A positioning method of knee, ankle, elbow joint function rotation axis

Abstract

The application relates to a knee, ankle, elbow joint function rotating shaft positioning method, which comprises the following steps: collecting human body action data, post-processing the human body action data, and establishing local coordinates of each segment of the human body based on the post-processed human body action data; based on the local coordinates of each segment of the human body, the spatial position of the knee, ankle, elbow joint function rotating shaft in a global coordinate system is obtained, and the positioning of the knee, ankle, elbow joint function rotating shaft is completed. The human body motion data captured through dynamic and static calibration technology is used to determine the local coordinates of each segment of the human body, so that the joint function rotating shaft of the knee, ankle and elbow is positioned, and the accuracy of the joint rotating shaft position is improved.

Description

Technical Field

[0001] This invention relates to the field of biomechanics, and in particular to a method for locating the functional rotation axis of the knee, ankle, and elbow joints. Background Technology

[0002] Currently, when establishing multi-rigid-body motion models of the human body, inertial measurement units (IMUs) are commonly used to collect human motion data and approximate the human body's posture, thereby creating a three-dimensional joint connection model that conforms to human behavioral characteristics. This technique is frequently used in the process of establishing multi-rigid-body motion models of the human body to create joint models for adjacent segments. However, the above technique often suffers from inconsistencies between the coordinate system of the IMU sensor and the coordinate system of the human segment, resulting in misalignment of the local coordinate axes of the IMU with the axes of the human segment, leading to inaccurate joint rotation axis positions.

[0003] Therefore, there is an urgent need for a method to locate the functional rotation axis of the knee, ankle, and elbow joints to solve the above-mentioned technical problems and improve the accuracy of the joint rotation axis position. Summary of the Invention

[0004] The purpose of this invention is to provide a method for locating the functional rotation axes of the knee, ankle, and elbow joints. By capturing human motion data through dynamic and static calibration techniques, the local coordinates of each segment of the human body are determined, thereby locating the functional rotation axes of the knee, ankle, and elbow joints and improving the accuracy of the joint rotation axis position.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A method for locating the functional rotation axis of the knee, ankle, and elbow joints, comprising:

[0007] Collect human motion data, post-process the human motion data, and establish local coordinates of each segment of the human body based on the post-processed human motion data;

[0008] Based on the local coordinates of each segment of the human body, the spatial positions of the functional rotation axes of the knee, ankle, and elbow joints in the global coordinate system are obtained, thus completing the positioning of the functional rotation axes of the knee, ankle, and elbow joints.

[0009] Furthermore, the method for collecting the human motion data includes:

[0010] Static calibration points and dynamic calibration point groups are set for each segment of the human body. Based on the optical motion capture system, the spatial positions of each calibration point in the global coordinate system under static and dynamic conditions are recorded respectively. The segments of the human body include the proximal segments and distal segments of the knee, ankle and elbow joints. The proximal segments of the knee, ankle and elbow joints include the thigh, lower leg and upper arm. The distal segments of the knee, ankle and elbow joints include the lower leg, foot and forearm.

[0011] Further, post-processing of the human motion data includes:

[0012] The human motion data is processed by interpolation algorithm to fill in missing points, and then filtered after the interpolation is performed.

[0013] Furthermore, based on the local coordinates of each segment of the human body, obtaining the spatial positions of the functional rotation axes of the knee, ankle, and elbow joints in the global coordinate system includes:

[0014] Based on the spatial position of each calibration point of the proximal segment in the global coordinate system, the spatial position of the static calibration point of the proximal segment in the global coordinate system under dynamic conditions is obtained.

[0015] Establish a local coordinate system for the proximal segment, obtain the spatial position of the local coordinate system for the proximal segment within the global coordinate system, and obtain the spatial position of the dynamic calibration point group of the distal segment within the local coordinate system for the proximal segment.

