WO2022123182A1

WO2022123182A1 - Device for measuring mechanical movement of a part

Info

Publication number: WO2022123182A1
Application number: PCT/FR2021/052250
Authority: WO
Inventors: Nassim SALHI; Minh Chau Phan Huy
Original assignee: Safran
Priority date: 2020-12-10
Filing date: 2021-12-09
Publication date: 2022-06-16
Also published as: FR3117591A1; FR3117591B1

Abstract

The invention relates to a device (10) for measuring mechnical movement of at least one part (50), comprising: - at least one fibre optic sensor (20) comprising at least a first fibre Bragg grating (30a) and at least a second fibre Bragg grating (30b), - a resiliently deformable member (40) provided with the sensor (20), and - a movable member (60) rigidly connected to the member (40) and comprising a first longitudinal end (60a) of the movable member configured to be attached to the part (50). In addition, the fibre Bragg grating (30a) extends between the movable member (60) and a first end (42) of the member (40) and the second fibre Bragg grating extends between the movable member (60) and a second end (44) of the member (40). The device (10) further comprises a fixed carrier (70) to which the first end (42) and the second end (44) of the member (40) are attached.

Description

DESCRIPTION

TITLE: DEVICE FOR MEASUREMENT OF MECHANICAL DISPLACEMENT OF A PART

Technical field of the invention

The present invention relates to a device for measuring the mechanical displacement of a part, using several Bragg gratings. This type of mechanical displacement measuring device is, in particular but not exclusively, suitable for on-board equipment, used in an environment under severe conditions, in which the mechanical displacement measuring device is subjected to strong variations in ambient temperature and electromagnetic disturbances.

The mechanical displacement measuring device finds applications in various fields, such as civil engineering, geotechnics, aeronautics, etc.

Technical background

The state of the art includes, in particular, documents EP-A2-0867688, WO-A1 -2009/073913, FR-A1 -2983954 and JP-A-2017198628.

A mechanical displacement measuring device, also called an extensometer in the technical field, is commonly used in the industrial sectors to characterize and guarantee the state of structural integrity and operation of a part in use, in particular without the degrade.

The extensometer is therefore an instrument used to measure a displacement, or deformation, in a measurement range that can range from a few millimeters to several tens of centimeters. It can be used on a part subjected to traction, compression or torsion.

The extensometer comprises one or more Bragg gratings integrated in a "heart" of a fiber optic sensor, also designated by FBG for "Fiber Bragg Grating" in English. The fiber optic sensor therefore comprises two layers. In the center of the fiber optic sensor, is arranged the core having a high refractive index and a very small diameter and allows the transport of light. Around the core is arranged a sheath having a lower refractive index preventing light from exiting the core.

The Bragg grating is able to measure the modification of the light propagating in the fiber optic sensor consisting of a periodic modulation of the refractive index of the heart creating a resonant structure.

It is known from the state of the art, an extensometer capable of measuring mechanical displacements of a moving part via the fiber optic sensor independently of the surrounding temperature.

FIG. 1 presents a schematic view in perspective of a device for measuring the mechanical displacement of a part 5 whose mechanical displacement is to be measured according to the state of the art on which an extensometer 1 comprises an optical fiber sensor 2 integrating two Bragg gratings 3a and 3b positioned symmetrically on a lower face 4a and an upper face 4b of a flexible blade 4, generally designated by the term cantilever in English. The flexible blade 4 is connected to the part 5, so that any displacement of the part 5 is transmitted to the Bragg gratings 3a and 3b.

The Bragg gratings 3a and 3b are capable of measuring the modification of the light propagating in the optical fiber sensor 2. The displacement of the part 5 is determined by calculating the difference between the two measurements of the Bragg gratings 3a and 3b.

The use of the two Bragg gratings 3a and 3b thus positioned leads to a self-compensation of the effect of temperature, since the two Bragg gratings 3a and 3b have the same temperature sensitivity. Thus, the temperature surrounding part 5 will induce the same offset, or error, on the two Bragg gratings 3a and 3b.

Therefore, the calculation of the difference makes it possible to eliminate the contribution of the temperature and to keep only the contribution of the displacement of the part 5. However, such an extensometer may have drawbacks in terms of use and/or size in on-board equipment used in severe environments in which the fiber optic sensors are subjected to strong temperature variations and electromagnetic disturbances.

For example, a reliable, space-saving mechanical displacement measurement device may be required in the thrust reversers of an aircraft propulsion system. Such a mechanical displacement measuring device can be fixed to a control unit fitted to a structural casing of the thrust reverser to check the positions (closing, opening and during opening) of the thrust reverser flaps .

In such a context, it is interesting to propose a solution making it possible to overcome, at least in part, the drawbacks of the state of the art, in particular by optimizing the measurement of mechanical displacement of a part, in particular for a propulsion assembly. aircraft, by a mechanical displacement measuring device that is reliable and compatible with the space available in operation.

Summary of the invention

The present invention thus proposes a device for measuring the mechanical displacement of at least one part, in particular of an aircraft propulsion assembly, comprising:

- at least one optical fiber sensor comprising at least one first Bragg grating and at least one second Bragg grating,

- an elastically deformable member equipped with the fiber optic sensor, in particular extending along a longitudinal axis, and

- a movable member, in particular of elongated shape and in particular able to slide in translation along the longitudinal axis, integral with the elastically deformable member and comprising a first longitudinal end of the movable member configured to be fixed to the part.

According to the invention, the first Bragg grating extends between the movable member and a first end of the elastically deformable member and the second Bragg grating extends between the movable member and a second end of the elastically deformable member.

Moreover according to the invention, the device for measuring mechanical displacement further comprises a fixed support to which are fixed the first end and the second end of the elastically deformable member.

According to the invention, the fiber optic sensor is capable of measuring at least one mechanical displacement of the part. Thus, this solution achieves the above objective.

