A method for analyzing human lower limb movement posture

Abstract

This invention discloses a method for analyzing the motion posture of the human lower limbs, relating to the field of human signal acquisition and analysis technology. The method includes the following steps: acquiring multi-source signals from the lower limbs using multiple inertial measurement units; calculating multiple second initial posture quaternions based on posture vectors and posture angles; obtaining multiple third initial posture quaternions based on multiple first and second initial posture quaternions; obtaining multiple third real-time posture quaternions based on multiple first and second real-time posture quaternions; obtaining multiple floating axes for multiple joints based on the multiple third real-time posture quaternions; and obtaining the motion angles of multiple joints in the sagittal, coronal, and horizontal planes based on the multiple floating axes. This invention effectively avoids the errors caused by using inertial data to solve for joint angles. Based on floating axes, it can accurately calculate the three-dimensional joint angles of the lower limbs during real-time motion, while also exhibiting good repeatability.

Description

Technical Field

[0001] This invention relates to the field of human signal acquisition and analysis technology, and in particular to a method for analyzing the movement posture of the human lower limbs. Background Technology

[0002] Modern medical research shows that the range of changes in lower limb joint angles during human movement can accurately reflect the differences in the biomechanical characteristics of lower limb movement among individuals. Therefore, accurately detecting and analyzing the joint angles of the human lower limbs is of great significance for obtaining biomechanical parameters of different individuals. By comparing and analyzing the joint angles with data from normal individuals, it is possible to determine whether the function of the human lower limbs is normal.

[0003] Regarding the acquisition and analysis of multi-source signals from the human lower limbs, existing technologies include two main acquisition schemes. One is a multi-source signal acquisition scheme based on optical motion capture systems and force plates using marker points. This scheme has high sensitivity, good repeatability, and stability. However, the high cost and limited use of optical motion capture systems and force plates restricts its application to laboratory settings. The other is based on inertial motion capture systems. These systems typically consist of multiple inertial sensors and host computer software for data analysis and computation. They offer advantages such as being unrestricted by location, portability, good dynamic performance, and low cost. However, current joint angle calculation algorithms based on inertial sensors still have larger errors compared to optical motion capture systems, indicating significant room for improvement in inertial motion capture systems. Summary of the Invention

[0004] This invention provides a method for analyzing the movement posture of the human lower limbs, which can solve the problem that the joint angle calculation algorithm based on inertial sensors in the prior art still has a large error compared with the optical motion capture system.

[0005] This invention provides a method for analyzing the movement posture of the human lower limbs, comprising the following steps:

[0006] Multiple sources of signals from the lower limbs are acquired by multiple inertial measurement units. The multiple sources of signals include multiple first initial attitude quaternions and first real-time attitude quaternions of the multiple inertial measurement units relative to the geodetic coordinate system.

[0007] Based on the first initial attitude quaternion, define the attitude angle and attitude vector;

[0008] Calculate multiple second initial attitude quaternions of multiple body segments of the lower limb relative to the geodetic coordinate system based on attitude vectors and attitude angles;

[0009] Multiplying multiple first initial attitude quaternions and multiple second initial attitude quaternions together yields multiple third initial attitude quaternions for multiple inertial measurement units relative to multiple body segments.

[0010] Multiple second real-time attitude quaternions of multiple inertial measurement units relative to multiple body segments are obtained based on multiple third initial attitude quaternions;

[0011] Divide multiple second real-time attitude quaternions and multiple first real-time attitude quaternions to obtain multiple third real-time attitude quaternions of multiple body segments relative to the geodetic coordinate system.

[0012] Calculate the rotation matrix of multiple third real-time pose quaternions, and obtain multiple floating axes of multiple joints based on the rotation matrix of multiple third real-time pose quaternions;

[0013] Based on the rotation matrix of multiple floating axes and multiple third real-time attitude quaternions, the motion angles of multiple joints in the sagittal, coronal, and horizontal planes are obtained.

