FIELD OF THE INVENTION
The present disclosure relates in general to wind turbine towers, and more particularly to methods of additively manufacturing wind turbine tower structures using an automated, tower-climbing additive printing device.
BACKGROUND OF THE INVENTION
Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture kinetic energy of wind using known foil principles. The rotor blades transmit the kinetic energy in the form of rotational energy so as to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
The wind turbine tower is generally constructed of steel tubes, pre-fabricated concrete sections, or combinations thereof. Further, the tubes and/or concrete sections are typically formed off-site, shipped on-site, and then arranged together to erect the tower. For example, one manufacturing method included forming pre¬cast concrete rings, shipping the rings to the site, arranging the rings atop one another, and then securing the rings together. As wind turbines continue to grow in size, however, conventional manufacturing methods are limited by transportation regulations that prohibit shipping of tower sections having a diameter greater than about 4 to 5 meters. Thus, certain tower manufacturing methods include forming a plurality of arc segments and securing the segments together on site to form the diameter of the tower, e.g. via bolting and/or welding. Such methods, however, require extensive labor and can be time-consuming. In view of the foregoing, the art is continually seeking improved methods for manufacturing wind turbine towers. Accordingly, the present disclosure is directed to methods for manufacturing wind turbine tower structures that address the aforementioned issues. In particular, the present disclosure is directed to

methods for additively manufacturing wind turbine tower structures on site using automated additive printing devices that climb the tower structure during printing.
BRIEF DESCRIPTION OF THE INVENTION
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In one aspect, the present disclosure is directed to an additive printing device for manufacturing a tower structure of a wind turbine. The additive printing device includes a central pole extending substantially along a vertical direction and a print head for selectively depositing cementitious material to form the tower structure. A support structure movably couples the print head to the central pole. In addition, a plurality of lift arms are mounted to the central pole which are extendable to engage a portion of the tower structure and raise the central pole. A plurality of stabilizer legs are mounted to the central pole and are movable to a support position to support the central pole.
In one embodiment, the present disclosure is directed to a method of manufacturing a tower structure of a wind turbine using an additive printing device. The additive printing device includes a central pole, a plurality of lift arms mounted to the central pole, a plurality of stabilizer legs mounted to the central pole, and a print head movably coupled to the central pole by a support arm. The method includes printing one or more support structures on an inner wall of the tower structure by depositing cementitious material using the print head and moving the support arm along the central pole. The method further includes positioning the plurality of lift arms to engage the one or more support structures, retracting the plurality of stabilizer legs, and extending the plurality of lift arms to raise the central pole. The method further includes positioning the plurality of stabilizer legs to engage the one or more support structures to support the central pole and printing additional layers of the tower structure.
According to still another embodiment, the present disclosure provides an additive printing device for manufacturing a structure. The additive printing device

includes a central pole extending substantially along a vertical direction and a print head for selectively depositing cementitious material to form the structure. A support structure movably couples the print head to the central pole and a plurality of lift arms are mounted to the central pole, the lift arms being extendable to engage a portion of the structure and raise the central pole. A plurality of stabilizer legs are pivotally mounted proximate a bottom of the central pole, the plurality of stabilizer legs being movable to an unfolded position to support the central pole. These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
A full and enabling disclosure of the present invention, including the best mode
thereof, directed to one of ordinary skill in the art, is set forth in the specification,
which makes reference to the appended figures, in which:
FIG. 1 illustrates a perspective view of one embodiment of a wind turbine
according to the present disclosure;
FIG. 2 illustrates a cross-sectional view of one embodiment of a tower structure of
a wind turbine according to the present disclosure;
FIG. 3 illustrates a schematic view of an additive printing device that may be used
to print the exemplary tower structure of FIG. 2 according to the present
disclosure;
FIG. 4 illustrates a step of a build process of an exemplary tower structure using
an exemplary additive printing device according to the present disclosure;
FIG. 5 illustrates another step of a build process of the exemplary tower structure
using the exemplary additive printing device according to the present disclosure;
FIG. 6 illustrates another step of a build process of the exemplary tower structure
using the exemplary additive printing device according to the present disclosure;
FIG. 7 illustrates another step of a build process of the exemplary tower structure

