NO347715B1

NO347715B1 - System and method for repair and maintenance of wind turbine blade

Info

Publication number: NO347715B1
Application number: NO20210867A
Authority: NO
Inventors: Vincent Gorbani
Original assignee: Altokinetics As
Priority date: 2021-07-05
Filing date: 2021-07-05
Publication date: 2024-03-04
Also published as: WO2023282761A1; NO20210867A1

Description

SYSTEM AND METHOD FOR REPAIR AND MAINTENANCE OF WIND TURBINE BLADE.

Technical Field

The present invention relates to a tool for use in repair and maintenance operation in the renewable industry. Particularly, the invention relates to an inspection, repair and maintenance device for use on areas on a wind turbine. This may for instance be a blade maintenance device for a wind turbine that is capable of performing multiple repair and maintenance tasks such as cleaning, inspection, leading edge repair, de-icing of a blade while travelling and flying along on all side of the blade.

Background Art

There is a growing need for renewable energy sources both to meet the demand of increased energy in the world and to meet the requirements of reducing the emission of greenhouse gases.

One of the renewable energy source in this transition is the energy produced by wind power. Using wind turbine, the wind energy is converted to mechanical energy (kinetic energy) to produce electricity. This method of energy production has come into the spotlight as a great source of clean energy for reducing greenhouse gas.

As the wind power industry grows, the demand for more lean and smarter method of repair and maintenance of the blades of the wind is needed.

Current methods of blade repair are very costly, time consuming and dangerous with the carrying fatality.

To reduce the levelized Cost of Energy (LCOS) in the wind power field, it is necessary to reduce the operation and maintenance cost (O&M) so that wind industry can grow and become more sustainable. A typical amount of cost for O&M today is approximately 45000$.

Drones, such as unmanned aerial vehicles (UAVs) have been used in the industry for various purposes. Recent legislation allows domestic use of drones in particular inspection operation in accordance with FAA regulations (Luftfartstilsynet).

A wind turbine arrangement comprising a tower, a nacelle mounted on an upper part of the tower, and a rotor connected to the nacelle. The rotor has a number of blades that provide the rotation and thus the mechanical source of energy and having a number of blades.

During the lifecycle, the wind turbine arrangement needs intervallic inspection and maintenance, such as cleaning, damage repair, erosion repair, dewatering repair, de-icing, etc.

All of these abovementioned activities are required even after installation so as to avert issues or an accident and to improve operation efficiency.

However, due to structural largeness of the wind turbine with a tower height of the plus 100 meter and the blade length in the size of 40 to 110 meter there are many complications in performing repair and maintenance. Since the blade is placed at a high altitude, a working environment is dangerous and not suitable, as a worker or climber needs to stay in the mid-air for the operation.

Because of mentioned poor condition of blade maintenance in this method, a device that is capable of performing examination and repair/maintenance without the direct access of workers/climbers to the blade has been suggested.

D1 discloses a method for performing maintenance operations using unmanned vehicle where the tool is moved continuously or intermittently across a wind turbine blade while maintaining contact with the surface of the wind turbine blade undergoing maintenance.

The present invention generally relates to automated system for carrying repair and maintenance tool(s) across limited access surface of wind turbine blade, such as repair and maintenance vehicle including (but not limited to) distance sensory system, holding fixation assembly system, robotic arm system, umbilical and tether assembly and separate tool for robotic arm activities such as cleaning tool, grinding tool, calking tool and pressure gauge tool. In particular this disclosure relates to apparatus for performing repair operation on a leading edge of wind turbine blades.

The tool and method according to the invention is beneficial in that it provides

- a reduction in overall maintenance time,

- 50% less mobilization time

- 40% less repair and maintenance time

- Fatality risk free

- No climbers needed

- Safe and free from human error

- 40% less down time on the wind turbine

- Unique technology

Further and other aspects of the invention will come apparent throughout the disclosure of the invention.

Summary of invention

The invention relates to an unmanned repair aerial vehicle tool for a wind turbine blade comprising a unmanned aerial vehicle adapted to be positioned along the wind turbine blade. The tool is distinctive in that the tool further comprises

-a holding fixation assembly system comprising at least one suction cup and an actuator connecting at least one suction cup to the unmanned aerial vehicle for positioning and connecting the tool to a wind turbine blade prior to a repair and maintenance operation and

-a robotic arm attached to the unmanned aerial device to perform repair and maintenance at a defined position on the wind turbine blade.

