Bending sensor and preparation method thereof

Abstract

The invention discloses a bending sensor and a preparation method thereof, the sensor comprises a plurality of sensing units in end-to-end connection, each sensing unit comprises a first connector, a sensing main body and a second connector, and the first connector and the second connector are respectively located at two ends of the sensing main body; the first connector of one sensing unit is connected with the second connector of another sensing unit, and the second connector of one sensing unit is connected with the first connector of another sensing unit; the sensing main body comprises an outer wrapping layer and a fiber core layer, and the outer wrapping layer wraps the periphery of the fiber core layer; a light-emitting part is arranged in the first connector and is used for emitting a light source, and the light source can be conducted in the sensing main body and is conducted from one end of the fiber core layer to the other end of the fiber core layer to obtain conducted light; and a photosensitive module is arranged in the second connector and is used for judging the bending angle of the sensing main body according to the light intensity attenuation of the conduction light relative to the light source. The sensor has the advantages of modularization, high flexibility and assemblability, and can ensure accurate angle measurement.

Description

Technical Field

[0001] This application relates to the technical field of sensors, and particularly to a bending sensor and a preparation method thereof. Background Art

[0002] Monitoring human joint movements is crucial in various fields, including human motion analysis, rehabilitation medicine, sports training, and human-computer interaction. The human body, as a highly complex biomechanical system, relies on the coordinated actions of multiple joints for daily activities, from walking and running to grasping objects and performing fine gestures. For example, precise operation of the hand involves complex coordination between finger joints, wrist joints, and metacarpophalangeal joints, enabling tasks from writing to operating delicate tools. Similarly, the spine, as the central axis of the body, exhibits flexibility and stability at its segments, which is crucial for maintaining balance and protecting the spinal cord and nerve roots. Therefore, accurately monitoring multiple human joints simultaneously is an indispensable technology for clinical diagnosis and treatment, rehabilitation outcome assessment, and sports training analysis.

[0003] Currently, human multi-joint detection mainly relies on two major sensor technologies: camera-based motion capture systems and wearable sensing technologies. Camera-based systems use high-resolution cameras to capture images of human movements and analyze the positions and trajectories of joints through computer vision algorithms. These systems have the advantage of non-contact measurement and can capture full-body movements with high precision. However, they are limited by environmental factors such as lighting conditions, occlusion problems, and the need for special spaces. In addition, their high equipment costs and complex installation processes limit their widespread application. On the other hand, wearable sensing technologies are favored for their portability, real-time performance, and environmental adaptability. These technologies mainly include inertial sensors (such as accelerometers, gyroscopes), and flexible sensors based on sensitive materials. Inertial sensors directly measure acceleration and angular velocity and estimate the angles and positions of joints through algorithms, but their accuracy may be easily affected by noise interference and cumulative errors. Flexible sensors based on sensitive materials have unique advantages in monitoring joint ranges of motion due to their excellent compliance and high sensitivity to bending and stretching deformations. However, most existing wearable sensors are only designed for single-joint monitoring, making it difficult to achieve synchronous measurement at multiple joints and body parts. More importantly, these sensors usually lack the ability to be flexibly assembled and cannot be adaptively adjusted according to individual differences, joint numbers, and lengths, thus limiting their application potential in multi-joint monitoring scenarios. Summary of the Invention

[0004] The main technical problem to be solved by this application is to provide a bending sensor and a preparation method thereof, which solve the limitations in flexibility, accuracy, and adaptability of existing multi-joint monitoring.

[0005] To solve the above technical problems, a technical solution adopted in this application is to provide a bending sensor, which includes a plurality of sensing units connected end to end. The sensing unit includes a first connector, a sensing body, and a second connector. The first connector and the second connector are respectively located at both ends of the sensing body. The first connector is used to connect the second connector of another sensing unit, and the second connector is used to connect the first connector of yet another sensing unit. The sensing body includes an outer cladding layer and a core layer, and the outer cladding layer wraps around the periphery of the core layer. A light-emitting component is provided in the first connector, and the light-emitting component is used to emit a light source. The light source can be conducted in the sensing body, and the light source is conducted from one end of the core layer to the other end of the core layer to obtain the conducted light. A photosensitive module is provided in the second connector, and the photosensitive module is used to judge the bending angle of the sensing body according to the light intensity attenuation of the conducted light relative to the light source.

[0006] Based on the same inventive concept, this application also provides a method for preparing a bending sensor. The method includes the following steps: preparing the outer cladding layer, first inserting a support rod and an elastic wire into a mold, then injecting a liquid flexible material into the mold, and taking it out of the mold after curing to form the outer cladding layer; preparing the core layer, first pulling out the support rod from the first through hole of the outer cladding layer, and then sequentially inserting a plurality of short optical fiber segments into the first through hole of the outer cladding layer to form the core layer; installing connectors, installing a first connector and a second connector at both ends of the outer cladding layer respectively to form a sensing unit; connecting a plurality of the sensing units end to end to obtain a bending sensor; wherein, the first connector of one sensing unit is connected to the second connector of another sensing unit, and the second connector of one sensing unit is connected to the first connector of yet another sensing unit.