[0016] Based on the spatial position of the distal segment dynamic calibration point group in the local coordinate system of the proximal segment, the spatial positions of the knee, ankle, and elbow joint centers in the local coordinate system of the proximal segment and the spatial positions of the knee, ankle, and elbow joint centers in the global coordinate system are calculated. Combining the local coordinate system of the proximal segment, the spatial positions of the functional rotation axes of the knee, ankle, and elbow joints in the global coordinate system are calculated.

[0017] Furthermore, based on the spatial positions of each calibration point of the proximal segment in the global coordinate system, obtaining the spatial positions of the static calibration points of the proximal segment in the global coordinate system under dynamic conditions includes:

[0018] Obtain the spatial position v of the static calibration point of the proximal segment in the global coordinate system under static conditions. m ={x s ,y s ,z s The spatial positions of the dynamic calibration point group of the proximal segment and the proximal segment within the global coordinate system. Calculate the spatial position 'a' of the center of the dynamic calibration point group of the proximal segment under static conditions within the global coordinate system:

[0019]

[0020] Obtain the spatial position of the dynamic calibration point set of the proximal segment in the global coordinate system at a certain moment under dynamic conditions. Calculate the spatial position p of the center of the dynamic calibration point group of the proximal segment at a certain moment under dynamic conditions within the global coordinate system:

[0021]

[0022] Calculate the vector from the static position to the dynamic position of the center of the dynamic calibration point group of the proximal segment at a certain moment.

[0023]

[0024] Calculate the vector group A, which is the vector of each calibration point in the dynamic calibration point group of the proximal segment under static conditions, pointing to the center of the dynamic calibration point group, and the vector group B, which is the vector of each calibration point in the dynamic calibration point group of the proximal segment at a certain moment under dynamic conditions, pointing to the center of the dynamic calibration point group. Based on the vector groups A and B, obtain matrix C, C = B × A′. Perform singular value decomposition on matrix C to obtain the rotation matrix R of the dynamic calibration point group of the proximal segment.

[0025]

[0026] In the formula, P and Q are matrices obtained by performing singular value decomposition on matrix C;

[0027] Calculate the spatial position d of the static calibration point of the proximal segment in the global coordinate system under dynamic conditions. s :

[0028]

[0029] Furthermore, establishing the local coordinate system of the proximal segment includes:

[0030] Based on the human anatomy-based trunk and pelvic segmental skeletal system calibration technique, a local coordinate system for the proximal segment is established. The orientation of the axes of the proximal segment local coordinate system is... The origin of the local coordinate system is o = {x0 y0 z0}, and the direction vectors of the x, y, and z axes of the local coordinate system are (x1 y1 z1), (x2 y2 z2), and (x3 y3 z3), respectively.

[0031] Furthermore, obtaining the spatial position of the distal segment dynamic calibration point group within the proximal segment local coordinate system includes:

[0032] Obtain the spatial position v of the dynamic calibration point group of the distal segment in the global coordinate system. dg ={x d y d z d} Calculate the spatial position v of the distal segment dynamic calibration point group within the local coordinate system of the proximal segment. l :

[0033] v l =(A×(v′) dg -o))′

[0034] In the formula, A is the vector group pointing from each calibration point in the dynamic calibration point group of the proximal segment under static conditions to the center of the dynamic calibration point group, and o is the coordinate of the origin of the local coordinate system of the proximal segment.

[0035] Furthermore, calculating the spatial positions of the knee, ankle, and elbow joint centers within the local coordinate system of the proximal segment includes:

[0036] Obtain the spatial positions of the dynamic calibration point group in the local coordinate system of the proximal segment at different times, calculate the average value of the spatial positions of the dynamic calibration point group in the local coordinate system of the proximal segment at a certain time, and obtain the spatial position v of the joint center in the local coordinate system of the proximal segment. c :

[0037]

[0038] In the formula, v dl(i) v represents the position of the dynamic calibration point group within the local coordinate system of the proximal segment i during time t. mean(i) The average position of the proximal segment i calibration point group within time t.