For this, the mechanical displacement measuring device according to the invention synergistically combines, on the one hand, at least one Bragg grating integrated directly between the movable member and each of the ends of the elastically deformable member, and on the other hand, to fix the ends of the elastically deformable member on a fixed support. Such a configuration allows the elastically deformable member to ensure the functions of a feedback element and of a deformable element, to allow transmission and measurement by the Bragg gratings of the deformations generated by the displacements of the part whose mechanical displacement is to be measured and/or controlled.

In particular, the movable member is able to move, in particular to cause the elastically deformable member to slide, in particular in translation along the longitudinal axis, when the part to be measured moves. This generates mechanical stresses on each of the ends of the elastically deformable member fixed to the fixed support. These stresses therefore cause deformation by compression of one of the ends of the elastically deformable member and deformation by traction of the other of the ends of the elastically deformable member. These deformations by compression and by tension are thus measured, respectively, by the first Bragg grating and the second Bragg grating positioned specifically on each of the ends of the elastically deformable member.

More particularly, the Bragg gratings are capable of measuring the modification of the light propagating in the optical fiber sensor. the calculation of the difference in measurements of the Bragg gratings makes it possible to determine the mechanical displacement of the part.

This differential measurement of the first Bragg grating and the second Bragg grating has the advantage of not requiring consideration of the contribution of the surrounding room temperature.

Such a configuration of the mechanical displacement measuring device according to the invention makes it possible to simplify and optimize the measurement of mechanical displacement of a part or of on-board equipment used in an environment under severe conditions in which the device mechanical displacement measuring device is subject to strong variations in ambient temperature and electromagnetic disturbances.

The invention therefore has the advantage of being based on a simple design, offering very high reliability and little disadvantage in terms of cost and size.

The mechanical displacement measuring device according to the invention may comprise one or more of the following characteristics, taken separately from each other or in combination with each other:

- the first Bragg grating is configured to measure a tensile deformation of the elastically deformable member and the second Bragg grating is configured to measure a compressive deformation of the elastically deformable member;

- the fixed support, in particular having a generally elongated shape along the longitudinal axis, comprises longitudinal ends provided respectively with a first transverse wall and a second transverse wall on which are fixed the first end and the second end of the elastically deformable organ;

- the movable member comprises a guide rod, in particular extending along the longitudinal axis, and a slider;

- the slider is fixed to an intermediate portion of the elastically deformable member;

- The movable member further comprises a guide roller extending in the elastically deformable member, in particular along the longitudinal axis; - the guide roller comprising a central opening able to allow the insertion of at least a part of the guide rod and at least one longitudinal groove of complementary shape with at least one junction member connecting the guide rod to the slider;

- the fixed support comprises guide members cooperating with complementary members of the slider, the guide members and/or the complementary members being, for example, chosen from at least rails, grooves, stops and/or bores;

- the elastically deformable member comprises an internal passage over its entire extent inside which the fiber optic sensor extends;

- the elastically deformable member the optical fiber sensor is fixed along an outer surface of the elastically deformable member;

- the elastically deformable member comprises a sheath, in particular of heat-shrinkable material, capable of wrapping and securing the optical fiber sensor to the elastically deformable member;

- the mechanical displacement measuring device further comprises a counter-reaction spring whose ends are connected, respectively, to the slider and to the fixed support; and

- the elastically deformable member is a helical spring formed by a tubular wire or by a solid wire.

The present invention also relates to a system for measuring mechanical displacements, in particular for an aircraft propulsion assembly, comprising at least one mechanical displacement measuring device according to the invention for measuring the mechanical displacements of a part of the assembly aircraft propellant.

The measurement system can also include a device for processing and analyzing data from the fiber optic sensor. Such a processing and analysis device, also referred to as an interrogator, makes it possible to emit a light wave in the optical fiber of the optical fiber sensor. By traversing the optical fiber, the wave is partly absorbed or diffused by the heart of the optical fiber. The part of the scattered wave is then analyzed by the interrogator. The present invention also relates to an aircraft propulsion assembly, comprising in particular a turbomachine and a nacelle forming an outer annular envelope of the turbomachine, and an aircraft comprising such a propulsion assembly.

The propulsion assembly comprises at least one part connected to a mechanical displacement measuring device according to the invention or to a measuring system according to the invention. The mechanical displacement measuring device or the measuring system can be fixed on a structural casing of the turbomachine and/or of the nacelle. The part to be measured can be a part of a thrust reverser, such as flaps.

Of course, the different characteristics, variants and/or embodiments of the invention can be associated with each other in various combinations insofar as they are not incompatible or exclusive of each other.

Brief description of figures

The invention will be better understood and other characteristics and advantages will become apparent on reading the following detailed description comprising embodiments given by way of illustration with reference to the appended figures, presented by way of non-limiting examples, which may be used to complete the understanding of the invention and the presentation of its realization and, where appropriate, contribute to its definition, on which:

[Fig.1] the figure is a schematic perspective view of a mechanical displacement measuring device according to the state of the art;

[Fig.2] Figure 2 is a schematic view in axial section of a first embodiment of a mechanical displacement measuring device according to the invention;

[Fig.3a] Figure 3a is a schematic view in axial section of a first variant of an elastically deformable member of the mechanical displacement measuring device of Figure 2;

[Fig.3b] Figure 3b is a schematic view in axial section of the elastically deformable member of Figure 3a comprising an optical fiber sensor; [Fig.4a] Figure 4a is, respectively, a partial view and an enlarged view in axial section of a second variant of an elastically deformable member of the mechanical displacement measuring device of Figure 2 comprising a fiber sensor optical;

[Fig.4b] Figure 4b is, respectively, a partial view and an enlarged view in axial section of the elastically deformable member of Figure 4a comprising a sheath;

[Fig.4c] Figure 4c is, respectively, a partial view and an enlarged view in axial section of the elastically deformable member of Figure 4b after retraction of the sheath;

[Fig.5a] Figure 5a is a schematic view in axial section of a measuring system comprising the mechanical displacement measuring device of Figure 2;

[Fig.5b] Figure 5b is a schematic view in axial section of a variant of a mobile member of the measuring system of Figure 5a;

