A method for measuring the radial vibration shape of a wind turbine tower using a single laser beam

Abstract

The present invention provides a method for measuring the radial vibration shape of a wind turbine tower using a single laser beam, which relates to the technical field of wind turbine vibration monitoring. The method comprises the following steps: constructing a single laser beam scanning area directly opposite the central axis of the wind turbine tower; exciting the wind turbine tower using a fixed-frequency simple harmonic force and scanning the area with a single laser beam to obtain the steady-state velocity response of each measuring point; calculating the frequency spectrum of each measuring point based on the steady-state velocity response; obtaining the laser forward vibration shape of the wind turbine tower based on the real or imaginary part of the frequency spectrum at each measuring point with the maximum amplitude at a frequency equal to the excitation frequency; and constructing a wind turbine tower vibration shape correction matrix to correct the laser forward vibration shape of the wind turbine tower to a radial vibration shape. This method can measure the radial vibration shape of a wind turbine tower using only a single laser beam.

Description

Technical Field

[0001] The present invention relates to the technical field of wind turbine vibration monitoring, and in particular to a method for measuring the radial vibration shape of a wind turbine tower using a single laser beam. Background Art

[0002] The wind turbine tower is a key component of a wind turbine, supporting the superstructure and absorbing vibration energy. Excessive tower vibration under wind can affect the overall stability of the wind turbine. Therefore, vibration measurement and dynamic characteristic analysis of wind turbine towers are crucial.

[0003] Currently, compared to traditional contact sensors, using scanning laser vibrometers to measure wind turbine tower vibration response offers the advantages of non-contact, distributed, and high-precision. However, conventional two-dimensional laser vibrometers, equipped with only a single laser transmitter, can only measure the vibration shape of the structure within the measurement area in a fixed direction through single laser beam scanning, and cannot measure the radial vibration shape of the wind turbine tower. In contrast, three-dimensional laser scanning vibrometers, equipped with three laser transmitters, can measure the radial vibration shape of the wind turbine tower through synchronous scanning of three laser beams. However, they have disadvantages such as high cost and cumbersome operation. Summary of the Invention

[0004] To solve the above problems, the present invention proposes a method for measuring the radial vibration shape of a wind turbine tower using a single laser beam. This method can measure the radial vibration shape of a wind turbine tower using only a single laser beam.

[0005] To achieve the above objectives, the present invention provides the following technical solutions.

[0006] A method for measuring the radial vibration shape of a wind turbine tower using a single laser beam comprises the following steps:

[0007] Construct a single laser beam scanning area on the wind turbine tower facing the central axis;

[0008] The wind turbine tower is excited by a constant-frequency simple harmonic force, and a single laser beam is used to scan the area to obtain the steady-state velocity response of each measuring point.

[0009] The spectrum of each measuring point is calculated based on the steady-state response of the velocity at each measuring point; the shape of the laser forward vibration of the wind turbine tower is obtained based on the real part or imaginary part of the spectrum at each measuring point with the maximum amplitude when the frequency is equal to the excitation frequency;

[0010] The wind turbine tower vibration shape correction matrix is ​​constructed to correct the wind turbine tower laser forward vibration shape into a radial vibration shape.

[0011] Preferably, the step of constructing a single laser beam scanning area of ​​the wind turbine tower facing the central axis comprises the following steps:

[0012] Align the laser head of the two-dimensional scanning laser vibrometer directly with the central axis of the wind turbine tower, with this direction as the laser forward direction, thereby establishing a single laser beam scanning area directly facing the central axis;

[0013] Among them, the plane formed by the central axis of the wind turbine tower and the laser transmitter head divides the single laser beam scanning area facing the central axis into two equal parts along the circumferential direction.

[0014] Preferably, the acquisition of the wind turbine tower laser forward vibration shape comprises the following steps:

[0015] The wind turbine tower is excited by simple harmonic force, and its excitation frequency is f0;

[0016] Use single laser beam scanning to obtain the steady-state velocity response w[x, y, t] of each measuring point, where t is time, x and y represent the coordinates of the measuring point along the circumferential and axial directions of the scanning area, respectively;

[0017] Calculate the spectrum of w[x,y,t] Where f is the frequency, according to the spectrum of each measuring point at frequency f=f0 The maximum amplitude of the real or imaginary part is used to obtain the forward laser vibration shape W of the wind turbine tower. N [x,y].