using the exemplary additive printing device according to the present disclosure; FIG. 8 illustrates another step of a build process of the exemplary tower structure using the exemplary additive printing device according to the present disclosure; FIG. 9 illustrates another step of a build process of the exemplary tower structure using the exemplary additive printing device according to the present disclosure; FIG. 10 illustrates a block diagram of one embodiment of a controller of an additive printing device according to the present disclosure; and FIG. 11 illustrates a flow diagram of one embodiment of a method for manufacturing a tower structure of a wind turbine according to the present disclosure.
Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Generally, the present disclosure is directed to an additive printing device and methods for manufacturing wind turbine towers using automated deposition of cementitious materials via technologies such as additive manufacturing, 3-D Printing, spray deposition, extrusion additive manufacturing, concrete printing, automated fiber deposition, as well as other techniques that utilize computer

numerical control and multiple degrees of freedom to deposit material. More specifically, methods of the present disclosure include using an automated additive printing device that "climbs" the tower structure during the printing process to form a tower structure out of concrete and at any desirable height without requiring a tall crane or otherwise being limited by manufacturing or logistics constraints common to prior manufacturing methods. Thus, the methods described herein provide many advantages not present in the prior art. For example, the present disclosure may permit on-site printing of tower structures having any desirable size (e.g., greater than four meters in diameter), thereby enabling the construction of larger tower structures and wind turbines. The methods also increase design flexibility, eliminate overall size restrictions, and permit the formation of tower structures having any desirable profile and cross sectional shape. The additive printing device may also utilize any suitable number of print heads to decrease manufacturing time. In addition, the support structures printed into the tower structure may be used for alternative purposes after construction of the tower is complete. For example, support structures or ledges may be formed large enough to serve as service platforms of the tower, ledges for door openings, etc. In addition, ledges may have defined openings to channel electrical power and signal lines or may also be used to support a ladder. Referring now to the drawings, FIG. 1 illustrates one embodiment of a wind turbine 10 according to the present disclosure. As shown, the wind turbine 10 includes a tower 12 extending from a foundation 15 or support surface with a nacelle 14 mounted atop the tower 12. A plurality of rotor blades 16 are mounted to a rotor hub 18, which is in turn connected to a main flange that turns a main rotor shaft. The wind turbine power generation and control components are housed within the nacelle 14. The view of FIG. 1 is provided for illustrative purposes only to place the present invention in an exemplary field of use. It should be appreciated that the invention is not limited to any particular type of wind turbine configuration. In addition, the present invention is not limited to use with wind turbine towers, but may be utilized in any application having concrete constructions and/or tall tower structures in addition to wind towers, including for

example homes, bridges, tall towers, and other aspects of the concrete industry. Further, the methods described herein may also apply to manufacturing any similar structure that benefits from the advantages described herein. Referring now to FIG. 2, tower structure 12 of a wind turbine 10 will be described in more detail according to an exemplary embodiment of the present subject matter. Specifically, FIG. 2 illustrates a partial, cross-sectional view of one embodiment of the tower structure 12 of the wind turbine 10 according to the present disclosure. As shown, the tower structure 12 defines a circumferential tower wall 20 having an outer surface 22 and an inner surface 24. Further, as shown, the circumferential tower wall 20 generally defines a hollow interior 26 that is commonly used to house various turbine components (e.g. a power converter, transformer, etc.) at various locations along the tower. In addition, as will be described in more detail below, the tower structure 12 is formed using additive manufacturing.
Moreover, as shown, the tower structure 12 is formed of a cementitious material 28 that is reinforced with one or more tensioning cables 30 (FIG. 2), such as elongated cables or wires, helical cables or wires, reinforcing bars (also referred to as rebar), and/or mesh. These tensioning cables 30 may be embedded in the cementitious material 28 during the printing process, as described in more detail below. As used herein, the cementitious material 28 may include any suitable workable paste that is configured to bind together after curing to form a structure. Suitable cementitious materials include, for example, concrete, pitch resin, asphalt, clay, cement, mortar, cementitious compositions, or similar materials or compositions.
According to exemplary embodiments of the present subject matter, an adhesive material (not shown) may be provided between one or more of the cementitious material 28 and the foundation 15, the cementitious material 28 and tensioning cables 30, or multiple layers of the cementitious material 28 and tensioning cables 30. Thus, the adhesive material may further supplement interlayer bonding between materials.

