Optical fiber sensing type acceleration sensor for wind driven generator

Abstract

The utility model relates to the technical field of fiber grating sensing, in particular to an optical fiber sensing type acceleration sensor for a wind driven generator. The device comprises an acceleration sensor and a tail fiber, and the acceleration sensor comprises a shell, and a fiber grating and a sensitive element which are arranged in the shell; the fiber bragg grating comprises a first grating part, a second grating part and a tail fiber part, the first grating part, the second grating part and the tail fiber part are sequentially connected in series, and the tail fiber part penetrates through the shell and then is connected with the tail fiber; the sensitive element comprises a first sensitive element used for driving the first grating part to change in the first direction and a second sensitive element used for driving the second grating part to change in the second direction, and the first direction is perpendicular to the second direction. Acceleration sensing in at least two directions is achieved through one optical fiber, the number of optical fibers and connectors is reduced, the overall structure of the sensor can be more compact, and the sensor is suitable for a wind driven generator needing lighter and smaller sensors for blade vibration.

Description

Technical Field

[0001] This utility model relates to the field of fiber optic grating sensing technology, and in particular to a fiber optic sensing accelerometer for wind turbines. Background Technology

[0002] Fiber Bragg grating (FBG) sensors are instruments that use fiber Bragg grating sensing technology to measure physical quantities (stress, strain, temperature, vibration, etc.). Changes in external physical quantities cause a change in the center wavelength of the light reflected by the Bragg grating. By analyzing this wavelength change, the fiber Bragg grating sensor can monitor the state of the object being measured. FBG accelerometers have a wide range of applications, including bridges, earthquake monitoring, and wind turbines. They offer advantages such as lightning protection, electromagnetic interference resistance, and the ability to be distributed.

[0003] Most wind farms are located in sparsely populated, harsh environments with complex climates. Under these harsh conditions, blades are prone to bulging, cracking, delamination, and even breakage during prolonged fatigue operation. As the primary component of a wind turbine for absorbing wind energy, the structural damage to the blades directly affects the turbine's power generation efficiency and operational safety. Therefore, blade fault monitoring is essential. Currently, the mainstream method uses electrical signal-based accelerometers for blade monitoring. However, these are relatively weaker than optical signals in terms of lightning protection, are easily affected by electromagnetic environments, and are not suitable for multi-point distributed measurements.

[0004] Patent document CN111879966A discloses a multi-directional fiber optic accelerometer sensor. Its housing contains accelerometers for three different directions: x, y, and z. It determines the direction of an object's motion and the magnitude of acceleration along that direction by detecting changes in the center wavelength of the light returning from the fiber optic cables in these three directions, thus achieving multi-directional detection. This prior art uses three fiber optic cables to accommodate the three different directions, increasing the sensor's size and complexity. For structural adhesive coating installations inside wind turbine blades, which can easily reach tens of meters in length, the three fiber optic cables are costly, and the large amount of adhesive applied during installation further increases costs. Utility Model Content

[0005] This invention aims to solve the above problems by providing a fiber optic accelerometer that is small in size, lightweight, and has good lightning protection, suitable for wind turbines.

[0006] The technical solution of this utility model is to provide a fiber optic accelerometer for wind turbines, including an accelerometer and a pigtail. The accelerometer includes a housing, a fiber optic grating, and a sensing element disposed within the housing. The fiber optic grating includes at least one first grating section, at least one second grating section, and a pigtail section, which are connected in series. The pigtail section passes through the housing and is connected to the pigtail. The sensing element includes at least one first sensing element for driving the first grating section to change along a first direction, and at least one second sensing element for driving the second grating section to change along a second direction. The first and second directions are perpendicular.

[0007] As a preferred embodiment of this invention, both the first and second sensitive elements are cantilever beam structures. The cantilever beam structure includes a mounting base, a cantilever beam, and an inertial mass block connected in sequence. The mounting base is connected to the housing, and the inertial mass block is suspended inside the housing. The inertial mass block of the first sensitive element senses vibration in a first direction, and the inertial mass block of the second sensitive element senses vibration in a second direction. The two ends of the first or second grating section are respectively connected to the mounting base and the inertial mass block, and the body of the first or second grating section does not contact the cantilever beam.