[0018] Preferably, constructing the wind turbine tower vibration shape correction matrix comprises the following steps:

[0019] Construct the wind turbine tower vibration shape correction matrix based on the single laser beam scanning area facing the central axis:

[0020]

[0021] Where θ is the angle between the laser beam and the laser forward direction.

[0022] Preferably, the step of correcting the wind turbine tower laser forward vibration shape to a radial vibration shape comprises the following steps:

[0023] The wind tower laser forward vibration shape W N Perform dot multiplication of [x,y] and the correction matrix C[x,y] to obtain the radial vibration shape:

[0024] W R [x,y]=W N [x,y]·C[x,y].

[0025] Beneficial effects of the present invention:

[0026] The present invention proposes a method for measuring the radial vibration shape of a wind turbine tower using a single laser beam. Conventional two-dimensional laser vibrometers are only equipped with a single laser emitter head and can therefore only obtain the vibration shape of the structure in a fixed direction within the measurement area through single laser beam scanning, but cannot obtain the radial vibration shape of the wind turbine tower. The technology disclosed in the present invention can measure the radial vibration shape of a wind turbine tower using only a single laser beam through a vibration shape correction method. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of a single laser beam scanning area of ​​a wind turbine tower facing the central axis according to an embodiment of the present invention;

[0028] Figure 2 This is a diagram of a wind turbine tower model according to an embodiment of the present invention;

[0029] Figure 3 This is a diagram of the laser forward vibration shape of a wind turbine tower according to an embodiment of the present invention;

[0030] Figure 4 7 is a wind turbine tower vibration shape correction matrix diagram according to an embodiment of the present invention;

[0031] Figure 5 3. It is a diagram of the radial vibration shape of the wind turbine tower according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] Example 1

[0034] The present invention provides a method for measuring the radial vibration shape of a wind turbine tower using a single laser beam. Figure 1-5 As shown, the following steps are included:

[0035] S1: Establish a single laser beam scanning area on the wind turbine tower facing the central axis to obtain the laser forward vibration shape.

[0036] I. See Figure 1 The laser head of a 2D scanning laser vibrometer is aligned directly with the central axis of the wind turbine tower. This direction is defined as the laser's forward direction, thereby establishing a single laser beam scanning area aligned with the central axis. The plane formed by the central axis of the wind turbine tower and the laser head divides the single laser beam scanning area aligned with the central axis into two equal sections along the circumferential direction.

[0037] II. Use a constant-frequency simple harmonic force to excite the wind turbine tower, with an excitation frequency of f0. Simultaneously, use a single laser beam to scan and obtain the steady-state velocity response w[x,y,t] of each measuring point, where t is time, and x and y represent the coordinates of the measuring point along the circumferential and axial directions of the scanning area, respectively. Calculate the frequency spectrum of w[x,y,t] Where f is the frequency. The real or imaginary part of the maximum amplitude is used to obtain the laser forward vibration shape W of the wind turbine tower. N [x,y].

[0038] S2: Construct the wind turbine tower vibration shape correction matrix to correct the “laser forward” vibration shape of the wind turbine tower to a radial vibration shape.

[0039] I. Constructing the wind turbine tower vibration shape correction matrix based on the single laser beam scanning area facing the central axis Where θ is the angle between the laser beam and the laser forward direction.

[0040] II. Laser forward vibration shape of wind turbine tower W N [x,y] is multiplied by the correction matrix C[x,y] to obtain the radial vibration shape W R [x,y]=W N [x,y]·C[x,y].

[0041] In this embodiment, the laser sensor is a PSV-400 laser scanning vibrometer produced by Polytec of Germany; and the force exciter is a 4890 modal vibrator produced by B&K of Denmark.

[0042] like Figure 2 As shown, the embodiment uses a steel wind turbine tower model as the embodiment test piece. The wind turbine tower model is 300 mm high, 300 mm in outer diameter, and 8 mm thick. The bottom is welded to a 10 mm thick square steel plate, and is fixed to the vibration isolation platform by bolts at its four corners.

