KR20120057162A - Device and method for measuring center of gravity and moment of inertia - Google Patents

Abstract

PURPOSE: A device for measuring a center of gravity and a moment of inertia and a method for measuring the center of gravity and the moment of inertia using the same are provided to reduce manufacturing costs and to simplifying a structure by measuring a center of gravity and a moment of inertia with one device without moving or installing a measurement object. CONSTITUTION: A device for measuring a center of gravity and a moment of inertia comprises a measuring table(110), a first shaft(120), a second shaft(140), a pivot(150), a bearing(160), a force sensor(170), a fixing unit(180), and a driving unit(190). The measuring table supports measurement objects. The pivot supports the second shaft to be pivotable so that the first and second shafts are inclined by an offset of a center of gravity of the measurement objects. The bearing is installed in the outer circumference of the first shaft so that the first shaft is relatively rotated and supports a moment generated caused by the first and second shafts being inclined. The force sensor supports the bottom surface of the bearing and measures a reaction force with respect to the bearing generated caused by the first and second shafts being inclined. The driving unit generates torsion in a torsion bar by rotating the first shaft when the second shaft is fixed.

Description

DEVICE AND METHOD FOR MEASURING CENTER OF GRAVITY AND MOMENT OF INERTIA}

The present invention relates to a device for measuring the center of gravity and moment of inertia for measuring the center of gravity and moment of inertia and a method of measuring the center of gravity and moment of inertia using the same.

In general, structures such as large satellites and aircraft require precise center of gravity and moment of inertia measurements.

As an example of the apparatus for measuring the center of gravity, there is a structure including a measuring table for installing the measurement object, and three force transducers provided on the bottom of the measuring table. However, according to this structure, the alignment level of the measurement table and the force sensor directly affects the center of gravity measurement value, and there is a problem in that the alignment level of the force sensor must be continuously checked.

In addition, in order to measure the center of gravity and the moment of inertia, they are measured by separate equipment. After measuring the center of gravity, the measured object must be moved to the moment of inertia measurement. When the object to be measured is a large structure, the movement is not easy and there is a troublesome problem.

The present invention is to solve the above problems, to provide a structure of a measuring device that can measure the center of gravity and the moment of inertia in one device.

In order to realize the above object, the present invention provides a measurement table for supporting a measurement object having a center of gravity and an inertia moment, a first shaft fixed to a bottom of the measurement table, and a second shaft connected by the first shaft and the torsion bar. A pivot for pivotably supporting the second shaft such that the first and second shafts are inclined by an shaft, an offset of the center of gravity of the measurement object, and the first shaft may be relatively rotated. A bearing which is installed on an outer circumferential surface of the first shaft so as to support a moment generated as the first and second shafts are inclined, and supports a bottom of the bearing as the first and second shafts are inclined. A force sensor for measuring the reaction force against the bearing, a fixing unit for selectively restraining rotation of the second shaft, and the first shaft when the second shaft is fixed Drives the rotation soft discloses a center-of-gravity and moment of inertia measuring device comprising a drive unit for generating a torsion bar, the torsion.

The first shaft may be installed at the center of the measurement table, and the second shaft and the torsion bar may have the same axis as the first shaft.

The force sensor may be installed at a position separated by a predetermined distance in the X-axis direction from the center of the bearing.

The fixing unit may include a disk coupled to an outer circumferential surface of the second shaft and a brake for pressing the upper and lower surfaces of the disk by a clamping operation.

The driving unit may include a motor generating a rotational force and a tension belt installed between the motor and the first shaft and transmitting the rotational force of the motor to the first shaft.

On the other hand, the present invention is to measure the reaction force due to the X-axis and Y-axis offset of the center of gravity of the measurement object through the rotation of the measurement table, and by operating the fixing unit to restrain the rotation of the second shaft And rotating the first shaft by operating the driving unit, measuring the torsion period of the torsion bar, the weight of the measurement target, the distance in the X axis direction between the support point of the force sensor and the pivot. And calculating a center of gravity of the object to be measured based on the measured value of the force sensor, and calculating a moment of inertia of the object to be measured based on the torsion period. do.

As the reaction force generated by the X-axis offset, an average value of the measured value when the measurement table is rotated by 0 degrees and the measured value when the measurement table is rotated by 180 degrees may be used.

As the reaction force generated by the Y-axis offset, the average value of the measured value when the measurement table is rotated 90 degrees and the measured value when the measurement table is rotated 270 degrees may be used.

