JP7146190B2 - State estimation system and state estimation method - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act Presented at the 48th Graduation Research Presentation Lecture Meeting for Student Members of the Chugoku-Shikoku Student Association of the Japan Society of Mechanical Engineers on March 6, 2018. Lectured at the Dynamics and Design Conference 2018 on August 29, 2018. Presented in a collection of papers

The present invention relates to a state estimation system capable of estimating the motion, posture, moment around each joint, etc. of each part of a human being, and more specifically, to a state estimation system that is capable of estimating the motion, posture, and moment of each part of a human being. This relates to a state estimation system that can estimate the motion and posture of the body, and the moment of the ankle and hip joints.

Conventionally, as a system capable of estimating the angle and position of each part of a standing human being, there is a system such as that described in Patent Document 1 below.

The system described in Patent Document 1 comprises a first acceleration sensor attached to at least one of the left and right thighs of a human, and a second acceleration sensor attached to the upper body of the human. Using the acceleration measured by the first acceleration sensor and the second acceleration sensor, it is possible to estimate the bending state of joints such as the hips and knees of the lower body of a human being.

As another conventional example, when estimating the posture of a human, each part of the human is marked, and the marking is obtained by motion capture. Some systems are designed to detect

Using such a system makes it possible to estimate the angles and movements of a person's legs, legs, and upper body. You will be able to judge objectively.

JP 2018-015023 A

However, when estimating the position, motion, and other states of each part of a human using the system described above, there are the following problems.

In other words, in the system described above, it is necessary to attach marks for accelerometers and motion capture to multiple parts of the human body. There was a problem that it took a lot of time and effort. In addition, when an acceleration sensor or motion capture is used, only the position and acceleration of the body surface can be detected, and when estimating the displacement of the center of mass, there is a problem that an error inevitably occurs.

In view of the above problems, the present invention aims to provide a state estimation system capable of easily and quickly estimating the state of each part of a subject, such as position, motion, and moment.

That is, in order to solve the above problems, the present invention provides a force plate having a plurality of load cells, and based on the output values from the load cells, the shear force from the subject along the plane of the force plate and the subject At least the angle, angular velocity, angular acceleration, and moment of each part of the subject using the first calculation unit that calculates the center of pressure in the standing state, and the shear force and the center of pressure calculated by the first calculation unit and an output unit for outputting the value calculated by the second calculation unit. The height up to the joint, the height up to the center of mass of the foot, and the height of the center of mass of the body are used as parameters for calculation .

Then, when performing the calculation in the second calculation unit, the moment of the ankle joint in the sagittal plane of the human being is calculated.

After calculating the moment of the ankle joint in this way, the acceleration, displacement, and velocity of the two centers of mass of the lower body and the upper body in the sagittal plane are calculated.

Similarly, after calculating the acceleration, displacement, and velocity of the two centers of mass of the lower body and the upper body in the sagittal plane, the moment of the hip joint is estimated.

In another aspect of the invention, the moment of the ankle joint on the frontal plane is calculated by the second calculation unit.

At this time, after calculating the moment of the ankle joint on the frontal plane, the acceleration, displacement, and velocity of the two centers of mass of the lower body and the upper body on the frontal plane are calculated.

Then, after calculating the acceleration, displacement, and velocity of the two centers of mass of the lower body and the upper body on the frontal plane, the moment of the hip joint is estimated.

Also, by independently providing the force plates corresponding to the left and right feet, the moment of the lower half of the body can be determined separately.

In this way, according to the present invention, it is possible to detect the angle, angular acceleration, moment, etc. of each part of the subject using only the shear force and pressure center of the force spray. It becomes possible to easily estimate the state of the subject without applying marks for the purpose.

The figure which shows the state which stood up to the force plate in one embodiment of this invention. Functional block diagram in the same form A diagram showing a one-link model in the sagittal plane in the sagittal plane of the same morphology A diagram showing a two-link model in the sagittal plane of the same morphology Diagram for detecting the state in the frontal plane of the same morphology Flowchart showing isomorphic estimation method Comparative example of one link model in the sagittal plane of the conventional example and the present invention Comparative example of the two-link model in the sagittal plane of the conventional example and the present invention Comparative example of hip joint moment in the sagittal plane of the conventional example and the present invention Comparative example of one-link model in the sagittal plane when the conventional example and the force plate of the present invention are oscillated Comparison example of two-link model in the sagittal plane when the conventional example and the force plate of the present invention are oscillated Comparative example of hip joint moment in the sagittal plane when the conventional example and the force plate of the present invention are oscillated Comparative example of 1-link model in the frontal plane of the conventional example and the present invention Comparative example of the two-link model in the frontal plane of the conventional example and the present invention Comparative example of the moment in the frontal plane of the conventional example and the present invention

An embodiment of the present invention will be described below with reference to the drawings.