[0008] As a preferred embodiment of this invention, the mounting base and the inertial mass block are respectively provided with grooves into which the first grating portion or the second grating portion can be inserted.

[0009] As a preferred embodiment of this invention, the groove is provided with an adhesive fixing groove.

[0010] As a preferred embodiment of the present invention, the housing is further provided with a limiting element, the limiting element including at least one first limiting member for limiting the movement distance of the first sensitive element in the first direction, and at least one second limiting member for limiting the movement distance of the second sensitive element in the second direction.

[0011] As a preferred embodiment of the present invention, the housing includes a main body having a receiving cavity for accommodating the fiber optic grating and the sensitive element, and a plurality of fixing ears disposed on the main body, the plurality of fixing ears being uniformly arranged in a ring around the center of the main body.

[0012] As a preferred embodiment of this invention, the housing is filled with damping fluid.

[0013] As a preferred embodiment of this invention, a fiber optic temperature sensor is provided between the accelerometer and the pigtail.

[0014] The beneficial effects of this utility model are:

[0015] 1. This application employs a fiber Bragg grating accelerometer sensor for all-optical-path measurement and a non-metallic housing, improving blade safety during thunderstorms. It deploys acceleration sensing in at least two directions to meet the acceleration measurement requirements for wind turbine blade flapping and swaying. Furthermore, this application utilizes a single fiber Bragg grating to achieve acceleration sensing in at least two directions, allowing the accelerometer to share a single pigtail across both axes. This reduces the number of optical fibers and connectors, resulting in: first, a more compact overall sensor structure, suitable for wind turbines requiring lighter and smaller sensors for blade vibration; second, reduced equipment and installation costs; third, shared pigtail transmission ensures consistent signal response time through the same optical path, minimizing signal delay differences between channels. This allows for more accurate synchronization of acceleration data across multiple axes when measuring multi-axis composite vibrations, improving the accuracy of dynamic composite vibration measurements of wind turbine blades; and fourth, easier integration into fiber optic networks for multi-point vibration detection of wind turbines, reducing system complexity.

[0016] 2. In some embodiments, the accelerometer of this application can also be used for triaxial or even multiaxial acceleration measurement in other devices, all sharing a single pigtail, thus reducing the number of optical fibers and connectors.

[0017] 3. In some embodiments, damping fluid is filled inside the housing to reduce measurement noise and abnormal vibration of sensitive elements, thereby improving the accuracy of acceleration measurement. Attached Figure Description

[0018] Figure 1 This is a front view of a fiber optic accelerometer sensor for wind turbines.

[0019] Figure 2 This is a side view of a fiber optic accelerometer sensor for wind turbines.

[0020] Figure 3 This is a schematic diagram of the internal structure of an accelerometer in a fiber optic accelerometer for a wind turbine.

[0021] Figure 4 This is a front view of a cantilever beam structure in a fiber optic accelerometer for a wind turbine.

[0022] Figure 5 This is a side view of a cantilever beam structure in a fiber optic accelerometer for a wind turbine.

[0023] Figure 6 This is a top view of a cantilever beam structure in a fiber optic accelerometer for a wind turbine.

[0024] In the figure: accelerometer 1, housing 11, main body 111, fixing lug 112, first grating part 121, second grating part 122, pigtail part 123, first sensing element 131, second sensing element 132, mounting base 133a, cantilever beam 133b, inertial mass block 133c, groove 133d, first limiting member 141, second limiting member 142, fiber optic grating temperature sensor 2, pigtail 3. Detailed Implementation

[0025] The following are specific embodiments of the present invention, and the technical solution of the present invention will be further described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0026] A fiber optic accelerometer for wind turbines, such as Figure 1 As shown, it includes an accelerometer 1 and a pigtail 3.

