WO2010089139A1

WO2010089139A1 - Measuring device for measuring deformations of elastically deformable objects

Info

Publication number: WO2010089139A1
Application number: PCT/EP2010/000738
Authority: WO
Inventors: Bernhardt Furrer; Joachim Ihlefeld; Theo Knaus; Christoph Kluser; Joachim Tiedeke
Original assignee: Baumer Innotec Ag
Priority date: 2009-02-06
Filing date: 2010-02-05
Publication date: 2010-08-12
Also published as: DE102009007938A1; EP2394136A1

Abstract

The invention relates to a device for measuring deformations of an elastic, elongated carrier structure, comprising at least one optically detectable marking at a first longitudinal position along the elongated carrier structure, and at least on electronic camera having an objective and a matrix sensor. The objective of the camera is aligned toward the at least one optically detectable marking, such that the marking is depicted on the matrix sensor and the camera faces the marking in the longitudinal direction along the carrier structure. The image data of the camera are fed to an image processing device set up for determining the position of the marking within the image field by means of an image detection. A deviation of the position of the marking from at least one target value is determined and quantified by means of a calculating device.

Description

Measuring device for measuring deformations of elastically deformable objects

description

The invention generally relates to the measurement of elastic deformations. In particular, the invention relates to the measurement of deformations of an object, such as an elongate carrier, such as a windmill blade or a wing.

In order to detect deformation of carrier elements, in particular strain gauges (DMS) are known.

With these strips, stretching deformations can be detected. They often form the measuring device of scales of all sizes, from household scales to crane scales. Also deformation measurements in steel construction or can also be realized by strain gauge measurements. To measure the strain by the change in resistance of the strain gage, bridge circuits, such as a Wheatstone bridge, are typically used. The mechanical coupling of the strain gauge is typically done by gluing.

Although the DMS-guided measurements are of high accuracy, there are still some disadvantages. If the structures at which the deformation is to be measured are very long and the deformation itself is relatively small, a very long strain gauge would have to be used for a reliable measurement. This increases the expenditure on equipment, as well as the weight. It must also be ensured that the connection of the elastic support to the DMS remains stable for a long time. Moreover, in the case of a permanent change in the resistance parameters, it can not be concluded whether a permanent deformation of the actual carrier or possibly an age-related change in the resistance values of the strain gage or the bridge circuit are the cause.

From EP 1 742 015 Bl, in-situ monitoring of blades and turbines within a gas turbine engine is known. For this purpose, a device is provided, which comprises a camera and a light source, wherein the light source causes an illumination of the rotating component during operation, while the camera receives an image of the component during operation. A controller compares the images of the component to changes in the component

Monitor component. The camera rotates with the component and provides images of at least one target portion of the component. The controller makes a comparison of the received images for detecting changes in the component. Because to verify a deformation the

Marking must always be in the field of vision of the camera, the system is primarily suitable for detecting small deformations.

Similarly, WO 2004/038328 A2 is based on attaching one or more cameras to a first part of an aircraft structure and target objects to a second part of the aircraft structure to detect deformations of an element of an aircraft, the target objects in view of the one or more cameras lie. It will take a series of pictures and processed to determine the size and direction of movement of the target object (s).

From EP 1 361 445 Al an anemometer for wind turbines is known in which a laser beam through the mast of

Wind turbine is directed through to a target object. With a camera, the laser beam is recorded on the target object. Based on the deformation of the mast caused displacement of the point of impact of the laser beam on the target object, the wind direction is determined.

US 7377181 Bl describes a measuring system for the detection of stresses in test bodies. For this purpose, a marking pattern with coded markings is applied to a test body. Based on the coded markings, targets are identified by means of a camera. To determine material stresses, changes in the distance of the target marks are then determined on the basis of the camera images. This method is accordingly sensitive to stretching or compression, but relatively insensitive to bending.

The invention is therefore based on the object to solve the above problems, especially for longer measuring distances. This object is solved by the subject matter of the independent claims. Advantageous embodiments and further developments of the invention are specified in the respective dependent claims.

Accordingly, the invention provides a device for measuring deformations of an elastically deformable object, preferably an elongate support structure. This device comprises at least one optically detectable marking at a first longitudinal position along the elastically deformable object, and at least one electronic camera with an objective and a matrix sensor, wherein the lens of the camera is directed to the at least one optically detectable marker such that the marker is imaged onto the matrix sensor and the camera looks longitudinally along the elastically deformable object at the marker. The device for measuring deformations further comprises an image processing device to which the image data are supplied to the camera. The

Image processing device is set up to determine the position of the marking within the image field on the basis of an image recognition. It is also one

Calculating device provided, which is adapted to determine a deviation of the position of the marking of at least one desired value and quantify.

By means of this device, a method for measuring deformations of the elastically deformable object, such as a support structure is performed, wherein at least one optically detectable mark at a first longitudinal position along the elastically deformable object, and at least one electronic camera with a

Lens and a matrix sensor is used, the lens of the camera is directed to the at least one optically detectable marker, such that the marker is imaged on the matrix sensor and the camera looks at the marker (for example, in FIG

Longitudinal direction along an object in the form of an elastically deformable support structure), wherein an image processing device, the image data to the camera are supplied, and wherein the image processing device performs an image recognition, so that the position of the marker within the image field is determined, and wherein by means of a computing device determines a deviation of the position of the marker of at least one target value and the position the marker within the image field is quantified.

The invention allows a highly accurate detection of deformations of the elastically deformable object without strain gauges. The installation effort is considerably reduced, since a gluing of the strain gauge is eliminated.

