DE202015106397U1 - Bending measuring device with optical fiber - Google Patents

Abstract

Bending measuring device for optical bending measurement on a component (R), comprising a first optical waveguide (1), a light source (4) and a light sensor (5) at a first end (11) of the first optical waveguide (1) and a coupling point (3) at the second end (12) of the first optical waveguide (1) having a first end surface (13) and a reflection surface (31), wherein an optical signal from the light source (4) to the light sensor (5) via the coupling point (3) is passed, characterized in that the first optical waveguide (1) in the region of the coupling point (3) with the component (R) is connected and the surface normals of the first end face (13) and the reflection surface (31) by an angle (δ) with δ> 0 differ from each other.

Description

The invention relates to a bending measuring device for optical bending measurement on a component, comprising a first optical waveguide, a light source and a light sensor at a first end of the first optical waveguide and a coupling point at the second end of the first optical waveguide having a first end surface and a reflection surface, wherein an optical Signal is passed from the light source to the light sensor via the coupling point. Furthermore, the invention relates to a bending measuring device for optical bending measurement on a component with two optical waveguides, a light source at a first end of the first optical waveguide and a light sensor at a second end of the second optical waveguide and a coupling point between a first end surface at the second end of the first optical waveguide and a second end surface at the first end of the second optical fiber, wherein an optical signal is passed from the light source to the light sensor via the coupling point.

Bending measuring devices with an optical waveguide are known in various embodiments in the prior art.

The DE 10 2006 027 421 B3 describes a method for producing a bending sensor, on which at least one sensing region is formed by providing a flexurally elastic base jacket, which is interrupted in at least a portion of the sensing region or structured by elevations and / or depressions. At least one planar fiber core is created on the base shell. The optical fiber core has a greater refractive index than the base cladding. The fiber optic core is covered by a cover. This bending sensor is provided for an impact sensor device of a pedestrian protection system of a vehicle.

In the DE 20 2010 002 129 U1 a sensor for detecting relative movements between objects, in particular the occurrence of cracks in structures and their dynamic development is shown. In this case, a first surface of the first sensor element faces a second surface of a second sensor element, these surfaces move relative to each other in a relative movement of the sensor elements due to a relative movement of the objects and the first sensor element at least a first transmission device for supplying a signal to the sensor and the second sensor element has at least one second transmission device for routing the signal from the sensor, wherein the first and second transmission device are arranged and configured such that the signal is only at least one predetermined relative position between the two sensor elements of at least one first transmission device on at least one second transmission device couples over.

The US 2003/0231818 A1 describes an optical sensor integrated in the edge region of the optical fiber. Shantless sections of the fiber thereby form optical sensors which, filled with a special sensor material, form the measuring system, in particular for temperature measurement.

Next is from the DE 10 2006 048 635 B4 a fiber optic bending sensor and a method of manufacturing the same, comprising means for detecting a deformation based on a change in the intensity of light received from the optical fiber, wherein light emitting regions are arranged in the form of one or more stripes extending through the fiber cross section. Thus, a distinction between positive and negative bending can be achieved by intensity amplification in one direction and intensity attenuation in the other bending direction. This fiber-optic sensor is designed for the detection of bending stress over a wide sensitive zone, here impact area of a pedestrian on a motor vehicle. It is disadvantageous that the sensor fibers for forming the strips according to the invention by direct writing or photo-inscription for the production of refractive index changes must be elaborately processed and prefabricated.

Starting from a fiber optic bending sensor according to DE 10 2006 048 635 B4 It is an object of the invention to provide a bending sensor, which is suitable for monitoring the stress of components, for example, for rotor blades of wind turbines, which can detect direction-dependent bending stress at a point of the component.

This object is achieved with a bending measuring device according to claim 1. Due to the fact that the first optical waveguide in the region of the coupling point is connected to the component and the surface normals of the first end surface and the reflection surface deviate from each other by an angle δ with δ> 0, the load is unloaded (not bent) basic position (mean angle δ) reaches an average attenuation of the optical signal at the coupling point. With a positive bending stress at this point that the instantaneous angle δ _m opens between end surface and reflecting surface or between the two opposing end faces δ _m> δ, so that through the bending measuring both the amplitude (decrease the attenuation; flexural strength) as well as the bending direction (positive bending) can be determined. In a negative bend, the angle between the end surfaces and the end surface and the reflection surface becomes δ _m <δ, so that the Damping increases and can be derived from the negative bending in magnitude and direction. In this case, the direction of the inclination of the end face predetermines the measuring direction of the bending measurement, so that with this device a selective bending measurement of a bending occurring in a spatial direction can be measured. Two 90 ° twisted sensor fibers can thus measure the bending of an elongate structure (rotor blade) in all radial directions to the elongated structure.

Alternatively, the bending measuring device consists of two optical waveguides, wherein the two optical waveguides are connected to the component in the region of the coupling point and the surface normals of the first end surface and the second end surface deviate from one another by an angle δ of δ> 0. Here, at the coupling point as well as in the embodiment according to claim 1, an average damping in the basic position δ realized, with subsequent deflections are recognized both in terms of magnitude as well as from the direction forth.

