KR101452171B1 - Method of Estimating Displacement of a Tower Structure - Google Patents

Abstract

A method for estimating the displacement of a tower type structure is disclosed. A method for estimating the displacement of a tower type structure according to one embodiment of the present invention comprises: an acceleration measuring step for measuring the acceleration of the structure by attaching an acceleration sensor to the structure; a tilt measuring step for measuring the tilt of the structure by attaching a tilt sensor to the structure; a displacement calculating step for calculating the displacement of the structure by using the acceleration measured in the acceleration measuring step; a correction factor calculating step for calculating a correction factor by converting the displacement calculated in the displacement calculating step and the tilt measured in the tilt measuring step into a frequency area and comparing the first modes of each with each other; and a displacement estimating step for estimating the displacement of the structure by multiplying the tilt measured by the tilt sensor by the correction factor.

Description

TECHNICAL FIELD The present invention relates to a method of estimating displacement of a tower structure,

The present invention relates to a method for estimating displacement of a tower structure, more particularly, to a method of estimating displacement of a tower structure capable of indirectly estimating a displacement of a structure using acceleration and slope information at a desired position will be.

Displacement is a physical quantity that can directly indicate the state of a structure. However, displacement measurements of tower structures such as wind power generators, transmission towers and weather towers are considerably constrained. The methods for displacement measurement can be classified into direct method and indirect method. (Park et al). The direct method is a technique to measure the relative displacement between the device and the wind turbine by installing a device for measuring the displacement at a fixed point and using a Laser Doppler Vibrometer (LDV) (Nassif et al. 2005), Linear Variable Differential Transformer (LVDT) (Lee et al., 2006, Park et al., 2010) and others. However, these devices are very expensive, difficult to install outdoors for long periods of time, and can also be affected by weather conditions.

An indirect method is a method of converting physical quantities such as acceleration, strain and angle into displacement. Since these physical quantities do not require fixed points in the measurement, there is an advantage that the position constraint of sensor installation is less than direct method.

However, when the displacement is estimated through the acceleration, there is a disadvantage that the low-frequency component is greatly amplified due to the measurement noise

To overcome these disadvantages, Lee et al. (2010) developed a displacement estimation algorithm based on FIR (Finite Impulse-Response) filter and verified the validity of the method by applying it to railway bridges. Foss and Haugse (1995) proposed a method of estimating displacement through mode shape transformation of measured strain at various points of a structure and performed an experimental verification through cantilever. Park et al (2013) proposed a fusion equation that combines the advantages of the displacement estimation method with acceleration and strain, and verified its validity through experiments in actual bridges. However, strain and acceleration data are required for measurement, and it is impossible to measure strain when it is difficult to install

SUMMARY OF THE INVENTION The present invention has been made to overcome the above-mentioned problems, and an object of the present invention is as follows.

An object of the present invention is to provide a method of estimating a position of a structure that can estimate a displacement of a structure quickly by a simple method.

The problems of the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, a method of estimating displacement of a tower structure according to an embodiment of the present invention may include an acceleration measurement step, a slope measurement step, a displacement calculation step, a correction coefficient calculation step, and a displacement estimation step.

In the acceleration measurement step, an acceleration sensor may be attached to the structure to measure the acceleration of the structure.

In the tilt measuring step, the inclination of the structure can be measured by attaching a tilt sensor to the structure.

In the displacement calculation step, the displacement of the structure can be calculated using the acceleration measured in the acceleration measurement step.

The correction coefficient calculating step may calculate the correction coefficient by converting the displacement calculated in the displacement calculating step and the slope measured in the slope measuring step into the frequency domain and comparing the respective primary modes with each other.

In the displacement estimation step, the displacement of the structure may be estimated by multiplying the slope measured by the slope sensor by the correction coefficient.

Then, the displacement estimation step may be repeated periodically to periodically observe the displacement of the tower structure.

The acceleration sensor and the tilt sensor may be attached to the uppermost end of the structure.

The damage or change of the structure can be predicted through the type or size of the estimated displacement.

로 나타낼 수 있다.
The correction coefficient

.

The effects of the present invention will be described below.

According to the method for estimating a position of a structure according to an embodiment of the present invention, a correction coefficient is calculated using a first mode of a displacement and a slope of a structure, and the displacement of the structure is estimated by multiplying the slope of the structure by the correction coefficient. The displacement of the structure can be estimated quickly.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims.

The foregoing summary, as well as the detailed description of the preferred embodiments of the present application set forth below, may be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown preferred embodiments in the figures. It should be understood, however, that this application is not limited to the precise arrangements and instrumentalities shown.
1 illustrates a simplified wind turbine model for applying a displacement estimation method of a tower structure according to an embodiment of the present invention;
Figure 2 shows the mode shapes of the three primary frequencies of the wind turbine of Figure 1;
3 is a graph of a load obtained by calculating a thrust of a wind turbine;
4 is a graph showing the results of numerical analysis extracted through sensor fusion; And
5 is an enlarged time-series graph.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood, however, that the appended drawings illustrate the present invention in order to more easily explain the present invention, and the scope of the present invention is not limited thereto. You will know.

