In-mold fiducial markers in wind turbine blade manufacturing for improved optical system calibration

Abstract

1. A method for manufacturing a composite structure, comprising: providing a mold configured to form a composite structure; providing at least one magnetic anchor disposed within the mold; providing at least one optical marker magnetically coupled to the at least one magnetic anchor; providing an optical projector that projects at least one light beam toward the at least one optical marker; receiving at least one reflected beam from the at least one optical projector to identify positions of the optical markers disposed on the mold; and calibrating the optical projector by comparing positions of predetermined virtual optical markers with positions of the identified optical markers.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 369,128, filed July 22, 2022, the entire contents of which are incorporated herein by reference.

[0002] The disclosed subject matter relates to systems and corresponding methods for manufacturing large composite structures, such as wind turbine blades. These large composite structures are typically formed in two-part molds that require complex component placement / installation after the blade halves have been molded, followed by a mold closure process to complete the manufacturing process.

[0003] In particular, the present disclosure provides a mold with optical fiducial markers for calibrating optical systems (e.g., overhead laser projection into the mold) in the manufacture of wind turbine blades. In particular, the present disclosure provides a method for calibrating digital fiducials with physical fiducials by incorporating reflective optical markers into the mold (and optionally outside the mold) without creating recesses or voids in the mold's interior surfaces. This allows for accurate and precise assembly of blade components, such as shear webs, spar caps, and composite layup segments. The calibration techniques disclosed herein are applicable to a variety of overhead projection devices and projection geometries, including the apparatus and techniques disclosed in U.S. Pat. Nos. 10,889,075 and 11,007,727, the entire contents of each of which are incorporated herein by reference.

[0004] Wind turbine blades typically include a hollow blade shell constructed primarily from a composite material such as fiberglass reinforced plastic. The blade shell typically consists of two half shells, a lower pressure shell and an upper suction shell, which are molded separately in respective female molds and then joined along flanges at the leading and trailing edges of the blade. Exemplary views of mold halves for a wind turbine blade are shown schematically in Figures 1A-1C.

[0005] Referring to Figure 1a, this shows a mould 10 for a wind turbine blade, separated into two half moulds, an upper suction side mould 10a and a lower pressure side mould 10b, side-by-side in an open mould arrangement. A pressure side blade shell 12a is supported on a mould surface 14a of the lower mould 10a, and a suction side blade shell 12b is supported on a mould surface 14b of the upper mould 10b. Shells 12a and 12b each consist of multiple layers of glass fibre cloth bonded together with a cured resin.

[0006] After shells 12a, 12b are formed in their respective mold halves 10a, 10b, shear webs 16 are bonded to spar caps located on or within the interior surface 17 of upwind blade shell 12a. Shear webs 16 are longitudinally extending structures that bridge the two blade half-shells 12a, 12b and serve to transfer shear loads from the blade to the hub of the wind turbine during use. In the particular embodiment shown in cross section in FIG. 1a, each shear web 16 comprises a web 18 having an optional first longitudinally extending mounting flange 20 at its lower end 19 and an optional second longitudinally extending mounting flange 22 at its upper end 21. An adhesive, such as epoxy, is applied along these mounting flanges 22 and used to bond shear webs 16 to the spar caps of each half-shell 12a, 12b.

[0007] As shown in Figure lb, after the shear web 16 is bonded to the upper blade shell 12a, adhesive is applied along the shear web's second (upper) mounting flange 22 and along the leading and trailing edges 24, 26 of the blade shells 12a, 12b. The upper mold 10b (including the upper blade shell 12b) is then lifted and rotated into position over the lower blade mold 10a, bonding the two blade half shells 12a, 12b along the leading and trailing edges 24, 26 and bonding the shear web 16 to the spar cap along the inner surface 28 of the upper blade shell 12b. The process of placing one mold half over the other is called closing the mold.

[0008] Referring to FIG. 1C, a problem can arise during mold closure in that the shear webs 16 may move slightly relative to the top shell 12b. For example, the shear webs 16 may move slightly under their own weight during mold closure or may become misaligned due to contact with the top shell 12b. Additionally or alternatively, the shear webs and spar caps may be improperly positioned prior to mold halves being closed, resulting in a damaged or defective blade structure. Furthermore, the concave curvature of the top shell 12b tends to press the shear webs 16 together slightly, as shown in FIG. 1C. Such movement of the shear webs 16 during mold closure may result in the shear webs 16 being bonded to the spar cap and / or top shell 12b in a suboptimal position.

[0009] As wind turbine blades become larger and larger to improve operational efficiency, safety margins decrease, necessitating tighter manufacturing acceptance standards and tolerances, which in turn necessitates the design and implementation of manufacturing tools that enable highly accurate process checks to meet stringent specifications and requirements.

