Ankle joint motion angle measurement device and method

Abstract

The present invention provides an ankle joint motion angle measurement device and method, relating to the field of angle measurement technology. The device comprises: a first equidistant helical structure, a planar spring structure, a second equidistant helical structure, a central axis, a housing, and a connecting rod. The equidistant helical structure comprises an equidistant helical structure static platform and an equidistant helical structure dynamic platform. The planar spring structure comprises a planar spring static platform and a planar spring dynamic platform. The first equidistant helical structure, the planar spring structure, and the second equidistant helical structure are coaxially connected with the central axis. The housing comprises a foot connection end and a cover plate matching the first and second equidistant helical structures. Deformations generated by movement in different directions are concentratedly transmitted to a fiber Bragg grating, achieving high-precision ankle joint motion angle measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of angle measurement, and in particular to a device and method for measuring the angle of ankle joint motion. Background Art

[0002] The ankle joint is a crucial weight-bearing and movement hub in the lower limb. Composed primarily of the tibia, fibula, and talus, it serves as a hinge connecting the lower leg and foot. It possesses two primary degrees of freedom: plantar flexion / dorsiflexion (sagittal plane movement) and inversion / eversion (frontal plane movement). It participates in key daily movements such as standing, walking, running, and jumping, bearing the combined influence of body weight and ground reaction forces.

[0003] Ankle angle measurement uses specific sensing technology to monitor and record ankle angular movements in different directions in real time. This includes plantar flexion (downward pressure) and dorsiflexion (upward lift) in the sagittal plane, as well as inversion (foot pointing inward) and eversion (foot pointing outward) in the frontal plane. Ankle angle measurement plays a key role in medical rehabilitation, performance optimization, and injury warning. It provides doctors with accurate range of motion data to assist in developing personalized rehabilitation plans, helps coaches analyze athletes' technical movements, and continuously monitors and warns of fall risks and chronic injury trends, playing an irreplaceable role in clinical, sports, and home health monitoring scenarios.

[0004] The existing ankle joint motion angle measurement process is mostly through visual detection or angle estimation through sensors, which is easily affected by obstructions and local electromagnetic interference, reducing the accuracy of ankle joint motion angle measurement and limiting the scope of application. Summary of the Invention

[0005] In order to solve the technical problems in the existing technology that the measurement process of ankle joint motion angle is mostly carried out through visual detection or angle estimation through sensors, which is easily affected by obstructions and local electromagnetic interference, reduces the accuracy of ankle joint motion angle measurement, and has a limited scope of application, the present invention provides an ankle joint motion angle measurement device and method.

[0006] The technical solutions provided by the embodiments of the present invention are as follows:

[0007] First aspect

[0008] An embodiment of the present invention provides an ankle joint motion angle measurement device, comprising:

[0009] a first equidistant helical structure, a planar spring structure, a second equidistant helical structure, a central shaft, a housing, and a connecting rod;

[0010] The first equidistant helical structure and the second equidistant helical structure each include an equidistant helical structure static platform and an equidistant helical structure dynamic platform, wherein a first equidistant helical beam and a second equidistant helical beam are arranged on a plane where the equidistant helical structure static platform is located, starting from the equidistant helical structure static platform and spaced apart by a first preset angle, and a flexion-extension motion monitoring fiber Bragg grating is arranged in the spiral direction of each equidistant helical beam, wherein each equidistant helical beam extends to the equidistant helical structure dynamic platform;

[0011] The planar spring structure includes a planar spring static platform and a planar spring dynamic platform. A plurality of distributed flexible beams are arranged on a plane where the planar spring static platform is located, with the planar spring static platform as a starting point and spaced at intervals of a second preset angle. A tilt motion monitoring fiber Bragg grating is arranged on one of the distributed flexible beams, wherein each of the distributed flexible beams extends to the planar spring dynamic platform.

[0012] The first equidistant helical structure, the planar spring structure and the second equidistant helical structure are coaxially connected with the central axis as the axis;

[0013] The housing includes a foot connection end and a cover plate matching the first equidistant helical structure and the second equidistant helical structure;

[0014] The connecting rod includes a leg connecting end and a planar spring connecting end matching the planar spring structure.

[0015] Second aspect

[0016] An embodiment of the present invention provides a method for measuring an ankle joint motion angle, which is applied to the ankle joint motion angle measuring device according to the first aspect. The method includes:

[0017] S1: Obtaining a first wavelength offset of each of the flexion and extension motion monitoring fiber Bragg gratings;

[0018] S2: Obtaining a second wavelength offset of the tilt motion monitoring fiber Bragg grating;

[0019] S3: calculating the flexion and extension rotation angle according to the first wavelength offset;

[0020] S4: Calculating the tilting motion rotation angle according to the second wavelength offset;

[0021] S5: Outputting the flexion and extension movement rotation angle and the tilt movement rotation angle.

