Method for optically detecting a wind turbine for testing purposes using an aircraft

Abstract

A method for optically acquiring a wind turbine for monitoring purposes with the aid of an aircraft, in particular a manned or unmanned rotorcraft, which has at least one camera installed thereon, wherein the wind turbine comprises a plurality of rotor blades, the surface of which is scanned within the scope of the method.

Claims

1. A method for optically acquiring a wind turbine for monitoring purposes with the aid of an aircraft which has at least one camera installed thereon, wherein the wind turbine comprises a plurality of rotor blades, the surface of which is scanned within the scope of the method, wherein the scanning is carried out optically, comprising the following method steps: aligning a first rotor blade in a vertical position, subsequently flying over and scanning a first side of the first rotor blade in the vertical direction, subsequently flying over and scanning a second side of the first rotor blade in the vertical direction, subsequently aligning a second rotor blade in a vertical position, subsequently flying over and scanning a first side of the second rotor blade in the vertical direction, subsequently flying over and scanning a second side of the second rotor blade in the vertical direction, wherein a control command is generated in an automated manner after flying over the second side of the first rotor blade, on the basis of which control command the alignment of the second rotor blade into the vertical position is initiated.

2. The method as claimed in claim 1, wherein a rotor blade axis of the rotor blade to be scanned is aligned pointing vertically upward during the scanning.

3. The method as claimed in claim 1, wherein the rotor blade to be scanned is aligned in such a way that a compression side and at tension side of the rotor blade lie substantially parallel to a plane which is spanned by the tower a rotary axis of the wind turbine.

4. The method as claimed in claim 1, wherein the regions to be detected on the rotor surface are scanned at least twice, wherein the camera or cameras and/or the aircraft are arranged at different positions in relation to the rotor blade at each one of the two scans.

5. The method as claimed in claim 1, wherein the flying over the side of the rotor blades during the scanning is initially carried out in one vertical direction and subsequently carried out in the opposite vertical direction.

6. The method as claimed in claim 1, wherein a multiplicity of partial recordings of the rotor blade are generated, said partial recordings being combined to an overall recording.

7. The method as claimed in claim 1, wherein a distance between the wind turbine or the rotor blade and the aircraft is monitored in an automated manner.

Description

(1) The invention will be explained in more detail below on the basis of the figures, in which

(2) FIG. 1 shows a wind turbine which is flown over and detected in a thermographic manner by a helicopter;

(3) FIG. 2 schematically shows the flight trajectory of the helicopter during the flying-over procedure;

(4) FIG. 3 schematically shows the thermal image of a rotor blade acquired optically, a) with an artifact caused by helicopter, b) without an artifact caused by helicopter;

(5) FIG. 4 schematically shows the alignment of the helicopter while flying over the rotor blade from above.

(6) FIG. 1 shows a known wind turbine 1 with a tower 4 and a nacelle 3. A plurality of rotor blades 2, of which only two can be identified, are fastened to a hub 13. Usually, three rotor blades are present. The rotor, which comprises the rotor blades 2 and the hub 13, rotates about the rotor axis A, which is aligned substantially horizontally and which can be rotated about a vertical axis, which is defined by the tower 4, depending on the position of the nacelle. The rotor blades 2, in turn, can be twisted in relation to the hub 13 about the rotor blade axis B. For inspection purposes, a first rotor blade 2.sub.1 is now aligned vertically such that the rotor blade axis B thereof points vertically upward. Now, a helicopter 9, on which a thermal imaging camera is installed, flies over both the compression side 5 and the tension side 6 of the rotor blade 2 in succession. Here, flying over in a vertically downward direction and flying over in a vertically upward direction are provided in each case.

(7) More details in respect of the flight trajectory emerge from FIG. 2. It is possible to identify the rotor blade 2 with the tension side 5 thereof. Initially, the helicopter 9 positions itself at a position approximately level with the blade tip and then it flies vertically downward in the direction of the hub in a manner approximately parallel to the rotor blade axis B. Then, it displaces its position in the x-direction such that the rotor blade can be observed from the helicopter from a slightly different angular position. Then, the helicopter flies vertically upward again. During the process of flying over, the camera records a multiplicity of thermal images. Subsequently, the helicopter 9 switches the side of the rotor blade and flies from the tension side to the compression side 5. There, it likewise initially flies over the rotor blade from top to bottom in the vertical direction, subsequently changing the longitudinal position x and flying to the top again. Once it has reached the top again, it can assume a type of parked position; the higher, the better. Then, a signal is transmitted to a control unit of the wind turbine, for example by way of radio waves or SMS, with the request now to bring the next rotor blade into the position pointing vertically upward. Then, the next rotor blade is acquired and flown over in the manner described above, until all rotor blades have been flown over and optically acquired.

(8) FIG. 3 shows the thermal image of a rotor blade 2, which is composed from a multiplicity of individual recordings 11 by stitching, carried out either by hand or in an automated manner. However, the recordings according to FIG. 3a were recorded from a different lateral position than the recording according to FIG. 3b. Thus, a first thermal image artifact 10.sub.1 can be identified in FIG. 3a, which artifact can also be identified in the recording according to FIG. 3b. The first thermal image artifacts 10.sub.1 are respectively arranged at the same positions in both images, despite a deviating recording position. In this respect, the assumption can be made that these thermal image artifacts 10.sub.1 indicate cracks in the shown rotor blade 2. Furthermore, it is also possible to identify support structures 12, both in the illustration according to FIG. 3a and in the illustration according to FIG. 3b. Furthermore, a second thermal image artifact 10.sub.2 can be identified in FIG. 3a. However, it cannot be identified in the illustration according to FIG. 3b. Since it cannot be identified in the second illustration, it consequently does not indicate damage. It turns out that this is the thermal image of an exhaust gas flow of the helicopter.

(9) FIG. 4 shows the alignment of the helicopter 9 while flying over the rotor blade in different longitudinal positions. Initially, the helicopter 9.sub.1 flies over the rotor blade 2 (depicted in a simplified manner in a horizontal cross section not true to scale) in such a way that a recording angle ?.sub.1 of approximately 100? emerges. At the second time, the helicopter 9.sub.2 flies over the rotor blade 2 in such a way that a recording angle ?.sub.2 of approximately 80? emerges.

(10) A distance x between the helicopter 9 and the rotor blade 2 is established continuously by means of a laser rangefinder not depicted in any more detail here. If the helicopter should come too close to the rotor blade, a safety warning which warns the pilot about a possible collision is output (e.g. acoustically or optically). If the distance x becomes too big, this can reduce the significance of the generated images. This is also signaled to the pilot by means of a warning signal.

REFERENCE SIGNS

(11) 1 Wind turbine 2 Rotor blade 3 Nacelle 4 Tower 5 Tension side 6 Compression side 7 Front edge 8 Rear edge 9 Helicopter 10 Artifact 11 Individual recording 12 Support structure 13 Hub A Rotor axis B Rotor blade axis ? Recording angle x Horizontal distance