Narrow auditory meatus force sensing FBG method and system

Abstract

The invention provides an FBG (Fiber Bragg Grating) method and system for sensing narrow auditory meatus force, and aims to solve the problems that the narrow auditory meatus is high in operation difficulty and difficult in micro-scale sensing, and an FBG sensor is adopted. The system is composed of a simulated auditory meatus cavity, an FBG force sensor, an ATI force comparison sensor, a modem and the like, and integration of the FBG sensor and a narrow auditory meatus is achieved. The FBG sensor has the advantages of being flexible and small in size, the multi-core multi-point grating array design is adopted, and the contact force in the auditory meatus can be accurately sensed. The corresponding relation between FBG output and actual stress is determined through a calibration method, and the problem of detection precision is solved. Based on a Cosseerat rod model, accurate acquisition of contact force information is realized, and accurate and safe force sensing support is provided for auditory meatus injection sampling operation.

Description

Technical Field

[0001] The present invention relates to the technical field of medical treatment, and in particular to an FBG method and system for force sensing in narrow ear canals. Background Art

[0002] In the medical field, especially for delicate operations such as inner ear lymph injection sampling, the operation path is complex and challenging. These operations usually require entering from the external auditory canal, passing through the middle ear, and finally reaching the inner ear. However, the narrow structure of the ear canal and the curved path make control extremely difficult during the injection and inspection process, and micro-scale perception in the ear canal also becomes extremely difficult.

[0003] Traditional rigid camera sensors have significant limitations when dealing with such complex environments. They often face problems such as poor deformation adaptability, small illumination coverage, and inability to directly sense force. These problems not only affect the accuracy of operation, but also increase the risk of damage to ear canal tissue.

[0004] In order to overcome these technical difficulties, fiber Bragg grating (FBG) sensors have gradually attracted attention due to their unique advantages. FBG sensors have the characteristics of small size, high sensitivity, immunity to electromagnetic interference, and good biocompatibility, and can provide continuum information in real time. These characteristics make FBG sensors have great application potential in narrow and complex ear canal environments.

[0005] However, it is not easy to apply FBG sensors to narrow ear canals for force sensing. Traditional FBG sensors are often difficult to enter the ear canal and accurately sense contact force due to their large size or lack of flexibility. In addition, how to ensure the stability and reliability of FBG sensors in the ear canal, and how to accurately calibrate and verify their force sensing accuracy are also technical challenges that need to be solved urgently.

[0006] Therefore, it is necessary to propose a new technical solution to improve the above technical problems. Summary of the invention

[0007] In view of the defects in the prior art, the object of the present invention is to provide a FBG method and system for narrow ear canal force sensing.

[0008] According to the present invention, a FBG system for force sensing of narrow ear canals includes: a data processing and output terminal, a modem, an optical fiber fixing device, an FBG optical fiber, a slide rail, a mobile platform, an ATI six-axis force sensor, a 3D camera and an ATI demodulator;

[0009] The data processing and output ends are respectively connected to a modem, an ATI demodulator and a 3D camera; the modem is connected to an optical fiber fixture; an FBG optical fiber is passed through the optical fiber fixture, and the optical fiber fixture is installed on a slide rail; the mobile platform is installed on the slide rail, an ATI six-axis force sensor is installed on the mobile platform, and the ATI six-axis force sensor is connected to the ATI demodulator.

[0010] Preferably, the modem is used to receive wavelength information on the FBG optical fiber and convert it into information of strain change.

[0011] Preferably, a sensing unit is engraved on the FBG optical fiber for sensing the contact force in the ear canal.

[0012] Preferably, the slide rail and the moving platform are used to generate axial or radial forces.

[0013] Preferably, the ATI six-axis force sensor is fixed on the slide rail and the moving platform to measure the standard value of the contact force.

[0014] Preferably, the 3D camera is arranged on the side of the FBG optical fiber, the guide wire twister and the ATI six-axis force sensor to capture the relative position between the FBG optical fiber and the ATI force sensor to obtain the standard value of the position and direction angle of the contact force.

[0015] The present invention also provides a FBG method for narrow ear canal force sensing, the method using the FBG system for narrow ear canal force sensing as described above, the method comprising the following steps:

[0016] Step S1: using a fiber Bragg grating (FBG) sensor as a flexible sensing unit, three-dimensionally bending according to the shape of the ear canal, and sensing force;

[0017] Step S2: controlling the influence of temperature change on the fiber Bragg grating (FBG) sensor, so that the fiber Bragg grating (FBG) sensor array has the ability to measure the contact force in a narrow natural cavity;

[0018] Step S3: receiving wavelength information on the FBG optical fiber through a modem and converting it into strain change information;

[0019] Step S4: The data processing and output end reads the strain change information processed by the modem, and performs subsequent strain-force information processing to obtain the result of FBG force sensing, that is, the size, direction and position of the contact force.