[0022] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0023] In an embodiment of the present invention, an ankle joint motion angle measurement device is provided with a first equidistant spiral structure, a second equidistant spiral structure and a planar spring structure, and is coaxially connected in series through a central axis to construct a three-dimensional motion response system with both structural flexibility and directional differentiation. Among them, the planar spring structure is composed of a plurality of flexible beams and a dynamic and static platform. It has a high flexibility in the frontal plane direction, i.e., inversion and eversion, and is specifically used to detect the inversion / eversion angle, while the equidistant spiral structure has a large flexibility in the sagittal plane direction, i.e., plantar flexion and dorsiflexion, and is specifically used for plantar flexion / dorsiflexion angle sensing. This structural division of labor allows the main deformations generated by movements in different directions to be concentrated and transmitted to the fiber Bragg grating, reducing the measurement crosstalk between the two degrees of freedom of movement. In addition, a fiber Bragg grating is integrated on each key flexible beam, which can convert local microstrain into wavelength deviation, realize high-precision ankle joint motion angle measurement, avoid ambient light interference, and has multiple advantages such as anti-electromagnetic interference, comfortable to wear, clear decoupling, and compact structure, which can effectively expand the applicable scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 A schematic diagram of the exploded structure of an ankle joint motion angle measurement device provided by an embodiment of the present invention;

[0026] Figure 2 A schematic diagram of the overall structure of an ankle joint motion angle measurement device provided by an embodiment of the present invention;

[0027] Figure 3 A schematic structural diagram of a first equidistant spiral structure and a second equidistant spiral structure provided by an embodiment of the present invention;

[0028] Figure 4 A schematic structural diagram of a planar spring structure provided by an embodiment of the present invention;

[0029] Figure 5 A schematic diagram of a combined structure of a first equidistant spiral structure, a second equidistant spiral structure, and a planar spring structure provided in an embodiment of the present invention;

[0030] Figure 6 A schematic diagram of an exemplary structure of an angle measurement system having an ankle joint motion angle measurement device provided by an embodiment of the present invention;

[0031] Figure 7A schematic diagram of experimental data of the rotation angle and wavelength offset of a flexion and extension movement provided by an embodiment of the present invention;

[0032] Figure 8 A schematic diagram of experimental data of a tilt motion rotation angle and wavelength offset provided by an embodiment of the present invention;

[0033] Figure 9 A schematic flow chart of a method for measuring ankle joint motion angle provided in an embodiment of the present invention.

[0034] Description of Reference Numerals

[0035] 1. First equidistant spiral structure; 101. Static platform of equidistant spiral structure; 102. Dynamic platform of equidistant spiral structure; 103. First equidistant spiral beam; 1031. Groove of equidistant spiral beam; 104. Second equidistant spiral beam; 2. Plane spring structure; 201. Static platform of plane spring; 202. Dynamic platform of plane spring; 203. Distributed flexible beam; 2031. Groove of distributed flexible beam; 2032. First distributed flexible beam; 2033. Second distributed flexible beam; 2034. Third distributed flexible beam; 3. Second equidistant spiral structure; 4. Center axis; 401. Plane spring connecting disk; 402. Center through hole; 5. Shell; 501. Foot connecting end; 502. Cover plate; 6. Connecting rod; 601. Leg connecting end; 602. Plane spring connecting end. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0037] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as an "exemplary" in the present invention should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of the word "exemplary" is intended to present concepts in a concrete manner. Furthermore, in the embodiments of the present invention, "and / or" can mean both or either of the two.

[0038] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, when the distinction is not emphasized, the meanings they convey are the same. The terms "of," "corresponding," and "corresponding" may sometimes be used interchangeably. It should be noted that, when the distinction is not emphasized, the meanings they convey are the same.

[0039] In the embodiments of the present invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript form such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0040] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0041] Reference Manual Figure 1 , shows a schematic diagram of the exploded structure of an ankle joint motion angle measurement device provided by an embodiment of the present invention.

[0042] Reference Manual Figure 2 , shows a schematic diagram of the overall structure of an ankle joint motion angle measurement device provided by an embodiment of the present invention.

[0043] Reference Manual Figure 3 , showing a structural schematic diagram of a first equidistant spiral structure and a second equidistant spiral structure provided by an embodiment of the present invention.

[0044] Reference Manual Figure 4 , which shows a structural schematic diagram of a planar spring structure provided by an embodiment of the present invention.

[0045] Reference Manual Figure 5 , shows a schematic diagram of a combined structure of a first equidistant spiral structure, a second equidistant spiral structure and a planar spring structure provided by an embodiment of the present invention.

[0046] Reference Manual Figure 6 , shows an example structural diagram of an angle measurement system with an ankle joint motion angle measurement device provided by an embodiment of the present invention.

[0047] Figure 6 The signal processing process of the ankle joint motion angle measurement system is demonstrated: First, the ankle joint motion angle measurement device, when worn, collects strain signals caused by human motion. These signals are then wavelength-modulated by a connected fiber optic interrogator and converted into electrical signals. Finally, the data is transmitted via an interface to a personal computer (PC), where angle calculations and visualization output are performed, enabling real-time monitoring and analysis of the ankle joint's two-degree-of-freedom motion. This process offers the advantages of a clear structure, efficient data transmission, and high processing accuracy.

