Robotic maintenance device having repair material supply system and method for repairing leading edge damage on a wind turbine blade

Abstract

A robotic maintenance device (40) includes a repair material supply system (60) and is configured to repair damage (26) around the leading edge (22) of a wind turbine blade (20). The robotic maintenance device (40) includes an applicator tool (42) configured to apply and shape a coating (30) defined by a two-component repair material over the leading edge (22) of the blade (20). The repair material supply system (60) includes a purge valve (74) and a waste container (76) located downstream from a mixer (72). The purge valve (74) delivers an initial output from the mixer (72), which may include any or all of air, debris, and insufficiently mixed first and second components, into the waste container (76). By delivering the first amount of mixer output to the waste container (76) for a predetermined period of time after initiation of flow of components into the mixer (72), the purge valve (74) assures that the applicator tool (42) receives only a high-quality mixture of the two- component repair material mixed at the desired mix ratio.

Description

[0001] ROBOTIC MAINTENANCE DEVICE HAVING REPAIR MATERIAL SUPPLY SYSTEM AND METHOD FOR REPAIRING LEADING EDGE DAMAGE ON A WIND TURBINE BLADE

[0002] Technical Field

[0003] This application relates generally to wind turbines, and more particularly relates to a robotic maintenance device including a repair material supply system 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 / or manual repairs by rope access technicians.

[0004] Background

[0005] 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.

[0006] 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 rain, particulate matter, debris, or other items in the air, especially along the leading edge that is configured to face 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.

[0007] 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 fiber composites and the like. 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. WO2018 / 113875, for example.

[0008] 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 conduct 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 boomstyle lift. In all conventional methods, the wind turbine must be stopped and locked in 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.

[0009] In recent years, a desire has emerged to allow for some automated or semi- autonomous maintenance of wind turbine blades, to thereby improve the speed and / or precision of such a process. For example, several newer robotic maintenance devices have been developed that operate to conduct leading edge erosion repairs while the blade remains attached in position on the wind turbine. Operating such robotic maintenance devices at the high heights and ambient environmental conditions of wind turbine blades has presented additional technical problems with the automated solutions, including how to properly prepare and handle rapid-curing two-component mixtures that typically define the repair material used for correcting erosion damage on a blade. Thus, further improvements for maintenance and repair systems are desired.

[0010] Summary

[0011] 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 on a wind turbine. The robotic maintenance device includes a repair material supply system and an applicator tool for coating the leading edge of the wind turbine blade with a two-component repair material. The repair material supply system includes a cartridge actuator configured to receive two supply cartridges respectively containing first and second components of the two-component repair material. The cartridge actuator operates to push a flow of the first and second components into supply lines exiting the cartridge actuator. A mixer is connected to the supply lines and is configured to static mix the flow of the first and second components during flow through the mixer. The repair material supply system further includes a purge valve including an inlet connected to and receiving flow form the mixer, and also including a first outlet and a second outlet being selectively fluidically connected with the inlet by the purge valve moving between a first position and a second position. A waste container is connected to the first outlet of the purge valve, and an applicator supply line is connected to the second outlet of the purge valve for delivering two-component repair material to the applicator tool. A controller of the robotic maintenance device is configured to hold the purge valve in the first position such that a first portion of the two-component repair material delivered by the mixer is discharged into the waste container. The controller then switches the purge valve to the second position after a period of time, with the purge valve in the second position delivering the two- component repair material from the mixer to the applicator tool.

[0012] Several embodiments are now described in conjunction with the applicator tool of this invention, and it will be understood that each embodiment can stand on its own and / or be combined in any combination with the other features / steps in the following embodiments.

[0013] In one embodiment, the purge valve is a two-position valve configured to move between the first position and the second position. The purge valve may also be mechanically and / or electrically actuated by the robotic maintenance device to move linearly or rotationally from the first position to the second position.

[0014] In another embodiment, the controller of the robotic maintenance device operates a timer that measures a predetermined time in which the purge valve dispenses into the waste container. The controller then switches the purge valve to the second position only after the predetermined time has elapsed following a start of operation of the cartridge actuator.

[0015] In yet another embodiment, the controller of the robotic maintenance device receives sensor input measuring movement resistance at the cartridge actuator. The controller then starts the timer when the sensor input indicates that the cartridge actuator has started pushing the first and second components into the supply lines towards the mixer and the purge valve.

[0016] In a related embodiment, the predetermined time is selected to allow any air, debris, and insufficiently mixed first and second components exiting the mixer to be dispensed into the waste container. As a result, only completely mixed two-component repair material is delivered to the applicator tool.

[0017] In a further embodiment, the waste container is a disposable plastic bag sized to receive at least two minutes of initial output of air, debris, and / or first and second components delivered by flow through the mixer and caused by operation of the cartridge actuator.

[0018] In another embodiment, the two supply cartridges, the mixer, the purge valve, and the waste container are replaced with new components after one operation by the robotic maintenance device of delivering the two-component repair material onto the wind turbine blade. To this end, these components define a replaceable assembly defining a one-time use part of the repair material supply system.

[0019] In one embodiment, the robotic maintenance device further includes an abrading tool that is configured to pre-condition the leading edge of the wind turbine blade. The preconditioning is done by sanding or abrading as the robotic maintenance device moves along a length of the wind turbine blade.

[0020] In yet another embodiment, the applicator tool includes a spatula configured to receive the two-component repair material from the repair material supply system. The spatula is configured to shape the two-component repair material during dispensing onto the leading edge of the wind turbine blade at locations of the leading edge that were preconditioned by the abrading tool as the robotic maintenance device moves along the length of the wind turbine blade.