The state estimation system 1 in this embodiment is capable of estimating the state (hereinafter abbreviated as "state") of each part of a human standing on a force plate 2, such as the position, velocity, acceleration, and moment. As shown in FIGS. 1 and 2, a force plate 2 having a plurality of load cells 4; Using the first calculation unit 5 that calculates the center of pressure on the plate 2, and the shear force and the center of pressure calculated by this first calculation unit 5, the angle, acceleration, angular acceleration, moment, etc. of each part of the subject are calculated. A second calculation unit 6 for calculating the state is provided. The state estimation system 1 according to this embodiment will be described in detail below. In this embodiment, for convenience of explanation, as shown in FIG. 1, the front-rear direction of the force plate 2 is defined as the X-axis direction, the left-right direction as the Y-axis direction, and the vertical direction as the Z-axis direction. to stand up in the X-axis direction. Also, the sagittal plane indicates the XZ plane, and the frontal plane indicates the XY plane.

First, the force plate 2 is configured with load cells 4 below four corners of a rectangular plate 3 . This load cell 4 is configured by attaching a strain gauge (not shown) to a strain-generating body, and detects the deformation of the strain-generating body using the strain gauge, and detects the load acting in the XYZ directions and the It is designed to detect moments around the XYZ axes. Using these load cells 4, it is now possible to calculate the shear force along the XY plane from the subject acting on the plate 3, the center of pressure for the load acting on the XY plane from the Z-axis direction, and the like. there is In addition, in this embodiment, it is possible to detect changes in the state of each part by rocking the human being, and an acceleration sensor that detects the movement of the force plate 2 and a sensor that detects the movement state of the force plate. A swing detection means 8 such as a rotary encoder is provided for the purpose. In this case, the swing detection means 8 is composed of an acceleration sensor and a rotary encoder. 8 may be used.

The center of gravity of the subject standing on the force plate 8 moves in the front-rear direction at the moment of movement, and a shearing force acts on the force plate 2 from the feet along with this movement. The first calculation unit 5 calculates this shearing force and also calculates the center of pressure based on the load of the subject in the Z-axis direction. At this time, when calculating the shear force, the sum of the loads in the X-axis direction of the load cells 4 provided at the four corners is calculated, and the difference between the load sum values before and after the sampling time is calculated as the shear force. On the other hand, when calculating the center of pressure, the load in the Z-axis direction of the load cells 4 provided at the four corners is detected, and the coordinates of the center of pressure are calculated using the moment balance formula, using the coordinates of the center of pressure as unknowns. go. Then, the shear force and the center of pressure calculated in this way are output to the second calculation unit 6 .

Using this shearing force and the center of pressure, the second calculation unit 6 first calculates the angle and angular acceleration of the ankle joint of the subject in the sagittal plane, and the moment acting on the ankle joint. When calculating these values, the mass of the subject's foot, the mass of the body, the moment of inertia around the center of mass of the body, the height of the ankle joint from the ground, and the height of the center of mass of the foot , the length from the ankle joint to the center of mass of the body is input as a parameter. These parameters may be measured directly from the subject, or may be estimated using past statistical values from the subject's height and weight.

Using these parameters, the shear force, and the center of pressure, when calculating the joint angle and angular acceleration of the foot and leg in the sagittal plane, and the moment acting on the ankle joint, using the one-link model in Fig. 3, Calculate as follows.

<State in the sagittal plane>

First, the X-direction, Z-direction, and moment around the ankle joint in the foot are calculated by the following Equation 1, respectively. As parameters, m _f is the mass of the foot, m _b is the mass of the body, J _b is the moment of inertia around the center of mass of the body, L _f is the height of the ankle joint, and _lf is the height of the center of mass of the foot. , l ₁ is the length from the ankle joint to the center of mass of the lower body, and M is the weight of the subject.

On the other hand, the X-direction, Z-direction, and moment around the ankle joint in the body part are calculated by the following Equation 2, respectively.

Then, the following Equation 3 is obtained from the sum of Equations 1 and 2 above (balance equation in the X-axis direction).

Further, the following Equation 4 is obtained from the sum of the third equation (moment balance equation) of Equations 1 and 2 above.

