Bending sensor and preparation method thereof

Abstract

The present application discloses a bending sensor and its preparation method. The sensor includes multiple end-to-end connected sensing units, each including a first connector, a sensing body, and a second connector, with the first connector and the second connector respectively located at the two ends of the sensing body. 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. The sensing body includes an outer cladding and a core layer, with the outer cladding wrapping around the outer periphery of the core layer. The first connector is provided with a light-emitting element for emitting a light source, which can be transmitted in the sensing body from one end of the core layer to the other end of the core layer to obtain the transmitted light. The second connector is provided with a photosensitive module for determining the bending angle of the sensing body based on the attenuation of the transmitted light relative to the light source. The sensor is modular, highly flexible, and assemblable, ensuring accurate angle measurement.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a bending sensor and a preparation method thereof. Background Art

[0002] Monitoring human joint motion 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 movements of multiple joints to carry out daily activities, from walking and running to grasping objects and performing fine gestures. For example, precise manipulation of the hands involves intricate coordination between the finger joints, wrist joints, and metacarpophalangeal joints, enabling tasks ranging from writing to manipulating delicate tools. Similarly, the spine, as the central axis of the body, exhibits flexibility and stability across its segments, which is essential for maintaining balance and protecting the spinal cord and nerve roots. Therefore, simultaneous and accurate monitoring of multiple human joints is an indispensable technology for clinical diagnosis and treatment, rehabilitation outcome assessment, and sports training analysis.

[0003] Currently, human multi-joint detection relies primarily on two main sensor technologies: camera-based motion capture systems and wearable sensing technologies. Camera-based systems use high-resolution cameras to capture images of human motion and analyze joint positions and trajectories using computer vision algorithms. These systems offer the advantage of non-contact measurement and can capture full-body motion with high accuracy. However, they are limited by environmental factors such as lighting conditions, occlusion issues, and the need for specialized spaces. Furthermore, their high equipment costs and complex installation processes restrict their widespread application. Wearable sensing technologies, on the other hand, are favored for their portability, real-time performance, and environmental adaptability. These technologies primarily include inertial sensors (such as accelerometers and gyroscopes) and flexible sensors based on sensitive materials. Inertial sensors directly measure acceleration and angular velocity and estimate joint angles and positions using algorithms, but their accuracy can be susceptible to noise interference and accumulated errors. Flexible sensors based on sensitive materials offer unique advantages for monitoring joint range of motion due to their excellent compliance and high sensitivity to bending and stretching deformations. However, most existing wearable sensors are designed only for single-joint monitoring, making simultaneous measurement of multiple joints and body parts difficult. More importantly, these sensors generally lack the ability to be flexibly assembled and cannot be adaptively adjusted according to individual differences, number and length of joints, thus limiting their application potential in multi-joint monitoring scenarios. Summary of the Invention

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

[0005] In order to solve the above technical problems, a technical solution adopted in the present application is to provide a bending sensor, comprising a plurality of end-to-end connected sensing units, wherein the sensing unit comprises a first connector, a sensing body and a second connector, and the first connector and the second connector are respectively located at the two 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 comprises an outer cladding and a core layer, and the outer cladding is wrapped around the outer 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, and 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 attenuation of the light intensity of the conducted light relative to the light source.

[0006] Based on the same inventive concept, the present application also provides a method for preparing a bending sensor, which includes the following steps: preparing an outer cladding, first inserting a support rod and an elastic wire into a mold, then injecting a liquid flexible material into the mold, curing it, and then taking it out from the mold to form the outer cladding; preparing a core layer, first pulling the support rod out of the first through hole of the outer cladding, and then inserting multiple short optical fiber segments into the first through hole of the outer cladding in sequence to form the core layer; installing connectors, respectively installing a first connector and a second connector at both ends of the outer cladding to form a sensing unit; connecting multiple 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 another sensing unit.