[0020] Preferably, the fiber Bragg grating (FBG) sensor comprises:

[0021] Multi-core fiber MCF: contains multiple independent cores, each of which is engraved with a Bragg grating FBG to sense strain changes;

[0022] Sensor head: Made of metal or ceramic, with PTFE coated on the surface to conduct force;

[0023] Elastic tube: Made of highly elastic polymer, bonded to the surface of the first grating area, used to enhance the strain sensing capability of the fiber Bragg grating FBG sensor;

[0024] Tube body: Made of metal or braided tube, used to encapsulate the optical fiber and allow it to bend freely;

[0025] Optical fiber connector: used to connect FBG optical fiber and modem;

[0026] Adhesive layer: used to connect the sensor head, elastic tube, tube body and multi-core optical fiber MCF into one.

[0027] Preferably, the sensor head end transmits the force to the elastic tube; the bonding layer includes a first bonding layer and a second bonding layer; a first small hole is radially opened at the sensor head end, and glue is poured into the first small hole to form a first bonding layer, thereby connecting the sensor head end with the front end of the multi-core optical fiber MCF as a whole.

[0028] Preferably, the elastic tube detects the axial force and radial force exerted on the sensor head end; a second small hole is opened radially in the tube body, and glue is poured into the second small hole to form a second bonding layer to connect the tube body and the multi-core optical fiber MCF as a whole.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The FBG sensor of the present invention has high sensitivity and can sense the contact force changes in the ear canal in real time and accurately. By controlling the influence of temperature changes on the FBG grating, the sensor can accurately reflect the changes in external strain, thereby accurately measuring the contact force in the narrow natural cavity. The FBG force sensing calibration method ensures the corresponding relationship between the sensor output and the actual force conditions. The calibration and calibration are performed by the ATI six-dimensional force sensor and 3D camera, which significantly improves the measurement accuracy.

[0031] 2. Considering the narrow and curved characteristics of the ear canal, the present invention designs a flexible FBG sensor; the sensor is composed of a multi-core multi-point grating array, has flexible variability and small size, can smoothly enter the ear canal, and undergo complex three-dimensional bending along with the shape of the ear canal, thus ensuring the stability and reliability of the sensor;

[0032] 3. The FBG sensor material of the present invention has good biocompatibility, is harmless to human tissue, and is suitable for operations such as ear canal injection sampling in the medical field; this feature ensures the safety of the operation process and the comfort of the patient.

[0033] 4. The FBG sensor of the present invention has the characteristics of strong anti-interference, is not affected by the electromagnetic environment, can work stably in complex medical environments, and provides reliable technical support for medical operations; it has multiple force sensing points, and can simultaneously sense the contact force between the sensor head and the eardrum and the contact force between the sensor and the ear canal in the path; this multi-point sensing mechanism helps to avoid damage to the ear canal tissue due to excessive operating force during the diagnosis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0035] Figure 1 It is a schematic diagram of ear canal detection of the present invention;

[0036] Figure 2 It is a schematic diagram of the ear canal FBG force sensing system of the present invention;

[0037] Figure 3 It is a cross-sectional view of a multi-core optical fiber FBG of the present invention;

[0038] Figure 4 This is a schematic diagram of the multi-core optical fiber FBG sensing area of ​​the present invention;

[0039] Figure 5 It is a schematic diagram of the FBG force sensing sensor of the present invention;

[0040] Figure 6 It is a schematic cross-sectional diagram of the FBG force sensing sensor and the ear canal hole of the present invention;

[0041] Figure 7 It is a schematic diagram of the FBG force sensor calibration device of the present invention;

[0042] Figure 8 It is a schematic diagram of the force application module of the present invention;

[0043] Fig. 9 is a cross-sectional view of the clamp (a, b) of the present invention;

[0044] Fig.10 It is a schematic diagram of the clamping head structure of the clamp of the present invention;

[0045] Fig.11 It is a partial cross-sectional view of the FBG force sensor calibration device of the present invention;

[0046] Fig.12This is a flow chart of the calibration of the FBG force sensor of the present invention;

[0047] Fig.13 It is the logic block diagram of the natural cavity FBG force calibration of the present invention;

[0048] Fig.14 This is a logic block diagram of the natural cavity FBG force sensing detection of the present invention;

[0049] Fig.15 This is a schematic diagram of the FBG sensor array of the present invention uniformly distributed at 120° around the circumference. DETAILED DESCRIPTION

[0050] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0051] Embodiment 1:

[0052] According to the present invention, a FBG system for force sensing in a narrow ear canal comprises: a data processing and output end, a modem, an optical fiber fixing device, an FBG optical fiber, a slide rail, a mobile platform, an ATI six-axis force sensor, a 3D camera and an ATI demodulator; the data processing and output end are respectively connected to the modem, the ATI demodulator and the 3D camera; the modem is connected to the optical fiber fixing device; the optical fiber fixing device is provided with an FBG optical fiber, and the optical fiber fixing device is installed on the slide rail; the mobile platform is installed on the slide rail, the ATI six-axis force sensor is installed on the mobile platform, and the ATI six-axis force sensor is connected to the ATI demodulator.