The step of calculating the center of gravity and the moment of inertia of the measurement object may be calculated based on the value and the torsion period of the force sensor measured in the non-installed state of the measurement object.

According to the measuring device and the measuring method of the present invention as described above, there is an advantage that the center of gravity and the moment of inertia can be measured in one device without moving and installing the measurement object by using a table rotation.

In addition, according to the present invention, it is a structure that can measure the center of gravity with only one force sensor, it is possible to simplify the structure and reduce the manufacturing cost.

1 is a front view of the device for measuring the center of gravity and moment of inertia according to an embodiment of the present invention.
Figure 2 is a plan view of the center of gravity and moment of inertia shown in Figure 1;

Hereinafter, an apparatus for measuring the center of gravity and moment of inertia related to the present invention and a method for measuring the center of gravity and moment of inertia using the same will be described in more detail with reference to the accompanying drawings.

1 is a front view of a center of gravity and moment of inertia measuring apparatus according to an embodiment of the present invention, Figure 2 is a plan view of the center of gravity and moment of inertia shown in FIG.

1 and 2, the center of gravity and the moment of inertia measuring device 110, the first shaft 120, the second shaft 140, pivot (150, pivot), bearing 160, force sensor 170, the fixing unit 180, and the driving unit 190.

The measurement table 110 is for supporting the measurement object 10 and may have a form of a circular plate.

The first shaft 120 is fixed to the bottom of the measurement table 110 and has a form extending downward from the measurement table 110. The first shaft 120 is installed at the center of the bottom surface of the measurement table 110.

The second shaft 140 is connected by the first shaft 120 and the torsion bar 130. The torsion bar 130 has a lower rigidity than that of the first and second shafts 120 and 140, and the torsion bar 130 is torsionally deformed as the first and second shafts 120 and 140 rotate relative to each other in directions opposite to each other. This will happen. The first shaft 120, the torsion bar 130, and the second shaft 140 are sequentially fixed and have the same axis.

Pivot 150 pivotally supports second shaft 140. Such a structure causes the first and second shafts 120 and 140 to be inclined about the pivot point by an offset of the center of gravity of the measurement object. The second shaft 140 is rotatable about its central axis and at the same time tilted around the support point of the pivot 150. The pivot 150 may be implemented as a structure supported by a separate support structure.

The bearing 160 is installed on the outer circumferential surface of the first shaft 120 and allows the first shaft 120 to rotate relative to the center thereof. When the measurement table 110 is rotated, the first and second shafts 120 and 140 fixed thereto rotate together with the measurement table 110. In addition, the bearing 160 functions to support the moment generated as the first and second shafts 120 and 140 are tilted.

The force sensor 170 supports and fixes the bottom of the bearing 160, and measures the reaction force on the bearing 160 generated as the first and second shafts 120 and 140 are tilted. The force sensor 170 is supported and fixed by a separate support structure, the force sensor 170 is installed at a position separated by a predetermined distance (L) in the X-axis direction from the center of the bearing 160.

The fixing unit 180 functions to selectively restrain the rotation of the second shaft 140. The fixing unit 180 may have a structure including a disk 181 fixedly coupled to an outer circumferential surface of the second shaft 140 and a brake 182 for pressing the upper and lower surfaces of the disk by a clamping operation. However, the fixing unit 180 may be implemented in other configurations as long as the fixing unit 180 restricts the rotation of the second shaft 140. According to the structure of the present embodiment, before the brake 182 is operated, the second shaft 140 can be rotated. However, when the brake 182 is operated, the second shaft 140 is constrained to the brake 182 so that the rotation thereof is prevented. Will be limited.

The driving unit 190 functions to rotationally drive the first shaft 120 when the second shaft 140 is fixed. When the first shaft 120 is rotated in a state in which the rotation of the second shaft 140 is restricted, the first shaft 120 and the second shaft 140 rotate relative to each other in directions opposite to each other, and accordingly, the torsion bar Torsion occurs in the 130.

The driving unit 190 may have a configuration including a motor 191 for generating a rotational force, and a tension belt 192 installed between the motor 191 and the first shaft 120. Accordingly, the tension belt 192 moves according to the driving of the motor 191, and the tension belt 192 transmits the rotational force of the motor 191 to the first shaft 120 by the frictional force with the first shaft 120. To pass. When the torsion bar 130 stops rotation of the motor 191 after the torsion occurs, the torsion bar 130 generates a vibration having a predetermined frequency.

