An IMU-based three-dimensional motion capture method for foot joints

Abstract

The application provides a three-dimensional motion capture method for foot joints based on an IMU, which comprises the following steps: collecting foot motion data by using an IMU sensor; and analyzing foot motion according to the collected foot motion data. The application can measure the motion state of small foot joints in a real-life environment with bare feet or with shoes.

Description

Technical Field

[0001] This invention relates to the field of rehabilitation science and technology, and in particular to a method for three-dimensional motion capture of foot joints based on IMU. Background Technology

[0002] The foot is the foundation of the human body, composed of 26 bones, 33 joints, and soft tissues such as muscles and ligaments. The structure of the foot bones and the movement of the joints allow the body to adapt to different surfaces and perform various upright movements. When foot joint movement is abnormal, it can cause soft tissue overuse injuries in the foot and lower limbs, pain in the lower limbs and even the spine, and abnormal postures. Therefore, three-dimensional motion analysis of foot joint movement helps to quantitatively evaluate various foot injuries and rehabilitation effects.

[0003] Currently, common methods for three-dimensional foot motion analysis include optical motion capture and double-sided fluorescence. Both are expensive, require specific experimental facilities and can only be tested in a laboratory, and the latter involves radiation exposure. If measuring foot movement while wearing shoes or orthotics, the former requires modification to the shoe to allow markers to be applied to the skin, thus disrupting the shoe's structure and affecting the results. Neither method can measure the three-dimensional movement of the foot in real-life environments, whether barefoot or inside a shoe.

[0004] Currently, IMU sensors based on MEMS technology have been used for 3D motion capture of large human joints, such as shoulder / elbow / wrist / hip / knee / ankle, but have not yet been applied to motion capture of small foot joints, especially not to motion capture of foot joints after wearing shoes. Summary of the Invention

[0005] The purpose of this invention is to provide an IMU-based three-dimensional motion capture method for foot joints, which can measure the motion state of small joints of the foot in real-life environments, whether barefoot or wearing shoes.

[0006] A method for three-dimensional motion capture of foot joints based on IMU, comprising:

[0007] Foot movement data is collected using an IMU sensor;

[0008] Foot movement is analyzed based on the collected foot movement data.

[0009] Foot movement data collected using IMU sensors includes:

[0010] Wearable IMU sensors capture three-dimensional movements of the first metatarsophalangeal joint;

[0011] Wearable IMU sensors capture three-dimensional movements of the interphalangeal joints;

[0012] Wearable IMU sensors capture three-dimensional movements of the first metatarsal relative to the midfoot.

[0013] Wearable IMU sensors capture three-dimensional movements of the first metatarsophalangeal joint, including:

[0014] Attach IMU sensor 1 to The IMU sensor 2 is attached to the middle section of the posterior surface of the first metatarsal bone in the middle segment of the proximal phalanx of the toe, with the X-axis direction of the IMU sensor coinciding with the line of the attached bone.

[0015] Secure each IMU sensor, and use elastic bands and buckles to fix the control module corresponding to the IMU sensor to the ankle joint.

[0016] Wearable IMU sensors capture three-dimensional movements of the interphalangeal joints, including:

[0017] 3D motion capture of the interphalangeal joint: attaching the IMU sensor 3 to In the middle of the distal phalanx of the phalanx, the X-axis direction of the IMU sensor coincides with the straight line of the attached bone;

[0018] The IMU sensors are secured to the ankle joint using elastic bands and buckles, with IMU sensors 1 and 3 used for measurement. Movement of the interphalangeal joints.

[0019] Wearable IMU sensors capture three-dimensional movements of the first metatarsal relative to the midfoot, including:

[0020] Three-dimensional motion capture of the first metatarsal relative to the midfoot: IMU sensor 4 is attached to the intermediate cuneiform bone, with the X-axis of the IMU sensor facing the direction of the course.

[0021] The IMU sensors are secured, and the control module corresponding to the IMU sensors is fixed to the ankle joint using elastic bands and buckles. IMU sensors 2 and 4 are used to measure the movement of the first metatarsal relative to the midfoot.

[0022] Analysis of foot movement data includes:

[0023] Analyze standing still data;

[0024] Analyze walking dynamic data.

[0025] Analysis of standing still data includes:

[0026] Data is recorded while the person is standing still. The accelerometer readings during this time are used to calculate the position of the bones and the static angles of the joints. α is the angle between the gravity line and the x-axis of the accelerometer, β is the angle between the gravity line and the y-axis of the accelerometer, and γ is the angle between the gravity line and the z-axis of the accelerometer.