[0007] The beneficial effects of the present application are as follows: The present application discloses a bending sensor, which includes a plurality of sensing units connected end to end. Each sensing unit includes a first connector, a sensing body, and a second connector. The first connector and the second connector are respectively located at both ends of the sensing body. The first connector of one sensing unit is used to connect the second connector of another sensing unit, and the second connector of one sensing unit is used to connect the first connector of yet another sensing unit. The sensing body includes an outer cladding layer and a core layer, and the outer cladding layer wraps around the periphery of the core layer. A light-emitting element is provided in the first connector, and the light-emitting element is used to emit a light source. The light source can be conducted in the sensing body. The light source is conducted from one end of the core layer to the other end of the core layer to obtain the transmitted light. A photosensitive module is provided in the second connector, and the photosensitive module is used to judge the bending angle of the sensing body according to the light intensity attenuation of the transmitted light relative to the light source. This design emphasizes modularity, high flexibility, and assemblability, and can be customized for different joints, while ensuring accurate angle measurement. The present application also discloses a preparation method of the bending sensor. The sensor prepared by this method can achieve rapid customization and accurate multi-joint monitoring, solving the limitations of the prior art. Its modular design, low error, and wireless integration highlight the potential of personalized healthcare and human-machine interfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic diagram of the overall structure of an embodiment of a bending sensor according to the present application;

[0009] Figure 2 is a schematic diagram of a partial cross-section of an embodiment of a bending sensor according to the present application;

[0010] Figure 3 is a schematic diagram of the stress when a sensing unit bends in an embodiment of a bending sensor according to the present application;

[0011] Figure 4 is a schematic diagram of the structures of the first connector and the second connector in an embodiment of a bending sensor according to the present application;

[0012] Figure 5 is a schematic circuit diagram of an embodiment of a bending sensor according to the present application;

[0013] Figure 6 is a schematic optical path diagram of an embodiment of a bending sensor according to the present application;

[0014] Figure 7 is a chromatographic coordinate diagram when a sensing unit bends in an embodiment of a bending sensor according to the present application;

[0015] Figure 8 is a spectral signal diagram when a sensing unit bends in an embodiment of a bending sensor according to the present application;

[0016] Figure 9 It is a diagram showing the change in visible light attenuation of the sensing unit at different strain levels in an embodiment of a bending sensor according to the present application;

[0017] Figure 10 It is a diagram showing the change in the overall light emission intensity of visible light of each sensor node in an embodiment of a bending sensor according to the present application;

[0018] Figure 11 It is a displacement network diagram of the short optical fiber section under the 90° bending condition of the sensing unit in an embodiment of a bending sensor according to the present application;

[0019] Figure 12 It is a correlation diagram between the bending angle, theoretical attenuation and strain of the short optical fiber section in an embodiment of a bending sensor according to the present application;

[0020] Figure 13 It is an experimental result diagram of subjecting the sensing unit to 1000 tensile cycles at a rate of 15% in an embodiment of a bending sensor according to the present application;

[0021] Figure 14 It is a hysteresis response diagram of the sensing unit at the 1st, 500th and 1000th tensile cycles in an embodiment of a bending sensor according to the present application;

[0022] Figure 15 It is a light intensity attenuation step response diagram of the sensing unit at different strain levels at different times in an embodiment of a bending sensor according to the present application;

[0023] Figure 16 It is a light intensity attenuation response diagram of the sensing unit corresponding to different strain levels at the same time in an embodiment of a bending sensor according to the present application;

[0024] Figure 17 It is a test result diagram of testing the maximum static magnetic force of the sensing unit using a standard tension sensor in an embodiment of a bending sensor according to the present application;

[0025] Figure 18 It is an ILI response diagram of the sensing unit when bending from 0° to 90° in an embodiment of a bending sensor according to the present application;

[0026] Figure 19 It is a relationship diagram between temperature and ILI response of the sensing unit in an embodiment of a bending sensor according to the present application;

[0027] Figure 20 It is a monitoring result diagram of the monitoring experiment on finger joints in an embodiment of a bending sensor according to the present application;

[0028] Figure 21It is a measurement result diagram of each sensor node during the finger joint monitoring experiment in an embodiment of a bending sensor according to the present application;

[0029] Figure 22 It is a measurement result diagram of the bending angles of each finger joint during the finger joint monitoring experiment in an embodiment of a bending sensor according to the present application;

[0030] Figure 23 It is a monitoring result diagram of the spinal region monitoring experiment in another embodiment of a bending sensor according to the present application;

[0031] Figure 24 It is a measurement result diagram of the bending angles of each joint during the spinal region monitoring experiment in an embodiment of a bending sensor according to the present application;

[0032] Figure 25 It is a flowchart of an embodiment of a preparation method of a bending sensor according to the present application;

[0033] Figure 26 It is a schematic diagram of the physical preparation process of an embodiment of a preparation method of a bending sensor according to the present application. Detailed implementation manners

[0034] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present application.

