WO2021121522A1

WO2021121522A1 - Automated device and method for repairing leading edge damage on wind turbine blade

Info

Publication number: WO2021121522A1
Application number: PCT/DK2020/050392
Authority: WO
Inventors: Ivar J.B.K. JENSEN; Aksel PETERSEN; Asger Bloksma KROGSTRUP
Original assignee: Vestas Wind Systems A/S
Priority date: 2019-12-18
Filing date: 2020-12-18
Publication date: 2021-06-24

Abstract

A robotic maintenance device and method for automatically repairing damage around the leading edge of a wind turbine are provided. The maintenance device is configured to scan the wind turbine blade with a vision system and then selectively use one or more tool heads to conduct the repair of any damage around the leading edge of the blade. The tool heads can include a cleaning/abrading tool head to sand down and clean the surface around the damage and a coating applicator tool head to apply layers of coating to repair the damage. The maintenance device includes a drive having a plurality of clamping actuators, each pair of which is designed to be moved along a stroke direction into and out of clamped engagement with the blade and along a longitudinal direction to allow for movement of the maintenance device along the blade.

Description

AUTOMATED DEVICE AND METHOD FOR REPAIRING LEADING EDGE DAMAGE

ON WIND TURBINE BLADE

Technical Field

This application relates generally to wind turbines, and more particularly, relates to an automated robotic device and method for repairing damage along the leading edge of a wind turbine blade without necessitating removal of the blade from the tower of the wind turbine and without necessitating manual repairs by rope access technicians.

Background

Wind turbines are used to produce electrical energy using a renewable resource and without combusting a fossil fuel. Generally, a wind turbine converts kinetic energy from the wind into electrical power. A conventional wind turbine installation includes a foundation, a tower supported by the foundation, and an energy generating unit positioned atop of the tower. The energy generating unit typically includes one or more nacelles to house several mechanical and electrical components, such as a generator, gearbox, and main bearing, and the wind turbine also includes a rotor operatively coupled to the components in the nacelle through a main shaft extending from the nacelle. Single rotor wind turbines and multi-rotor wind turbines (which may have multiple nacelles) are known, but for the sake of efficiency, the following description refers primarily to single rotor designs. The rotor, in turn, includes a central hub and a plurality of blades extending radially therefrom and configured to interact with the wind to cause rotation of the rotor. The rotor is supported on the main shaft, which is either directly or indirectly operatively coupled with the generator which is housed inside the nacelle. Consequently, as wind forces the blades to rotate, electrical energy is produced by the generator. Wind power has seen significant growth over the last few decades, with many wind turbine installations being located both on land and offshore.

As noted above, blades interact with the wind to generate mechanical rotation of the rotor, which can then be converted into electrical energy. A wind turbine blade is a complex structure that must be constructed to withstand long-term service in an abusive environment, while also maximizing lift and minimizing drag forces. The blades move at varying speeds through the ambient environment surrounding the wind turbine, but often this movement is at high speed. Consequently, the blades will typically experience erosion and damage over time in operation as a result of friction from the air as well as potential impacts from particulate matter, debris, or other items in the air, especially along the leading edge facing the direction of movement through the wind. The erosion or damage along the leading edge of the blade adversely affects the aerodynamic qualities of the blade over time, resulting in lower power production for given incoming wind speeds. Such erosion and damage on the blades can be corrected by routine maintenance and repair procedures.

The blades are typically formed from a shell of layered fiber composite, aluminum, or similar material with an outer skin defined by a series of layers of coatings (polymeric elastomers, paint, etc.) surrounding and covering an outer surface of the shell. The shell encloses internal components of the blade and isolates them from the environment, including shear webs and spar caps, for example. The outer skin may be defined by several different layers of material, including at least an outermost topcoat, a second layer underneath the outermost topcoat, and a third layer underneath the second layer. Other layers are typically present underneath the third layer as well, including base materials typically made from fibre composites and the like. The topcoat, second layer, and third layer may be formed from different colors of material so as to more easily reveal how deep an erosion or damaged portion goes into the outer skin of the blade. Damage to the blade outer skin can be categorized into several different levels of severity based on which layer the damage extends to, e.g., an erosion to the third layer would be a "category 2" level of severity, which would be higher than a cut to the second layer, which would be a "category 1" level of severity. For low levels of damage or erosion, such damage can be repaired by depositing a coating onto the area to fill in the damage and restore the blade to the original condition along the leading edge thereof. One such repair by depositing material can be reviewed in PCT International Patent Publication No. WO201 8/113875, owned by the original Applicant of the present application. However, merely depositing material over a damaged or eroded portion of a wind turbine blade can potentially lead to variations from the original airfoil shape and can change the aerodynamic properties and performance of the wind turbine blade, in use.

Although the '875 Publication referenced above provides one automated device for maintenance and repair, these types of repairs of the wind turbine blades have typically been conducted in three other manners conventionally. First, the blade can be disassembled from the remainder of the wind turbine and lowered to the ground for the repair to be completed. Such a repair process is time-consuming and costly as a result of needing to disassemble, move, and reassemble the blade relative to the top of the tower. Second, a human operator with rope access can rappel along the wind turbine blade while still attached to the rotor hub to evaluate and make repairs as needed to the blade. Once again, such a repair process is time-consuming and costly because of the need for experienced rope access technicians and the time needed to effect the repairs manually. Third, a repair action can be taken by an operator on a platform hoisted into position adjacent the blade on the wind turbine, either extending from the nacelle or hub of the wind turbine or extending from a cherry picker or boom-style lift. In all conventional methods, the wind turbine must be stopped and locked for the time period of repair, and as such, significant power production losses are experienced by wind turbine operators for these necessary maintenance and repair actions. This may lead some operators to delay or procrastinate in making such repairs, which can lead to more significant structural damage and even longer delays when more thorough repairs are necessary on the wind turbine blade.

In recent years, a desire has emerged to allow for some automated maintenance of wind turbine blades, to thereby improve the speed and/or precision of such a process. However, conventional automated maintenance devices are not always designed for reliable use on a wind turbine blade still connected to the rotor and hub of a wind turbine, and such systems are very slow in operation. As a result, the conventional automated options have not been adopted as manual repair by rope access technicians continues to be quicker and more efficient in many circumstances. Further improvements for automated maintenance and repair systems are desired. Accordingly, wind turbine manufacturers and operators continue to seek improved options for conducting automated maintenance and repair on the wind turbine blades of modern wind turbine designs.

Summary

To these and other ends, embodiments of the invention are directed to a robotic maintenance device for repairing damage around a leading edge of a wind turbine blade of a wind turbine. In this regard, the maintenance device includes a main body with first and second body portions extending towards opposite sides of the leading edge when the maintenance device is mounted on the wind turbine blade. The maintenance device also includes an articulated arm connected to the main body and configured to selectively engage with one or more tool heads used for conducting maintenance and repair actions on the wind turbine blade. A drive is coupled to the first and second body portions and is configured to move the maintenance device longitudinally along the leading edge of the wind turbine blade, and a control system is configured to operate the articulated arm and the drive. The drive includes at least three pairs of clamping actuators connected to the first and second body portions. Each pair of clamping actuators is mounted on the main body to move along a stroke direction into and out of clamped engagement with opposite sides of the wind turbine blade and also move along a longitudinal direction towards and away from the remaining pairs of clamping actuators. These directional movements enable movement of the maintenance device along the leading edge. The use of this drive with the maintenance device improves the precision and reliability of automated repair actions done on a wind turbine blade while the blade remains attached to the rotor hub.

In one embodiment, the drive further includes linear actuators coupled to each of the clamping actuators. Some of the linear actuators are operable to move one of the clamping actuators in opposite directions along the stroke direction, while some others of the linear actuators are operable to move one of the clamping actuators in opposite directions along the longitudinal direction. Each of the linear actuators may be defined by a piston and cylinder, with the control system controlling operation of the linear actuators. For example, the piston of each linear actuator can be hydraulically, pneumatically, or electrically actuated.