In a preferred embodiment of the invention, the camera is arranged at a second longitudinal position spaced from the first longitudinal position in the longitudinal direction. However, it is also possible to arrange the camera outside the elastically deformable object. Also in this case, the camera preferably looks in the longitudinal direction along the object, such as in particular an elongate support structure on the marking. This can be done in a simple way by an arrangement in extension of

Longitudinal direction of the support structure or by an optical deflecting element in the beam path, such as a mirror or a prism can be realized.

In particular, it is beneficial to exploit existing cavities in the object by the marker is disposed within a cavity. Such cavities are especially with elongated support structures often present. For example, various carriers, such as tubular or bay-shaped carriers are hollow inside. It is then generally advisable to illuminate the marking by means of a lighting device.

With the invention, it is also possible, in a very simple manner, to track and quantify deformations in all spatial directions. This can be achieved by at least two along the

Markings provided at different distances from the camera are provided in the longitudinal direction, wherein the computing device is set up to determine and quantify a change in length or an uneven deformation of the support structure or another object on the basis of a comparison of the positions of the two markings.

Such an uneven deformation can be done by measuring the deformation in two distances. If there is a normal deformation, such as a deflection, then both marks are on or near a setpoint curve. A deviation of the position of the markings from the curvature curve known from the structure can be caused for example by a kink or a local weakening of the structure. If such a deviation is detected, for example, a warning signal can be generated or the device can be switched off with the carrier or another elastically deformable object, or moved to a safe state. The invention will be described below with reference to the deformation of an elastically deformable carrier. The invention can equally be applied to other elastically deformable objects in the same way.

In order to be able to distinguish the markings arranged at different distances, it may be advantageous to use different shapes of markings, for example different reflectors, which can then be discriminated with image processing. Further

Distinguishing features could be different "colors" (wavelengths of reflection) or mounting directions. The distinguishing features could also be combined. If different "colors" are used, they can be distinguished by a color camera or by different illuminations. An encoding of different markings can be achieved in an advantageous manner by one or more wavelength-selective filters, in particular color filters on the markings. Then, in different embodiments, the different markings with different wavelengths can be illuminated and selectively evaluated in a further development of the invention.

It can be used in a further development of the invention, more than two at different distances to the camera arranged markings. For example, a plurality of reflectors can be arranged one behind the other and viewed with the camera in an axis or at an angle, wherein the lateral and / or axial displacement is evaluated. Furthermore, it is also possible to determine a torsion of the support structure about its longitudinal axis. For this purpose, in a further development of the invention, a marking with at least two marking elements spaced laterally from the viewing direction is used, whereby a torsion of the elastic, elongate carrier structure is determined and quantified on the basis of a rotation of the marking elements in the image plane. Due to the torsion, the marking elements rotate about a pivot point in the image plane. The fulcrum does not have to lie within the image field itself. However, the torsion then still leads to a change in the angle of the path connecting the two elements.

A suitable illumination of the marking can be realized by a laser by the laser is aligned parallel to the viewing direction of the camera on the marking. A cheap, space-saving option is, for example, to couple the laser by means of a beam splitter paraxial to the viewing direction of the camera. The coupling can also be done within the lens, or within the camera.

Preferably, the invention is used to determine deformations at longer distances. The length of the optical path between the matrix sensor and the marking can be at least 4 meters, preferably at least 6 meters. If the measuring device according to the invention is installed in the interior of a carrier structure, the distance between the marking and the camera, or more generally the length of the optical path along the longitudinal direction of the carrier structure in essentially only limited by the fact that the mark is shadowed by a deflection of the limiting walls.

With the invention, in particular, a control can be constructed, with which deformations of the support structure is counteracted. For this purpose, a control device is provided with a device according to the invention for measuring deformations, wherein the control device comprises an actuating device with at least one actuator, with which the elastic deformation is counteracted in response to the fact that the calculation device has quantified a deviation of the marking from a desired position , Adjustment may in particular be made dependent on the deformation exceeding or reaching a predefined limit value.

According to another aspect of the invention, there is provided an aerodynamic wing having a means for measuring deformations as described herein, and a rotor of a wind turbine, the rotor comprising such an aerodynamic wing. It is expedient to arrange at least the marking of the measuring device in the interior of the wing and to provide an active illumination of the mark.

The camera can be housed in the wing, or rotor blade itself. But it also makes sense to arrange the camera in the rotor hub. Thus, electrical or electronic elements within the rotor blade can be avoided. Alternatively or additionally, the invention can also be used in the tower of the wind turbine, which carries the rotor.

The invention can be used here in a particularly advantageous manner together with a control device as described above, wherein the actuator comprises an actuator for adjusting the angle of attack, and wherein the adjusting device changes the angle of attack of the rotor blade. Also, generally, the buoyancy of the wing may be changed by means of one or more actuators. This is especially thought of the flaps on the wings of an aircraft.

In order to be able to accurately quantify a deformation based on the position of the mark in the field of view of the camera, the knowledge of the distance of the mark from the camera is valuable. In the simplest case, the marking is attached at a defined distance to the support structure. But it is also possible to design the measuring device self-calibrating. For this purpose, according to an embodiment of the invention, it is provided that the length of the optical path from the matrix sensor to the marking is determined by a transit time measurement of a light beam or by the size of a pattern projected onto the marking. For example, a laser may project a grid onto the surface of the pattern. Based on the distances of the pattern, the distance from the camera can then be determined automatically by triangulation in a simple manner. In a corresponding manner, it is also possible depending on the design of the marker, based on the Size of the marking or the distance of marking elements in the image plane by triangulation to calibrate.