[0048] Reference Manual Figure 7 , which shows a schematic diagram of experimental data of the rotation angle and wavelength offset of a flexion and extension movement provided by an embodiment of the present invention.

[0049] Figure 7 The corresponding relationship between the ankle plantar flexion / dorsiflexion degree of freedom angle and the optical fiber wavelength offset is shown, where Fiber1 and Fiber2, two flexion and extension motion monitoring fiber Bragg gratings, are used to measure the sagittal plane angle, showing a high linear correlation ( ), indicating that wavelength shifts can accurately reflect angular changes. Furthermore, when using Fiber3 for frontal plane measurements, there was virtually no response in this degree of freedom, verifying the low crosstalk between the two directions, which was only 0.91%. The measurement resolution in this direction reached 37.09 pm / °, demonstrating the system's excellent performance in terms of angle perception accuracy and directional decoupling.

[0050] Reference Manual Figure 8 , which shows a schematic diagram of experimental data of a tilt motion rotation angle and wavelength offset provided by an embodiment of the present invention.

[0051] Figure 8 The relationship between the ankle inversion / eversion degree of freedom angle and the fiber wavelength offset is shown. The wavelength variation generated by Fiber3 (the tilt motion monitoring fiber Bragg grating) (used for frontal plane detection) exhibits a good linear trend, with a linearity of up to 0.9970 and a range of ±23°, indicating that the tilt motion monitoring fiber Bragg grating is sensitive to angular variations in this direction. The wavelength variation of the two flexion and extension motion monitoring fiber Bragg gratings, Fiber1+Fiber2, shows almost no wavelength variation, verifying that the measurement crosstalk in this direction is extremely low, at only 0.57%. The system's angular resolution in this direction is 224.70 pm / °, demonstrating its extremely high accuracy and good decoupling characteristics for inversion and elongation monitoring.

[0052] An embodiment of the present invention provides an ankle joint motion angle measurement device, comprising: a first equidistant helical structure 1, a planar spring structure 2, a second equidistant helical structure 3, a central axis 4, a housing 5, and a connecting rod 6. The first equidistant helical structure 1 and the second equidistant helical structure 3 each include an equidistant helical structure static platform 101 and an equidistant helical structure dynamic platform 102. On the plane where the equidistant helical structure static platform 101 resides, a first equidistant helical beam 103 and a second equidistant helical beam 104 are arranged with the equidistant helical structure static platform 101 as a starting point and at intervals of a first preset angle. A fiber Bragg grating for monitoring flexion and extension motion is arranged in the spiral direction of each equidistant helical beam, wherein each equidistant helical beam extends to the equidistant helical structure dynamic platform 102. The planar spring structure 2 comprises a planar spring static platform 201 and a planar spring dynamic platform 202. Multiple distributed flexible beams 203 are arranged on the plane of the planar spring static platform 201, starting from the planar spring static platform 201 and spaced apart by a second predetermined angle. One of the distributed flexible beams 203 is equipped with a tilt motion monitoring fiber Bragg grating (FBG). Each distributed flexible beam 203 extends to the planar spring dynamic platform 202. The first equidistant helical structure 1, the planar spring structure 2, and the second equidistant helical structure 3 are coaxially connected around a central axis 4. The first and second equidistant helical structures 1 and 3 are located at opposite ends of the central axis 4, respectively. The planar spring structure 2 is coaxially arranged on the central axis 4 with the first and second equidistant helical structures 1 and 3. The housing 5 comprises a foot connection 501 and a cover plate 502 that mates with the first and second equidistant helical structures 1 and 3. The connecting rod 6 comprises a leg connection 601 and a planar spring connection 602 that mates with the planar spring structure 2. When the ankle joint moves, the fiber Bragg grating is deformed, and the ankle joint movement angle is obtained based on the fiber Bragg grating wavelength shift caused by the deformation.

