A wearable gait correction system based on fiber bragg grating

Abstract

The application provides a wearable normal walking action correction system based on fiber grating, and belongs to the field of fiber sensing. The system is composed of a light source module, a plurality of parts composite structure sensing units, a demodulation module, a data processing module, a user terminal module, a power module and an alarm module. The parts composite structure sensing units are composed of carbon fiber composite wearable parts with embedded fiber grating arrays and loose rings with pasted gratings. The demodulation module is composed of a multi-channel grating demodulator. The application provides a novel normal walking action real-time online correction system based on fiber grating sensing components, designs corresponding wearable parts, and solves the problems of traditional normal walking action correction systems, such as complexity, inconvenience to carry and high hysteresis. The composite structure joint angle sensing unit of the application corrects the angle measurement error caused by the change of limb circumference due to muscle stretching and deformation, and the incompatibility of the sensing unit and the limb, and expands the universality for different fat and thin people.

Description

TECHNICAL FIELD

[0001] The present application relates to a wearable normal step action correction system based on fiber grating, belonging to the field of optical fiber sensing. BACKGROUND

[0002] The action points of walking normally are: one foot kicks forward 75 cm, the leg is straightened at the same time, the toes are pressed down to make the soles parallel to the ground, the height is about 25 cm from the ground, and then the leg is changed to fall, and so on. The traditional training method is usually demonstrated by the instructor, and the student's action is observed, guided and corrected. This method is time-consuming and labor-intensive, and when the student trains alone, it is difficult to judge whether the action is standard.

[0003] There are some technical means for these problems, such as patent CN200995050Y developed according to the variable relationship between human height and arm swing height, which sets limits for arm swing and leg kicking range to standardize the action, but can only be used in place, and cannot follow the student to move; patent CN207966159U uses a three-axis acceleration sensor to collect the leg lifting angle and height information of the student, and sends an alarm when the preset height and angle are reached, which belongs to a wearable device, but cannot judge whether the leg is straight and the foot is parallel to the ground. In addition, there are also video information collected by camera equipment for action analysis, but there are problems of limited site and high action recognition lag.

[0004] The present application uses wearable components to measure joint angles and correct normal step actions. The existing wearable devices for measuring joint angles, such as smart gloves and sensing sleeves, have relative movement and gaps with the limbs during joint bending due to muscle contraction and expansion, which cannot always meet the close fit with the limbs, resulting in errors in angle measurement, and the universality is not high for users of different fat and thin body shapes, as described in the document "Flexible wearable wrist joint motion angle sensor" (Journal of Xi'an Jiaotong University, Vol. 52, No. 12, 2018). Therefore, the present application designs a composite structure joint angle sensing unit, which can correct the measurement errors caused by muscle stretching or different fat and thin of users. SUMMARY

[0005] The present application aims to solve the problems of the current normal step correction scheme, such as non-wearable, complex system, poor applicability, etc., and proposes a wearable normal step correction device and system based on fiber grating, which determines whether the action is standard by measuring the angles of each joint of the lower limbs, and reminds the student to correct the action in real time.

[0006] The purpose of the present application is achieved by the light source module, each part composite structure sensing unit, demodulation module, data processing module, user terminal module, alarm module, power module. The power module supplies power to the light source module, demodulation module, data processing module and alarm module through the wire; the data interface is connected between the demodulation module and the data processing module, between the data processing module and the user terminal module, and between the data processing module and the user terminal module to transmit data; the light source module, each part composite structure sensing unit and the demodulation module are connected by a single-mode optical fiber to conduct light signals.

[0007] The present application also includes some structural features:

[0008] 1. The each part composite structure sensing unit consists of a grating sensor for joint bending detection, a grating sensor for temperature compensation, a grating sensor for detecting limb circumference change, and an external member for support. The external member for support includes each part carbon fiber composite wearable part and each part elastic ring belt. The elastic ring belt is composed of two steel wire ropes, two springs and a plastic short plate, which are connected in order of steel wire rope, spring, plastic short plate, spring, steel wire rope, and the two ends of the steel wire rope are connected with the carbon fiber composite wearable part.

[0009] 2. The grating sensor for joint bending measurement and the grating sensor for temperature compensation are connected in series on one optical fiber. The number of gratings of the grating sensor for joint bending measurement at the hip and ankle is 3, and the number of gratings of the grating sensor for joint bending measurement at the knee is 1; the number of gratings of the grating sensor for temperature compensation at each part is 1. The corresponding grating sensor for joint bending measurement and the grating sensor for temperature compensation at each part are sequentially embedded in the carbon fiber composite wearable part of the hip, knee and ankle, and the capillary steel tube is used for protection and packaging of the grating sensor for temperature compensation during embedding.