[Fig.6a] Figure 6a is a schematic view in axial section of a second embodiment of the mechanical displacement measuring device according to the invention, in which the elastically deformable member is in the rest position;

[Fig.6b] Figure 6b is a schematic view in axial section of the mechanical displacement measuring device of Figure 6a, in which the elastically deformable member is compressed on one side;

[Fig.6c] Figure 6c is a schematic front view of a variant of the movable member of the mechanical displacement measuring device of Figures 6a and 6b;

[Fig.6d] Figure 6d is a schematic front view of a variant of a fixed support of the mechanical displacement measuring device of Figures 6a and 6b;

[Fig.7] Figure 7 is a schematic perspective view of a movable member of a third embodiment of the mechanical displacement measuring device according to the invention; [Fig.8a] Figure 8a is a schematic perspective view of a slider and a guide rod of the movable member of the third embodiment of the mechanical displacement measuring device according to Figure 7;

[Fig.8b] Figure 8b is a schematic front view of a variant of the movable member of Figure 8a;

[Fig.9a] Figure 9a is a schematic perspective view of a roller of the movable member of Figure 7;

[Fig.9b] Figure 9b is a schematic front view of the roller of Figure 9a

[Fig, 9c] Figure 9c is a schematic front view of a variant of the roller of Figures 9a and 9b;

[Fig.10] Figure 10 is a schematic perspective view of the third embodiment of the mechanical displacement measuring device comprising the movable member of Figure 7;

[Fig.11] Figure 11 is a schematic perspective view of a fixing cap of the mechanical displacement measuring device of Figure 10;

[Fig.12] Figure 12 is a schematic perspective view of a fourth embodiment of the mechanical displacement measuring device according to the invention;

[Fig.13a] Figure 13a is a schematic perspective view of a fifth embodiment of the mechanical displacement measuring device according to the invention;

[Fig.13b] Figure 13b is a schematic view of a feedback spring of Figure 13a.

Furthermore, it should be noted that, in the various figures, the structural and/or functional elements common to the various embodiments may be designated by identical references. Thus, unless otherwise stated, such elements have identical structural, dimensional and material properties. In addition, the various elements are not necessarily represented to scale in order to present a view making it easier to understand the invention.

Detailed description of the invention By convention, in the description below, the terms "longitudinal" and "axial" qualify the orientation of structural elements extending in the direction of a longitudinal axis, such as a longitudinal axis of a measurement of mechanical displacement, in particular an elastically deformable member. The terms “radial” or “vertical” qualify an orientation of structural elements extending in a direction perpendicular to the longitudinal axis. The terms "inner", "outer", "inner" and "outer" are used in reference to positioning relative to the longitudinal axis. Thus, a structural element extending along the longitudinal axis has an inner face facing the longitudinal axis and an outer surface, opposite the inner face.

Figure 1 has been described in the preamble of the description. It is a schematic perspective view of a device for measuring the mechanical displacement of a part 5 whose mechanical displacement is to be measured according to the state of the art.

Figures 2 to 13 show several embodiments of a mechanical displacement measuring device 10 according to the invention. The mechanical displacement measuring device 10 is used to measure and/or control a mechanical displacement of a part 50, visible in particular in FIG. 5a. The part 50 for which it is desired to measure and/or control a mechanical displacement can in particular be all or part of an aircraft propulsion assembly.

For this, the mechanical displacement measuring device 10 comprises an optical fiber sensor 20. More particularly, the mechanical displacement measuring device 10 comprises at least a first Bragg grating 30a and a second Bragg grating 30b. In addition, the mechanical displacement measuring device 10 may comprise an elastically deformable member 40, a movable member 60, in particular a movable member 60 of elongated shape, and/or a fixed support 70.

More specifically, FIGS. 2 to 5b illustrate a first embodiment of the mechanical displacement measuring device 10 according to the invention. According to the first embodiment of the mechanical displacement measuring device 10, the elastically deformable member 40 has a generally elongated shape extending along a longitudinal axis A.

Referring to Figures 2, 3a and 4c, the elastically deformable member 40 comprises a first end 42 and a second end 44, in particular a first end 42 and a second end 44 opposite each other. The elastically deformable member 40 also comprises an intermediate portion 46, or middle portion 46, connecting the first end 42 and the second end 44 to each other.

In the example presented, the first end 42, the second end 44 and the intermediate portion 46 are monobloos. Alternatively, the first end 42, the second end 44 and the intermediate portion 46 could be unitary and interconnected. The elastically deformable member 40 has an outer surface 47.

The elastically deformable member 40 is of a variable length and/or diameter depending on the dimensions of the part 50 to be measured and/or the environment in which the mechanical displacement measuring device 10 is used.

Advantageously, the elastically deformable member 40 is a helical spring 40 as illustrated without limitation in the figures. Coil spring 40 includes a plurality of coils. The turns of the helical spring 40, in the rest position, can be separated to allow deformations by compression and by extension, or traction, along the longitudinal axis A. In the rest position, the helical spring 40 comprises a distance (d) between two adjacent turns, as illustrated in Figures 3a and 4c.

Figures 3a and 3b illustrate a first variant of the elastically deformable member 40, in which the elastically deformable member 40 is a helical spring 40 comprising an internal passage 48 extending over its entire extent. In such a configuration, coil spring 40 is hollow. By way of example, the hollow coil spring 40 can be made by winding a hollow capillary or a tubular wire in several turns.

FIGS. 4a to 4c illustrate a second variant of the elastically deformable member 40 comprising a sheath 49. In particular, the sheath 49 is made of shrinkable material, advantageously made of heat-shrinkable material. In such a configuration, coil spring 40 may be non-hollow. By way of example, the non-hollow coil spring 40 can be made by winding a solid metal rod or a solid wire in several turns.

Referring to Figures 2, 3b, 4a to 4c, the elastically deformable member 40 is equipped with the fiber optic sensor 20.