[0027] The accelerometer 1 includes a housing 11, and a fiber Bragg grating and a sensing element disposed within the housing 11. The housing 11 is a non-metallic housing, and its structure is not limited, as long as it has a cavity for accommodating the fiber Bragg grating and the sensing element. Figure 1 and Figure 2 As shown, the housing 11 includes a cubic body 111, which is hollow inside to form an accommodating cavity. The body 111 includes a back side for connecting to the wind turbine blades, a front side opposite the back side, and several side sides. In some embodiments, the back side and side wall thickness of the housing 11 are thickened to accommodate the sensitive element and improve the installation rigidity to enhance the accuracy of acceleration measurement.

[0028] The main body 111 can be installed to the wind turbine blade in various ways, such as by adhesive bonding, where adhesive is applied to the back of the main body 111 and then bonded to the wind turbine blade. In some embodiments, such as... Figure 1 As shown, the housing 11 also includes a plurality of fixing ears 112 disposed on the main body 111. The plurality of fixing ears 112 are evenly arranged in a ring around the center of the main body 111, for example... Figure 1 In the cube, the four sides of the main body 111 are provided with fixing ears 112. For example... Figure 2 As shown, the back of the mounting ear 112 is flush with the back of the main body 111, and the mounting ear 112 has a round hole. Based on this, the mounting ear 112 can be connected to the wind turbine blade using screws. The evenly distributed mounting ears 112 ensure installation stability. If necessary, adhesive can also be applied to the back of the main body 111 to assist in installation. Alternatively, both the mounting ear 112 and the main body 111 can be connected to the wind turbine blade using adhesive. The mounting ear 112 increases the contact area of ​​the adhesive, which can increase the bonding strength of the sensor.

[0029] Since it is designed for monitoring the vibration of wind turbine blades, it is necessary to measure vibration in both flapping and swaying directions. Therefore, if Figure 3 As shown, the fiber optic grating in the housing 11 includes at least one first grating section 121 and at least one second grating section 122. The first grating section 121 and the second grating section 122 are formed by etching gratings on an optical fiber, and the first grating section 121 and the second grating section 122 are connected in series. The first grating section 121 and the second grating section 122 are used to change the center wavelength of their reflection due to strain. By processing the center wavelength, the external acceleration signal can be calculated. In some embodiments, the fiber optic grating may also include a third grating section, a fourth grating section, etc., to be suitable for triaxial and multiaxial acceleration measurement. The fiber optic grating also includes a pigtail section 123, which passes through the housing 11 and is connected to a pigtail 3 to transmit the optical signal to the first grating section 121 and the second grating section 122, and transmit the reflected optical signal back to the detection device. Thus, acceleration sensing in at least two directions can be achieved using a single optical fiber. In some embodiments, to prevent the pigtail portion 123 from bending and being damaged, the main body 111 is provided with a reinforcing sleeve fitted over the pigtail portion 123.

[0030] like Figure 3 As shown, secondly, in order to cause strain in the first grating section 121 and the second grating section 122, the sensing element in the housing 11 includes at least one first sensing element 131 for driving the first grating section 121 to change along a first direction, and at least one second sensing element 132 for driving the second grating section 122 to change along a second direction. The first direction and the second direction are perpendicular, for example, as... Figure 3 In the diagram, the first direction is the left-right direction, and the second direction is the direction perpendicular to the plane of the paper. When used in wind turbine blades, the back of the housing 11 is connected and installed to the blade. The first direction refers to the oscillation direction, that is, the vibration of the blade in the plane of rotation, perpendicular to the Y-axis direction on the side; the second direction is the control direction, that is, the vibration of the blade in the direction perpendicular to the plane of rotation, perpendicular to the Z-axis direction on the mounting plane.

[0031] In principle, the structures of the first sensitive element 131 and the second sensitive element 132 are not limited and can adopt existing technologies such as mass-spring systems and cantilever beam structures. For example, both the first sensitive element 131 and the second sensitive element 132 can adopt cantilever beam structures, or both can adopt mass-spring systems, or one can adopt a cantilever beam structure and the other adopts a mass-spring system. Considering the advantages of sensitivity, reliability, multi-axis detection, and miniaturization, in some embodiments, both the first sensitive element 131 and the second sensitive element 132 adopt cantilever beam structures.