If the surface normal of the reflection surface coincides with the optical axis of the first optical waveguide, the reflection surface can simply be oriented exactly perpendicular to the optical axis of the optical waveguide facing the reflection surface, wherein the first end surface of the first optical waveguide is inclined at an angle δ to the optical axis of the optical waveguide is designed.

Accordingly, the surface normal of the second end surface may coincide with the optical axis of the second optical fiber. Alternatively, the surface normal of the first end surface may coincide with the optical axis of the first optical fiber.

If the first and / or second optical waveguide is a multi-core optical fiber cable made of a plurality of individual fibers (multicore fiber), the bending measuring device outside the coupling point is largely insensitive to shocks and bends elsewhere.

If the inclined by an angle (δ) with δ> 0 first or second end surface is formed as a bevel, the optical waveguide, especially in the form of a multi-core optical fiber cable easily on site in the desired shape.

Hereinafter, the invention with reference to the accompanying drawings described in detail.

It shows:

1 the numerical aperture of a known optical fiber;

2 the numerical aperture of an optical fiber having an angled end surface;

3 a coupling point according to the invention in the basic position;

4 in the 3 shown coupling point deflected upwards;

5 in the 3 shown coupling point deflected downwards;

6 an alternative embodiment of a coupling point with two angled end surfaces;

7 a further embodiment of a coupling point with reflection surface and

8th a schematic arrangement of a bending measuring device on a rotor blade.

The bending measuring device according to the invention is based on an attenuation evaluation at a coupling point in a multimode optical waveguide. The bending measurement takes place in the area of the coupling point.

In 1 an optical waveguide is shown having an orthogonal to its optical axis oriented end face. In the optical waveguide, the light spreads symmetrically to the optical axis, as indicated by the light beams. Due to the orthogonally oriented end surface of the optical waveguide, the numerical aperture is also symmetrical to the optical axis, namely α ₁ = α ₂ and β ₁ = β ₂ .

In the case of an optical waveguide with an angled end surface (angle δ), as shown in 2 is shown, the numerical aperture changes such that the angles β ₁ and β _{2 are} no longer oriented symmetrically with respect to the optical axis of the fiber. The radiation characteristic rotates in the clockwise direction about a point of contact P of the optical waveguide with the result that β ₁ > β ₂ .

The bending measuring device according to the invention 3 has a first optical waveguide 1 and a second optical fiber 2 on, being on the second end 12 of the first optical waveguide 1 a first end surface 13 is formed in the form of a bevel cut. At the first end 21 of the second optical waveguide 2 is a second endface 23 formed, which is aligned orthogonal to the optical axis.

The first endface 13 and the second end surface 23 abut one another at a point of contact P and form a coupling point 3 , By doing that, the first end face 13 is aligned at an angle δ to the orthogonal plane to the optical axis by means of bevel grinding, forms at the coupling point 3 a wedge-shaped air gap. As again in 3 is shown, this comes from a light source, not shown 4 at the first end of the first optical waveguide, not shown 1 fed light symmetrical to the first end surface 13 and gets there from the sloping endface 13 unbalanced in the second optical fiber 2 at the second end surface 23 coupled. This results in a violation of the so-called acceptance angle θ, so that a portion of the light outside the in 3 dashed line, not in the optical fiber 2 can continue and is decoupled from the optical fiber. Accordingly, there is an attenuation of the light signal, which has a second end, not shown 22 of the second optical waveguide 2 arranged light sensor 5 (not shown) is measured.

In 4 is the bending measuring device to the point of contact or bending point P at his in 4 right leg lying upwards. This causes the difference between γ ₂ and the acceptance angle θ to become larger, so that even more light from the second optical waveguide 2 is decoupled. It follows that in the second optical fiber 2 guided amount of light decreases with decreasing angle δ.

In 5 an opposite bend takes place around the bending point P, whereby the instantaneous angle δ _m between the two end faces 13 . 23 increases δ _m > δ. Consequently, the difference γ ₂ and θ becomes smaller, so that more light enters the second optical fiber 2 is coupled. It follows that in the second optical fiber 2 guided amount of light with increasing angle (up to max γ ₂ = θ) is greater.

Thus, the amount of light is modeled by the deflection of the optical waveguide about the bending point P. The direction of the deflection can be detected by the increase or decrease in the amount of light, from which the rotation about the bending point P and thus the bending to be measured can be determined. The system is reversible because the direction of the light has no influence on the operating principle.

In a further embodiment, both end surfaces can 13 and 23 a beveled, possibly also with different angles δ ₁ and δ ₂ , such as 6 shows. Decisive is the size of the angle δ ₁ + δ ₂ as a wedge-shaped opening of the coupling point 3 ,

In a further embodiment, only a first optical waveguide 1 with a first end surface 13 be present in the oblique cut, wherein the coupling point 3 with a reflection surface 31 is formed. Im in 7 illustrated embodiment is the reflection surface 31 orthogonal to the optical axis of the first optical fiber 1 aligned. Of course, here too the constellation as in 6 be formed or only the reflection surface 31 be placed obliquely to the optical axis, in which case the first end surface 13 of the first optical waveguide 1 would have an orthogonal to the optical axis guided surface.