[0010] 3. The number of gratings of the grating sensor for detecting limb circumference change at each part is 1, which is connected in series on one optical fiber and sequentially pasted on the elastic ring belt of the hip, knee and ankle. After pasting around the steel wire rope, plastic short plate and steel wire rope on the ring belt, it is sequentially extended to the next part, and the optical fiber grating is located on the plastic short plate.

[0011] 4. The demodulation system demodulates the wavelength drift of each grating point , the data processing module obtains the strain of each joint bending measurement grating point which eliminates the influence of temperature according to the wavelength drift, and further calculates the joint bending angle; at the same time, the error correction coefficient is determined according to the wavelength drift of the grating sensor for detecting limb circumference change, and the accurate joint bending angle is obtained. Finally, compared with the preset value of each joint angle. The joint angle preset value is calculated by combining the leg length value input by the user with the standard of normal walking.

[0012] Compared with existing technologies, the beneficial effects of this invention are: 1. This invention proposes a novel real-time online correction system for marching movements based on fiber optic grating sensing components, and designs corresponding wearable components, solving the problems of traditional marching movement correction systems being cumbersome, difficult to carry, and having high latency. 2. This invention designs a composite structure joint angle sensing unit to correct for changes in limb circumference caused by muscle contraction and deformation, and angle measurement errors caused by misalignment between the sensing unit and the limb, and expands its applicability to people of different body types. Attached Figure Description

[0013] Figure 1 This is a diagram of a wearable marching correction system;

[0014] Figure 2 It is a simplified model diagram of the human lower limbs marching.

[0015] Figure 3 This is a schematic diagram of the structure of a wearable hip component;

[0016] Figure 4 This is a schematic diagram of the structure of a wearable knee component;

[0017] Figure 5 This is a schematic diagram of the structure of a wearable ankle component;

[0018] Figure 6 This is a schematic diagram of the adjustable ring structure and its grating arrangement;

[0019] Figure 7 This is a schematic diagram of the knee composite structure sensing unit. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0021] Combination Figures 1-7 The entire system of this invention comprises two large units, namely the left leg and the right leg. Each large unit contains three sensing units, namely a composite sensing unit for the hip, knee, and ankle. The two large units share a set of light source module, demodulation module, and data processing module. The broadband light source, fiber optic coupler, optical switch, demodulator, main processor, and power supply are packaged in a plastic box and secured to the waist with straps. The optical fiber output of the optical switch leads to the sensing units of each part of the left and right large units respectively. When there is a leg raising, knee bending, or foot raising movement, the limb causes the grating of the sensing unit to drift in wavelength. The demodulation module performs wavelength demodulation, and the processor converts the wavelength values ​​of each part into angle values ​​and compares them with preset angle values. When the preset angle is met, a command is issued to control the alarm module to emit a prompt sound to complete the movement correction. At the same time, the optical switch is controlled to select another unit to proceed to the next movement.

[0022] The composite structure sensing unit of each part includes a grating sensor 19 for joint bending detection, a grating sensor 20 for temperature compensation, a grating sensor 21 for detecting the change of the circumference of the limb, and an external member for support. The external member for support includes a carbon fiber composite wearable part 22 of each part and a loose ring belt 15. The carbon fiber composite wearable part is formed by laminating and curing multiple layers of carbon fiber and resin composite prepreg, and its shape can be fixed at the joint. The loose ring belt is composed of two steel wire ropes 16, two springs 17 and a plastic short plate 18, which are connected in the order of steel wire rope, spring, plastic short plate, spring and steel wire rope. The two ends of the steel wire rope are connected to the carbon fiber composite wearable part, so that the ring belt can be wrapped around the limb and tightened.

[0023] The grating sensors for joint bending detection and the sensors for temperature compensation are embedded in the carbon fiber composite wearable part of each part. The number of gratings of the grating sensors for joint bending measurement at the hip and ankle is 3, and the number of gratings at the knee is 1. The number of gratings of the grating sensors for temperature compensation at each part is 1, and the gratings are connected in series on one optical fiber. The corresponding grating sensors for joint bending detection and the sensors for temperature compensation of each part are sequentially embedded in the carbon fiber composite wearable part of the hip, knee and ankle in order, and the temperature compensation grating is packaged with a capillary steel tube. The embedding direction of the gratings is parallel to the direction of the unidirectional prepreg of the upper and lower layers, and parallel to the limb. The wavelength shift caused by the deformation of the gratings driven by the joint bending is linearly related to the strain at the grating points. The bending curvature of each point is obtained from the strain at each point. The distance between adjacent measurement gratings is equal to L, and the bending curvature radii of the two arc segments after bending are represented by the average of the curvature radii of the measurement points at both ends of the gratings, which are 、 , and the bending angles of the two arc segments are , , respectively. The joint bending angle .