[0053] The first equidistant helical structure 1 responds to plantar flexion / dorsiflexion. Its helical beam exhibits high flexibility in this direction. This deformation induces strain in both the flexion-extension monitoring fiber Bragg gratings (FBG1) and flexion-extension monitoring fiber Bragg gratings (FBG2), enabling angular sensing of sagittal plane motion. The equidistant helical structure's static platform 101 serves as a fixed base, securing one end of the helical beam and restricting its movement on one side, providing an anchor point for deformation at the other end. The equidistant helical structure's dynamic platform 102, connected to external moving components, drives the helical beam's deformation through its movement and serves as the output for angular rotation. The first and second equidistant helical beams 103 and 104 are flexible structures capable of elastic torsional deformation, converting angular changes into local strain, thereby driving the FBGs to generate wavelength variations. This wavelength variation is then used to indirectly measure ankle joint angle. Fiber Bragg gratings (FBGs) are affixed to the helical beams, detecting microstrains and converting them into wavelength signals for angle calculation. The planar spring structure 2 responds to inversion / valgus motion. The flexible beam exhibits significant flexibility in the frontal plane and, in conjunction with FBG3, senses tilt angle. The planar spring static platform 201 and the planar spring dynamic platform 202 respectively secure the ends of the flexible beam. The static platform is mounted on the central axis, while the dynamic platform rotates with the lateral movement of the connecting rod. The distributed flexible beam 203 acts as a carrier for structural deformation, driving the FBG angle measurement through deformation. The second equidistant helical structure 3 is symmetrically arranged with the first equidistant helical structure 1 to balance and enhance structural stability (it can also be used for bidirectional data acquisition). The central axis 4 connects the axial components of each flexible structure in series, ensuring coaxial transmission and angular decoupling. The housing 5 encapsulates the first equidistant helical structure 1, the planar spring structure 2, the second equidistant helical structure 3, and the central axis 4, and connects them to the foot. The foot connector 501 secures the sensing structure to the foot, providing an input source for angle signals. The cover 502, in conjunction with the equidistant helical structure, protects the internal structure and maintains the device's posture. The connecting rod 6 securely connects the device to the calf, transmitting ankle joint motion to the internal sensing structure. The leg connector 601 connects to the calf to acquire actual motion. The planar spring connection end 602 is connected to the planar spring dynamic platform 202 and serves as a driving source for the inversion / eversion movement.

[0054] In actual application, human ankle joint movement drives relative rotation between the connecting rod (calf end) and the housing (foot end). This rotation is transmitted along the central axis to the planar spring and equidistant helical structure. Inversion / eversion movement causes deformation of the planar spring structure's flexible beam, driving strain in FBG3 (the tilt motion monitoring fiber Bragg grating). Plantar flexion / dorsiflexion movement acts on the equidistant helical structure, inducing deformation in FBG1 and FBG2 (the tilt motion monitoring fiber Bragg gratings). Each direction of motion is guided by a dedicated flexible mechanism, significantly reducing crosstalk between the two degrees of freedom. Real-time calculation of joint angles is achieved using the FBG grating's wavelength offset signal, resulting in strong decoupling, high measurement accuracy, and robust interference immunity, making it suitable for high-precision ankle joint measurement requirements in diverse scenarios.

[0055] Specifically, the first equidistant helical structure 1 and the second equidistant helical structure 3 are both fixedly connected to the cover plate 502. Specifically, matching connection holes are provided on the first equidistant helical structure 1, the second equidistant helical structure 3, and the cover plate 502, and the first equidistant helical structure 1 and the second equidistant helical structure 3 are both fixedly connected to the cover plate 502 through the connection holes.

[0056] Specifically, the planar spring structure 2 is fixedly connected to the planar spring connection end 602. Specifically, both the planar spring structure 2 and the planar spring connection end 602 are provided with matching connection holes, and the planar spring structure 2 and the planar spring connection end 602 are fixedly connected via the connection holes.

[0057] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0058] In an embodiment of the present invention, an ankle joint motion angle measurement device is provided with a first equidistant spiral structure, a second equidistant spiral structure and a planar spring structure, and is coaxially connected in series through a central axis to construct a three-dimensional motion response system with both structural flexibility and directional differentiation. Among them, the planar spring structure is composed of a plurality of flexible beams and a dynamic and static platform. It has a high flexibility in the frontal plane direction, i.e., inversion and eversion, and is specifically used to detect the inversion / eversion angle, while the equidistant spiral structure has a large flexibility in the sagittal plane direction, i.e., plantar flexion and dorsiflexion, and is specifically used for plantar flexion / dorsiflexion angle sensing. This structural division of labor allows the main deformations generated by movements in different directions to be concentrated and transmitted to the fiber Bragg grating, reducing the measurement crosstalk between the two degrees of freedom of movement. In addition, a fiber Bragg grating is integrated on each key flexible beam, which can convert local microstrain into wavelength deviation, realize high-precision ankle joint motion angle measurement, avoid ambient light interference, and has multiple advantages such as anti-electromagnetic interference, comfortable to wear, clear decoupling, and compact structure, which can effectively expand the applicable scenarios.

[0059] In a possible implementation, each equidistant spiral beam is provided with an equidistant spiral beam groove 1031 in the spiral direction. Fiber Bragg gratings for monitoring flexion and extension motion are arranged in the equidistant spiral beam groove 1031 .

[0060] It should be noted that equidistant spiral beam grooves 1031 are provided along the spiral direction of the equidistant spiral beam for accurately embedding and fixing the flexion and extension motion monitoring fiber Bragg grating, ensuring that the optical fiber fits tightly against the beam surface, improving the strain transmission efficiency and wavelength response sensitivity, and preventing the optical fiber from sliding or being damaged during structural deformation, thereby improving the stability and reliability of the measurement system.

[0061] In a possible implementation manner, the first preset angle is 180°.