The right sides of these Equations 3 and 4 are all parameters and measured values, and the left sides are simultaneous linear equations of the angle and angular acceleration of the ankle joint to be calculated. By solving this, the angular acceleration and angle of the ankle joint can be obtained as shown in Equations 5 and 6.

Also, the moment acting on the ankle joint can be obtained from only the force acting on the floor reaction force (the force in the Z-axis direction) from the third formula (moment balance formula) of Formula 1, as shown in Formula 7.

Next, from the ankle joint angles, angular accelerations, and moments thus calculated, the states of the subject's lower body and upper body are calculated using the two-link model shown in FIG.

When calculating the angle and angular acceleration of each of the lower body and upper body of a human, or the moment around the hip joint, which is the joint between the lower body and upper body, the calculation is performed as follows. Here, as parameters, m _f is the foot mass, m ₁ and m ₂ are the masses of the lower body and upper body, respectively, J ₁ and J ₂ are the moments of inertia around the centers of mass of the lower body and upper body, and L _f is the leg mass. Joint height, l _f is the height of the foot center of mass, l ₁ is the length from the ankle joint to the lower body center of mass, L ₁ is the length from the ankle joint to the hip joint, l ₂ is the hip joint to the upper body center of mass be the length of These parameters are assumed to be similarly estimated from past statistical values using the subject's height, weight, and the like.

Using the parameters, shear force, center of pressure, and ankle joint angles, angular accelerations, and moments around the ankle joints calculated using Equations 5 to 7, the lower body as shown in Fig. 4, which is a two-link model. The X-axis direction balance equation, the Z-axis direction balance equation, and the moment around the ankle joint are established as shown in the following equation (8).

On the other hand, the balance equation in the X-axis direction, the balance equation in the Z-axis direction, and the moment around the ankle joint in the upper body are established as shown in Equation 9 below.

Then, the equation of motion in the X-axis direction is obtained as shown in Equation 10 from the sum of the first equation (balance equation in the X-axis direction) of Equations 1, 8, and 9.

On the other hand, the equation of motion in the Z-axis direction is obtained as shown in Equation 11 from the sum of the second equations (balance equations in the Z-axis direction) of Equations 1, 8, and 9.

Here, M indicates the body weight of the subject. Substituting Equation 11 into the third equation (moment balance equation) of Equations 1, 8, and 9, an equation of motion regarding rotation is obtained as shown in Equation 12.

Here, the center of mass of the link model in FIGS. 3 and 4 is represented by the following equation (13).

Substituting this relationship into the third and fourth terms on the left side of Equation 12 yields Equation 14 below.

Assuming that the first term on the right side of Equation 14 is estimated by Equation 6, the right sides of Equations 10 and 14 are all known, and these represent the binary simultaneous 1 The following equation is obtained. By solving this, the angular accelerations of the lower body and the upper body are obtained, and the angles of the lower body and the upper body are calculated by integrating the angular accelerations thus obtained.

When the angular acceleration and angle of the two-link model in FIG. 4 can be calculated in this way, the moment around the hip joint is calculated from the sum of the third formula of formulas 1 and 8, and the first formula of formulas 1 and 8. By substituting R _hx , the following equation 15 is obtained.

If the angular accelerations and angles of the upper and lower bodies can be estimated in this way, the moment N _h around the hip joints can be automatically obtained from equation (15).

Then, the angular acceleration, angular velocity, moment, and the like of the ankle joints, the lower body, and the upper body calculated in this way are output so that the state of the subject can be determined. When calculating such a value, if the force plate is accelerating, the acceleration in the direction detected by the swing detection means 8 is taken into account in the calculation.

<State in the frontal plane>

Next, FIG. 5 shows a model in the frontal plane (XY plane). In this model, the body is composed of six segments, both feet, both legs, pelvis, and upper body, and has five joints in both ankle joints, both hip joints, and waist. Here, (X _f,r ,Z _f,r ), (X _f,l ,Z _f,l ) are the centers of mass of the left and right feet, (X _l,r ,Z _l,r ), (X _{l, l} , Z _{l, l} ) are the coordinates of the center of mass of the left and right legs, (X _p , Z _p ) of the center of mass of the pelvis, and (X _u , Z _u ) of the center of mass of the upper body. As body parameters, m _f is the mass of the foot, m _l is the mass of the leg, m _w is the mass of the pelvis, m _u is the mass of the upper body, J _l is the moment of inertia around the center of mass of the leg, and _Ju is Let it be the moment of inertia around the center of mass of the upper body. In addition, L _f is the height of the ankle joint, l _f is the height of the center of mass of the foot, l _l is the length from the ankle joint to the center of mass of the leg, L _l is the length from the ankle joint to the hip joint, l _{Let p} be the length from the hip joint to the pelvic center of mass, L _p be the length from the hip joint to the waist joint, and l _u be the length from the waist joint to the upper body center of mass. Let θ _l,r and θ _l,l be the posture angles of both legs viewed from the vertical axis, and θ _u be the angle of the upper body.