The adhesive material described herein may include, for example, cementitious material such as mortar, polymeric materials, and/or admixtures of cementitious material and polymeric material. Adhesive formulations that include cementitious material are referred to herein as "cementitious mortar." Cementitious mortar may include any cementitious material, which may be combined with fine aggregate. Cementitious mortar made using Portland cement and fine aggregate is sometimes referred to as "Portland cement mortar," or "OPC." Adhesive formulations that include an admixture of cementitious material and polymeric material are referred to herein as "polymeric mortar." Any cementitious material may be included in an admixture with a polymeric material, and optionally, fine aggregate. Adhesive formulations that include a polymeric material are referred to herein as "polymeric adhesive."
Exemplary polymeric materials that may be utilized in an adhesive formulation include may include any thermoplastic or thermosetting polymeric material, such as acrylic resins, poly epoxides, vinyl polymers (e.g., polyvinyl acetate (PVA), ethylene-vinyl acetate (EVA)), styrenes (e.g., styrene butadine), as well as copolymers or terpolymers thereof. Characteristics of exemplary polymeric materials are described in ASTM C1059 / C1059M-13, Standard Specification for Latex Agents for Bonding Fresh To Hardened Concrete.
Referring now generally to FIGS. 3 through 9 an additive printing device 40 will be described according to an exemplary embodiment of the present subject matter. Notably, all or part of tower structure 12 may be printed, layer-by-layer, using additive printing device 40, which may use any suitable mechanisms for depositing layers of additive material, such as concrete, to form tower structure 12. Thus, aspects of the present subject matter are directed to methods for manufacturing wind turbine towers via additive manufacturing. Additive manufacturing, as used herein, is generally understood to encompass processes used to synthesize three-dimensional objects in which successive layers of material are formed under computer control to create the objects. As such, objects of almost any size and/or shape can be produced from digital model data. It should further be understood that the additive manufacturing methods of the

present disclosure may encompass three degrees of freedom, as well as more than three degrees of freedom such that the printing techniques are not limited to printing stacked two-dimensional layers, but are also capable of printing curved and/or irregular shapes.
It should be understood that the additive printing device 40 described herein generally refers to any suitable additive printing device having one or more nozzles for depositing material (such as the cementitious material 28) onto a surface that is automatically controlled by a controller to form an object programmed within the computer (such as a CAD file). More specifically, as shown in FIG. 3 and described below, additive printing device 40 includes one or more print heads 42 having any suitable number of nozzles 44 and being independently movable to simultaneously print layers of tower structure 12. Referring still to FIGS. 3 through 9, additive printing device 40 will be described in more detail according to exemplary embodiments of the present subject matter. As shown, additive printing device 40 includes a central pole 46 that extends through the interior 26 of tower structure 12 along an axial direction A. According to the illustrated embodiment, central pole 46 is vertically oriented, such that the axial direction A is substantially parallel to the vertical direction V. It should be appreciated that as used herein, terms of approximation, such as "approximately," "substantially," or "about," refer to being within a ten percent margin of error. As explained in detail below, central pole 46 includes various components mounted thereon to facilitate the climbing or raising of central pole 46 within tower structure 12 while supporting one or more print heads 42 during the formation of tower structure 12.
Specifically, print heads 42 may be configured for selectively depositing cementitious material 28 to form tower structure 12 layer-by-layer. Additive printing device 40 may further include a support structure 48 that movably couples print head 42 to central pole 46. In general, support structure 48 may be any device, system, or mechanism that is coupled to central pole 46 and configured for moving one or more print heads 42 along a profile of tower structure 12 during the printing process. For example, support structure 48 may be