[0021] Embodiments of the present invention are also directed to a method for repairing damage around a leading edge of a wind turbine blade on a wind turbine. The method includes providing a robotic maintenance device onto the wind turbine blade, the robotic maintenance device including an applicator tool and a repair material supply system including a cartridge actuator, a mixer, and a purge valve. The method also includes moving the applicator tool along a working length at the leading edge of the wind turbine blade. The repair material supply system delivers a supply of mixed two-component repair material to the applicator tool. The method further includes coating the leading edge of the wind turbine blade with the two- component repair material using the applicator tool. The step of delivering the supply of mixed two-component repair material to the applicator tool further includes:

[0022] - operating the cartridge actuator to push a flow of two components to be mixed to the mixer;

[0023] - mixing the two components in the mixer to produce the two-component repair material, which is delivered into the purge valve;

[0024] - holding the purge valve in a first position such that a first portion of the two- component repair material delivered by the mixer is discharged into a waste container; and

[0025] - switching the purge valve to a second position after a period of time, with the purge valve in the second position delivering the two-component repair material from the mixer to the applicator tool.

[0026] In one embodiment, the purge valve is a two-position valve, and the step of switching the purge valve to the second position includes moving the purge valve from the first position to the second position. This step can further include mechanically and / or electrically actuating the purge valve to move linearly or rotationally from the first position to the second position by the robotic maintenance device.

[0027] In another embodiment, the step of delivering the supply of mixed two-component repair material to the applicator tool further includes operating a timer to measure a predetermined time in which the purge valve dispenses into the waste container. Thus, the controller switches the purge valve to the second position only after the predetermined time has elapsed following a start of operation of the cartridge actuator. In yet another embodiment, the step of delivering the supply of mixed two- component repair material to the applicator tool further includes measuring movement resistance at the cartridge actuator. This step further includes starting the timer when the measured movement resistance indicates that the cartridge actuator has started pushing first and second components defining the flow of two components towards the mixer and the purge valve.

[0028] In a further embodiment, the predetermined time is selected to allow all air, debris, and insufficiently mixed first and second components exiting the mixer to be dispensed into the waste container, thereby allowing only completely mixed two- component repair material to be delivered to the applicator tool.

[0029] In one embodiment, the waste container is sized to receive at least two minutes of initial output of air, debris, and / or first and second components delivered by flow through the mixer and caused by operation of the cartridge actuator.

[0030] In another embodiment, the method includes, after the step of coating the leading edge of the wind turbine blade using the applicator tool, removing and replacing each of two supply cartridges in the cartridge actuator, the mixer, the purge valve, and the waste container with new components at the robotic maintenance device.

[0031] In a further embodiment, the robotic maintenance device also includes an abrading tool, with the applicator tool including a spatula. The method then further includes pre-conditioning the leading edge of the wind turbine blade by sanding or abrading with the abrading tool while moving said abrading tool along the working length. The method also includes shaping the two-component repair material with the spatula during coating of the leading edge of the blade with the spatula, and specifically at locations of the leading edge that were pre-conditioned by the abrading tool.

[0032] The elements and steps described herein can be reconfigured and combined in many different combinations to achieve the desired technical effects for different styles of wind turbines and different repair systems, as may be needed in the art. Brief Description of the Drawings

[0033] 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.

[0034] Fig. 1 is a perspective view of a wind turbine, with one of the wind turbine blades held in a generally horizontal orientation as is done during maintenance actions according to embodiments of the invention.

[0035] 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.

[0036] Fig. 3 is an enlarged cross-sectional view of the wind turbine blade shown in Fig. 2 with a coating applied over the damaged region on the leading edge of the blade to make a repair of the erosion-type damage.

[0037] Fig. 4 is a top perspective view of a robotic maintenance device including a coating applicator tool head fed by a repair material supply system in accordance with embodiments of the present invention, the maintenance device being mounted in position on the leading edge of the wind turbine blade of Figs. 1 through 3.

[0038] Fig. 5 is a top perspective view similar to Fig. 4 but with the robotic maintenance device shown mostly in phantom to reveal additional components thereof.

[0039] Fig. 6 is a schematic block diagram showing components of the repair material supply system and the robotic maintenance device of Fig. 4.

[0040] Fig. 7A is a cross-sectional side view through the purge valve of the repair material supply system of Fig. 6, showing the purge valve in a first position.

[0041] Fig. 7B is a cross-sectional side view of the purge valve of Fig. 7A, showing the purge valve moved to a second position. Fig. 8 is a schematic flow chart showing several steps of a method for repairing damage around the leading edge of the wind turbine blade in accordance with embodiments of the present invention.

[0042] Detailed Description

[0043] With reference to Figs. 1 through 8, embodiments of a robotic (automated or semi- autonomous) maintenance device having a repair material supply system and a method for repairing damage around a leading edge of a wind turbine blade are shown in detail. The repair material supply system is configured to prepare and deliver a mixed two-component repair material for application by an applicator tool as this tool is moved along a length of the blade, for thereby repairing erosion damage to the outer skin of the wind turbine blade. As will be explained in further detail below, in one embodiment, the repair material supply system now includes a purge valve located between a mixer and the applicator tool, the purge valve being controlled to dispense an initial flow of the two components moving through the mixer into a waste container so as to avoid supplying the applicator tool with (a) any repair material fouled by air or debris or (b) any repair material that is not sufficiently mixed at a correct / desired mix ratio of the two components. As the two-component repair material for such applications of wind turbine repair is designed to be quickly cured (typically within about 120 seconds of mixing / application), it is desirable to assure a homogenous mixture of the two-component repair material be applied by the applicator tool during the entire operation and movement along the length of the wind turbine blade. Thus, the provision of the purge valve and its operation enables a more consistent and reliable application of the two-component repair material and a significantly lowered likelihood that the repair coating will fail to sufficiently correct the erosion-type damage. Each of these aspects improves the functionality and operations of the robotic maintenance device, and each will be described in additional detail below.

