Optical fiber intensity-modulated plantar pressure sensor system

Abstract

The application provides a fiber intensity modulation type plantar pressure sensor system, which comprises a fiber pressure sensing unit, a wireless transmission system and a lithium battery; the fiber pressure sensing unit comprises a D-shaped grooved fiber sensor and two fiber bending sensors; the D-shaped grooved fiber sensor comprises a bending fiber, the bending fiber comprises a left half fiber and a right half fiber, D-shaped grooves are arranged on the left half fiber and the right half fiber, and the left half fiber and the right half fiber are buckled and installed through the two D-shaped grooves to form a 'Y' type cross structure; the fiber bending sensor comprises a fiber, and the fiber is bent into a 'Y' type cross structure; the lithium battery is connected with the wireless transmission system and the fiber pressure sensing unit; the application has the advantages of simple structure, easy preparation, high sensitivity and wearability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sensors, in particular to a fiber intensity modulation type plantar pressure sensor system. BACKGROUND

[0002] With the development of human medical level, people's demand for health detection management is increasingly strong. Among them, plantar pressure detection is an important part, which affects many of our daily activities. If the plantar pressure is detected, people can prevent or treat many diseases in advance.

[0003] In order to measure the pressure on the plantar surface, various sensing technologies have been integrated into insoles. The sensing technology commonly used in research environments is based on many methods, including resistive, capacitive, inductive, piezoelectric and optical sensing methods based on optical fibers. Optical fiber sensing method is very popular in precise pressure measurement. Compared with electronic sensors, optical fiber sensors have the advantages of small size, light weight, multiplexing, no electromagnetic field interference, electrical isolation and biological compatibility.

[0004] The fiber intensity modulation type plantar pressure sensor is generally made by using the macro-bending loss and micro-bending loss principle of the optical fiber. When the physical quantity acts on the optical fiber, the intensity of the optical signal will change. The change of the intensity of the optical signal can realize the measurement of the physical quantity. If the bending radius of the optical fiber is less than a critical value, the bending loss of the optical fiber will increase sharply to obtain a relatively sensitive macro-bending optical fiber sensor. However, the fiber intensity modulation type plantar pressure sensor has the following defects: first, the structure is complex, which requires complex image processing technology, imaging technology and supporting in-shoe system; second, the manufacturing difficulty is high, which needs to be measured with the help of laboratory harsh conditions; third, the sensitivity is low, and the sensitivity of the prior art cannot meet the demand of precise pressure measurement. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application provides a fiber intensity modulation type plantar pressure sensor system, which is simple in structure and easy to manufacture, and has high sensitivity.

[0006] The present application achieves the above technical purpose by the following technical means.

[0007] A fiber intensity modulation type plantar pressure sensor system, comprising: an optical fiber pressure sensing unit, a wireless transmission system and a lithium battery.

[0008] The optical fiber pressure sensing unit comprises a D-shaped grooved optical fiber sensor and two optical fiber bending sensors, the D-shaped grooved optical fiber sensor comprises a bending optical fiber, the bending optical fiber comprises a left half optical fiber and a right half optical fiber, the left half optical fiber and the right half optical fiber are both provided with a D-shaped groove, the left half optical fiber and the right half optical fiber are installed by buckling two D-shaped grooves to form a 'Y' shaped cross structure, and the optical fiber bending sensor comprises an optical fiber which is bent into a 'Y' shaped cross structure.

[0009] The lithium battery is connected with the wireless transmission system and the optical fiber pressure sensing unit.

[0010] Further, the connection loss Lf at the D-shaped groove is:

[0011]

[0012] Wherein, D is the depth of the D-shaped groove, and L is the length of the D-shaped groove.

[0013] Further, the D-shaped grooved optical fiber sensor is installed at a first sensing position, the first sensing position is located at a toe tip, the two optical fiber bending sensors are respectively installed at a second sensing position and a third sensing position, the second sensing position is located at a sole, and the third sensing position is located at a heel.

[0014] Further, the sensing length of the D-shaped grooved optical fiber sensor and the two optical fiber bending sensors in the optical fiber pressure sensing unit is d1, the sensing width is d w , the sensing thickness is d t , and the following conditions are met: 2mm < d l < 5mm, 1mm < d w < 2mm, 1mm < d t < 1.6mm.

[0015] Further, 200um < D < 500um and 1000um < L < 2000um.

[0016] Further, the optical fiber in the optical fiber pressure sensing unit is a plastic optical fiber.

[0017] Further, the wireless transmission system comprises a laser, a photodiode, a digital power meter and a microcomputer.

[0018] The beneficial effects of the present application are:

[0019] 1) The D-shaped grooved optical fiber sensor in the present application is distributed in a 'Y' shape by D groove inlaying, which can effectively improve the sensing sensitivity, and the inlaying structure can ensure that the structure has good stability.

[0020] 2) The optical fiber in the optical fiber sensor of the present application is plastic optical fiber, which has simple structure, is easy to prepare, has high sensitivity, and is wearable.