a robotic arm, a guide wire system, a telescoping support arm, lead screw mechanism, or any other suitable structure for supporting print heads 42. According to the illustrated embodiment, support structure 48 comprises a support arm 50 that extends substantially along a radial direction R (e.g., along a horizontal direction or perpendicular to the axial direction A) from central pole 46.
As illustrated, support arm 50 is mounted to central pole 46 by a rotary bearing 52. In addition, rotary bearing 52 is coupled to central pole 46 by a vertical rail 54 such that rotary bearing 52 (e.g., and thus support arm 50) are movable along the vertical direction V (see, e.g., FIGS. 1 and 2). More specifically, rotary bearing 52 may include an inner race 56 that is mounted within vertical rail 54 and is rotatably fixed relative to central pole 46. Notably, support arm 50 is mounted directly to outer race 58 of rotary bearing 52, and is thus rotatable relative to inner race 56 and central pole 46. It should be appreciated that other suitable bearing and/or coupling mechanisms may be used to rotatably join support arm 50 to central pole 46 while remaining within the scope of the present subject matter. Additive printing device 40 may include any suitable actuator or positioning mechanism (not shown) for moving inner race 56 of rotary bearing 52 along the vertical direction V from a bottom 60 of central pole 46 to a top 62 of central pole 46. In this regard, for example, inner race 56 may be coupled to one or more of a plurality of linear actuators, servomotors, track conveyor systems, etc. Alternatively, according to an exemplary embodiment, the positioning mechanism includes a ball screw linear slide that is driven by a servomotor (not shown). These positioning mechanisms are used only for the purposes of explaining aspects of the present subject matter and are not intended to be limiting in any manner.
In order to further facilitate improved positioning of print head 42, support arm 50 may further include a horizontal rail 64 which is configured for slidably receiving print head 42. In this regard, horizontal rail 64 may be similar to vertical rail 54 and support arm 50 may include any suitable positioning mechanism similar to those described above. In this regard, print head 42 may be moved along the radial

direction R toward and away from central pole 46 along support arm 50. Thus, by mounting support arm 50 onto central pole 46 using rotary bearing 52, print head 42 may be positioned at any suitable location within a horizontal plane to print a particular cross-section of tower structure 12.
Although FIG. 3 illustrates a single print head 42 including a single nozzle 44 for depositing cementitious material 28, it should be appreciated that according to alternative embodiments, any suitable number of support arms 50 may be used to support any suitable number of print heads and 42 having any suitable number and configuration of nozzles 44. For example, a support arm may extend from central pole 46 within each of four circumferential quadrants of tower structure 12 and may each support a separate print head 42. In this manner, the printing process may be expedited. In addition, support arms 50 may support other devices for facilitating construction of an improved tower structure 12, such as reinforcement depositing devices described below. Furthermore, according to exemplary embodiments, each nozzle 44 may be configured for depositing a different material, composition, or product.
In addition, although the exemplary embodiment illustrates a single horizontal support arm 50 supporting a single print head 42, it should be appreciated that other print mechanisms may extend from rotary bearing 52 according to alternative embodiments. For example, according to alternative embodiments, one or more flexible robotic arms (using linkage mechanisms or similar) may be mounted to rotary bearing 52 for positioning one or more nozzles at any suitable location within reach of the robotic arm. Such an embodiment would enable the printing of structures slightly taller than central pole 46.
During the printing process, various components, supports, and other features may be printed into or included in the cementitious material 28 used to print tower structure 12. For example, according to the exemplary embodiment, the printing process may include embedding one or more tensioning cables 30 at least partially within one or more of portions of tower structure 12. In this regard, as shown for example in FIG. 3, additive printing device 40 may include a cable supply module 66 that positions tensioning cable 30 at least partially within tower structure 12. It

