MEASURING SYSTEM FOR MEASURING A SURFACE OF A ROTOR BLADE OF A WIND TURBINE

Abstract

A measurement system and a measurement method for measuring a surface of a rotor blade of a wind power installation as a measured object. The measurement system comprises: a carrier unit having a plurality of measurement sensors arranged in a measurement plane, wherein the measurement system is configured to align the measurement plane with a profile section of the measured object, a movement unit which is configured to move the carrier unit relative to the measured object in a longitudinal direction that is at an angle to the measurement plane, and an advancing unit which is configured to advance at least one measurement sensor in the measurement plane relative to the profile section. The measurement system and the measurement method facilitate an accurate measurement of the surface of the measured object with reduced outlay.

Claims

1-21. (canceled)

22. A measurement system for measuring a surface of a rotor blade of a wind power installation as a measured object, comprising: a carrier unit having a plurality of measurement sensors arranged in a measurement plane, wherein the measurement system is configured to align the measurement plane with a profile section of the measured object, a movement unit configured to move the carrier unit relative to the measured object in a longitudinal direction that is at an angle to the measurement plane, and an advancing unit configured to advance at least one measurement sensor of the plurality of measurement sensors in the measurement plane relative to the profile section, wherein the plurality of measurement sensors are configured as laser section sensors, and wherein the advancing unit is configured to advance to a distance between the at least one measurement sensor and the measured object in such a way that a requirement with respect to a measurement resolution of the at least one measurement sensor with respect to the surface of the measured object is satisfied both in a hub region of the rotor blade and in a blade-tip region.

23. The measurement system as claimed in claim 22, wherein the advancing unit has a mechanical advancing element configured to mechanically advance the at least one measurement sensor.

24. The measurement system as claimed in claim 22, wherein the advancing unit has a linear advancing element, and wherein an axis of the linear advancing element extends in the measurement plane.

25. The measurement system as claimed in claim 22, wherein the plurality of measurement sensors are each configured to capture part of the profile section of the measured object in the measurement plane, and further comprising a calculation unit configured to combine the captured parts of the profile section to form an overall profile section.

26. The measurement system as claimed in claim 25, wherein the calculation unit is configured to combine profile sections at different positions of the carrier unit in the longitudinal direction to form a profile of the surface of the measured object.

27. The measurement system as claimed in claim 25, wherein the calculation unit is configured to compare the captured profile section or the captured profile to a reference profile section or a reference profile, and wherein the calculation unit is configured to determine if a deviation between the reference profile section or the reference profile and the captured profile section or profile exceeds a predetermined tolerance value.

28. The measurement system as claimed in claim 27, wherein the calculation unit is further configured to undertake a correction of the captured profile section or of the captured profile on the basis of an inherent weight of the measured object and gravity.

29. The measurement system as claimed in claim 22, wherein the carrier unit is embodied as a portal, wherein the plurality of measurement sensors are directed in a direction of an interior of the portal.

30. The measurement system as claimed in claim 22, wherein the carrier unit is configured to be arranged within the profile section of the measured object, wherein the plurality of measurement sensors are directed away from the carrier unit to the outside of the measurement system.

31. The measurement system as claimed in claim 22, wherein the movement unit has a guide component and a motor, wherein the guide component defines the longitudinal direction and the movement unit is configured to move the carrier unit along the guide component by the motor.

32. The measurement system as claimed in claim 22, further comprising a position determination unit configured to determine the position of the carrier unit along the longitudinal direction.

33. The measurement system as claimed in claim 32, wherein the carrier unit has a retroreflector and wherein the position determination unit is configured to determine the position of the carrier unit by the retroreflector.

