JP2018136324A - Method for monitoring deformation of rotary element via monitoring device using optical fiber and wind force turbine having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for monitoring the change with time of a part exposed to rotational motions, and more specifically, for monitoring the deformation to which the surface of the region around the rotational part will be possibly exposed to.SOLUTION: The method includes the steps of: discharging an optical signal at a first end part of an optical fiber (step 71); measuring the characteristics of an optical signal received at a second end part of the optical fiber on the condition that at least one of the sections of the optical fiber extends between two positions of the surface of a part which is exposed to rotational motions (step 72); and comparing the characteristics of the optical signal and a reference signal on the condition that the characteristics change as the function of the length of the optical fiber between the ends of the optical fiber (step 73).SELECTED DRAWING: Figure 7

Description

  The present invention is in the field of monitoring aging of parts exposed to rotational motion. It particularly relates to monitoring the rotating elements of a wind turbine. More specifically, the present invention also relates to a method for monitoring the deformation of the surface of a part capable of undergoing rotational movement using a measuring device comprising an optical fiber that functions as a sensor.

  It is known to monitor static civil structures, such as buildings, tunnels or bridges, by determining the overall deformation, i.e. the deformation between at least two relatively distant positions of the structure . This is made possible in particular by the installation of an optical fiber extending between two positions of the structure and by analyzing the changes in the optical signal transmitted through this optical fiber. For example, EP 0649000 A1 describes a system for building monitoring that includes two support plates and optical fibers secured to each of these support plates and extending between them to form an arc. ing. By measuring the amplitude of the optical signal passing through the optical fiber, it is possible to determine the change in arc bending and the relative displacement of the two support plates.

  In the machine, some parts, especially moving parts, are at risk of breakage. However, in most cases, it is not possible to equip these parts with optical fibers that are properly positioned against damage that can take various forms. For example, wind turbine rotor blade deformation cannot be monitored by installing sensors on the rotor blades. The same is true for propellers, pistons, and more generally any moving parts. Furthermore, even if the sensor can be installed on the part to be monitored, the movement of this part presents some difficulties. First, sensor measurements can be hindered by inertia or centrifugal forces, or where applicable, by gravity, which varies as a function of the angular position of the part with the sensor. Second, the installation of sensors on rotating parts introduces asymmetries that can accelerate aging of the part itself or other parts of the machine, such as mechanical bearings. Finally, transmission of measurement results via an electrical conductor to an external device, for example the monitoring station, is not possible. This problem of transmission of measurement results becomes even more difficult when a large number of sensors are required to monitor the state of the part.

The object of the present invention is in particular the above mentioned by providing a deformation monitoring method which has the least possible influence on the operation and aging of this rotating element and which is not itself affected by the rotational movement. Overcoming all or part of the drawbacks. To this end, the present invention is based on the property that a moving part where a defect, for example a crack has started, propagates anomaly cyclique de contrainte and deformation in the structure. In practice, any crack is preceded by a stress non-uniformity in the part or by a material non-uniformity. This non-uniformity is linked to the deformation of the part. If the part moves during rotation, this non-homogeneity of deformation inevitably results in inhomogeneities in the generated and distributed dynamic stresses throughout the part. In particular, the part experiences a local cycle de compression-depression while stress is distributed differently over time. The periodic deformation of the part was selected as a strategic site for both to make the sensor relatively easy to install and for the capacity of this site to undergo stress changes in failure events It can be detected at the site of the structure. Thus, in the case of wind turbine rotor blades, a single sensor located all or part of the circumference of the rotor blade base is received both locally and at any other location of the rotor blade. Will respond to any damage. More specifically, an object of the present invention is a method for monitoring deformation that may occur on the surface of a portion that can undergo rotational motion, the method comprising:
Emitting an optical signal at the first end of the optical fiber, wherein at least one of the sections of the optical fiber extends between two positions on the surface of the part;
Measuring the characteristic of the optical signal received at the second end of the optical fiber, wherein the characteristic is evoluant as a function of the length of the optical fiber between the ends of the optical fiber; Comparing the characteristics of the optical signal with the reference signal,
It is characterized by including.