In another embodiment, the control system operates the clamping actuators such that at least two of the pairs of clamping actuators remain in clamped engagement with the wind turbine blade to continuously secure the maintenance device on the wind turbine blade during movement along the leading edge and during any maintenance and repair actions.

In yet another embodiment, the drive further includes a longitudinal rail connected to each of the first and second body portions. Each of the clamping actuators is mounted on one of the longitudinal rails (e.g., in each pair of clamping actuators, one of the pair is mounted on the longitudinal rail connected to the first body portion while the other of the pair is mounted on the longitudinal rail connected to the second body portion), and the main body is configured to move as one piece with the longitudinal rails. The at least three pairs of clamping actuators may include a front pair of clamping actuators positioned at one end of the main body, a rear pair of clamping actuators positioned at an opposite end of the main body, and a middle pair of clamping actuators located between the front pair and the rear pair. The middle pair of clamping actuators is rigidly coupled to the longitudinal rails and the front pair and rear pair are movably coupled to the longitudinal rails so as to move in the longitudinal direction relative to the longitudinal rails. In such embodiments, the control system actuates the drive using a series of steps to produce a movement of the maintenance device along the leading edge of the wind turbine blade, the steps including:

• moving the rear pair of clamping actuators along the stroke direction away from engagement with opposite sides of the wind turbine blade;

• moving the rear pair of clamping actuators on the longitudinal rails along the longitudinal direction to a position adjacent the middle pair of clamping actuators;

• moving the rear pair of clamping actuators along the stroke direction towards the opposite sides of the wind turbine blade to clamp into engagement with the blade;

• moving the middle pair of clamping actuators along the stroke direction away from engagement with opposite sides of the wind turbine blade; • moving the middle pair of clamping actuators and the longitudinal rails along the longitudinal direction such that the middle pair of clamping actuators moves to a position adjacent the front pair of clamping actuators;

• moving the middle pair of clamping actuators along the stroke direction towards the opposite sides of the wind turbine blade to clamp into engagement with the blade;

• moving the front pair of clamping actuators along the stroke direction away from engagement with opposite sides of the wind turbine blade;

• moving the front pair of clamping actuators on the longitudinal rails along the longitudinal direction to a position spaced apart from the middle pair of clamping actuators; and

• moving the front pair of clamping actuators along the stroke direction towards the opposite sides of the wind turbine blade to clamp into engagement with the blade.

In a further embodiment, the maintenance device includes at least one idler wheel mounted on an undersurface of the main body which faces towards the wind turbine blade. The idler wheel(s) are configured to be rolled along the leading edge of the wind turbine blade to help support a weight of the maintenance device when the drive moves the maintenance device along the wind turbine blade.

In another embodiment, the control system includes at least one camera to provide visual feedback on an operational state of the maintenance device and components thereof. For example, the control system may include an overview camera and a scanning camera. The overview camera is mounted on a mast extending upwardly from the main body, and the overview camera provides a complete overview of the maintenance robot and current operation. Such an overview may be helpful to transmit to an operator located remote from the wind turbine blade, e.g., on the ground surface. The scanning camera is mounted on the articulated arm and it is configured to image the surface of the blade in the vicinity of the leading edge, and/or image damaged areas of the wind turbine blade. In still another embodiment, the articulated arm includes a series of arm portions and joints enabling a free end of the articulated arm to reach any portion of the leading edge and the opposite sides of the wind turbine blade to perform maintenance of repair actions. The free end of the articulated arm includes an interface element that mechanically and electrically couples with corresponding interfaces provided on the tool heads. It will be understood that the various features described in these embodiments of the maintenance device may be combined in any combination and sub-combination to achieve the desired technical advantages and effects described herein.

Embodiments of the present invention are also directed to a method for automatically repairing damage around a leading edge of a wind turbine blade. The method includes positioning a robotic maintenance device having a main body, a vision system, an articulated arm, and a drive by operating the drive to move the main body along the leading edge of the wind turbine blade such that the articulated arm can move into position at a location containing damage on the blade. The method also includes scanning the wind turbine blade with the vision system to produce image data confirming a location and severity of damage on the wind turbine blade. The method further includes calculating a movement path for each of a cleaning/abrading tool head and a coating applicator tool head based on the location and severity of the damage shown in the image data. The articulated arm then couples to the cleaning/abrading tool head and the cleaning/abrading tool head is used to sand down a surface of the blade around the damage and subsequently clean the surface to prepare the surface for repair. The articulated arm then couples to the coating applicator tool head and uses the coating applicator tool head to apply layers of a coating to the surface of the wind turbine blade. The damage is thus repaired on the wind turbine blade, and the method achieves greater efficiency and quality of repair than known methods for repairing leading edge blade damage such as erosion damage.

In one embodiment, the method further includes operating the wind turbine to move one of the wind turbine blades to a generally horizontal orientation. That blade is then pitched such that the leading edge of the blade is oriented to face vertically upward, thereby placing the blade in position to receive the robotic maintenance device.

In some embodiments, the drive includes at least three pairs of clamping actuators connected to first and second body portions of the main body, which extend towards opposite sides of the leading edge when the maintenance device is mounted on the wind turbine blade. Operating the drive further includes actuating each pair of the clamping actuators to selectively move along a stroke direction into and out of clamped engagement with opposite sides of the blade, and selectively moving each pair of clamping actuators along a longitudinal direction towards and away from the remaining pairs of clamping actuators. In one example, the drive includes linear actuators coupled to each of the clamping actuators, and the step of operating the drive includes using some of the linear actuators to move the clamping actuators along the stroke direction and using some others of the linear actuators to move one pair of the clamping actuators along the longitudinal direction relative to the other pairs of the clamping actuators (e.g., some of the linear actuators move the clamping actuators along the stroke direction, while some others of the linear actuators move the clamping actuators along the longitudinal direction). In this method, at least two of the pairs of clamping actuators are maintained in clamped engagement with the wind turbine blade at all times to continuously secure the maintenance device in position on the blade during movement along the leading edge and during maintenance and repair actions.

As set forth above, the drive may also include a longitudinal rail connected to each of the first and second body portions, with the at least three pairs of clamping actuators including a front pair, a rear pair, and a middle pair. The series of control steps listed above (moving the rear pair of clamping actuators, then moving the middle pair of clamping actuators, and then moving the front pair of clamping actuators) can then be followed in embodiments of this method to define the operation of the drive.

In another embodiment, the method includes scanning the wind turbine blade with the vision system after using the cleaning/abrading tool head but before using the coating applicator tool head. This scan accounts for the material removal caused by operation of the cleaning/abrading tool head, and the movement path for the coating applicator tool head can be re-calculated if needed.

In another embodiment, the method includes scanning the wind turbine blade with the vision system after using the cleaning/abrading tool head and the coating applicator tool head. This scan confirms whether further repair actions are necessary at the location containing damage on the blade.

In a further embodiment, the vision system includes cameras that image operations of the maintenance device and the blade. The method then includes transmitting images from the cameras to an offsite operator that is not located on the blade while the maintenance device operates, and modifying operation of the maintenance device based on commands received from the offsite operator.

The steps and elements described herein can be reconfigured and combined in many different combinations to achieve the desired technical effects in different styles of wind turbines, as may be needed in the art.

Brief Description of the Drawinqs

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the invention.

Fig. 1 is a perspective view of a wind turbine according to one embodiment of the invention.

Fig. 2 is a front view of a wind turbine blade of the wind turbine of Fig. 1 , showing various levels of erosion-type damage along a leading edge that is pitched upwardly. Fig. 3 is a top perspective view of a robotic maintenance device in accordance with embodiments of the present invention, mounted in position on the leading edge of the wind turbine blade of Fig. 2 with an articulated arm moving over a surface containing the damage.

Fig. 4 is a top perspective partially cross-sectioned view along line 4-4 in Fig. 3 of the robotic maintenance device of this embodiment, showing the drive in further detail.