In describing the embodiments of the present invention, it is to be noted that elements having the same function are denoted by the same names and numerals, but are substantially not identical to elements of the prior art.

Also, the terms used in the present application are used only to describe certain embodiments and are not intended to limit the present invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

FIG. 1 illustrates a simplified wind turbine model for applying a displacement estimation method of a tower structure according to an embodiment of the present invention. Referring to FIG.

The tower type structure 100 is a structure 100 having a vertical height from the ground. The tower type structure 100 is a wind turbine as shown in FIG. 1.

The method of estimating displacement of a tower structure according to an embodiment of the present invention may include an acceleration measurement step, a displacement calculation step, a slope measurement step, a correction coefficient calculation step, and a displacement estimation step.

In the acceleration measuring step, the acceleration sensor 200 may be attached to the structure 100 to measure the acceleration of the structure 100. Here, the acceleration sensor 200 can generally be attached at the uppermost end where displacement measurement of the tower-like structure 100 is required.

In the tilt measuring step, the tilt sensor 300 may be attached to the structure 100 to measure the tilt of the tower structure 100. Only one tilt sensor 300 may be provided, or a plurality of tilt sensors 300 may be provided.

In the case where only one tilt sensor 300 is provided, the tilt sensor 300 can be disposed at the uppermost position, which is the same position as the acceleration provided on the tower structure 100.

When a plurality of tilt sensors 300 are provided, the tilt sensors 300 adjacent to each other may be attached to each other along the longitudinal direction of the structure 100.

In the displacement calculation step, the displacement of the structure 100 can be calculated using the acceleration measured in the acceleration measurement step. The displacement of the structure 100 can be obtained by integrating the acceleration of the structure 100 measured from the acceleration sensor 200 twice by integrating the acceleration twice.

The relationship between the slope and the displacement can be expressed by Equation 1 and Equation 2 as follows by way of the mode shape.

Where φ and ψ are the mode shapes of displacement and rotation angle, respectively, and q is the generalized coordinate. The generalized coordinates can be obtained from the measured rotation angle information as shown in Equation (3).

Here, + means pseudo inverse.

From the equations (1) and (3), the displacement is obtained by the following equation (4), and it can be seen that there is a linear relationship between the rotation angle and the displacement.

However, since the unknown integral constant is generated in the process of integrating the acceleration, it is difficult to calculate the accurate displacement of the structure 100.

Therefore, in the correction coefficient calculating step, the slope measured in the slope measuring step and the displacement calculated in the displacement calculating step can be converted into the frequency domain, respectively, and the correction coefficients? Can be calculated by comparing the respective primary modes.

Here, the correction coefficient? Is expressed by the following equation (5).

은 1차 고유진동수이며,

은 가속도의

에서의 주파수 영역에서의 크기,

은 수학식 4를 통해 기울기로부터 추정된 변위의

에서의 주파수 영역에서의 크기를 의미한다.here

Is a first-order natural frequency,

Of acceleration

The size in the frequency domain,

≪ RTI ID = 0.0 > (4) < / RTI >

In the frequency domain.

In the displacement estimation step, the displacement of the structure 100 can be calculated by multiplying the slope measured by the tilt sensor 300 by the correction coefficient alpha as shown in Equation (6) below.

The correction coefficient alpha is a value that does not change as long as no damage occurs to the structure 100. If the correction coefficient alpha is calculated only once for the first time, The displacement of the structure 100 can be estimated simply by multiplying the slope value by the correction coefficient alpha.

Periodically, the slope of the structure 100 is measured, and the displacement of the structure 100 is periodically measured by multiplying the slope of the structure 100 by the correction coefficient alpha, and the damage or the damage of the structure 100 through the shape or size of the estimated displacement The change can be predicted.

In the case of restoring to the displacement directly through the tilt sensor 300, it is difficult to measure the dynamic displacement due to the sensor noise, and a considerable error occurs in the estimated value due to the error of the mode shape. Therefore, the displacement can be estimated by fusing the data obtained from the acceleration sensor 200 and the tilt sensor 300 as described above.

In order to fuse the two physical quantities, a minimization function such as Equation (7) below can be used.

을 제외하고는 단위행렬을 갖는다. Lc는 미분연산자이며 수학식 8로 표현된다.La is a weighted diagonal matrix,

And has a unitary matrix. Lc is a differential operator and is expressed by Equation (8).