In the simplest embodiment of the invention, the marking can be given by points or stripes or similar structures that contrast with the surroundings of the marking.

Up to certain frequencies, vibrations of the support structure, such as. measure about one wing directly.

Essential is the frame rate of the camera. The use of modern digital chips, in which a ROI (Region of Interest) can be set and only this area can be read, allow increased measurement frequencies. Even if the measurement frequency is limited, however, higher frequencies can also be measured in their direction and amplitude by smearing the image of the mark. A direct measurement of the vibrations is readily possible for frequencies up to 20 hertz with a picture repetition rate of at least 50 hertz, preferably at least 60 hertz.

For a direct measurement of the vibration of the carrier structure, an image sequence is recorded and determined on the basis of the course determined by the individual images of the change in position of the marking of at least one of the parameters amplitude and frequency of the vibration by means of the computing device.

According to one embodiment of the invention, which is the subject of the present application in particular, the tag comprises a code in which a location information of the Position of the code is coded, wherein the computing means is adapted to decode the code and thus determine the location of the field of view of the camera on the object. On the basis of a so determined spatial displacement of the deformation can then be determined relative to a reference position. In particular, the location shift can be determined with subpixel resolution. The code may include the shape of a strip and / or dot pattern or any symbols such as characters, textures, color markers in which position data are encoded include. Is the information of the code by the

Image processing device decoded, is directly a location information ready, which provides the location of the image field on the coded object, preferably its center. The code thus represents a position code, preferably in two dimensions. If the carrier structure deforms, the location of the field of view of the camera moves over the code in accordance with the relative movement between the camera and the code due to the deformation. The determination of the position of the field of view based on the code in the field of view has the particular advantage that a large measuring range is achieved with simultaneously high measuring accuracy. Even with large deformations, the marker does not get out of sight of the camera, because new code elements in the field of view of

Camera arrive. Furthermore, it is advantageous that the influence of distortions of the optics is limited or even excluded, since the location of the position determination relative to the optical axis of the camera remains stationary. Since it is sufficient only part of the code for the

Deedieren decoding the location information, efficient or economical lighting can be provided which only illuminate the field of view of the camera or even only part of the face or Blickfekds the camera.

The corresponding method for measuring deformations of an elastically deformable object, in particular an elastic, elongate support structure is accordingly based on at least one optically detectable marking at a first longitudinal position along the elastically deformable object, as well as at least one electronic camera with an objective and a matrix. Sensor is used, wherein the lens of the camera is directed to the at least one optically detectable marker, such that the marker is imaged on the matrix sensor and the camera looks at the marker, wherein an image processing device, the image data are supplied to the camera, and wherein the image processing device performs an image recognition, so that the position of the marker within the image field is determined, and wherein by means of a computing device determines a deviation of the position of the marker of at least one desired value and based on the Pos the mark within the image field is quantified, the mark comprising a code in which a location information of the

Position of the code is coded, wherein the computing device decodes the code and thus determines the location of the field of view of the camera on the code

In addition to the location information, a synchronization pattern, such as a grid as an example, is preferably included. For such a code, it is sufficient, a very small code detail with a light source, such as a ^' collimated laser to illuminate and capture with a camera and then the intersection of the optical axis of the camera or a defined optical axis shifted point with the code and thus the shift to the grid origin, expressed in one discrete number of raster elements.

As location information in particular location coordinates are encoded in the code. These do not have to specify the location position in absolute units to a given reference point. Rather, a relative indication is sufficient. As a relative indication, therefore, in a very simple case, for example, a unique numbering of the code units, which may also be repeated cyclically, may suffice as location information. The number of each code unit then corresponds to a specific location on the object.

By translation and rotation of the surface to be examined, the captured image changes. In addition to a pure displacement distortions occur, which can be described by an affine transformation. The technical problem is inverse for this, from a measured image the translation and rotation parameters are calculated, i. the parameters of affine ones

Inverse transformation, which corresponds to a major axis transformation determined on an ideal grid.

The measuring accuracy is determined, among other things, by the precision of the raster detection. Particularly advantageous are therefore fast, preferably subpixel accurate Edge detectors as part of the image processing device.

The measurement of the change in position of the pattern with respect to the reference position can then be carried out as follows by the measuring device and its correspondingly configured image processing and computing device:

The contours are approximated by digital lines, points of intersection of the grid lines are determined. These intersections are stored in ordered order in a matrix matrix, whereby intersections connected by digital links are stored in identical rows or columns of the matrix, unoccupied points are marked as open (disabled). The

Principal axis transformation between a matrix 2 learned as a reference position (this does not necessarily have to be orthogonal) and the matrix 1 provides the required 6 transformation parameters, namely three translation parameters x, y, z and three rotation parameters α, β, γ. Particularly advantageous is the use of a CMOS sensor with integrated gradient filter and digital signal processor (DSP). With this hardware, a very fast and cost-optimized single-chip processing can be performed. This is the

Image processing device and the computing device at least partially or even completely integrated in the camera.

It is not necessary for the location information of the code to correspond in absolute terms to the location position. Relative information is also sufficient if one Calibration is performed. However, it is also advantageous if it is known at which intervals along the code the location information is stored. In this case, directly from the decoding of the location information, the absolute amount of the lateral shift of the mark caused by a deformation of the support structure can be obtained. If, for example, it is known that the location information is stored at specific intervals, for example of one centimeter, the displacement of the pattern relative to the reference position can be achieved by simple

Difference formation of the decoded location coordinates are obtained.