Fig. 5A is a partially cross-sectioned top view of one part of the drive on the robotic maintenance device of Fig. 4, with the drive shown in a first operational state where a rear pair of clamping actuators is about to move along a stroke direction away from clamped engagement with the wind turbine blade.

Fig. 5B is a partially cross-sectioned top view of the drive of Fig. 5A, with the drive shown in a second operational state where the rear pair of clamping actuators is disengaged with the blade and is about to move along a longitudinal direction towards a middle pair of clamping actuators.

Fig. 5C is a partially cross-sectioned top view of the drive of Fig. 5B, with the drive shown in a third operational state where the rear pair of clamping actuators is now adjacent the middle pair of clamping actuators and is about to move along a stroke direction towards clamped engagement with the wind turbine blade.

Fig. 5D is a partially cross-sectioned top view of the drive of Fig. 5C, with the drive shown in a fourth operational state where the rear pair of clamping actuators is now engaged with the wind turbine blade and the middle pair of clamping actuators is about to move along a stroke direction away from clamped engagement with the wind turbine blade.

Fig. 5E is a partially cross-sectioned top view of the drive of Fig. 5D, with the drive shown in a fifth operational state where the middle pair of clamping actuators is disengaged with the blade and is about to move with the longitudinal rails along a longitudinal direction towards a front pair of clamping actuators.

Fig. 5F is a partially cross-sectioned top view of the drive of Fig. 5E, with the drive shown in a sixth operational state where the middle pair of clamping actuators is now adjacent the front pair of clamping actuators and is about to move along a stroke direction towards clamped engagement with the wind turbine blade.

Fig. 5G is a partially cross-sectioned top view of the drive of Fig. 5F, with the drive shown in a seventh operational state where the middle pair of clamping actuators is now engaged with the wind turbine blade and the front pair of clamping actuators is about to move along a stroke direction away from clamped engagement with the wind turbine blade.

Fig. 5H is a partially cross-sectioned top view of the drive of Fig. 5G, with the drive shown in an eighth operational state where the front pair of clamping actuators is disengaged with the blade and is about to move along a longitudinal direction away from the middle pair of clamping actuators.

Fig. 5I is a partially cross-sectioned top view of the drive of Fig. 5H, with the drive shown in a ninth operational state where the front pair of clamping actuators is now spaced apart from the middle pair of clamping actuators and is about to move along a stroke direction towards clamped engagement with the wind turbine blade.

Fig. 5J is a partially cross-sectioned top view of the drive of Fig. 5I, with the drive shown in a tenth operational state where the front pair of clamping actuators is now engaged with the wind turbine blade, returning the drive back to the first operational state but with the maintenance device moved a distance along the leading edge of the blade.

Fig. 6A is a top perspective view of the robotic maintenance device according to an embodiment of the invention, showing an operational state in which the articulated arm moves vision system equipment to scan an area of the wind turbine blade containing damage.

Fig. 6B is a top perspective view of the robotic maintenance device of Fig. 6A, showing a further operational state in which the articulated arm has moved to allow the vision system to scan a different area on the wind turbine blade.

Fig. 6C is a top perspective view similar to Fig. 6B but with most of the robotic maintenance device shown in phantom to highlight a cleaning/abrading tool head that may be coupled to the articulated arm.

Fig. 6D is a top perspective view similar to Fig. 6C after the articulated arm is connected to the cleaning/abrading tool head, showing the cleaning/abrading tool head in use along the leading edge of the wind turbine blade.

Fig. 6E is a top perspective view similar to Fig. 6B but with most of the robotic maintenance device shown in phantom to highlight a coating applicator tool head that may be coupled to the articulated arm.

Fig. 6F is a top perspective view similar to Fig. 6E after the articulated arm is connected to the coating applicator tool head, showing the coating applicator tool head in use to apply layers of coating to the leading edge of the wind turbine blade to repair the damage.

Fig. 6G is a top perspective view similar to Fig. 6F, showing a further operational state after use of the cleaning/abrading tool head and the coating applicator tool head, specifically in which the vision system is used to scan the repaired blade to confirm that a desirable repair has been completed.

Detailed Description

With reference to Figs. 1 through 6G, embodiments of a robotic maintenance device and a method for automatically repairing damage around a leading edge of a wind turbine blade are shown in detail. The maintenance device includes a drive that helps reliably maintain the robotic maintenance device in clamped engagement on the wind turbine blade even when the blade is still connected to the wind turbine rotor and hub. To this end, when a repair or maintenance action is required, the wind turbine moves the selected blade to a generally horizontally-extending position with the leading edge pitched upwardly, and then the maintenance device can be mounted on and move along the lengthwise length of the blade at the leading edge. The drive allows for longitudinal movements of the maintenance device along the length of the blade to enable the repairs, while also assuring the position of the maintenance device during repair process steps to increase the precision and accuracy of repairs done, thus minimizing operational downtime for conducting such maintenance and repair actions. The maintenance device also uses a new advantageous method for repairing so-called category-1 and category- 2 damage to the outer coatings of a wind turbine blade, the method including scanning the blade to image the damaged area, sanding down a surface of the blade around the damaged area and cleaning the same, and then applying layers of coating by painting or the like to repair the damage. This method produces a high quality repair with minimal time, once again helping minimize operational downtime, while also avoiding the need for rope access technicians and the associated safety and timing problems of manual repairs. Other advantages and effects of the embodiments of this invention will be evident from the following description.

Throughout this application, the correction of erosion damage on wind turbine blades is typically referred to as a "repair" of those damages. In some contexts, "damage" refers to more significant damages to the blade (perhaps beyond what is described as "category-1" and "category-2" damage herein), and so the operation of the maintenance device may be deemed a routine maintenance action that occurs before a blade is "damaged" in such contexts. In this regard, the maintenance device is capable of providing preventative maintenance to remove wear and erosion effects before such effects cause "damage" that must be repaired on the wind turbine blade, and the maintenance device is also capable of providing more thorough repairs after damage is caused on the blade. Turning with reference to Fig. 1 , a wind turbine 10 is shown to include a tower 12, a nacelle 14 disposed at the apex of the tower 12, and a rotor 16 operatively coupled to a generator (not shown) housed inside the nacelle 14. The rotor 16 of the wind turbine 10 includes a central hub 18 and a plurality of wind turbine blades 20 that project outwardly from the central hub 18 at locations circumferentially distributed around the hub 18. As shown, the rotor 16 includes three wind turbine blades 20, but the number of blades 20 may vary from one wind turbine to another. The wind turbine blades 20 are configured to interact with air flow to produce lift that causes the rotor 16 to spin generally within a plane defined by the wind turbine blades 20. As the rotor 16 spins, the wind turbine blades 20 pass through the air with a leading edge 22 leading the respective wind turbine blade 20 during rotation. As schematically evidenced by a tractor trailer 24 shown along a ground surface at the bottom of the tower 12, the wind turbine blades 20 in use are spaced apart from the ground surface by a significant distance, which normally renders maintenance and repair actions difficult. However, the robotic maintenance device of this invention improves the repair process to make same easy and less time-consuming as will be set forth in detail below.

As the wind turbine 10 ages, one or more of the wind turbine blades 20 may experience erosion from prolonged, continuous exposure to the environment. One example of such erosion damage 26 is shown in Fig. 1 and better shown in the detailed view of Fig. 2. While not being particularly limited to any source, erosion damage 26 may occur due to particulates in the air that abrade the leading edge 22 of the wind turbine blade 20 during operation. Erosion therefore may occur in an erosion zone that includes the leading edge 22, but it may also occur in other areas in the surface 30 of the blade 20. Accordingly, while the robotic maintenance device is configured to repair damage and move along the leading edge 22, this device is also capable of conducting maintenance and repair actions anywhere along the outer surface of the blades 20.