[0043] According to S1, the laser transmitter head of the two-dimensional scanning laser vibrometer is pointed at the central axis of the wind turbine tower model, and this direction is the laser positive direction, thereby establishing a single laser beam scanning area facing the central axis. The plane formed by the central axis of the wind turbine tower and the laser transmitter head divides the single laser beam scanning area facing the central axis into two equal parts along the circumferential direction. The scanning area is 70mm away from the bottom of the specimen, and its circumferential length L x and axial length L yThe diameters of the specimens were all 160 mm. An electromagnetic vibrator was used to apply simple harmonic excitation to the specimen in the radial direction, while a laser vibrometer was used to obtain the steady-state velocity response w[x, y, t] at each measurement point within the single laser beam scanning area facing the central axis. The excitation frequencies were selected to correspond to the natural frequencies of the first four bending modes of the wind turbine tower model: 12.50, 63.75, 100.63, and 258.75 Hz, respectively.

[0044] Use discrete Fourier transform to calculate the spectrum of each measurement point w[x,y,t] The spectrum of each measuring point at the selected excitation frequency The real part of the wind turbine tower model is used to obtain the laser forward vibration shape W N [x,y], such as Figure 3 As shown. Figure 3 Middle Command W N The maximum absolute value of the [x,y] amplitude is 1, and its x and y coordinates are normalized separately.

[0045] Furthermore, according to S2, the single laser beam scanning area facing the central axis is used to determine the angle θ between the laser beam and the laser forward direction corresponding to each measuring point column, thereby constructing the wind turbine tower vibration shape correction matrix like Figure 4 As shown. Figure 4 The x and y coordinates of C[x,y] are normalized separately. The wind tower laser forward vibration shape W N [x,y] is multiplied by the correction matrix C[x,y] to obtain the radial vibration shape W R [x,y], such as Figure 5 As shown. Figure 5 Middle Command W R The maximum absolute value of the [x,y] amplitude is 1, and its x and y coordinates are normalized separately. By comparing the vibration mode obtained by finite element modal analysis of the wind turbine tower model, the radial vibration shape obtained by the present invention is consistent with the shape of the corresponding vibration mode in the measurement area.

[0046] Therefore, the present invention proposes a method for measuring radial vibration deformation of a local area of ​​a wind turbine tower using a single laser beam, which can measure the radial vibration shape of the wind turbine tower using only a single laser beam.

[0047] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for measuring the radial vibration shape of a wind turbine tower using a single laser beam, characterized in that: The following steps are involved: Construct a single laser beam scanning area on the wind turbine tower facing the central axis; The wind turbine tower is excited by a constant-frequency simple harmonic force, and a single laser beam is used to scan the area to obtain the steady-state velocity response of each measuring point. The spectrum of each measuring point is calculated based on the steady-state response of the velocity at each measuring point; the shape of the laser forward vibration of the wind turbine tower is obtained based on the real part or imaginary part of the spectrum at each measuring point with the maximum amplitude when the frequency is equal to the excitation frequency; Construct the wind turbine tower vibration shape correction matrix to correct the wind turbine tower laser forward vibration shape to radial vibration shape; The acquisition of the wind turbine tower laser forward vibration shape comprises the following steps: The wind turbine tower is excited by simple harmonic force, and its excitation frequency is ; Use single laser beam scanning to obtain the steady-state velocity response of each measuring point ,in For time, and Respectively represent the coordinates of the measuring points along the circumferential and axial directions of the scanning area; calculate Spectrum ,in is the frequency, according to the frequency spectrum of each measuring point Down The maximum amplitude of the real or imaginary part is used to obtain the forward vibration shape of the wind turbine tower laser ; The method of constructing a wind turbine tower vibration shape correction matrix comprises the following steps: Construct the wind turbine tower vibration shape correction matrix based on the single laser beam scanning area facing the central axis: in, is the angle between the laser beam and the laser forward direction; The method of correcting the wind turbine tower laser forward vibration shape to a radial vibration shape comprises the following steps: Laser forward vibration shape of wind turbine tower With the correction matrix Performing dot product, we get the radial vibration shape: 。 2. The method for measuring the radial vibration shape of a wind turbine tower using a single laser beam according to claim 1, characterized in that: The method of constructing a single laser beam scanning area of ​​the wind turbine tower facing the central axis includes the following steps: Align the laser head of the two-dimensional scanning laser vibrometer directly with the central axis of the wind turbine tower, with this direction as the laser forward direction, thereby establishing a single laser beam scanning area directly facing the central axis; Among them, the plane formed by the central axis of the wind turbine tower and the laser transmitter head divides the single laser beam scanning area facing the central axis into two equal parts along the circumferential direction.

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