should be understood that such cables 30 may extend along the entire height of the tower 12
(e.g., as shown in FIG. 2) or along only a portion of the tower height. According to an exemplary embodiment, as the tower structure 12 is being built up, the additive printing device 40 can alternate between depositing tensioning cables 30 using cable supply module 66 and printing the cementitious material 28 using nozzles 44. Alternatively, as illustrated in FIG. 3, cable supply module 66 may be positioned adjacent nozzle 44 and configured for unwinding or unrolling tensioning cable 30 or rebar into the print area prior to depositing cementitious material 28 such that the tensioning cable becomes embedded within or printed over with cementitious material 28. Alternatively, additive printing device 40 may include any other suitable features for compressing or embedding tensioning cable 30 into cementitious material 28 before it has solidified or cured. In alternative embodiments, the additive printing device 40 is configured to eject the cementitious material 28 with short polymer and/or metallic fibers or rings as reinforcements to improve the structural strength of the tower structure 12. Tensioning cables 30 may generally be configured for ensuring that the stresses in the cementitious material 28, e.g., concrete, may remain largely compressive. These cables 30 may be pretensioned and cementitious material 28 may be printed around the cables 30 or the printing process may define holes throughout tower structure 12 through which tensioning cables 30 may be placed after curing, and thereafter post-tensioned. In alternative embodiments, the additive printing device 40 may be configured to provide tension to the cable(s) 30 during printing of the tower structure 12. In such embodiments, additive printing device 40 may vary a tension of the one or more cables 30 as a function of a cross-section of the tower structure 12 during the printing process. Thus, such tensioning cables 30 are configured to manage tensile stresses of the tower structure 12. In another embodiment, the tower structure 12 may include, for example, a plurality of reinforcing bars that form a metal mesh (not shown) arranged in a cylindrical configuration to correspond to the shape of the tower structure 12. Further, the cylindrical metal mesh can be embedded into the cementitious

material 28 of the tower structure 12 before the material 28 cures and periodically along the height of the tower 12. In addition, the additive printing device 40 is configured to print the cementitious material 28 in a manner that accounts for the cure rate thereof such that the tower wall 20, as it is being formed, can bond to itself. In addition, the additive printing device 40 is configured to print the tower structure 12 in a manner such that it can withstand the weight of the wall 20 as the additively-formed cementitious material 28 can be weak during printing. Notably, if central pole 46 is fixed in its vertical position, the height of the tower structure 12 is limited to the height of central pole 46 (or slightly higher if a robotic arm extends from rotary bearing 52). Therefore, in order to build tower structures 12 having any suitable height, aspects of the present subject matter are directed to facilitating the raising of central pole 46 within tower structure 12 as additive material is printed layer-by-layer. Specifically, the features described below permit central pole 46 (and thus additive printing device 40 and print heads 42) to "climb" the walls of tower structure 12 during the build process. After tower structure 12 of a desired height is completed, additive printing device 40 may then descend or climb back down tower structure 12. Referring still to FIGS. 3 through 9, additive printing device 40 includes a plurality of lift arms 70 that are mounted to central pole 46. In general, lift arms 70 are configured move and engage tower structure 12 to facilitate the climbing process. More specifically, lift arms 70 may be pivoted between a folded position (e.g., as shown in FIG. 4) and an unfolded position (e.g., as shown in FIGS. 3 and 5). In addition, lift arms 70 may move between a retracted position (e.g., as shown in FIG. 5) and an extended position (e.g., as shown in FIG. 6) to engage a portion of the tower structure 12 and raise central pole 46. Although the process herein is used to describe the method of raising central pole 46 during the printing process, it should be appreciated that this process may be reversed to lower central pole 46 within tower structure 12 after construction is completed. Lift arms 70 may include any suitable mechanism or device for moving lift arms 70 between the folded and unfolded position. In addition, lift arms 70 may include any suitable mechanism or device for extending or retracting a contact pad 72 of

each lift arm 70. For example, according to the illustrated embodiment, each of the plurality of lift arms 70 comprises a hydraulic cylinder 74 and a piston rod 76. At the end of piston rod 76, contact pad 72 is mounted and generally configured for engaging tower structure 12, as we described in more detail below. Thus, when lift arms 70 are in the unfolded position, they may be hydraulically actuated to extend piston rod 76 and contact pad 72 to engage tower structure 12 and raise central pole 46.
It should be appreciated that any suitable number of lift arms 70 may be used to support and raise central pole 46. For example according to exemplary embodiments at least three lift arms 70, or more preferably four lift arms 70 are mounted to central pole 46 and operate simultaneously to lift central pole 46. In addition, it should be appreciated that other lift mechanisms are possible and within the scope of the present subject matter. Furthermore, it should be appreciated that according to exemplary embodiments, lift arms 70 may not be pivotally mounted to central pole, e.g., so long as hydraulic cylinder 74 may extend piston rod 76 sufficiently to engage tower structure 12. Additive printing device 40 may further include a plurality of stabilizer legs 80 that are mounted proximate bottom 60 of central pole 46 and are generally configured for supporting central pole 46 during the printing process. For example, according to the illustrated embodiment, stabilizer legs 80 are pivotable, in a manner similar to lift arms 70, for moving between a folded position or retracted position (e.g., as shown in FIG. 6) and an unfolded position or a support position (e.g., as shown in FIGS. 3 through 5). Stabilizer legs 80 may terminate in a support pad 82 configured to engage the ground, the foundation 15, a portion of tower structure 12, or any other suitable surface providing vertical support to the stabilizer legs 80 and thus central pole 46. Similar to lift arms 70, stabilizer legs 80 may include a hydraulic cylinder 84 and a piston rod 85 for facilitating the extension of stabilizer legs 80. According to alternative embodiments, stabilizer legs 80 are fixed length legs that are pivotally mounted to central pole 46. According to an exemplary embodiment of the present subject matter, lift arms 70 and stabilizer legs 80 may be configured for engaging tower structure in any