The holding fixation system has preferably two suction cups, one at each side of the holding fixation system. The suction cups are further arranged so that they may be positioned one at each side surface of the wind turbine blade when attached to the blade.

The invention further relates to a method for performing a repair operation of a wind turbine blade using the unmanned repair aerial vehicle tool connected to the lead edge of a wind turbine blade according to any of the claims 1-8, where the repair operation comprises sequential steps actuated by the robotic arm -washing the area by a cleaning tool,

-grinding the area by a grinding tool,

-clean the area by a cloths tool

-coating the area by a caulking tool,

-measure the hardness of the coating layer by a measurement gauge tool.

The invention also relates to a maintenance assembly for a windmill blade. The maintenance device comprising a maintenance tool according to any of the claims 1-8, a generator arranged at a ground surface or a vessel and a cable and tether system connecting the generator and the maintenance device.

Further or other aspect of the invention is set out by the dependent claims, to which reference are made.

An example of the present application may disclose

an Unmanned Repair Aerial Vehicle (URAV) that may perform: examination with a capability direct image processing (AI system with Machine learning capability), and performs: repair/ maintenance of blade which including a cleaning, leading edge grinding and vacuuming all the grinded residue, post grinding cleaning, applying protective coating and measuring the hardness of the coating afterwards, all these activities will be done with the robotic arm which is attached to the underside of the drone body and the activities are performed while unmanned repair aerial vehicle tool travel along the blades.

Human based climber repair and maintenance of wind turbine structure can be time consuming, expensive and risky. To perform these operations with the traditional method can be very costly for the field operators, each repair operation for one wind turbine blade can lead to minimum of 3 days shut-down for each wind turbine.

The unmanned repair aerial vehicle tool comprises an unmanned aerial vehicle, such as s drone with the motorized back side for movement in two axis of x and Y. The unmanned repair aerial vehicle tool further comprises a robotic arm connected to the unmanned aerial vehicle, the robotic arm has the ability to move in a multiple of axis, for instance 7. The unmanned repair aerial vehicle tool also comprises a holding fixation assembly with one or more suction cups.

The one or more suction cups may be connected to adjustable actuators for stability during its operation.

The maintenance tools, such as the two types of grinding tool a belt grinder and flat disc grinder, automatic caulking gun for coating and surface pressure gauge may be components or tools that are a part of the maintenance or repair system. The tools are activated with electricity through a battery pack for short time operation or a direct umbilical cable connection with a power source on the ground or on a vessel for offshore operation.

The front facing the wind turbine blade of the unmanned repair aerial vehicle tool may further be equipped with soft rolling foam bumper and a distance sensor.

The operation sequence of the unmanned repair aerial vehicle tool is by steering the tool and flying this to the location which needed to be fixed.

Connect the by the holding fixation assembly, which may include

-activate the actuators and get the suction cup connected to the blade,

-check the distance and connect the soft rolling foam bumper arrangement toward the blade,

-activate the robotic arm and perform the various maintenance operations.

The maintenance operation may include:

-clean the area, after cleaning change the tool and grab the grinding tool (the one fit for purpose). Grind the area with vacuum system on, then change the tool to cleaning and remove any leftover residues. After cleaning, change the tool with caulking gun and apply coating for the area needed. Wait 5 minute and then change the tool to surface pressure gauge to check the coating hardness, then release the pressure for the suction cup and move to the next fixing location.

This repair and maintenance operation on the blades can be done on any angles and there is no hindrance or limitation for our device.

Brief description of drawing

Figure 1 depicts a wind turbine blade that requires maintenance,

Figure 2 depicts the wind turbine blade in its full length and the tool according to the invention arranged on the blade edge,

Figure 3a and 3b depicts a perspective view of an embodiment of the unmanned repair aerial vehicle tool according to the invention, view from above and below,

Figure 4 depicts a top view of the unmanned aerial vehicle according to the invention, in isolation,

Figure 5 depicts an isometric view of a robotic arm according to an embodiment of the invention, in isolation,

Figure 6a depicts an enlarged front view of the unmanned repair aerial vehicle tool according to an embodiment of the invention,

Fig. 6b depicts an enlarged side view of the unmanned repair aerial vehicle tool according to an embodiment of the invention, side viewed,

Fig. 6c depicts an embodiment of the unmanned repair aerial vehicle tool, viewed from above,

Figure 7 depicts a perspective view of the unmanned repair aerial vehicle tool during operation on a wind turbine blade.