[0039] Furthermore, the spatial positions of the centers of the knee, ankle, and elbow joints in the global coordinate system are as follows:

[0040] v cg =R′ i ×v′ c +a′ i =(x cg y cg z cg )

[0041] In the formula, v cg Let a be the spatial position of the joint center in the global coordinate system. i R represents the spatial position of the center of the dynamic calibration point group of proximal segment i in the global coordinate system under static conditions. i v is the rotation matrix of the dynamic calibration point group of proximal segment i at this moment. c Let be the spatial position of the joint center in the local coordinate system of the proximal segment i.

[0042] Furthermore, the spatial positions of the functional rotation axes of the knee, ankle, and elbow joints within the global coordinate system are as follows:

[0043]

[0044] In the formula, (x cg y cg z cg (x1 y1 z1) represents the spatial position of the joint center in the global coordinate system, and (x1 y1 z1) represents the x-axis direction of the local coordinate system.

[0045] The beneficial effects of this invention are as follows:

[0046] This invention uses dynamic and static calibration technology to capture human motion data and determine the local coordinates of each segment of the human body, thereby locating the joint function rotation axis of the knee, ankle, and elbow, which can improve the accuracy of the joint function rotation axis position calculation results. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a flowchart illustrating a method for locating the functional rotation axes of the knee, ankle, and elbow joints according to an embodiment of the present invention. Detailed Implementation

[0049] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] This embodiment provides a method for locating the functional rotation axis of the knee, ankle, and elbow joints, such as... Figure 1 As shown, it includes:

[0052] S1. Conduct motion capture experiments to collect human motion data.

[0053] S1.1. Set dynamic and static calibration points sequentially for the upper arm, forearm, thigh, lower leg, and foot.

[0054] Based on the human anatomy-based skeletal system calibration technique for the trunk, pelvis, and limb segments, static calibration points are established at anatomical locations on the upper arm, forearm, thigh, lower leg, and foot. Simultaneously, dynamic calibration point groups are established within these segments. Specifically:

[0055] (1) Determine the location of static calibration points for each segment based on the anatomical location of the trunk and limb segments;

[0056] (2) Set up calibration rods to determine the location of simulated static calibration points for pelvic segments;

[0057] (3) Make multiple calibration plates and set them at the required positions on the trunk, pelvis and limb segments. The calibration plates are equipped with multiple dynamic calibration points.

[0058] S1.2. Conduct static optical motion capture experiments

[0059] (1) Conduct static measurement experiments

[0060] Experimental subjects with static and dynamic calibration points at each segment are required to remain stationary, and the positions of each calibration point must be recorded. Experimental data includes the spatial position of each calibration point in the global coordinate system when stationary.

[0061] The experimental subject, with static and dynamic calibration points already set as required, must remain stationary. An optical motion capture system will be used to record the spatial position of each calibration point in the global coordinate system. The experimental data includes the spatial position of each calibration point in the global coordinate system during the experimental recording period.

[0062] (2) Conduct dynamic measurement experiments

[0063] Following the static measurement experiment, the experimental subject, with static and dynamic calibration points set as required, underwent a dynamic measurement experiment. The subject was required to maintain the proximal segment (thigh, lower leg, upper arm) posture unchanged, while moving the distal segment (lower leg, foot, forearm) to induce flexion and extension movements of the joints. The spatial positions of each calibration point on the proximal and distal segments within the global coordinate system were recorded. The experimental data included the spatial position of each calibration point within the global coordinate system during the experimental recording time period.

[0064] S2. Post-processing of experimental data

[0065] S2.1. Add data points

[0066] During the experiment, some markers will inevitably be lost for a short period of time. Therefore, an interpolation algorithm needs to be used in the software to fill in the spatial positions of the markers lost during that period.

[0067] During the experiment, due to less-than-ideal experimental conditions (such as interference from reflective objects), some calibration points may be lost for a short period or become interfering. An interpolation algorithm needs to be used in the software to fill in the spatial positions of the calibration points during the lost capture time. If the continuous loss time exceeds 20 frames, the measurement needs to be repeated.

[0068] S2.2 is for data filtering.