[0035] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly disposed on the other component; when a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component.

[0036] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0037] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" and "several" mean two or more, unless otherwise clearly and specifically defined.

[0038] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which this application can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the effects and purposes that can be achieved by this application.

[0039] For the description of this application, the following is used in a non-limiting manner: Figure 1 The marks "front", "rear", "up", "down", "left" and "right" shown in the figure are used to facilitate understanding of the embodiment and are not intended to limit the present application. Among them, the front-to-back direction represents the longitudinal direction, the left-to-right direction represents the transverse direction, and the up-down direction represents the vertical direction.

[0040] Figures 1 - 6 An embodiment of a bending sensor of the present application is shown, which includes a plurality of end-to-end connected sensing units 1, wherein the sensing unit 1 includes a first connector 2, a sensing body 3, and a second connector 4, wherein the first connector 2 and the second connector 4 are respectively located at two ends of the sensing body 3; wherein the first connector 2 of one sensing unit 1 is used to connect to the second connector 4 of another sensing unit 1, and the second connector 4 of one sensing unit 1 is used to connect to the first connector 2 of yet another sensing unit 1; the sensing body 3 includes an outer cladding 31 and a core layer 32, wherein the outer cladding 31 is wrapped around the periphery of the core layer 32; a light-emitting component is provided in the first connector 2, and the light-emitting component is used to emit a light source, and the light source can be conducted in the sensing body 3, and the light source is conducted from one end of the core layer 32 to the other end of the core layer 32 to obtain the conducted light; a photosensitive module is provided in the second connector 4, and the photosensitive module is used to judge the bending angle of the sensing body 3 according to the attenuation of the light intensity of the conducted light relative to the light source.

[0041] like Figure 2 As shown, a plurality of elastic wires 33 are inserted into the outer covering layer 31 to supply power to the light-emitting element and enable the photosensitive module to perform data communication.

[0042] Combination Figure 3, when a single sensing unit 1 bends, internal stresses will appear on both sides of the sensing unit 1. Therefore, this application uses elastic wires 33 with stress relief capabilities, and strategically places four elastic wires 33 around the core layer 32 ( Figure 2 above, below, in front of, and behind the core layer 32 shown), which can ensure that the sensing unit 3 will not break.

[0043] As Figure 2 shown, the core layer 32 includes a plurality of short optical fiber segments 34 arranged side by side with the same size and the same spacing distance.

[0044] It should be noted that the core layer 32 uses PMMA optical fibers. PMMA optical fibers have the characteristics of high refractive index and low optical loss, resulting in negligible attenuation of light intensity during short-distance propagation. Therefore, the sensor experiences insignificant optical bending loss, resulting in a decrease in the sensitivity of the sensing unit. In addition, when the sensor bends, the mismatch in elastic modulus between the PMMA optical fiber and the elastic outer cladding 31 easily causes stress concentration in the PMMA optical fiber, increasing the possibility of microcrack formation or fiber fracture. To alleviate these challenges, this application divides the PMMA optical fiber into several short optical fiber segments 34 to fill the outer cladding 31 of the sensing unit 1, thereby significantly increasing the macroscopic bending loss rate of the PMMA optical fiber and alleviating the internal residual stress.

[0045] As Figure 4 shown, the first connector 2 includes three groups of contact rings, and the second connector 4 includes three groups of contacts respectively corresponding to and connected to the three groups of contact rings; the three groups of contact rings are the first contact ring 21, the second contact ring 22, and the third contact ring 23 from the inside out, and the three groups of contacts are the first contact 41, the second contact 42, and the third contact 43 from the inside out.

[0046] Furthermore, the first contact ring 21 and the corresponding first contact 42 are voltage common collector (VCC) contacts, which are used as the positive power supply of the bending sensor. The second contact ring 22, the third contact ring 23, and the corresponding second contact 42, the third contact 43 are integrated circuit bus (IIC) contacts, which are used to transmit data of the photosensitive module; among them, the serial data line (SDA) and the serial clock line (SCL) are respectively used to transmit data and provide a synchronous clock signal for the photosensitive module. The outer sides of the first connector 2 and the second connector 4 are both made of metal conductors, which are used as the negative power supply (GND) of the bending sensor. This design helps to reduce the size of the bending sensor. After the first connector 2 is joined with the corresponding second connector 4, the contacts are precisely aligned to ensure the stability of the electrical performance of the sensor.