[0021] 3) The foot pressure sensor shoe pad scheme of the present application is laid out according to the foot pressure distribution of the human body, different sensors with different sensitivities and pressure detection ranges are combined for detection at different positions, and the foot pressure information in the walking process of the human body can be collected and stored, thereby providing a reliable and effective human motion information sensing scheme for human motion auxiliary equipment. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A sensor distribution diagram of a fiber intensity modulation type foot pressure sensor system of an embodiment of the present application;

[0023] Figure 2 A D-shaped groove fiber sensor schematic diagram of an embodiment of the present application, wherein (a) is a “and” shape structure schematic diagram, and (b) is an extrusion schematic diagram of the D-shaped groove fiber sensor;

[0024] Figure 3 A schematic diagram of a fiber intensity modulation type foot pressure sensor system of an embodiment of the present application;

[0025] Figure 4 A corresponding curve of applied pressure and optical power output of the present application;

[0026] Figure 5 A POF sensor output response curve of the present application under a fixed pressure;

[0027] Figure 6 A fiber light output change graph with temperature of the present application;

[0028] Figure 7 Force conditions of the sensor in an actual gait cycle of the present application, wherein (a) is a third sensing position heel response output power graph; (b) is a third sensing position heel response calculated pressure graph; (c) is a first sensing position toe tip response output power graph; (d) is a first sensing position toe tip response calculated pressure graph; (e) is a second sensing position foot palm response output power graph; and (f) is a second sensing position foot palm response calculated pressure graph.

[0029] Reference signs: 1—first sensing position; 2—second sensing position; 3—third sensing position; 4—D-shaped groove inlay extrusion position; 5—laser; 6—optical fiber pressure sensing unit; 7—photodiode; 8—digital power meter; 9—microcomputer; 10—lithium battery. DETAILED DESCRIPTION

[0030] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] Please see Figures 1 to 3 According to an embodiment of the present invention, a fiber optic intensity modulation type plantar pressure sensor system includes: a fiber optic pressure sensing unit 6, a wireless transmission system, and a lithium battery 10.

[0032] Specifically, the fiber optic pressure sensing unit 6 includes a D-groove fiber optic sensor and two fiber optic bending sensors. Each D-groove fiber optic sensor comprises a bent fiber optic cable, consisting of a left half and a right half. Both the left and right half of the fiber optic cable have D-grooves and are connected via two D-grooves to form an "U"-shaped cross structure. When the left and right half of the fiber optic cable are subjected to pressure and undergo bending deformation, the end faces of the left and right half of the fiber optic cable will experience different pressure bending deformations as the applied pressure changes. This alters the energy coupling between the two fibers. When the fiber optic cable is in a straight state, its bending loss decreases as the deformation recovers. Due to the elasticity of the fiber optic cable, the sensor exhibits high repeatability and stability.

[0033] The fiber optic bending sensor includes a single fiber optic cable bent into an "O"-shaped cross structure.

[0034] Furthermore, in the D-groove fiber optic sensor, the maximum aperture angle of the fiber is β, NA is the numerical aperture, and n h For the refractive index, sinβ = N A / n h The connection loss Lf at the D-groove is:

[0035]

[0036] Where D is the depth of the D-groove, 200μm < D < 600μm. L is the length of the D-groove, 1000μm < L < 2000μm.

[0037] Furthermore, the sensing length of the D-grooved fiber optic sensor and the two fiber optic bend sensors in the fiber optic pressure sensing unit 6 is d. l The sensing width is d w The sensing thickness is d t , satisfying 2mm < dl <5mm, 1mm < d w <2mm, 1mm < d t <1.6mm. The optical fiber in the optical fiber pressure sensing unit 6 is a plastic optical fiber.

[0038] Please refer to Figure 4 In the range of 0N-45N, the sensitivity of the un-grooved optical fiber bending sensor is 0.026mw / N, and the sensitivity of the D-grooved optical fiber sensor is 0.287mw / N. The pressure response range of the un-grooved optical fiber bending sensor is [0N, 1592N], i.e. [0kg, 159kg], and the pressure response range of the D-grooved optical fiber sensor is [0N, 70N], i.e. [0kg, 7kg]. The sensitivity of the D-grooved optical fiber sensor is about 11.03 times higher than that of the un-grooved optical fiber bending sensor. At the same time, the inlaid structure cleverly utilizes the mortise and tenon structure characteristics formed by the grooved structure, and can form a stable inlaid structure without dislocation, deformation and other problems in the motion state, ensuring the sensing sensitivity and efficiency.

[0039] Please refer to Figure 5 The data in Table 1 is obtained.

[0040] Table 1: Comparison of D-grooved sensor and ordinary sensor

[0041]

[0042] With the change of the ambient temperature, the sensor may produce different pressure readings. Please refer to Figure 6 In the temperature range of 25-45℃, the output power and the change of temperature are 0.01345mW / ℃.