According to the first variant of the elastically deformable member 40, the optical fiber sensor 20 is fixed inside the internal passage 48. With reference to FIG. 3b, the optical fiber sensor 20 comprising the first Bragg grating 30a and the second Bragg grating 30b is inserted into the internal passage 48 of the helical spring 40, formed for example by a capillary. The fiber optic sensor 20 comprising the first Bragg grating 30a and the second Bragg grating 30b is therefore wound in a spiral following the shape of the capillary forming the helical spring 40 directly integrating the fiber optic sensor 20.

By way of example, the hollow coil spring 40 incorporating the fiber optic sensor 20 is wound with a radius of curvature of approximately 15 mm. The radius of curvature can be variable depending on the dimensions and the type of optical fiber sensor 20 used.

According to the second variant of the elastically deformable member 40, the optical fiber sensor 20 is fixed along the outer surface 47 of the elastically deformable member 40. More particularly, the optical fiber sensor 20 is fixed along the external surface 47 of the elastically deformable member 40 via the sheath 49, in particular made of shrinkable material, advantageously of heat-shrinkable material. The sheath 49 made of shrinkable or heat-shrinkable material has the advantage of fixing the optical fiber sensor 20 to the elastically deformable member 40 by heating and/or of adapting to the deformations of the elastically deformable member 40 in operation.

Referring to Figure 4a, the fiber optic sensor 20 comprising the first Bragg grating 30a and the second Bragg grating 30b is fixed on the outer surface 47 of the coil spring 40, for example at several points 22, in order to maintain fixed the fiber optic sensor 20 on the coil spring 40. The fiber optic sensor 20 can be fixed, for example glued, progressively on the coils of the helical spring 40 when the latter is rigid. Alternatively, the fiber optic sensor 20 can be fixed, for example by glue, progressively on different points 22 of a straight zone of the unwound spring, or of the non-wound metal rod, when the spring is flexible.

Referring to Figure 4b, once the fiber optic sensor 20 is attached to the coil spring 40, the sheath 49 is threaded serpentine on the coil spring 40 comprising the fiber optic sensor 20, with or without adhesive. The sheath 49 has a diameter greater than the diameter of the coil spring 40 comprising the fiber optic sensor 20, before shrinking of the sheath 49.

Referring to Figure 4c, once the sheath 49 threaded on the coil spring 40 comprising the fiber optic sensor 20, the sheath 49 is retracted, for example using a heating element, also designated by the term hot gun in English. In this configuration, the diameter of the retracted sheath 49 is less than the diameter of the coil spring 40 comprising the fiber optic sensor 20.

The assembly formed by the elastically deformable member 40 and the optical fiber sensor 20 equipped with the first Bragg grating 30a and the second Bragg grating 30b is configured to be assembled on the fixed support 70. In the examples and in a manner not limiting, the fixed support 70 has an elongated shape, such as a cylinder of revolution, extending around the longitudinal axis A.

Referring to Figures 2, 5a and 5b, the fixed support 70 comprises a first transverse wall 72 and a second transverse wall 74 disposed at the longitudinal ends of the fixed support 70. The first end 42 and the second end 44 of the elastically deformable member 40 are fixed, respectively, to the first transverse wall 72 and to the second transverse wall 74.

In a complementary manner, the first transverse wall 72 and/or the second transverse wall 74 may respectively comprise a first orifice 720 and a second orifice 740. It is thus possible to pass elements of the mechanical displacement measuring device 10 to the interior of the fixed support 70. In the examples of FIGS. 2 and 5a, the first end 42 comprising the fiber optic sensor 20 is connected to the first transverse wall 72 through the first orifice 720. Preferably, the first orifice 720 has a diameter substantially similar to the diameter of the the first end 42 comprising the fiber optic sensor 20. The second end 44 comprising the fiber optic sensor 20 can be attached to the second transverse wall 74 by fixing means, such as clips not shown in the figures.

Referring to Figure 5a, the second orifice 740 is adapted to receive a first longitudinal end 60a of the movable member 60. Preferably, the second orifice 740 has a diameter substantially similar to the diameter of the first longitudinal end 60a. Thus configured, the movable member 60 has an elongated shape extending along the longitudinal axis A.

As shown in Figure 5a, the movable member 60 connects the elastically deformable member 40 and the part 50 to be measured.

Referring to Figures 2, 4c to 5b, the movable member 60 comprises the first longitudinal end 60a and a second longitudinal end 60b, in particular a first longitudinal end 60a and a second longitudinal end 60b opposite each other.

In the example shown, the first longitudinal end 60a and the second longitudinal end 60b are in one piece. Alternatively, the first longitudinal end 60a and the second longitudinal end 60b could be unitary and interconnected.

The second longitudinal end 60b can be fixed substantially on the intermediate portion 46 of the elastically deformable member 40. Thus arranged, the movable member 60 and the elastically deformable member 40 are integral, in particular in translation along the longitudinal axis HAS.

The first longitudinal end 60a is configured to be fixed to the part 50 to be measured, so that the optical fiber sensor 20 fitted to the elastically deformable member 40 is able to measure the mechanical displacements of the part 50. Advantageously, the movable member 60 comprises a slider 62 connected to a guide rod 64. The guide rod 64 may have an elongated shape along the longitudinal axis A.

The guide rod 64 extends longitudinally between the first longitudinal end 60a and the second longitudinal end 60b. The first longitudinal end 60a extends by passing through the second orifice 740 of the fixed support 70, between the part 50 and the second longitudinal end 60b connected to the elastically deformable member 40.

In the example of the figures, the second longitudinal end 60b extends inside the elastically deformable member 40, in particular the coil spring 40.

Thus, the diameter of the guide rod 64 is less than or equal to the internal diameter of the elastically deformable member 40.

According to an exemplary embodiment, the slider 62 may comprise a main body 620, in particular a cylindrical main body 620 extending around the longitudinal axis A. By way of example, the main body 620 may be a solid or hollow cylinder .

The slider 62, in particular the main body 620, is fixed to the second longitudinal end 60b in an axial direction opposite to the part 50. More specifically, the slider 62, in particular the main body 620, is attached at least partially to the intermediate portion 46 of the elastically deformable member 40.