  The section of the optical fiber preferably follows the convexity of the surface of the part and allows it to be maintained in contact with the part over its entire length.

  The part is, for example, a wind turbine or a rotating element of a turbine. It can in particular be a ring of mechanical bearings.

According to a particular embodiment, a plurality of optical fibers are used, each optical fiber including a section that extends between two locations on the surface of the part. In this embodiment, for each optical fiber:
An optical signal is emitted at the first end,
The characteristics of the optical signal received at the second end are measured, and the characteristics of the optical signal are compared with a reference signal.

  The optical signal is preferably emitted simultaneously in each optical fiber, making it possible to support the result.

  In the first embodiment, two of the optical fibers are used, and the extending portion of the first optical fiber is arranged in axial symmetry with respect to the extending portion of the second optical fiber, and the axis of symmetry of the axis is It is the axis of rotation of the part.

  In a second embodiment, the surface is the surface of a rotating surface and the axis of rotation of the rotating surface is integrated with the axis of rotational movement of the part. The stretched portion of the optical fiber can then be angled along the axis of rotation to cover the outer periphery of the plane of rotation.

  The method also includes a transmission step (L'etape de transmission) of each measured characteristic, or of each comparison result of the measured characteristic and a reference signal, or part of these elements, by means of a radio link. Is also contained. In particular, in order to limit the electricity consumption of the radio link means, the transmission process can only be carried out when there is a malfunction. In fact, for the rotational movement of the part, these means are supplied by a battery mounted on the part. By limiting power consumption, the battery life can be extended. It is also possible to charge the battery by providing a generator driven by the movement of the part.

  According to a particular embodiment, the emission, measurement and comparison steps are carried out continuously over a determined period of time, enabling the monitoring of part deformation with respect to at least one complete rotation of the part.

The subject of the invention is also a wind turbine comprising a part capable of undergoing rotational movement and a device for monitoring deformation of said part, said monitoring device comprising:
An optical fiber in which at least one of the sections extends between two positions on the surface of said part;
A light source capable of emitting an optical signal at the first end of the optical fiber;
A detector capable of measuring a characteristic of the optical signal received at the second end of the optical fiber, wherein the characteristic varies as a function of the length of the optical fiber between the ends of the optical fiber; Shall be
A processing module capable of comparing the characteristics of the optical signal and the reference signal.

The invention will be better understood and other advantages will become apparent when reading the following description with reference to the accompanying drawings.
FIG. 1 schematically shows an example of a wind turbine used as a generator, the part of the wind turbine being monitored by the method according to the invention.
2 and 3 show an example of a ball bearing in which an installable deformation monitoring device can implement the method according to the invention.
4, 5, and 6 show different examples of monitoring device implementations on the ball bearings in FIGS.
FIG. 7 shows an example of the steps of the method for monitoring a rotating element according to the invention.
Examples of optical signals utilized by the monitoring device are shown in two graphs.

The present invention is based on a monitoring device that utilizes the propagation characteristics of an optical signal in an optical fiber that is firmly fixed at least two points to the part to be monitored. In practice, it is well known that the extension of an optical fiber in the longitudinal direction is accompanied by a lateral contraction that affects the attenuation effect of the amplitude of the optical signal passing through the optical fiber. Woven or twisted optical fibers are also well known, and their length changes also have the effect of changing the amplitude of the received signal after transmission through the optical fiber. Indicated by changes in flexion. Thus, measuring the amplitude of the optical signal very accurately determines the change in length experienced by the portion to be monitored between the two points where the optical fiber is fixed by comparing it to the reference amplitude. Make it possible. Patent application EP 0 264 622 A1 describes an example of the monitoring device. The apparatus includes an optical fiber and a measuring device capable of emitting an optical signal at one end of the optical fiber and measuring the amplitude of the received optical signal at the other end of the optical fiber.