Particularly suitable is a two-dimensional code. With such a code can improve the

Measuring accuracy in a simple manner, several independent measuring fields can be realized by e.g. with a second camera another position is determined. It is also possible to mount the code on a non-planar surface and to scan two spaced-apart areas at an angle to one another. In such a code as a marker, location information for the locations is then coded along two non-parallel, preferably perpendicular directions. Accordingly, by decoding the code from the image information by means of the image processing device, a shift relative to a reference position along two non-parallel axes can be obtained.

Generally it is when using a code as

Mark appropriate, a route, or in the case of a two-dimensional code, an area with the marker to cover, which are so large that the shifts due to the elastic deformations to be measured within the distance, or area lie. In other words, even with the maximum detectable deformation, part of the code in the image field, particularly preferably also in the middle of the image, is visible.

The determination of translations and rotations of an object in three spatial directions by means of a code encoded on an object and coded therein

Location information is not limited to elastic deformations of objects. Rather, this embodiment of the invention is quite generally suitable for the detection and quantification of movements of objects in any direction.

According to a further aspect of the invention, therefore, a device for measuring a change in position, in particular translation and rotation of an object is provided, which comprises an optically detectable code with code units applied to the object, in which a location information, preferably in the form of absolute or relative location coordinates, is coded is. At least one camera with a matrix sensor is provided, with which the object or the code on the object can be detected. The measuring device in turn comprises an image processing and computing device. In the computing device, an assignment table is stored in which the geometric positions of at least some code units are stored at a reference position. The image processing device is, as described above, configured to recognize and decode the code, thereby associating the decoded location information with an image position. The computing device is set up to determine the transformation, preferably in the form of a principal axis transformation, which transfers the reference position according to the allocation table into the current position detected by the camera at which the code was decoded at the image position. These transformation parameters describe the change in position of the object.

A particularly suitable for the invention, two-dimensional code is described in EP 1333402 Al, which is made in terms of the design and expression of the code fully also the subject of the present invention.

Accordingly, in a development of the invention, the two-dimensional code has at least one, preferably all, of the following properties:

the code comprises a pattern containing a synchronization synchronization code and a position-dependent code, position data encoded in fixed-size code units,

the code comprises a pattern which comprises a synchronization code used for synchronization, this synchronization code being variable, being formed according to a previously known formation instruction and being distributed geometrically uniformly on the surface,

the code comprises a pattern comprising a synchronization synchronization code, which comprises two variable components each for synchronization along two non-parallel directions on the surface,

the code comprises a pattern which comprises a synchronization synchronization code which itself contains position-dependent data, preferably the least significant bit (s) of the coded position data,

the code comprises a pattern which comprises a synchronization code used for the synchronization, the synchronization code being distributed geometrically uniformly over the pattern,

the code comprises a pattern which contains a synchronization synchronization code which is at least twice the spatial frequency compared to the position-dependent code,

- Position data are encoded in units of fixed size, the location information is not completely present in a code unit, with a complete decoding of the location information by detecting a field at most six times the size of a code unit, preferably at most four times the size of a code unit is possible.

The code can be reduced according to a further development of the invention to code units having a size of at most 10 x 10, preferably at most 8 x 8, even of only 6 x 6 fields, each of the fields is a marker that a Represents bit. In general, the code units may be considered as laterally spaced marker marker elements as described above. The code described above is optimized in terms of its information density. The code can be stably read with a suitably adapted decoding method even with a small field of optional form.

In order to enable a measurement of elastic deformations, it is provided according to a further development of the invention that the code is arranged at least partially on a surface arranged obliquely to the viewing direction, wherein the marking is arranged with the code that of the camera or of several Cameras are simultaneously detected at different distances along the longitudinal direction of the support structure arranged code elements in which location information is encoded. Preferably, the code is applied to at least two mutually angled surfaces.

The opposite to the viewing direction of the camera obliquely arranged code can have a grid which is equidistant, or even projection corrected.

In order to determine a displacement of the surfaces provided with the code relative to a reference position and thus a deformation of the support structure, can in an advantageous

Way in the computing device, an assignment table of coordinates, preferably three-dimensional coordinates are stored to location information of the code. The allocation table can, as will be described in more detail below, inter alia, by projection of a

Grid on the areas provided with the code and a Comparison with the decoded location information are generated.

From the decoded position data can in a known arrangement of the code at the reference position by the

Computing a Hauptachsentransformation be calculated, with which transforms the mark from the reference position to the measured position. The change in position relative to the reference position can then be determined and quantified from this main axis transformation. This allows detection of both rotation and translation in three spatial directions.

In general, the invention can be used to provide the functionality of a support structure, such as a

Rotor blades of a wind turbine to monitor, control and / or regulate. This can also be done in a forward-looking or extrapolating manner by comparing movement patterns measured by the computing device with stored movement patterns. An example is a vibration with still allowed, but aufschaukelnder amplitude. For example, if such a movement pattern detected, can be counteracted early by a suitable control, such as by changing the angle of attack.

The invention will be explained in more detail by means of embodiments and with reference to the accompanying drawings. The same reference numbers refer to the same or corresponding elements. Show it :

Fig. 1 is a view of a rotor of a wind turbine with

Dividing a device for measuring elastic deformations of a rotor blade,

2 shows a cross section through a rotor blade,

3 shows a camera of the measuring device,

4 shows a video recording of the camera during a bending of the rotor blade,

5 shows a variant of the rotor of FIG. 1,

6 shows a video recording of the camera of the markings in the rotor blade of the example shown in FIG. 5,

7 is a diagram with deflection curves of the wing of the rotor,

8 shows an arrangement of the measuring device with a two-dimensional code as marking,

Fig. 9 shows an arrangement with a code with projection-corrected raster.