[0027] According to the accelerometer (a x ,a y ,a z ) calculate

[0028]

[0029]

[0030] Based on α, β, and γ, the rotation matrix of the IMU sensor coordinate system relative to the world coordinate system when rotating in the order of x, y, z is calculated as follows:

[0031]

[0032] The static joint angles of two adjacent IMUs are calculated using the joint angle calculation method described by Suntay-Grood.

[0033] Analysis of walking dynamic data includes

[0034] Subjects walked continuously in a designated environment, either barefoot or wearing shoes, and dynamic data was recorded. Gyroscope data was used to calculate joint angles during the movement.

[0035] At any moment of motion, integrating the angular velocity yields the gyroscope's angular increment. This angular increment is then used to obtain the rotation matrix Rd of the IMU sensor relative to the world coordinate system. Rotating in the x, y, z order, the rotation matrix Rd represents the dynamic position relative to the static position. d ×R s =R, using the joint angle calculation method described by Suntay-Grood, the motion angle of the target joint during a gait cycle can be calculated.

[0036] A three-dimensional motion capture system for foot joints based on an IMU, comprising:

[0037] The data acquisition module is used to collect foot movement data using an IMU sensor;

[0038] The data processing module is used to analyze foot movement based on the collected foot movement data.

[0039] A computer device includes a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of any of the IMU-based three-dimensional motion capture methods for foot joints.

[0040] This invention develops a low-cost, portable method for three-dimensional motion capture of foot joints based on IMU sensors, which can measure the movement of small joints of the foot in real-life environments, whether barefoot or wearing shoes. Attached Figure Description

[0041] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a flowchart of the present invention;

[0044] Figure 2 This is a schematic diagram of the foot joint motion capture system of the present invention;

[0045] Figure 3 This is a schematic diagram of the IMU sensor worn by the present invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0048] Furthermore, the use of terms such as "first" and "second" in this invention is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" and "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0049] Current IMU sensors are used for 3D motion capture of large human joints, such as the shoulder, elbow, wrist, hip, knee, and ankle, but have not yet been applied to motion capture of small joints in the foot, especially when the foot is wearing shoes. Therefore, this invention aims to develop a low-cost, portable IMU sensor-based 3D motion capture system for foot joints that can measure the movement of small joints in the foot in real-life environments, whether barefoot or wearing shoes.

[0050] Example 1

[0051] A method for three-dimensional motion capture of foot joints based on IMU, reference Figure 1 ,include:

[0052] The S100 uses an IMU sensor to collect foot movement data;

[0053] S200 analyzes foot movement based on collected foot movement data.

[0054] This invention develops a low-cost, portable method for three-dimensional motion capture of foot joints based on IMU sensors, which can measure the movement of small joints of the foot in real-life environments, whether barefoot or wearing shoes.

[0055] The S100 uses an IMU sensor to collect foot movement data, including:

[0056] S101, wearable IMU sensor captures three-dimensional motion of the first metatarsophalangeal joint;

[0057] S102, wearable IMU sensor to capture three-dimensional movements of the interphalangeal joints;

[0058] S103 uses wearable IMU sensors to capture three-dimensional movements of the first metatarsal relative to the midfoot.

[0059] The S101 wearable IMU sensor captures three-dimensional movements of the first metatarsophalangeal joint, including:

[0060] Attach IMU sensor 1 to The IMU sensor 2 is attached to the middle section of the posterior surface of the first metatarsal bone in the middle segment of the proximal phalanx of the toe, with the X-axis direction of the IMU sensor coinciding with the line of the attached bone.

[0061] Secure each IMU sensor, and use elastic bands and buckles to fix the control module corresponding to the IMU sensor to the ankle joint.

[0062] The S102 wearable IMU sensor captures three-dimensional movements of the interphalangeal joints, including:

[0063] 3D motion capture of the interphalangeal joint: attaching the IMU sensor 3 to In the middle of the distal phalanx of the phalanx, the X-axis direction of the IMU sensor coincides with the straight line of the attached bone;

[0064] The IMU sensors are secured to the ankle joint using elastic bands and buckles, with IMU sensors 1 and 3 used for measurement. Movement of the interphalangeal joints.