The stance width of both feet is assumed to match the hip width w, and the legs are assumed to always be parallel and at equal angles. As a result, θ _l =θ _l,r =θ _l,l . In addition, it is assumed that there is no up-and-down movement due to the knee joint and the change in posture angle is minimal. As a result, it can be considered as a linear system, and it is considered that each articulated joint is acted upon by a restraining force and a moment as shown in FIG.

Under such a premise, the following relational expression (16) holds for the left and right legs, the left and right legs, the pelvis, and the upper body.

Next, the equation of motion for each segment is obtained based on the free body diagram. However, in the following equations, the horizontal acceleration of the segment is converted into the supporting surface acceleration and the angular acceleration of each segment according to Equation (16). Also, since it is assumed that the left and right leg posture angles are always equal, the angles and angular accelerations are also assumed to be the same in the calculations.

Accordingly, the equations for the horizontal direction, the vertical direction, and the moment of the right foot are given by the following equations 17, respectively.

Similarly, the horizontal, vertical and moment equations for the left foot are shown in Equation 18 below.

Similarly, the horizontal, vertical and moment equations for the right leg are shown in Equation 19 below.

Similarly, the horizontal, vertical, and moment equations for the left leg are shown in Equation 20 below.

Similarly, the equations for the horizontal, vertical and moment of the pelvis are shown in Equation 21 below.

Similarly, the horizontal, vertical, and moment equations for the upper body are shown in Equation 22 below.

Based on the above formula, the relational expression between the floor reaction force and the posture will be shown in order. First, from the first equation (horizontal relational expression) of Equations 17 to 22, the motion equation of translational motion about the Y-axis is as follows.

Here, M indicates body weight and R _y =R _y,r =R _y,l . Next, from the second equation (vertical relational expression) of Equations 17 to 22, the balance of force with respect to the Z axis is as follows.

Next, the equation of motion for rotation is shown. R _hy,r , R _hy,l , R _hz,r , and R _hz,l are required for arranging the formulas _. get

Similarly, R _hy,l is obtained from the second expressions of Equations 18 and 20.

R _hz,r is obtained from the second equation of Equations 17 and 19.

R _hz,l is obtained from the second equation of Equations 18 and 20.

Also, since R _wy is also required, the following equation is obtained from the first equation of Equations 17 to 21.

As the summation of the formulas related to rotation, calculate the sum of the third formulas of formulas 17 to 22, and replace the parts R _hy,r , R _hy,l , R _hz,r , and R _hz,l with formulas 25 to 28. Substituting, we get:

where m _b =M-2m _f is the mass of the body part. The following equation holds from the relationship between the centers of mass of the 1-link model and the 2-link model.

Substituting this into Equation 30 yields the following equation.

Accordingly, when the posture angle θ _b of the one-link model in FIG. 3 is known, the angular velocities of the upper body and lower body can be obtained by solving the simultaneous linear equations of Equations 23 and 32. In addition, the moment that the body receives from the floor is N _s , and if there is only one plate, it is the inverse of the measured moment M _x around the X axis, and N _s =-M _x . .

On the other hand, when there are two force plates, it is represented by the following equation.

Here, w is the stance width, and R _z,r and R _z,l are the relative displacements of the center of pressure from the virtual center of the left and right feet. Y _p1 and Y _p2 are the pressure centers of the respective force plates, R _z1 and R _z2 are the vertical reaction forces, and h is the distance between the origins of the two force plates. The suffix 1 indicates the output value of the force plate on the right foot, and the suffix 2 indicates the output value of the force plate on the left foot.

Equations 23 and 30 are the basic equations of this two-link model. The following equation is obtained by giving a constraint condition to make this a one-link model.