[0014] Preferably, the plurality of inertial measurement units include:

[0015] The pelvic inertial measurement unit is fixedly installed at the hip joint on the back, parallel to the coronal plane of the human body.

[0016] The thigh inertial measurement unit is fixedly positioned at the contour of the thigh projected onto the coronal plane, at a position equidistant from the hip and knee joints.

[0017] The lower leg inertial measurement unit is fixedly set at the contour position of the lower leg projected onto the coronal plane, and this position is equidistant from the vertical distance of the knee joint and the ankle joint;

[0018] The foot inertial measurement unit is fixedly positioned at the center of the instep, parallel to the sagittal plane.

[0019] Preferably, each of the inertial measurement units includes an inertial sensor, a microcontroller, and a Bluetooth module. The inertial sensor and the Bluetooth module are both electrically connected to the microcontroller. The inertial sensor includes a triaxial accelerometer, a gyroscope, and a magnetometer.

[0020] Preferably, the multiple first initial attitude quaternions of the multiple inertial measurement units relative to the geodetic coordinate system include the first initial attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system. The first initial attitude quaternion of the thigh inertial measurement unit relative to the geodetic coordinate system The first initial attitude quaternion of the lower leg inertial measurement unit relative to the geodetic coordinate system The first initial attitude quaternion of the foot inertial measurement unit relative to the geodetic coordinate system Multiple first real-time attitude quaternions of multiple inertial measurement units relative to the geodetic coordinate system, including the first real-time attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system. First real-time attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system First real-time attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system The first real-time attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system

[0021] Preferably, defining the attitude angle and attitude vector based on the first initial attitude quaternion includes the following steps:

[0022] Obtain the first initial attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system.

[0023] Will Substituting into the quaternion to rotation matrix formula yields the first rotation matrix.

[0024] according to Calculate the x-axis direction in the coordinate system of the first inertial measurement module.

[0025] definition With unit gravity vector z g The angle between them is the attitude angle θ;

[0026] Defined as perpendicular to vector x IMU1_2_G and the unit gravity vector z g The vector is the attitude vector n1;

[0027] The attitude angle θ is calculated using the following formula:

[0028] θ = acos(2(xz+wy))

[0029] The attitude vector n1 is calculated using the following formula:

[0030] n1=[2(xy+wz),y 2 +z 2 -w 2 -x 2 ,0] T

[0031]

[0032] In the formula, w, x, y, and z are respectively The constituent elements.

[0033] Preferably, multiple second initial attitude quaternions of multiple body segments relative to the geodetic coordinate system are calculated using the following formula:

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041] In the formula, It is the second initial attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system. It is the second initial attitude quaternion of the thigh inertial measurement unit relative to the geodetic coordinate system. It is the second initial attitude quaternion of the lower leg inertial measurement unit relative to the geodetic coordinate system. q(θ,n1) is the second initial attitude quaternion of the foot inertial measurement unit relative to the geodetic coordinate system, and q(θ,n1) is the quaternion rotated by an angle θ around the vector n1.

[0042] Preferably, the multiple third initial attitude quaternions of multiple inertial measurement units relative to multiple body segments are calculated by the following formula:

[0043]

[0044] In the formula, It consists of multiple third initial attitude quaternions for multiple inertial measurement units relative to multiple body segments. It consists of multiple second initial attitude quaternions for multiple body segments relative to the geodetic coordinate system. It consists of multiple first initial attitude quaternions of multiple inertial measurement units relative to the geodetic coordinate system.

[0045] Preferably, multiple third real-time attitude quaternions of multiple body segments relative to the geodetic coordinate system are obtained by the following formula:

[0046]

[0047] In the formula, It consists of multiple second real-time attitude quaternions of multiple inertial measurement units relative to multiple body segments. It consists of multiple third real-time attitude quaternions for multiple body segments relative to the geodetic coordinate system. It consists of multiple first real-time attitude quaternions of multiple inertial measurement units relative to the geodetic coordinate system.