Figure 8 depicts a flight System Layout Configuration according to an embodiment of the invention.

Detailed description of the invention

Figure 1 illustrates a part of a windmill or wind turbine blade 1 in detailed view. The illustration shows an example of wear on the edge 1a of the blade, which needs to be repaired.

Figure 2 shows the wind turbine blade 1 in its full length with an unmanned repair aerial vehicle tool 10 according to the invention arranged on the leading blade edge 1a.

The figure further shows a cable and tether system 4 providing power and connection to a ground 2 for the unmanned repair aerial vehicle tool 10.

The cable and tether system 4 comprise a cable 3 and a generator 5.

The figure 2 further shows the ground, here illustrated by a vessel 2 arranged beneath the wind turbine blade 1. The cable 3 is extending between the unmanned repair aerial vehicle tool 10 and generator 5. The generator 5 may be arranged on the ground or vessel 2 as illustrated in the figure.

The power goes from the generator 5, through the cable 3 to the unmanned repair aerial vehicle tool 10.

The cable and tether system 4 may further comprise a winch machine (not shown) for reeling in and out the cable 3. The winch machine is preferable arranged on the ground or vessel 2 for the ease of operation.

The cable 3 may as an embodiment of the invention be covered with Chinese finger grip. The Chinese finger grip may further be made of stainless steel. This would prevent slipping or cutting the cable.

The unmanned repair aerial vehicle tool 10 may also in addition be powered by a battery pack 19 (fig.7) integrated with the unmanned repair aerial vehicle tool 10. The battery pack 19 may then be arranged beneath a top cover of a chassis in the unmanned repair aerial vehicle tool 10. The battery pack 19 may supply voltages for a short operation or emergency operation of the unmanned repair aerial vehicle tool 10. If the main power supply, like the generator 5 fails, the battery pack 19 may supply power to the unmanned aerial vehicle tool 10.

Figure 3a and 3b shows the unmanned repair aerial vehicle tool 10 according to an embodiment of the invention in greater detail.

The unmanned repair aerial vehicle tool 10 comprises an unmanned aerial device 11, a robotic arm 15 and a holding fixation assembly system 20.

The parts are connected together to form an integrated unit as shown in the figure.

The individual parts of the unmanned repair aerial vehicle tool 10 will be described related to the following figures 4-7.

Figure 4 shows a basis chassis of the unmanned aerial device 11 illustrated from above. The figure illustrates a possible design of the unmanned aerial device 11.

The unmanned aerial device 11 may be a drone 11, but larger unmanned aerial vehicles may also be possible. This may as an illustrating example be a Y6 copter (tri-copter) drone with 6 motors and a duct 13 for each two motors.

The propeller duct 13 has preferable a size to fit a propeller 14 The propeller duct 13 may further have a gap of a few millimeter adapted to be fitted for coaxial motors 42a, 42b, 42c.

As illustrated in the figure, the unmanned aerial device 11 may have a chassis 12 having 3 chassis arms 12a extending in three distinctive directions. The chassis 12 may be built in a lightweight material, such as carbon fibre.

At the free end of each of the chassis arm 12a is a arranged a propeller duct 13 with one or more propeller blades 14. In the example embodiment shown in the figure, each propeller duct 13 comprises two distinctive propeller blades 14. Each of the propeller blades 14 may be driven by a motor 42a, 42b, 42c.

Further, each motor 42a, 42b, 42c may have an individual control unit, such as Electronic Speed Controller (ESC) 41. All of the motors are operationally connected in a flight controller module 40.

The unmanned repair aerial vehicle tool 10 is operated through the flight control module 40. The flight control module 40 is more specifically the main component for operating the unmanned aerial device 11 to position the unmanned repair aerial vehicle tool 10 at the wind turbine blade edge 1a in order to perform the inspection and maintenance operation.

As indicated in the figure, the unmanned aerial device 11 may be rotated both in an Y axis and in an X axis to facilitate an exact position of the unmanned repair aerial vehicle tool 10 according to the invention. This is performed by motors in the duct 13 adapted to be situated at an opposite of the side facing the wind turbine blade 1 when connected to this.

The flight controller module 40 will be further illustrated and described in relation to figure 8.