34. A measurement method for measuring a surface of an object, the method comprising: aligning a carrier unit with a plurality of measurement sensors, arranged in a measurement plane, with a profile section of the object, wherein the plurality of measurement sensors are configured as laser section sensors, moving the carrier unit in a longitudinal direction, at an angle to the measurement plane, relative to the object, and advancing at least one of the measurement sensors of the plurality of measurement sensors in the measurement plane relative to the profile section in such a way that the distance between the at least one measurement sensor and the object satisfies a requirement with respect to a measurement resolution of the at least one measurement sensor with respect to the surface of the object.

35. The measurement method as claimed in claim 34, wherein, in each case, at least one profile section of the object is captured before and after moving the carrier unit and advancing at least one of the measurement sensors.

36. The measurement method as claimed in claim 35, wherein a position of the carrier unit in the longitudinal direction is captured for each profile section.

37. The measurement method as claimed in claim 36, wherein at least one profile section is corrected depending on its position in the longitudinal direction.

38. The measurement method as claimed in claim 37, wherein a surface profile of the object is calculated from the captured profile sections.

39. The measurement method as claimed in claim 34, wherein the object is a rotor blade of a wind power installation.

40. A method comprising: using the measurement system as claimed in claim 1 to initially measure a surface of the measured object at a first resolution, comparing the measured surface of the object at the first resolution to a reference surface; and when a deviation of the comparison exceeds a threshold value, using the measurement system to measure the surface of the measured object at a second, higher resolution.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0059] FIG. 1 schematically shows an exemplary embodiment of a measurement system,

[0060] FIG. 2 schematically shows the functional principle of a laser section sensor,

[0061] FIGS. 3a and 3b schematically show a calibration of measurement sensors in an exemplary manner,

[0062] FIGS. 4a and 4b schematically show a position determination unit of the measurement system according to the invention in an exemplary manner,

[0063] FIG. 5 schematically shows how an example of a measured object, specifically a rotor blade of a wind power installation, is mounted in an exemplary manner and

[0064] FIGS. 6a to 6c schematically show further exemplary embodiments of a measurement system in an exemplary manner.

DESCRIPTION OF THE RELATED ART

[0065] FIG. 1 schematically shows an exemplary embodiment of a measurement system 1 according to the invention. The measurement system 1 comprises a carrier unit 3, which is configured in the form of a frame, and a movement unit 5, by means of which the frame 3 can be moved. In this example, the frame extends along a width x and along a height y and it is movable by means of the movement unit 5 in a longitudinal direction z, which is perpendicular to both the width x and the height y. In this exemplary embodiment, the width x and the height y define the measurement plane of the measurement system. The selection of the axes is exemplary and may be different in other exemplary embodiments. Even though width x, height y and length z are respectively perpendicular to one another in this example, this may also be different in other exemplary embodiments.

[0066] In this example, the movement unit 5 is an electric motor which moves the measurement system 1 along the longitudinal direction z by way of a rail (not shown) on the floor, on which the frame 3 is placed, for example by means of wheels.

[0067] In this example, seven measurement sensors 30 are provided within the frame 3. The measurement sensors 30 are each directed inwardly in the measurement plane from the frame 3, onto the region in which a measured object should be inserted. In this example, two measurement sensors 30, namely the measurement sensors arranged at the upper end of the frame 3, are fastened to the frame 3 by means of an advancing unit 40. The advancing unit 40 allows the measurement sensor 30, which is fastened to the frame 3 by the advancing unit 40, to be able to be moved in the measurement plane. In this example, the advancing unit 40 comprises two parallel linear advancing elements 42, which are arranged at vertical portions of the frame 3 and which mount a horizontal carrier such that it is movable in the height direction y between the two linear advancing elements 42. In other exemplary embodiments, only one measurement sensor 30, or more than two of the measurement sensors 30, are fastened to the frame 3 by means of the advancing unit 40, preferably all of the measurement sensors 30, in particular. Each of the measurement sensors 30 may have a dedicated advancing unit 40 or a plurality of the measurement sensors 30 can be advanced using a common advancing unit 40.