[0048] Preferably, multiple floating axes of multiple joints are calculated using the following formula:

[0049]

[0050]

[0051]

[0052] In the formula, e Hip It is the floating axis of the hip joint, e Knee It is the floating axis of the knee joint, e Ankle It is the floating axis of the ankle joint, |·| denotes normalization, and i, j, and k represent the unit vectors in the x, y, and z directions, respectively. It is the third real-time attitude quaternion of the pelvis relative to the geodetic coordinate system. It is the third real-time attitude quaternion of the thigh relative to the Earth coordinate system. It is the third real-time attitude quaternion of the lower leg relative to the Earth coordinate system. R(*) is the third real-time attitude quaternion of the foot relative to the geodetic coordinate system, and R(*) represents the rotation matrix of a certain quaternion.

[0053] Preferably, the motion angles of multiple joints in the sagittal, coronal, and horizontal planes are calculated using the following formula:

[0054]

[0055]

[0056]

[0057]

[0058]

[0059]

[0060]

[0061]

[0062]

[0063] In the formula, α1 represents the angle of motion of the hip joint in the sagittal plane, β1 represents the angle of motion of the knee joint in the sagittal plane, γ1 represents the angle of motion of the ankle joint in the sagittal plane, α2 represents the angle of motion of the hip joint in the coronal plane, β2 represents the angle of motion of the knee joint in the coronal plane, γ2 represents the angle of motion of the ankle joint in the coronal plane, α3 represents the angle of motion of the hip joint in the horizontal plane, β3 represents the angle of motion of the knee joint in the horizontal plane, and γ3 represents the angle of motion of the ankle joint in the horizontal plane.

[0064] Compared with the prior art, the beneficial effects of the present invention are:

[0065] This invention provides a method for analyzing the movement posture of the human lower limbs. It can determine the position of each inertial sensor relative to the body segment based on the initial posture quaternions of the lower limbs over a short period, overcoming the shortcomings of current methods such as excessively long sensor calibration time and inaccurate sensor positioning. Furthermore, the sensor positions no longer require specific specifications. By using real-time quaternion data to predict the floating rotation axes and reference axes of the hip, knee, and ankle joints in the sagittal, coronal, and horizontal planes, it effectively avoids errors caused by using inertial data to solve joint angles. Based on the floating rotation axes, it can accurately calculate the three-dimensional joint angles of the lower limbs during real-time movement, while also exhibiting good repeatability, making it particularly suitable for application in the field of human movement posture calculation. Attached Figure Description

[0066] 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, 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.

[0067] Figure 1 A flowchart illustrating a method for analyzing the movement posture of the human lower limbs according to the present invention;

[0068] Figure 2 This is a schematic diagram of the structure of the inertial measurement unit of the present invention;

[0069] Figure 3 This is a schematic diagram of multiple inertial measurement units worn according to the present invention;

[0070] Figure 4 This is a flowchart of a method for analyzing the movement posture of the human lower limbs according to the present invention;

[0071] Figure 5 This is a schematic diagram illustrating the data processing of combining the data from this invention with data from existing plantar pressure detection systems.

[0072] In the diagram: 1-Pelvic inertial measurement unit, 2-Thigh inertial measurement unit, 3-Lower leg inertial measurement unit, 4-Foot inertial measurement unit. Detailed Implementation

[0073] 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.

[0074] Reference Figure 1 This invention provides a method for analyzing the movement posture of the human lower limbs, comprising the following steps:

[0075] Step 1: Multi-source signal acquisition of the lower limbs is performed through multiple inertial measurement units, including multiple first initial attitude quaternions and first real-time attitude quaternions of multiple inertial measurement units relative to the geodetic coordinate system.

[0076] Reference Figure 3 Multiple inertial measurement units (IMUs) are included, comprising a pelvic IMU 1, a thigh IMU 2, a lower leg IMU 3, and a foot IMU 4. Each IMU is fixed to a specific anatomical position using elastic straps 6. The pelvic IMU 1 is fixed at the hip joint on the back, parallel to the coronal plane of the human body. The thigh IMU 2 is fixed at the contour of the thigh projected onto the coronal plane, equidistant from the hip and knee joints. The lower leg IMU 3 is fixed at the contour of the lower leg projected onto the coronal plane, equidistant from the knee and ankle joints. The foot IMU 4 is fixed at the center of the dorsum of the foot, parallel to the sagittal plane.