Indeed, the slider 62, in particular the main body 620, can have a tubular shape, in particular molded, to correspond to the footprint of the elastically deformable member 40. Thus, according to a particular embodiment, the slider 62 can be assembled around at least one of the turns of the intermediate portion 46 of the elastically deformable member 40, as a coil spring 40, in the rest position.

The slider 62, in particular the main body 620, has a width iezo measured with respect to the longitudinal axis A. The width Ie2o is between a minimum value corresponding to the distance (d) between two adjacent turns, as illustrated on FIGS. 3a and 4c, and a maximum value corresponding to the length of several turns, for example four turns, of the coil spring 40 at rest. In particular, as shown in the example of Figure 6a, the main body 620 can cover approximately 3 to 4 coils of the coil spring 40.

Preferably, the main body 620 has a small width I ₆₂₀ to promote the deformation, both in extension and in compression, of the elastically deformable member 40, in particular along the longitudinal axis A, as illustrated in the figure 5b.

By way of example, in the case where the helical spring 40 comprises 10 turns, the main body 620 of the slider 62 can be fixed to the helical spring 40 so as to cover at least the distance (d) between the 5th ^and 6th ^e turns, i.e. at most to cover the 5 ^th and 6 ^th turns.

According to the invention, the first Bragg grating 30a, respectively the second Bragg grating 30b, of the optical fiber sensor 20 extends between the first end 42 of the elastically deformable member 40 and the movable member 60, and the second Bragg grating 30b, respectively the first Bragg grating 30a, extends between the second end 44 of the elastically deformable member 40 and the movable member 60.

Such a configuration of the invention makes it possible to create a translation Tr of the elastically deformable member 40 by the movable member 60 when the part 50 whose mechanical displacement is to be measured and/or controlled moves, and consequently to deform the first end 42 and the second end 44 comprising the fiber optic sensor 20.

In this way, the first Bragg grating 30a and the second Bragg grating 30b are able to measure a deformation in tension of the first end 42, respectively of the second end 44, and a deformation in compression of the second end 44, respectively. of the first end 42.

More particularly, the slider 62 is fixed on the intermediate portion 46 so as to separate the mechanical displacement measuring device 10 in two measuring regions.

In the example of Figures 5a and 5b, the slider 62 delimits a first region 32a corresponding substantially to the first end 42 comprising a first Bragg grating 30a and a second region 32b corresponding substantially at the second end 44 comprising the second Bragg grating 30b.

Referring to Figure 5a, the first end 42 is deformed in tension and the second end 44 is deformed in compression. Thus, the first Bragg grating 30a is capable of measuring the tensile deformation of the elastically deformable member 40 and the second Bragg grating 30b is capable of measuring the compressive deformation of the elastically deformable member 40.

Conversely, in the example of Figure 5b, the first end 42 is deformed in compression and the second end 44 is deformed in tension. Thus, the first Bragg grating 30a is capable of measuring the compression deformation of the elastically deformable member 40 and the second Bragg grating 30b is capable of measuring the tensile deformation of the elastically deformable member 40.

The position of the first Bragg grating 30a and of the second Bragg grating 30b of the fiber optic sensor 20 on the first end 42 and the second end 44 can be chosen so as to favor, for example, the symmetry of measurements and/or the fiber optic sensor sensitivity 20.

The fiber optic sensor 20 can be equipped with one or more Bragg gratings positioned on the first end 42 and the second end 44, so as to improve the measurement of deformation of the elastically deformable member 40.

Thus, in general, the mechanical displacement measuring device 10 is capable of measuring both a compression deformation and a tensile deformation of the elastically deformable member 40 via the first Bragg grating 30a and the second Bragg grating 30b of the fiber optic sensor 20.

This allows the mechanical displacement measuring device 10 to determine the mechanical displacement of the part 50 by calculating the difference of the measurements of the first Bragg grating 30a and the second Bragg grating 30b. For this, the fiber optic sensor 20 can be connected to a processing and analysis device 8. The processing and analysis device 8 receives data from the fiber optic sensor 20. For this purpose, the device processing and analysis 8 comprises a connector 8 'to be connected optical fiber sensor 20, as illustrated schematically in Figure 5a.

In the case where the mechanical displacement measuring device 10 comprises a single Bragg grating positioned per region of the elastically deformable member 40, namely the first Bragg grating 30a in the first region 32a and the second Bragg grating 30b in the second region 32b, the measurement of deformation by the first Bragg grating 30a and by the second Bragg grating 30b is obtained according to the laws:

- for the first Bragg grating 30a located in the first region 32a:

- And for the second Bragg grating 30b located in the second region 32b:

where :

Δλ30a is a wavelength variation of the first Bragg grating 30a;

Δλaob is a wavelength variation of the second Bragg grating 30b; K(T_30a) is a thermal sensitivity of the first Bragg grating 30a;

K(T 30a) is a thermal sensitivity of the second Bragg grating 30b; K( _ε _30a) is a mechanical sensitivity of the first Bragg grating 30a; K( _ε _30b) is a mechanical sensitivity of the second Bragg grating 30b; T is a temperature surrounding the deformation; ε is a deformation (compression or elongation) relative to the first Bragg grating and to the second Bragg grating.

The thermal sensitivity of the first Bragg grating K(T __30a) and the thermal sensitivity of the second Bragg grating K(r_30b) depend mainly on the index variation related to temperature. Since the first Bragg grating 30a and the second Bragg grating 30b are inscribed in the same optical fiber, the thermal sensitivity of the first Bragg grating K(T_ 30a) and the thermal sensitivity of the second Bragg grating K(r_30b) can be considered identical and equal.

The mechanical sensitivity of the first Bragg grating K(ε 30a) and the mechanical sensitivity of the second Bragg grating K(e 30b) come from the calibration of the optical fiber sensor 20 to the deformation and therefore to the displacement of the movable member 60. The values of mechanical sensitivity of the first Bragg grating K(ε_30a) and of the mechanical sensitivity of the second Bragg grating K(ε_30b) are therefore known.