Fig. 1 shows a wind turbine rotor 1 according to the invention with three wings 5. Each of the wings 5 forms an elastically deformable support structure. The rotor accommodates parts of a device for measuring deformation of the wings, the principle of which is explained below. The Task of the measuring device is now to measure the deflection of the wing 5 of the wind turbine in two axes.

The device for measuring deformations is based on at least one optically detectable marking 7 at a first longitudinal position along the wing 5, and an electronic camera 9 with an objective 11 and a matrix sensor, wherein the lens 11 of the camera on the at least one optically detectable Marking is directed such that the mark 7 is imaged on the matrix sensor and the camera 9 in the longitudinal direction along the wing 5 looks at the mark 7, wherein the means for measuring deformations further comprises an image processing device which the image data of the camera and wherein the image processing device is set up to determine the position of the marking within the image field by means of an image recognition, wherein the device for measuring deformations additionally comprises a computing device which is set up, a deviation of the position of the marking from at least one nominal value determine and quantify.

The image processing device and the computing device are not explicitly shown in FIG. 1. However, these devices can also be integrated in the camera 9, so that the camera 9 at an output already outputs the data of the deviation from the target position, for example, the position of the stationary rotor in calm. In the embodiment shown in Fig. 1, the camera is installed in the hub 3 of the rotor 1. This is beneficial to avoid electronic elements in the rotor blades. The rotor hub can be compared to the wings 5 easier shielded from lightning, so that the camera is protected from a lightning due to failure.

If, due to the incoming wind, a deformation of the wing occurs during operation, the position of the marking 7 moves transversely with respect to the longitudinal axis of the wing, which also represents the viewing direction of the camera. Thus, the position of the image of the mark on the matrix sensor of the camera 9 shifts. If the distance of the camera 9 to the mark is known, the deformation at the location of the mark can be easily calculated from the displacement by means of the computing device.

The distance of the matrix sensor of the camera 9 to the marking is preferably at least 4 meters, particularly preferably at least 6 meters, between the matrix sensor and the marking in order to be able to measure a bending of the blade with high accuracy. On the other hand, it is generally favorable to choose the distance not greater than 40 meters, otherwise the wing 5 bends quickly so far in the occurring loads that the marker is no longer in the field of view of the camera, but hidden by the curved walls of the wing becomes.

Particularly preferably, a control device can generally be provided with which the deformations can be counteracted. The control device comprises For this purpose, an adjusting device with at least one actuator, which is counteracted in response to the fact that the calculator a deviation of the mark from a desired position, in particular the exceeding of a limit value, the elastic deformation is counteracted. In the case of the wind turbine rotor 1 shown in FIG. 1, an actuator for adjusting the angle of attack of the blades 5 is used, so that the adjusting device changes the angle of attack of the rotor blade as a function of the measured deformation.

Fig. 2 shows a cross section through the wing 5. Typically include wings of wind turbines, as well as other aerodynamic wings, in particular aircraft wings along their longitudinal direction extending cavities. In the example shown in FIG. 2, the wing 5 comprises an upper shell 51 and a lower shell 52, between which a spar 54 is arranged. Within the spar 54, a shaft-shaped cavity 56 extends. Also, the other intermediate spaces 55 and 57 may be hollow. It is now expedient that, as shown in FIG. 2, at least the marking 7 of the measuring device is arranged in the interior of the blade 5. By way of example, the marking in the spar 54 in the shaft-shaped cavity 56 is used in FIG. So that the camera 9 can detect the mark 7, an active illumination of the mark is provided.

3 shows an example of a suitable camera 9 in this example

Housing 91 of the camera 9 LEDs 92 is provided, which objects along the line of sight of the camera, in installed state so along the longitudinal direction of the wing 5 illuminate. In order to obtain a high contrast in the recorded images, it is then still favorable to form the marker as a reflector. For this purpose, a reflector foil or, as shown in FIG. 2, a marking 7 in the form of a cat's eye can be used.

FIG. 4 schematically shows a camera image 94 of the image sequence which is typically recorded continuously at the intended image repetition rate during operation. Recognizable in the camera image is the mark 7, which is shifted relative to the reference position 70. The camera 9 and the lighting is controlled or adjusted so that the light signal of the reflector controls the camera well, but preferably not overridden. There is a focal point determination of the reflector image. With the known properties of the lens of the camera, the deflection of the light spot relative to the reference position 70 in two directions is determined. In the case of a wing 5 represents the

Reference position preferably the position of the mark 7 in calm, in which no significant forces except the moments caused by the dead weight act on the wing.

5 shows a variant of the rotor 1 from FIG. 1. In this variant, two markings 7, 71 spaced apart from the camera 9 along the longitudinal direction of the blade are provided. Based on the position of these markers 7, 71, it is then also possible to determine and quantify an uneven deformation of the carrier structure. In addition, the markers 7, 71 may each comprise two or more marking elements spaced laterally from the viewing direction. Then, based on a rotation of the marking elements in the image plane, a torsion of the elastic, elongated support structure, or in the example of FIG. 5, a torsion of the wing 5 can be determined and quantified.

FIG. 6 shows an image from the video sequence recorded by the camera 9 of the rotor 1 shown in FIG. 5.

Each of the markers 7, 71 in the example illustrated in FIG. 6 comprises two laterally spaced marking elements. The marking elements 701, 702 of the marking 7 and the marking elements 704, 705 of the marking 71 are also arranged along mutually transverse, here in particular along mutually perpendicular lines. In order to distinguish the markings 7, 71 from one another, the marking elements have discrete properties, such as different color or shape. This is symbolized in Fig. 6 by the different filling of the here circular marking elements. An encoding of the various markings 7, 71 can also be advantageous by one or more wavelength-selective filters, such as in particular color filters on the markings. If different colors are reflected back or reflected back from the markings to the camera, the different markings with different wavelengths can be illuminated and selectively selected at different times in a further development of the invention be evaluated. This can be particularly advantageous if more than two markers are used and are to be discriminated.

