KR20160068458A - Load estimation using strain measurement - Google Patents

Abstract

According to an embodiment of the present invention, an apparatus to estimate a load at an arbitrary point using a strain measurement comprises: (a) (S110) a load application step of applying a series of unit vertical loads to n points of a structure having a strain measurement sensor attached; (b) (S120) a strain measurement step which the strain measurement sensor measures a primary strain data due to the series of unit vertical loads; (c) (S130) a correlation coefficient calculation step of calculating a correlation coefficient with respect to a linear relationship between the series of unit vertical loads and primary strain data; and (d) (S140) an unknown load calculation step of calculating an unknown load by applying the correlation coefficient to a secondary strain measured at the strain measurement sensor when the unknown load is applied to the n points.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a load estimation method using strain measurement,

The present invention relates to an apparatus and method for estimating an arbitrary point load using strain measurement, wherein the structure is assumed to be a linear system, and only the strain is measured by using the relationship of strain and load measured at an arbitrarily designated position, And more particularly, to a device and a method for estimating a load of a position.

It is very important to evaluate the structural integrity of a structure objectively because the load acting on a specific point in the structure may cause deformation and destruction of the structure. In particular, safety and accuracy must be given priority because safety is a top priority as hundreds of people are aboard structures such as aircraft.

Conventionally, a method of attaching a load cell to directly measure a load at a point where a load acts is used. However, it is often difficult to attach the load cell according to the shape of the structure and the environmental conditions, and there is a problem that the installation process is complicated and there are many practical limitations.

By means of the apparatus and method for estimating a load at an arbitrary point by using the strain measurement of the present invention, the load applied to an arbitrary point of the structure is accurately measured without being influenced by the environmental conditions of the shape of the structure.

(A) a load applying step (S110) in which a series of unit vertical loads are applied to n points of a structure to which a strain measuring sensor is attached; (b) a strain measuring step (S120) in which the strain measuring sensor measures primary strain data due to the series of unit vertical loads; (c) calculating a correlation coefficient for a linear relationship between the series of unit vertical loads and the first strain data; And (d) calculating an unknown load by applying the correlation coefficient to the secondary strain measured by the strain measuring sensor when an unknown load is applied to the n points.

Further, the structure may be a vehicle, and the n points may be any point on the underside of the vehicle.

In the load applying step (S110), the series of unit vertical loads are applied by the load applying unit.

Preferably, the correlation coefficient calculation in the correlation coefficient calculation step (S130) is performed by a computer.

Further, in the unknown load calculation step (S140), the calculation of the unknown load is performed by a computer.

And, in the unknown load calculation step (S140), the unknown load is applied by the load applying unit.

Preferably, the method of estimating a load at an arbitrary point using the strain measurement is a process after step (c), wherein a correlation coefficient for a linear relationship between the n points and the series of unit vertical loads and the first strain data is calculated as data And a storage step (S135) of base-forming (data base).

The present invention can also provide a recording medium storing a program for causing a computer to execute a method of estimating a load at an arbitrary point using the strain measurement.

The present invention can also provide an apparatus for estimating a load at an arbitrary point using strain measurement, which includes the recording medium,

According to an aspect of the present invention, there is provided a load estimation apparatus comprising: the recording medium; N strain measurement sensors attached to any n points of the structure; A load applying unit for applying a series of unit vertical loads to n points of the structure to which the strain measuring sensor is attached; A first arithmetic processing unit for calculating a correlation coefficient for a linear relationship between the series of unit vertical loads and the primary strain data measured by the strain measuring sensors upon application of the series of unit vertical loads; A storage unit for storing the n points and the correlation coefficient calculated by the arithmetic processing unit; A second arithmetic processing unit for calculating an unknown load when an unknown load is applied using the correlation coefficient stored in the storage unit; And a display unit for displaying the calculated unknown load on the screen so that the unknown load can be visually confirmed.

According to the apparatus and method for estimating a load at an arbitrary point using the strain measurement of the present invention, it is possible to accurately measure a load at any point of the structure without affecting the shape or environmental condition of the structure.

1 to 3 are flowcharts of a method for estimating an arbitrary point load using strain measurement according to an embodiment of the present invention.
FIG. 4 illustrates n points of a structure to which a strain measurement sensor is attached in a method of estimating an arbitrary point load using strain measurement according to an embodiment of the present invention.
5 is a block diagram of an arbitrary-point load estimating apparatus using strain measurement according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Prior to the description, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and should be construed in accordance with the technical concept of the present invention.

Throughout this specification, when an element is referred to as "including" an element, it is understood that it may include other elements as well, without departing from the other elements unless specifically stated otherwise.

In each step, the identification code is used for convenience of explanation, and the identification code does not describe the order of the steps, and each step may be performed differently from the stated order unless clearly specified in the context. have. That is, each of the steps may be performed in the same order as the specified order, substantially simultaneously or in the reverse order.

1 to 3 are flowcharts of a method for estimating an arbitrary point load using strain measurement according to an embodiment of the present invention.