[0044] 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 robotic maintenance device may be deemed a routine maintenance action that occurs before a blade is "damaged" in such contexts. In this regard, it will be understood that within the context of this application, the robotic 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 robotic maintenance device is also capable of providing more thorough repairs after damage is caused on the blade.

[0045] Turning with reference to Fig. 1 , a wind turbine 10 is shown and includes 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. 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 repair material supply system in accordance with embodiments disclosed herein improves the repair process to make automated or semi-automated repairs with the robotic maintenance device more efficient and less time-consuming as will be set forth in detail below.

[0046] 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 of the blade 20. Accordingly, while the robotic maintenance device is configured to repair damage along the leading edge 22 of the blade 20, this device may also be capable of conducting maintenance and repair actions elsewhere 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 may become 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 of in Fig. 2, it will be understood that the erosion damage 26 may define differing levels of severity based on how deep the damage 26 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. By identifying and correcting such lower levels of erosion damage 26 promptly by maintenance-style "repair actions," more significant damage of the blade 20 can be avoided along with higher operational downtime caused by the more significant damage.

[0047] Fig. 3 illustrates a repaired section of a wind turbine blade 20 having damage 26 on the leading edge 22 of the blade 20. The repaired section includes a shaped coating 30 of material that has been applied over the damage 26 on the leading edge 22 of the blade 20, in accordance with embodiments of this invention. The coating 30 is configured to define a new outer surface 32 that thereafter interacts with the air flowing over the blade 20 during later operations of the wind turbine 10. As such, the coating 30 corrects and covers / fills in the damage 26 on the wind turbine blade 20 and prevents or reduces the likelihood of the damage 26 further advancing, such as to a higher category of damage. In that regard, the coating 30 is shaped so as to minimize any negative impacts of the repair on the aerodynamic performance on the wind turbine blade 20 during use. The coating 30 is shaped to allow the new outer surface 32 to merge with the original outer surface 34 to minimize disruptions of the air flow over the blade 20.

[0048] With continued reference to Fig. 3, the coating 30 is thus typically configured to be at a maximum thickness at or about the leading edge 22 of the blade 20 and then decrease in thickness in a direction away from the leading edge 22 and toward the trailing edge (not shown) of the blade 20 along both of the existing outer surfaces 34 (i.e. , leeward and windward sides) of the blade 20. More particularly, the thickness of the coating 30 merges with the outer surface 34 of the leeward side at a first chamfer line 36 and the windward side at a second chamfer line 38. The first and second chamfer lines 36, 38 extend generally parallel to and proximate the leading edge 22 of the wind turbine blade 20 and are formed by one or more chamfer arms of the applicator tool. Preferably, the thickness of the coating 30 should decay to substantially zero at the first and second chamfer lines 36, 38. This allows the coating 30 to merge into the existing surfaces 34 of the blade 20 in a smooth manner, thereby minimizing the disruption of the air flow in the transition from the outer surface 32 of the coating 30 to the original outer surfaces 34 of the blade 20.

[0049] In an exemplary embodiment, the coating 30 may be formed from a two-component repair material defined by an epoxy or a polyurethane, but other materials may also be possible. The robotic maintenance device in accordance with embodiments of the invention aids in providing a precise and high-quality coating 30 on the leading edge 22 of the wind turbine blade 20 having the shape and features as described above. To this end, a homogenous mixture of the two-component repair material is applied to assure a consistent repair material quality along all portions of the leading edge 22 of the blade 20.

[0050] Fig. 4 provides an overview of an exemplary robotic maintenance device 40 equipped with an applicator tool 42 and a repair material supply system 60 in accordance with embodiments of this invention. The robotic maintenance device 40 shown in Figs. 4 and 5 is just one example of such an automated repair device, and it will be understood that the repair material supply system 60 and the underlying methods of operation can be performed by other types of automated devices and robotic devices in other embodiments consistent with the scope of the present invention. However, some basic components of this example of the robotic maintenance device 40 will now be described as pertinent background environment for how the repair material supply system 60 and the applicator tool 42 perform their functions.

[0051] The maintenance device 40 as shown in Fig. 4 includes a main body 44 (also referred to as a main chassis) that extends between a first end 46 and a second end 48. As shown, the maintenance device is configured to align with and extend along the leading edge 22 of the blade 20 when mounted on the blade 20. The first end 46 of the main body 44 includes a tool head 50 configured to support the applicator tool 42 over the leading edge 22 of the blade 20, as shown in this Figure. The applicator tool 42 is operatively coupled (e.g., mechanically and electrically) with the robotic maintenance device 40 via the tool head 50. In this regard, the tool head 50 and main body 44 of the maintenance device 40 may house components required to mechanically and electrically operate the applicator tool 42 and associated components. The maintenance device 40 and its components are shown in schematic form in these views except where necessary to illustrate particular features related to the aspects of the present invention. It will be appreciated that the wind turbine 10 is halted with the blade 20 to be worked upon in a generally horizontal orientation (as shown in Fig. 1 ) with the blade 20 pitched so that the leading edge 22 faces upwardly such that the maintenance device 40 can then be placed upon the blade 20 as shown in this Figure. 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 (e.g., UAV). The main body 44 generally defines a framework for other components of the maintenance device 40 to be mounted on, as set forth in the following description.

[0052] The maintenance device 40 also includes a controller or control system 52 shown schematically in Fig. 4 and implemented on known hardware and software platforms. The control system 52 is operatively connected to the components of the maintenance device 40, including the applicator tool 42 and associated components, and at least a movement drive (not shown in detail) for the maintenance device 40, to thereby operate these elements. More particularly, the control system 52 is capable of responding to inputs from components of the maintenance device 40 and applicator tool 42 and / or from an offsite operator to modify or initiate the actions taken by the maintenance device 40. More particularly, the actions of the maintenance device 40 and applicator tool 42 may be modified based on real-time feedback or inputs detected by the maintenance device 40 during repair operations.