As described above, the frontal plane can be developed with the same theory as the sagittal plane. That is, Equations 3 and 4, which are the equations of motion of the one-link model in the sagittal plane, correspond to Equations 34 and 35, which are the equations of motion of the one-link model in the frontal plane. Equations 10 and 12, which are equations of motion of , correspond to Equations 23 and 30, which are equations of motion of the two-link model of the frontal plane.

<Estimation of Joint Moment on Frontal Plane>

Next, using the posture estimation result based on the force plate 2, the joint moment on the frontal plane is estimated. When there is only one force plate 2, it is possible to estimate the "moment of the lower body (the sum of the moments of both hip joints and both ankle joints)" and the "moment around the waist". On the other hand, when measuring with two force plates for each foot, the five moments of "left ankle joint moment", "right ankle joint moment", "left hip joint moment", "right hip joint moment", and "moment around waist" can be estimated.

First, the left and right ankle joint moments are obtained as follows from the sum of the third equations of Equations 17 and 18, respectively.

Also, the right hip joint moment is obtained by calculating the sum of the third expressions of Equations 17 and 19 and substituting Equations 25 and 29 for Rhy,r and Rhz,r.

The left hip joint moment can be calculated by the sum of the third expressions of Equations 18 and 20.

If there are two force plates 2 in this manner, the left and right joint moments can be estimated independently.

Next, the sum of the left and right ankle joint torques is obtained from the sum of Equations 36 and 37 as follows.

Also, the sum of the left and right hip joint torques is obtained from the sum of Equations 38 and 39 as follows.

Equations 40 and 41 require the difference Rz,r-Rz,l between the vertical reaction forces of the left and right force plates 2, and therefore cannot be calculated separately for the hip joint and the ankle joint. On the other hand, the moment τl of the entire lower body is, from the difference between Equation 40 and Equation 41,

となるので、こちらは１枚のフォースプレート２の計測から推定することができる。

Therefore, this can be estimated from the measurement of one force plate 2 .

Finally, find the moment around the waist. In this calculation, the following equation is obtained by summing the first equations of equations 17 to 21.

After calculating the third formula of formulas 17 to 21, and substituting formula 43, the following formula is obtained.

This can also be calculated from the measured values of one force plate 2 .

Next, a method of estimating the angle, angular acceleration, moment, etc. of each part of a human being using the state estimation system 1 configured as described above will be described with reference to the flow chart of FIG.

First, the height, weight, etc. of a human subject are measured in advance, and each parameter necessary for calculation is calculated. In that state, the force plate 2 is made to stand up, and the shear force along the plane of the plate 3 and the center of pressure applied to the plate 3 are calculated using the load cells 4 provided at the four corners of the plate 3. 5 (step S1).

Then, using such known parameters and shear force, the angular acceleration and angle of the ankle joint in the sagittal plane, the angle, and the moment acting on the ankle joint are expressed by Equations 5, 6, and 7. (Step S2).

Next, with the angular acceleration, angle, and moment of the ankle joints calculated in this way, next, using the two-link model, the angular acceleration, angle, and moment of the hip joint, etc. of the lower body and upper body are calculated by Equations 10 and 14. , from Equation 15 (step S3).

Next, using the angle _.theta.b of the one-link model thus calculated, the angular acceleration in the frontal plane is obtained using equations 23 and 32, and the angle is obtained by integrating this. In addition, since the moment that the body receives from the floor surface is the moment around the X-axis at the center of pressure, N _s =-M _x , and if there are two force plates 2, the moment can be obtained from Equation 33 (step S4).

Finally, the joint moment on the frontal plane is calculated using Equations 39, 39, 42, and 44 (step S5). In this way, calculations are performed in order from the 1-link model on the sagittal plane to the 2-link model and then the model on the frontal plane, and the angular acceleration, angle, and moment of each part are calculated and output (step S6).

Thus, according to the above embodiment, the force plate 2 having a plurality of load cells 3 and the shear force from the subject along the plane of the force plate 2 based on the output values from the load cells 3 and Using the first calculation unit 5 for calculating the center of pressure in the standing state of the subject, and the shear force and the center of pressure calculated by the first calculation unit 5, the angle, angular velocity, and angular acceleration of each part of the subject are calculated. , and an output unit 7 for outputting the value calculated by the second calculation unit 6. The second calculation unit 6 calculates in advance the foot mass, Since the body part mass, the height from the force plate to each joint, the height to the center of mass of the foot part, and the height of the center of mass of the body part are used as parameters, the shear force of force plate 2 and The state of each part of the human body can be detected only from the center of pressure, and the state of the subject can be easily estimated without applying motion capture marks as in the past.