[0024] However, due to the difference in body fat of each person, the grating strain caused by the same angle of joint bending is different, which will introduce errors. At the same time, muscle stretching and limb circumference change occur during joint bending, which will cause gaps between the wearable part and the limb, and also cause errors. Therefore, a compensation part, i.e. a loose ring belt with an optical fiber grating, is designed to correct the errors caused by the change of the circumference of the limb.

[0025] The number of gratings of the fiber grating sensor for detecting the circumference change of the limb is one, the grating is pasted on the plastic short plate, and the two ends of the optical fiber are pasted on the steel wire across the spring. The function of the spring is to reduce the strain of the grating, buffer the deformation caused by the stretching of the ring belt, avoid the breakage of the grating, and make the ring belt always close to the limb to adapt to the change of the circumference of the limb. The fiber grating sensors for detecting the circumference change of the limb are connected in series on one optical fiber and are pasted on the loose ring belts of the hip, knee and ankle in turn. The coefficient k is set, which is linearly related to the grating drift amount on the ring belt, that is, linearly related to the fatness of the limb and the stretching degree of the muscle, and the actual bending angle of each joint measured by the composite structure sensing unit is , which realizes the purpose of excluding the influence of the circumference change of the limb.

[0026] The preset angle is converted from the leg length value input by the user terminal, i.e. the keyboard, and the requirement of the marching according to the geometric relationship. The hip angle is , and the ankle angle is , wherein H is the leg length value. In addition, the leg length value is displayed by the LCD display screen, and the keyboard and the LCD display screen are installed outside the waist belt plastic box and are connected with the total processor through the IO port.

[0027] After the total processor calculates the bending angles of each part, the preset angles are compared. When the measured angles of each part meet the preset angles, the total processor sends a command to control the alarm module to send a prompt signal to inform the user that the action is qualified, and at the same time, the optical switch is controlled through the data interface to select the next unit to perform the next step of action correction. In this way, the continuous measurement of the angles of each joint is realized, and then the continuous correction of the marching action is realized.

[0028] The system diagram is shown in Figure 1 The broadband light source 1, the optical fiber coupler 2, the optical switch 12, the demodulator 3, the total processor 4, the buzzer 5 and the power module 8 are packaged in the plastic box 13, and the plastic box is fixed on the waist by means of a bandage. The user terminal module, i.e. the keyboard 6 and the LCD display screen 7, are arranged outside the plastic box and are used to input and display the leg length value respectively. The keyboard 6 and the LCD display screen 7 are connected through the IO port, and the keyboard 6 and the total processor 4 are connected through the IO port. The user first inputs the leg length value on the matrix keyboard 6, the total processor 4 receives and transmits it to the LCD display screen 7 for display, and then converts the leg length value into the preset angles of each part in combination with the marching standard by using the geometric relationship, wherein the marching standard is that one foot kicks forward 75 cm, the leg is straight, the toes are pressed down at the same time, the soles are parallel to the ground, and the height is about 25 cm from the ground. The marching action is simplified as shown in Figure 2 The joint angle conversion method is that the preset angle of the hip is , the preset angle of the ankle is , and the preset angle of the knee is , wherein H is the leg length, and the unit is cm.

[0029] The light emitted by the broadband light source 1 is transmitted via optical fiber to the output of coupler 2, and then via optical fiber at the output end of optical switch 12 to the hip composite structure sensing unit 9, knee composite structure sensing unit 10, and ankle composite structure sensing unit 11. Each composite structure sensing unit includes a grating sensor 19 for joint flexion detection, a grating sensor 20 for temperature compensation, a grating sensor 21 for detecting changes in limb circumference, and external support components. The external support components include wearable carbon fiber composite material components 22 for each part and adjustable straps 15 for each part. The wearable carbon fiber composite material components for each part are as follows: Figure 3 , Figure 4 , Figure 5 As shown, it is made of multi-layer carbon fiber and resin composite prepreg laminated and cured. Its shape ensures fixation at the joint and prevents relative slippage with the limb. The elastic band consists of two steel wire ropes 16, two springs 17, and a plastic short plate 18, connected in series in the order of steel wire rope, spring, plastic short plate, spring, steel wire rope. The steel wire ropes at both ends are connected to the wearable carbon fiber composite material component, so that the band wraps around the limb and tightens it. Its structure is as follows. Figure 6 As shown.