It is favorable, as in the preceding examples, the markers 7, 71, or their marking elements 701, 702 and 7004, 705 form as reflectors, so that a high image contrast in the viewing direction paraxial illumination, for example by light-emitting diodes or one or more lasers to achieve.

The position of the markers 7, 71 is now derived from two reflector images. From the distance between the two reflector images can now also the mounting distance of

Reflectors, or the markers 7, 71 measured to the camera and so the measuring arrangement are calibrated, since the real distance of the marking elements belonging to a mark 7, 71, 702, or 704, 705 is known. Thus, it can be seen from the receptacle 94 that the distance of the marking elements 704, 705 is smaller than the distance of the marking elements 701, 702. The marking 71 is provided that the real distance is equal, thus further from the matrix sensor Camera removed.

Since the distance of the imaged marking elements changes with their distance, a determination of the distance can now also be used to detect and quantify a deformation in the longitudinal direction, in particular an elongation of the wing. At the wings large rotors can reach such strains certainly orders of magnitude in the meter range.

On the basis of each two arranged in a line marking elements is now the measurement of a

Rotation of the wing possible. If a torsion occurs between camera 9 and marking 7 and / or 71, the angle of the line connecting the two marking elements respectively belonging to a marking 7, 71 in the image plane changes.

According to one embodiment, the following parameters can be used for the measuring device:

The working distance, or the length of the optical path between sensor and marking is selected within a distance of about 40 meters. The measurement time is 16, 6 milliseconds corresponding to a refresh rate of 60 frames per second. Measurable are the large X-deflection, Y-deflection, rotation, distance of the marking, oscillation amplitude and oscillation frequency up to typically 20 Hertz. With a simple camera sensor, a measurement accuracy of 1/7000 of the maximum detectable displacement along the X-axis (the direction along the longer side of the image shown in Fig. 6) and 1/4000 of the maximum detectable displacement along the Y-axis can already be achieved become.

FIG. 7 shows an example of how, based on a comparison of the positions of the two markings, an uneven deformation of the carrier structure, in particular a non-uniform deflection of the vane 5, can be determined and quantified. In Fig. 7 diagrams of the deflection .DELTA.x of the wing as a function of the distance D to the hub are shown. The marker 7 is located at the position dl and the marker 71 at the position d2.

The solid curve shows an example of a normal, uniform deflection of an intact wing. If the wing has a kink, or for example also a crack, which leads to the weakening of the structure of the wing, there is an increased deflection behind the crack or kink. Such an exemplary deflection curve is shown in dashed lines. Accordingly, the ratio of the deflections .DELTA.x is greater here. Is based on the measurement data from the

Computing found that such an abnormal deflection is permanently present, or a permanent deviation from the bevy of deflection curves of an intact wing is present, for example, a shutdown of the wind turbine or the start of a safe state can be initiated. This safe state can be achieved for example by neutral position of the wings, the defective wing facing down.

By attaching two reflector pairs in the depth of the wing, the bend can be measured in two distances. This makes it possible to check whether the wing is evenly bent, or whether there is a kink, because the two points are no longer on the curve known from the structure curve. It is also possible according to a further embodiment of the invention, in addition to or alternatively to a position determination of marking elements, to provide a marking in the form of a code in which location information is coded. This offers, inter alia, the advantage that the deformation of a carrier structure can always be determined on the basis of the imaged and decoded information relating to the image center or any other reference point in the image plane. This eliminates measurement errors that can be caused by distortion of the lens.

Accordingly, the tag comprises a code in which location information of the local position of the code is coded, wherein the calculating means is adapted to decode the code and thus to determine the location of the field of view of the camera.

In the measuring device described with reference to FIGS. 1 to 7, a shift of the markings in all directions in the image plane, and therefore in two dimensions transversely to the viewing direction of the camera can be detected and quantified. If a code is used with location information, it is therefore advantageous to choose a corresponding two-dimensional code in which

Location information for the locations along two non-parallel, preferably vertical directions is encoded.

Hereinafter, a preferred code and its arrangement as marking in or on the support structure will be described in more detail. As in the embodiments described above, a camera 9 and one or more markings in the form of labein with the code are again arranged in a volume of the support structure.

The label or labels are arranged not only on a single planar surface, but on at least two mutually angled surfaces or surface elements, for example on a curved surface.

An exemplary arrangement with obliquely facing surfaces 76, 77, which is provided with a mark in the form of a two-dimensional code, is shown in FIG. 8

The grid can be equidistant or projection-corrected, so that the resolution and thus measurement accuracy for the directions considered is approximately constant.

9 shows a code with a projection-corrected raster. The raster width of the matrix or the raster of the code on the surface 76, which is essentially perpendicular to the viewing direction 95 of the camera 9, has a value a, while the raster width of the code is at an angle α to the viewing direction 95 the camera 9 standing surface 77 in the viewing direction by a value a / sin (α) is increased.

The individual grids 710 represent individual bits of the code. In order to recognize the fields and to be able to decode the code, the fields are formed differently contrasting depending on the bit value. For example Dark and light, or absorbing and reflecting fields can be used. The bit values are represented in FIG. 9 by different fillings of the grid fields. For example, the hatched fields may represent logical zeros and the non-hatched fields may represent logical ones or vice versa.