[0065] The S103 wearable IMU sensor captures three-dimensional motion of the first metatarsal relative to the midfoot, including:

[0066] Three-dimensional motion capture of the first metatarsal relative to the midfoot: IMU sensor 4 is attached to the intermediate cuneiform bone, with the X-axis of the IMU sensor facing the direction of the course.

[0067] The IMU sensors are secured, and the control module corresponding to the IMU sensors is fixed to the ankle joint using elastic bands and buckles. IMU sensors 2 and 4 are used to measure the movement of the first metatarsal relative to the midfoot.

[0068] like Figure 3 .

[0069] The S200 analyzes foot movement based on the collected foot movement data, including:

[0070] S201 analyzes standing still data;

[0071] S202 analyzes walking dynamic data.

[0072] S201 analysis of standing still data includes:

[0073] Data is recorded while the person is standing still. The accelerometer readings during this time are used to calculate the position of the bones and the static angles of the joints. α is the angle between the gravity line and the x-axis of the accelerometer, β is the angle between the gravity line and the y-axis of the accelerometer, and γ is the angle between the gravity line and the z-axis of the accelerometer.

[0074] According to the accelerometer (a x ,a y ,a z ) calculate

[0075]

[0076]

[0077] Based on α, β, and γ, the rotation matrix of the IMU sensor coordinate system relative to the world coordinate system when rotating in the order of x, y, z is calculated as follows:

[0078]

[0079] The static joint angles of two adjacent IMUs are calculated using the joint angle calculation method described by Suntay-Grood.

[0080] S202 analyzes walking dynamic data including

[0081] Subjects walked continuously in a designated environment, either barefoot or wearing shoes, and dynamic data was recorded. Gyroscope data was used to calculate joint angles during the movement.

[0082] At any moment of motion, integrating the angular velocity yields the gyroscope's angular increment. This angular increment is then used to obtain the rotation matrix Rd of the IMU sensor relative to the world coordinate system. Rotating in the x, y, z order, the rotation matrix Rd represents the dynamic position relative to the static position. d ×R s =R, using the joint angle calculation method described by Suntay-Grood, the motion angle of the target joint during a gait cycle can be calculated.

[0083] Example 2

[0084] A foot joint three-dimensional motion capture system based on IMU, reference Figure 2 ,include:

[0085] The data acquisition module is used to collect foot movement data using an IMU sensor;

[0086] The data processing module is used to analyze foot movement based on the collected foot movement data.

[0087] Example 3

[0088] A computer device includes a memory and a processor, the memory storing a computer program, the processor executing the computer program to implement the steps of any of the IMU-based three-dimensional motion capture methods for foot joints.

[0089] This invention develops a low-cost, portable method for three-dimensional motion capture of foot joints based on IMU sensors, which can measure the movement of small joints of the foot in real-life environments, whether barefoot or wearing shoes.

[0090] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for three-dimensional motion capture of foot joints based on IMU, characterized in that, include: Foot movement data is collected using an IMU sensor; Analyze foot movement based on the collected foot movement data; The use of an IMU sensor to collect foot movement data includes: Wearable IMU sensors capture three-dimensional movements of the first metatarsophalangeal joint, including: Attach IMU sensor 1 to The IMU sensor 2 is attached to the middle section of the posterior surface of the first metatarsal bone in the middle segment of the proximal phalanx of the toe, with the X-axis direction of the IMU sensor coinciding with the line of the attached bone. Secure each IMU sensor, and use elastic bands and buckles to fix the control module corresponding to the IMU sensor to the ankle joint; Wearable IMU sensors capture three-dimensional movements of the interphalangeal joints, including: 3D motion capture of the interphalangeal joint: attaching the IMU sensor 3 to In the middle of the distal phalanx of the phalanx, the X-axis direction of the IMU sensor coincides with the straight line of the attached bone; Secure the IMU sensors by using elastic bands and buckles to fasten the corresponding control module to the ankle joint. IMU sensors 1 and 3 are used for measurement. Movement of the interphalangeal joints; Wearable IMU sensors capture three-dimensional movements of the first metatarsal relative to the midfoot, including: Three-dimensional motion capture of the first metatarsal relative to the midfoot: IMU sensor 4 is attached to the intermediate cuneiform bone, with the X-axis of the IMU sensor facing the direction of the course. Secure the IMU sensor and use elastic bands and buckles to fix the control module corresponding to the IMU sensor to the ankle joint. IMU sensors 2 and 4 are used to measure the movement of the first metatarsal relative to the midfoot. The analysis of foot movement based on the collected foot movement data includes: Analyze standing still data; Analyze walking dynamic data; The analysis of the static standing data includes: Data is recorded while the person is standing still. The accelerometer readings during this time are used to calculate the position of the bones and the static angles of the joints. α is the angle between the gravity line and the x-axis of the accelerometer, and β is the angle between the gravity line and the y-axis of the accelerometer. It is the angle between the gravity line and the z-axis of the accelerometer; According to the accelerometer Calculate the gravitational acceleration g= α= 、 β= ； According to α, β, The rotation matrix of the IMU sensor coordinate system relative to the world coordinate system when rotating in the order of x, y, z is calculated as follows: R s =RxRyRz= The static joint angles of two adjacent IMUs are calculated using the joint angle calculation method described by Suntay-Grood. The analyzed walking dynamic data includes: Subjects walked continuously in a designated environment, either barefoot or wearing shoes, and dynamic data was recorded. Gyroscope data was used to calculate joint angles during the movement. At any moment of motion, integrating the angular velocity yields the gyroscope's angular increment. This angular increment is then used to obtain the rotation matrix Rd of the IMU sensor relative to the world coordinate system, rotating in the x, y, z order. This is the rotation matrix of the dynamic position relative to the static position. The motion angles of the target joint during a gait cycle are calculated using the joint angle calculation method described by Suntay-Grood.

