater its output photocurrent, and the greater the output voltage across resistor 422. Furthermore, the light-receiving circuit 42 also includes a capacitor 423 connected in parallel across resistor 422. Capacitor 423 is used to suppress output noise and improve output voltage stability. The measurement circuit 43 includes a signal acquisition and processing unit 431. The signal acquisition and processing unit 431 is used to perform one or more of the following: output voltage acquisition, filtering, conversion, averaging, outlier removal, reference voltage update, and bending parameter calculation. In one specific embodiment, the signal acquisition and processing unit 431 is a microcontroller.

[0032] The light-emitting circuit 41 drives the light-emitting part 1 to output a detection light signal, the light-receiving circuit 42 converts the electrical signal output by the light-receiving part 2 into an output voltage, and the measuring circuit 43 collects and processes the output voltage. During the detection process, the greater the light intensity received by the light-receiving part 2, the greater the photocurrent output by the light-receiving part 2, and the greater the output voltage obtained by the detection circuit 4; the smaller the light intensity received by the light-receiving part 2, the smaller the output voltage.

[0033] During calibration and / or real-time detection, the output voltage of detection circuit 4 is sampled multiple times continuously, and the sampling results are subjected to at least one of the following processing methods: averaging and outlier removal.

[0034] Deformation parameters include at least one of bending angle, curvature, bending radius, and degree of bending.

[0035] When the object under test is in the reference deformation state and the output voltage meets the preset stability conditions, the reference voltage is updated to compensate for baseline drift caused by light source attenuation, optical coupling changes, installation errors and environmental changes; when the updated detection deviation exceeds the preset deviation threshold, the calibration is re-executed.

[0036] Furthermore, let the reference voltage of the bending sensor 100 under the reference deformation state be... The output voltage under known deformation state or real-time deformation state is: Then the normalized voltage change satisfy:

[0037] Deformation parameters With normalized voltage change The following relationship exists between them:

[0038] in, To determine the normalized voltage change based on multiple known deformation states and their corresponding normalized voltage changes. The corresponding relationship function is obtained through calibration. When the object under test returns to the reference deformation state and the output voltage meets the preset stability condition, the updated reference voltage can be used. calculate This compensates for baseline drift caused by light source attenuation, changes in optical coupling, installation errors, and environmental changes.

[0039] In some implementations, the output voltage change can also be used. As an auxiliary characterization quantity, it is used to help determine the light intensity change caused by the macro-bending loss of the optical fiber; when establishing the calibration relationship of the deformation parameters, the normalized voltage change is preferred. .

[0040] Example 1: Robot Joint Rotation Angle Detection. A light-emitting part 1 and a light-receiving part 2 are respectively disposed on two adjacent robot joints 200 that can rotate relative to each other. An optical fiber 3 connects the light-emitting part 1 and the light-receiving part 2 and crosses the joint area. When the two robot joints 200 rotate relative to each other, the optical fiber 3 bends with the change in joint angle. When the deformation parameter is the bending angle, the bending angle is related to the change in normalized voltage. The relationship between them can be represented as:

[0041] Within a certain range of joint rotation, the above relationship can be further approximated as a linear relationship:

[0042] in, and These are the coefficients obtained through calibration.

[0043] When it is necessary to use curvature When characterizing the deformation of a joint or flexible object, it can be expressed according to the calibration relationship as follows:

[0044] And can be based on curvature With bending radius The geometric relationship between them is further obtained as follows:

[0045] The above formula is used to illustrate the correspondence between the normalized voltage change and the deformation parameter in this invention; when using the output voltage change as an auxiliary characterization quantity, a corresponding relationship can also be established based on calibration. The specific function form can be determined through calibration according to the fiber optic parameters, installation method, and usage scenario, and does not constitute a limitation on this invention.

[0046] During robot joint testing, the light-emitting part 1 and the light-receiving part 2 can be fixed to both sides of the joint by screws, clips, adhesives, or mounting brackets, respectively. See [link / reference]. Figure 3 The fiber optic cable 3 can be reserved with a length that matches the range of joint rotation, allowing it to change continuously between the straightened and bent states of the joint, while avoiding exceeding the minimum allowable bending radius; during installation, the fiber optic cable 3 should be prevented from twisting, and the same installation state should correspond to the same calibration relationship.

[0047] To verify the feasibility of the detection method of this invention in detecting the bending angle of a robot joint, a step-index multimode optical fiber was used. The light-emitting part 1 and the light-receiving part 2 were fixed to both sides of the robot joint, with the optical fiber 3 spanning the robot joint area. The robot joint was subjected to multiple bending angles from 0° to 90° sequentially, and the output voltage of the detection circuit 4 was collected every 5°. The output voltage at 0° straightness is used as the reference voltage. Calculate the normalized voltage change. .