suitable matter to provide the support necessary for lifting or stabilizing central pole 46. For example, contact pads 72 and support pads 82 may have feature for engaging the wall, e.g., via friction, locking mechanisms, etc. According to still another embodiment, as best illustrated in FIGS. 2 and 4 through 9, additive printing device 40 may be configured to move print heads 42 to print one or more support structures or shelves 86 on inner wall 24 of tower structure 12. Lift arms 70 and stabilizer legs 80 can be configured for engaging these support shelves 86, e.g., by sitting on top of them, to raise central pole 46 or support central pole 46 to facilitate the printing process.
Although FIG. 2 illustrates all of tower structure 12 as being printed from a single material, e.g., concrete, it should be appreciated that each tower structure 12 may be printed using any suitable material, even if different from other sections. In addition, each tower structure 12 may have any suitable cross sectional profile (e.g., as taken along an axial direction A) and profile (e.g., as defined along the axial direction A). In this regard, as illustrated, tower structure 12 may be substantially cylindrical or have a circular cross section. However, according to still other embodiments, tower structure 12 may be polygonal, elliptical, oval, square, teardrop, airfoil, or any other suitable shape. In addition, according to still another embodiment, tower structure 12 may be tapered or vary in cross-sectional area depending on the vertical position along the tower structure 12. Referring now to FIG. 10, a block diagram of one embodiment of the controller 90 of the additive printing device 40 is illustrated. As shown, the controller 90 may include one or more processor(s) 92 and associated memory device(s) 94 configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like and storing relevant data as disclosed herein). Additionally, the controller 90 may also include a communications module 96 to facilitate communications between the controller 90 and the various components of the additive printing device 40. Further, the communications module 96 may include a sensor interface 98 (e.g., one or more analog-to-digital converters) to permit signals transmitted from one or more sensors or feedback devices to be converted into signals that can be understood

and processed by the processors 92. It should be appreciated that these sensors and feedback devices may be communicatively coupled to the communications module 96 using any suitable means, e.g., via a wired or wireless connection using any suitable wireless communications protocol known in the art. As used herein, the term "processor" refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. The processor 92 is also configured to compute advanced control algorithms and communicate to a variety of Ethernet or serial-based protocols (Modbus, OPC, CAN, etc.). Additionally, the memory device(s) 94 may generally comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s) 94 may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s) 92, configure the controller 90 to perform the various functions as described herein.
Now that the construction and configuration of tower structure 12 and additive printing device 40 have been presented according to an exemplary embodiment of the present subject matter, an exemplary method 100 for manufacturing a tower structure of a wind turbine using an additive printing device is provided. Method 100 can be used to form tower structure 12 using additive printing device 40, or to form any other suitable tower or tall concrete structure using any other suitable additive printing device. In this regard, for example, controller 90 may be configured for implementing method 100. However, it should be appreciated that the exemplary method 100 is discussed herein only to describe exemplary aspects of the present subject matter, and is not intended to be limiting. As shown in FIG. 11, method 100 includes, at step 110, printing one or more support shelves on an inner wall of a tower structure by depositing cementitious