2. A foot joint three-dimensional motion capture system based on IMU, characterized in that, include: The data acquisition module is used to collect foot movement data using an IMU sensor; The data processing module is used to analyze foot movement based on the collected foot movement data; The use of an IMU sensor to collect foot movement data includes: Wearable IMU sensors capture three-dimensional movements of the first metatarsophalangeal joint, including: Attach IMU sensor 1 to The IMU sensor 2 is attached to the middle section of the posterior surface of the first metatarsal bone in the middle segment of the proximal phalanx of the toe, with the X-axis direction of the IMU sensor coinciding with the line of the attached bone. Secure each IMU sensor, and use elastic bands and buckles to fix the control module corresponding to the IMU sensor to the ankle joint; Wearable IMU sensors capture three-dimensional movements of the interphalangeal joints, including: 3D motion capture of the interphalangeal joint: attaching the IMU sensor 3 to In the middle of the distal phalanx of the phalanx, the X-axis direction of the IMU sensor coincides with the straight line of the attached bone; Secure the IMU sensors by using elastic bands and buckles to fasten the corresponding control module to the ankle joint. IMU sensors 1 and 3 are used for measurement. Movement of the interphalangeal joints; Wearable IMU sensors capture three-dimensional movements of the first metatarsal relative to the midfoot, including: Three-dimensional motion capture of the first metatarsal relative to the midfoot: IMU sensor 4 is attached to the intermediate cuneiform bone, with the X-axis of the IMU sensor facing the direction of the course. Secure the IMU sensor and use elastic bands and buckles to fix the control module corresponding to the IMU sensor to the ankle joint. IMU sensors 2 and 4 are used to measure the movement of the first metatarsal relative to the midfoot. The analysis of foot movement based on the collected foot movement data includes: Analyze standing still data; Analyze walking dynamic data; The analysis of the static standing data includes: Data is recorded while the person is standing still. The accelerometer readings during this time are used to calculate the position of the bones and the static angles of the joints. α is the angle between the gravity line and the x-axis of the accelerometer, and β is the angle between the gravity line and the y-axis of the accelerometer. It is the angle between the gravity line and the z-axis of the accelerometer; According to the accelerometer Calculate the gravitational acceleration g= α= 、 β= ； According to α, β, The rotation matrix of the IMU sensor coordinate system relative to the world coordinate system when rotating in the order of x, y, z is calculated as follows: R s =RxRyRz= The static joint angles of two adjacent IMUs are calculated using the joint angle calculation method described by Suntay-Grood. The analyzed walking dynamic data includes: Subjects walked continuously in a designated environment, either barefoot or wearing shoes, and dynamic data was recorded. Gyroscope data was used to calculate joint angles during the movement. At any moment of motion, integrating the angular velocity yields the gyroscope's angular increment. This angular increment is then used to obtain the rotation matrix Rd of the IMU sensor relative to the world coordinate system, rotating in the x, y, z order. This is the rotation matrix of the dynamic position relative to the static position. The motion angles of the target joint during a gait cycle are calculated using the joint angle calculation method described by Suntay-Grood.

3. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the IMU-based three-dimensional motion capture method for foot joints as described in claim 1.

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