[0007] The beneficial effects of the present application are as follows: the present application discloses a bending sensor, comprising a plurality of end-to-end connected sensing units, each comprising a first connector, a sensing body, and a second connector, the first connector and the second connector being located at the two ends of the sensing body, respectively; the first connector of a sensing unit being used to connect to the second connector of another sensing unit, and the second connector of a sensing unit being used to connect to the first connector of yet another sensing unit; the sensing body comprising an outer cladding and a core layer, the outer cladding being wrapped around the outer periphery of the core layer; a light-emitting element being provided within the first connector, the light-emitting element being used to emit a light source, the light source being conducted within the sensing body, the light source being conducted from one end of the core layer to the other end of the core layer, thereby acquiring the conducted light; a photosensitive module being provided within the second connector, the photosensitive module being used to determine the bending angle of the sensing body based on the attenuation of the conducted light intensity relative to the light source. The design emphasizes modularity, high flexibility, and assemblability, and can be customized for different joints while ensuring accurate angle measurement. This application also discloses a method for preparing the bending sensor. The sensor prepared by this method can achieve rapid customization and accurate multi-joint monitoring, which solves the limitations of existing technologies. Its modular design, low error and wireless integration highlight the potential of personalized healthcare and human-computer interface. 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 partial cross-sectional schematic diagram of an embodiment of a bending sensor according to the present application;

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

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

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

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

[0014] Figure 7 is a chromatogram when a sensing unit of an embodiment of a bending sensor according to the present application is bent;

[0015] Figure 8 This is a spectrum signal diagram of a sensing unit when it is bent according to an embodiment of a bending sensor of the present application;

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

[0017] Figure 10 This is a graph showing changes in the overall luminous intensity of visible light at each sensor node in an embodiment of a bending sensor according to the present application;

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

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

[0020] Figure 13 1 is a graph showing the experimental results of a bending sensor embodiment of the present application in which a sensing unit is subjected to 1000 stretching cycles at a rate of 15%;

[0021] Figure 14 1 is a diagram showing hysteresis responses of a sensing unit in an embodiment of a bending sensor according to the present application during the first, 500th, and 1000th stretching cycles;

[0022] Figure 15 This is a light intensity attenuation step response diagram of a sensing unit under different time and different strain levels according to an embodiment of a bending sensor of the present application;

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

[0024] Figure 17 This is a test result diagram of the maximum static magnetostriction of a sensing unit using a standard tension sensor according to one embodiment of a bending sensor of the present application;

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

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

[0027] Figure 20 This is a graph showing monitoring results of a finger joint monitoring experiment conducted according to an embodiment of a bending sensor of the present application;

[0028] Figure 21This is a diagram showing measurement results of each sensor node when conducting a finger joint monitoring experiment according to an embodiment of a bending sensor of the present application;

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

[0030] Figure 23 1 is a graph showing monitoring results of a spinal column area monitoring experiment conducted according to another embodiment of a bending sensor of the present application;

[0031] Figure 24 This is a diagram showing the measurement results of the bending angles of various joints during a spinal region monitoring experiment conducted according to an embodiment of a bending sensor of the present application;

[0032] Figure 25 is a flow chart of an embodiment of a method for preparing a bending sensor according to the present application;

[0033] Figure 26 This is a schematic diagram of the physical preparation process of an embodiment of a method for preparing a bending sensor according to the present application. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of this application.

[0035] It should be noted that when an element is referred to as being “fixed on” or “set on” another component, it can be directly on the other component or indirectly set 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 terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply 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 understood as a limitation on this application.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, features specified as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" and "several" mean two or more, unless otherwise 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 efficacy and purpose that can be achieved by this application.

[0039] For the description of this application, the non-limiting 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, and the first connector 2 and the second connector 4 are respectively located at the 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, and the outer cladding 31 is wrapped around the outer 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 passed through the outer covering 31 for supplying power to the light-emitting element and enabling the photosensitive module to perform data communication.

[0042] Combine Figure 3When a single sensing unit 1 is bent, internal stress will appear on both sides of the sensing unit 1. Therefore, the present application uses elastic wires 33 with stress relief capability, and strategically places four elastic wires 33 around the core layer 32 ( Figure 2 The top, bottom, front and back of the core layer 32 shown in the figure can ensure that the sensing unit 3 will not be broken.

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

[0044] It should be noted that the core layer 32 uses PMMA optical fiber, which has the characteristics of high refractive index and low light loss, resulting in negligible attenuation of light intensity during short-distance propagation. Therefore, the sensor experiences insignificant optical bending loss, resulting in reduced sensitivity of the sensing unit. In addition, when the sensor is bent, the mismatch in elastic modulus between the PMMA optical fiber and the elastic outer cladding 31 easily leads to stress concentration within the PMMA optical fiber, increasing the possibility of microcrack formation or fiber breakage. In order to alleviate these challenges, the present 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 improving the macroscopic bending loss rate of the PMMA optical fiber and alleviating internal residual stress.