[0048] Table 1 Test data of robot joint bending angle and output voltage

[0049] in, The output voltage at 0° of straightness, i.e. =3.300V. As can be seen from Table 1, with the robot joint bending angle... As the voltage increases, the output voltage V gradually decreases, and the normalized voltage change... The gradual increase indicates that the change in macrobending loss of optical fiber 3 caused by joint bending can be effectively characterized by the detection circuit 4.

[0050] Based on the above multiple angle points, the bending angle can be established through linear fitting, piecewise linear fitting, or nonlinear fitting. With normalized voltage change Correspondence between During real-time detection, detection circuit 4 acquires the current output voltage. The controller or signal processing unit determines the voltage based on the reference voltage. calculate And obtain the current bending angle of the robot joint according to the correspondence.

[0051] The above test data are used to illustrate the trend of output voltage variation with the bending degree of optical fiber 3 in the detection method of the present invention. In practical applications, the calibration can be re-performed according to the type of optical fiber, installation method, parameters of light-emitting part 1 and light-receiving part 2, and structure of the object under test to obtain the angle calculation relationship under the corresponding application scenario.

[0052] Example 2: Human Joint Bending Detection Integrated with Clothing. A bending sensor 100 is disposed on clothing, protective gear, or a wearable carrier. An optical fiber 3 crosses the human joint area to change its bending state as the human joint bends. The human joint can be the elbow joint, knee joint, finger joint, shoulder joint, hip joint, or the lumbar region. This implementation is similar to the robot joint detection method, except that the optical fiber 3 is indirectly associated with the human joint through clothing, protective gear, or a wearable carrier.

[0053] The optical fiber 3 can be fixed to the surface or interlayer of clothing by stitching, woven into the clothing fiber structure, bonded to clothing or protective gear, or threaded into a flexible sleeve fixed to clothing. The light-emitting part 1 and the light-receiving part 2 can be respectively set on both sides of the joint area of ​​the human body, or they can be set together in the non-joint area of ​​the clothing and form a detection segment that crosses the joint area of ​​the human body through the extended optical fiber 3.

[0054] During calibration, the human joint is positioned in an extended state or a predetermined reference posture, and a reference voltage V0 is recorded. Subsequently, the human joint is positioned at multiple known bending angles, and the corresponding calibration voltages are recorded to establish a correspondence between the bending angle or degree of bending of the human joint and the normalized voltage change. During detection, the degree of bending or movement state of the human joint is obtained based on the real-time output voltage.

[0055] In the clothing integration embodiment, the relative sliding between the clothing and the human body may cause different optical fiber bending states corresponding to the same human joint angle. To reduce this effect, the degree of clothing fit can be adjusted, local fixing straps can be set, flexible sleeves can be set, the position of the optical fiber 3 across the human joint area can be limited, or recalibration can be performed for specific wearing conditions.

[0056] Besides robot joints and human joints, fiber optic cable 3 can also be associated with flexible mechanisms, soft actuators, or other objects under test that allow fiber optic cable 3 to bend with their deformation. These applications do not change the fundamental principle of determining deformation parameters or deformation states using changes in the macro-bending loss of fiber optic cable 3.

[0057] Example 3: Battery bulge detection. A bending sensor 100 is disposed on the surface of the battery to be detected or at a position adjacent to the surface of the battery to be detected, see [reference needed]. Figure 4 The two ends of the optical fiber 3 are fixed to the two sides of the battery area to be tested, and the middle part of the optical fiber 3 is attached to or abuts the surface of the battery to be tested, so that the optical fiber 3 can bend as the surface of the battery bulges.

[0058] When battery 301 is in a normal state, the initial state of the surface to be tested is used as the reference deformation state, and the reference voltage is recorded. When the battery 302 is in a bulging state, the surface of the battery bulges outward and pushes the optical fiber 3 that is attached to or abutting it to bend, which increases the macro-bending loss of the optical fiber 3, reduces the light intensity reaching the light receiving part 2, and the output voltage obtained by the detection circuit 4 decreases accordingly.

[0059] During battery bulge detection calibration, a calibration component simulating the surface of the battery to be tested can be used. This component sequentially forms multiple known bulge heights and drives the optical fiber 3, collecting the calibration voltage corresponding to each known bulge height and establishing a correspondence between bulge height, thickness variation, or bulge degree and normalized voltage variation. During detection, the bulge degree or bulge state of the battery is determined based on the real-time output voltage, and a warning signal can be output when a preset threshold is reached.

[0060] In some embodiments, the optical fiber 3 is bonded to the battery surface with insulating adhesive; in other embodiments, the optical fiber 3 is disposed between the battery surface and an adjacent insulating support or battery casing, so that the optical fiber 3 can bend when the battery bulges. The installation of the optical fiber 3 should avoid causing conductive connections, punctures, or excessive compression to the battery, and should ensure that the optical fiber 3 remains in a predetermined initial state when the battery is not bulging.