Erosion damage 26 is generally characterized as a loss of material from the wind turbine blade 20. Material loss may be uniformly distributed but is often non-uniform across the leading edge 22 or any other surface of the wind turbine blade 20. Rather than losing a uniform skin of material from a surface, erosion may include localized surface imperfections, such as random pitting and shallow gouges or crack-like features that may be a result of localized, connected pitting (as a result of impacts with debris or other matter in the environment). In any case, if erosion damage 26 is not repaired in a timely fashion, the wind turbine blade 20 becomes less efficient at rotating the rotor 16 and ultimately, the structural integrity of the wind turbine blade 20 may be significantly impaired. With reference to the detailed view in Fig. 2, it will be understood that the erosion damage 26 may define differing levels of severity based on how deep the damage extends inwardly into the material layers defining the outer shell of the blade 20. In the example shown, the erosion damage 26 includes some areas with an erosion or cut of material through the outer topcoat layer into a second layer of material underneath the topcoat, which is categorized as a "category 1" level of severity, and further areas with an erosion or cut of material through the outer topcoat layer and the second later of material into a third layer of material underneath the second layer, which is categorized as a "category 2" level of severity. For reference, deeper cuts and erosions defining more significant damage is typically categorized at higher levels such as category 3, 4, or 5. In Fig. 2, the topcoat is shown at 28a, the revealed areas of second layer are shown at 28b, and the revealed areas of third layer are shown at 28c. These various layers 28a, 28b, 28c of material may be different in color, which can help with the identification of damage severity and repair confirmation after the repair is completed with the maintenance device. By identifying and correcting such lower levels of erosion damage 26 promptly, more significant damage of the blade 20 can be avoided along with higher operational downtime caused by the more significant damage.

Fig. 3 provides an overview of the robotic maintenance device 40 in accordance with embodiments of this invention. The maintenance device 40 includes a main body 42 having a first body portion 44 and a second body portion 46 extending towards opposite sides of the leading edge 22 of the blade 20 when the maintenance device 40 is mounted atop the leading edge 22 of the blade 20 as shown in this Figure. It will be appreciated that the wind turbine 10 is halted with the blade 20 to be worked upon in a generally horizontal orientation with the blade 20 pitched so that the leading edge 22 faces upwardly when the maintenance device 40 is placed upon the blade 20. The maintenance device 40 can be moved onto the blade 20 in various manners without departing from the scope of this invention, including by crane and/or by flying vehicle. The main body 42 generally defines a framework for other components of the maintenance device 40 to be mounted on, as set forth in the following description.

Along one end of the main body 42, an articulated arm 48 is connected to the main body 42 so as to project outwardly beyond a front of the remainder of the maintenance device 40. The articulated arm 48 is defined by a series of arm portions 50 connected together at rotational joints 52 in this embodiment. Movement of the arm portions 50 at the joints 52 enable a free end 54 of the articulated arm 48 to move all around the periphery and surface of the wind turbine blade 20. To this end the free end 54 is capable of accessing any portion on the surface of the blade 20 to conduct inspection or maintenance and repair actions in this embodiment (or any portion within the physical range defined by the articulated arm 48). The free end 54 of the articulated arm 48 also carries elements defining part of a vision system 56 for the maintenance device 40. For example, the vision system 56 may include a laser (not shown) and/or a scanning camera 58 configured to image the surface 30 in the vicinity of the leading edge 22 and/or damaged areas on the blade 20.

As also shown in Fig. 3, the maintenance device 40 also includes in this embodiment a mast 60 that projects upwardly from the main body 42 to a position well above the remainder of the maintenance device 40. The vision system 56 also includes an overview camera 62 mounted on the mast 60. The overview camera images the remainder of the maintenance device 40 to provide a complete overview of the operational status and actions of the maintenance device 40. Such an overview can be desirable when the maintenance device 40 is at least partially monitored or controlled from a location offsite, including on the ground surface rather than on the blade 20. More or fewer camera devices may be provided in other embodiments to allow for visual feedback to be provided to the maintenance device 40 and/or to an operator. The main body 42 serves as a support for one or more tool heads that may be selectively engaged by the articulated arm 48 to conduct the necessary repair and maintenance actions. In the embodiment shown, two exemplary tool heads are provided on the maintenance device 40. The first is a cleaning/abrading tool head 70 that is configured to sand down the surface of the wind turbine blade 20 containing damage and then clean that surface to prepare it for repair. The second is a coating applicator tool head 80 that is configured to apply layers of coating material onto the surface of the blade 20 to fill in damaged areas and thereby repair the blade 20. It will be understood that the particular design of these tool heads as well as the total number of tool heads located on the maintenance device 40 may vary in other embodiments without departing from the scope of the invention, as each tool head is designed to provide a certain functionality and such functionality needs may vary in different contexts and applications. The free end 54 of the articulated arm 48 includes an interface element 64 that can mechanically and electrically couple with corresponding interface elements 66 located on each of the tool heads 70, 80. The interface elements 64, 66 are of any standard design known in robotics and are not described in further detail herein.

The maintenance device 40 also includes a control system 90 shown schematically in Fig. 3 and implemented on known hardware and software platforms. The control system 90 is operatively connected to the other portions of the maintenance device 40, including the articulated arm 48, the vision system 56, and a drive 100, to thereby operate these elements. The control system 90 is capable of responding to inputs from the vision system 56 and/or from an offsite operator to modify the actions taken by the maintenance device 40 based on the repair or maintenance needed on the blade 20. The operation of the control system 90 will be further explained below as the method for operating the maintenance device 40 is shown in further detail.

The drive 100 is further illustrated in Figs. 3 and 4. As noted above, the main body 42 includes first and second body portions 44, 46 that extend towards opposite sides of the leading edge 22 of the blade 20 when the maintenance device 40 is mounted atop the leading edge 22. The drive 100 is defined by a plurality of elements located along longitudinal rails 102 extending along a length of the maintenance device 40 at the free ends defined by the first and second body portions 44, 46. Furthermore, in the position shown, a plurality of idler wheels 104 connected to an undersurface of the main body 42 between the first and second body portions 44, 46 sit directly on the leading edge 22 of the blade 20, two of such idler wheels 104 being visible in Fig. 3. The idler wheels 104 can freely rotate along the surface of the blade 20 in response to movements of the maintenance device 40 generated by the drive 100 as will be described. The idler wheels 104 help support a weight of the maintenance device 40 on the blade 20 such that the entire weight is not applied to the drive 100 and its elements. These idler wheels 104 may be formed from a plastics material or any other suitable material, typically a low- friction material to help avoid any damage upon engagement with the blade 20. The drive 100 includes a plurality of clamping actuators 106a, 106b, 106c that extend from the longitudinal rails 102 into selective clamped engagement with the opposite sides of the wind turbine blade 20. The idler wheels 104 and the clamping actuators 106a-c define the points of direct contact between the maintenance device 40 of this embodiment and the blade 20. It will be understood that only one idler wheel 104 or any other number of idler wheels 104 may be provided in other embodiments.

In the embodiment shown in Figs. 3 and 4, the drive 100 includes three pairs of actuators in the plurality of clamping actuators 106a-c. To this end, the plurality of clamping actuators 106a-c includes a front pair of clamping actuators 106a located at one longitudinal end of the main body 42, a middle pair of clamping actuators 106b, and a rear pair of clamping actuators 106c located at another longitudinal end of the main body 42. The middle pair of clamping actuators 106b is positioned between the front and rear pairs. The drive 100 is configured to move one pair of the clamping actuators at a time relative to the other pairs to produce movements in either direction along the leading edge 22 of the blade 20. To this end, the plurality of clamping actuators 106a-c is configured to produce a steady crawling-like movement along the blade 20 as the maintenance device 40 is positioned for conducting repair and maintenance actions. The specific movement steps defining this crawling-like movement will be described in further detail below. Advantageously, the drive 100 always maintains at least two pairs of the plurality of clamping actuators 106a-c in clamped engagement with the blade 20 at all times, even during movement action, which reliably retains the maintenance device 40 in secure engagement with the blade 20 even though the maintenance device 40 is operating on the blade 20 well above the ground surface and in the significantly windy ambient environment that the blade 20 normally operates in. Moreover, this design of the drive 100 allows both for movement of the maintenance device 40 and rigid engagement in position during repair method steps in order to make repair actions more precise and accurate, thereby to help minimize downtime needed for repair or maintenance actions. It will be understood that other embodiments of the drive 100 may include more than three pairs of clamping actuators 106a-c without departing from the scope of the invention, but at least three pairs are always provided to achieve the technical advantages described herein.