로 정의되었으며

는 첫 번째 고유주기에 해당하는 데이터 개수이다. 수학식 7을 u에 대해 미분하여 정리하면 다음의 수학식 9와 같이 가속도와 회전각에 대한 수식을 얻을 수 있다.λ is the Tikhonov normalization constant and Lee et al. (2010) by

And

Is the number of data corresponding to the first natural period. If Equation (7) is differentiated with respect to u, the equations for the acceleration and the rotation angle can be obtained as shown in the following Equation (9).

,

그리고

이다.here,

,

And

to be.

For the numerical verification of the proposed method, numerical analysis was carried out on the following simple simplified wind turbine model as a tower type structure. The numerical model is modeled as shown in Fig. 1 and Table 1 below with reference to the specifications of the 5 MW wind turbine proposed by NREL. The height of the wind turbine is 90 m, and natural frequencies are 0.33 Hz first, 3.44 Hz second, and 10.33 Hz third.

In Table 1, D1 is the diameter of the uppermost end of the wind turbine and D2 is the diameter of the lowermost end.

Fig. 2 is a mode shape of the main three natural frequencies of the wind turbine of Fig. 1; Here, the mode shape of the tilt is differentiated by interpolating the mode shape of the displacement.

The upper part of the wind turbine was modeled by the concentrated mass of the blades and the nacelle, and the upper wind load was obtained through the wind turbine simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence) developed by NREL.

After obtaining the thrust of a 5 MW wind turbine with 20 m / s wind speed, we applied the hanning window as shown in Fig. 3 and applied it to the numerical analysis.

In order to perform the numerical analysis, the layout of the tilt sensor 300 in total four cases is considered. The sensors are arranged as shown in Table 2 below and in all cases the acceleration sensor 200 is placed at the top of the wind turbine requiring displacement measurement.

FIG. 4 is a graph showing a result of numerical analysis extracted through sensor fusion, and FIG. 5 is an enlarged time series graph.

The results of the numerical analysis are shown in Figs. 4 and 5. FIG. 4 shows the results of Case 1 through Case 4 extracted through the sensor fusion and the results obtained when only one tilt sensor 300 is used. When only one tilt sensor 300 is used, the similar size is slightly different because it can not correct the error of the mode shape properly. Referring to FIG. 5, it can be seen that all cases of Case 1 to Case 4 are substantially similar to true values. However, even if the use of the tilt sensor 300 is increased, the accuracy of the result is not necessarily improved.

These results are quantitatively listed in Table 3 above. Table 3 summarizes the case of using data fusion and tilt sensor 300 only and compares the accuracy with correlation coefficient and RMS (root mean square) error. The RMS error is defined as: < EMI ID = 10.0 >

When using only the tilt sensor 300, the correlation coefficient is not significantly different from that of the sensor fusion in all cases and shows a high correlation coefficient. That is, the displacement estimated by the tilt sensor 300 alone has a waveform substantially similar to the actual value. However, it is found that there is a large difference from the actual value as a result of calculating the error defined in Equation (6), and it can be seen that there is an error in the scale of the displacement due to the error of the mode shape. It can be seen that the result of the sensor fusion is considerably smaller than that of the tilt sensor 300 alone because it corrects the error of the mode shape through the fusion with the acceleration.

Also, it can be seen that the increase of the number of used sensors does not necessarily improve the accuracy, and it can be seen that the sensor 1 (Case 1) estimates the displacement sufficiently for engineering purposes.

Therefore, when the tilt sensor 300 and the acceleration sensor 200 are fused, the error of the mode shape can be corrected, so that the scale can be estimated with a suitable displacement. Only one tilt sensor 300 and one acceleration sensor 200 are used It is possible to estimate the displacement very accurately.

It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or scope of the invention as defined in the appended claims. It is obvious to them. Therefore, the above-described embodiments are to be considered as illustrative rather than restrictive, and the present invention is not limited to the above description, but may be modified within the scope of the appended claims and equivalents thereof.

100: Structure
200: Acceleration sensor
300: tilt sensor

Claims (5)

An acceleration measuring step of measuring an acceleration of the structure by attaching an acceleration sensor to the structure;
A tilt measuring step of measuring a tilt of the structure by attaching a tilt sensor to the structure;
A displacement calculating step of calculating a displacement of the structure using the acceleration measured in the acceleration measuring step;
A correction coefficient calculating step of converting the displacement calculated in the displacement calculating step and the slope measured in the slope measuring step into a frequency domain and comparing the respective primary modes with each other to calculate a correction coefficient; And
A displacement estimation step of estimating a displacement of the structure by multiplying the slope measured by the slope sensor by the correction coefficient;
And estimating the displacement of the tower structure. The method according to claim 1,
And estimating the displacement of the tower structure periodically. The method according to claim 1,
Wherein the acceleration sensor and the tilt sensor are attached to the uppermost end of the structure. 3. The method of claim 2,
A method for estimating a displacement of a tower structure that predicts damage or change of the structure through the type or size of the estimated displacement. The method according to claim 1,
Wherein the correction coefficient

A method for estimating displacement of a tower structure.

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