[0077] Reference Figure 2 and Figure 4Each inertial measurement unit (IMU) includes an inertial sensor, a microcontroller, and a Bluetooth module. Each inertial sensor contains a three-axis accelerometer, a gyroscope, and a magnetometer. Before measurement begins, magnetic field calibration is required to correct for unknown electromagnetic interference and remap the magnetic field of the sensor. If magnetic field calibration fails, it must be recalibrated. After successful calibration, the heading angle needs to be reset to align the heading angle outputs of all IMUs. Because each IMU uses a separate clock domain, time synchronization allows measurement data from different IMUs to be synchronized to a common time domain. This effectively avoids time differences between different sensors when measuring joint angles. After time synchronization, the system can begin data acquisition. The microcontroller uses strapdown integration to obtain quaternion data for solving joint angles from the acceleration and angular velocity measured by the accelerometer and gyroscope, as well as the magnetometer data after Kalman filtering. This quaternion data is then sent to the Bluetooth module. The microcontroller receives the Bluetooth module's transmit / receive commands and sends the quaternion data to the human lower limb multi-source signal fusion analysis system for joint angle calculation. The calculation process is as follows:

[0078] The acquired first initial attitude quaternions of multiple inertial measurement units relative to the geodetic coordinate system include the first initial attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system. The first initial attitude quaternion of the thigh inertial measurement unit relative to the geodetic coordinate system The first initial attitude quaternion of the lower leg inertial measurement unit relative to the geodetic coordinate system The first initial attitude quaternion of the foot inertial measurement unit relative to the geodetic coordinate system Multiple first real-time attitude quaternions of multiple inertial measurement units relative to the geodetic coordinate system, including the first real-time attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system. First real-time attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system First real-time attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system The first real-time attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system

[0079] Step 2: Define the attitude angle and attitude vector.

[0080] Before starting real-time joint angle calculation, multiple initial quaternion data points from the first 5 seconds of static standing state are used to determine the sensor offset from the body, effectively solving the shortcomings of excessively long sensor calibration time and inaccurate sensor positioning. First, the quaternions collected by pelvic inertial measurement unit 1 need to be extracted, and the average value is calculated to obtain the quaternion representing the initial posture. The formula for quaternion to rotation matrix is ​​obtained. The x-axis direction in the coordinate system of pelvic inertial measurement unit 1 is expressed as (x IMU1_2_G );

[0081]

[0082] definition With unit gravity vector z g The angle between them is called the attitude angle θ, which is calculated using the following formula:

[0083] θ=acos(2(xz+wy)) (2)

[0084] Defined as perpendicular to vector x IMU1_2_G and the unit gravity vector z g The vector is the attitude vector n1, which is calculated using the following formula:

[0085] n1=[2(xy+wz),y 2 +z 2 -w 2 -x 2 ,0] T

[0086]

[0087] In the formula, w, x, y, and z are respectively The constituent elements.

[0088] Based on Euler's rotation theorem, a rotation of θ around vector n1 is represented by the quaternion q(θ,n1):

[0089]

[0090] Step 3: Calculate multiple second initial attitude quaternions for multiple body segments relative to the geodetic coordinate system based on the attitude vectors and attitude angles. The multiple second initial attitude quaternions for multiple body segments relative to the geodetic coordinate system are calculated using the following formula:

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] In the formula, It is the second initial attitude quaternion of the pelvic inertial measurement unit relative to the geodetic coordinate system. It is the second initial attitude quaternion of the thigh inertial measurement unit relative to the geodetic coordinate system. It is the second initial attitude quaternion of the lower leg inertial measurement unit relative to the geodetic coordinate system. q(θ,n1) is the second initial attitude quaternion of the foot inertial measurement unit relative to the geodetic coordinate system, and q(θ,n1) is the quaternion rotated by an angle θ around the vector n1.