In 8th is a schematic diagram showing the arrangement of a bending measuring device according to the invention on a rotor blade R of a wind turbine. In this case, the bending measuring device is arranged with its point of contact or bending point P at a particular stress point of the rotor R and connected to the rotor blade R. In 8th to the left of the bending point P is the first optical waveguide 1 arranged. At its first end from the bending measuring device 11 of the first optical waveguide 1 is a light source 4 , For example, arranged an LED for coupling a light signal. The second end 12 of the first optical waveguide 1 forms the beveled first end surface 13 , which ends immediately at the bending point P. This is followed as part of the coupling point 3 the second optical fiber 2 with his first end 21 as the second end face 23 orthogonal to the optical axis, at. The second optical fiber 2 has at its second end 22 a light sensor 5 for the evaluation of the coupling point 3 in a certain way attenuated light signal coming from the light source 4 is sent out.

The coupling point 3 is arranged directly at the bending point P and consists of the two opposing end surfaces, namely the first, obliquely ground end surface 13 and the second end face oriented orthogonally to the optical axis 23 , wherein a wedge-shaped air space with an opening angle of δ forms between these two surfaces.

In the case of bending stresses of the rotor R, this wedge-shaped air gap changes, wherein an instantaneous angular range with δ _m > δ results in one bending direction and δ _m <δ in the other bending direction. With this according to 8th arranged in a rotor blade R bending measuring device can both high-frequency vibrations, for example in the range of 50 Hz to 300 Hz, which act in particular to the rotor axis of the wind turbine tangential direction on the rotor blade R, as well as low-frequency vibrations of, for example, 1/10 Hz, in the rotor axis the wind turbine parallel direction on the rotor blade R act, with correspondingly rotated by 90 ° oriented bending measuring devices are measured.

LIST OF REFERENCE NUMBERS

1

first optical fiber

11

first end of the first optical fiber

12

second end of the first optical fiber

13

first end surface

2

second optical fiber

21

first end of the second optical fiber

22

second end of the second optical fiber

23

second end surface

3

coupling point

31

reflecting surface

4

light source

5

light sensor

P

Touch point, bending point

θ

acceptance angle

δ

Angle (oblique cut)

R

rotor blade

X

optical axis

Y

deflection

Z

axis of rotation

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006027421 B3 [0003]
• DE 202010002129 U1 [0004]
• US 2003/0231818 A1 [0005]
• DE 102006048635 B4 [0006, 0007]

Claims (7)

Bending measuring device, for optical bending measurement on a component (R), with a first optical waveguide ( 1 ), a light source ( 4 ) and a light sensor ( 5 ) at a first end ( 11 ) of the first optical waveguide ( 1 ) and a coupling point ( 3 ) at the second end ( 12 ) of the first optical waveguide ( 1 ) having a first end surface ( 13 ) and a reflection surface ( 31 ), wherein an optical signal from the light source ( 4 ) to the light sensor ( 5 ) via the coupling point ( 3 ), characterized in that the first optical waveguide ( 1 ) in the region of the coupling point ( 3 ) is connected to the component (R) and the surface normals of the first end surface ( 13 ) and the reflection surface ( 31 ) differ by an angle (δ) with δ> 0. Bending measuring device according to claim 1, characterized in that the surface normal of the reflection surface ( 31 ) with the optical axis (X) of the first optical waveguide ( 1 ) coincides. Bending measuring device for optical bending measurement on a component (R) with two optical waveguides ( 1 . 2 ), a light source ( 4 ) at a first end ( 11 ) of the first optical waveguide ( 1 ) and a light sensor ( 5 ) at a second end ( 22 ) of the second optical waveguide ( 2 ) and a coupling point ( 3 ) between a first end surface ( 13 ) at the second end ( 12 ) of the first optical waveguide ( 1 ) and a second end surface ( 23 ) at the first end ( 21 ) of the second optical waveguide ( 2 ), wherein an optical signal from the light source ( 4 ) to the light sensor ( 5 ) via the coupling point ( 3 ), characterized in that the two optical fibers ( 1 . 2 ) in the region of the coupling point ( 3 ) are connected to the component (R) and the surface normals of the first end surface ( 13 ) and the second end surface ( 23 ) differ by an angle (δ) with δ> 0. Bending measuring device according to claim 3, characterized in that the surface normal of the second end surface ( 23 ) with the optical axis (X) of the second optical waveguide ( 2 ) coincides. Bending measuring device according to claim 1 or 3, characterized in that the surface normal of the first end face ( 13 ) with the optical axis (X) of the first optical waveguide ( 1 ) coincides. Bending measuring device according to one of the preceding claims, characterized in that the first and / or second optical waveguide ( 1 . 2 ) is a multi-core optical fiber cable of a plurality of individual fibers. Bending measuring device according to one of the preceding claims, characterized in that the first or second end surface inclined by an angle (δ) with δ> 0 ( 13 . 23 ) is designed as a tapered cut.

Images