Now turning specifically to Fig. 4, the main body 42 of the maintenance device 40 is sectioned along a horizontal plane just above the longitudinal rails 102 such that the components defining the drive 100 in this embodiment of the invention are revealed in further detail. All of the plurality of clamping actuators 106a-c are shown in Fig. 4 in clamped engagement with the opposite sides of the wind turbine blade 20, which is shown in phantom. Each of the clamping actuators 106a-c includes a support bracket 110 coupled to the corresponding longitudinal rail 102, an elongate arm 112 coupled with the support bracket 110, and gripping pad 114 located at one end of the elongate arm 112. The elongate arm 112 of each clamping actuator 106a-c is slidably movable along a stroke direction relative to the support bracket 110 such that the gripping pad 114 can be moved towards and away from the surface of the blade 20. Although the elongate arm 112 of each clamping actuator 106a-c is shown as two parallel rod-like members in Fig. 4, it will be appreciated that other types of arm designs may also be used in other embodiments. Likewise, the particular shape and material defining the gripping pad 114 can also be modified depending on the wind turbine blade 20 that is to be repaired by the maintenance device 40. The drive 100 also includes linear actuators for moving the clamping actuators 106a-c in opposite direction along respective axes. In this regard, each of the clamping actuators 106a-c includes a stroke-direction linear actuator 116 that is rigidly mounted on the support bracket 110 of that clamping actuator 106a-c. The stroke-direction linear actuator 116 of this embodiment is of a pnematically driven piston and cylinder design, as will be described in further detail with reference to the operating states of the drive 100 shown in Figs. 5A through 5J. For example, the piston 118 of the stroke-direction linear actuator 116 is rigidly coupled to the gripping pad 114 and/or the elongate arm 112, while the cylinder 120 of the stroke-direction linear actuator 116 is rigidly coupled to the support bracket 110. Therefore, as the piston 118 is retracted within the cylinder 120, the elongate arm 112 and gripping pad 114 are withdrawn away from contact with the blade 20, and vice versa. The control system 90 is operatively connected to the stroke-direction linear actuators 116 and thereby controls supply of pneumatic fluid (e.g., pressurized air) to and from the linear actuators 116 to cause movements of the clamping actuators 106a-c along the stroke direction. The various pneumatic lines are not shown in these illustrations for the sake of simplicity, and it will be appreciated that a source of compressed air (not shown) such as a pre-pressurized pressure vessel or an air compressor may be provided somewhere on the maintenance device 40 in such embodiments.

In a similar fashion, the drive 100 also includes a longitudinal -direction linear actuator 122 extending between the support brackets 110 of adjacent pairs of the clamping actuators 106a-c located on the same side of the main body 42 (e.g., "pairs" as defined in this context along the same longitudinal rail 102). The longitudinal -direction linear actuators 122 are defined by a pneumatic piston and cylinder design in this embodiment, with the piston 124 of these linear actuators 122 being rigidly coupled to one of the front pair of clamping actuators 106a or connected to one of the rear pair of clamping actuators 106c, and the cylinder 126 of these linear actuators 122 being rigidly coupled to one of the middle pair of clamping actuators 106b. Once again, the control system 90 is operatively connected to the longitudinal -direction linear actuators 122 to control movements of these linear actuators 122 and corresponding relative movements of the clamping actuators 106a-c along the longitudinal direction. To this end, when the pistons 124 are fully extended from the corresponding cylinders 126, as shown in Fig. 4, the support brackets 110 and the clamping actuators are spaced apart from one another such that the middle pair of clamping actuators 106b is generally equally spaced between the front and rear pairs of clamping actuators 106a, 106c.

The support brackets 110 on the front pair of clamping actuators 106a and on the rear pair of clamping actuators 106c are movably coupled to the longitudinal rails 102, but the support brackets 110 on the middle pair of clamping actuators 106b is rigidly coupled to the corresponding longitudinal rail 102. As a result, when either of the longitudinal - direction linear actuators 122 is used, the front or rear pair of clamping actuators 106a, 106c moves along the stationary longitudinal rail 102 towards or away from the middle pair of clamping actuators 106b; or put another way, the middle pair of clamping actuators 106b moves along with the longitudinal rail 102 relative to the front or rear pair of clamping actuators 106a, 106c. This operation is further explained in detail with reference to Figs. 5A through 5J below.

Other embodiments of linear actuators may be used in non-illustrated embodiments of the robotic maintenance device 40, including hydraulic piston drives, electric motor drives, and/or mechanical drives, for example. The use of linear actuators allows for simple structures and controls when controlling movements of the maintenance device 40 along the length of the blade 20, thereby contributing to the ability for the maintenance device 40 to move quickly along that direction (while also remaining secured at all times with a plurality of points of contact to the surface of the blade 20). Moreover, in embodiments containing more than three pairs of clamping actuators 106a-c, the linear actuators and connections between the support brackets 110 and the longitudinal rails 102 may be modified to allow for the relative movement between pairs of clamping actuators 106a-c needed in such embodiments. Regardless of how the drive 100 is reconfigured in such alternatives, the following description of drive operation will be easily analogized to work with differing structural designs by those skilled in the art. For the sake of brevity, only one operational movement cycle with the illustrated embodiment of the drive 100 is described in detail. The operational movement cycle for the drive 100 begins in a first operational state shown in Fig. 5A. While only one side of the drive 100 is shown in Figs. 5A through 5J, it will be understood that the other side of the drive 100 generally works in tandem or parallel with the same movements in this embodiment so that the robotic maintenance device 40 moves as a unitary piece. In Fig. 5A, all three of the clamping actuators 106a-c on this side of the drive 100 are engaged in clamped engagement with the surface 30 of the wind turbine blade 20. To begin a movement cycle, the control system 90 actuates each of the stroke-direction linear actuators 116 on the rear pair of clamping actuators 106c (only one of which is shown in these Figures) to withdraw its piston 118 back within the corresponding cylinder 120. As a result, the piston 118 will pull the elongate arm 112 and the gripping pad 114 of the rear clamping actuator 106c along the stroke direction away from engagement with the blade 20, as shown by arrow 150 in Fig. 5A. This disengagement of the rear pair of clamping actuators 106c enables movement of the rear pair longitudinally relative to the remainder of the drive 100 in the subsequent steps.

Next, as shown in Fig. 5B, the stroke-direction linear actuator 116 on the rear clamping actuator 106c has completed the stroke direction movement of the rear clamping actuator 106c away from the surface 30 of the blade 20. The control system 90 then actuates the longitudinal -direction linear actuator 122 that extends between the middle clamping actuator 106b and the rear clamping actuator 106c to withdraw its piston 124 back into the corresponding cylinder 126. Such movement causes the rear clamping actuator 106c to move along the longitudinal direction on the longitudinal rail 102 towards the middle clamping actuator 106b, as also shown by arrow 152 in Fig. 5B. The longitudinal - direction linear actuator 122 continues moving the rear clamping actuator 106c until it is in a position adjacent the middle clamping actuator 106b. The completion of this movement along the longitudinal direction is shown at Fig. 5C. It will be understood that in some embodiments, the stroke-direction movement of the rear clamping actuator 106c may not be fully completed when the longitudinal direction movement begins, so long as the clamping engagement with the blade 20 is released before the longitudinal movement. This alternative will apply at each similar step of the process below. After the rear clamping actuator 106c has moved adjacent to the middle clamping actuator 106b, the control system 90 actuates the stroke-direction linear actuator 116 associated with the rear clamping actuator 106c again, but this time to extend the piston 118 from the cylinder 120. Such movement of the piston 118 pushes the elongate arm 112 and the gripping pad 114 towards the blade 20 in the stroke direction until the gripping pad 114 comes back into clamped engagement with the surface 30, as indicated by arrow 154 in Fig. 5C. As this movement is done on both sides of the drive 100 in this embodiment, it will be understood that all 3 pairs of clamping actuators 106a-c are once again clamped to the wind turbine blade 20, as shown in the operational state of Fig. 5D.