[0043] The D-grooved optical fiber sensor is installed at the first sensing position 1, and the first sensing position 1 is located at the toe tip. Two optical fiber bending sensors are respectively installed at the second sensing position 2 and the third sensing position 3, and the second sensing position 2 is located at the instep, and the third sensing position 3 is located at the heel. By fixing the optical fiber sensor on the insole, the overall structural strength of the device is improved, thereby improving the sensing support stability, protecting the subject and preventing the subject from being injured. The present application proposes a combined sensing scheme. The toe tip pressure change range of the first sensing position 1 is small and the sensitivity requirement is high, while the instep of the second sensing position 2 and the heel of the third sensing position 3 have large plantar pressure range. Therefore, the D-grooved optical fiber sensor structure and the ordinary “Y” shaped optical fiber sensor structure are respectively used, so as to realize the purpose of high sensitivity and large range measurement.

[0044] Further, the wireless transmission system comprises a laser 5, a photodiode 7, a digital power meter 8 and a microcomputer 9. The lithium battery 10 is connected with the wireless transmission system and the optical fiber pressure sensing unit 6.

[0045] The working principle of the optical fiber intensity modulation type plantar pressure sensor system according to the embodiment of the present application is as follows:

[0046] The laser 5 sends optical signals to the optical fiber pressure sensing unit 6, and the optical fiber pressure sensing unit 6 collects the position and mechanical data of the human body during the training process, which is used for real-time monitoring and the action made by the subject during the movement, so as to realize the purpose of real-time monitoring of the movement action. The optical signal emitted by the optical fiber pressure sensing unit 6 is converted into an electrical signal by the photodiode 7, and then transmitted to the computer for processing by the digital power meter 8, and an instruction is issued, thereby playing an indicating role for the subject and the researchers; by setting the lithium battery 10, the user can use it outside the laboratory, thereby increasing the portability of the overall device.

[0047] When the human body walks, the pressure will change with the change of gait, which will drive the optical fiber to deform, and the optical fiber intensity modulation type plantar pressure sensor system according to the embodiment of the present application will detect the output optical power to realize the sensing of the human gait pressure. In this embodiment, a subject with an age of 23 years old, a weight of 62 kg, a height of 174 cm, an MBI of 20.5 and no related plantar diseases is used to simulate normal human gait movement by walking back and forth. Please refer to Figure 7 , the pressure of the heel at the moment of heel landing and the moment of plantar pressure is higher, that is, the heel response reaches the peak value in Figs. (a) (b), and the maximum heel pressure is 154N±20N. When the foot is in the standing posture, the body weight is distributed on the whole foot, so that the pressure at the single foot stance time is low and more evenly distributed, that is, the pressure is smoothly decreased in Figs. (a) (b), and the pressure is smoothly increased in Figs. (e) (f). In the late gait, the body weight is transferred to the forefoot during the toe-off time, which results in higher pressure in the area, so that the toe tip in Figs. (c) (d) and the sole in Figs. (5) (6) reach the peak value, which are 35N±5N and 70N±10N, respectively.

[0048] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the scope of the patent of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A fiber optic intensity modulated plantar pressure sensor system, characterized by, It comprises a fiber pressure sensing unit, a wireless transmission system and a lithium battery. The fiber pressure sensing unit comprises a D-shaped grooved fiber sensor and two fiber bending sensors, the D-shaped grooved fiber sensor comprises a bending fiber, the bending fiber comprises a left half fiber and a right half fiber, the left half fiber and the right half fiber are both provided with a D-shaped groove, the left half fiber and the right half fiber are installed by two D-shaped groove buckles to form a "Y" type cross structure; the fiber bending sensor comprises a fiber, the fiber is bent into a "Y" type cross structure; The connection loss Lf at the D-shaped groove is: The lithium battery is connected with the wireless transmission system and the fiber pressure sensing unit; where β is the maximum aperture angle of the optical fiber in the D-shaped slotted fiber optic sensor, D is the depth of the D-shaped slot, and L is the length of the D-shaped slot. The D-shaped grooved fiber sensor is installed at a first sensing position, the first sensing position is located at a toe tip, the two fiber bending sensors are respectively installed at a second sensing position and a third sensing position, the second sensing position is located at a sole, and the third sensing position is located at a heel. 200 μm < D < 500 μm, 1000 μm < L < 2000 μm.

2. The fiber strength modulated plantar pressure sensor system of claim 1, wherein, The sensing length d of the D-shaped grooved fiber sensor and the two fiber bend sensors in the fiber optic pressure sensing unit l , the sensing width d w , the sensing thickness d t , satisfy 2mm < d l < 5mm, 1mm < d w < 2mm, 1mm < d t < 1.6mm.

3. The fiber-optic intensity-modulated plantar pressure sensor system of claim 2, wherein, The fiber in the fiber pressure sensing unit is a plastic fiber.

4. The fiber strength modulated plantar pressure sensor system of claim 1, wherein, The wireless transmission system comprises a laser, a photodiode, a digital power meter and a microcomputer.

5. The fiber strength modulated plantar pressure sensor system of claim 1, wherein, ​

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