The code can - in contrast to a simple raster - ensure an absolute reference point. It is possible to endlessly print or otherwise produce a suitable code by distributing the information two-dimensionally in a particular manner so that the global positioning can be fully calculated from a maximum of 4 6x6 grid environments. Such a two-dimensional code as is preferred for the invention is known from EP 1333402 A1.

The arrangement of the code on a plurality of surfaces or surface elements that are at different distances from the camera, such as the exemplary arrangement of the surfaces 76, 77 is used according to the arrangement shown in Fig. 5 to detect a deformation along the line of sight. For this purpose, code units are decoded on a plurality of area elements arranged at different distances and their location information is evaluated. If there is a shift in the longitudinal direction, the location information at certain assigned image parts also change relative to one another. Instead of evaluating different image parts, it is also possible to use a plurality of cameras which detect different surface elements. As well as in Fig. 5 can also Codes are applied to a plurality of faces arranged one behind the other in the viewing direction of the camera, so that nonlinear deformations can be detected with several measuring points, and / or to increase the measuring accuracy.

A film (or similar structure) printed with such a code is now glued or otherwise secured to the object to be measured. Due to the special structure of the information arrangement phase and frequency of the local grid can be determined (similar to large 2D barcodes, FFT or chain processing). In this case, a code-internally used scrambling method can ensure a high local contour density.

After Find ^'of the raster by the image processing apparatus of the content code is binarized and entered into a matrix. From this, the global position can then be decoded in the (de facto infinite) grid. The method of decoding is also described in EP 1333402 A1, the content of which in this respect is also fully made the subject of the present application.

If the geometry of the surface is already known, defined points P ^ (x, y, z) of the grid can be assigned 3D coordinates.

One obtains a precisely assigned table of the form:

P _i (x, y, z) <-> angle _i (α, β, γ) This table can then be stored in the computing device for calculating the current position, or the deformation of the support structure.

The angles result from the central projection of the camera image through the aperture of the lens. Finally, from the set {P, angle}, the displacement of the labeled object relative to a reference position can be output by matching by determining the parameters of a main axis transformation. Measurable are the

Displacement vector (XO, YO, ZO) and the rotation in three angles (αθ, ßθ, γθ).

If the reference position is not known, for example if the exact shape to which the grid has been stuck, or the distance of the code to the camera is not determined, the following can be carried out according to an embodiment of the invention:

1. With a laser grating projector (e.g., a diffractive element laser), a point cloud or second grating is projected onto the screen from a known position (e.g., donated on the housing). For this purpose, it is expedient to use a complementary color, e.g. If the grid is printed in red, the laser creates its structure without contrast errors. The blue spectral range can then be used for the inspection. It will be apparent to those skilled in the art that there are many more possibilities for this.

2. The laser structure is measured, the control points are assigned. By simple triangulation (the distance Laser aperture to the lens aperture is known, the angles are known) calibrated 3D coordinates are determined on the grid.

3. Finally, the set of 3D points thus measured is assigned to the reference grid, and a set of 3D reference points is obtained on the grid. The laser can then be removed.

If a non-projection-corrected code is used, a calibration of both the distance, as well as the position of the surface can also be made on the basis of a comparison of the known grid width with the grid width detected in the camera.

The preferred code will be described in more detail below. The two-dimensional code has the following characteristics: the code comprises a synchronization code serving synchronization and a position-dependent code, the position data being encoded in code units of fixed size. The synchronization code is variable and geometrically evenly distributed on the surface. The synchronization code also allows the synchronization in the X and Y directions by means of two variable components. In particular, the

Synchronization code variable such that it contains even position-dependent data, preferably the one or more least significant bits of the coded position data. It is also possible to use the only slowly changing must-significant bit. In order to make the synchronization particularly reliable, the synchronization code can be compared with at least twice the spatial frequency to the position-dependent code. In order to obtain particularly small code units, it is then also possible not to completely encode the location information in a code unit. The complete location information can then be performed by detecting a field at most six times the size of a code unit, preferably at most four times the size of a code unit. In this case, the data can be divided so that missing bits of a position data from adjacent code units are added.

The above embodiments relate to the, or the wings of a wind turbine. The invention can also be used in a corresponding manner for aircraft wings. Here then it makes sense not to change the angle of attack of the wing depending on the deformation, as long as the wings are as usual in general, rigid. However, it is possible here to regulate the buoyancy by means of one or more rudders and flaps, such as the ailerons and spoilers or flaps.

Since the deformation of the wing is typically preceded by a change in attitude of the aircraft, among other things, the attitude can be stabilized by a control device which controls the flaps and / or rudders by means of the measurement of the deflection and / or twisting of the wing.

A measuring device according to the invention can also advantageously be provided in the aircraft fuselage in order to be able to detect loads on the carrier structure here. It will be apparent to those skilled in the art that the invention is not limited to the embodiments described above, but can be varied in many ways. In particular, the invention can also be applied to other support structures and elastically deformable objects.