[0068] FIG. 2 schematically shows the functional principle of a laser section sensor as an example of a measurement sensor 30. The measurement sensor 30 is a laser light section sensor which comprises a laser light source 32, a cylindrical lens 34, a lens 37 and detector, e.g., a camera 39. The punctiform light emitted by the laser light source 32 is split into a line by means of the cylindrical lens 34. The line emerges from the measurement sensor 30 and strikes a surface of a measured object 2. The incident laser light 36 is reflected at the surface 2 and enters into the camera 39 as a reflected line 38 via the lens 37. The height profile of the surface 2 can be calculated by the offset of the laser line incident on the camera 39. Laser light section sensors are based on the known principle of laser triangulation, with the punctiform light source being expanded into a two-dimensional line. The laser light section sensor 30 is only an example of a surface sensor that can be used in the measurement system 1 according to the invention.

[0069] FIGS. 3a and 3b schematically show a calibration of the measurement sensors 30 in an exemplary manner. FIG. 3a illustrates the beam profile 301 to 307 of the seven measurement sensors 30 shown in FIG. 1. The beam profile first extends linearly and is then split in a fan-like manner by a cylindrical lens 34, as shown in FIG. 2. The beam profiles 301 to 307 strike the surface 2 of the measured object 2 at different positions and at different angles, using the example here of a profile of a rotor blade of a wind power installation.

[0070] The individual beam profiles 301 to 307 partly superimpose significantly; this is used for calibration and reliability, as elucidated in FIG. 3b. FIG. 3b shows a part of a profile section that is obtained by the division of the measurement sensors 30 shown in FIG. 3a. FIG. 3b only shows the parts of the profile section that are captured by three measurement sensors 30. Other measurement values of the respective adjacent sensors would also be visible in the edge region of FIG. 3b if all seven measurement sensors 30 were taken into account.

[0071] It is clear from FIG. 3b that the parts of the profile sections that originate from the respective beam profiles 302, 303 and 304 overlap in the shown portion of the profile curve. In the example shown in FIG. 3b, the profiles are such that at least two of the sensors overlap at all times and that even all three sensors overlap in the central region. As a result of the calibration of the measurement sensors 30, a profile section which is presented as a single line is produced. Expressed differently, the calibrated sensors 30 supply measurement values that fit to one another, from which an overall profile section can be calculated. FIG. 3b shows a defect 60, at which the rotor blade deviates from a usual profile. No deviation of the measurement line 303 from the measurement line 304 can be seen at the position 60 either, i.e., the defect 60 has been determined in agreement by the measurement sensor 30, from which the beam profile 303 originates, and the measurement sensor 30, from which the beam profile 304 originates.

[0072] The overlap of the individual measurement lines 302, 303 and 304 can be adapted, if necessary, in a further step in the aftermath of the measurement. By way of example, the lines can be smoothed by a suitable method, in particular by B-splines or the like. Additionally, a suitable method for producing a smooth surface can be used in the aftermath when producing a 3D (three-dimensional) surface from two-dimensional profile sections. By way of example, a NURBS surface can be fitted into the point cloud of the entire measured object. Hence, a smooth, simulation-capable surface is produced.

[0073] FIG. 4a schematically shows, in an exemplary manner, a position determination unit 50 which is used in a measurement system 1. In FIG. 4a, the sensors 30 are shown schematically by the laser light source 32 and the cylindrical lens 34, which are arranged on a schematic frame 3 sketched out in the form of a semicircle. Further elements of the measurement sensors 30 have been omitted for improved illustration. Further, FIG. 4a shows a rotor blade as an example of a measured object 2, which is moved along the frame 3 in the longitudinal direction z.