[0061] The above embodiments for detecting robot joints, human joints, and battery bulges illustrate that the bending sensor 100 can bend according to the deformation of the object under test through different installation methods. As long as the deformation of the object under test can cause a corresponding change in the bending state and macro-bending loss of the optical fiber 3, the detection principle of this invention can be used for detection.

[0062] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0063] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A bending sensor based on optical fiber macro-bending loss, characterized in that, include: The light-emitting part and the light-receiving part; An optical fiber, one end of which is optically coupled to the light-emitting part, and the other end of which is optically coupled to the light-receiving part; The optical fiber is used to be directly or indirectly associated with the object under test, and its bending state changes with the deformation of the object under test, so that the macro bending loss of the optical fiber changes with the deformation of the object under test. The light receiving part is used to receive the optical signal transmitted through the optical fiber and output the corresponding electrical signal. A detection circuit is used to output a detection signal characterizing the change in macrobending loss of the optical fiber based on the electrical signal, and the detection signal is used to determine the deformation parameters or deformation state of the object under test.

2. The bending sensor according to claim 1, characterized in that, The optical fiber is a step-index multimode optical fiber. The light-emitting part includes a transmitting housing and a light-emitting diode disposed in the transmitting housing. The light-receiving part includes a receiving housing and a photodiode disposed in the receiving housing.

3. The bending sensor according to claim 2, characterized in that, The transmitting housing and / or the receiving housing are provided with a connecting groove, and the end of the optical fiber is disposed in the connecting groove and fixed with glue.

4. The bending sensor according to claim 2, characterized in that, The detection circuit includes a light-emitting circuit for driving the light-emitting diode to emit light, a light-receiving circuit for converting the electrical signal output by the photodiode into an output voltage, and a measurement circuit for acquiring and processing the output voltage.

5. The bending sensor according to claim 4, characterized in that, The measurement circuit includes a signal acquisition and processing unit, which is used to perform one or more of the following: output voltage acquisition, filtering, conversion, averaging, outlier removal, normalized voltage change calculation, and deformation parameter calculation.

6. The bending sensor according to claim 1, characterized in that, The light-emitting part and the light-receiving part are respectively disposed on two adjacent robot joints that can rotate relative to each other. The optical fiber is connected between the light-emitting part and the light-receiving part and crosses the robot joint area so as to change the bending state as the angle between the two robot joints changes. And / or, the optical fiber is used to be disposed in clothing, protective gear or wearable carrier by at least one of sewing, weaving, bonding and sleeve fixing, and crosses the joint area of ​​the human body to change the bending state as the human joint bends; And / or, the optical fiber is used to be positioned on or adjacent to the surface of the battery to be tested, so as to change its bending state as the surface of the battery bulges, rises or changes in thickness change.

7. A method for detecting macrobending loss in optical fiber, characterized in that, Using the bending sensor according to any one of claims 1-6, the detection method comprises: S1. The optical fiber is directly or indirectly associated with the object under test, so that the optical fiber changes its bending state as the object under test deforms, so that the macrobending loss of the optical fiber changes as the object under test deforms. S2. When the object under test is in a reference deformation state and the output voltage of the detection circuit meets the preset stability condition, the output voltage of the detection circuit is collected as a reference voltage. S3. Place the object under test in multiple known deformation states in sequence, and collect the calibration voltage corresponding to each known deformation state. S4. Calculate the normalized voltage change corresponding to each known deformation state based on the reference voltage and each of the calibration voltages. S5. Establish the correspondence between the deformation parameters of the object under test and the normalized voltage change; S6. Acquire the real-time output voltage, calculate the current normalized voltage change based on the reference voltage and the real-time output voltage, and obtain the current deformation parameters or deformation state of the object under test based on the corresponding relationship. S7. When the object under test returns to the reference deformation state and the output voltage meets the preset stability condition, update the reference voltage; when the updated detection deviation exceeds the preset deviation threshold, repeat S2 to S5.

8. The detection method according to claim 7, characterized in that, The preset stability conditions include: the range, variance, or rate of change of the output voltage collected in multiple consecutive samples is less than the corresponding threshold.

9. The detection method according to claim 7, characterized in that, The normalized voltage change η satisfies: η=(V0) V) / V0; where V0 is the reference voltage, and V is the calibration voltage or the real-time output voltage; the deformation parameters include at least one of bending angle, curvature, bending radius, degree of bending and thickness change; the correspondence is a linear relationship, a piecewise linear relationship or a nonlinear relationship.

10. A bending detection system based on optical fiber macro-bending loss, characterized in that, The device includes a bending sensor as described in any one of claims 1-6 and a controller communicatively connected to the detection circuit, the controller being configured to perform the detection method as described in any one of claims 7-9.

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