[0098] Step 4: Based on multiple first initial attitude quaternions and multiple second initial attitude quaternions, obtain multiple third initial attitude quaternions for multiple inertial measurement units relative to multiple body segments. The multiple third initial attitude quaternions for multiple inertial measurement units relative to multiple body segments are calculated using the following formula:

[0099]

[0100] In the formula, It consists of multiple third initial attitude quaternions for multiple inertial measurement units relative to multiple body segments. It consists of multiple second initial attitude quaternions for multiple body segments relative to the geodetic coordinate system. It consists of multiple first initial attitude quaternions of multiple inertial measurement units relative to the geodetic coordinate system.

[0101] The placement of the sensor does not affect the solution of the attitude quaternion.

[0102] Step 5: Obtain multiple second real-time attitude quaternions for multiple inertial measurement units (IMUs) relative to multiple body segments based on multiple third initial attitude quaternions. During the wearing process, the relative positions of the IMUs and each body segment do not change; therefore, the real-time quaternion of each IMU installed in a body segment relative to the bound body segment is equal to the initial attitude quaternion, i.e.:

[0103]

[0104]

[0105]

[0106]

[0107] In the formula and These represent the second real-time attitude quaternions of the IMUs installed at the pelvis, thigh, calf, and foot positions relative to the bound body segments.

[0108] Step 6: Based on multiple first real-time attitude quaternions and multiple second real-time attitude quaternions, obtain multiple third real-time attitude quaternions for multiple body segments relative to the geodetic coordinate system. The multiple third real-time attitude quaternions for multiple body segments relative to the geodetic coordinate system are obtained using the following formula:

[0109]

[0110] In the formula, It consists of multiple second real-time attitude quaternions of multiple inertial measurement units relative to multiple body segments. It consists of multiple third real-time attitude quaternions for multiple body segments relative to the geodetic coordinate system. It consists of multiple first real-time attitude quaternions of multiple inertial measurement units relative to the geodetic coordinate system.

[0111] Step 7: Obtain multiple floating axes for multiple joints based on multiple third real-time pose quaternions. Calculate the multiple floating axes for multiple joints using the following formula:

[0112]

[0113] In the formula, e Hip It is the floating axis of the hip joint, e Knee It is the floating axis of the knee joint, e Ankle It is the floating axis of the ankle joint, |·| denotes normalization, and i, j, and k represent the unit vectors in the x, y, and z directions, respectively. It is the third real-time attitude quaternion of the pelvis relative to the geodetic coordinate system. It is the third real-time attitude quaternion of the thigh relative to the Earth coordinate system. It is the third real-time attitude quaternion of the lower leg relative to the Earth coordinate system. R(*) is the third real-time attitude quaternion of the foot relative to the geodetic coordinate system, and R(*) represents the rotation matrix of a certain quaternion.

[0114] Step 8: Obtain the motion angles of multiple joints in the sagittal, coronal, and horizontal planes based on multiple floating axes. Calculate the motion angles of multiple joints in the sagittal, coronal, and horizontal planes using the following formula:

[0115]

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123]

[0124] In the formula, α1 represents the angle of motion of the hip joint in the sagittal plane, β1 represents the angle of motion of the knee joint in the sagittal plane, γ1 represents the angle of motion of the ankle joint in the sagittal plane, α2 represents the angle of motion of the hip joint in the coronal plane, β2 represents the angle of motion of the knee joint in the coronal plane, γ2 represents the angle of motion of the ankle joint in the coronal plane, α3 represents the angle of motion of the hip joint in the horizontal plane, β3 represents the angle of motion of the knee joint in the horizontal plane, and γ3 represents the angle of motion of the ankle joint in the horizontal plane.

[0125] After completing the above analysis of lower limb joint angles, the data is compared with the gait data of normal human lower limbs to obtain the dynamic state of the wearer's lower limbs.