(A) a load application step (S110) in which a series of unit vertical loads are applied to n points of the structure to which the strain measurement sensor 20 is attached, (b) a strain measuring step (S120) of measuring the strain data due to the series of unit vertical loads by the strain measuring sensor (20) (c) calculating a linear strain amount A correlation coefficient calculating step of calculating a correlation coefficient with respect to the relationship; and (d) when the unknown load is applied to the n points, the correlation coefficient is applied to the secondary strain measured by the strain measuring sensor 20 And an unknown load calculation step (S140) for calculating an unknown load.

In the load applying step S110, the series of unit vertical loads are applied to n points of the structure to which the strain measuring sensor 20 is attached by the load applying unit 30. [ When said series of units is the vertical load, the load applied to each of the n points _{P 1 P 2 ... P j,} (j = n) in the sense of the present invention, [P ₁ P ₂ ... P _j ] means that a load other than 0 is applied to only one component, and a component other than 0 is changed and added. Specifically, a series of unit vertical loads is a set of n [P ₁ P ₂ ... P _j ], for example, {[P 0 ... 0 _{. . .} 0], [0 ... 10M ... 0] _{. . .} 0] ... [0 0 ... 0] _{. . .} 10M]}. Here, the unit of load may be Newton (N).

In the strain measurement step S120, when a series of unit vertical loads are applied, n pieces of primary strain data are measured in each of the strain measuring sensors 20 attached to n points. That is, the primary strain data are [ε _1, ε ₂ ,. _{. .} ε _i ], (i = n). Specifically, when a series of unit vertical loads are applied in turn, the primary strain data is measured for each unit vertical load.

A strain gauge may be used as the strain measuring sensor 20.

In the correlation coefficient calculation step (S130), a correlation coefficient for a linear relationship between a series of unit vertical loads and the primary strain data is calculated. The structure can be defined as a linear system according to the structure and environment as shown in Equation (1) below.

...... (1)

...... (One)

As noted above, [ε _1, ε ₂ ,. _{. .} ε _i ] is strain data, [P ₁ P ₂ ... P _j ] means load, and α _ij means strain data and load correlation coefficient. Here, since the load is applied at n points and the strain is measured, i and j have values of n.

For example, a series of unit vertical loads {[P ₁ 0 ... 0 _{. . .} 0], [0 P ₂ ... 0] _{. . .} 0] ... [0 0 ... 0] _{. . .} P _j ]} and the primary strain data [ε _1, ε ₂ ,. _{. .} ε _i ] is applied to the linear system, all of the n ² correlation coefficients α _ij can be calculated.

On the other hand, in the correlation coefficient calculation step (S130), correlation coefficient calculation can be performed by a computer.

In the storing step S135, correlation coefficients for n points and the linear relationship between the series of unit vertical loads and the primary strain data are converted into data bases and stored. More specifically, when n points are converted into a database, they can be stored as nodes. Then, n ² correlation coefficients? _Ij calculated according to the positions of n points on the structure are all databaseized. It is possible to estimate the load using a database-based correlation coefficient without calculating the correlation coefficient every time the load is estimated. However, since there is a possibility that aging of the structure progresses with time, the correlation coefficient needs to be updated at an appropriate time interval.

In the unknown load calculation step S140, when an unknown load is applied to n points, an unknown load is calculated by applying the correlation coefficient stored in the secondary strain data measured by the strain measurement sensor 20. [

When an unknown load is applied to n points, the strain measuring sensor 20 calculates the secondary strain data [? ₁ ,? ₂ ,? _{. .} ε _i ] is measured. Thereafter, the correlation coefficients? _Ij And the measured secondary strain data are applied to the above equation (1), n unknown loads can be calculated.

On the other hand, in the unknown load calculation step (S140), the calculation of the unknown load can be performed by a computer.

In the notification step S150, when the unknown load calculated through the unknown load calculation step S140 exceeds the appropriate limit load of the structure, it is determined that there is an abnormality, and an alarm means is generated to notify the operator of the abnormality can do. For example, if the structure is a vehicle, it can be notified to the driver, and in the case of a bridge or a building, it can be notified to the manager.

At this time, the warning means may be a light emission using a lamp, a warning sound through a speaker, a recognition method through a display, or the like.

Hereinafter, numerical values and results obtained by simulation will be described, for example, in the case where n is four to help understand the invention.

FIG. 4 illustrates four points of a structure to which the strain measurement sensor 20 is attached in the method of estimating a point at any point using strain measurement according to an embodiment of the present invention.

P1, P2, P3, P4] = {[10MN 0 0 0], [0 10MN 0 0], and [0 0MN 0 0] at the four points, 0 0 10MN 0] [0 0 0 10MN]} is applied. The measurement values of the four strain measuring sensors 20 are summarized in Table 1 below.

<Table 1. Strain measured when a series of unit vertical loads are applied at four points>

Table 1 shows the unit vertical loads [P1, P2, P3, P4] = {[ε _1, ε _2, ε _3, ε ₄ ] 10M 0 0], [0 0 0 0 0], [0 0 10M 0] [0 0 0 10M] are applied. By applying the above sixteen strain data values and a series of unit vertical loads to the equation (1), the correlation coefficient α _ij can be obtained as shown in the following equation (2).