material using a print head supported by a support arm rotatably and vertically mounted to a central pole. For example, step 110 may include printing tower structure 12 using additive printing device 40 as described above. In this regard, as best shown in FIG. 4, additive printing device 40 may begin the build process by being mounted on the ground or foundation 15, with stabilizer legs 80 in the unfolded position for supporting central pole 46 in a vertical orientation during a printing process. In addition, lift arms 70 may be in the retracted, folded position as print heads 42 (two illustrated in FIG. 4) rotate about central pole 46 while being supported by support arm 50 and moving along the radial direction R as needed. As layers of tower structure 12 are printed, support arm 50 may move upward along the vertical direction V to print subsequent layers. According to the exemplary embodiment, support shelves 86 are printed along with the tower structure 12, e.g., extending towards the central axis A of tower structure 12 along the radial direction R from inner wall 24. It should be appreciated that support shelves 86 may be continuous flanges extending circumferentially around tower structure 12 or may be spaced apart where needed to engage lift arms 70 and/or stabilizer legs 80. In addition, support structures or support shelves 86 may have any suitable size, profile, or configuration. For example, support shelves may be small ridges or protrusions, or large shelves (e.g., as illustrated in FIGS. 4 through 9).
After the support shelves 86 have been printed and print heads 42 have been raised to top 62 of central pole 46, the printing process cannot proceed without raising the print heads 42 to a higher vertical location. Thus, step 120 includes positioning a plurality of lift arms to extend from the central pole and engage the one or more support shelves. In this regard, as shown for example in FIG. 5, lift arms 70 may pivot to an unfolded position and be seated on support shelves 86. In addition, stabilizer legs 80 may be retracted (e.g., using hydraulic cylinder 84 and piston rod 85) and/or folded into central pole 46.
Then, as illustrated in FIG. 6, step 130 includes folding and/or retracting a plurality of stabilizer legs, e.g., to permit the raising of central pole without contacting the tower structure. Step 140 includes extending the plurality of lift

arms to raise the central pole. Specifically, the hydraulically actuated lift arms 70 may be extended to lift central pole 46 along the vertical direction V while maintaining its vertical orientation. As shown in FIG. 6, when the lift process begins, stabilizer legs 80 may leave the ground and may be moved to a folded position, particularly if needed to clear the support shelves 86. After the lift arms 70 have raised the central pole 46 such that the stabilizer legs 80 are positioned above support shelves 86, the stabilizer legs 80 may once again unfold and engage support shelves 86 to support central pole 46. Specifically, at step 150 the plurality of stabilizer legs may be positioned to extend from the central pole and engage the one or more support shelves to support the central pole. At this point, as shown in FIG. 7, lift arms 70 and stabilizer legs 80 may both be in contact with support shelves 86. Step 160 includes printing additional layers of the tower structure. As shown in FIGS. 8 and 9, this process may be repeated, layer-by-layer, shelf-by-shelf, until the tower structure 12 is complete and the additive printing device 40 is positioned at the very top of the tower structure 12. The lift arms 70 and stabilizer legs 80 may then operate in reverse the order described above to lower the additive printing device 40 back to the ground level or foundation 15, where it may be disassembled or otherwise removed from the completed tower structure 12.
FIG. 11 depicts an exemplary control method having steps performed in a particular order for purposes of illustration and discussion. Those of ordinary skill in the art, using the disclosures provided herein, will understand that the steps of any of the methods discussed herein can be adapted, rearranged, expanded, omitted, or modified in various ways without deviating from the scope of the present disclosure. Moreover, although aspects of the methods are explained using tower structure 12 and additive printing device 40 as an example, it should be appreciated that these methods may be applied to the operation of additive printing device to form any suitable tower structure.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any

incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.