[0053] To stabilize the maintenance device 40 as it moves along the leading edge 22 during repair operations, the maintenance device 40 also includes two or more wheels 56 connected to the main body 44 of the maintenance device 40, as shown in Fig. 4. The wheels 56 are connected to an underside of the main body 44 via respective support arms 58 and steady movement of the maintenance device 40 as it moves along the wind turbine blade 20. The support arms 58 may be curved to conform to the shape of the wind turbine blade 20. The curvature of the support arms 58 results in a predictable contact point between the wheels 56 and the surfaces 34 of the wind turbine blade 20, which is preferably below the damaged area 26. The wheels 56 can freely rotate along the surface 34 of the blade 20 in response to movements of the maintenance device 40 generated by the movement drive(s). The wheels 56 help support a weight of the maintenance device 40 on the blade 20 such that the entire weight is not applied to the movement drive(s) and its elements. These wheels 56 may be formed from a plastics material or any other suitable material, typically a moderate to low-friction material to help avoid any damage upon engagement with the blade 20. The wheels 56 also prevent tipping of the maintenance device 40 to either side of the blade 20. The plurality of wheels 56 in combination with the movement drive(s) are configured to space the applicator tool 42 over the leading edge 22 for repair operations. Moreover, the wheels 56 and movement drive(s) produce a steady movement of the maintenance device 40 along the blade 20 during repair and maintenance actions. To this end, it will be understood that any number of wheels 56 and movement drives may be provided in other embodiments.

[0054] Additionally, a power supply 62 such as a battery pack may be mounted on the maintenance device 40 for supplying power to components of the maintenance device 40 such as the controller 52, the repair material supply system 60, the drive system, and the applicator tool 42, for example. The power supply 62 may be configured to power those components and systems so that the maintenance device 40 can repair an entire leading edge 22 of a wind turbine blade 20, for example. The power supply 62 is shown schematically in Fig. 4. The power supply 62 may also be used to provide operating power to additional elements or modules that may be connected to the maintenance device 40 as well.

[0055] Fig. 5 provides a similar overview of the robotic maintenance device 40 but with the main body 44 shown in phantom to reveal additional internal components not visible in Fig. 4. In one embodiment, the maintenance device 40 also includes a cleaning / abrading tool 64 that is configured to sand down the surface of the wind turbine blade 20 containing damage 26 and then clean that surface to prepare it for repair. The cleaning / abrading tool 64 is shown in Fig. 5 and may be located on the underside of the main body 44 of the maintenance device 40, for example. As shown, the abrading tool 64 can include a plurality of sanding brushes that are rapidly rotated to abrade and / or cut away (by sanding action) rough edges and irregular sections caused by the erosion damage 26, thereby preparing a smoother contoured surface for receiving the two-component repair material via coating 30. The abrading tool 64 is located behind the tool head 50 such that the robotic maintenance device 40 can run the abrading tool 64 over the leading edge 22 just before the applicator tool 42 moves over this same portion of the leading edge 22, e.g., to precondition the surface just before the coating 30 is applied.

[0056] Once the damaged surface is prepared with the cleaning / abrading tool 64, the applicator tool 42 is used to apply the coating 30 to the prepared surface to fill in damaged areas 26 and thereby repair the blade 20. The applicator tool 42 in this embodiment includes a spatula configured to receive the two-component repair material from the repair material supply system 60 and first and second chamfer arms that can selectively press on the exterior of the spatula on opposing sides of the leading edge 22, each of these visible in Fig. 5. To briefly describe an overview of these elements and their function in this embodiment, as the applicator tool 42 moves, the coating material 30 is forced into a gap defined toward the front edge of the spatula and is essentially extruded from an opening at the front edge. In this regard, the height of the coating material, or thickness, is dictated by the height profile of the opening. A drive cylinder continues to apply a driving force on the first and second chamfer arms to maintain their engagement with the spatula, which helps the spatula form the first and second chamfer lines 36, 38. The coating 30 applied to the wind turbine blade 20 extends between the first and second chamfer lines 36, 38 to cover and fill in the erosion damage 26, as shown in Fig. 3. The chamfer arms may be adjusted to position the first and second chamfer lines 36, 38 of the shaped coating proximate edges of where the exterior surface 34 has been sanded, to thereby reduce the likelihood that the coating 30 will slip or have a bonding failure on the blade 20. It should be understood that after the coating 30 has dried or cured, the applicator tool 42 may be used to make additional passes over the damage 26 on the leading edge 22 of the blade 20. In this way, the final coating 30 may be comprised of a plurality of layers, with each layer applied using the applicator tool 42 as described above.

[0057] The robotic maintenance device 40 may include additional components not shown in these overview drawings, including but not limited to, a vision system with camera or sensors that are mounted on opposite ends of the main body 44 to confirm damaged areas on the blade 20 and the quality / sufficiency of the repair provided by the coating 30. Such additional components and further details regarding the applicator tool 42 and abrading tool 64 (briefly described above) can be understood from WO 2023 / 280362 A1 , for example. Further examples of robotic maintenance devices are, for example, disclosed in WO 2021 / 121521 A1 and WO 2023 / 280360, and such robotic maintenance devices may be used in other embodiments with the repair material supply system developed in the present invention. Further details of any exemplary robotic maintenance device can be understood from those prior patent applications in combination with the description provided herein.