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

[0046] Furthermore, the first contact ring 21 and the corresponding first contact 42 are voltage common collector (VCC) contacts, serving as the positive power supply for the bend sensor. The second and third contact rings 22 and 23 and the corresponding second and third contacts 42 and 43 are integrated circuit bus (IIC) contacts, used to transmit data from the photosensitive module. The serial data line (SDA) and serial clock line (SCL) are used for data transmission and provide a synchronous clock signal for the photosensitive module, respectively. The outer sides of the first and second connectors 2 and 4 are both made of metal conductors, serving as the negative power supply (GND) for the bend sensor. This design helps reduce the size of the bend sensor. When the first connector 2 and the corresponding second connector 4 are engaged, the contacts are precisely aligned, ensuring the stability of the sensor's electrical performance.

[0047] Furthermore, the connection between the first connector 2 and the second connector 4 adopts a magnetic connection, which can achieve rapid assembly of the bending sensor and facilitate the customization of bending sensors of 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] like Figure 1 As shown, the sensor body 3 is a horizontally placed cylinder. The resulting sensor body 3 is 80 mm long and has a cross-sectional diameter of 4 mm. The outer cladding 31 and the core layer 32 are the same length as the sensor body 3, and the cross-sectional diameter of the core layer 32 is 1.5 mm. Within each core layer 32, the spacing between two adjacent short fiber segments 34 is 0.5 mm. The cross-sectional diameters of the first and second connectors 2 and 4 are identical, both 5 mm. When connected, the total length of the first and second connectors 2 and 4 is 7 mm.

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

[0052] like Figure 5 As shown, the light emitting element adopts a micro LED 20, which 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 380nm and 780nm.

[0053] Furthermore, the photosensitive module includes a photonic chip 40 for converting optical signals into electrical signals. In this embodiment, the photonic chip 40 is integrated on the side where the second connector 4 is connected to the sensor body 3, and can detect the light intensity at the end of the sensor unit 1 (the end where the second connector 4 is installed).

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

[0055] Furthermore, the microcontroller uses an STM32F103RCT6 chip, the voltage source uses an AMS1117 chip, and the wireless communication module uses an NRF2401L chip. The voltage source provides a stable operating voltage for the wireless communication module, the microcontroller, and the sensor unit 1. The microcontroller communicates with the sensor unit nodes (photonic chip 40) via an integrated circuit bus and processes data from each sensor unit node. The processed data is then transmitted to a computer via the wireless communication module for display.

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

[0057] like Figure 5 As shown, the voltage common collector (VCC) and the bend sensor's negative power supply (GND) serve as a power bus, providing operating voltage for the micro-LEDs 20 and photonic chip 40 within each sensing unit 1. The serial data line (SDA) and serial clock line (SCL) form the integrated circuit bus (IIC). Each photonic chip 40 has a unique device tag stored in a specific register. A master device can acquire signals from each sensing unit node via the IIC using a polling read method.

[0058] like Figure 6 As shown, when sensing unit 1 is in a straight configuration, photonic chip 40 can determine the light intensity at the sensor's end. Due to the short length of short fiber segment 34, the light transmission loss within the fiber is negligible. Short fiber segment 34 has a certain gap between each small section, so only the light loss in the gaps needs to be considered. The light attenuation in these gaps can be expressed as follows:

[0059] ;

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

[0061] ;

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

[0063] .

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

[0065] .

[0066] Therefore, it can be clearly seen that the attenuation of the light intensity in the sensing unit 1 is determined by the spacing 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 distance between two adjacent short optical fiber segments 34 increases, which causes a change in the intensity of their output light. Therefore, the bending angle of the sensing unit 1 can be determined based on the change in light intensity attenuation.

[0068] like Figure 7 and Figure 8 As shown, one end of the sensing unit 1 is fixed, and the other end is bent from 0° to 90° in increments of 10°. A bending experiment is performed to obtain a chromatographic coordinate diagram and a 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 The changes in the spectral signal are shown, indicating that the overall intensity of the spectral signal decreases as the bending angle increases.