The measuring device 10 is configured so that the translation Tr of the movable member 60 will cause variations of opposite signs on the first Bragg grating 30a and the second Bragg grating 30b. The first Bragg grating 30a will see an increase in its Bragg wavelength and the second Bragg grating 30b will see a decrease in its Bragg wavelength and vice versa.

Therefore, by calculating the difference between the variation in wavelength of the first Bragg grating Δλ _30a and the variation in wavelength of the second Bragg grating Δλ30b, the following equation is obtained:

Temperature is no longer a factor in this equation. It therefore follows that the value of the deformation relative to the first Bragg grating and to the second Bragg grating ε can therefore be determined independently of the temperature.

Knowledge of the deformation relating to the first Bragg grating and to the second Bragg grating E makes it possible to determine the value of the displacement of the mobile member 60 and, consequently, the value of the displacement of the part 50 which it is desired to measure and/or or control a mechanical movement via a prior calibration.

The preliminary calibration is obtained by measuring the variation in wavelength of the first Bragg grating Δλ _30a , respectively of the second Bragg grating Δλ _30b , connected to the deformation ε relative to the first Bragg grating 30a , respectively to the second Bragg grating 30b, via the mechanical sensitivity of the first Bragg grating K( _ε _30a), respectively of the second Bragg grating K( _ε _30b), as a function of the displacement (elongation or compression) of the elastically deformable member 40, in particular the helical spring 40, via the movable member 60, in particular the slider 62.

The rest position of the elastically deformable member 40, in particular of the helical spring 40, corresponds to the spectral shift reference point. In the case where the measuring device 10 comprises several Bragg gratings, in particular the first Bragg grating 30a and the second Bragg grating 30b, of the optical fiber sensor 20 positioned by first region 32a and second region 32b of the organ elastically deformable 40, an average value of the measurements of the Bragg gratings per region can be taken to determine the value of the mechanical displacement of the part 50.

Figures 6a to 6d are schematic views of a second embodiment of the mechanical displacement measuring device 10 according to the invention.

The mechanical displacement measuring device 10 of the second embodiment differs from the mechanical displacement measuring device 10 of the first embodiment by the movable member 60 and/or the fixed support 70. More particularly, the movable member 60 comprises the slider 62 and the guide rod 64. More specifically, the slider 62 further comprises a secondary body 622, in particular a cylindrical secondary body 622.

Referring to Figures 6a and 6b, the main body 620 is fixed to the guide rod 64 by the second longitudinal end 60b. The secondary body 622 extends radially outward from the main body 620, so that the main body 620 and the secondary body 622 are coaxial.

The secondary body 622 makes it possible to create peripheral guidance of the slider 62 along the longitudinal axis A, in particular by limiting the angular movement of the main body 620 during a movement, in particular along the longitudinal axis A.

In the example presented, the secondary body 622 has a width I ₆₂₂ greater than the width I ₆₂₀ of the main body 620.

Advantageously, the slider 62 and the fixed support 70 may comprise, respectively, guide members 76 and complementary members 626 cooperating with the guide members 76. The guide members 76 and the complementary members 626 make it possible to reinforce the limitation of the displacement angular slider 62 in translation along the longitudinal axis A. The guide members 76 and the complementary members 626 can be chosen in particular from rails, grooves, projecting teeth, stops and/or bores.

With reference to the variant presented in FIG. 6c, the secondary body 622 of the slider 62 comprises two projecting teeth as complementary members 626. Such complementary members 626 extend radially towards the outside of the secondary body 622. reference to the variant shown in Figure 6d, the fixed support 70 has a cylindrical shape of revolution comprising two grooves as guide members 76. The complementary members 626 and the guide members 76 cooperate by form complementarity to promote the guiding the slider 62 inside the fixed support 70.

Figures 7 to 11 are schematic views of a third embodiment of the mechanical displacement measuring device 10 according to the invention.

The mechanical displacement measuring device 10 of the third embodiment differs from the mechanical displacement measuring device 10 of the first embodiment by the movable member 60 and a fixing plug 80.

More particularly, with reference to Figure 7, the movable member 60 comprises a variant of the slider 62, a variant of the guide rod 64 and a guide roller 66, in particular a guide roller 66 cylindrical. The guide roller 66 makes it possible in particular to create a central guide for the slider 62 along the longitudinal axis A.

In Figure 8a, guide rod 64 extends along longitudinal axis A between first longitudinal end 60a and second longitudinal end 60b.

According to the third embodiment, the first longitudinal end 60a is similar to that described in relation to the first embodiment of the mechanical displacement measuring device 10 and the second longitudinal end 60b comprises at least one longitudinal extension 640. Preferably, the longitudinal extension 640 extends radially outward from the guide rod 64.

In the example, the second longitudinal end 60b and the longitudinal extension 640 extend on either side of the slider 62.

Furthermore, the slider 62 comprises an annular body 621 extending around the longitudinal axis A. The annular body 621 comprises at least one junction member 68 connecting the annular body 621 of the slider 62 to the longitudinal extension 640 of the guide rod 64. Junction member 68 may be a radial wall forming a connecting bridge between slider 62 and guide rod 64.

In Figure 8b, the slider 62 includes three junction members 68 and the guide rod 64 also includes three longitudinal extensions 640, so as to constitute a reinforcement of a solid connection between the slider 62 and the guide rod 64.

In the example of Figures 8a and 8b, the slider 62 and the guide rod 64 are in one piece. Alternatively, the slider 62 and the guide rod 64 could be unitary and interconnected.

Referring to Figure 9a, the guide roller 66 has an elongated cylindrical shape along the longitudinal axis A. The guide roller 66 extends between a first end face 664 and a second end face 666. The guide roller 66 further comprises a central opening 660 opening onto the first end face 664 and the second end face 666. The central opening 660 may have a diameter similar to an outer diameter of the guide rod 64. Central opening 660 is configured for insertion of at least a portion of guide rod 64.