[0032] In some implementations, a cantilever beam structure is used as the second sensing element 132, i.e. Figure 4 , 5 As shown in Figure 6, the cantilever beam structure includes a mounting base 133a, a cantilever beam 133b, and an inertial mass block 133c connected in sequence; Figure 3 As shown, the mounting base 133a is used to connect to the back of the housing 11, and the inertial mass block 133c is suspended inside the housing 11. The direction from the mounting base 133a to the inertial mass block 13c, or in other words, the length direction of the cantilever beam 133b, is perpendicular to both the first and second directions, i.e., according to... Figure 3 In the direction of the cantilever beam 133b, the length direction is parallel to the vertical direction; the two ends of the second grating part 122 in the length direction are connected to the mounting base 133a and the inertial mass block 133c respectively, and the body of the second grating part 122 does not contact the cantilever beam 133b, and the second grating part 122 has a certain pre-stretch to facilitate the quantization of the positive and negative acceleration signals into the stretching and compression of the grating. To facilitate the installation of the second grating part 122, the mounting base 133a and the inertial mass block 133c are respectively provided with grooves 133d for the second grating part 122 to be inserted into, so as to fix the second grating part 122. Adhesive can be applied to the grooves 133d to improve the fixing effect of the second grating part 122. In some embodiments, such as... Figure 5 , 6 As shown, at least two large circular grooves are provided between the grooves 133d to serve as glue fixing grooves. Glue is applied to these grooves to increase the adhesion effect on the second grating part 12, reduce the creep phenomenon of the optical fiber, and extend the service life of the sensor.

[0033] In this cantilever beam structure design, the inertial mass block 133c moves along the second direction, i.e. Figure 3 The vibration originates in a direction perpendicular to the paper plane, causing a change in the stretch of the second grating section 122, which in turn changes the reflected wavelength. By processing the center wavelength, the external acceleration signal can be calculated. In order to control the inertial mass block 133c to sense the vibration in the second direction, the dimension of the cantilever beam 133b along the second direction is smaller than its dimension along the first direction.

[0034] In some implementations, to avoid excessive vibration distance of the inertial mass block 133c along the second direction, such as Figure 3 As shown, the housing 11 is also provided with a limiting element, which includes at least one second limiting member 142 for limiting the movement distance of the second sensitive element 132 in the second direction. In the embodiment using a cantilever beam structure, the second limiting member 142 is U-shaped and includes a fixing plate, a connecting plate, and a limiting plate in sequence. The fixing plate is connected to the back of the housing 11, and the distance from the fixing plate to the limiting plate is parallel to the second direction. The inertial mass block 133c is inserted into the second limiting member 142, and its vibration distance is limited by the fixing plate and the limiting plate, protecting the acceleration sensitive element from damage in a large vibration environment.

[0035] The mounting method of the first grating portion 121 and the first sensitive element 131 is the same as that of the second grating portion 122 and the second sensitive element 132. In some embodiments, the first sensitive element 132 also adopts the same method. Figure 4 , 5 The cantilever beam structure shown in Figure 6 is basically the same as the cantilever beam structure of the second sensitive element 132 mentioned above, except that in this cantilever beam structure, the mounting base 133a is connected to the side of the housing 11, and the inertial mass block 133c is along the first direction, i.e. Figure 3 The cantilever beam 133b vibrates in the left-right direction, and its dimension along the first direction is smaller than its dimension along the second direction. Similarly, in some embodiments, the limiting element includes at least one first limiting member 141 for limiting the movement distance of the first sensitive element 131 in the first direction. The first limiting member 141 has a structure that is basically the same as the second limiting member 142 described above, except that in the first limiting member 141, the fixing plate is connected to the side of the housing 11, and the distance from the fixing plate to the limiting plate is parallel to the first direction.

