JP7106065B2 - force plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a force plate that can detect force and the center of gravity generated when a person walks or runs. It relates to force plates that are made detectable.

A force plate that detects force generated when a person walks or runs is composed of a pair of upper and lower metal plates and a triaxial load cell provided between these plates (see Patent Document 1). . When detecting force using such a force plate, the force acting in the vertical direction (Z-axis direction) of the load cells provided at the four corners and the direction along the plane of the plate (X-axis direction and Y-axis direction) direction) and the center of gravity (COP) of that force.

By the way, when detecting force with such a conventional force plate, a relatively thick metal plate is used in order to prevent the upper plate from deforming (or to limit the deformation to a small range). In addition, the load cells are provided at the very four corners of the plate so as not to apply force to the outer regions of the load cells at the four corners and to prevent the load cells from generating moments.

JP 2010-110382 A (56th paragraph)

However, when such a force plate is used to detect force, if the plate is relatively thin, the plate will inevitably flex and the force will be dispersed. In addition, when such bending occurs, as shown in FIG. 4, even though the force is applied in the X-axis direction, a force component in the Z-axis direction is generated due to the tilt angle θ due to the bending. error occurs. In addition to the bending of the plate, if a shearing stress is generated in the strain gauge of the load cell, an error associated with the deformation will occur. Furthermore, if you try to install a load cell near the center of the plate to reduce the error due to deflection, your foot will rest on the outer area of the load cell, and an upward force will be applied to the load cell on the far side with the nearest load cell as a fulcrum. It will not be possible to detect the exact value.

Accordingly, the present invention has been made in view of the above problems, and is a force sensor that can accurately detect a force even when the plate is bent or a force acts on the plate in the outer region of the load cell. Intended to serve plates.

That is, in order to solve the above problems, the force plate of the present invention is provided between a pair of plates provided on the top and bottom, and between the pair of plates . A plurality of load cells that detect the moment of two orthogonal axes along the plane of the load cell, and the force in the three orthogonal axes based on the moment of the two axes generated by the deflection of the plate provided on the upper side of the load cell and a correction unit for correcting the

Moreover, in such an invention, an acceleration sensor may be provided in the load cell, and the forces in the three axial directions may be corrected by the correction unit based on the values obtained by the acceleration sensor.

According to the present invention, even if the plate is made thinner or the area of the plate is increased and deflection occurs, correction based on the deflection can be performed, and accurate force can be detected. become.

Schematic diagram of a force plate that is one embodiment of the present invention Schematic plan view of the force plate in the same configuration A view of placing an additional plate on top of the upper plate in the same configuration A diagram showing a state in which the force plate in the same configuration is bent. A diagram showing a state in which the force plate in the same configuration is tilted as a whole. Flowchart for detecting force plate force in isomorphism

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

The force plate 1 in this embodiment, as shown in FIGS. Configured. Characteristically, a correction unit 5 for calculating a correction value based on the deflection of the upper plate 11 provided on the upper side of the load cell 2 is provided so that the force in the orthogonal XYZ axis direction can be corrected by the value of this correction unit 5. It is the one that was made. The configuration of the force plate 1 according to this embodiment will be described in detail below. In this embodiment, the directions along the plane of the lower plate 12 installed on the horizontal plane are defined as the X-axis and the Y-axis, and the normal direction of the plane is defined as the Z-axis.

First, the force plate 1 is composed of a pair of rectangular upper and lower plates 11 and 12 (see FIG. 2). A plate having such a rigidity and thickness that it does not come into contact with the lower plate (hereinafter referred to as the lower plate 12) even if it is performed is used. On the other hand, the lower plate 12 is made of a relatively rigid material (stainless steel, etc.) that does not bend even if it is installed in an unstable place with unevenness. In this embodiment, a rectangular plate will be described as an example of the plate, but plates of various shapes such as square, triangular, and circular plates can be used according to the application. can be used.