[0062] The first equidistant spiral beam 103 and the second equidistant spiral beam 104 are arranged at intervals of 180° on the plane where the static platform 101 of the equidistant spiral structure is located.

[0063] It should be noted that the first equidistant helical beam 103 and the second equidistant helical beam 104 are arranged 180° symmetrically on the static platform plane, i.e., they are linearly opposed to each other. This structural arrangement achieves structural balance and symmetry, making the device more uniform in strain distribution when subjected to force or deformation, improving the stability and anti-interference capabilities of the fiber optic measurement signal, and facilitating dual-channel signal fusion or differential analysis when calculating motion angles, thereby enhancing measurement accuracy.

[0064] In a possible implementation, a distributed flexible beam groove 2031 is formed on the distributed flexible beam 203. A tilt motion monitoring fiber Bragg grating is arranged in the distributed flexible beam groove 2031.

[0065] It should be noted that the distributed flexible beam 203 is provided with a dedicated distributed flexible beam groove 2031 for embedding a fiber Bragg grating (FBG) for tilt motion monitoring. This groove design ensures that the optical fiber is accurately positioned and tightly adheres to the beam surface, allowing the strain energy generated by flexible beam deformation to be efficiently transferred to the optical fiber. This improves the optical fiber's response sensitivity and measurement accuracy to tilt motions such as inversion and eversion, and effectively reduces the impact of installation errors and external disturbances on measurement results.

[0066] In one possible embodiment, the distributed flexible beams 203 include a first distributed flexible beam 2032, a second distributed flexible beam 2033, and a third distributed flexible beam 2034. The second preset angle is 120°. The first distributed flexible beams 2032, 2033, and 2034 are arranged at intervals of 120° on the plane of the planar spring static platform 201. The first distributed flexible beams 2032, 2033, and 2034 all extend to the planar spring dynamic platform 202.

[0067] It should be noted that the three distributed flexible beams in the planar spring structure—first distributed flexible beam 2032, second distributed flexible beam 2033, and third distributed flexible beam 2034—are symmetrically arranged at 120-degree intervals on the static platform plane and connected to the planar spring dynamic platform 202, forming a stable three-point support structure. This equiangular arrangement not only helps distribute the load and improve the uniform force performance of the spring structure, but also enhances the system's sensitivity and stability to changes in inversion / valgus angles. It also strengthens the overall structural symmetry and deformation consistency, facilitating the precise acquisition of microstrain signals caused by tilting motion.

[0068] In one possible embodiment, a planar spring connection plate 401 is provided on the central shaft 4 to secure the planar spring structure 2. A central through-hole 402 is defined at the center of the planar spring structure 2 for passing through the central shaft 4. The diameter of the planar spring connection plate 401 is larger than that of the central through-hole 402. Each equidistant spiral structure static platform 101 is fixedly connected to the central shaft 4. The planar spring static platform 201 of the planar spring structure 2 is also fixedly connected to the central shaft 4.

[0069] It should be noted that a planar spring connection plate 401 is provided on the central shaft 4 for positioning and stably securing the planar spring structure 2. This connection plate has a diameter larger than the planar spring central through-hole 402, effectively limiting the radial displacement of the spring structure and ensuring reliable positioning. The planar spring structure is fixedly connected to the central shaft via a planar spring static platform 201, ensuring coaxial rotation during transmission. Simultaneously, the two equidistant helical static platforms 101 are also fixed to the central shaft, forming a coaxial, rigid, and stable multi-degree-of-freedom linkage system. This provides the structural foundation for high-precision and low-crosstalk angle measurement.

[0070] Specifically, both the equidistant spiral structure static platform 101 and the planar spring static platform 201 are provided with connection holes that match the planar spring connection disk 401. Both the equidistant spiral structure static platform 101 and the planar spring static platform 201 are fixedly connected to the planar spring connection disk 401 through the connection holes.

[0071] In practical applications, when a person performs gait or specific movements, ankle joint motion (including plantar flexion / dorsiflexion and inversion / eversion) generates relative rotation between the calf-end connecting rod and the foot-end housing. This rotation is transmitted sequentially through the central axis to the first equidistant helical structure, the planar spring structure, and the second equidistant helical structure. Movement in different directions causes dominant deformation in specific structures: plantar flexion / dorsiflexion primarily drives torsional deformation of the equidistant helical beam, generating strain in FBG1 and FBG2. Inversion / eversion, on the other hand, causes bending deformation of the planar spring flexible beam, generating strain in FBG3. A fiber Bragg grating converts the sensed microstrain into a wavelength shift signal. This data is then analyzed by a demodulator and a computing system to calculate the ankle joint angle changes in both degrees of freedom. This device offers strong decoupling, sensitive response, and stable signals during ankle joint angle measurement. It also boasts extremely high angle measurement resolution and excellent interference immunity, making it suitable for clinical rehabilitation monitoring, motor function assessment, and smart wearable applications.

[0072] Reference Manual Figure 9 , shows a flow chart of a method for measuring ankle joint motion angle provided by an embodiment of the present invention.