[0058] Figs. 6 and 7A-7B illustrate the repair material supply system 60 and some components thereof in accordance with one embodiment of the invention. As initially noted above, the repair material supply system 60 includes a purge valve 74 that helps assure that a consistent, desirable quality mixture of the two-component repair material is delivered to the applicator tool 42 during operations of the robotic maintenance device 40. As such, any air or debris that may be present in the repair material supply system 60 originally does not foul the two-component repair material that is actually applied to make the coating 30 on the wind turbine blade 20. In Fig. 6, the components defining the repair material supply system 60 are shown in a block diagram. The repair material supply system 60 includes a cartridge actuator 70 connected to a mixer 72, which is then connected to the purge valve 74, with the purge valve 74 connected to and selectively discharging to either a waste container 76 or the applicator tool 42. Each of these elements is now described in some further detail.

[0059] The cartridge actuator 70 is configured to receive two supply cartridges respectively containing first and second components that are mixed to make the two-component repair material. The cartridge actuator may define a housing for receiving the two supply cartridges (which, as an aside, may be independent elements or connected together at exterior housings for convenience), and a drive mechanism for applying a force to each of the two supply cartridges. In one such example, the drive mechanism includes moveable pistons that are driven to press on a plunger or similar element of the two supply cartridges, thereby to force a flow of the first and second components out of an opposing end of the supply cartridges. For example, the first component is forced to flow into a first component supply line 78a extending between the cartridge actuator 70 and the mixer 72, while the second component is forced to flow into a second component supply line 78b extending between the cartridge actuator 70 and the mixer 72. As will be described further below, the two supply cartridges and the first and second component supply lines 78a, 78b define part of an integrated replaceable assembly that can be discarded after use by the robotic maintenance device 40, but the remainder of the cartridge actuator 70 is reusable for later operations (e.g., the pistons and drive mechanism can be reversed to an original position so that a new set of two supply cartridges can be loaded in for a later operation). Alternative types of cartridge actuators may also be used with different robotic maintenance devices in other embodiments of the invention, so long as these actuate an initial flow of the first and second components towards the mixer 72. Furthermore, in other alternatives, the two supply cartridges may be at least partially pressurized to help discharge the flow of the first and second components from the cartridge actuator 70 (the actuation or drive by the actuator 70 may take a different form, in such versions). The mixer 72 is a static mixer element that includes a sequence of baffles defining flow passages that force incoming fluid (first and second components) to fold over one another and thoroughly mix (by static mixing) during travel along a longitudinal length of the mixer element. As the mixed fluid will cure and solidify after a relatively short period of time, if flow is not present, the mixer 72 is also included as part of the replaceable assembly initially described above. The mixer 72 may take any number of various forms, so long as the structure within is designed to cause a complete mixing of input components delivered in this case from the first and second component supply lines 78a, 78b. The mixer 72 is connected at an opposite end of these supply lines to a mixer output line 80, which delivers output from the mixer 72 to the purge valve 74 as shown in Fig. 6. After the mixing, the resulting two-component repair material has a suitable viscosity that allows this material to flow under the influence of gravity and surface tension effects to form a smooth and continuous coating 30, e.g., at the applicator tool 42 as described briefly above.

[0060] The purge valve 74 of the embodiments of this invention is located in the repair material supply system 60 so as to receive the flow through mixer output line 80 and selectively direct it to either a discharge line 82 leading to the waste container 76 or to an applicator supply line 84 leading to the applicator tool 42. One example of the specific structure of the purge valve 74 is shown in Figs. 7A and 7B. As shown in these views, the purge valve 74 is a two-position valve that is configured to move from a first position, shown in Fig. 7A, to a second position, shown in Fig. 7B. As will be readily understood, the generally linear movement between these first and second positions may be modified in other embodiments of the purge valve 74 without departing from the scope of the invention, so long as the flow coming from the mixer output line 80 is selectively directed to just one of two outlets from the purge valve 74.

[0061] With continued reference to the example shown in Figs. 7A and 7B, the purge valve 74 includes a valve body 90 carrying a valve member 92 therein. The valve body 90 includes an inlet 94 on one side that receives flow from the mixer output line 80. The valve body 90 further includes a first outlet 96 and a second outlet 98 in parallel to one another and located on an opposite side from the valve member 92. The valve member 92 in this embodiment is a generally solid member filling a chamber within the valve body 90, but the valve member 92 includes a flow passage 100 formed about its periphery that can be moved to fluid ically connect the inlet 94 with just one of the first and second outlets 96, 98. The valve member 92 and / or the valve body 90 carry appropriate seal members to assure that the flow through the purge valve 74 is directed from the inlet 94 to one of the first and second outlets 96, 98. In the first position shown in Fig. 7A, the flow passage 100 of the valve member 92 is located to put the inlet 94 into fluid communication with the first outlet 96, and this first outlet 96 is connected to the aforementioned discharge line 82 leading to the waste container 76. As such, a flow through the purge valve 74 in the first position is shown by the flow arrows 102, which allows output from the mixer 72 to flow into the waste container 76 for the reasons set forth in detail herein.

[0062] Then when it is desired to move the output flow from the mixer 72 to the applicator tool 42, the purge valve 74 is moved to the second position as shown in Fig. 7B. As shown in this view, the valve member 92 has been moved generally linearly and to the right as shown by movement arrow 106 such that the flow passage 100 of the valve member 92 is moved and now fluid ically couples the inlet 94 with the second outlet 98. In this second position, a flow through the purge valve 74 is shown by the flow arrows 104, which allows output from the mixer 72 to flow to the applicator tool 42 (via the applicator supply line 84 as noted in Fig. 7 B). The movement of the valve member 92 from first to second positions as shown by arrow 106 can be mechanically and / or electrically actuated by the robotic maintenance device 40, in various manners as will be readily understood to those skilled in this art of valves and flow mechanisms. The specific structures and movements / operations of the purge valve 74 may be modified from the schematic illustrations shown in Figs. 7A and 7B in other embodiments of the invention, but only so long as the purge valve 74 continues to provide the flow switching and directing function described throughout this disclosure.