[0047] Furthermore, the connection between the first connector 2 and the second connector 4 is a magnetic connection, which can achieve the rapid assembly of the bending sensor and facilitate the customization of bending sensors with different lengths for different joints.

[0048] It should be noted that according to experimental experience, when the length of a single sensing unit 1 is less than 10 cm, it can form a constant curvature during the bending process, thereby accurately measuring the bending deformation.

[0049] Furthermore, the length of the sensing unit 1 in the present application is less than 10 cm.

[0050] As Figure 1 shown, the sensing body 3 is a horizontally placed cylinder. At this time, the length of the obtained sensing body 3 is 80 mm, and the cross-sectional diameter is 4 mm. The lengths of the outer cladding 31 and the core layer 32 are the same as the length of the sensing body 3, and the cross-sectional diameter of the core layer 32 is 1.5 mm; and within a core layer 32, the spacing between adjacent short optical fiber segments 34 is 0.5 mm. The cross-sectional diameters of the first connector 2 and the second connector 4 are the same, both being 5 mm; and the total length after the first connector 2 and the second connector 4 are correspondingly connected is 7 mm.

[0051] In some other embodiments, generally, the length of the obtained sensing body 3 is between 50 mm and 90 mm, and the cross-sectional diameter is between 3 mm and 5 mm. The lengths of the outer cladding 31 and the core layer 32 are the same as the length of the sensing body 3, also between 50 mm and 90 mm; the cross-sectional diameter of the core layer 32 is between 1 mm and 2.5 mm; and within a core layer 32, the spacing between adjacent short optical fiber segments 34 is between 0.3 mm and 0.7 mm. The cross-sectional diameters of the first connector 2 and the second connector 4 are the same, both being between 4 mm and 6 mm; and the total length after the first connector 2 and the second connector 4 are correspondingly connected is between 5 mm and 10 mm. Other sizes are also possible, as long as the sizes of each part of the sensing unit 1 meet the actual usage requirements.

[0052] As Figure 5 shown, the light-emitting component uses a micro LED 20, and the micro LED 20 is integrated on the first connector 2 through surface mount technology (SMT), and the wavelength of the light source emitted by the micro LED 20 is between 380 nm and 780 nm.

[0053] Furthermore, the photosensing module includes a photon chip 40 for converting an optical signal into an electrical signal. In this embodiment, the photon chip 40 is integrated on one side of the second connector 4 connected to the sensing body 3, and the light intensity at the end of the sensing unit 1 (the end where the second connector 4 is installed) can be detected.

[0054] In this embodiment, the bending sensor further includes a wireless front end, which includes a voltage source, a microcontroller, and a wireless communication module; the voltage source is used to provide operating voltages for the light-emitting element, the photon chip 40, the microcontroller, and the wireless communication module; the microcontroller communicates with the photon chips 40 of multiple sensing units 1 through an integrated circuit bus and processes the data from the photon chips 40 of each sensing unit 1; the wireless communication module is used to transmit the processed data to a computer for display.

[0055] Further, the microcontroller uses the chip STM32F103RCT6, the voltage source uses the chip AMS1117, and the wireless communication module uses the chip NRF2401L. The voltage source provides stable operating voltages for the wireless communication module, the microcontroller, and the sensing unit 1. The microcontroller communicates with the sensing unit nodes (photon chips 40) through an integrated circuit bus and processes the data of each sensing unit node. The processed data is transmitted to a computer for display through the wireless communication module.

[0056] In this embodiment, the wireless front end is used for signal processing, and the overall system complexity is low, which is convenient for the miniaturization and lightweight integration of the bending sensor in wearable devices.

[0057] As Figure 5 shown, the voltage common collector (VCC) and the negative power supply (GND) of the bending sensor serve as power buses to provide operating voltages for the micro-LED 20 and the photon chip 40 in each sensing unit 1. The serial data line (SDA) and the serial clock line (SCL) constitute the integrated circuit bus (IIC). Among them, each photon chip 40 has an independent device label stored in a specific register, and the master device can obtain signals from each sensing unit node through the integrated circuit bus (IIC) by means of a polling read method.

[0058] As Figure 6 shown, when the sensing unit 1 maintains a straight configuration, the photon chip 40 can determine the light intensity at the end of the sensor. Since the length of the short optical fiber segment 34 is short, the light transmittance loss in the optical fiber can be ignored. There are certain gaps between each small part of the short optical fiber segment 34. Therefore, only the light loss in the gaps needs to be considered. The attenuation of light in these gaps can be expressed as follows:

[0059] ;

[0060] Among them, and respectively represent the input and output light intensities; e represents the natural logarithm; and d respectively represent the absorption coefficient of air and the interval distance between two adjacent short optical fiber segments 34. Therefore, the intensity of light at the end of the sensing unit 1 can be expressed as the first formula:

[0061] ;

[0062] Among them, n is the total number of gaps between the short optical fiber segments 34 in each core layer 32. The corresponding optical intensity attenuation can be expressed as the second formula:

[0063] .