WE CLAIM:
1. An additive printing device for manufacturing a tower structure of a wind
turbine, the additive printing device comprising:
a central pole extending substantially along a vertical direction;
a print head for selectively depositing cementitious material to form the tower
structure;
a support structure movably coupling the print head to the central pole;
a plurality of lift arms mounted to the central pole, the lift arms being extendable
to engage a portion of the tower structure and raise the central pole; and
a plurality of stabilizer legs mounted to the central pole, the plurality of stabilizer
legs being movable to a support position to support the central pole.
2. The additive printing device as claimed in claim 1, wherein the support
structure comprises:
a support arm extending substantially along a radial direction from the central pole.
3. The additive printing device as claimed in claim 2, wherein the support arm is mounted to the central pole by a rotary bearing.
4. The additive printing device as claimed in claim 3, wherein
a vertical rail mounted to the central pole, wherein the rotary bearing is slidably mounted to the vertical rail such that the support arm is movable along a vertical direction.
5. The additive printing device as claimed in claim 1, wherein the support
arm comprises:
a horizontal rail configured for slidably receiving the print head such that the print head may move along a radial direction.
6. The additive printing device as claimed in claim 1, wherein the support

structure comprises:
a flexible robotic arm rotatably mounted to the central pole and having the print
head mounted at a distal end of the robotic arm.
7. The additive printing device as claimed in claim 1, wherein each of the plurality of lift arms comprises a hydraulic cylinder and a piston rod.
8. The additive printing device as claimed in claim 1, wherein the additive printing device further comprises:
a plurality of support arms extending from the central pole; and
a plurality of print heads, each of the plurality of support arms supporting at least
one of the plurality of print heads.
9. The additive printing device as claimed in claim 1, wherein the print head prints one or more support structures on an inner wall of the tower structure, the plurality of lift arms and the plurality of stabilizer legs being configured for engaging the one or more support structures.
10. The additive printing device as claimed in claim 1, wherein the plurality of lift arms comprise three or more lift arms and the plurality of stabilizer legs comprise three or more three stabilizer legs.
11. The additive printing device as claimed in claim 1, wherein the plurality of stabilizer legs are positioned in an unfolded position to support the central pole while the print head prints one or more layers of the tower structure and move to a folded position as the plurality of lift arms raise the central pole.
12. The additive printing device as claimed in claim 1, wherein the plurality of lift arms are configured for moving to a retracted position to lower the central pole within the tower structure.

13. A method of manufacturing a tower structure of a wind turbine using an
additive printing device, the additive printing device comprising a central pole, a
plurality of lift arms mounted to the central pole, a plurality of stabilizer legs
mounted to the central pole, and a print head movably coupled to the central pole
by a support arm, the method comprising:
printing one or more support structures on an inner wall of the tower structure by
depositing cementitious material using the print head and moving the support arm
along the central pole;
raising the central pole; and
printing additional layers of the tower structure.
14. The method as claimed in claim 13, wherein raising the central pole
comprises:
positioning the plurality of lift arms to engage the one or more support structures;
retracting the plurality of stabilizer legs;
extending the plurality of lift arms to raise the central pole; and
positioning the plurality of stabilizer legs to engage the one or more support
structures to support the central pole;.
15. The method as claimed in claim 13, wherein the support arm is mounted to the central pole by a rotary bearing, the rotary bearing being coupled to the central pole by a vertical rail, and wherein printing the one or more support structures comprises rotating the support arm about the central pole and moving the support arm along the vertical direction.
16. The method as claimed in claim 13, wherein the print head is slidably received within a horizontal rail mounted to the support arm, and wherein printing the one or more support structures comprises moving the print head along a radial direction.
17. The method as claimed in claim 13, wherein the plurality of lift arms are

pivotally mounted to central pole, wherein positioning the plurality of lift arms to engage the one or more support structures comprises pivoting the plurality of lift arms to an unfolded position.
18. The method as claimed in claim 13, wherein positioning the plurality of
stabilizer legs comprises pivoting the plurality of stabilizer legs to an unfolded
position to support the central pole, the method further comprising:
moving the plurality of stabilizer legs to a folded position as the plurality of lift arms raise the central pole.
19. The method as claimed in claim 13, further comprising: retracting the plurality of lift arms to lower the central pole within the tower structure.
20. An additive printing device for manufacturing a structure, the additive printing device comprising:
a central pole extending substantially along a vertical direction;
a print head for selectively depositing cementitious material to form the structure;
a support structure movably coupling the print head to the central pole;
a plurality of lift arms mounted to the central pole, the lift arms being extendable
to engage a portion of the structure and raise the central pole; and
a plurality of stabilizer legs pivotally mounted proximate a bottom of the central
pole, the plurality of stabilizer legs being movable to an unfolded position to
support the central pole.