Hereinafter, a method of measuring the center of gravity and the moment of inertia by using the measuring device of the above-described configuration will be described.

First, the reaction force of the bearing 160 and the torsion period of the torsion bar 130 are measured while the measurement object 10 is not mounted. The value measured by the force sensor is based on including both the measurement object and the measurement device. This step is based on the measurement result in the uninstalled state of the measurement object. Is done to get it.

In detail, the force sensor value F _{tare , 0} at 0 ° angle of the measurement table 110 is measured. This is a value due to the moment generated according to the X axis direction offset of the center of gravity of the measurement table 110.

Then, the measurement table 110 is rotated by 90 ° to measure the force sensor value F _{tare , 90} . This is a value due to the moment according to the Y axis direction offset of the center of gravity of the measurement table 110.

And, while rotating the measurement table 110 in sequence by 90 °, the force sensor value at a 180 ° angle of rotation of the measuring table 110 (F _{tare, 180),} and 270 ° the force sensor value at the angle of rotation (F _{tare , 270} ) in turn. F _{tare , 180} is a value due to the X-axis offset of the center of gravity of the measurement table 110, F _{tare , 270} is a value due to the Y-axis direction offset of the center of gravity of the measurement table 110.

In this embodiment, as a measure (F _{tare, X)} due to the X-axis offset was used as the average value of F _{tare, 0} and F _{tare, 180,} a measurement value due to the Y-axis direction, the offset (F _{tare, Y)} The average values of F _{tare , 90} and F _{tare , 270} were used. This is to improve the accuracy of the measurement, it can be represented by the following equation.

F _{tare , X} = (F _{tare , 0} + F _{tare , 180} ) / 2

F _{tare , Y} = (F _{tare , 90} + F _{tare , 270} ) / 2

However, it is possible to use the F _tare, as _X F _{tare, 0} and F _{tare, 180} either the contrast is used as the F _{tare, Y} F _tare, may be used any one of a ₉₀ and F _{tare, 270} .

Next, the fixing unit 180 is operated to constrain the rotation of the second shaft 140. Then, the driving unit 190 is operated in the rotation restraint state of the second shaft 140 to rotate the first shaft 120 by a predetermined angle (for example, 3 °). As a result, torsional deformation occurs in the torsion bar 130, and the torsional period T _tare of the torsion bar 130 is measured by releasing the rotation of the first shaft 120.

Next, the measurement object is installed in the measurement table 110 and the same process as described above is performed.

As described above, through the rotation of the measurement table 110 due to the reaction force (F _{test, X} ) due to the moment due to the X axis direction offset of the center of gravity of the measurement object 10, and the moment due to the Y axis direction offset Measure one reaction force (F _{test, Y} ). Similarly, as the F _test, the average value of the F _{test, 0} and F _{test, 180} as described above, and _X may be used, and the average value of the F _{test, 90} and the F _{test, 270 test} as _{F, Y} may be used. This can be represented by the following equation.

F _{test , X} = (F _{test , 0} + F _{test , 180} ) / 2

F _{test , Y} = (F _{test , 90} + F _{test , 270} ) / 2

However, as the F _{test, X} as shown in the foregoing description F _{test, 0} and the F _test, and can use any of the _180, F _test, a _Y F _test, also possible to use any one of a ₉₀ and F _{test, 270} Do.

Next, after the first shaft 120 is rotated at the same angle (for example, 3 °) in the fixed state of the second shaft 140, the torsion period (T _test ) is measured.

The equation about the moment equilibrium can be established around the support point of the pivot 150, from which a calculation formula for calculating the center of gravity (CG _x , CG _Y ) of the measurement object is derived. The formula is as follows.

CG _x = (F _{test , X} -F _{tare , X} ) * L / W

CG _Y = (F _{test , Y} -F _{tare , Y} ) * L / W

CG _x and CG _Y represent the X and Y coordinates of the center of gravity, respectively, and L represents the distance in the X axis direction between the pivot point and the support point of the force sensor. And, W represents the weight of the measurement object, which can be measured separately before installation on the measurement table (110).

On the other hand, the moment of inertia of the object is proportional to the square of the torsion period around the torsion axis, and based on this, it is possible to derive a calculation formula for calculating the moment of inertia (I _ZZ ) in the vertical axis direction of the measurement object 10. The calculation is shown below.