[0053] The modem is used to receive the wavelength information on the FBG optical fiber and convert it into information on strain changes. The FBG optical fiber is engraved with a sensing unit to sense the contact force in the ear canal. The slide rail and the mobile platform are used to generate axial or radial forces. The ATI six-axis force sensor is fixed on the slide rail and the mobile platform to determine the standard value of the contact force. The 3D camera is arranged on the side of the FBG optical fiber, the guide wire twister and the ATI six-axis force sensor to capture the relative position between the FBG optical fiber and the ATI force sensor to obtain the standard value of the position and direction angle of the contact force.

[0054] The present invention also provides a FBG method for narrow ear canal force sensing, the method using the FBG system for narrow ear canal force sensing as described above, the method comprising the following steps:

[0055] Step S1: using a fiber Bragg grating (FBG) sensor as a flexible sensing unit, three-dimensionally bending according to the shape of the ear canal, and sensing force;

[0056] Step S2: controlling the influence of temperature change on the fiber Bragg grating (FBG) sensor, so that the fiber Bragg grating (FBG) sensor array has the ability to measure the contact force in a narrow natural cavity;

[0057] Step S3: receiving wavelength information on the FBG optical fiber through a modem and converting it into strain change information;

[0058] Step S4: The data processing and output end reads the strain change information processed by the modem, and performs subsequent strain-force information processing to obtain the result of FBG force sensing, that is, the size, direction and position of the contact force.

[0059] Fiber Bragg Grating (FBG) sensors include:

[0060] Multi-core fiber MCF: contains multiple independent cores, each of which is engraved with a Bragg grating FBG to sense strain changes;

[0061] Sensor head: Made of metal or ceramic, with PTFE coated on the surface to conduct force;

[0062] Elastic tube: Made of highly elastic polymer, bonded to the surface of the first grating area, used to enhance the strain sensing capability of the fiber Bragg grating FBG sensor;

[0063] Tube body: Made of metal or braided tube, used to encapsulate the optical fiber and allow it to bend freely;

[0064] Optical fiber connector: used to connect FBG optical fiber and modem;

[0065] Adhesive layer: used to connect the sensor head, elastic tube, tube body and multi-core optical fiber MCF into one.

[0066] The sensor head end transmits the force to the elastic tube; the adhesive layer includes a first adhesive layer and a second adhesive layer; a first small hole is opened in the radial direction of the sensor head end, and glue is poured into the first small hole to form a first adhesive layer, connecting the sensor head end and the front end of the multi-core optical fiber MCF as a whole. The elastic tube detects the axial force and radial force on the sensor head end; a second small hole is opened in the radial direction of the tube body, and glue is poured into the second small hole to form a second adhesive layer, connecting the tube body and the multi-core optical fiber MCF as a whole.

[0067] Embodiment 2:

[0068] The present invention proposes a method and system for force sensing in narrow ear canals based on FBG. The system realizes accurate force sensing in narrow ear canals by designing a flexible and small-sized FBG force sensing sensor, combined with advanced calibration methods and data processing technology. This not only improves the accuracy and safety of operations such as ear canal injection sampling, but also provides new ideas and methods for the development of related medical technologies.

[0069] The natural cavity FBG force sensing system consists of a simulated ear canal cavity, FBG force sensor, ATI force comparison sensor, and modem, etc. It solves the problem of integrating FBG sensor with narrow ear canal.

[0070] The FBG sensor includes a multi-core multi-point grating array, which is characterized by flexibility, small size, and the ability to enter narrow ear canals, solving the problem that general FBG sensors cannot enter narrow natural cavities for force perception.

[0071] The FBG force sensing calibration method establishes the corresponding relationship between the output of the FBG sensor and the actual force conditions, solving the problem of FBG force sensing detection accuracy verification.

[0072] Based on the equilibrium equation and constitutive equation of the Cosserat rod model, the contact force perception information of the natural cavity is acquired.

[0073] 1. Invented the narrow ear canal FBG force sensing system

[0074] The system consists of an ear canal simulation cavity, an FBG force sensor, a detection accuracy comparison sensor ATI, and a modem, etc. It solves the problem of integrating the FBG sensor with the narrow ear canal cavity.