[0064] Furthermore, substituting the first formula into the second formula , the relationship between the interval distance between two adjacent short optical fiber segments 34 in the same core layer 32 and the optical intensity attenuation can be obtained:

[0065] .

[0066] From this, it can be clearly seen that the attenuation of the optical intensity in the sensing unit 1 is determined by the interval distance d between two adjacent short optical fiber segments 34 after segmentation and the total number of gaps n.

[0067] Furthermore, when the sensing unit 1 is bent, the interval distance between two adjacent short optical fiber segments 34 increases, which will cause a change in the output optical intensity. Therefore, the bending angle of the sensing unit 1 can be determined according to the change in the optical intensity attenuation.

[0068] As Figure 7 and Figure 8 shown, one end of the sensing unit 1 is fixed, and the other end is bent from 0° to 90° in increments of 10° for a bending experiment to obtain the chromatographic coordinate diagram and spectral signal diagram of the corresponding spectrum. Figure 7 It shows that the chromatographic coordinates of the spectrum remain stable at (0.174, 0.523), indicating that the chromaticity is relatively stable. Figure 8 It shows the change of the spectral signal, indicating that as the bending angle increases, the overall intensity of the spectral signal decreases.

[0069] Combined with Figure 9 , Figures (A)-(F) show the normalized spectral distributions of the sensing unit 1 when the strains are 0%, 3%, 6%, 9%, 12%, and 15% respectively. Figure (G) shows the relationship between the optical intensity attenuation of red light, green light, and blue light and the strain level of the sensing unit 1. Figure (H) shows the comparison of the optical intensity attenuation of red light, green light, and blue light, the three visible lights, of the sensing unit 1 at the strain level of 0% - 15%. It can be seen that the visible light with a wavelength between 490 nm and 570 nm exhibits a greater attenuation rate.

[0070] As Figure 10As shown, Figures a - c show the changes in the overall light emission intensity (ILI) of visible light corresponding to each sensor node when the cascaded bending sensor is bent at different sensor nodes. The ILI of this bending sensor can be expressed as:

[0071] ;

[0072] where represents the wavelength of visible light with a value between 490 nm and 570 nm; represents the spectral function.

[0073] Furthermore, in order to study the bending characteristics of the bending sensor in a multi - node cascaded configuration, this application designed three groups of experiments, which respectively involved the simultaneous bending of a single node, two nodes, and three nodes. Each group of experiments was repeated five times, and the results are as shown in Figure 10 a - c. As shown in Figure 10 a, the repeatability errors of the three sensor nodes are 0.19 dB, 0.11 dB, and 0.14 dB respectively. The results show that the independent bending of sensor node 3 does not interfere with other nodes. Figure 10 Figure b shows the ILI response when sensor node 2 and sensor node 3 are bent simultaneously. When sensor node 2 and sensor node 3 are bent simultaneously, the repeatability errors of the three nodes are 0.13 dB, 0.18 dB, and 0.16 dB respectively; in addition, the signal from sensor node 1 is not affected by crosstalk interference. As shown in Figure 10 c, the low repeatability errors observed when the three sensor nodes are bent simultaneously are 0.25 dB, 0.21 dB, and 0.24 dB respectively. It can be seen that the ILI responses of each sensor node at the same bending angle are consistent.

[0074] As shown in Figure 11 , a displacement network diagram of multiple short optical fiber segments 34 under a 90° bending condition is shown, and a uniform displacement distribution of the short optical fiber segments 34 can be observed.

[0075] As shown in Figure 12 , the correlation between the theoretical attenuation and the strain of the short optical fiber segment is shown as the bending angle increases. It can be seen that the results of the strain of the short optical fiber segment and the theoretical attenuation are similar, indicating a linear relationship between the light intensity attenuation and the strain of the short optical fiber segment.

[0076] Furthermore, the sensing unit 1 is installed on a specific stretching device and subjected to 1000 stretching cycles at a rate of 15%, and the corresponding experimental results are as shown in Figure 13 . Among them, detailed views of the signal in the initial and last 20 cycles are provided. It can be seen that these illustrations show a high degree of consistency, indicating the repeatability of the bending of the sensing unit 1.