The guide roller 66 further comprises at least one longitudinal groove 662. In particular, the longitudinal groove 662 extends at least over part of a length of the guide roller 66. In the example, the longitudinal groove 662 opens only on the first end face 666.

Furthermore, the longitudinal groove 662 is configured to have a complementary shape with the connecting member 68 of the slider 62. The longitudinal groove 662 makes it possible to guide the slider 62 and to avoid twists turns of the elastically deformable member 40 extending around the slider 62.

The longitudinal groove 662 may have a depth (p) less than a total height (h) of the guide roller 66. The depth (p) of the longitudinal groove 662 and the height (h) of the guide roller 66 are measured according to a plane perpendicular to the longitudinal axis A, as illustrated in Figure 9b. Preferably, the height (h) of the guide roller 66 is similar to the internal diameter of the annular body 621 of the slider 62.

As shown in Figure 9c, the guide roller 66 includes three longitudinal grooves 660, so as to receive the three junction members 68 of the slider 62 of Figure 8b.

Referring to Figure 10, the guide roller 66 is assembled, on the one hand, around the guide rod 64 through the central opening 660, and on the other hand, in the slider 62 through the longitudinal groove 662. The assembly consisting of the slider 62, the guide rod 64 and the guide roller 66 forms the movable member 60. Preferably, the slider 62, the guide rod 64 and the guide roller 66 are coaxial.

In the example, the guide roller 66 and the guide rod 64 extend on either side of the slider 62.

The slider 62, the guide rod 64 and the roller 66 can have variable dimensions, for example the size or the shape, depending on the part 50 to be measured and the space available in the environment of use. In the configuration of the movable member 60, the guide rod 64 connected to the slider 62 is therefore movable in translation through the guide roller 66 along the longitudinal axis A.

In a non-limiting way, the slider 62 extends between two adjacent turns of the elastically deformable member 40. The turns of the elastically deformable member 40 are arranged around the guide roller 66.

Advantageously, the second end face 666 of the roller can be fixed, for example by gluing, welding, screwing or any other fixing means, against the second transverse wall 74 of the fixed support 70. This makes it possible to reinforce the holding in position of the movable member 60 on the fixed support 70.

Furthermore, the first orifice 720 of the first transverse wall 72 can comprise the fixing cap 80 capable of fixing the first end 42 of the elastically deformable member 40 on the fixed support 70. Such a fixing configuration makes it possible to protect the first end 42 of the elastically deformable member 40 from any pinching of the optical fiber sensor 20 at the output of the mechanical displacement measuring device 10.

Referring to Figure 11, the fixing plug 80 has a generally frustoconical shape. The fixing plug 80 comprises a passage from the first end 42 of the elastically deformable member 40 incorporating the optical fiber sensor 20. The passage from the first end 42 opens between a first hole 84 and a second hole 88 made in the plug 80. Thus arranged, the first end 42 of the elastically deformable member 40 is inserted through the first hole 84 and the second hole 88 at the outlet of the mechanical displacement measuring device 10.

The passage of the first end 42 can be of linear shape or inclined with respect to the longitudinal axis A. In the example of Figure 11 and in a non-limiting way, the passage of the first end 42 is inclined so that the first hole 84 is formed on an outer face 82 of the fixing plug 80, with respect to the mechanical displacement measuring device 10, and the second hole 88 is formed on an outer surface 86 of the fixing plug 80, with respect to the longitudinal axis A.

Thus, at least a portion of the turns of the first end 42 of the elastically deformable member 40 are wound around the outer surface 86 of the fixing cap 80. As a result, the first end 42 of the elastically deformable member 40 is inserted through the second hole 88 and passes through the first hole 84 of the fixing plug 80 to exit the mechanical displacement measuring device 10 in order to connect the fiber optic sensor 20 to the processing and analysis device 8.

Preferably, the outer diameter of the attachment plug 80 is similar to the diameter of the first orifice 720 of the first transverse wall 72. FIG. 12 is a schematic view of a fourth embodiment of the mechanical displacement measuring device 10 according to the invention.

The mechanical displacement measuring device 10 of the fourth embodiment differs from the device of the first embodiment by the movable member 60.

More particularly, the movable member 60 of the fourth embodiment comprises a variant of the slider 62, a variant of the guide rod 64 and a variant of the guide roller 66.

In Figure 12, the guide rod 64 extends along the longitudinal axis A between the first longitudinal end 60a and the second longitudinal end 60b. The second longitudinal end 60b is fixed to the main body 620 of the slider 62. The guide rod 64 may have an external diameter similar to the internal diameter of the main body 620.

In the example, the slider 62 and the guide rod 64 are in one piece. Alternatively, the slider 62 and the guide rod 64 could be unitary and interconnected.

Guide rod 64 includes at least one longitudinal slot 642 and at least one first guide member 641 extending inward from guide rod 64.

The first guide member 641 can be a radial extension or a groove allowing a sliding connection with the guide roller 66.

In the example, the longitudinal slot 642 extends on either side of the first guide member 641. The longitudinal slot 642 is through and extends over the entire guide rod 64.

Guide rod 64 further includes a central opening 644 configured for at least partial insertion of guide roller 66.

Guide roller 66 extends between first end face 664 and second end face 666 along longitudinal axis A.

The guide roller 66 comprises at least a second guide member 661 of complementary shape with the first guide member 641 of the guide rod 64. The second guide member 661 can be a longitudinal groove or a longitudinal extension extending radially outward from the guide roller 66. In the example, the second guide member 661 extends substantially over the entire length of the second longitudinal end 60b and opens towards the first end face of the guide roller 66. The second guide member 661 is configured to have a shape complementary to the first guide member 641 of the guide rod 64. This makes it possible to guide the slider 62 in translation along the longitudinal axis A.

The guide roller 66 is therefore assembled in the guide rod 64 via the central opening 660 and the second guide member 661. The assembly consisting of the slider 62, the guide rod 64 and the guide 66 forming the movable member 60 are coaxial.