An example of comparison between the result of the state method using only the force plate described above and the result of detection using the conventional motion capture and force plate will be shown. In the demonstration experiment, measurement was performed for 30 seconds, and the values measured by motion capture are indicated by a thick line, and the values estimated in the above embodiment are indicated by a thin line. The sampling frequency was set to 100 Hz for both, and the angular velocity and angular acceleration measured by motion capture were calculated by numerical differentiation. As a test subject, a man with a height of 180 cm and a weight of 73 kg was asked to stand on a stationary floor.

The angle, angular velocity, and angular acceleration of the one-link model in the sagittal plane are shown in order from the top of FIG. As can be seen from FIG. 7, the values are similar to those calculated by motion capture.

FIG. 8 shows the angles, angular velocities, and angular accelerations of the two-link model. Similarly, in FIG. 8, it can be seen that the values are similar to those calculated by motion capture.

Further, the moment around the hip joint is shown in FIG. Also in FIG. 9, it can be seen that the values are similar to the values calculated by motion capture.

Next, we will show the results of a rocking experiment in which the force plate is equipped with a vibrating device. The force plate was oscillated irregularly by superimposing a plurality of oscillating waveforms between 0.1 Hz and 1.0 Hz.

As shown in Fig. 10, it can be seen that the 1-link model is similar to the conventional motion capture method, and the 2-link model (Fig. 11) and hip joint moment (Fig. 12) are also very similar. I found out that I do.

On the other hand, a demonstration experiment was conducted on the frontal plane. In this case as well, a comparative example with motion capture is shown. FIG. 13 shows the values of the one-link model, FIG. 14 shows the values of the two-link model, and FIG. 15 shows the joint moment values. As can be seen from these values, the estimation method using only the force plate was found to be very similar to the estimation by motion capture.

1 State estimation system 2 Force plate 3 Plate 4 Load cell 5 First calculation unit 6 Second calculation unit 7 Output unit 8 Shaking motion detection means

Claims (9)

a force plate with multiple load cells;
a first calculation unit that calculates the shear force from the subject along the plane of the force plate and the center of pressure of the subject in the standing state based on the output value from the load cell;
a second calculation unit that calculates at least one of the angle, angular velocity, angular acceleration, and moment of each part of the subject using the shear force and the center of pressure calculated by the first calculation unit;
an output unit that outputs the value calculated by the second calculation unit;
In a state estimation system comprising
The second calculation unit calculates in advance the mass of the foot, the mass of the body, the height from the force plate to each joint, the height to the center of mass of the foot, and the height of the center of mass of the body as parameters. A state estimation system that is 2. The state estimation system according to claim 1 , wherein the second calculation unit calculates the moment of the ankle joint in the human sagittal plane. 2. The method according to claim 1 , wherein the second calculation unit calculates the moment of the ankle joint on the sagittal plane, and then calculates the acceleration, displacement, and velocity of the two centers of mass of the lower body and the upper body on the sagittal plane. state estimation system. The state estimation system according to claim 1 , wherein the second calculation unit calculates the moment of the hip joint after calculating the acceleration, displacement, and velocity of the two centers of mass of the lower body and the upper body in the sagittal plane. . 2. The state estimation system according to claim 1 , wherein the second calculation unit calculates the moment of the ankle joint on the frontal plane. The state according to claim 1 , wherein the second calculation unit calculates the acceleration, displacement, and velocity of the two centers of mass of the lower body and the upper body on the frontal plane after calculating the moment of the ankle joint on the frontal plane. estimation system. 2. The state estimation according to claim 1 , wherein the second calculation unit estimates the moment of the hip joint after calculating the acceleration, displacement, and velocity of the two centers of mass of the lower body and the upper body on the frontal plane. system. 2. The state estimation system according to claim 1 , wherein the force plates are provided independently on both legs. In a state estimation method for estimating the state of a subject standing on a force plate using a force plate equipped with a plurality of load cells,
a first calculation step of calculating the shear force from the subject along the plane of the force plate and the center of pressure of the subject using the load cell values;
a second calculation step of calculating at least one of the angle, angular velocity, angular acceleration, and moment of each part of the subject using the shear force and the center of pressure calculated in the first calculation step;
a step of outputting the value calculated in the second calculation step ;
In a state estimation method comprising
In the second calculation step, the mass of the foot, the mass of the body, the height from the force plate to each joint, the height to the center of mass of the foot, and the height of the center of mass of the body are calculated in advance as parameters. state estimation method.

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