[0063] For example, the “linear” movement two-position valve could be replaced with a three- way ball valve or some other known valve structure that operates to selectively directing flow into one of two outlets (e.g., herein generically referred to as a “two- position valve”). The mechanical and / or electrical actuation of the purge valve 74 by the robotic maintenance device 40 may be a rotational movement or some other kind of movement than the linear movement example shown in the structure example provided in Figs. 7A and 7B. Other alternative designs will be readily understood by those skilled in the art for performing the necessary functions described herein of the purge valve 74.

[0064] Returning with reference to Fig. 6, the repair material supply system 60 also includes a sensor 86 operatively communicating with the controller 52 of the robotic maintenance device 40. The sensor 86 operates to determine when the cartridge actuator 70 has begun operations to force a flow of the first and second components into and through the mixer 72. In one example, the sensor 86 can measure a movement resistance encountered by the drive mechanism operating the piston type drives in the cartridge actuator 70. When the movement resistance increases over a threshold that can be pre-programmed into the controller 52, it can be identified that the cartridge actuator 70 is now forcing a flow of first and second components out of the supply cartridges. This sensor input can be used in the control process for the purge valve 74 as described further below.

[0065] The waste container 76 connected to the purge valve 74 by the discharge line 82 may be defined in one embodiment as a sealed waste container. In one example, the sealed waste container 76 is defined by a closed plastic bag-like receptacle or the like. Such a plastic bag receptacle can be formed to be disposable following a repair operation performed using the repair material supply system 60 and the robotic maintenance device 40. The plastic bag receptacle or any other type of waste container 76 used is sized to receive at least two minutes of initial output of air, debris, and first and second components (mixed or unmixed) delivered by flow through the mixer 72 and the purge valve 74 at the beginning of an operational / repair cycle. Advantageously, the waste container 76 of such embodiments contains such “undesirable” or initial output from the supply cartridges for later disposal and keeps such from escaping into the ambient environment such as falling onto the wind turbine blade 20. The use of the waste container 76 for these purposes has been proven in testing to be more desirable than other solutions like maintaining some initial amount of flow in a fillable bladder located upstream or downstream of the mixer 72, as such bladder-type solutions have a tendency to heat up and sometimes cause undesirable early curing of the two-component repair material within the system. It will be understood that the waste container 76 can be defined by other receptacles sized to receive such initial output in other embodiments, including non-sealed arrangements such as an open top container (but such alternatives are still configured to avoid having any air, debris, or first and second components be discharged into the environment around the robotic maintenance device 40). The waste container 76 is also included in the replaceable assembly described above along with the purge valve 74.

[0066] Having described the various components of the repair material supply system 60 and its purge valve 74, the operational process of repairing a wind turbine blade 20 while using these new components is now described in detail. It will be generally understood that the coating 30 (defined by the two-component repair material) is not discharged from the supply cartridges (the components thereof) until repair actions are to be done, as the mixed coating 30 can solidify in the supply lines or components of the repair material supply system 60 after being mixed for a period of time. In the context of wind turbine blade repair, the two-component repair material is typically designed as a quick curing material, e.g., curing in about 2 minutes or less, so as to finalize the coating 30 to repair the blade 20 shortly after the coating 30 is applied. This quick cure time minimizes any likelihood that the repair will be adversely affected by something blowing around in the ambient environment of the blade 20.

[0067] However, when using the two-component repair material, it is important to have the first and second components mixed at the desired mix ratio and fully mixed in order to assure the qualities of the coating 30 as well as the full curing of same. The first and second components have been found to typically define different viscosities from one another, which results in differing speeds of initial flow from the cartridge actuator 70 through the first and second component supply lines 78a, 78b when operation is initiated at the cartridge actuator 70. In addition, the filling level of each cartridge may differ slightly, causing the piston of the cartridge actuator 70 to contact the plunger of one of the cartridges before the other. In this regard, when the cartridge actuator 70 starts flow of the first and second components, it is typically true that one of the components will flow into the mixer 72 before the other component reaches the mixer 72. As such, the first portion of flow coming through the mixer 72 is often not at the desired mix ratio, and the quality of such initial flow can be undesirable. To address this potential problem, the purge valve 74 diverts the initial flow to allow the mixer 72 to be cleared of any air, debris, and / or insufficiently mixed first and second components. In the exemplary embodiment described herein, the purge valve 74 is controlled based on time. To this end, the controller 52 of the robotic maintenance device 40 operates a timer that measures a predetermined time in which the purge valve 74 directs flow into the waste container 76 at the beginning of a dispense cycle by the repair material supply system 60. The predetermined time is based on testing done on similar repair material supply systems and supply cartridges, this predetermined time being selected to allow all air, debris (these former items potentially being pre-existing in the mixer 72 before operation), and insufficiently-mixed first and second component initially flowing through the mixer 72 to go into the waste container 76 rather than to the applicator tool 42. Such predetermined time may be, for example, up to two minutes of operational output from the mixer 72. Within this predetermined time, the first and second components (regardless of variations in viscosity) have had sufficient time to both flow into and through the mixer 72 so as to produce the two-component repair material at the desired mix ratio. Once the predetermined time has elapsed as measured by the timer at controller 52, the controller 52 actuates movement of the purge valve 74 from the first position to the second position so as to then deliver the properly mixed two-component repair material to the applicator tool 42.