Reference sign list:

1 wind turbine rotor

3 hub of 1

5 wings of 1

7, 71 marking

9 camera

11 lens of 9

51 upper shell of 5

52 lower shell of 5

54 Holm

55, 57 spaces between 51, 52

56 shaft-shaped cavity in 54

76, 77 Areas provided with a two-dimensional code

91 case of 9

92 LEDs

95 Viewing direction of 9

701, 702,

704, 705 Marking Elements

710 grid

Claims

Claims:

1. A device for measuring deformations of an elastically deformable object, preferably an elongated support structure comprising at least one optically detectable mark at a first longitudinal position along the elastically deformable object, and at least one electronic camera with a lens and a matrix sensor, wherein the lens the camera is directed to the at least one optically detectable marker such that the marker is imaged onto the matrix sensor and the camera faces the marker, the deformation measuring device further comprising an image processing device which captures the image data of the camera and wherein the image processing device is set up to determine the position of the marking within the image field on the basis of an image recognition, wherein the device for measuring deformations additionally comprises a computing device that is set up, a deviation determining and quantifying the position of the mark of at least one target value, the mark comprising a code in which location information of the position of the code is coded, the calculating means being arranged to decode the code and thus the location of the field of view of the code Determine the camera.

2. Device according to the preceding claim, wherein the camera at a second longitudinal position spaced from the first longitudinal position in the longitudinal direction is arranged.

3. Device according to one of the preceding claims, characterized in that the marking is arranged within a cavity of the elastically deformable object and is illuminated by means of a lighting device.

4. Device according to one of the preceding claims, characterized by at least two along the

Marked longitudinally at different distances from the camera markings, wherein the computing device is set up to determine and quantify a change in length or an uneven deformation of the elastically deformable object based on a comparison of the positions of the two markings.

5. Device according to the preceding claim, characterized in that the code comprises a two-dimensional code in which location information for the locations is coded along two non-parallel, preferably vertical directions.

6. Device according to one of the preceding claims, characterized in that the code comprises at least one, preferably all of the following characteristics: the code comprises a pattern which contains a synchronization synchronization code and a position-dependent code,

Position data are encoded in units of fixed size, the code comprises a pattern which comprises a synchronization code used for synchronization, this synchronization code being variable, being formed according to a previously known formation instruction and being distributed geometrically uniformly on the surface,

the code comprises a pattern comprising a synchronization synchronization code comprising two variable components each for synchronization along two non-parallel directions on the surface,

the code comprises a pattern comprising a synchronization synchronization code, the synchronization code being distributed uniformly geometrically across the pattern, the code comprising a pattern comprising one of

Synchronization serving synchronization code, which is present at least twice the spatial frequency compared to the position-dependent code,

7. Device according to one of the two preceding claims, characterized in that the code is arranged at least partially on a surface arranged obliquely to the viewing direction, wherein the mark is arranged with the code so that from the camera or from several cameras simultaneously at different distances along a direction of the elastically deformable object arranged code elements in which location information is encoded, are detected.

8. Device according to one of the three preceding claims, characterized in that in the computing device, an assignment table of coordinates, preferably three-dimensional coordinates is stored to location information of the code.

9. Device according to one of the four preceding claims, characterized in that the computing device is adapted to calculate from decoded position data, a main axis transformation, with which the marker from the reference position transformed into the measured position and based on

Main axis transformation to determine the position change relative to the reference position and quantify.

10. Device according to one of the preceding claims, characterized by a laser for illuminating the marking, wherein the laser is aligned parallel to the viewing direction of the camera on the marking.

11. Device according to one of the preceding claims, characterized in that the length of the optical path between the matrix sensor and the marking is at least 4 meters, preferably at least 6 meters.

12. A control device with a device for measuring deformations according to one of the preceding claims, wherein the control device comprises an actuating device with at least one actuator, with which in response to the fact that was calculated by the computing means a deviation of the mark from a desired position, the elastic deformation counteracted.

13. aerodynamic wing, characterized by a device for measuring deformations according to one of the preceding claims.

14. Wind turbine rotor with an aerodynamic wing according to the preceding claim.

15. Wind turbine rotor according to the preceding claim, characterized in that the camera is arranged in the rotor hub.

16. Wind turbine rotor according to the preceding claim, characterized by a control device according to claim 13, wherein the actuator comprises an actuator for adjusting the angle of attack, and wherein the

Adjusting device the angle of attack of the rotor blade changes.

17. A method for measuring deformations of an elastically deformable object, in particular an elastic, elongated support structure, wherein at least one optically detectable mark at a first longitudinal position along the elastically deformable object, and at least one electronic camera with an objective and a matrix sensor is used wherein the lens of the camera is directed to the at least one optically detectable marker, such that the marker is imaged onto the matrix sensor and the camera faces the marker, the image data being supplied to an image processing device of the camera, and wherein the image processing device performs an image recognition, so that the position of the marker within the image field is determined, and wherein by means of a computing device detects a deviation of the position of the marker of at least one target value and based on the position of the marker within the Bildfel ds, wherein the marker comprises a code in which location information of the position of the code is encoded, wherein the computing device decodes the code and thus determines the location of the field of view of the camera on the code.

18. The method according to the preceding claim, characterized in that the deformation of an aerodynamic wing is detected and quantified and by means of at least one actuator depending on the deformation of the angle of attack of the wing or the Buoyancy is changed.

19. The method according to one of the two preceding claims, characterized in that a marking is used with at least two laterally spaced from the viewing direction marking elements, wherein based on a rotation of the Markieruήgselemente in the image plane, a torsion of the elastic, elongated support structure is determined and quantified.

20. Method according to one of the three preceding claims, characterized in that the length of the optical path from the matrix sensor to the marking is determined by a transit time measurement of a light beam or by the size of a pattern projected onto the marking.

21. Method according to one of the four preceding claims, in which a measurement of the vibration of the elastically deformable object is carried out, wherein an image sequence is recorded and determined on the basis of the individual images determined course of the change in position of the marking of at least one of the parameters amplitude and frequency of the vibration by means of Calculation device is determined.

22. The method according to any one of the five preceding claims, characterized gekennzeichn that measured movement patterns are compared by the computing device with stored movement patterns.