Now that the control system 90 has completed a movement cycle for the rear clamping actuator 106c, similar steps are repeated to move the middle clamping actuator 106b and the longitudinal rail 102 rigidly coupled to the support bracket 110 of the middle clamping actuator 106b. To this end, beginning at Fig. 5D, the control system 90 actuates the stroke-direction linear actuator 116 associated with the middle clamping actuator 106b to move its piston 118 and withdraw that back into the cylinder 120. Such movement results in a movement of the elongate arm 112 and gripping pad 114 of the middle clamping actuator 106b along the stroke direction away from engagement with the surface 30 of the blade 20, as shown by arrow 156 in Fig. 5D. Once the middle clamping actuator 106b is withdrawn away from the blade 20, either partially or fully as shown in Fig. 5E, the control system 90 actuates the longitudinal -direction linear actuator 122 connected to the middle clamping actuator 106b and the front clamping actuator 106a to withdraw its piston 124 within the cylinder 126. This actuation results in a movement of the middle clamping actuator 106b and also the longitudinal rail 102 rigidly coupled to the middle clamping actuator 106b along the longitudinal direction towards the front clamping actuator 106a as shown by arrows 158 in Fig. 5E. The middle clamping actuator 106b specifically moves from the position adjacent the rear clamping actuator 106c to a new position adjacent the front clamping actuator 106a, as shown in Fig. 5F. It will be understood that the longitudinal -direction linear actuator 122 extending between the middle clamping actuator 106b and the rear clamping actuator 106c may be simultaneously actuated to allow for this movement of the middle clamping actuator 106b away from the rear clamping actuator 106c, which remains in clamped engagement with the blade 20 during this movement step (e.g., the piston 124 on one longitudinal -direction linear actuator 122 is withdrawn into its cylinder 126 while the piston 124 on the other longitudinal -direction linear actuator 122 is extended away from its cylinder 126). Upon reaching the position adjacent the front clamping actuator 106a as shown in Fig. 5F, the control system 90 actuates the stroke-direction linear actuator 116 associated with the middle clamping actuator 106b again, but this time to extend the piston 118 from the cylinder 120. This movement causes the middle clamping actuator 106b and its gripping pad 114 to be moved along the stroke direction as shown by arrow 160 in Fig. 5F back into clamped engagement with the surface 30 of the blade 20. This step completes the movement cycle of the middle clamping actuator 106b and the longitudinal rail 102, as shown in Fig. 5G.

After the movement cycle for the middle clamping actuator 106b is completed, similar steps are repeated to move the front clamping actuator 106a. In this regard, beginning at Fig. 5G, the control system 90 actuates the stroke-direction linear actuator 116 associated with the front clamping actuator 106a to move its piston 118 and withdraw that back into the cylinder 120. Such movement results in a movement of the elongate arm 112 and gripping pad 114 of the front clamping actuator 106a along the stroke direction away from engagement with the surface 30 of the blade 20, as shown by arrow 162 in Fig. 5G. Once the front clamping actuator 106a is withdrawn away from the blade 20, either partially or fully as shown in Fig. 5H, the control system 90 actuates the longitudinal -direction linear actuator 122 connected to the middle clamping actuator 106b and the front clamping actuator 106a to extend its piston 124 out of the cylinder 126. This actuation results in a movement of the front clamping actuator 106a on the longitudinal rail 102 along the longitudinal direction away from the middle clamping actuator 106b as shown by arrow 164 in Fig. 5H. The front clamping actuator 106a moves to a new position spaced apart from the middle clamping actuator 106b, as shown in Fig. 5I. The control system 90 next actuates the stroke-direction linear actuator 116 associated with the front clamping actuator 106a again, but this time to extend the piston 118 from the cylinder 120. This movement causes the front clamping actuator 106a and its gripping pad 114 to be moved along the stroke direction as shown by arrow 166 in Fig. 5I back into clamped engagement with the surface 30 of the blade 20. This step completes the movement cycle of the front clamping actuator 106a, as shown in Fig. 5J.

As shown in Fig. 5J as compared to Fig. 5A, the clamping actuators 106a-c of the drive 100 are all repositioned back relative to one another but the drive 100 and the robotic maintenance device 40 has moved a distance along the lengthwise direction of the blade 20. Advantageously, during all steps of this operational movement cycle, at least two pairs of the clamping actuators 106a-c always remain in clamped engagement with the surfaces 30 of the blade 20, thereby assuring that the robotic maintenance device 40 reliably remains mounted on the blade 20 during the movement. Nevertheless, the series of steps shown from Figs. 5A to 5J can be completed quickly when using pneumatically- actuated linear actuators as shown, and then the cycle can be repeated to move the maintenance device 40 as far as necessary along the leading edge 22 of the wind turbine blade 20. It will be appreciated that the steps shown and described above can be reversed to cause movement of the maintenance device 40 in an opposite lengthwise direction along the blade 20. Moreover, during all movement steps in this embodiment, the idler wheels 104 roll along the leading edge 22 and help support the weight of the maintenance device 40 so as to not put excessive strain or stress on the clamping actuators 106a-c. Likewise, modifications to the operational steps and ordering thereof can be made in other embodiments of the invention, such as, for example, if more than 3 pairs of clamping actuators 106a-c are provided on the maintenance device 40. In addition, the stroke length of the various linear actuators can be modified in other embodiments. For example, the stroke length of the linear actuators that generate longitudinal movements of the clamping actuators 106a-c can be adjusted to modify the amount of movement of each pair of clamping actuators 106a-c, such as for improving the stability of the maintenance device 40.

Now that the operation of the drive 100 on the maintenance device 40 has been described in detail to show how the maintenance device moves into position along the leading edge 22 of the blade 20, the overall operation of the robotic maintenance device 40 is described with reference to Figs. 6A through 6G. To this end, the maintenance device 40 of this embodiment is configured to perform a method for automatically repairing damage around the leading edge 22 of the blade 20. As a general overview, this method includes the steps of scanning the blade 20 to detect a shape of the surface 30 at a location and a severity of damage at the location to guide further movements of tool heads, using the cleaning/abrading tool head 70 to sand down and clean the surface 30 of the blade 20 adjacent the damage, and then using the coating applicator tool head 80 to apply layers of coating to the surface 30 and thereby repair the damage. These and further optional steps and alternatives will now be described with reference to the Figures.

First, as shown in Fig. 6A, the maintenance device 40 is positioned on the leading edge 22 of the wind turbine blade 20 while the blade 20 remains attached to the wind turbine 10 and with the blade 20 pitched so that the leading edge 22 extends generally horizontally and facing upwardly. As can be seen in Fig. 6A, the leading edge 22 includes erosion damage 26 along a portion thereof. The drive 100 of the maintenance device 40 actuates as described in detail above to move the maintenance device 40 until the articulated arm 48 is within reach of the erosion damage 26 (e.g., to the position shown in each of FIGS. 6A through 6G). When the maintenance device 40 is securely clamped to the blade 20, the control system 90 uses one or more cameras or lasers associated with the vision system 56 to produce image data of the shape of the surface 30 of the blade 20 and the damage on the blade 20. For example, the scanning camera 58 on the free end 54 of articulated arm 48 can be used to capture images of the erosion damage 26 as shown schematically by the imaging broken lines shown in Fig. 6A. This scanning can continue as the articulated arm 48 moves the scanning camera 58 to different positions as shown by the continued scanning being done in a different position in Fig. 6B. Such images from the scanning can be evaluated by the control system 90 to identify both the location and the severity of the damage on the blade 20, which also determines how the remainder of the maintenance and repair action should be conducted. For example, a deeper level of "category 2" damage will necessitate more layers of coating to be applied than areas with a shallower level of "category 1" damage. To this end, the movement path for each of the cleaning/abrading tool head 70 and the coating applicator tool head 80 can be calculated from these scans. It will be appreciated that the scans from varying cross-sections of the blade 20 can be logically combined by the control system 90 to establish a general working surface profile for the further steps of maintenance and repair (e.g., one or more robot working lines). It will also be understood that the maintenance device 40 is maintained generally stationary during performance of the steps in FIGS. 6A through 6G, so as to avoid unnecessary vibrations and movements that could make the repair inaccurate.