[0077] As shown Figure 14 in the figure, the hysteresis response characteristics of the sensing unit 1 at the 1st, 500th, and 1000th stretching cycles are shown. Among them, the calculation method of the hysteresis coefficient E is as follows:

[0078] ;

[0079] Among them, represents the hysteresis error; represents the attenuation range of the sensing unit 1. The results show that the hysteresis coefficients of the 1st cycle, 500th cycle, and 1000th cycle are 4.5%, 8.6%, and 7.8% respectively, indicating that the sensing unit 1 has stable ILI response characteristics.

[0080] As shown Figure 15 and Figure 16 in the figure, the step response of the light intensity attenuation in the stretching range of the sensing unit 1 corresponding to the strains of 2.5%, 5%, 7.5%, 10%, and 12.5% at different times, and the light intensity attenuation response of the sensing unit 1 corresponding to the strains of 2.5%, 5%, 7.5%, 10%, and 12.5% at the same time point are respectively shown. It can be seen that the larger the stretching range, the more the corresponding light intensity attenuation.

[0081] As shown Figure 17 in the figure, since the cascaded assembly of the sensing unit 1 requires the attraction of two sets of magnets, the maximum static magnetic force of the sensing unit 1 was tested in this application by using a standard tension sensor. It can be seen that when the maximum static magnetic force of the sensing unit 1 reaches 5N, a stable connection between the first connector 2 and the second connector 4 is allowed.

[0082] As shown Figure 18 in the figure, in order to study the relationship between the bending angle and the overall luminous intensity of the sensing unit 1 during the bending process, the ILI response of the sensing unit 1 when bending from 0° to 90° was also tested in this application. Among them, the relationship between the bending angle and ILI can be obtained by linear fitting to get the mapping relationship:

[0083] ;

[0084] Among them, represents the bending angle; ; ; represents the light intensity measured by the photon chip 40 in the sensing unit 1; represents the compensation function regarding temperature; the coefficient of determination . The experimental results show that the average error of the sensing unit 1 is within ±0.1°, proving that the sensing unit 1 has high measurement accuracy.

[0085] As shownFigure 19 As shown, the relationship between temperature and the ILI of sensing unit 1 is shown. Therefore, the compensation function regarding temperature can be expressed as:

[0086] ;

[0087] where T represents the ambient temperature.

[0088] As Figure 20 shown, first, the sensing unit 1 is cascaded and assembled to measure the bending angle of finger joints and sitting postures. To better fit the sensing unit 1 to the human hand, this application integrates magnets into the nitrile rubber glove, allowing the bending sensors of three cascaded sensing units 1 to be directly attached to the glove. The corresponding sensor nodes are made to bend as close as possible to the proximal interphalangeal joint (PIP), metacarpophalangeal joint (MCP), and wrist joint (Wrist) of the human hand. It can be seen that during the finger bending process, each sensor node can independently measure the angle of each finger joint.

[0089] As Figure 21 shown, the measurement results of three sensor nodes during the process of repeating the finger bending experiment 8 times are shown. It can be seen that the variance deviations corresponding to the three sensor nodes are extremely small, being 1.39 (sensor node 1), 3.89 (sensor node 2), and 3.57 (sensor node 3) respectively, further verifying the accuracy and stability of the bending sensors of three cascaded sensing units 1 when measuring the angles of human joints.

[0090] As Figure 21 shown, the measurement error values for measuring each finger joint using the bending sensors of three cascaded sensing units 1 are shown, being ±1.10°, ±1.85°, and ±1.77° respectively, which proves that this bending sensor has good measurement accuracy.

[0091] It should be noted that monitoring sitting postures is crucial for spinal health, especially during long periods of sitting. To monitor a person's sitting posture, this application assembles seven sensing units 1 to monitor a person's sitting posture. To ensure that each sensing unit 1 fits closely to the body, a special tight-fitting garment embedded with magnets is made, enabling each sensing unit 1 to be easily assembled and fixed on this tight-fitting garment.

[0092] As Figure 23 and Figure 24 shown, to evaluate the monitoring effect on the spine, this application conducts experiments on two common bad sitting postures: neutral spine looking down and kyphotic spine looking down. In addition, this application also uses an advanced optical motion capture system as the ground truth to compare the bending angles measured by each sensor node.

[0093] As Figure 23 shown,Figure 23 i shows the curvature of the spinal segments measured in real time by seven sensor nodes from spinal neutral to spinal neutral with downward gaze and then back to spinal neutral. Figure 23 j shows the curvature of the spinal segments measured in real time by seven sensor nodes from kyphosis to kyphosis with downward gaze and then back to kyphosis.

[0094] As Figure 24 shown, Figure 24 i shows the measurement error values of the flexion angles measured by seven sensor nodes in the state of spinal neutral with downward gaze. Figure 24 j shows the measurement error values of the flexion angles measured by seven sensor nodes in the state of kyphosis with downward gaze. It can be seen that the average measurement error of each sensor node is less than 0.80°.