FIG. 1 is a diagram schematically illustrating an example of a wind turbine used as a generator. The wind turbine 10 includes a nacelle 11 supported by a tower 12, a hub 13 pivotally connected to the nacelle 11 along a substantially horizontal axis X, and a rotor blade 14 supported by the hub 13. The nacelle 11 is pivotally connected to the tower 12 along a substantially vertical axis Y, allowing an orientation of the axis X in a direction parallel to the wind direction. In addition, each rotor blade is pivotally connected to the hub 13 along an axis Z ₁ , Z ₂ , or Z ₃ to allow orientation of each rotor blade as a function of wind speed. The axis Z ₁ , Z ₂ , or Z ₃ is perpendicular to the axis X and assembles at the position of the axis X. Preferably they are distributed around the axis X uniformly, i.e. at an angle of 120 degrees between them. Normally, the nacelle 11 contains an alternating current power source (not shown), and its shaft is rotationally driven directly or indirectly by the hub 13. The nacelle 11 can also contain drive means (not shown) that can drive the rotation of the rotor blade 14 relative to the hub 13 along the respective axis Z ₁ , Z ₂ , or Z ₃ .

2 and 3 show examples of ball bearings on which a deformation monitoring device can be installed. FIG. 2 shows a cross-sectional view of the ball bearing, and FIG. 3 shows a partial cross-sectional view of the part of the bearing. Ball bearing 20 provides a pivotable connection between hub 13 and one of rotor blades 14. It will be described as an example pivotable connection along the axis Z _1. The bearing 20 includes an outer ring 21, a first row of balls 22, a second row of balls 23, and an inner ring 24. The outer diameter of the bearing 20 is, for example, on the order of 2 meters in diameter. In the embodiment, the hub 13 is firmly fixed to the inner ring 24, and the rotor blade 14 is firmly fixed to the outer ring 21. In this example, the hub 13 is fixed to the inner ring 24 by a set of fixing elements that are unevenly distributed on the outer periphery of the inner ring 24. Each fixing element comprises, for example, two studs and two nuts. Next, the inner ring 24 is provided with a set of mounting holes 241 made parallel to the axis Z ₁ ; Is provided. Each stud passes through the mounting hole 241 of the inner ring 24 and the mounting hole of the hub 13. A nut is screwed into each end of the stud to secure the hub 13 to the inner ring 24. Similarly, the fixing of the rotor blade 14 to the outer ring 21 can be performed by a stud and a nut. Next, the outer ring 21, for example parallel to the axis _{Z 1,} can contain mounting holes 211. Of course, any other suitable securing means can be used to secure the rotor blade 14 to the outer ring 21 and the hub 13 to the inner ring 24. Bearing 20 is, for example, angular contact ball bearings, axial stress along axis Z _1, in particular to resist gravity and centrifugal force the rotor blades 14 are exposed. The bearing 20 shown in FIGS. 2 and 3 also includes a couronne dentee 212 formed on the outer peripheral surface 213 of the outer ring 21.
The saw bit 212 can engage a pinion (not shown) that is driven to orient the rotor blade 14 as a function of wind speed, for example.

  For the purpose of monitoring the occurrence of deformation of the outer circumferential surface 213 of the outer ring 21, a deformation monitoring device 30 can be installed there. Of course, it should be noted that the monitoring device 30 can also detect deformation caused by damage received by an arbitrary portion connected to the outer ring 21 instead of the outer ring 21 alone. The monitoring device 30 includes an optical fiber 31, a light source 32 that can emit an optical signal at the first end of the optical fiber 31, and a detection that can measure the characteristics of the optical signal received at the second end of the optical fiber 31. Container 33. The measured characteristic varies between the ends of the optical fiber 31 as a function of the length of the optical fiber 31. This can be, for example, the amplitude of the optical signal or the duration of travel of the optical signal between both ends of the optical fiber 31. It should be noted that the light source 32 and the detector 33 can be grouped together in the same module. Also, one of the physical ends of the optical fiber 31 can be coupled to a reflector capable of reflecting an optical signal. The second physical end of the optical fiber 31 is then used for both emitting and receiving optical signals. In order to be able to monitor the deformation of the outer peripheral surface 213, the optical fiber 31 must contain at least one section extending between two points of the outer peripheral surface 213. Usually, the section follows the outer peripheral surface 213. According to a preferred embodiment, the optical fiber 31 is installed so that the section is exposed to tension de precontrainte. Thus, even when the deformation of the outer peripheral surface 213 includes two points where the optical fiber 31 is fixed close to each other, the section undergoes a change in length (in this case, contraction). According to a particular embodiment, the optical fiber 31 is prestressed between its entire length, ie the end connected to the light source 32 and the end connected to the detector 33.