The load cells 2 provided at the four corners of the force plate 1 are 5-axis load cells capable of detecting loads in the XYZ directions and moments in the XY directions along the planes of the plates 11 and 12. 2 is used. Various types of load cells can be used as the load cell 2. For example, a load cell that can detect a load by using a resistance change of a strain gauge attached to a strain generating body (not shown) is used. Such a load cell 2 is provided between the upper plate 11 and the lower plate 12 as shown in FIG. 1, and the body flange 21 is attached to the upper plate 11 and the lower plate 12 with bolts. A strain-generating body is attached across the upper plate 11 and the lower plate 12, and the strain gauge attached to the strain-generating body is deformed as the upper plate 11 is deformed. As for the mounting positions of such load cells 2, not only near the four corners of the plate, but also inside the four corners as shown in FIG. A load cell 2 may be provided on the center side of the additional plate 13 so that the vicinity of the boundary can be stepped on. If the load cell 2 is provided on the central side in this way, the load cell 2 approaches the central portion of the plates 11, 12, and 13, so even if a large force acts on the central portion of the upper plate 11 or the like, a large deflection will occur. can be prevented.

Further, in this embodiment, the load cell 2 is attached with an acceleration sensor 3 (see FIG. 1). When such an acceleration sensor 3 is used, the tilt angle of the force plate 1 as shown in FIG. 5 can be calculated from the detected acceleration. The detected value can be corrected in consideration of the inclination angle of the plate caused by the accident.

Using the load cell 2 attached in this manner, the operation of the load detection unit 4 (see FIG. 1) that detects forces in the XYZ axis directions accompanying human motion will be described.

First, when a person moves on the upper plate 11, the X-axis, Y-axis, and Z-axis forces of all the load cells 2 are detected and added. These values do not need to be corrected if the upper plate 11 is not flexed, because the force applied by the human and the force detected by the load cell 2 match. However, if the upper plate 11 is bent, an error will occur in the force along the plane. Specifically, as shown in Fig. 4, when a person kicks his or her foot in the direction of the X-axis to apply a force Px in a flexed state, the force Px is applied along the flexed plate to the load cell. 2 side. At this time, in the load cell 2, since the force Px acts in the direction along the angle θ due to the deflection of the plate, the force Px sin θ acts upward as the load in the Z-axis direction, and the load in the X-axis direction Px cos θ acts as a load. In addition to the error due to the deflection of the upper plate 11, the strain gauge attached to the strain generating body undergoes shear deformation, which causes an error in the load cell 2 itself. Therefore, in this embodiment, even if the upper plate 11 is flexed or the strain gauge is sheared, the correction section 5 is provided so as to correct the error.

In this correction unit 5, it is assumed that the force of the XYZ axes and the moment in the XY axis direction detected by all the load cells 2 including its own load cell 2 are affected by bending, etc., and are detected by all the load cells 2. The corrected forces Fx, Fy, Fz, Mx, and My are multiplied by a predetermined coefficient to calculate the corrected forces.

Specifically, first, the voltage, which is the output of the strain gauge, is amplified to output forces in three axial directions (Fx0, Fy0, Fz0) and moments in two axial directions (Mx0, My0) before correction. Then, these values are multiplied by the correction matrix C to calculate the force (Fx, Fy, Fz) in three axial directions and the moment (Mx, My) in two axial directions after correction. This correction matrix C is composed of coefficients that will be affected by the forces and moments detected by all the load cells 2, including itself. , consists of 5 coefficients of forces in 3 axial directions including itself and moments in 2 axial directions (total 25 coefficients in 5 rows and 5 columns). Each of these coefficients includes the moment of inertia of the upper plate 11, etc. By multiplying the force before correction by the coefficient having these components, the force after correction is calculated using the following equation. .