Figure 5 shows a perspective view of an embodiment of the robotic arm 15 according to the invention. The robotic arm 15 comprises a base part 16, a movable articulated part 17 and a claw 18.

The robotic arm 15 may for instance have 7 possible axial movements and is capable to change maintenance tools at the claw/hand 18.

The movable articulated part 17 may further comprise a number of hingedly connected parts 17a-17g. The number of hinged connections in the figure 5 is 7. However, this is only an illustrating example and other numbers of hinged connections may be possible. In figure 5, there is a first part 17a rotationally connected to the base part 16. The first part 17a is adapted to rotate 360° around a vertical axis extending through the center axis of the base part 16. A second part 17b may further be fixedly or rotatably connected to the first part 17a. In the embodiment illustrated in the figure, this is fixedly attached to the first part 17a. Further a third part 17c is rotationally connected to the second part 17b through a horizontal axis. Further, a fourth part 17d is rotationally connected to the third part 17c through a horizontal axis. Both the third and fourth part 17c, 17d are adapted to be rotated up and down 330°.

A fifth part 17e is rotationally connected to the fourth part 17d. This part 17e is in the figure illustrated to rotate around its own axis 360 degree.

Further, a sixth part 17f is rotationally connected to the fifth part 17e and is further adapted to rotate 360° around its own axis.

A seventh part 17g is rotationally connected to the sixth part. This part 17g is adapted to rotate up and down 330°.

The claw 18 is rotationally connected to the seventh part 17g. The claw 18 is adapted to rotate 360° around a vertical axis extending at the center or the seventh part 17g.

As pointed out above, the number or part of the robotic arm 15 and the rotation with respect to each other is only illustrated as an example in the figure. Other number of parts and connections are possible embodiments of the invention as long as the robotic arm 15 provides a degree of motion for the claw 18 in order to perform the different maintenance or repair operations.

The robotic arm 15 is connected to the unmanned aerial device 11 through the base part 16 (see fig.7).

The robotic arm 15 is mounted to the unmanned aerial device 11. The connection may be rails arranged on the base part 16 and the chassis 12, respectively, for sliding movement front and back of the robotic arm 15 (not shown). The base part 16 of the robotic arm 15 may be designed to have 360° rotation and rolling mechanism for the rails. The rolling mechanism may further be equipped with motors (not shown) for pushing/pulling and locking the robotic arm 15 to the unmanned aerial vehicle 11. The base part 16 may be attached to the underside of the drone frame chassis 12 for easy connection and disconnection. The robotic arm 15 may also have a direct connection to the power source and the separate control unites.

The robotic arm 15 in the illustrating example may be capable to reach and repair 2,4 m of area at each position. Other areas may however be possible with other embodiments of the robotic arm 15.

The control mechanism 40 of the unmanned repair aerial vehicle tool 10 may preferably function so that the when the unmanned repair aerial vehicle tool 10 is positioned and docketed at the surface of the wind turbine blade 1, the robotic arm 15 becomes active. The robotic arm 15 may then perform the maintenance and repair operation. This will be further described in relation to the functioning of the tool.

Figure 6a-6c shows an embodiment of the holding fixation assembly system 20 arranged on the unmanned repair aerial vehicle tool 10 in greater detail, viewed from different angles.

The holding fixation system 20 comprises one or more suction cups 21. The one or more suction cups 21 are adapted to be placed on the surface of the wind turbine blade 1 and connect the unmanned repair aerial vehicle tool 10 to the wind turbine blade 1.

As an illustrating example, the figure shows that the unmanned holding fixation system 20 have two suction cups 21.

The one or more suction cups 21 may further be equipped with a vacuum system (not shown) to facilitate the connection between the unmanned repair aerial vehicle tool 10 and the wind turbine blade surface 1. This may be an inbuild vacuum system and emergency release system in case of over pressure from the unmanned aerial vehicle 11 and uncontrolled movement or pulling.

The one or more suction cups 21 is be connected to the unmanned aerial vehicle 11 through an actuator 22. There may be arranged an actuator 22 to each of the suction cups 21. The actuator(s) 22 facilitate the positioning of the suction cup(s) 21 at a suitable position for connection to the wind turbine blade 1.

The actuators 22 may be connected to the chassis 12 through an end connection point and elevation device.