  FIG. 4 shows a first example of implementation of the deformation monitoring device 30 on the bearing 20. In this example, the light source 32 and the detector 33 are contained in a single module, and the optical fiber 31 is stretched over the entire circumference of the outer peripheral surface 213. Preferably, the optical fiber 31 is prestressed over its entire length.

  FIG. 5 shows a second example of installation of the deformation monitoring device 50 on the bearing 20. In this example, the apparatus 50 comprises two light sources 32A and 32B, two detectors 33A and 33B, and two optical fibers 31A and 31B. The optical fiber 31A extends between the light source 32A and the detector 33A over the first half of the periphery of the outer peripheral surface 213, and the optical fiber 31B extends between the light source 32B and the detector 33B around the outer peripheral surface 213. It extends over the second half. Each optical fiber 31A and 31B is preferably pre-stressed over its entire length.

  FIG. 6 shows a third example of implementation of the deformation monitoring device 60 on the bearing 20. In this example, the device 60 comprises three light sources 32A, 32B and 32C, three detectors 33A, 33B and 33C, and three optical fibers 31A, 31B and 31C. Optical fiber 31A extends between light source 32A and detector 33A; optical fiber 31B extends between light source 32B and detector 33B; optical fiber 31C includes light source 32C and detector 33C. It stretches between. The light sources 32A, 32B, and 32C and the detectors 33A, 33B, and 33C are disposed on the outer peripheral surface 213 so that the optical fibers 31A, 31B, and 31C cover the entire periphery of the outer peripheral surface 213. Advantageously, each optical fiber covers substantially one third of the circumference of the outer peripheral surface 213. Each optical fiber 31 </ b> A, 31 </ b> B, and 31 </ b> C can be concentrated with respect to the rotor blade 14. More generally, the deformation monitoring device can include any number of assemblies, each comprising an optical fiber, a light source, and a detector. The advantage of being able to use multiple assemblies is that it allows for more local monitoring of deformation. Also, the optical fiber can overlap at least partially around the surface to be monitored.