[0074] The position determination unit 50 has a position laser 52 and a retroreflector 54. The position laser 52 is stationary and arranged independently of the frame 3. It does not move when the frame 3 is moved by means of the movement unit 5. The position laser 52 measures the distance from the retroreflector 54, which moves with the frame 3. The retroreflector 54 reflects the radiation incident from the position laser 52 back to the position laser 52 in a way that is largely independent of the alignment of the retroreflector 54 in respect of the position laser 52. The retroreflector 54 is guided continuously on a circular or elliptical orbit. The circular or elliptical orbit of the retroreflector 54 can be effected in respect of an attachment surface, which is fastened to the frame 3, or in respect of the entire frame 3. By virtue of the frame 3 moving in the longitudinal direction Z and the retroreflector 54 simultaneously being situated on a circular or elliptical orbit, a helical trajectory emerges, from which the position and orientation of the frame 3 of the measurement system 1 can be determined at all times.

[0075] FIG. 4b schematically shows, in an exemplary manner, the measurement system 1 shown in FIG. 1 together with the measured object 2, the blade tip of a rotor blade in this example. The frame 3 is guided along the rotor blade 2, with the measurement sensors 30 capturing profile sections of the rotor blade 2 continuously or at certain intervals. Instead of the rotating retroreflector 54, a stationary retroreflector 54 is shown in the example shown in FIG. 4b. In this example, too, the retroreflector 54 can be used to determine the distance from the position laser 52 (not shown in FIG. 4b).

[0076] The measurement system 1 is suitable for capturing a three-dimensional surface geometry of a measured object 2 in an automated manner. Particularly for large dimensions of the measured object 2 and the high measurement resolution that is required for a meaningful determination of the surface geometry of the measured object 2, the measurement is not implemented from a stationary location of the measurement system 1, but instead from different positions by virtue of the frame 3 being moved by means of the movement unit 5 along the measured object 2 and the measurement sensors 30 consequently carrying out a relative movement with respect to the measured object 2 during the measurement process. A carrier unit, for example in the form of a frame 3 with a plurality of measurement sensors 30 which are, for example, optical triangulation sensors such as laser light section sensors, is guided on a rail system, for example, along the measured object 2 and precisely tracked with the aid of a position determination unit 50. By way of example, the position determination unit 50 is a position laser 52, which determines the distance to a retroreflector 54 attached to the frame 3. Thus, a sequence of complete profile sections of the measured object 2 arises. Individual measurements of profile sections can be fusioned to form a three-dimensional overall model with a high resolution. Here, too, autonomous or preprogrammed floor conveyors could be used as movement units 5 for moving a carrier unit 3. Additionally, the portal could be fastened in a freely manipulable manner to an industrial robot in order to be able to describe any spatial curve as a travel along a measured object.

[0077] The advancing component 40, which is configured to set the distance of the measurement sensors 30 from the measured object 2, ensures that the measurement resolution of the surface of the measured object 2 is sufficiently high, independently of the diameter of the measured object 2 at the position at which the current profile section is measured. Deviations of the three-dimensional overall model can be determined by a comparison with a CAD model, for example.

[0078] Significant sagging caused by gravity, occurring, in particular, in the case of long measured objects 2 such as rotor blades of a wind power installation is simulated and taken into account in the evaluation. The measurement data captured by the measurement system 1 form the basis for flow simulation for evaluating the power of the rotor blade or evaluating the rotor blade acoustically, for example, in the case of rotor blades of a wind power installation.

[0079] What the measurement system 1 can achieve is that the overall measurement time for a rotor blade is no longer than 30 minutes. Within this time, a profile section can be recorded every 2 millimeters in the longitudinal direction of the measured object 7 using the measurement system 1. Using the measurement system, the local measurement inaccuracy at the profile leading and trailing edge can lie in the region from 0.05 to 0.17 mm on the pressure side and from 0.07 to 0.41 mm on the suction side. Within these tolerance ranges, there can be a guarantee for power values or acoustic values of the rotor blade.