[0069] During the experiment, fluctuations in experimental data may occur due to insufficient experimental conditions. To smooth the optical motion capture data, a first-order Butterworth low-pass filter with a cutoff frequency of 6Hz is used as the filter for supplementing the optical motion capture data.

[0070] S3. Locate the functional rotation axes of the knee, ankle, and elbow joints based on the established local coordinates of each segment of the human body.

[0071] S3.1. Calculate the spatial position of the static calibration point of the proximal segment in the global coordinate system.

[0072] (1) Read the static measurement experimental data of each proximal segment (thigh, lower leg, upper arm), and read the spatial position of the static calibration point of the segment in the global coordinate system as v. m ={x s ,y s ,z s The spatial positions of each point in the dynamic calibration point group of this segment within the global coordinate system are: Among them, v m This is the position of the static calibration point in the global coordinate system, and the coordinates of this calibration point are {x}. s ,y s ,z s};v s To define the positions of the four calibration points in the dynamic calibration point group within the global coordinate system during the static measurement experiment, the coordinates of the four calibration points are: {x} s1 y s1 z s1}、{x s2 y s2 z s2}、{x s3 y s3 z s3}、{x s4 y s4 z s4}

[0073] (2) Read the dynamic measurement experimental data of each proximal segment (thigh, lower leg, upper arm), and read the spatial position of the dynamic calibration point group of that segment in the global coordinate system. Among them, v d The coordinates of the four calibration points in the dynamic calibration point group are given in the global coordinate system at a certain moment during the dynamic measurement experiment. The coordinates of the four calibration points are: v d1 ={x d1 y d1 z d1}、v d2 ={x d2 y d2 z d2}、vd3 ={x d3 y d3 z d3}、v d4 ={x d4 y d4 z d4}

[0074] (3) Calculate the spatial position of the segment in the global coordinate system during the dynamic measurement experiment.

[0075] Calculating rotation matrices using singular value decomposition

[0076] 'a' represents the position of the center of the dynamic calibration point group in the global coordinate system during the static measurement experiment.

[0077]

[0078] p is the position of the center of the dynamic calibration point set in the global coordinate system at a certain moment during the dynamic measurement experiment.

[0079]

[0080] The vector pointing from the position of the center of the dynamic calibration point group at a certain moment to its position in the dynamic measurement experiment at that moment.

[0081]

[0082] A is a vector group of four calibration points pointing towards the center of the calibration point group in a static experiment.

[0083]

[0084] B is a vector group of four calibration points pointing towards the center of the calibration point group at a certain moment in the dynamic experiment.

[0085]

[0086] C = B × A'

[0087] Singular value decomposition of matrix C yields matrix P. 3×3 and Q 4×4

[0088] P 3×3 T 3×4 Q 4×4 =C 3×4

[0089] R is the rotation matrix of the segment containing the dynamic calibration point group at that moment.

[0090]

[0091] Calculate the spatial position of the static marker point of this segment in the global coordinate system.

[0092]

[0093] S3.2. Establish a local coordinate system for the proximal segment and calculate its position within the global coordinate system.

[0094] Based on the human anatomy-based trunk and pelvic segmental skeletal system calibration technique, static calibration point positions are set, along with midpoints, auxiliary points, and auxiliary vectors. The origin of the proximal segment local coordinate system is located, and the direction of the auxiliary vector is determined to be the direction of the proximal segment coordinate system. Thus, a proximal segment local coordinate system is established, with the axes oriented as follows: The position coordinates of the origin of the local coordinate system in the global coordinate system are o = {x0 y0 z0}. The direction vectors of the x, y, and z axes of the local coordinate system in the global coordinate system are (x1 y1 z1), (x2 y2 z2), and (x3 y3 z3), respectively.

[0095] S3.3. Calculate the position of the dynamic calibration point set of the distal segment in the local coordinate system of the proximal segment.

[0096] The spatial position of the acquired remote segment dynamic calibration point in the global coordinate system is v dg ={x d y d z d The location of this calibration point in the local coordinate system of the proximal segment is v. l =(A×(v′) dg -o))′.