FIG. 7 is a diagram illustrating an example of steps of the deformation monitoring method according to the present invention. This method will now be described with reference to an example implementation of the monitoring device of FIG. In the first step 71, the light source 32 emits an optical signal, for example a pulse, at the first end of the optical fiber 31. In the second step 72, the detector 33 receives the optical signal at the other end of the optical fiber 31, and measures the characteristics of this optical signal. As mentioned above, the characteristic can be the amplitude of the optical signal or the duration of transmission of the optical signal between the light source 32 and the detector 33. The optical signal can be single frequency, can be spread over a frequency band, or can be composed of multiple single frequency signals. The optical fiber 31 can be a single mode or a multimode fiber. Thus, the characteristic measured by the detector 33 can actually be the result of a combination of characteristics. In step 73, the characteristics of the optical signal are compared with the reference signal. The comparison is performed by a processing module that is or is not incorporated in the detector 33. The reference signal may have an amplitude value, for example during a phase d'initialisation if the part to be monitored is considered present aucun defaut and / or said part It can be the amplitude value of the optical signal measured during the phase de repos when not subjected to any rotational movement. The reference signal can be, for example, the duration of the reference measured during the initialization and / or stop phase. Also, the optical signal emitted by the light source 32 is not necessarily a pulse and can be a continuous signal if the reference signal is also continuous. The duration of the optical signal is determined, for example, such that during this duration the part to be monitored makes a complete rotation. Fatigue phenomena due to the asymmetry of the part to be monitored can therefore be observed due to the discontinuity of the optical signal received at the detector 33. The optical signal can be emitted or received at a predetermined frequency or upon operator request. The monitoring frequency depends in particular on the importance of the monitored part and / or on previous measurements made on the monitored part or other parts mechanically connected to the monitored part. If several optical fibers are used to monitor the deformation of the same part, different optical signals can be emitted independently of one another or synchronously. Signal synchronization has the advantage of allowing correlation of measurement results. The monitoring method according to the present invention may also include a step 74 of transmitting the result of each comparison between the optical signal and the reference signal to an external device such as a monitoring station. Alternatively, the data transmitted during step 74 could be an optical signal received at detector 33 where the comparison is being made by an external device. According to a particular embodiment, the wind turbine contains a central unit that collects data originating from the detector 33 or from the processing module performing the comparison, preferably via a wireless link. Preferably, this central unit collects data originating from all detectors of the wind turbine and / or from all processing modules. A common monitoring station for the entire wind farm can collect all of the data collected by different central units via wired or wireless links.

  Due to the movement received by the part to be monitored, the monitoring device 30 is preferably supplied by a battery, for example a lithium battery. Furthermore, data transmission is preferably performed by wireless link means. In order to limit the power consumption of the monitoring device 30 and increase the life of the battery, the data transmission can be performed relatively infrequently, for example once a day. This frequency can be smaller than the measurement frequency, ie the frequency at which the optical signal is emitted. According to an advantageous embodiment, data is transmitted only if a malfunction is found.

  According to a particular embodiment, the monitoring device 30 utilizes the movement of the monitored part to increase its autonomy. In particular, the monitoring device 30 can contain a generator that is driven by the movement of the part and makes it possible to charge the battery.

  FIG. 8 shows an example of an optical signal used by the monitoring device 30 in two graphs. The first graph 81 shows an example of the reference optical signal, and the second graph 82 shows an example of the optical signal received by the detector 33 when a malfunction occurs in a part of the wind turbine. is there. In each graph, the amplitude A of the signal is plotted as a function of time over a duration substantially corresponding to two revolutions of the hub 13 of the wind turbine. As shown in FIG. 81, the amplitude of the reference signal is substantially constant over time. The optical signal received by the detector 33 in the absence of defects will be the same or similar. In practice, in the normal situation, i.e. no wear or completely regular wear, the measurement signal does not show any discontinuities during the complete rotation of the rotor blades. On the other hand, the graph 82 shows a failure in the amplitude of the optical signal, a sign of irregularity, a change in the stress experienced by the part of the normal cycle, and thus in one of the parts monitored or connected to it. The start of the wave. It should be noted that monitoring stress changes means monitoring the effects of aging of the primary effect of the part, as opposed to monitoring cracks, which are tertiary effects. In this way, maintenance of wind turbines can be managed in a more logical manner by allowing maintenance to be planned in advance by stress monitoring.

  The monitoring method according to the invention has been described with reference to the bearing between the hub and rotor blades of a wind turbine. Of course, for other bearings of the wind turbine, for example, for bearings between the hub and nacelle frame of the wind turbine, and for other parts that are subject to rotational movement, such as turbine wheels or Pelton wheels. It would be possible to apply More generally, this method is applicable to any rotating element having a surface where it is desirable to monitor deformation. This surface can be an outer peripheral surface. In the case of points, it can be a rotating surface whose axis of rotation is integrated with the axis of rotation of the rotating element. Preferably, the section of the optical fiber that extends between the two points of the rotating element follows the convexity of its surface.