[0073] The present invention also provides a method for measuring ankle joint motion angle, which is applied to the above-mentioned ankle joint motion angle measuring device, and the method comprises:

[0074] S1: Obtaining the first wavelength offset of each flexion and extension motion monitoring fiber Bragg grating.

[0075] It should be noted that a fiber optic interrogator collects the wavelength shift of the flexion-extension monitoring fiber Bragg grating (FBG) mounted on an equidistant helical beam in real time, recording the strain response caused by the deformation of the helical beam during plantar flexion and dorsiflexion. These wavelength shifts reflect the magnitude of the microstrain on the fiber and serve as a key input signal for the subsequent calculation of sagittal plane rotation angle, ensuring the accuracy and real-time performance of the angle solution.

[0076] S2: Obtain the second wavelength offset of the tilt motion monitoring fiber Bragg grating.

[0077] It should be noted that the wavelength shift of the tilt-monitoring fiber Bragg grating (FBG) mounted on a planar spring-loaded flexible beam is measured to capture the microstrain response caused by the bending of the beam during inversion / valgus motion. This wavelength shift reflects the deformation caused by ankle joint motion in the frontal plane and serves as the basis for calculating the inversion / valgus angle.

[0078] In a possible implementation manner, the first wavelength offset and the second wavelength offset are acquired by a fiber optic interrogator.

[0079] It should be noted that both the first wavelength offset and the second wavelength offset are obtained through a fiber optic demodulator. This device can collect the wavelength changes in the Bragg grating reflection signal in real time with high sensitivity and convert it into digital data, ensuring that the microstrain signals caused by plantar flexion / dorsiflexion and inversion / valgus movements are accurately recorded, providing high-precision input for subsequent angle calculation.

[0080] S3: Calculate the flexion and extension rotation angle according to the first wavelength offset.

[0081] In a possible implementation, the calculation method of the flexion and extension rotation angle is specifically as follows:

[0082] ;

[0083] in, represents the initial Bragg wavelength of the FBG for monitoring the flexion and extension motion on the first equidistant helical beam, represents the initial Bragg wavelength of the FBG monitoring flexion-extension motion on the second equidistant helical beam, , represents the first wavelength offset of the flexion-extension motion monitoring fiber Bragg grating on the first equidistant helical beam, represents the first wavelength offset of the flexion-extension monitoring fiber Bragg grating on the second equidistant helical beam, It represents the proportional coefficient between the rotation angle of the flexion-extension motion and the strain of the flexion-extension motion monitoring fiber Bragg grating on the first equidistant spiral beam, It represents the proportional coefficient between the rotation angle of the flexion-extension motion and the strain of the flexion-extension motion monitoring fiber Bragg grating on the second equidistant spiral beam, , Indicates the rotation angle of flexion and extension movement, Indicates the effective photoelastic coefficient of the optical fiber material that transmits optical signals.

[0084] It should be noted that the calculation of the flexion-extension rotation angle is based on the proportional change in the wavelength offset of the fiber Bragg gratings on two equidistant spiral beams relative to their initial wavelength. The wavelength offset is converted to equivalent strain using a proportionality factor. Combined with the fiber strain response model shown in the formula, the corresponding plantar flexion / dorsiflexion angles are calculated. Because the two optical fibers are symmetrically arranged and have consistent structural responses, dual-channel complementary calibration is possible, improving the accuracy of the angle calculation and robustness against interference.

[0085] S4: Calculate the tilting motion rotation angle according to the second wavelength offset.

[0086] In a possible implementation, the tilting motion rotation angle is calculated as follows:

[0087] ;

[0088] in, represents the initial Bragg wavelength of the fiber Bragg grating monitored by the tilt motion on the distributed flexible beam, represents the second wavelength offset of the oblique motion monitoring fiber Bragg grating on the distributed flexible beam, It represents the proportional coefficient between the tilt motion rotation angle and the tilt motion monitoring fiber Bragg grating strain, Indicates the tilting motion rotation angle, Indicates the effective photoelastic coefficient of the optical fiber material that transmits optical signals.

[0089] It should be noted that the calculation of the tilting rotation angle (i.e., the varus / valgus angle) is based on the proportional change in the wavelength offset of the fiber Bragg grating on the distributed flexible beam relative to its initial Bragg wavelength. This wavelength change is converted into strain using a proportionality factor, and the corresponding angle is further calculated. High-precision frontal plane motion can be determined using a single grating signal. This simple structure and high sensitivity facilitate real-time monitoring of varus / valgus angle changes.