[0036] In some embodiments, the thickness required for the housing 11 can be further reduced by adjusting the fiber Bragg grating coiling method to control the first grating section 121 and the second grating section 122 to be arranged in parallel on the same plane.

[0037] After the fiber optic grating and sensing element are installed in the housing 11, in some embodiments, the housing is filled with a damping fluid, such as silicone oil, to reduce measurement noise and abnormal vibration of the sensing element, thereby improving the accuracy of acceleration measurement. To prevent leakage of the damping fluid, the housing 11 has a through-hole for the pigtail 123 to pass through and a sealing ring inside the reinforcing cylinder.

[0038] In addition, since the measurement of wind turbine blades requires simultaneous monitoring of blade temperature to determine whether blade icing has occurred, a fiber optic temperature sensor 2 is fused in series after the accelerometer 1. This temperature sensor adopts a square structure package, which is convenient for attaching to the inner wall of the blade.

[0039] The specific embodiments described herein are merely illustrative examples illustrating the spirit of this utility model. Those skilled in the art to which this utility model pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of this utility model or exceeding the scope defined by the appended claims.

Claims

1. A fiber optic accelerometer for wind turbines, comprising an accelerometer (1) and a pigtail (3), wherein the accelerometer (1) comprises a housing (11), and a fiber optic grating and a sensing element disposed within the housing (11); Its features are: The fiber grating includes at least one first grating section (121), at least one second grating section (122), and a pigtail section (123). The first grating section (121), the second grating section (122), and the pigtail section (123) are connected in series. The pigtail section (123) passes through the housing (11) and is connected to the pigtail (3). The sensitive element includes at least one first sensitive element (131) for driving the first grating portion (121) to change along a first direction, and at least one second sensitive element (132) for driving the second grating portion (122) to change along a second direction. The first direction and the second direction are perpendicular.

2. The fiber optic accelerometer for wind turbines according to claim 1, characterized in that: Both the first sensing element (131) and the second sensing element (132) are cantilever beam structures. The cantilever beam structure includes a mounting base (133a), a cantilever beam (133b), and an inertial mass block (133c) connected in sequence. The mounting base (133a) is connected to the housing (11), and the inertial mass block (133c) is suspended inside the housing (11). The inertial mass block (133c) of the first sensitive element (131) senses vibration in the first direction, and the inertial mass block (133c) of the second sensitive element (132) senses vibration in the second direction. The two ends of the first grating part (121) or the second grating part (122) are respectively connected to the mounting base (133a) and the inertial mass block (133c), and the body of the first grating part (121) or the second grating part (122) does not contact the cantilever beam (133b).

3. The fiber optic accelerometer for wind turbines according to claim 2, characterized in that: The mounting base (133a) and the inertial mass block (133c) are respectively provided with grooves (133d) into which the first grating part (121) or the second grating part (122) can be inserted.

4. The fiber optic accelerometer for wind turbines according to claim 3, characterized in that: The groove (133d) is provided with an adhesive fixing groove.

5. The fiber optic accelerometer for wind turbines according to claim 1, characterized in that: The housing (11) is further provided with limiting elements, including at least one first limiting member (141) for limiting the movement distance of the first sensitive element (131) in the first direction, and at least one second limiting member (142) for limiting the movement distance of the second sensitive element (132) in the second direction.

6. The fiber optic accelerometer for wind turbines according to claim 1, characterized in that: The housing (11) includes a main body (111) with a accommodating cavity for housing the fiber optic grating and the sensitive element, and a plurality of fixing ears (112) disposed on the main body (111), the plurality of fixing ears (112) being uniformly arranged in a ring around the center of the main body (111).

7. The fiber optic accelerometer for wind turbines according to claim 1, characterized in that: The housing (11) is filled with damping fluid.

8. The fiber optic accelerometer for wind turbines according to claim 1, characterized in that: A fiber optic temperature sensor (2) is provided between the accelerometer (1) and the pigtail (3).

Images