[0075] Natural cavity FBG force sensing system Figure 1 and Figure 2As shown. The system mainly consists of 1-data processing and output end, 2-modulator, 3-fiber fixture, 4-FBG fiber, 5-slide rail, 6-mobile platform, 7-ATI sensor, 8-3D camera, 9-ATI demodulator. The sensing unit is engraved in 4-FBG fiber. FBG grating has a strong reflection effect only on wavelengths within a certain narrow bandwidth, and there is a linear mathematical relationship between the reflection center wavelength and the external strain change and temperature change. The reflection center wavelength is also called the Bragg center wavelength. Controlling the influence of temperature change on FBG grating enables the FBG sensor array to measure the contact force in a narrow natural cavity. 3-modulator receives the wavelength information from 4-FBG fiber through the adapter on 4-FBG fiber and converts it into strain change information. 1-data processing and output end reads the strain change information processed by 3-modulator through 2-data transmission line, and performs subsequent strain-force information processing to obtain the result of FBG force perception, that is, the magnitude, direction and position of the contact force.

[0076] The base of the wire twister is fixed on the force measuring surface of the 6-ATI six-axis force sensor. The end of the 4-FBG optical fiber is inserted into the wire twister and fixed by the wire twister, and is indirectly connected to the 6-ATI six-axis force sensor. The 5-3D camera is arranged on the side of the 4-FBG optical fiber, the wire twister and the 6-ATI six-axis force sensor, and is used to shoot the relative position between the 4-FBG optical fiber and the 6-ATI six-axis force sensor. The 6-ATI six-axis force sensor is fixed on the 7-slide rail and the moving slide. The moving slide can move axially (x-axis) or radially (y-axis) relative to the FBG optical fiber, thereby generating axial or radial forces on the FBG sensor. Under the action of the contact force, the Bragg center wavelength of the FBG sensor changes, and the modem receives the change in the Bragg center wavelength and transmits it to the 1-data processing and output end to calculate and output the measured value of force perception. The force value result measured by the 6-ATI six-axis force sensor is used as the standard value of the contact force. 5-3D camera takes images of FBG fiber and ATI force sensor. From the images obtained by 3D camera, the position of contact force on FBG fiber and the standard value of contact force angle can be obtained. The measured force value is compared and calibrated with the standard value to evaluate the force sensing accuracy of FBG sensor.

[0077] The FBG sensor calibrated for force sensing can be used for force sensing in the natural cavities of the human body. Many natural cavities are narrow and tortuous. When the 4-FBG optical fiber contacts the tissue in the natural cavity (such as the ear canal), the Bragg center wavelength of the FBG grating at the corresponding position shifts. After 3-modulation and demodulation, and 1-data processing and output end processing, the force sensing results, such as the location of the contact, the magnitude and direction of the force generated by the contact, can be output to the operator to provide contact force information, thereby avoiding large collisions that cause tissue damage.

[0078] 2. Invention of FBG force sensing sensor

[0079] The FBG sensor includes a multi-core multi-point grating array, which is characterized by flexibility, small size, and the ability to enter narrow ear canals, thereby solving the problem that general FBG sensors cannot enter narrow natural cavities for force perception.

[0080] Multi-core fiber (MCF) is a new type of optical fiber with multiple independent cores in a common cladding region. Each core is engraved with one or more Bragg gratings (FBGs). The Bragg wavelength reflected by the latter is related to the ambient temperature and strain, and has typical application prospects in the field of force sensing. Based on FBG multi-core optical fiber, the present invention designs a set of FBG force sensing sensors for the narrow space of the ear canal. The sensors are characterized by small size, the ability to enter narrow natural cavities of the human body such as the ear canal, and several force sensing points. They can measure the contact force between the sensor head and the eardrum, and can also sense the contact force between the sensor and the ear canal in the path, to avoid excessive operating force during the diagnosis process that may damage the ear canal tissue. Figure 3 As shown, the FBG force sensing sensor of the present invention adopts a 4-core optical fiber (outer diameter: 0.1-0.4 mm), including a cladding region and 4 independent cores, wherein core 4 is located at the MCF axis and is not affected by bending strain, and its FBG detection quantity can be used for temperature compensation; cores 1, 2, and 3 are distributed along the axis circumference, Δθ 12 =Δθ 23 = 1200. In the axial direction, N gratings (such as 7-1, 7-2, 7-3) are engraved at the same position of each fiber core of the MCF. The distance between the first grating and the top is a (about 1 to 5 mm), the length of each grating is b (about 1 to 3 mm), and the grating interval is c (about 1 to 5 mm). Figure 4 shown.