[0080] FIG. 5 shows a side view of an example of a measured object 2, specifically a rotor blade of a wind power installation. The rotor blade 2 is fastened in a stationary holder 22 at its hub end. In order to reduce sagging of the rotor blade, the rotor blade 2 is supported by at least one support apparatus 24. In this example, the support apparatus 24 is spaced apart from the blade tip by approximately one third of the blade length. In other examples, the support apparatus 24 can also be provided at other points of the blade and use can also be made of more than one support apparatus 24 for supporting the rotor blade 2.

[0081] On account of the support apparatus 24, it is not possible to displace a closed portal along the entire rotor blade 2. FIGS. 6a to 6c show three exemplary embodiments of a carrier unit 300, 400 and 500 which can be moved along the entire rotor blade 2, despite the provided support apparatus 24.

[0082] FIG. 6a shows a carrier unit 300, which is embodied in the form of an inverted U. In this example, the movement unit of the carrier unit 300 comprises two wheels 310, which are each provided at a lower end of the vertical frame elements. FIG. 6a shows two measurement sensors 330, which are arranged at opposite sides of the rotor blade 2. The measurement sensor 330 lying on the side shown on the right in the drawing is displaceable along a direction 345 in the measurement plane by means of an advancing unit 340. In an example, the measurement sensor 330 can also be rotatably mounted in relation to the advancing unit 340 and consequently be advanced in relation to two axes. In this example, the advancing unit 340 is further shown halfway up the rotor blade 2; in other examples, the displacement unit 340 can also be arranged at other positions with respect to the rotor blade or it can be assembled to be adjustable with respect to the carrier unit 300.

[0083] FIG. 6b shows a further exemplary embodiment of a carrier unit 400. The carrier unit 400 is composed from two frame elements 405, which are respectively arranged on a pressure side and a suction side of the rotor blade 2. The two sides 405 are not connected to one another and are displaceable relative to one another in a direction 420. To this end, the respective frame elements 405 have wheels 410. FIG. 6b also shows two measurement sensors 430. One of the measurement sensors 430, which is shown to the right in the drawing, is arranged to be pivotable in a direction 445 with respect to the carrier unit 400 at a pivot 442 via a displacement unit 440. In order to pass the position of the rotor blade 2 at which the support apparatus 24 is arranged, the two frame elements 405 are moved apart. As a result, the pivotable sensor 430 on the right-hand side is not situated below the rotor blade 2. After passing, the sensor can be positioned, again, below the rotor blade 2 in the vicinity of the leading edge of the rotor blade 2. Consequently, it is possible to ensure a high resolution the leading-edge region, which is a very sensitive region in respect of the aerodynamics. While the frame elements 405 in this example can be moved apart from one another and the advancing unit 440 facilitates a rotatable advance of the measurement sensor 430, the frame is either constructed from two frame elements 405 or one of the measurement sensors can be advanced in a rotatable manner in other examples. Combinations with other exemplary embodiments also are advantageously possible.

[0084] FIG. 6c schematically shows a further exemplary embodiment of a carrier unit 500. The carrier unit 500 stands on the ground on the right-hand side in the drawing by means of a stand element 510. By way of example, the stand element 510 may also comprise wheels. In this exemplary embodiment, too, only two measurement sensors 530 are shown schematically, of which the one shown to the right in the drawing can be advanced along an advanced direction 545 by means of an advancing element 540. After passing the support element 24, the sensor 530 shown on the right-hand side in the drawing can consequently be positioned below and in the vicinity of the leading edge of the rotor blade 2, without impairing the displacement of the carrier unit 500 along the measured object.

[0085] In other exemplary embodiments, the carrier unit 3, 300, 400, 500 may also comprise the advancing element in integrated fashion. As a result, measurement sensors, for example, can be advanced in the measurement plane by advancing part of the entire frame, etc., of the carrier unit 3, 300, 400, 500. Although the shown exemplary embodiments elucidate a rotor blade 2 of a wind power installation as an example of a measured object, the effects and advantages obtained by the invention are also applicable to other measured objects, in particular elongate measured objects with a varying cross section.