In this configuration of the movable member 60, the guide rod 64 fixed to the slider 62 is therefore movable in translation around the guide roller 66 along the longitudinal axis A.

In a non-limiting way, the slider 62 extends between two adjacent turns of the elastically deformable member 40. The turns of the elastically deformable member 40 are arranged around the guide rod 64. Advantageously, the second end face 664 of the guide roller 66 can be fixed, for example by gluing, welding, screwing or any other fixing means, against the second transverse wall 74 of the fixed support 70.

Figures 13a and 13b are schematic views of a fifth embodiment of the mechanical displacement measuring device 10 according to the invention.

The mechanical displacement measuring device 10 of the fifth embodiment differs from the mechanical displacement measuring device 10 of the first mode to the fourth embodiment by the addition of a counter-reaction spring 90.

In FIG. 13a, the mechanical displacement measuring device 10 further comprises the counter-reaction spring 90 fixed between the fixed support 70, in particular the first transverse wall 72, and the slider 62.

The counter-reaction spring 90 has a return force greater than a return force of the elastically deformable member 40. In this way, the slider 62 is in abutment position on fixed support 70, so that second end 44 is compressed on second transverse wall 74. This creates an equilibrium position of slider 62 in which elastically deformable member 40, in position of rest, is compressed on one side. A better equilibrium position of the slider 62 is thus obtained in order to optimize the measurements of mechanical displacements of the part 50 with respect to this equilibrium position.

The invention also relates to a system for measuring the mechanical displacements of a part 50 for an aircraft propulsion assembly. Such a measurement system comprises the part 50 whose mechanical displacement is to be measured and/or controlled and at least one mechanical displacement measuring device 10 according to the invention connected to the part 50.

The measurement system may include the device 8 for processing and analyzing data from the fiber optic sensor 20.

The invention also relates to an aircraft propulsion assembly comprising a turbomachine and a nacelle forming an outer annular envelope of the turbomachine, not illustrated in the figures. The propulsion assembly comprises at least one part 50 connected to a mechanical displacement measuring device 10 according to the invention and/or to a measuring system according to the invention for measuring the mechanical displacements of the fixed or mobile part 50 of the turbomachine and/or nacelle.

Advantageously, the mechanical displacement measuring device 10 or the measuring system according to the invention are fixed to a structural casing of the turbomachine and/or of the nacelle not illustrated in the figures. By way of example, the part 50 to be measured can be a part of a thrust reverser, such as deflector flaps.

Obviously, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms and other variants that a person skilled in the art may consider within the scope of the invention and in particular all combinations of the different operating modes described above, which can be taken separately or in combination.

Claims

29 CLAIMS

1. Mechanical displacement measuring device (10) of at least one part (50), in particular of an aircraft propulsion assembly, comprising:

- at least one optical fiber sensor (20) comprising at least one first Bragg grating (30a) and at least one second Bragg grating (30b),

- an elastically deformable member (40) fitted with the fiber optic sensor (20), and

- a movable member (60) integral with the elastically deformable member (40) and comprising a first longitudinal end (60a) configured to be fixed to the part (50), characterized in that the first Bragg grating (30a) s extends between the movable member (60) and a first end (42) of the elastically deformable member (40) and the second Bragg grating (30a) extends between the movable member (60) and a second end (44) of the elastically deformable member (40), and in that the mechanical displacement measuring device (10) further comprises a fixed support (70) to which the first end (42) and the second end ( 44) of the elastically deformable member (40).

2. Device for measuring mechanical displacement (10) according to the preceding claim, characterized in that the fixed support (70) comprises longitudinal ends provided respectively with a first transverse wall (72) and a second transverse wall (74 ) to which are fixed the first end (42) and the second end (44) of the elastically deformable member (40).

3. Mechanical displacement measuring device (10) according to one of the preceding claims, characterized in that the movable member (60) comprises a guide rod (64) and a slider (62).

4. Mechanical displacement measuring device (10) according to the preceding claim, characterized in that the slider (62) is fixed to an intermediate portion (46) of the elastically deformable member (40).

5. Mechanical displacement measuring device (10) according to claim 3 or 4, characterized in that the movable member (60) further comprises a guide roller (66) extending in the member elastically 30 deformable (40) and comprising a central opening (660) adapted to allow the insertion of at least a portion of the guide rod (64) and at least one longitudinal groove (662) of complementary shape with at least one member junction (68) connecting the guide rod (64) to the slider (62).

6. Mechanical displacement measuring device (10) according to any one of claims 3 to 5, characterized in that the fixed support (70) comprises guide members (76) cooperating with complementary members (626) of the slider (62).

7. Mechanical displacement measuring device (10) according to one of claims 3 to 6, characterized in that it further comprises a counter-reaction spring (90) whose ends are connected, respectively, to the slider ( 62) and to the fixed support (70).

8. Device for measuring mechanical displacement (10) according to any one of the preceding claims, characterized in that the elastically deformable member (40) comprises an internal passage (48), in particular over its entire extent, inside from which the fiber optic sensor (20) extends.

9. Mechanical displacement measuring device (10) according to any one of the preceding claims, characterized in that the fiber optic sensor (20) is fixed along an outer surface (44) of the elastically deformable member (40).

10. Device for measuring mechanical displacement (10) according to the preceding claim, characterized in that the elastically deformable member (40) comprises a sheath (49), in particular of heat-shrinkable material, capable of wrapping and securing the fiber sensor optic (20) on the elastically deformable member (40).

11. Mechanical displacement measuring device (10) according to any one of the preceding claims, characterized in that the elastically deformable member (40) is a helical spring formed by a tubular wire or by a solid wire.

12. System for measuring the mechanical displacement of at least one part (50) comprising at least one mechanical displacement measuring device (10) according to any one of the preceding claims and a device for processing and analysis (8) of data from a fiber optic sensor (20).

13. Aircraft propulsion assembly comprising a mechanical displacement measuring system comprising at least one mechanical displacement measuring device (10) according to one of claims 1 to 11.

14. Aircraft comprising at least one aircraft propulsion assembly according to the preceding claim.