The unmanned repair aerial vehicle tool 10 may further comprise a soft rolling foam bumper arrangement 23. The soft rolling foam bumper arrangement 23 is arranged at the side of the tool 10 intended to face the windmill plate 1a when the unmanned repair aerial vehicle tool 10 is connected to the wind turbine blade 1. This provides a protection and damper between the wind turbine blade 1 and the unmanned repair aerial vehicle tool 10.

The soft foam bumper arrangement 23 may comprise one or more soft rolling foam pads 23a that is adapted to rotate freely around a center axis as indicated in the figure 6a and 6c. A support bar 23b may be connected between two of the chassis arms 12a or the two front ducts 13. The soft rolling foam pads 23a may be mounted onto support bar 23b. The foam pads 23a may be installed through the central hole onto the front support bar 23b. The material for the foam pads 23a may for instance be a foam polyurethane or similar.

The soft foam bumper arrangement 23 may contact an outer side of the blade 1 during repair operation and makes a rolling movement.

The unmanned repair aerial vehicle tool 10 may also be equipped with one or more distance sensor(s) 24. The distance sensor(s) 24 may be arranged on the unmanned repair aerial vehicle tool 10 in a position so that it is able to measure the surface of the wind turbine blade 1. The distance sensor(s) 24 is adapted to be used when moving the unmanned repair aerial vehicle tool 10 towards the wind turbine blade 1 and further to position the unmanned repair aerial vehicle tool 10 at the surface of the blade 1.

The distance sensor(s) 24 of the unmanned repair aerial vehicle tool 10 may comprise a distance sensor that detects a positioning of the unmanned repair aerial vehicle tool 10 towards the blade 1 prior to connect or docking itself with the holding fixation system 20 to the blade 1. The sensor(s) 24 send signal to the flight controller 48 for exact and smooth docking connection on to the blade 1.

The holding fixation system 20 may further comprising a vertical leveling movement system and a horizontal leveling movement system for each actuator 22 in order to position the suction cup 21 in a suitable position for connection with the blade 1.

The function of the holding fixation system 20 is to hold unmanned repair aerial vehicle tool 10 in a fixed position during repair process and minimize the uncontrolled movement for the unmanned aerial vehicle 11 and the robotic arm 15.

Figure 7 shows the embodiment of the unmanned repair aerial vehicle tool 10 from the figures 1-6c in a position attached to the wind turbine blade 1, viewed from below.

As illustrated in the figure, the suction cups 21 are adapted to be attached to the surface of the wind turbine blade 1. The soft rolling foam bumper arrangement 23 is further bearing against the wind turbine blade edge 1a.

The robotic arm 15 is further arranged at the underside of the unmanned aerial vehicle 11. The unmanned repair aerial vehicle tool 10 may optionally also comprise other maintenance tools, such as a flat disc grinding tool and Belt grinding tool 6, a caulking tool 7 and a cleaning tool 8. These tools may be arranged on the unmanned repair aerial vehicle tool 10 in respective holders as indicated in the figure. These tools 6, 7, 8 are arranged so that they are able to perform maintenance operations on the blade by the robotic arm 15.

The tools are arranged in near proximity to the claw 18 of the robotic arm 15 so that the claw 18 is able to pick up the intended tool 6, 7, 8 to perform the maintenance and repair operation.

The unmanned repair aerial vehicle tool 10 may further have a camera 9 arranged to perform a visible observation of the maintenance/repair operation. The camera 9 may be part of an inspection unit arranged at the front of the unmanned repair aerial vehicle tool 10 facing the blade 1, when installed. The camera 9 is adapted to inspect defects of the blade 1 and inspect the final results of the repair operation. The inspection unit may further have a second camera (not shown) installed at the back side of the unmanned repair aerial vehicle tool 10 with the view toward the blade 1 during repair operation. The inspection unit may also comprise a third inspection camera (not shown) on the robotic arm 15 having a central view of the operation.

The figure further shows the cable or umbilical cable 3 and the connection to the unmanned repair aerial vehicle tool 10.

Fig 8 shows a schematic view of the flight controller module 40. As indicated by the figure the flight controller module 40 comprises a number of electronic speed controller 41. The electronic speed controllers 41 are independently controlling a set of motors 42a, 42b, 42c that are used in the movement of the unmanned repair aerial vehicle 10 towards the wind turbine blade 1. The set of motors may also comprise an X-movement motor 42b, and a Y-movement motor 42c especially designed to move the tool in the X and Y axial direction of the back propellers. This is part of the X and Y leveling movement system as referred to above. The X and Y motor may preferably be positioned at the back or rear side of the unmanned repair aerial vehicle tool 10 as indicated in the figures 4 and 7. This means the side facing away from the soft rolling foam bumper arrangement 23.

