SU1733026A1 - Strain-gauge platform for measuring propelling effort in sports-related research - Google Patents

Abstract

The invention makes it possible to increase the accuracy of measuring the repulsive effort of an athlete from the platform. The tensoplatform consists of a rigid plate 1, six degrees of freedom of which are limited to support-dynamometers 2-7. Each support is a cantilever beam of equal resistance. The supports are rigidly fixed to the platform 8. The reaction of the supports is determined by means of strain gauges glued to the beams. The impact of the plate 1 on the dynamometers 2, 3.4 is carried out through metal balls. The action of plate 1 on dynamometers 5, 6, 7 is carried out through rolling bearings. The points of contact of the plate with dynamometers 2, 3, 4 in the plan form the vertices of an imaginary geometric triangle bounding the working supporting platform of the plate 1. The location of the supports 2-7 allows to determine the coordinates of the point of application of force and the magnitude of this force 9 ill. (L С 1 vj with so about th

Description

figure 1

The proposed tensoplatform relates to devices for measuring stresses by the method of electrical tensometry and can find the main use in measuring the repulsive effort of the legs of an athlete during long jumps, height, and running. The results of the study of these efforts can be used by the trainer to improve the training methodology.

The known construction of tensoplatforms, which, however, have the disadvantage that during the transfer of forces from the plate by a dynamometer due to elastic deformations at the points of contact, tangential friction forces arise, which additionally load the dynamometers and increase the measurement error. In addition, the influence of various components of the measured force on the strain gauges designed to measure other components is not excluded, which also reduces the accuracy of the measurements.

The purpose of the invention is to improve the measurement accuracy.

FIG. 1 shows a strain platform, top view; in fig. 2 shows section A-A in FIG. one; in fig. 3 - diagram of the measured loads and reactions of the supports; in fig. 4 (- support of horizontal component loads in axonometric view; in Fig. 5 - the same, top view; in Fig. 6 - the same, side view; in Fig. 7 - the same, end view; Fig. 8 - the support perceiving the vertical components of the loads, side view; in Fig. 9, the same, top view.

The proposed tensoplatform (Fig. 1, 2) consists of a rigid plate 1, six degrees of freedom of which are limited to six support-dynamometers 2-7. Each support is a cantilever beam of equal resistance and limits one degree of freedom of the slab. Support dynamometers 2-7 are rigidly attached to platform 8, welded from a 65x65x6 angle.

The reactions of the bonds (supports) are determined by means of strain gauges pasted on the supporting beam dynamometers.

The impact of the plate on the dynamometers is carried out either through spherical bodies - metal balls 9 (on supports 2, 3, 4, perceiving the vertical components of the load), or through rolling bearings (on supports 5, 6, 7). The supports 5, 6, 7 perceive the horizontal components of the measured force (Fig. 3),

FIG. 2 shows only the ball 9 on the support 3. The other two balls on the supports 2 and 4 are not shown.

The above device of force-measuring elements makes it possible, when transferring forces from the plate to the dynamometers, to exclude

slip friction forces contributing to the error.

This device also eliminates the influence of the component forces on the strain gages, which are not designed to measure these forces, which also reduces the measurement error and allows one to simplify the design of the force-measuring elements to the utmost. Each force-measuring element (beam-dynamometer) in this case perceives only one force factor: the force acting perpendicular to the axis of this dynamometer.

For the system of forces acting on the support plate, six independent equilibrium equations can be composed (see Fig. 3).

Since bond reactions are determined experimentally, six unknowns are included in these equations:

Py, PX, PZ — components of the resultant force;

x, y, z are the coordinates of the point of application of the resultant force.

If we neglect the thickness of the slab, it is obvious that, and it is possible to get along with a system of five equations with five unknowns:

 Px-Re 0 (1)

 Py-R4-Rs 0 (2)

n -Pz + R 1 + R2 + R3 0; (3)

m0x 0; -Pz y + Ra (4)

40

 Pz x-Ra d-Ra. (five)

As the unknowns are separated, the solution to this system is extremely simple:

from (1) from (2) Py R4 + Rs; 45 of (3) Pz Ri + R2 + R3;

R3l

R3i

Rz

Ri + R2 + Rs

from (5) x

R3 d + R2 f Rs d + R2 f

R

Ri + R2 + R3

By knowing the three components of the repulsive force PX, Py, Pz, it is possible to determine both the magnitude of this force and its guides in space.

In addition, as can be seen from the solution of the system, one can determine the coordinates of the point of application of this force and y, i.e. the coordinates of the point of application of the resultant force of the foot pressure on the plate.

It should be noted that the plate rests on spherical bodies — balls that, in plan, form the vertices of an imaginary geometric triangle bounding the plate support plate. Since the plate rests on the balls1 freely, it will be fixed geometrically unchanged (deprived of all six degrees of freedom) only if the measured force is applied inside this triangle. This triangle on the surface of the slab is highlighted with bright paint. Its dimensions can be arbitrarily large, but even with existing tensoplatform sizes, the dimensions of a triangle are quite sufficient, which was shown by the use of a tensoplatform in operation.

Placing the plate on three balls, and not on four, is caused by the desire to simplify the design and interpretation of the oscillograms.

The tensoplatform of the proposed design was manufactured and used in research, it showed reliable and trouble-free operation. Included with it were used amplifier

Topaz-4 direct current and M-041 loop oscilloscope. These devices are compact and have a small weight, and since the platform weighs no more than 8 kg, it is possible to measure not only in the gym, but also in the field conditions - sportdager, at the stadium.

Claims (1)

Tenzoplatform for measuring repulsive effort in sports studies, comprising a platform carrying a plate on supports with strain gauges, characterized in that, in order to improve measurement accuracy, it is equipped with three cantilever beams of equal resistance with strain gauges for measuring horizontal forces. on the platform with the possibility of hinge interaction with the plate by the cantilever plots, with one beam perpendicular to the other two, and the plate is set the support is supported through spherical bodies, the supports are made in the form of cantilever beams of equal resistance, and the spherical bodies form in terms of the vertices of an imaginary geometric triangle bounding the supporting plate of the plate. Aa FIG. 2 ttfopt / xoBdtf / refftw / rrf. L P 1 / 7m / a D / 0lgf0r / ah FIG. five FIG. 6 FIG. eight i t FIG. 7