[0097] S3.4. Calculate the position of the joint rotation center in the local coordinate system of the proximal segment.

[0098] The calculated positions of the dynamic calibration point group within the local coordinate system of the proximal segment i during time t are as follows:

[0099] v dl(i) =(v d1,i,t v d2,i,t v d3,i,t v d4,i,t )

[0100]

[0101]

[0102]

[0103]

[0104] The average position of the calibration point group of segment i within time t is:

[0105]

[0106] The position of the joint center in the local coordinate system of the proximal segment i is:

[0107]

[0108] S3.5. Calculate the spatial position of the joint center in the global coordinate system.

[0109] The rotation matrix of the proximal segment i of joint j can be calculated as R. i The position of the joint center in the global coordinate system is:

[0110] v cg =R′ i ×v′ c +a′ i =(x cg y cg z cg )

[0111] S3.6. Calculate the spatial position of the joint's rotation axis in the global coordinate system.

[0112] Based on the human anatomy-based trunk and pelvic segmental skeletal system calibration technique, a local coordinate system for this segment has been established. The directions of the local coordinate system axes are... Its x-axis direction is A x = (x1 y1 z1).

[0113] The spatial position of the joint's rotation axis in the global coordinate system is:

[0114]

[0115] In the formula, (x cg y cg z cg (x1 y1 z1) represents the spatial position of the joint center in the global coordinate system, and (x1 y1 z1) represents the x-axis direction of the local coordinate system.

[0116] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for locating the functional rotation axis of the knee, ankle, and elbow joints, characterized in that, include: Collect human motion data, post-process the human motion data, and establish local coordinates of each segment of the human body based on the post-processed human motion data; Based on the local coordinates of each segment of the human body, the spatial positions of the functional rotation axes of the knee, ankle, and elbow joints in the global coordinate system are obtained, thus completing the positioning of the functional rotation axes of the knee, ankle, and elbow joints. Based on the local coordinates of each segment of the human body, the spatial positions of the functional rotation axes of the knee, ankle, and elbow joints in the global coordinate system are obtained, including: Based on the spatial position of each calibration point of the proximal segment in the global coordinate system, the spatial position of the static calibration point of the proximal segment in the global coordinate system under dynamic conditions is obtained. Establish a local coordinate system for the proximal segment, obtain the spatial position of the local coordinate system for the proximal segment within the global coordinate system, and obtain the spatial position of the dynamic calibration point group of the distal segment within the local coordinate system for the proximal segment. Based on the spatial position of the distal segment dynamic calibration point group in the local coordinate system of the proximal segment, the spatial positions of the knee, ankle, and elbow joint centers in the local coordinate system of the proximal segment and the spatial positions of the knee, ankle, and elbow joint centers in the global coordinate system are calculated. Combining the local coordinate system of the proximal segment, the spatial positions of the functional rotation axes of the knee, ankle, and elbow joints in the global coordinate system are calculated. Based on the spatial positions of each calibration point of the proximal segment in the global coordinate system, obtaining the spatial positions of the static calibration points of the proximal segment in the global coordinate system under dynamic conditions includes: Obtain the spatial position of the static calibration point of the proximal segment in the global coordinate system under static conditions. The spatial position of the dynamic calibration point group of the proximal segment within the global coordinate system Calculate the spatial position of the center of the dynamic calibration point group of the proximal segment in the global coordinate system under static conditions. : Obtain the spatial position of the dynamic calibration point set of the proximal segment in the global coordinate system at a certain moment under dynamic conditions. Calculate the spatial position of the center of the dynamic calibration point group of the proximal segment in the global coordinate system at a certain moment under dynamic conditions. : Calculate the vector from the static position to the dynamic position of the center of the dynamic calibration point group of the proximal segment at a certain moment. : Calculate the vector set pointing from each calibration point in the dynamic calibration point set of the proximal segment under static conditions to the center of the dynamic calibration point set. And the vector group pointing from each calibration point in the dynamic calibration point group of the proximal segment at a certain moment under dynamic conditions to the center of the dynamic calibration point group. Based on vector groups and Get matrix , For the matrix Perform singular value decomposition to obtain the rotation matrix of the dynamic calibration point set of the proximal segment. ; In the formula, P , Q For matrix The matrix obtained by performing singular value decomposition; Calculate the spatial position of the static calibration point of the proximal segment in the global coordinate system under dynamic conditions. : 。 2. The method for locating the functional rotation axis of the knee, ankle, and elbow joints according to claim 1, characterized in that, The methods for collecting the human motion data include: Static calibration points and dynamic calibration point groups are set for each segment of the human body. Based on the optical motion capture system, the spatial positions of each calibration point in the global coordinate system under static and dynamic conditions are recorded respectively. The segments of the human body include the proximal segments and distal segments of the knee, ankle and elbow joints. The proximal segments of the knee, ankle and elbow joints include the thigh, lower leg and upper arm. The distal segments of the knee, ankle and elbow joints include the lower leg, foot and forearm.