[0126] Example

[0127] Reference Figure 5 This invention combines lower limb joint angle analysis data with existing plantar pressure detection systems that can display torque, enabling simultaneous detection, online calculation, wireless transmission, visual display, and data analysis and storage of lower limb joint movement angles, plantar pressure, and torque during walking. It provides data support for analyzing changes in lower limb joint force and torque, and can be widely applied in fields such as medical and rehabilitation equipment research and development and evaluation, showing promising application prospects.

[0128] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0129] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method of analyzing a motion posture of a lower extremity of a human body, characterized by, The method comprises the following steps: Collecting multi-source signals of the lower limbs by a plurality of inertial measurement units, the multi-source signals comprising a plurality of first initial attitude quaternions and first real-time attitude quaternions of the plurality of inertial measurement units relative to a geodetic coordinate system; Defining an attitude angle and an attitude vector according to the first initial attitude quaternions; Calculating a plurality of second initial attitude quaternions of a plurality of body segments of the lower limbs relative to the geodetic coordinate system according to the attitude vector and the attitude angle; Multiplying the plurality of first initial attitude quaternions and the plurality of second initial attitude quaternions to obtain a plurality of third initial attitude quaternions of the plurality of inertial measurement units relative to the plurality of body segments; Obtaining a plurality of second real-time attitude quaternions of the plurality of inertial measurement units relative to the plurality of body segments according to the plurality of third initial attitude quaternions; Dividing the plurality of second real-time attitude quaternions by the plurality of first real-time attitude quaternions to obtain a plurality of third real-time attitude quaternions of the plurality of body segments relative to the geodetic coordinate system; Calculating a rotation matrix of the plurality of third real-time attitude quaternions to obtain a plurality of floating axes of a plurality of joints according to the rotation matrix of the plurality of third real-time attitude quaternions; Obtaining movement angles of the plurality of joints in a sagittal plane, a coronal plane and a horizontal plane according to the plurality of floating axes and the rotation matrix of the plurality of third real-time attitude quaternions.

2. The method of claim 1, wherein the method comprises: The plurality of inertial measurement units comprises: a pelvic inertial measurement unit (1) fixedly arranged at a position of a hip joint on a back parallel to a coronal plane of a human body; a thigh inertial measurement unit (2) fixedly arranged at a position of a contour of a thigh projected on the coronal plane, the position being equal in vertical distance to a hip joint and a knee joint; a lower leg inertial measurement unit (3) fixedly arranged at a position of a contour of a lower leg projected on the coronal plane, the position being equal in vertical distance to a knee joint and an ankle joint; a foot inertial measurement unit (4) fixedly arranged at a center of a instep parallel to a sagittal plane.

3. The method of claim 1, wherein Each of the inertial measurement units comprises an inertial sensor, a microcontroller and a Bluetooth module, the inertial sensor and the Bluetooth module being electrically connected to the microcontroller, and the inertial sensor comprising a three-axis accelerometer, a gyroscope and a magnetometer.

4. The method of claim 1, wherein The plurality of first initial attitude quaternions of the plurality of inertial measurement units relative to the terrestrial coordinate system includes a first initial attitude quaternion of the pelvic inertial measurement unit relative to the terrestrial coordinate system The first initial attitude quaternion of the thigh inertial measurement unit relative to the terrestrial coordinate system The first initial attitude quaternion of the lower leg inertial measurement unit relative to the terrestrial coordinate system The first initial attitude quaternion of the foot inertial measurement unit relative to the terrestrial coordinate system The plurality of first real-time attitude quaternions of the plurality of inertial measurement units relative to the terrestrial coordinate system includes a first real-time attitude quaternion of the pelvic inertial measurement unit relative to the terrestrial coordinate system The first real-time attitude quaternion of the pelvic inertial measurement unit relative to the terrestrial coordinate system The first real-time attitude quaternion of the pelvic inertial measurement unit relative to the terrestrial coordinate system The first real-time attitude quaternion of the pelvic inertial measurement unit relative to the terrestrial coordinate system 5. The method of claim 4, wherein the method further comprises: The attitude angle θ is calculated by the following formula: obtaining a first initial attitude quaternion of the pelvic inertial measurement unit with respect to a terrestrial coordinate system Substituting into the quaternion-to-rotation matrix formula gives the first rotation matrix Substituting into the quaternion-to-rotation matrix formula gives the first rotation matrix According to The x-axis direction representation in the first inertial measurement module coordinate system is calculated as Definitions The angle between the unit gravity vector z g and the body-fixed vector x is the attitude angle θ. The vector defined as being perpendicular to the vector x IMU1_2_G and the unit gravity vector z g is the attitude vector n1; The attitude vector n1 is calculated by the following formula: The second initial attitude quaternions of the plurality of body segments relative to the geodetic coordinate system are calculated by the following formula: The third initial attitude quaternions of the plurality of inertial measurement units relative to the plurality of body segments are calculated by the following formula: n1 = [2(xy + wz), y - x, 0] 2 2 2 2 T ​​​​ wherein w, x, y and z are respectively the constituent elements of the composition.