[0090] It should be noted that the ankle joint structure is relatively complex, and its flexion and extension and tilt movements are not pure rotational movements, but will be accompanied by the offset of the ankle joint rotation center. If this problem is not solved, on the one hand, it will reduce the wearing comfort of the sensor, and on the other hand, it will affect the measurement of the angle of rotation, resulting in measurement crosstalk. Due to the flexibility distribution characteristics of the equidistant spiral structure, in addition to the plantar flexion / dorsiflexion and inversion / eversion movements of the ankle joint, the ankle joint angle sensor can also move within the plane, which can adapt to the offset of the rotation center during the ankle joint movement, improve wearing comfort, and reduce measurement crosstalk. Taking the movement in the Y direction within the plane as an example, the relationship between the movement distance and the wavelength offset is:

[0091] ;

[0092] in, and They represent the Bragg wavelength shift of FBG1 and FBG2 due to the movement in the Y direction, and They represent the proportional coefficients of Y-direction movement and fiber strain. Since the two fibers are configured in the same way and the Y-direction movement has opposite effects on the strain of the two fibers, . Indicates the moving distance in the Y direction. and At the same time, it is affected by plantar flexion / dorsiflexion and two-directional translation, so we can get:

[0093] ;

[0094] in, and are the total Bragg wavelength shifts of FBG1 and FBG2, respectively.

[0095] Then we get:

[0096] ;

[0097] in, is the measurement sensitivity of plantar flexion / dorsiflexion rotation angle, is the measurement sensitivity of the varus / externus rotation angle.

[0098] S5: Output the flexion and extension rotation angle and the tilt movement rotation angle.

[0099] In practical applications, fiber Bragg gratings (FBGs) arranged on equidistant helical beams and distributed flexible beams collect strain wavelength offset signals generated by plantar flexion / dorsiflexion and inversion / eversion movements, respectively. A fiber optic interrogator reads the data in real time. Based on the proportional relationship between wavelength, strain, and angle, the system calculates the angles of motion in both directions, ultimately outputting precise flexion and extension and tilt angle values. This enables high-precision, low-crosstalk monitoring of the ankle joint's dual degrees of freedom (DOF) angles. This highly automated process is suitable for real-time assessment and motion analysis in multiple scenarios.

[0100] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0101] In an embodiment of the present invention, an ankle joint motion angle measurement device is provided with a first equidistant spiral structure, a second equidistant spiral structure and a planar spring structure, and is coaxially connected in series through a central axis to construct a three-dimensional motion response system with both structural flexibility and directional differentiation. Among them, the planar spring structure is composed of a plurality of flexible beams and a dynamic and static platform. It has a high flexibility in the frontal plane direction, i.e., inversion and eversion, and is specifically used to detect the inversion / eversion angle, while the equidistant spiral structure has a large flexibility in the sagittal plane direction, i.e., plantar flexion and dorsiflexion, and is specifically used for plantar flexion / dorsiflexion angle sensing. This structural division of labor allows the main deformations generated by movements in different directions to be concentrated and transmitted to the fiber Bragg grating, reducing the measurement crosstalk between the two degrees of freedom of movement. In addition, a fiber Bragg grating is integrated on each key flexible beam, which can convert local microstrain into wavelength deviation, realize high-precision ankle joint motion angle measurement, avoid ambient light interference, and has multiple advantages such as anti-electromagnetic interference, comfortable to wear, clear decoupling, and compact structure, which can effectively expand the applicable scenarios.

[0102] The above embodiments can be implemented in whole or in part via software, hardware (e.g., circuits), firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions or computer programs. When loaded or executed on a computer, the processes or functions described in accordance with the embodiments of the present invention are fully or partially performed. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired means (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium accessible by a computer, or a data storage system such as a server or data center that contains a collection of one or more available media. The available medium can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media. The semiconductor media can be a solid-state drive.

[0103] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. A and B can be singular or plural. Furthermore, the character " / " as used herein generally indicates an "or" relationship between the associated objects, but it may also indicate an "and / or" relationship. For specific understanding, please refer to the context.

[0104] In this disclosure, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or plural.

[0105] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0106] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0107] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0108] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0109] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0110] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0111] If the functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or the portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for enabling a computer system (which can be a personal computer, server, or network system, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes various media that can store program code, such as USB flash drives, mobile hard drives, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical disks.

[0112] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

[0113] There are a few points to note:

[0114] (1) The drawings of the embodiments of the present invention only relate to the structures related to the embodiments of the present invention. Other structures may refer to conventional designs.

[0115] (2) For the sake of clarity, the thickness of layers or regions in the drawings used to describe the embodiments of the present invention are exaggerated or reduced, that is, these drawings are not drawn to scale. It is understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "under" another element, the element may be "directly on" or "under" the other element or intervening elements may be present.

[0116] (3) In the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other to form new embodiments.