3. The method for locating the functional rotation axis of the knee, ankle, and elbow joints according to claim 1, characterized in that, Post-processing of the human motion data includes: The human motion data is processed by interpolation algorithm to fill in missing points, and then filtered after the interpolation is performed.

4. The method for locating the functional rotation axis of the knee, ankle, and elbow joints according to claim 1, characterized in that, Establishing the local coordinate system of the proximal segment includes: Based on the human anatomy-based trunk and pelvic segmental skeletal system calibration technique, a local coordinate system for the proximal segment is established. The orientation of the axes of the proximal segment local coordinate system is... The coordinates of the origin of the local coordinate system are Local coordinate system The direction vectors of the axes are respectively .

5. The method for locating the functional rotation axis of the knee, ankle, and elbow joints according to claim 1, characterized in that, Obtaining the spatial position of the distal segment dynamic calibration point group within the proximal segment local coordinate system includes: Obtain the spatial position of the dynamic calibration point group of the distal segment within the global coordinate system. Calculate the spatial position of the dynamic calibration point set of the distal segment within the local coordinate system of the proximal segment. : In the formula, A This is a set of vectors pointing from each calibration point in the dynamic calibration point set of the proximal segment under static conditions to the center of the dynamic calibration point set. The coordinates are the origin of the local coordinate system for the proximal segment.

6. The method for locating the functional rotation axis of the knee, ankle, and elbow joints according to claim 1, characterized in that, Calculating the spatial positions of the knee, ankle, and elbow joint centers within the local coordinate system of the proximal segment includes: Obtain the spatial positions of the dynamic calibration point group in the local coordinate system of the proximal segment at different times, calculate the average value of the spatial positions of the dynamic calibration point group in the local coordinate system of the proximal segment at a certain time, and obtain the spatial position of the joint center in the local coordinate system of the proximal segment. : In the formula, vdl ( i) For time t Internal dynamic calibration point group in the proximal segment i Position within the local coordinate system vmean ( i (time) t inner proximal segment i The average position of the calibration point group.

7. The method for locating the functional rotation axis of the knee, ankle, and elbow joints according to claim 1, characterized in that, The spatial positions of the centers of the knee, ankle, and elbow joints in the global coordinate system are as follows: In the formula, This represents the spatial position of the joint center within the global coordinate system. For the proximal segment under static conditions i The spatial position of the center of the dynamic calibration point group within the global coordinate system. For proximal segment i The rotation matrix of the dynamic calibration point group at that moment. The joint center is in the proximal segment i Spatial position within a local coordinate system.

8. The method for locating the functional rotation axis of the knee, ankle, and elbow joints according to claim 1, characterized in that, The spatial positions of the functional rotation axes of the knee, ankle, and elbow joints in the global coordinate system are as follows: In the formula, This represents the spatial position of the joint center within the global coordinate system. Local coordinate system axes x Axial direction.

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