[0030] The grating sensor 19 for joint flexion detection and the sensor 20 for temperature compensation are embedded in the carbon fiber composite wearable components of each location. The hip and ankle grating sensors for joint flexion measurement each have three gratings, while the knee grating sensor has one. The temperature compensation grating sensor for each location also has one grating, and all gratings are connected in series on a single optical fiber. The corresponding grating sensors for joint flexion detection and temperature compensation are sequentially embedded in the hip, knee, and ankle carbon fiber composite wearable components. The grating embedding direction is parallel to the direction of the unidirectional prepreg layers above and below, and parallel to the limb. The temperature compensation grating is protected and encapsulated using a capillary steel tube 14. All optical fiber inlets and outlets are protected with polyimide film to prevent fiber breakage. After the grating of the hip carbon fiber composite wearable component is embedded, it emerges from below and extends to the knee and ankle carbon fiber composite wearable components, with the knee and ankle gratings arranged in the same embedding method. The grating experiences wavelength shift due to joint bending and is also affected by temperature. Demodulator 3 receives the reflected wavelength, demodulates and identifies it, and then the main processor 4 processes the data. The strain magnitude is calculated from the reflected wavelength, thus obtaining the joint bending angle. The relationship between the grating reflected wavelength used for joint bending detection and temperature and strain is expressed as follows: , The coefficient of thermal expansion is... Thermo-optic coefficient, Here, represents the elastic-optical coefficients, and all coefficients are known quantities. The grating used for temperature compensation does not undergo strain, and its reflected wavelength is only affected by temperature. The temperature compensation grating is close to the grating distribution position for joint bending detection, which can be considered as being in the same temperature, so the temperature compensation grating can be used to eliminate the temperature influence. It should be noted that the thermal-optic coefficients and thermal expansion coefficients are different, so the strain of the grating for joint bending detection can be expressed as , and the bending curvature is , where h is the distance between the grating and the neutral axis of the limb. For the hip and ankle wearable components with three joint bending detection gratings, the three measurement points with a spacing distance L form two circular arcs, and the bending curvature radius of each arc is represented by the average of the curvature radii of the two end measurement points. The curvature radii of the two arc segments are denoted as , , and the total joint bending angle is . The knee joint bending detection grating is only one, and it is only necessary to determine whether the wavelength of the knee joint bending detection grating shifts to determine whether the knee is bent.

[0031] However, due to the different body shapes of different people, the grating strain caused by the same angle of joint bending is different, which will introduce errors. At the same time, muscle stretching and limb circumference changes will cause gaps between the wearable component and the limb, which will also cause errors. Therefore, a compensation component, i.e., a stretchable ring band with a fiber grating, is designed to correct the errors caused by the change in the circumference of the limb.

[0032] The number of gratings of the fiber grating sensor for detecting the change in the circumference of the limb is one at each position. The grating is attached to the plastic short plate 18, and the two ends of the optical fiber are attached to the steel wire rope 16 across the spring 17. The structure of the stretchable ring band and the arrangement of the gratings are shown in Figure 6 . The function of the spring is to reduce the strain of the grating and buffer the deformation caused by the stretching of the ring band to avoid the grating from being pulled apart. The elasticity of the spring can also make the ring band always adhere to the limb to adapt to the change in the circumference of the limb. The fiber grating sensors for detecting the change in the circumference of the limb are connected in series on one optical fiber and are attached to the stretchable ring bands at the hip, knee, and ankle in turn.

[0033] Taking the knee composite structure sensing unit as an example, the grating sensor for joint bending detection, the grating sensor for temperature compensation, the grating sensor for detecting the change in the circumference of the limb, and the external member for supporting are shown in Figure 7 . The coefficient k is set, and its size is linearly related to the grating drift amount on the ring band, i.e., linearly related to the body shape and muscle stretching degree of the limb. Using the composite structure sensing unit, the actual bending angles of the joints can be measured as , which can eliminate the influence of muscle expansion and contraction errors, correct the errors caused by the change in the circumference of the limb, and improve the universality of users with different body shapes.