[0069] Combine Figure 9 Figures (A)-(F) show the normalized spectral distribution of sensor unit 1 at strains of 0%, 3%, 6%, 9%, 12%, and 15%, respectively. Figure (G) shows the relationship between the light intensity attenuation of red, green, and blue light and the strain level of sensor unit 1. Figure (H) shows a comparison of the light intensity attenuation of three visible light sources, red, green, and blue, at strain levels of 0% to 15%, for sensor unit 1. It can be seen that visible light with wavelengths between 490nm and 570nm exhibits a greater attenuation rate.

[0070] like Figure 10As shown in Figure 5, Figures ac show the change in the overall luminous intensity (ILI) of visible light at each sensor node when the cascaded bending sensor is bent. The ILI of the bending sensor can be expressed as:

[0071] ;

[0072] in, Indicates the wavelength of visible light between 490nm and 570nm; represents the spectral function.

[0073] Furthermore, in order to study the bending characteristics of the bending sensor in a multi-node cascade configuration, this application designed three sets of experiments involving the simultaneous bending of a single node, two nodes, and three nodes, respectively. Each set of experiments was repeated five times. The results are shown in Figure 2. Figure 10 As shown in ac. Figure 10 As shown in (a), the repeatability errors of the three sensor nodes are 0.19dB, 0.11dB, and 0.14dB, respectively. The results show that the independent bending of sensor node 3 will not interfere with other nodes. Figure 10 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 0.13dB, 0.18dB, and 0.16dB, respectively; in addition, the signal from sensor node 1 is not affected by crosstalk. Figure 10 As shown in Figure 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 response of each sensor node at the same bending angle is consistent.

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

[0075] like Figure 12 As shown in Figure 2, the correlation between the theoretical attenuation and the strain of the short fiber segment is shown as the bending angle increases. It can be seen that the results of the strain of the short fiber segment and the theoretical attenuation are similar, indicating that there is a linear relationship between the light intensity attenuation and the strain of the short fiber segment.

[0076] Furthermore, the sensor unit 1 was installed on a specific stretching device and subjected to 1000 stretching cycles at a rate of 15%, and the corresponding experimental results were obtained as follows: Figure 13 , which provides a detailed view of the signal over the initial and final 20 cycles. As can be seen, these illustrations show a high degree of consistency, indicating that the bending of the sensing unit 1 is reproducible.

[0077] like Figure 14 As shown in FIG, the hysteresis response characteristics of the sensing unit 1 at the 1st, 500th and 1000th stretching cycles are shown. The hysteresis coefficient E is calculated as follows:

[0078] ;

[0079] in, represents the hysteresis error; represents the attenuation range of 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 sensing unit 1 has a stable ILI response characteristic.

[0080] like Figure 15 and Figure 16 The figure shows the light intensity attenuation step response of the sensor unit 1 at different times corresponding to strains of 2.5%, 5%, 7.5%, 10%, and 12.5% ​​within the stretching range, as well as the light intensity attenuation response of the sensor unit 1 at the same time point corresponding to strains of 2.5%, 5%, 7.5%, 10%, and 12.5%. It can be seen that the larger the stretching range, the greater the corresponding light intensity attenuation.

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

[0082] like Figure 18 As shown, in order to study the relationship between the bending angle and the overall luminous intensity of the sensor unit 1 during bending, the present application also tests the ILI response of the sensor unit 1 when it is bent from 0° to 90°. The relationship between the bending angle and the ILI can be mapped by linear fitting:

[0083] ;

[0084] in, Indicates the bending angle; ; ; represents the light intensity measured by the photonic chip 40 in the sensing unit 1; Represents the compensation function with respect to temperature; coefficient of determination The experimental results show that the average error of the sensing unit 1 is within ±0.1°, which proves that the sensing unit 1 has high measurement accuracy.

[0085] like Figure 19 As shown in FIG, the relationship between temperature and ILI of the sensing unit 1 is shown. Therefore, the compensation function with respect to temperature can be expressed as:

[0086] ;

[0087] Wherein, T represents the ambient temperature.