[0095] According to the above verification experiment, it can be seen the assembly characteristics of the bending sensor proposed in this application, as well as the high measurement accuracy for measuring finger joints and spinal joints. The measurement error of each sensor node is less than 1.85° compared with the actual situation.

[0096] Based on the same inventive concept, as Figure 25 and Figure 26 shown, this application also discloses a preparation method of a bending sensor, and the method includes the following steps:

[0097] Step S1: Prepare an outer cladding. First, insert a support rod and an elastic wire into a mold, then inject a liquid flexible material into the mold, and after curing, take it out of the mold to form the outer cladding.

[0098] As Figure 26 shown in i, the mold 10 includes an upper module 11, a lower module 12, a first clamping and fixing module 13 and a second clamping and fixing module 14. Among them, the upper module 11 is provided with a plurality of liquid injection ports 15 for injecting the liquid flexible material. The first clamping and fixing module 13 and the second clamping and fixing module 14 are both provided with a first fixing hole and a second fixing hole, which are respectively used for inserting the support rod 35 and the elastic wire 33 into the mold 10 correspondingly.

[0099] Before step S1, it is also necessary to assemble the upper module 11, the lower module 12, the first clamping and fixing module 13 and the second clamping and fixing module 14 to obtain the mold 10. Among them, first align the grooves of the upper module 11 and the lower module 12, and then use the first clamping and fixing module 13 and the second clamping and fixing module 14 to respectively snap onto both ends of the aligned upper module 11 and lower module 12, so as to obtain the mold 10.

[0100] As Figure 26As shown in Figures ii - v, in step S1, a support rod 35 and four elastic wires 33 are inserted into the mold 10, and then a liquid flexible material is poured into the mold 10. After the entire assembly is heated and cured, the mold 10 is removed to obtain the outer cladding 31.

[0101] Step S2: Prepare the core layer. First, the support rod is pulled out from the first through - hole of the outer cladding, and then multiple short optical fiber segments are sequentially inserted into the first through - hole of the outer cladding to form the core layer.

[0102] As Figure 26 shown in Figure vi, first, the support rod 35 is pulled out from the first through - hole (not shown in the figure) of the outer cladding 31, and then multiple short optical fiber segments 34 are sequentially inserted into the first through - hole of the outer cladding 31 to form the core layer (not shown in the figure).

[0103] In this embodiment, the first through - hole is located at the center of the cross - section of the outer cladding 31. Four second through - holes (not shown in the figure) are also provided circumferentially around the first through - hole, and the four elastic wires 33 pass through the four second through - holes of the outer cladding 31.

[0104] Step S3: Install the connectors. The first connector and the second connector are respectively installed at both ends of the outer cladding to form a sensing unit.

[0105] As Figure 26 shown in Figures vii - viii, the first connector 2 and the second connector 4 are respectively installed at both ends of the outer cladding 31. Among them, both ends of the four elastic wires 33 are respectively connected to the light - emitting element on the first connector 2 and the photosensitive module on the second connector 4, thereby forming the sensing unit 1.

[0106] Step S4: Connect multiple sensing units end - to - end to obtain a bending sensor.

[0107] Among them, in combination with Figure 1 , the first connector 2 of one sensing unit 1 is connected to the second connector 4 of another sensing unit 1, and the second connector 4 of one sensing unit 1 is connected to the first connector 2 of another sensing unit 1.

[0108] Combined with the specific description of the above-mentioned bending sensor, a single sensing unit 1 integrates a micro-LED 20, a photon chip 40, and multiple short optical fiber segments 34. Importantly, the multiple short optical fiber segments 34 within the sensing unit not only effectively reduce the bending stress but also adjust the ILI to improve the sensitivity. Further, both ends of the sensing unit 1 are equipped with magnetic first connector 2 and second connector 4, allowing for the quick cascading and assembly of multiple sensing units 1 to measure the bending angles at multiple interfaces. At the same time, the sensing unit 1 has good stability, low hysteresis, and high linearity. Its assemblable magnetic structure allows for quick customization and integration into wearable devices and can be used in a series of scenarios for personalized posture monitoring and human-machine interfaces.

[0109] Combined with Figures 20 - 24 , it can be seen that by individually assembling multiple sensing units 1 to obtain the corresponding bending sensor for monitoring the movements of multiple human joints, its versatility and adaptability are highlighted.