I _ZZ = C * (T _test ² -T _tare ² )

In the above equation, C represents the moment of inertia constant, which can be obtained by measuring the inertia moment value in advance by measuring the object with a measuring device and inversely calculating it.

Substituting the above measured values into the above-described formula of the center of gravity and the formula of the moment of inertia, the center of gravity (CG _X , CG _Y ) and the moment of inertia (I _ZZ ) of the measurement object 10 can be obtained. Since the values of F _{tare , X} , F _{tare , Y} , and T _tare can be used continuously in subsequent measurements in one measurement, these steps may be omitted in subsequent measurements.

As such, the weight W of the measurement object 10, the distance L in the X-axis direction between the support point of the force sensor 170 and the pivot 150, and the measured value F _{test , X} of the force sensor 170. , F _{test , Y} ) may be calculated based on the center of gravity (CG _X , CG _Y ) of the measurement object 10, the torsion bar 130 of the torsion period (T _test ) of the measurement object 10 The moment of inertia can be calculated.

According to the measuring device and the measuring method described above, there is an advantage that the center of gravity and the moment of inertia can be measured in one device, and it is possible to simplify the structure and reduce the manufacturing cost by using only one force sensor.

In the above description with reference to the accompanying drawings, a method of measuring the center of gravity and moment of inertia and the method of measuring the center of gravity and moment of inertia using the same, the present invention is limited by the embodiments and drawings disclosed herein Various modifications can be made by those skilled in the art within the scope of the technical idea of the present invention.

Claims (9)

A measurement table for supporting a measurement object of the center of gravity and the moment of inertia;
A first shaft fixed to the bottom of the measurement table;
A second shaft connected to the first shaft by a torsion bar;
A pivot pivotably supporting the second shaft such that the first and second shafts are inclined by an offset of the center of gravity of the measurement object;
A bearing installed on an outer circumferential surface of the first shaft to allow the first shaft to rotate relative to each other, and supporting a moment generated as the first and second shafts are tilted;
A force sensor supporting a bottom of the bearing and measuring a reaction force on the bearing generated as the first and second shafts are inclined;
A fixing unit for selectively restraining rotation of the second shaft; And
Apparatus for measuring the center of gravity and moment of inertia comprising a drive unit for generating a torsion to the torsion bar by rotating the first shaft when the second shaft is fixed. The method of claim 1,
The first shaft is installed in the center of the measurement table,
And the second shaft and the torsion bar have the same axis as the first shaft. The method of claim 1,
The force sensor is a center of gravity and moment of inertia measuring device, characterized in that installed in a position separated by a predetermined distance in the X axis direction from the center of the bearing. The method of claim 1, wherein the fixing unit,
A disk coupled to an outer circumferential surface of the second shaft; And
And a brake for pressing the upper and lower surfaces of the disk by a clamping operation. According to claim 1, wherein the drive unit,
A motor generating a rotational force; And
And a tension belt installed between the motor and the first shaft, the tension belt transmitting a rotational force of the motor to the first shaft. In the method of measuring the center of gravity and moment of inertia using the apparatus for measuring the center of gravity and moment of inertia according to claim 1,
Measuring reaction forces due to the X- and Y-axis offsets of the center of gravity of the measurement object through the rotation of the measurement table;
Operating the fixing unit to restrain the rotation of the second shaft;
Operating the driving unit to rotate the first shaft and measuring a torsion period of the torsion bar; And
The center of gravity of the measurement target is calculated based on the weight of the measurement target, the X-axis distance between the support point of the force sensor and the pivot, and the measured value of the force sensor, and the measurement target is based on the torsion period. The method of measuring the center of gravity and the moment of inertia, characterized in that it comprises the step of calculating the moment of inertia. The reaction force of claim 6, wherein the reaction force generated by the X-axis offset is
A method of measuring the center of gravity and the moment of inertia, characterized in that the measured value when the measurement table is rotated 0 degrees and the average value of the measured value when the measurement table is rotated 180 degrees. The reaction force of claim 6, wherein the reaction force generated by the Y-axis offset is
A method of measuring the center of gravity and moment of inertia, characterized in that the measured value when the measurement table is rotated 90 degrees, and the average value of the measured value when the measurement table is rotated 270 degrees. The method of claim 6,
Calculation step of the center of gravity and the moment of inertia of the measurement object,
The method of measuring the center of gravity and the moment of inertia, characterized in that calculated based on the value and the torsion period of the force sensor measured in the uninstalled state of the measurement object.

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