[0117] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An ankle joint motion angle measuring device, characterized in that: include: a first equidistant helical structure, a planar spring structure, a second equidistant helical structure, a central shaft, a housing, and a connecting rod; The first equidistant helical structure and the second equidistant helical structure each include an equidistant helical structure static platform and an equidistant helical structure dynamic platform, wherein a first equidistant helical beam and a second equidistant helical beam are arranged on a plane where the equidistant helical structure static platform is located, starting from the equidistant helical structure static platform and spaced apart by a first preset angle, and a flexion-extension motion monitoring fiber Bragg grating is arranged in the spiral direction of each equidistant helical beam, wherein each equidistant helical beam extends to the equidistant helical structure dynamic platform; The planar spring structure includes a planar spring static platform and a planar spring dynamic platform. A plurality of distributed flexible beams are arranged on a plane where the planar spring static platform is located, with the planar spring static platform as a starting point and spaced at intervals of a second preset angle. A tilt motion monitoring fiber Bragg grating is arranged on one of the distributed flexible beams, wherein each of the distributed flexible beams extends to the planar spring dynamic platform. The first equidistant helical structure, the planar spring structure and the second equidistant helical structure are coaxially connected with the central axis as the axis; The housing includes a foot connection end and a cover plate matching the first equidistant helical structure and the second equidistant helical structure; The connecting rod includes a leg connecting end and a planar spring connecting end matching the planar spring structure.

2. The ankle joint motion angle measuring device according to claim 1, characterized in that: Each equidistant spiral beam is provided with an equidistant spiral beam groove in the spiral direction; and a flexion-extension motion monitoring fiber Bragg grating is arranged in the equidistant spiral beam groove.

3. The ankle joint motion angle measuring device according to claim 1, characterized in that: The first preset angle is 180°; The first equidistant spiral beam and the second equidistant spiral beam are arranged at intervals of 180° on the plane where the static platform of the spiral structure is located.

4. The ankle joint motion angle measuring device according to claim 1, characterized in that: A distributed flexible beam groove is provided on the distributed flexible beam; and a tilt motion monitoring fiber Bragg grating is arranged in the distributed flexible beam groove.

5. The ankle joint motion angle measuring device according to claim 1, characterized in that: The distributed flexible beams include a first distributed flexible beam, a second distributed flexible beam and a third distributed flexible beam; the second preset angle is 120°; The first distributed flexible beam, the second distributed flexible beam and the third distributed flexible beam are arranged at intervals of 120° on the plane where the planar spring static platform is located, and the first distributed flexible beam, the second distributed flexible beam and the third distributed flexible beam all extend to the planar spring dynamic platform.

6. The ankle joint motion angle measuring device according to claim 1, characterized in that: A planar spring connecting disk for fixing the planar spring structure is provided on the central shaft; a central through hole for passing the central shaft is opened at the center of the planar spring structure, wherein the diameter of the planar spring connecting disk is larger than the diameter of the central through hole; Each of the equidistant spiral structure static platforms is fixedly connected to the central axis; The planar spring static platform of the planar spring structure is fixedly connected to the central axis.

7. A method for measuring ankle joint motion angle, characterized in that: The ankle joint motion angle measurement device according to any one of claims 1 to 6, wherein the method comprises: S1: Obtaining a first wavelength offset of each of the flexion and extension motion monitoring fiber Bragg gratings; S2: Obtaining a second wavelength offset of the tilt motion monitoring fiber Bragg grating; S3: calculating the flexion and extension rotation angle according to the first wavelength offset; S4: Calculating the tilting motion rotation angle according to the second wavelength offset; S5: Outputting the flexion and extension movement rotation angle and the tilt movement rotation angle.

8. The ankle joint motion angle measurement method according to claim 7, characterized in that: The first wavelength offset and the second wavelength offset are obtained by using an optical fiber demodulator.

9. The ankle joint motion angle measurement method according to claim 7, characterized in that: The calculation method of the flexion and extension rotation angle is specifically as follows: ； in, represents the initial Bragg wavelength of the FBG for monitoring the flexion and extension motion on the first equidistant helical beam, represents the initial Bragg wavelength of the FBG monitoring flexion-extension motion on the second equidistant helical beam, , represents the first wavelength offset of the flexion-extension motion monitoring fiber Bragg grating on the first equidistant helical beam, represents the first wavelength offset of the flexion-extension monitoring fiber Bragg grating on the second equidistant helical beam, It represents the proportional coefficient between the rotation angle of the flexion-extension motion and the strain of the flexion-extension motion monitoring fiber Bragg grating on the first equidistant spiral beam, It represents the proportional coefficient between the rotation angle of the flexion-extension motion and the strain of the flexion-extension motion monitoring fiber Bragg grating on the second equidistant spiral beam, , Indicates the rotation angle of flexion and extension movement, Indicates the effective photoelastic coefficient of the optical fiber material that transmits optical signals.

10. The ankle joint motion angle measurement method according to claim 7, characterized in that: The calculation method of the tilting motion rotation angle is specifically as follows: ； in, represents the initial Bragg wavelength of the fiber Bragg grating monitored by the tilt motion on the distributed flexible beam, represents the second wavelength offset of the oblique motion monitoring fiber Bragg grating on the distributed flexible beam, It represents the proportional coefficient between the tilt motion rotation angle and the tilt motion monitoring fiber Bragg grating strain, Indicates the tilting motion rotation angle, Indicates the effective photoelastic coefficient of the optical fiber material that transmits optical signals.

Images