[0110] Thus, it can be seen that the present application discloses a bending sensor, including multiple sensing units connected end-to-end. The sensing unit includes a first connector, a sensing body, and a second connector. The first connector and the second connector are respectively located at both ends of the sensing body; the first connector of one sensing unit is used to connect the second connector of another sensing unit, and the second connector of one sensing unit is used to connect the first connector of yet another sensing unit; the sensing body includes an outer cladding layer and a core layer, and the outer cladding layer wraps around the periphery of the core layer; a light-emitting element is provided within the first connector, and the light-emitting element is used to emit a light source. The light source can be conducted within the sensing body, and the light source is conducted from one end of the core layer to the other end of the core layer to obtain the transmitted light; a photosensing module is provided within the second connector, and the photosensing module is used to determine the bending angle of the sensing body based on the light intensity attenuation of the transmitted light relative to the light source. This design emphasizes modularity, high flexibility, and assemblability, and can be customized for different joints while ensuring accurate angle measurement. The present application also discloses a preparation method for the bending sensor. The sensor obtained by this method can achieve quick customization and accurate multi-joint monitoring, solving the limitations of the prior art. Its modular design, low error, and wireless integration highlight the potential for personalized healthcare and human-machine interfaces.

[0111] The above are only the embodiments of the present application and do not limit the patent scope of the present application. Any equivalent structural transformation made using the specification and drawings of the present application, directly or indirectly applied in other related technical fields, shall be equally included within the patent protection scope of the present application.

Claims

1. A bending sensor, characterized in that A plurality of end-to-end connected sensing units are included, wherein the sensing unit includes a first connector, a sensing body and a second connector, wherein the first connector and the second connector are respectively located at two ends of the sensing body; wherein the first connector of a sensing unit is used to connect to the second connector of another sensing unit, and the second connector of a sensing unit is used to connect to the first connector of yet another sensing unit; The sensing body comprises an outer cladding layer and a core layer, wherein the outer cladding layer wraps around the outer periphery of the core layer; A light emitting member is provided in the first connector, and the light emitting member is used to emit a light source, and the light source can be conducted in the sensing body, and the light source is conducted from one end of the fiber core layer to the other end of the fiber core layer to obtain the conducted light; A photosensitive module is disposed in the second connector, and the photosensitive module is used to determine the bending angle of the sensing body according to the attenuation of the light intensity of the transmitted light relative to the light source.

2. The bending sensor according to claim 1, characterized in that, The core layer includes a plurality of short optical fiber segments which are arranged side by side and have the same size and the same spacing distance.

3. The bending sensor according to claim 1, wherein, A plurality of elastic wires are inserted into the outer covering layer for supplying power to the light-emitting element and enabling the photosensitive module to perform data communication.

4. The bending sensor according to claim 1, characterized in that, The connection between the first connector and the second connector is magnetic.

5. The bending sensor according to claim 1, wherein The wavelength of the light source is between 380nm and 780nm.

6. The bending sensor according to claim 1, wherein The length of the sensing unit is less than 10 cm.

7. The bending sensor according to claim 1, characterized in that, The photosensitive module includes a photon chip, and the calculation formula of the bending angle is: ； Among them, represents the bending angle; ; ; represents the light intensity measured by the photon chip in the sensing unit; represents the compensation function for temperature, and , where T represents the ambient temperature.

8. The bending sensor according to claim 7, characterized in that, The bending sensor also includes a wireless front end, which includes a voltage source, a microcontroller and a wireless communication module; The voltage source is used to provide working voltage for the light-emitting element, the photonic chip, the microcontroller and the wireless communication module; The microcontroller communicates with the photonic chips of the plurality of sensing units through an integrated circuit bus and processes data from the photonic chip of each sensing unit; The wireless communication module is used to transmit the processed data to the computer for display.

9. The bending sensor according to claim 7, wherein The first connector includes three groups of contact rings, and the second connector includes three groups of contact points respectively connected to the three groups of contact rings; the three groups of contact rings are respectively the first contact ring, the second contact ring and the third contact ring from the inside to the outside, and the three groups of contact points are respectively the first contact, the second contact and the third contact from the inside to the outside; The first contact ring and the first contact point are voltage common collector contacts, used as a positive power supply for the bending sensor; The second contact ring, the third contact ring, the second contact point and the third contact point are integrated circuit bus contacts for transmitting data of the photonic chip; The outer sides of the first connector and the second connector are both made of metal conductors and are used as negative power supplies for the bending sensor.

10. A preparation method of a bending sensor, characterized in that, The method comprises the following steps: Preparing the outer cladding layer, first inserting the support rod and the elastic wire into a mold, then injecting the liquid flexible material into the mold, and taking it out from the mold after curing to form the outer cladding layer; Prepare the core layer by first pulling the support rod out of the first through hole of the outer cladding, and then inserting a plurality of short optical fiber segments into the first through hole of the outer cladding in sequence to form the core layer; Install connectors, and install a first connector and a second connector at both ends of the outer sheath respectively to form a sensing unit; Connect multiple said sensing units end to end to obtain a bending sensor; wherein, connect the first connector of one sensing unit to the second connector of another sensing unit, and connect the second connector of one sensing unit to the first connector of yet another sensing unit.

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