... (2)

... (2)

Therefore, the linear system of the structure on which the simulation is performed is defined by the following equation (3).

... (3)

... (3)

As described above, four points and four ² correlation coefficients? _Ij Are all databaseized. Therefore, when an unknown load is applied, the load can be estimated using the database-based correlation coefficient and the measured strain.

Table 2 summarizes the measured secondary strain data when an optional load [P1, P2, P3, P4] = [3M 2M 1.1M 4.3M] is applied.

<Table 2. Strain measured when an arbitrary load is applied to four points>

When an arbitrary load [P1, P2, P3, P4] is obtained by applying the strain measured in Table 2 to the above equation (3) and using an inverse matrix calculation algorithm or the like, an arbitrary load value and an error .

Therefore, according to the load estimation method of arbitrary points using the strain measurement of the present invention, it is possible to accurately measure the load at any point of the structure without affecting the shape of the structure.

5 is a block diagram of an arbitrary-point load estimating apparatus using strain measurement according to the present invention.

The load estimation apparatus according to the present embodiment includes a recording medium 10, n strain measurement sensors 20 attached to arbitrary n points of the structure, series of n points of the structure to which the strain measurement sensor 20 is attached A load applying unit 30 for applying a unit vertical load of the strain sensor 20 to the strain measuring unit 20 and a linear correlation unit for calculating a linear relationship between a series of unit vertical loads and the primary strain data measured by the strain measuring sensors 20 upon application of the series of unit vertical loads A storage unit 50 for storing the correlation coefficients calculated by the n points and the arithmetic processing unit, and a storage unit 50 for storing correlation coefficients calculated at the n points and the arithmetic processing unit, A second arithmetic processing unit 60 for calculating an unknown load, and a display unit 70 for displaying the calculated unknown load on the screen so that the calculated unknown load can be visually confirmed.

The system may further include a notification unit that determines that there is an abnormality when the calculated unknown load exceeds a predetermined limit load of the structure, and notifies the operator of the abnormality by generating a warning unit.

Therefore, the load estimation method and apparatus according to the present embodiment according to the present embodiment can objectively evaluate the structural integrity of the structure, thereby improving the reliability and accuracy of the structure.

The present invention is not limited to the above-described specific embodiment and description, and various changes and modifications may be made by those skilled in the art without departing from the scope of the present invention as claimed in the claims. And such modifications are within the scope of protection of the present invention.

10: recording medium 20: strain measuring sensor
30: load application unit 40: first arithmetic processing unit
50: storage unit 60: second arithmetic processing unit
70:

Claims (9)

(a) a load applying step (S110) in which a series of unit vertical loads are applied to n points of a structure to which a strain measuring sensor is attached;
(b) a strain measuring step (S120) in which the strain measuring sensor measures primary strain data due to the series of unit vertical loads;
(c) a correlation coefficient calculation step (S130) of calculating a correlation coefficient for a linear relationship between the series of unit vertical loads and the primary strain data, and
(d) calculating an unknown load by applying the correlation coefficient to the secondary strain measured by the strain measuring sensor when an unknown load is applied to the n points, A method for estimating a load at an arbitrary point.
The method according to claim 1,
Wherein the structure is a vehicle and the n points are arbitrary points on the underside of the vehicle.
The method according to claim 1,
Wherein the series of unit vertical loads are applied by the load applying unit in the load applying step (S110).
The method according to claim 1,
Wherein the correlation coefficient calculation in the correlation coefficient calculation step (S130) is performed by a computer.
The method according to claim 1,
Wherein the calculation of the unknown load in the unknown load calculation step (S140) is performed by a computer.
The method according to claim 1,
Wherein the unknown load is applied by the load applying unit in the unknown load calculating step (S140).
The method according to claim 1,
A method for estimating a load at an arbitrary point using the strain measurement
As a process after step (c)
And storing (S135) databaseing (S135) a correlation coefficient for a linear relationship between the n points and the series of unit vertical loads and the first strain data, A method for estimating a load at an arbitrary point.
A recording medium storing a program for causing a computer to execute a method of estimating a load at an arbitrary point using strain measurement according to any one of claims 1 to 7.
9. A recording medium according to claim 8;
N strain measurement sensors attached to any n points of the structure;
A load applying unit for applying a series of unit vertical loads to n points of the structure to which the strain measuring sensor is attached;
A first arithmetic processing unit for calculating a correlation coefficient for a linear relationship between the series of unit vertical loads and the primary strain data measured by the strain measuring sensors upon application of the series of unit vertical loads;
A storage unit for storing the n points and the correlation coefficient calculated by the arithmetic processing unit;
A second arithmetic processing unit for calculating an unknown load when an unknown load is applied using the correlation coefficient stored in the storage unit;
A display unit for displaying the calculated unknown load on a screen so that the unknown load can be visually confirmed;
And a load estimation unit for estimating an arbitrary point load using strain measurement.

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