[0081] like Figure 5As shown in the figure, the FBG force sensing sensor of the present invention is composed of a sensor head end (1), an elastic tube (2), a tube body (3), an optical fiber connector (4), a first adhesive layer (5), a second adhesive layer (6), an MCF (7), etc. The sensor head end (1) is made of metal or ceramic, and the surface is coated with PTFE to reduce the friction coefficient; it has a relatively large stiffness, and when a force is applied to the head end, it can be transmitted to the subsequent elastic tube (2); a small hole is radially opened on it, and glue can be poured through the small hole to form the first adhesive layer (5), connecting the sensor head end (1) and the front end of the MCF (7) into one body. The elastic tube (2) is made of a highly elastic polymer, or can be made by cutting a metal tube into a spring tube, and it is bonded to the surface of the first grating area (7-1). The strain of the grating area (7-1) will be mainly determined by the Young's modulus and Poisson's ratio of the polymer, thereby enhancing the strain sensing ability of the FBG and being responsible for detecting the axial force and radial force received by the sensor head end (1). The tube body (3) is made of metal (such as a nickel-titanium alloy tube) or a braided tube, and can be freely bent. A small hole is also radially opened on it, and glue can be poured through the small hole to form the second adhesive layer (6), connecting the tube body (3) and the MCF (7) into one body. The axial stiffness of the tube body (3) is relatively large and much greater than the bending stiffness. Therefore, the second grating area (7-2) and the third grating area (7-3) encapsulated inside are not sensitive to the axial force, and it can be considered that their detection is not affected by the axial external force. Each FBG (7-1, 7-2, 7-3) detects the bending shape parameters of the sensor, and calculates the contact force of the ear canal on the sensor based on the Cosserat rod model. The calculation principle is detailed in Section 4.

[0082] As Figure 6 shown, the outer diameter of the FBG force sensing sensor of the present invention is d, about 0.4 - 2 mm (d = 0.8 mm can be adopted in the embodiment), and the minimum inner diameter of the ear canal is D. The design requirement is d < D, so that the FBG force sensing sensor can smoothly enter the ear canal to reach the target tissue. During the movement of the FBG force sensing sensor, it contacts the wall of the ear canal, and can sense the contact force with the ear canal at multiple points.

[0083] Three, an FBG force sensing calibration method is invented

[0084] The corresponding relationship (calibration) between the output of the FBG sensor and the actual force situation is established, solving the problem of verifying the detection accuracy of the FBG force sensing.

[0085] In order to establish the corresponding relationship between the output of the FBG sensor and the actual force situation, it is necessary to calibrate the FBG sensor using a standard force sensor. In view of this, the present invention designs a set of force calibration devices for the FBG sensor based on the ATI force sensor. As Figure 7As shown, the FBG force calibration device is composed of a base (1), a force application module (2), an optical fiber clamping module a (3), an optical fiber clamping module b (4), a force detection module (5) and an FBG force sensing system (6).

[0086] The base (1) provides fixed support for the entire device and serves as an installation reference.

[0087] The force application module (2) is mounted on the base (2) and its function is to clamp the grating-free area on one side of the FBG sensor and apply force to the force sensing grating. The structure of the force application module (2) is as follows: Figure 8 As shown, it consists of an xy-axis slide (2-1), a mounting seat (2-2), an ATI six-dimensional force sensor (2-3), a twister bracket a (2-4), a limit column (2-5) (see Fig.10 ), clamp a (2-6) and positioning pins. The structure of the clamp a (2-6) is as follows: Fig. 9 As shown, it is composed of a clamp bracket (2-6-1), a clamp knob (2-6-2), a clamp stop pin (2-6-3) and a clamp chuck (2-6-4). The clamp bracket (2-6-1) and the clamp knob (2-6-2) are connected by threads and can move relative to each other forward and backward by rotation; the clamp stop pin (2-6-3) is bonded and fixed in the small hole of the clamp knob (2-6-2), and its head end extends into the groove of the clamp bracket (2-6-1), thereby preventing the clamp knob (2-6-2) from falling off when rotating; the clamp chuck (2-6-4) is bonded in the inner hole of the clamp bracket (2-6-1), and its center is a cavity, which allows the optical fiber to pass through in a free state. The front end of the chuck has several coaxial spring structures evenly arranged along the circumference, see for details. Fig.10 When the clamp knob (2-6-2) is tightened, the inner side of the knob presses against the spring of the clamp chuck (2-6-4), exerting a force toward the axis. The spring will bend slightly inward under the action of the torque, thereby clamping the optical fiber.