[0034] The wavelength drift ranges of the gratings on the same output fiber from the optical switch do not overlap with each other, the demodulator identifies and distinguishes the gratings in different positions by using the wavelength division multiplexing principle, and distinguishes the gratings on different optical fibers by controlling the optical switch by using the space division multiplexing principle, and the optical switch is controlled by the general processor.

[0035] The general processor compares the bending angles of the positions with the preset angles, and when the measured angles of the positions all meet the preset angles, the general processor sends a command to control the alarm module to send a prompt signal to inform the user that the action is qualified, and simultaneously controls the optical switch to select the next unit through the data interface to perform the next action correction.

[0036] The above settings can measure the joint bending angles in real time, judge whether the action is standard, and make the user know when the action meets the requirements, form muscle memory over a long period of time, realize action correction, and greatly improve the efficiency of gait correction.

[0037] In summary, the present application belongs to the field of optical fiber sensing, and specifically relates to a wearable gait action correction device and system based on fiber gratings. The system is composed of a light source module, a position composite structure sensing unit, a demodulation module, a data processing module, a user terminal module, a power module and an alarm module. The position composite structure sensing unit is composed of a carbon fiber composite wearable part embedded with an array of fiber gratings and a loose ring band with gratings. The demodulation module is composed of a multi-channel grating demodulator. The specific scheme is as follows: the fiber gratings in the joint composite structure sensing unit drift in wavelength with the bending of the joint, the wavelength drift is linearly related to the angle, and the error caused by the change in the circumference of the limbs due to the fatness and muscle stretch of the body can be corrected; the demodulation module identifies the grating reflected wavelength by using space division multiplexing and wavelength division multiplexing, then collects and analyzes it through the back end, converts it into the angle values of the positions by the general processor, and compares it with the preset angles. The preset angles are converted from the leg length value input by the user and the gait standard, and are suitable for users of different heights; if the collected angle values meet the preset angle values, the general processor sends a command to the buzzer to generate a reminder signal to inform the user that the action meets the standard, achieves the purpose of correcting the gait action, and is suitable for users of different heights and weights.

Claims

1. A wearable marching motion correction system based on fiber Bragg gratings, characterized in that: The system comprises a light source module, a composite structure sensing unit, a demodulation module, a data processing module, a user terminal module, an alarm module, and a power module. The composite structure sensing unit comprises a grating sensor for joint bending detection, a grating sensor for temperature compensation, a grating sensor for detecting limb circumference change, and an external support member. The grating sensor for joint bending detection and the grating sensor for temperature compensation are connected in series on an optical fiber. The number of gratings of the grating sensor for joint bending detection at the hip and ankle is 3, and the number of gratings of the grating sensor for joint bending detection at the knee is 1. ； wherein, is the thermal expansion coefficient, is the thermo-optic coefficient, is the elasto-optic coefficient, each of which is a known quantity; and the grating used for temperature compensation does not experience strain and the reflected wavelength is only affected by temperature: ； The number of gratings of the grating sensor for temperature compensation at each part is 1. ； The grating sensor for joint bending detection and the grating sensor for temperature compensation are sequentially embedded in the carbon fiber composite wearable part of the hip, knee, and ankle. ； The relationship between the grating reflection wavelength for joint bending detection and temperature and strain is represented as follows: For the hip and ankle wearable components with three joint bending detection gratings, the three measurement points with a spacing distance of L form two circular arcs, and the bending curvature radius of each circular arc is represented by the average curvature radius of the two end measurement points, and the curvature radii of the two arc segments are respectively denoted as , , and the total joint bending angle is ; and the knee grating for joint bending detection is only one, and it is only necessary to determine whether the knee grating has wavelength drift, that is, whether bending occurs. The grating sensor for detecting the change of the limb circumference is located on the plastic short plate, and a demodulation system demodulates the wavelength drift of each grating point The data processing module obtains the strain of each joint bending measurement grating point which eliminates the temperature influence according to the wavelength drift, and calculates the joint bending angle; meanwhile, the error correction coefficient is determined according to the wavelength drift of the grating sensor for detecting the change of the limb circumference, and the accurate joint bending angle is obtained. 2.The wearable positive step action correction system based on fiber grating according to claim 1, wherein: The strain of the grating for joint bending detection is represented as follows: The bending curvature is represented as follows: where h is the distance between the grating and the neutral axis of the limb. The number of gratings of the grating sensor for detecting limb circumference change at each part is 1, and the gratings are connected in series on an optical fiber. The gratings are sequentially pasted on the hip, knee, and ankle elastic ring belts and then sequentially extended to the next part.

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