The method for automated repair continues as shown in Figs. 6C and 6D. In Fig. 6C, the cleaning/abrading tool head 70 is shown in isolation from the remainder of the robotic maintenance device 40. In this embodiment, the cleaning/abrading tool head 70 includes an abrading means 72 defined by a series of sandpaper brushes and a cleaning means (not shown) for removing dust and debris from the surface 30 of the blade 20. The articulated arm 48 connects to the cleaning/abrading tool head 70 in the storage position of Fig. 6C and then moves the cleaning/abrading tool head 70 over the working area on the blade 20 as shown in Fig. 6D while the abrading means 72 is rotated. The abrading means 72 is then operated to run over the surface 30 adjacent the erosion damage 26 to sand down the surface 30 and level it out for the next repair steps, with the articulated arm 48 typically making multiple passes of the abrading means 72 over the surface at different angular orientations around the leading edge 22. These movements are schematically shown by the arrows 172 in Fig. 6D. Similar movements are made by the articulated arm 48 to move the cleaning means of the cleaning/abrading tool head 70 over the surface 30 after the abrading to clear any dust or debris from the surface 30 of the blade 20. It will be understood that the abrading means 72 and the cleaning means may be defined by various different elements in different embodiments of the invention, so long as the cleaning/abrading tool head 70 remains adapted to perform these functions of the automatic repair process.

The method for automated repair further continues as shown at Figs. 6E and 6F. With reference to Fig. 6E, the coating applicator tool head 80 is shown in isolation from the remainder of the robotic maintenance device 40. In this embodiment, the coating applicator tool head 80 includes an applicator means 82 in the form of a roller that receives a dispensed coating and then applies it in a painting-like manner to the surface 30 of the wind turbine blade 20. The articulated arm 48 connects to the coating applicator tool head 80 in the storage position of Fig. 6E and then moves the coating applicator tool head 80 over the surface 30 adjacent the erosion damage 26 in a similar fashion as set forth above for the cleaning/abrading tool head 70. To this end, the articulated arm 48 is configured to run the applicator means 82 longitudinally over the surface 30 through one or more passes to apply layers of coating onto the surface 30, and the articulated arm 48 also can move to different angular orientations around the leading edge 22 for making these passes of the coating applicator tool head 80. These movements are schematically shown by the arrows 174 in Fig. 6F. It will be understood that the applicator means 82 may be defined by various different elements in other embodiments of the invention, so long as the coating applicator tool head 80 remains configured to perform these functions of the automatic repair process.

In some embodiments of the method of repair, it may be desirable to verify the quality of repair and/or to use operator feedback and input to adjust how the steps described above are performed. Thus, with reference to Fig. 6G, further steps of the method are shown for such embodiments. The method further includes scanning with the vision system 56 the surface 30 of the wind turbine blade 20 adjacent the repairs made along the leading edge 22, for example, after the repair steps have been performed with the cleaning/abrading tool head 70 and with the coating applicator tool head 80. This scanning with the vision system 56 can produce images that may be analyzed by the control system 90 to determine whether further repair actions are necessary, e.g., whether the repair is completed with good quality. Furthermore, the method can include using cameras of the vision system 56 to image operations of the maintenance device 40 at all times during the method of repair, and then such images are transmitted to an offsite operator (shown schematically by "image transfer" block 176 in Fig. 6G) such as one stationed within the tractor trailer 24 on the ground surface below the wind turbine 10. The operator can provide feedback based on these images, and then the control system 90 modifies operation of the maintenance device 40 based on commands and feedback received from the offsite operator. It will be appreciated that further method steps of scanning the blade 20 following use of the cleaning/abrading tool head 70 but before use of the coating applicator tool head 80, to thereby account for the material removal caused by operation of the cleaning/abrading tool head 70, and the movement path for the coating applicator tool head 80 can be re-calculated if needed. Of course, these optional further steps may be omitted in some embodiments where visual verification of the repair is deemed unnecessary or the process is meant to be completely automated.

The robotic maintenance device 40 and method described in these embodiments allows for a repair or maintenance action to be taken without requiring human operators or rope access technicians on the wind turbine blade 20 itself. Furthermore, the drive 100 of the maintenance device 40 is configured to always maintain reliable clamped engagement with the blade 20 while operating on the blade 20, to thereby improve the precision and accuracy of repairs made with the tools. Lesser categories of blade damage such as erosion damage 26 can be quickly repaired when using this device and method, which will lead turbine operators to perform such routine maintenance on a regular schedule that should mostly avoid damage build up overtime that can cause significant operational downtime when blades 20 need to be removed or replaced for complex repair. An operator on the ground surface may also interact with the maintenance device 40 to help control and guide the maintenance and repair actions and assure these are done efficiently and with high quality. Thus, the maintenance device 40 and method achieves several technical advantages and improves the maintenance field as it relates to wind turbines and wind energy generation.

While the present invention has been illustrated by a description of various preferred embodiments and while these embodiments have been described in some detail, it is not the intention of the Applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Thus, the various features of the invention may be used alone or in any combination depending on the needs and preferences of the user.

Claims

1. A robotic maintenance device (40) for repairing damage around a leading edge (22) of a wind turbine blade (20) on a wind turbine (10), the maintenance device characterized by: a main body (42) including first and second body portions (44, 46) extending towards opposite sides of the leading edge when the maintenance device is mounted on the wind turbine blade; an articulated arm (48) connected to the main body and configured to selectively engage with one or more tool heads (70, 80) used for conducting maintenance and repair actions on the wind turbine blade; a drive (100) coupled to the first and second body portions and configured to move the maintenance device longitudinally along the leading edge of the wind turbine blade; and a control system (90) configured to operate the articulated arm and the drive, characterized in that the drive comprises at least three pairs of clamping actuators (106a-c) connected to the first and second body portions, wherein each pair of clamping actuators is mounted on the main body to move along a stroke direction into and out of clamped engagement with opposite sides of the wind turbine blade and also move along a longitudinal direction towards and away from other pairs of clamping actuators, thereby enabling movement of the maintenance device along the leading edge.

2. The robotic maintenance device of claim 1 , characterized in that the drive comprises linear actuators coupled to each of the clamping actuators, with some of the linear actuators being operable to move one of the clamping actuators in opposite directions along the stroke direction and some others of the linear actuators being operable to move one of the clamping actuators in opposite directions along the longitudinal direction.

3. The robotic maintenance device of claim 2, characterized in that each of the linear actuators includes a piston and cylinder, and the control system controls operation of the linear actuators.

4. The robotic maintenance device of claim 3, characterized in that the piston of each of the linear actuators is hydraulically, pneumatically, or electrically actuated.

5. The robotic maintenance device of any of the preceding claims, characterized in that the control system operates the clamping actuators such that at least two of the pairs of clamping actuators remain in clamped engagement with the wind turbine blade to continuously secure the maintenance device on the wind turbine blade during movement along the leading edge and during maintenance and repair actions.