Further, these correction values are corrected using the acceleration sensor 3 as necessary. As a case where the acceleration sensor 3 is used for correction, for example, it is conceivable to measure a force at a place where vibration is generated, or to measure a force at a place on a vehicle. When correction is performed using such an acceleration sensor 3, the acceleration of each load cell 2 in the XYZ axis direction is added for each axis to calculate the inclination direction of the force plate 1. FIG. Then, based on the angle difference between the tilt direction and the horizontal direction, the force is corrected in the XYZ axis directions with reference to the horizontal plane.

Next, a method of detecting a force associated with a human motion using the force plate 1 configured in this manner will be described with reference to FIG.

When using the force plate 1 to measure the force associated with human motion, first, the force plate 1 is placed on a horizontal floor surface. At this time, each load cell 2 is subjected to not only the load due to the weight of the upper plate 11, but also the load of the additional plate 13 provided thereon, and the moment associated with these weights. Now, preset these values to zero (step S1).

Then, in this state, a person is placed on the upper plate 11, and the force in the XYZ-axis directions accompanying the motion is detected, and the moment in the XY-axis directions is also detected (step S2).

Next, the five values thus detected are multiplied by the correction matrix C using Equation 1 above to obtain the corrected load and moment associated with the deflection of the upper plate 11 and the shear deformation of the strain gauge. (Step S3).

Further, when the acceleration sensor 3 is provided, the acceleration in the XYZ axis direction of the acceleration sensor 3 provided in each load cell 2 is added to calculate the tilt angle of the force plate 1 (step S4).

Then, the tilt angle of the force plate 1 in the XYZ-axis direction is corrected from the difference between the calculated tilt angle and the initial angle of the horizontal plane, and the corrected force calculated above is calculated based on this angle (step S5 ).

As described above, according to the above-described embodiment, the upper plate 11 and the lower plate 12 are provided between the pair of plates 11 and 12, and the force in the three orthogonal axial directions and the force in the plane of the upper plate 11 are applied. a plurality of load cells 2 for detecting the moment of two orthogonal axes along the load cell 2, and the moment of the three orthogonal axes generated by the deflection of the upper plate 11 provided on the upper side of the load cell 2. Since the correction unit 5 that calculates the force correction value is provided, even if the upper plate 11 is made thinner or the areas of the upper plate 11 and the additional plate 13 are increased to make it easier to bend, Correction based on the deflection can be performed, and accurate force can be detected.

In addition , the load cell 2 is provided with the acceleration sensor 3, and the correcting unit 5 corrects the forces in the three axial directions according to the values from the acceleration sensor 3. Therefore, the force plate 1 can be installed in an unstable place. Even in the case of tilting, the direction of the force can be corrected to a value based on the horizontal plane based on the value of the acceleration sensor 3 .

It should be noted that the present invention is not limited to the above embodiments, and can be implemented in various modes.

For example, in the above embodiment, when correcting the force in the X , Y, and Z axis directions, the correction is performed using the moment in the XY axis direction. good.

Furthermore, in the above embodiment, the acceleration sensor 3 is provided inside the load cell 2, but it may be provided near the load cell 2, or may be provided in the central portion of the force plate 1, You may enable it to calculate an inclination-angle.

Reference Signs List 1 Force plate 11 Upper plate 12 Lower plate 13 Additional plate 2 Load cell 21 Flange 3 Acceleration sensor 4 Load detector 5・・・ Corrector

Claims (2)

a pair of upper and lower plates;
a plurality of load cells provided between the pair of plates and detecting forces in three orthogonal axes and moments in two orthogonal axes along the plane of the upper plate ;
a correction unit that corrects the force in the orthogonal three-axis directions based on the biaxial moment generated by the deflection of a plate provided on the upper side of the load cell;
A force plate characterized by comprising a An acceleration sensor is provided on the load cell,
2. The force plate according to claim 1, wherein the correcting unit corrects the forces in the three axial directions according to values obtained by the acceleration sensor.

Images