[0088] like Figure 20 As shown, first, the sensor units 1 are assembled in cascade to measure the bending angles and sitting postures of the finger joints. To better adapt the sensor units 1 to the human hand, this application integrates magnets into a nitrile rubber glove, allowing the bending sensors of the three cascaded sensor units 1 to be directly attached to the glove. The corresponding sensor nodes are then bent as closely as possible to the proximal interphalangeal joint (PIP), metacarpophalangeal joint (MCP), and wrist joint (Wrist). As can be seen, during finger bending, each sensor node can independently measure the angle of each finger joint.

[0089] like Figure 21 Figure 2 shows the measurement results of three sensor nodes during eight repeated finger bending experiments. The variance deviations for the three sensor nodes are extremely small, at 1.39 (sensor node 1), 3.89 (sensor node 2), and 3.57 (sensor node 3), respectively. This further validates the accuracy and stability of the bending sensor, which cascades three sensor units, in measuring human joint angles.

[0090] like Figure 21 As shown, the measurement error values ​​of each finger joint measured using a bending sensor with three cascaded sensing units 1 are ±1.10°, ±1.85° and ±1.77°, respectively, which proves that the bending sensor has good measurement accuracy.

[0091] It should be noted that sitting posture monitoring is crucial for spinal health, especially when sitting for long periods of time. To monitor a person's sitting posture, this application assembles seven sensor units 1 to monitor a person's sitting posture. To ensure that each sensor unit 1 fits tightly to the body, a special tights embedded with magnets is made, allowing each sensor unit 1 to be easily assembled and fixed to the tights.

[0092] like Figure 23 and Figure 24 As shown, to evaluate the monitoring effect on the spine, this application conducted experiments on two common poor sitting postures: neutral spine with downward gaze and kyphotic spine with downward gaze. In addition, this application also used an advanced optical motion capture system as the ground truth to compare the bending angle measured by each sensor node.

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

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

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

[0096] Based on the same inventive concept, Figure 25 and Figure 26 As shown, the present application also discloses a method for preparing a bending sensor, which includes the following steps:

[0097] Step S1: preparing the outer covering layer, first inserting the support rod and the elastic wire into the mold, then injecting the liquid flexible material into the mold, and then taking it out from the mold after curing to form the outer covering layer.

[0098] like Figure 26 As shown in FIG. 1 , mold 10 comprises an upper module 11, a lower module 12, and a first clamping and fixing module 13 and a second clamping and fixing module 14. The upper module 11 is provided with multiple liquid injection ports 15 for injecting liquid flexible material. The first clamping and fixing modules 13 and the second clamping and fixing modules 14 are each provided with a first fixing hole and a second fixing hole for respectively inserting the support rod 35 and the elastic wire 33 into the mold 10.

[0099] Before step S1, the upper module 11, the lower module 12, and the first clamping and fixing module 13 and the second clamping and fixing module 14 need to be assembled to obtain the mold 10. First, the grooves of the upper module 11 and the lower module 12 are aligned, and then the first clamping and fixing module 13 and the second clamping and fixing module 14 are respectively snapped onto the aligned ends of the upper module 11 and the lower module 12 to obtain the mold 10.

[0100] like Figure 26As shown in ii-v, in step S1, a support rod 35 and four elastic wires 33 are inserted into the mold 10, and then the 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 covering 31.

[0101] Step S2: preparing the core layer, 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.

[0102] like Figure 26 As shown in FIG. 6 , the support rod 35 is first pulled out from the first through hole (not shown) of the outer cladding 31 , and then a plurality of short optical fiber segments 34 are sequentially inserted into the first through hole of the outer cladding 31 to form a core layer (not shown).

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

[0104] Step S3: Installing connectors: installing a first connector and a second connector at both ends of the outer covering to form a sensing unit.

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

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

[0107] Among them, combined Figure 1 , connect the first connector 2 of one sensing unit 1 to the second connector 4 of another sensing unit 1 , and connect the second connector 4 of one sensing unit 1 to the first connector 2 of yet another sensing unit 1 .

[0108] In conjunction with the specific description of the above-mentioned bending sensor, a single sensing unit 1 integrates a micro-LED 20, a photonic 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 bending stress, but also adjust ILI to improve sensitivity. Furthermore, both ends of the sensing unit 1 are equipped with a magnetic first connector 2 and a second connector 4, allowing for rapid cascading and assembly of multiple sensing units 1 to measure bending angles at multiple interfaces. At the same time, the sensing unit 1 has good stability, low hysteresis and high linearity, and its assemblable magnetic structure allows for rapid customization and integration into wearable devices, which can be used in a series of scenarios for personalized posture monitoring and human-machine interfaces.