The invention will be better understood and other advantages will become apparent when reading the following description with reference to the accompanying drawings.
It is schematically shown to view an example of a wind turbine to be used as a generator, part of the wind turbine is monitored by the process according to the invention. FIG. 3 shows an example of a ball bearing in which an installable deformation monitoring device can implement the method according to the invention. FIG. 3 shows an example of a ball bearing in which an installable deformation monitoring device can implement the method according to the invention. Is a diagram illustrating different examples of embodiment of the monitoring device on the ball bearing in FIG. 2 and 3. Is a diagram illustrating different examples of embodiment of the monitoring device on the ball bearing in FIG. 2 and 3. Is a diagram illustrating different examples of embodiment of the monitoring device on the ball bearing in FIG. 2 and 3. It is a figure which shows the example of the process of the monitoring method of the rotation element by this invention. It is a figure which shows the example of the optical signal utilized by the monitoring apparatus in two graphs.

Claims (13)

A method for monitoring deformations that may occur on a surface (213) of a part (21) capable of undergoing rotational movement, said method comprising:
Emitting an optical signal at a first end of the optical fiber (31), wherein at least one of the sections of the optical fiber is at two positions on the surface (213) of the part (21); It shall be stretched between
Measuring a characteristic of the optical signal received at the second end of the optical fiber (31), wherein the characteristic is a function of the length of the optical fiber between the ends of the optical fiber; And (73) comparing the characteristic of the optical signal with a reference signal;
The monitoring method comprising the steps of:   The method according to claim 1, wherein the section of the optical fiber (31) follows a convexity of the surface (213) of the portion (21).   The method according to claim 1 or 2, wherein the portion (21) is a rotating element of a wind turbine (10).   The method according to claim 1 or 2, wherein the portion (21) is a rotating element of a turbine.   The method according to claim 1, wherein the part is a ring (21) of a mechanical bearing (20). A plurality of optical fibers (31A, 31B, 31C) are used, each optical fiber including a section extending between two locations on the surface (213) of the portion (21), each For optical fiber:
An optical signal is emitted at the first end,
The characteristics of the optical signal received at the second end are measured, and the characteristics of the optical signal are compared with a reference signal,
The method according to any one of claims 1 to 5.   The method according to claim 6, wherein the optical signals are emitted simultaneously in each optical fiber (31A, 31B, 31C). Two optical fibers (31A, 31B) are used, and the extending portion of the first optical fiber (31A) is arranged in axial symmetry with respect to the extending portion of the second optical fiber (31B), and the axially symmetric symmetry. The method according to claim 6 or 7, wherein the axis (Z ₁ ) is the axis of rotational movement of the part (21). The surface (213) is the surface of the rotating surface in which the axis of rotation (Z ₁ ) is integrated with the axis of rotational movement of the portion (21), and the extending portions of the optical fibers (31A, 31B, 31C) The method according to claim 6 or 7, wherein the angle is distributed along the rotation axis (Z ₁ ) so as to cover the outer periphery of the rotation surface (213).   10. A transmission step (74) by means of radio link means of each measured characteristic or of each comparison result of the measured characteristic and a reference signal, or a part of these elements, also comprising a step (74). The method as described in any one of.   The method according to claim 10, wherein the transmission step (74) is performed only if a malfunction occurs.   The steps of releasing (71), measuring (72) and comparing (73) are carried out continuously over a determined period of time, the deformation of said part (21) with respect to at least one complete rotation of said part (21). 12. The method according to any one of claims 1 to 11, which enables monitoring of A wind turbine comprising a part (21) capable of undergoing rotational movement and a device (30) for monitoring deformation of said part, said monitoring device comprising:
An optical fiber (31) in which at least one of the sections extends between two positions on the surface (213) of said part (21);
A light source (32) capable of emitting an optical signal at the first end of the optical fiber (31);
A detector (33) capable of measuring a characteristic of the optical signal received at the second end of the optical fiber (31), wherein the characteristic is the optical fiber between the ends of the optical fiber; Shall vary as a function of length,
The wind turbine comprising a processing module capable of comparing characteristics of the optical signal and a reference signal.

Images