[0088] The ATI six-dimensional force sensor (2-3) includes a fixed end (2-3-1), a measuring end (2-3-2) and a signal line (2-3-3). When the first two show a relative motion trend, the force between them can be detected. In the force action module, the xy-axis slide (2-1), the mounting seat (2-2) and the fixed end (2-3-1) of the ATI six-dimensional force sensor are connected and fixed in sequence by screws as shown in the figure. The measuring end (2-3-2) of the ATI six-dimensional force sensor and the twister bracket a (2-4) are connected and fixed by screws, and the adjacent parts are fixed by positioning pins to ensure the installation accuracy. The limit column (2-5) is fixed to the center of the inner hole of the twister bracket a (2-4) by threaded connection, and the clamp a (2-6) is installed in the inner hole of the twister bracket a (2-4) by interference fit. The clamp a (2-6), the twister bracket a (2-4) and the limit column (2-5) are all coaxial with the optical fiber (7), and the optical fiber axis is defined as the x-axis. One side area of ​​the force sensing grating of the FBG sensor passes through the clamp a (2-6) to the end face of the limit column (2-5), thereby controlling the insertion length of the optical fiber; the clamp a knob (2-6-2) can be rotated to clamp (or loosen) the optical fiber. After assembly, the xy-axis slide table (2-1), the mounting seat (2-2) and the ATI six-dimensional force sensor fixed end (2-3-1) are connected as a whole; the optical fiber (7), the clamp a (2-6), the twister bracket a (2-4) and the ATI six-dimensional force sensor measuring end (2-3-2) are connected as a whole. Rotating the x-axis knob (2-1-1) and the y-axis knob (2-1-2) of the xy-axis slide table (2-1) can cause the slide to move horizontally along the x / y direction or generate a relative motion trend, and the force applied to the x / y-axis knob is transmitted to the fixed end (2-3-1) of the ATI six-dimensional force sensor; and the right side of the force sensing grating is clamped and fixed by the optical fiber clamping modules a (3) and b (4), so that the same relative motion trend along the x / y direction is generated between the fixed end (2-3-1) and the measuring end (2-3-2) of the ATI six-dimensional force sensor (2-3), thereby applying the force required for calibration to the force sensing grating and being detected by the ATI six-dimensional force sensor (2-3).

[0089] The optical fiber clamping modules a (3) and b (4) are installed on the base. The two modules have the same structure. Each module includes a fixed bracket (3-1), a clamp b (3-2), a twister bracket b (3-3) and a positioning pin, etc. The structure is as follows: Fig.11As shown. The base (1), the fixed bracket (3-1) and the twister bracket b (3-3) are connected and fixed by screws, and the positioning pins are used to ensure the installation accuracy. The clamp b (3-2) and the twister bracket b (3-3) are connected by interference fit. The optical fiber passes through the optical fiber clamping module (3) and b (4), wherein the optical fiber clamping module a (3) is clamped on the right side of the force sensing grating (7-1) of the FBG sensor, and the optical fiber clamping module b (4) clamps the middle part of the FBG sensor to ensure that the optical fiber is straight and avoid external force from interfering with the force sensing grating.

[0090] The force detection module (5) is composed of an ATI six-dimensional force sensor (2-3), an ATI sensor modulation module (5-1), a data transmission line (5-2), a computer and ATI measurement software (5-3), etc., and its structure is as follows: Figure 6 As shown. The signal line (2-3-3) of the ATI six-dimensional force sensor is connected to the ATI sensor modulation module (5-1), which is connected to the computer via the data transmission line (5-2). When the slider of the force application module (2) moves relatively along the x / y direction, the ATI six-dimensional force sensor (2-3) measures the actual force of the FBG force sensing grating and converts it into an electrical signal and transmits it to the ATI sensor modulation module for signal demodulation, and then transmits it to the computer for data processing to obtain the force value.

[0091] The FBG force sensing system (6) is composed of an FBG sensor (7), an optical fiber modem (6-1), a data transmission line (6-2), a computer and FBG measurement software (6-3). The FBG sensor is connected to the optical fiber modem through an optical fiber connector, and the latter is connected to the computer through a data transmission line. Under the force of the ATI six-dimensional force sensor, the reflected Bragg wavelength of the force sensing grating of the FBG sensor is shifted, and the reflected wave is demodulated by the optical fiber modem and then transmitted to the computer for data processing, thereby obtaining the measured force value of the FBG sensor. The measured value of the ATI six-dimensional force sensor is compared with the measured value of the FBG sensor one by one to realize the calibration of the FBG sensor.

[0092] The specific calibration method of FBG force sensor is as follows: Fig.12 As shown:

[0093] Calibration preparation: Figure 7 As shown, the components of the calibration device are connected, the clamps clamp the optical fibers, and the computer ATI measurement software and FBG measurement software are started.