6. The method of claim 5, wherein the method further comprises: The third real-time attitude quaternions of the plurality of body segments relative to the geodetic coordinate system are obtained by the following formula: wherein is a second initial attitude quaternion of the pelvis inertial measurement unit with respect to the terrestrial coordinate system, is a second initial attitude quaternion of the thigh inertial measurement unit with respect to the terrestrial coordinate system, is a second initial attitude quaternion of the shank inertial measurement unit with respect to the terrestrial coordinate system, is a second initial attitude quaternion of the foot inertial measurement unit with respect to the terrestrial coordinate system, q(0, n1) is a quaternion that rotates by an angle 0 about the vector n1, 7. The method of claim 6, wherein the method further comprises: determining a position of the lower extremity of the human body in the image; and determining a position of the upper extremity of the human body in the image. The floating axes of the plurality of joints are calculated by the following formula: wherein is a plurality of third initial attitude quaternions of the plurality of inertial measurement units with respect to the plurality of body segments, is a plurality of second initial attitude quaternions of the plurality of body segments with respect to the geodetic coordinate system, is a plurality of first initial attitude quaternions of the plurality of inertial measurement units with respect to the geodetic coordinate system.

8. The method of claim 7, wherein the method further comprises: The movement angles of the plurality of joints in the sagittal plane, the coronal plane and the horizontal plane are calculated by the following formula: wherein is a plurality of second real-time attitude quaternions of the plurality of inertial measurement units with respect to the plurality of body segments, is a plurality of third real-time attitude quaternions of the plurality of body segments with respect to the geodetic coordinate system, is a plurality of first real-time attitude quaternions of the plurality of inertial measurement units with respect to the geodetic coordinate system.

9. The method of claim 8, wherein the method further comprises: ​ where e Hip is the floating axis of the hip joint, e Knee is the floating axis of the knee joint, e Ankle is the floating axis of the ankle joint, |·| denotes unitization, i, j and k represent unit vectors in the x, y and z directions, respectively, is the third real-time attitude quaternion of the pelvis with respect to the earth coordinate system, is the third real-time attitude quaternion of the thigh with respect to the earth coordinate system, is the third real-time attitude quaternion of the shank with respect to the earth coordinate system, is the third real-time attitude quaternion of the foot with respect to the earth coordinate system, R(*) represents the rotation matrix of a certain quaternion.

10. The method of claim 9, wherein the method is a method of analyzing a human lower limb motion posture. ​ In the formula, a1 represents the movement angle of the hip joint in the sagittal plane, b1 represents the movement angle of the knee joint in the sagittal plane, g1 represents the movement angle of the ankle joint in the sagittal plane, a2 represents the movement angle of the hip joint in the coronal plane, b2 represents the movement angle of the knee joint in the coronal plane, g2 represents the movement angle of the ankle joint in the coronal plane, a3 represents the movement angle of the hip joint in the horizontal plane, b3 represents the movement angle of the knee joint in the horizontal plane, and g3 represents the movement angle of the ankle joint in the horizontal plane.

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