6. The robotic maintenance device of any of the preceding claims, characterized in that the drive further includes a longitudinal rail connected to each of the first and second body portions, with each pair of clamping actuators being mounted on the longitudinal rails such that one clamping actuator of each pair is mounted on the longitudinal rail connected to the first body portion while the other clamping actuator of each pair is mounted on the longitudinal rail connected to the second body portion, and wherein the main body is configured to move as one piece with the longitudinal rails.

7. The robotic maintenance device of claim 6, characterized in that the at least three pairs of clamping actuators includes a front pair of clamping actuators positioned at one end of the main body, a rear pair of clamping actuators positioned at an opposite end of the main body, and a middle pair of clamping actuators located between the front pair and the rear pair, wherein the middle pair is rigidly coupled to the longitudinal rails and the front pair and the rear pair are movably coupled to the longitudinal rails so as to move in the longitudinal direction relative to the longitudinal rails.

8. The robotic maintenance device of claim 7, characterized in that the control system actuates the drive using the following steps to produce a movement of the maintenance device along the leading edge of the wind turbine blade: moving the rear pair of clamping actuators along the stroke direction away from engagement with opposite sides of the wind turbine blade; moving the rear pair of clamping actuators on the longitudinal rails along the longitudinal direction to a position adjacent the middle pair of clamping actuators; moving the rear pair of clamping actuators along the stroke direction towards the opposite sides of the wind turbine blade to clamp into engagement therewith; moving the middle pair of clamping actuators along the stroke direction away from engagement with opposite sides of the wind turbine blade; moving the middle pair of clamping actuators and the longitudinal rails along the longitudinal direction such that the middle pair of clamping actuators moves to a position adjacent the front pair of clamping actuators; moving the middle pair of clamping actuators along the stroke direction towards the opposite sides of the wind turbine blade to clamp into engagement therewith; moving the front pair of clamping actuators along the stroke direction away from engagement with opposite sides of the wind turbine blade; moving the front pair of clamping actuators on the longitudinal rails along the longitudinal direction to a position spaced apart from the middle pair of clamping actuators; and moving the front pair of clamping actuators along the stroke direction towards the opposite sides of the wind turbine blade to clamp into engagement therewith.

9. The robotic maintenance device of any of the preceding claims, characterized in that the maintenance device comprises at least one idler wheel mounted on an undersurface of the main body which faces towards the wind turbine blade, the at least one idler wheel configured to be rolled along the leading edge of the wind turbine blade to help support a weight of the maintenance device when the drive moves the maintenance device along the wind turbine blade.

10. The robotic maintenance device of any of the preceding claims, characterized in that the control system comprises at least one camera to provide visual feedback on an operational state of the maintenance device and components thereof.

11. The robotic maintenance device of claim 10, characterized in that the at least one camera of the control system includes: an overview camera mounted on a mast extending upwardly from the main body and configured to provide a complete overview of the maintenance device and current operation thereof; and a scanning camera mounted on the articulated arm and configured to image the surface in the vicinity of the leading edge.

12. The robotic maintenance device of any of the preceding claims, characterized in that the articulated arm includes a series of arm portions and joints enabling a free end of the articulated arm to reach any portion of the leading edge and the opposite sides of the wind turbine blade to conduct maintenance or repair actions.

13. The robotic maintenance device of claim 12, characterized in that the free end of the articulated arm includes an interface element configured to mechanically and electrically couple with corresponding interfaces provided on the tool heads.

14. A method for automatically repairing damage around a leading edge (22) of a wind turbine blade (20) on a wind turbine (10), the method characterized by: positioning a robotic maintenance device (40) having a main body (42), a vision system (56), an articulated arm (48), and a drive (100) by operating the drive to move the main body along the leading edge of the wind turbine blade such that the articulated arm can move into position at a location containing damage on the wind turbine blade; scanning the wind turbine blade with the vision system to produce image data confirming a location and severity of damage on the wind turbine blade; calculating a movement path for each of a cleaning/abrading tool head (70) and a coating applicator tool head (80) based on the location and severity of the damage; coupling the cleaning/abrading tool head to the articulated arm and using the cleaning/abrading tool head to sand down a surface (30) of the wind turbine blade around the damage and subsequently clean the surface to prepare same for repair; and coupling the coating applicator tool head to the articulated arm and using the coating applicator tool head to apply layers of a coating to the surface of the wind turbine blade, thereby repairing the damage on the wind turbine blade.

15. The method of claim 14, further characterized by: operating the wind turbine to move one of the wind turbine blades to a generally horizontal orientation; and pitching the wind turbine blade in the generally horizontal orientation such that the leading edge of the blade is oriented to face vertically upward, thereby placing the blade in position to receive the robotic maintenance device.

16. The method of claim 14 or 15, wherein the drive includes at least three pairs of clamping actuators connected to first and second body portions of the main body that extend towards opposite sides of the leading edge when the maintenance device is mounted on the wind turbine blade, and operating the drive is further characterized by: actuating each pair of the clamping actuators to selectively move along a stroke direction into and out of clamped engagement with opposite sides of the wind turbine blade; and moving each pair of the clamping actuators along a longitudinal direction towards and away from other pairs of clamping actuators.

17. The method of claim 16, wherein the drive includes linear actuators coupled to each of the clamping actuators, and operating the drive is further characterized by: using some of the linear actuators to move the clamping actuators along the stroke direction relative to opposite sides of the wind turbine blade; and using some others of the linear actuators to move a pair of the clamping actuators along the longitudinal direction relative to the other pairs of clamping actuators.

18. The method of claim 16 or 17, characterized by: maintaining at least two of the pairs of clamping actuators in clamped engagement with the wind turbine blade at all times to continuously secure the maintenance device on the wind turbine blade during movement along the leading edge and during maintenance and repair actions.

19. The method of any of claims 16-18, wherein the drive includes a longitudinal rail connected to each of the first and second body portions, the at least three pairs of clamping actuators includes a front pair of clamping actuators positioned at one end of the main body, a rear pair of clamping actuators positioned at an opposite end of the main body, and a middle pair of clamping actuators located between the front pair and rear pair, and operating the drive is further characterized by: moving the rear pair of clamping actuators along the stroke direction away from engagement with opposite sides of the wind turbine blade; moving the rear pair of clamping actuators on the longitudinal rails along the longitudinal direction to a position adjacent the middle pair of clamping actuators; moving the rear pair of clamping actuators along the stroke direction towards the opposite sides of the wind turbine blade to clamp into engagement therewith; moving the middle pair of clamping actuators along the stroke direction away from engagement with opposite sides of the wind turbine blade; moving the middle pair of clamping actuators and the longitudinal rails along the longitudinal direction such that the middle pair of clamping actuators moves to a position adjacent the front pair of clamping actuators; moving the middle pair of clamping actuators along the stroke direction towards the opposite sides of the wind turbine blade to clamp into engagement therewith; moving the front pair of clamping actuators along the stroke direction away from engagement with opposite sides of the wind turbine blade; moving the front pair of clamping actuators on the longitudinal rails along the longitudinal direction to a position spaced apart from the middle pair of clamping actuators; and moving the front pair of clamping actuators along the stroke direction towards the opposite sides of the wind turbine blade to clamp into engagement therewith.

20. The method of any of claims 14-19, further characterized by: scanning the wind turbine blade with the vision system after using the cleaning/abrading tool head and the coating applicator tool head to confirm whether further repair actions are necessary at the location containing damage on the wind turbine blade.

21. The method of any of claims 14-20, further characterized by: scanning the wind turbine blade with the vision system after using the cleaning/abrading tool head but before using the coating applicator tool head to confirm whether the movement path for the coating applicator tool head needs to be adjusted based on material removal by the cleaning/abrading tool head.

22. The method of any of claims 14-21 , wherein the vision system further includes cameras configured to image operations of the maintenance device and the wind turbine blade, and the method is further characterized by: transmitting images from the cameras to an offsite operator that is not located on the wind turbine blade while the maintenance device operates; and modifying operation of the maintenance device based on commands received from the offsite operator.