[0109] Combine Figure 20-24 ,It can be seen that the corresponding bending sensor is ,obtained by personalized assembly of multiple sensing units 1 to monitor the ,movement of multiple joints of the human body, highlighting its ,versatility and adaptability.

[0110] As can be seen, the present application discloses a bending sensor comprising multiple end-to-end connected sensing units, each comprising a first connector, a sensing body, and a second connector, the first connector and the second connector being located at opposite ends of the sensing body. The first connector of one sensing unit is configured to connect to the second connector of another sensing unit, and the second connector of one sensing unit is configured to connect to the first connector of yet another sensing unit. The sensing body comprises a cladding and a core layer, with the cladding surrounding the core layer. The first connector is provided with a light-emitting element, configured to emit a light source that is conducted within the sensing body, from one end of the core layer to the other end of the core layer, thereby capturing the conducted light. The second connector is provided with a photosensitive module, configured to determine the bending angle of the sensing body based on the attenuation of the conducted light relative to the light source. The design emphasizes modularity, high flexibility, and assemblability, allowing for customized configurations for different joints while ensuring accurate angle measurement. The present application also discloses a method for fabricating the bending sensor. The sensor fabricated by this method enables rapid customization and accurate multi-joint monitoring, overcoming the limitations of existing technologies. Its modular design, low error, and wireless integration highlight the potential for personalized healthcare and human-machine interfaces.

[0111] The above are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structural transformations made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A bending sensor, characterized in that: The invention comprises a plurality of end-to-end connected sensing units, each comprising 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 one sensing unit is used to connect to the second connector of another sensing unit, and the second connector of one sensing unit is used to connect to the first connector of yet another sensing unit; The sensing body includes an outer cladding layer and a core layer, wherein the outer cladding layer is wrapped around the periphery of the core layer, and the core layer includes a plurality of short optical fiber segments of the same size and the same spacing distance arranged side by side; A light emitting element is provided in the first connector, and the light emitting element 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 core layer to the other end of the core layer to obtain the conducted light; A light sensing module is provided in the second connector, and the light sensing 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; The relationship between the spacing between two adjacent short optical fiber segments in the core layer and the light intensity attenuation is: ； in, represents the light intensity attenuation in the core layer; n represents the total number of gaps between short optical fiber segments in the core layer; represents the absorption coefficient of air; d represents the spacing between two adjacent short optical fiber segments; and e represents the natural logarithm.

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

3. The bending sensor according to claim 1, wherein The connection between the first connector and the second connector is a magnetic connection.

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

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

6. The bending sensor according to claim 1, wherein The photosensitive module includes a photon chip, and the calculation formula of the bending angle is: ； in, represents the bending angle; ; ; represents the light intensity measured by the photonic chip in the sensing unit; represents the compensation function with respect to temperature, and , T represents the ambient temperature.

7. The bending sensor according to claim 6, characterized in that The bending sensor further comprises a wireless front end, wherein the wireless front end comprises a voltage source, a microcontroller and a wireless communication module; The voltage source is used to provide operating 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.

8. The bending sensor according to claim 6, wherein: The first connector includes three groups of contact rings, and the second connector includes three groups of contact points connected to the three groups of contact rings respectively; the three groups of contact rings are, from the inside to the outside, a first contact ring, a second contact ring, and a third contact ring, and the three groups of contact points are, from the inside to the outside, a first contact, a second contact, and a third contact; The first contact ring and the first contact point are voltage common collector contacts, used to serve 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.

9. A method for preparing a bending sensor, characterized in that: The method comprises the following steps: preparing an outer covering layer by first inserting a support rod and an elastic wire into a mold, then injecting a liquid flexible material into the mold, curing the material, and then removing the material from the mold to form the outer covering layer; preparing a core layer by first pulling the support rod out of the first through hole of the outer cladding, and then sequentially inserting a plurality of short optical fiber segments into the first through hole of the outer cladding to form the core layer; Installing connectors, installing a first connector and a second connector at both ends of the outer covering to form a sensing unit; A plurality of the sensing units are connected 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.

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