[0094] Set the initial value: Rotate the x / y axis knob of the xy axis slide to adjust its position so that the optical fiber is straight and the ATI sensor is coaxial with the optical fiber. At this time, the ATI sensor force value is 0, and the wavelength value of each FBG grating is recorded as its measurement benchmark.

[0095] Axial force measurement: Rotate the x-axis knob of the xy-axis slide to apply pure axial tension / compression to the force sensing grating on the optical fiber, and record the ATI measurement value and FBG measurement value.

[0096] Radial force measurement: Loosen clamp a, and the front end of the optical fiber is located in the inner cavity of clamp a; rotate the y-axis knob of the xy-axis slide to apply radial force to the force sensing grating on the optical fiber, and record the ATI measurement value and the FBG measurement value.

[0097] FBG-ATI force value comparison: Compare the relationship between multiple groups of ATI measurement values ​​and FBG measurement values ​​to complete the calibration of the FBG force sensor.

[0098] Based on the above force detection module, a detection method is proposed for the ability of FBG sensors to perceive force information, that is, to evaluate the accuracy of FBG sensors in detecting the size, direction and location of contact force. Fig.13 As shown in the figure, under the action of contact force, the Bragg center wavelength of the FBG sensor changes, the change of the Bragg center wavelength is received by the modem, transmitted to the data processing and output end, and processed as the contact force and the location where the contact force occurs s j , as the measured value of force perception. According to Newton's third law, equal and opposite contact forces will be generated on the ATI force sensor, and the force value measured by the ATI force sensor is used as the magnitude of the contact force. The 3D camera takes images of the FBG fiber and the ATI force sensor. From the images obtained by the 3D camera, the position s where the contact force is generated on the FBG fiber can be obtained. i The standard value of the contact force and the direction angle θ i Standard value of . Measured value s j With standard value s i ,θ i Comparison and calibration are carried out to evaluate the force sensing accuracy of FBG sensors.

[0099] FBG sensors that have been calibrated for force sensing can be used for force sensing in natural cavities of the human body. Fig.14 As shown in the figure, many natural cavities are narrow and tortuous, and the calibrated FBG optical fiber measures the Bragg center wavelength of the FBG grating in real time in the natural cavity (such as the ear canal). When the FBG sensor contacts the tissue, the Bragg center wavelength of the FBG grating at the corresponding position shifts. After the modem and the data processing end process and calculate the wavelength shift, the software end processes and outputs the force sensing results, such as the location of the contact, the magnitude and direction of the force generated by the contact, and is supplemented by real-time graphical output, making the force sensing results more intuitive.

[0100] 4. FBG force sensing information acquisition

[0101] The equilibrium equation and constitutive equation based on the Cosserat rod model are proposed to realize the contact force perception algorithm of the natural cavity.

[0102] The FBG sensor array consists of four optical fibers, which are divided into external optical fibers and central optical fibers. A central optical fiber is arranged at the center of the FBG sensor, corresponding to Fig.15 The fiber Bragg grating with the serial number ④ is shown in FIG. The three external optical fibers are evenly arranged circumferentially at intervals of 120°, corresponding to Fig.15 The fiber Bragg gratings marked with serial numbers ①, ②, and ③ can determine the Bragg center wavelength change and strain calculation in real time, and obtain the strain information ε of each grating point ij (i,j=1,2,3), where j represents the fiber Bragg grating sensor at different positions, i represents the different fiber Bragg gratings on each sensor, and Fig.15 The serial numbers marked in correspondence.

[0103] The strain ε of each fiber Bragg grating ij (i, j = 1, 2, 3) can be used to calculate the curvature κ of the corresponding position j and the torsion angle θ bj By expressing, the curvature and torsion angle of each fiber grating can be further calculated, and the curvature vector is defined as follows:

[0104]

[0105] Then, at the jth fiber Bragg grating, the following geometric parameters can be obtained: curvature Twist angle θ bj =∠κ appj .

[0106] The curvature and torsion angle values ​​are modeled by Cosserat, and based on the equilibrium equation and constitutive equation of the Cosserat rod model, the magnitude, direction and position information of the contact force on the continuum robot are sensed. In addition, since the FBG sensor is a distributed sensor, the curvature and torsion information is discrete, and interpolation is required to obtain more complete information along the length of the FBG fiber.

[0107] The curvature and torsion angle at each fiber Bragg grating obtained above can be defined as:

[0108] The internal moment vector u is calculated from the constitutive equation of the Cosserat rod model j =K u (u j -u0), where K uis the [3×3] bending and torsional stiffness matrix, u0 is the [3×1] reference angle strain vector, and is defined as u0 = [0] 3×1 .