[0068] The time-based control of the operation of the purge valve 74 can be initiated using the sensor input from the sensor 86 described above. To this end, the sensor 86 can measure that the movement resistance applied against movement of the cartridge actuator 70 has increased sufficiently to indicate that flow of first and second components is being delivered into the mixer 72. Once this sensor input indicates the beginning of the flow, the timer can be run for the predetermined time to assure that any undesirable unmixed components and other initial output from the mixer 72 is discharged into the waste container 76 before flow begins to the applicator tool 42. Only after the predetermined time has elapsed since the beginning of flow initiation does the controller 52 operate the purge valve 74 to switch positions. Thus, the controller 52 can operate the purge valve 74 to perform the switching flow function as desired to achieve the technical benefits described herein for this dispensing cycle or process. Fig. 8 provides a process flowchart 200 that summarizes the operation of the repair material supply system 60 and the robotic maintenance device 40 consistent with the description above. Beginning at step 202, the process begins by actuating the two supply compartments (or cartridges) with the cartridge actuator 70 to deliver the first and second components to the mixer 72 and then to the purge valve 74. The controller 52 then starts the timer to measure whether the predetermined threshold time has elapsed since the initiation of flow (step 204). The purge valve 74 is held in the first position, as shown in Fig. 7A, which sends initial mixer output to the waste container 76 (step 206). Meanwhile, the controller 52 continuously or periodically checks whether the timer has expired to indicate that the predetermined threshold time has elapsed (step 208). If not, the process continues holding the purge valve 74 in the first position by returning to step 206, but if the timer has expired, the process moves on. The controller 52 (after the timer expires / the predetermined time elapses) then activates the purge valve 74 to switch to the second position as shown in Fig. 7B and therefore send mixer output to the applicator tool 42 (step 210). The applicator tool 42 then delivers the mixed two-component repair material onto the leading edge 22 of blade 20 to form the coating 30 and repair the leading-edge damage 26 (step 212). These steps shown in the process flow chart are performed generally as the robotic maintenance device 40 moves along a working length on the leading edge 22 of the blade 20, thereby enabling a repair of the damage 26 as noted with a consistent, desirable and / or high-quality repair material from the repair material supply system 60.

[0069] As noted above, the several components of the repair material supply system 60 are designed to be disposable and replaceable after these operational steps, e.g., these are one-time use components. To this end, the two supply cartridges, the mixer 72, the purge valve 74, and the waste container 76 as well as all lines between these elements form the replaceable assembly that is removed and replaced with new versions of these components after the operation described above at the robotic maintenance device 40. The replacement is necessary because these components are filled with some amounts of mixed components following the operational steps, and these mixed components will eventually cure or otherwise solidify to block further flow to and through these elements. The purge valve 74 and the waste container 76 developed for the repair material supply system 60 are formed with minimized cost and complexity to allow for cost-efficient operations and use of the robotic maintenance device 40. The addition of the purge valve 74 and the waste container 76 also advantageously require no further modifications to existing material supply components on the several known types of robotic maintenance devices 40.

[0070] The embodiments of the robotic maintenance device 40 including the repair material supply system 60 described above improve maintenance and repairs for erosion damage 26 at the leading edge 22 of the wind turbine blade 20. More particularly, the applicator tool 42 receives a proper two-component repair material from the supply system 60 for applying a coating 30 over the damage 26 at the leading edge 22 so as to arrest further deterioration of the wind turbine blade 20. The repair material supply system 60 is particularly advantageous when repairing wind turbine blades 20 in field conditions when, for example, the blades 20 remain attached to the rotor hub 18 at the top of the tower 12 of the wind turbine 10, which helps minimize operational downtime that is caused to conduct the maintenance and repair actions. Thus, even in less-than- ideal field conditions, the robotic maintenance device 40 is able to provide a high quality and precise repair of the damaged area 26 of the wind turbine blade 20.

[0071] 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. Moreover, the various features of the invention may be used alone or in any combination depending on the needs and preferences of the user, and the features described in the different embodiments are not dependent on one another for operation of the invention.

Claims

Claims1 . A robotic maintenance device (40) for repairing damage (26) around a leading edge (22) of a wind turbine blade (20) on a wind turbine (10), the robotic maintenance device (40) including a repair material supply system (60) and an applicator tool (42) for coating the leading edge (22) of the wind turbine blade (20) with a two-component repair material, and the repair material supply system (60) comprising: a cartridge actuator (70) configured to receive two supply cartridges respectively containing first and second components of the two-component repair material, the cartridge actuator (70) operating to push a flow of the first and second components into supply lines (78a, 78b) exiting the cartridge actuator (70); a mixer (72) connected to the supply lines (78a, 78b) and configured to mix the flow of the first and second components during flow through the mixer (72); a purge valve (74) including an inlet (94) connected to and receiving flow from the mixer (72), the purge valve (74) also including a first outlet (96) and a second outlet (98) being selectively fluid ically connected with the inlet (94) by the purge valve (74) moving between a first position and a second position; a waste container (76) connected to the first outlet (96) of the purge valve (74); and an applicator supply line (84) connected to the second outlet (98) of the purge valve (74) and configured to deliver two-component repair material to the applicator tool (42), wherein a controller (52) of the robotic maintenance device (40) is configured to hold the purge valve (74) in the first position such that a first portion of the two- component repair material delivered by the mixer (72) is discharged into the waste container (76), and then to switch the purge valve (74) to the second position after a period of time, with the purge valve (74) in the second position delivering the two- component repair material from the mixer (72) to the applicator tool (42).

2. The robotic maintenance device (40) with repair material supply system (60) according to claim 1 , characterized in that the purge valve (74) is a two-position valve configured to move between the first position and the second position.

3. The robotic maintenance device (40) with repair material supply system (60) according to claim 2, characterized in that the purge valve (74) is mechanically and / or electrically actuated by the robotic maintenance device (40) to move linearly or rotationally from the first position to the second position.

4. The robotic maintenance device (40) with repair material supply system (60) according to any of the preceding claims, characterized in that the controller (52) of the robotic maintenance device (40) operates a timer that measures a predetermined time in which the purge valve (74) dispenses into the waste container (76), such that the controller (52) switches the purge valve (74) to the second position only after the predetermined time has elapsed following a start of operation of the cartridge actuator (70).