The flight controller module 40 may further be equipped with GPS/ Gyroscope 45, Camera sensor 47, Distance sensor 47, Antenna and Receiver 46. All of these instruments facilitates the movement and positioning of the tool 10 towards the wind turbine blade 1. In addition, there is a power monitoring unit or power source 44 and/or a power distribution unit 43 for powering the unmanned repair aerial vehicle tool 10.

The “brain” of the flight controller module 40 is a flight controller 48 and is arranged in a center position of the flight control module 40 to be in operationally connection with each of the other equipment 41, 42a-c, 43, 44, 45, 46, 47.

The flight controller module 40 as shown in the figure comprises: the ESC control for each propeller motors and movement control for X and Y motors are manage through the flight controller. A flight controller regulates the level of electricity through the power hub for each ESC. A GPS / Gyroscope informs the flight controller for correct positioning of the drone. The camera and sensory system are setup as a subsystem for the distance positioning during operation.

The functionality of the unmanned repair aerial vehicle tool 10 according to the invention will be described in the following.

The unmanned repair aerial vehicle tool 10 is firstly moved by the unmanned aerial vehicle 11 to be positioned near the edge 1a of the wind turbine blade 1.

A holding and fixation process is then started with a vertical levelling system to align the unmanned repair aerial vehicle tool 10 in the vertical direction. The actuators are further erected above 45° (minimum 45°) and then a horizontal levelling system is activated for the gap distance between the two actuators (based on wind turbine blade). When the actuator position is ideal, activate the actuators piston to push out the rod connected to the suction cups 21. When the suction cups 21 are in contact with the surface of the wind turbine blade 1, the vacuum system of each suction cup 21 become operational and connect the unmanned repair aerial vehicle tool 10 to the wind turbine blade 1.

Each of the actuator(s) 22 is capable of multiple directional movement for creating best fixation position for the suction cup 21. This smart system is to make the best triangular fixation position for the unmanned repair aerial vehicle tool 10 during the repair operation. The formation of the actuators 22 installed is to contact the blade sides 1, a short distance from the leading edge 1a or other repair areas.

When the unmanned repair aerial vehicle tool 10 is docketed to the wind turbine blade 1 and fixed by the holding fixation assembly system 20, the robotic arm 15 become active.

The unmanned repair aerial vehicle tool 10 is now in position for the maintenance operation.

In general, the robotic arm 15 is adapted to time pick up a maintenance tool, such as the grinding tool 6, caulking tool 7, cleaning tool 8 etc and used this in the various maintenance process.

An example of a maintenance operation step may comprise:

Step 1: connect the claw/hand 18 to the cleaning tool 8 and wash the dirt and derbies of the area (if needed).

After cleaning, the maintenance area is dried and the cleaning tool 8 is secured back into its holder at the underside of the unmanned repair aerial vehicle tool 10. The claw/hand 18 is further disconnected from the cleaning tool 8.

Step 2: Connect the claw/hand 18 to the grinding tool 6 and start the grinding of the area. The vacuum system may suck in all the grinded parts into a bag which is position at the underside of the unmanned repair aerial vehicle tool 10 after grinding. The grinding tool 6 is then secured back into its holder at the underside of the unmanned repair aerial vehicle tool 10 and disconnected from the claw/hand 18.

Step 3: Connect the claw/hand 18 to the cloths tool (not shown) and clean the surface of the wind turbine blade 1 after cleaning. Secure the cloths tool back into its holder at the underside of unmanned repair aerial vehicle tool 10 and disconnected from the claw/hand 18.

Step 4: Connect the claw/hand 18 to the caulking tool 7 for applying surface coating on the leading edge 1a of the wind turbine blade 1. The caulking tool 8 comprises mixing gun, automatic edge forming mechanism and patrons. After coating, the caulking tool 8 is secured back into its holder at the underside of unmanned repair aerial vehicle tool 10 and disconnected from the claw 18.