[0109] Since the FBG fiber is not subject to contact torque, the equilibrium equation of the Cosserat rod model can be expressed as [3×1] internal force vector n j and [3×1] internal moment vector m j Further calculate the contact force vector f at each fiber Bragg grating j :

[0110]

[0111] Among them, f j is the [3×1] contact force vector at each FBG, is the angular strain matrix in antisymmetric form, is the linear strain matrix in antisymmetric form.

[0112] Those skilled in the art may understand this embodiment as a more specific description of Embodiment 1.

[0113] Those skilled in the art know that, in addition to realizing the system and its various devices, modules, and units provided by the present invention in a purely computer-readable program code, it is entirely possible to realize the same functions in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered as a hardware component, and the devices, modules, and units included therein for realizing various functions can also be regarded as structures within the hardware component; the devices, modules, and units for realizing various functions can also be regarded as both software modules for realizing the method and structures within the hardware component.

[0114] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A FBG system for narrow ear canal force sensing, characterized in that: include: Data processing and output terminal, modem, fiber fixture, FBG fiber, slide rail, mobile platform, ATI six-axis force sensor, 3D camera and ATI demodulator; The data processing and output ends are respectively connected to a modem, an ATI demodulator and a 3D camera; the modem is connected to an optical fiber fixture; an FBG optical fiber is passed through the optical fiber fixture, and the optical fiber fixture is installed on a slide rail; the mobile platform is installed on the slide rail, an ATI six-axis force sensor is installed on the mobile platform, and the ATI six-axis force sensor is connected to the ATI demodulator.

2. The FBG system for narrow ear canal force sensing according to claim 1, characterized in that: The modem is used to receive wavelength information on the FBG optical fiber and convert it into information of strain change.

3. The FBG system for narrow ear canal force sensing according to claim 1, characterized in that: The FBG optical fiber is engraved with a sensing unit for sensing the contact force in the ear canal.

4. The FBG system for narrow ear canal force sensing according to claim 1, characterized in that: The slide rail and the moving platform are used to generate axial or radial forces.

5. The FBG system for narrow ear canal force sensing according to claim 1, characterized in that: The ATI six-axis force sensor is fixed on the slide rail and the moving platform and is used to measure the standard value of the contact force.

6. The FBG system for narrow ear canal force sensing according to claim 1, characterized in that: The 3D camera is arranged on the side of the FBG optical fiber, the guide wire twister and the ATI six-axis force sensor, and is used to photograph the relative position between the FBG optical fiber and the ATI force sensor to obtain the standard value of the position and direction angle of the contact force.

7. A FBG method for narrow ear canal force sensing, characterized in that: The method uses the FBG system for narrow ear canal force sensing as described in any one of claims 1 to 6, and the method comprises the following steps: Step S1: using a fiber Bragg grating (FBG) sensor as a flexible sensing unit, three-dimensionally bending according to the shape of the ear canal, and sensing force; Step S2: controlling the influence of temperature change on the fiber Bragg grating (FBG) sensor, so that the fiber Bragg grating (FBG) sensor array has the ability to measure the contact force in a narrow natural cavity; Step S3: receiving wavelength information on the FBG optical fiber through a modem and converting it into strain change information; Step S4: The data processing and output end reads the strain change information processed by the modem, and performs subsequent strain-force information processing to obtain the result of FBG force sensing, that is, the size, direction and position of the contact force.

8. The FBG method for narrow ear canal force sensing according to claim 7, characterized in that: The fiber Bragg grating (FBG) sensor comprises: Multi-core fiber MCF: contains multiple independent cores, each of which is engraved with a Bragg grating FBG to sense strain changes; Sensor head: Made of metal or ceramic, with PTFE coated on the surface to conduct force; Elastic tube: Made of highly elastic polymer, bonded to the surface of the first grating area, used to enhance the strain sensing capability of the fiber Bragg grating FBG sensor; Tube body: Made of metal or braided tube, used to encapsulate the optical fiber and allow it to bend freely; Optical fiber connector: used to connect FBG optical fiber and modem; Adhesive layer: used to connect the sensor head, elastic tube, tube body and multi-core optical fiber MCF into one.

9. The FBG method for narrow ear canal force sensing according to claim 8, characterized in that: The sensor head end transmits the force to the elastic tube; the bonding layer includes a first bonding layer and a second bonding layer; a first small hole is radially opened at the sensor head end, and glue is poured into the first small hole to form a first bonding layer, so as to connect the sensor head end with the front end of the multi-core optical fiber MCF as a whole.

10. The FBG method for narrow ear canal force sensing according to claim 9, characterized in that: The elastic tube detects the axial force and radial force on the sensor head end; a second small hole is opened in the radial direction of the tube body, and glue is poured into the second small hole to form a second bonding layer to connect the tube body and the multi-core optical fiber MCF into one.

Images