5. The robotic maintenance device (40) with repair material supply system (60) according to claim 4, characterized in that the controller (52) of the robotic maintenance device (40) receives sensor input measuring movement resistance at the cartridge actuator (70), with the controller (52) starting the timer when the sensor input indicates that the cartridge actuator (70) has started pushing the first and second components into the supply lines (78a, 78b) towards the mixer (72) and the purge valve (74).

6. The robotic maintenance device (40) with repair material supply system (60) according to claim 4 or 5, characterized in that the predetermined time is selected to allow any air, debris, and insufficiently-mixed first and second components exiting the mixer (72) to be dispensed into the waste container (76), thereby allowing only completely-mixed two-component repair material to be delivered to the applicator tool (42).

7. The robotic maintenance device (40) with repair material supply system (60) according to any of the preceding claims, characterized in that the waste container (76) is a disposable plastic bag sized to receive at least two minutes of initial output of air, debris, and / or first and second components delivered by flow through the mixer (72) and caused by operation of the cartridge actuator (70).

8. The robotic maintenance device (40) with repair material supply system (60) according to any of the preceding claims, characterized in that the two supply cartridges, the mixer (72), the purge valve (74), and the waste container (76) are replaced with new components after one operation by the robotic maintenance device (40) of delivering the two-component repair material onto the wind turbine blade (20).

9. The robotic maintenance device (40) with repair material supply system (60) according to any of the preceding claims, wherein the robotic maintenance device (40) further comprises: an abrading tool (64) configured to pre-condition the leading edge (22) of the wind turbine blade (20) by sanding or abrading as the robotic maintenance device (40) moves along a length of the wind turbine blade (20).

10. The robotic maintenance device (40) with repair material supply system (60) according to claim 9, characterized in that the applicator tool (42) comprises: a spatula configured to receive the two-component repair material from the repair material supply system (60) and configured to shape the two-component repair material into a coating (30) during dispensing onto the leading edge (22) of the wind turbine blade (20) at locations of the leading edge (22) that were preconditioned by the abrading tool (64) as the robotic maintenance device (40) moves along the length of the wind turbine blade (20).

11. A method for repairing damage (26) around a leading edge (22) of a wind turbine blade (20) on a wind turbine (10), the method comprising: providing a robotic maintenance device (40) onto the wind turbine blade (20), the robotic maintenance device (40) including an applicator tool (42) and a repair material supply system (60) including a cartridge actuator (70), a mixer (72), and a purge valve (74); moving the applicator tool (42) along a working length at the leading edge (22) of the wind turbine blade (20); delivering, by the repair material supply system (60), a supply of mixed two- component repair material to the applicator tool (42); andcoating the leading edge (22) of the wind turbine blade (20) with the two- component repair material using the applicator tool (42), wherein the step of delivering the supply of mixed two-component repair material to the applicator tool (42) comprises: operating the cartridge actuator (70) to push a flow of two components to be mixed to the mixer (72); mixing the two components in the mixer (72) to produce the two- component repair material, which is delivered into the purge valve (74); holding the purge valve (74) in a first position such that a first portion of the two-component repair material delivered by the mixer (72) is discharged into a waste container (76); and switching the purge valve (74) to a second position after a period of time, with the purge valve (74) in the second position delivering the two-component repair material from the mixer (72) to the applicator tool (42).

12. The method according to claim 11 , wherein the purge valve (74) is a two- position valve, and the step of switching the purge valve (74) to the second position comprises: moving the purge valve (74) from the first position to the second position.

13. The method according to claim 12, wherein the step of switching the purge valve (74) to the second position comprises: mechanically and / or electrically actuating the purge valve (74) to move linearly or rotationally from the first position to the second position by the robotic maintenance device (40).

14. The method according to any of claims 11 through 13, wherein the step of delivering the supply of mixed two-component repair material to the applicator tool (42) further comprises: operating a timer to measure a predetermined time in which the purge valve (74) dispenses into the waste container (76), such that a controller (52) of the robotic maintenance device (40) switches the purge valve (74) to the second position only after the predetermined time has elapsed following a start of operation of the cartridge actuator (70).

15. The method according to claim 1 , wherein the step of delivering the supply of mixed two-component repair material to the applicator tool (42) further comprises: measuring movement resistance at the cartridge actuator (70); and starting the timer when the measured movement resistance indicates that the cartridge actuator (70) has started pushing first and second components defining the flow of two components towards the mixer (72) and the purge valve (74).

16. The method according to claim 14 or 15, characterized in that the predetermined time is selected to allow all air, debris, and insufficiently-mixed first and second components exiting the mixer (72) to be dispensed into the waste container (76), thereby allowing only completely-mixed two-component repair material to be delivered to the applicator tool (42).

17. The method according to any of claims 11 through 16, characterized in that the waste container (76) is sized to receive at least two minutes of initial output of air, debris, and / or first and second components delivered by flow through the mixer (72) and caused by operation of the cartridge actuator (70).

18. The method according to any of claims 11 through 17, further comprising, after the step of coating the leading edge (22) of the wind turbine blade (20) with the two-component repair material using the applicator tool (42): removing and replacing each of two supply cartridges in the cartridge actuator (70), the mixer (72), the purge valve (74), and the waste container (76) with new components at the robotic maintenance device (40).

19. The method according to any of claims 11 through 18, wherein the robotic maintenance device (40) further includes an abrading tool (64), the applicator tool (42) includes a spatula, and the method further comprises: pre-conditioning the leading edge (22) of the wind turbine blade (20) by sanding or abrading with the abrading tool (64) while moving said abrading tool (64) along the working length; and shaping the two-component repair material with the spatula during coating of the leading edge (22) of the wind turbine blade (20) with the spatula, specifically atlocations of the leading edge (22) that were pre-conditioned by the abrading tool

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