Step 5: Take a measurement gauge tool (not shown) with the claw/hand 18 after 5 minutes and measure the hardness of the new coating layer. Register the results and after use, secure the measurement gauge tool back into its holder at the underside of the unmanned repair aerial vehicle tool 10 and disconnect from the claw/hand 18

Step 6: Deactivate the robotic arm 15 and release the holding fixation system 20 by depressurize the suction cups 21 and retract the actuator 22. Move the unmanned repair vehicle tool 10 to the next location of the wind turbine blade and repeat the steps of the repair process at the new location.

Figure list

1 wind turbine blade

1a wind turbine blade leading edge

2 vessel

3 cable, such as umbilical cable

4 cable and tether system

5 generator

10 unmanned repair aerial vehicle tool 11 unmanned aerial vehicle

12 chassis

12a chassis arm

13 propeller duct

14 propeller blade

15 robotic arm

16 base part

17a-17g parts of the robotic arm

18 claw

19 battery pack

20- holding fixation assembly

21 Suction cup

22 Actuator

23 Soft rolling foam bumper arrangement 23a soft rolling foam pads

24 Distance sensor

6 Flat disc grinding tool or belt grinding tool 7 Caulking tool

8 Cleaning tool

9 Camera

40 flight controller module

41 Electronic speed controller 42a X- movement motor

42b motor

42c Y movement motor

43 Power hub

44 Power source

45 GPS/Gyroscope

46 antenna receiver

47 Camera sensor, distance sensor 48 Flight controller

Claims

1. An unmanned repair aerial vehicle tool (10) for a wind turbine blade comprising an unmanned aerial vehicle (11) adapted to be positioned along the wind turbine blade (1), characterized in that the tool further comprises

- a holding fixation assembly system (20) comprising at least one suction cup (21) and an actuator (22) connected to the unmanned aerial vehicle (11) for positioning and connecting the tool (10) to a wind turbine blade (1) prior to a repair and maintenance operation and

- a robotic arm (15) attached to the unmanned aerial device (11) to perform repair and maintenance at a defined position on the wind turbine blade (1),

the holding fixation assembly system (20) further comprises a vertical and horizontal levelling system in operable connection with the actuator (22).

2. The unmanned repair aerial vehicle tool (10) according to claim 1, wherein the unmanned repair aerial vehicle tool (10) comprises a soft rolling foam bumper arrangement (23) arranged at a side facing a blade edge (1a) when connected to the blade (1).

3. The unmanned repair aerial vehicle tool (10) according to any of the claims 1-2, wherein the unmanned repair aerial vehicle tool (10) further comprises at least one distance sensor (24) for detecting and positioning the maintenance tool with respect to the blade (1) prior to connection to the blade (1).

4. The unmanned repair aerial vehicle tool (10) according to any of the claims 1-3, wherein the robotic arm (15) is connected to the underside of the unmanned repair aerial vehicle tool (10), said robotic arm (15) is adapted to receive tools (6, 7, 8), such as a grinding tool (6), a caulking tool (7) or a cleaning tool (8).

5. The unmanned repair aerial vehicle tool (10) according to any of the claims 1-5, wherein the unmanned repair aerial vehicle tool (10) further comprises an inspection unit having an inspection camera adapted to inspect the blade (1) during operation and post repair operation.

6. The unmanned repair aerial vehicle tool (10) according to any of the claims 1-5, wherein the unmanned repair aerial vehicle tool further comprises a flight controller module (40) adapted to control the movement and maintenance operation of the unmanned repair aerial vehicle tool (10).

7. The unmanned repair aerial vehicle tool (10) according to any of the claims 1-6, wherein the unmanned repair aerial vehicle tool (10) further comprises a battery pack (19) integrated in the unmanned repair aerial vehicle tool (10).

8. Method for performing a repair operation or maintenance of a wind turbine blade using the unmanned repair aerial vehicle tool (10) connected to the lead edge (1a) of a wind turbine blade (1) according to any of the claims 1-7, where the repair or maintenance operation comprises a repair or maintenance step performed by a tool (8, 6, 7) actuated by the robotic arm (15), such as

- washing the area by a cleaning tool (8),

- grinding the area by a grinding tool (6),

- clean the area by a cloths tool,

- coating the area by a caulking tool (7),

- measure the hardness of the coating layer by a measurement gauge tool.

9. A maintenance assembly for a windmill blade (1) characterised in that the assembly comprising the unmanned repair aerial vehicle tool (10) according to any one of the claims 1-7, a generator (5) arranged at a ground surface or a vessel (2) and a cable and tether system (4) connecting the generator (5) and the unmanned repair aerial vehicle tool (10).