[0010] This disclosure provides new tools and techniques for spar cap calibration using an overhead optical projection system to calibrate the digital / virtual coordinates of a component (e.g., layup segment, spar cap, etc.) to its actual physical coordinates identified via reflective optical markers that are removably attached to the mold. Furthermore, the removable markers are attached (e.g., magnetically) via anchors located within the mold, which are located below the mold's exterior surface. Thus, the mold surface is integral and continuous, eliminating the need to form openings or recesses to receive the markers (and thereby preventing unwanted resin infiltration into the openings).

[0011] The calibration described here verifies the spatial placement of assembly components (e.g., layup segments, spar caps, cores, etc.) and confirms the desired assembly configuration. This provides an efficient system for highly accurate placement of internal components during wind turbine blade assembly without affecting the mold or blade structure. Summary of the Invention

[0012] The objects and advantages of the disclosed subject matter will be set forth in the following description and may be learned by practice of the disclosed subject matter. Additionally, additional advantages of the disclosed subject matter will be realized and attained by the methods and systems particularly pointed out in the description and claims herein, as well as become apparent from the accompanying drawings.

[0013] To achieve these and other advantages and in accordance with the objectives of the disclosed subject matter, as embodied and broadly described, the disclosed subject matter includes a method for manufacturing a composite structure, the method including the steps of providing a mold configured to form a composite structure, providing at least one magnetic anchor disposed within the mold, providing at least one optical marker magnetically coupled to the at least one magnetic anchor, providing an optical projector that projects at least one light beam toward the at least one optical marker, receiving a reflected beam from the at least one optical projector to identify locations of the optical markers disposed on the mold, and calibrating the optical projector by comparing the locations of the identified optical markers with predetermined virtual optical marker locations.

[0014] In some embodiments, the method also includes detaching the at least one optical marker from the magnetic anchor.

[0015] In some embodiments, the method also includes placing the plurality of layup segments in the mold after the at least one optical marker is removed.

[0016] In some embodiments, the method also includes injecting resin through the plurality of layup segments after the at least one optical marker is removed.

[0017] In some embodiments, at least one layup segment is disposed over the magnetic anchor.

[0018] In some embodiments, the composite structure is a wind turbine blade.

[0019] In some embodiments, the at least one magnetic anchor is located on a flange of a leading edge of a wind turbine blade.

[0020] In some embodiments, at least one magnetic anchor is located at the midpoint of the blade chord.

[0021] In some embodiments, at least one magnetic anchor is positioned on the blade at a location that coincides with the spar cap.

[0022] In some embodiments, multiple magnetic anchors are provided, and the magnetic anchors are positioned within the mold at locations that coincide with the maximum blade chord length.

[0023] In some embodiments, a plurality of optical markers are positioned between the leading and trailing edges of the blade.

[0024] In some embodiments, at least one magnetic anchor is positioned below the surface of the mold.

[0025] In some embodiments, at least one optical marker is configured as a mirror.

[0026] In some embodiments, the position(s) of the predetermined digital optical marker(s) and the positions of the identified physical optical marker(s) do not match, and the position(s) of the predetermined digital optical marker(s) are adjusted.

[0027] In some embodiments, the projection is performed by multiple lasers.

[0028] In some embodiments, the laser is configured to move relative to the mold.

[0029] In some embodiments, the lasers are configured to move relative to one another.

[0030] In some embodiments, multiple optical beams are projected simultaneously onto multiple optical markers.

[0031] In some embodiments, the selected beams are projected in a serial fashion.

[0032] In some embodiments, the optical markers are removed from the surface of the wind turbine blade before closing the first mold half onto the second mold half.

[0033] It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the disclosed subject matter claimed.

[0034] The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to illustrate and provide a further understanding of the methods and systems of the disclosed subject matter, and together with the description, the drawings serve to explain the principles of the disclosed subject matter.

[0035] A detailed description of various aspects, features, and embodiments of the subject matter described herein is provided with reference to the accompanying drawings, which are briefly described below. The drawings are illustrative and are not necessarily drawn to scale, and some components and features may be exaggerated for clarity. The drawings illustrate various aspects and features of the present subject matter and may depict one or more embodiments or examples of the invention, in whole or in part. [Brief explanation of the drawings]

[0036] [Figure 1A] 1 shows a cross-sectional view of a conventional wind turbine blade mold and manufacturing method. [Figure 1B] 1 shows a cross-sectional view of a conventional wind turbine blade mold and manufacturing method. [Figure 1C] 1 shows a cross-sectional view of a conventional wind turbine blade mold and manufacturing method. [Figure 2A] 1 is an illustrative view of optical fiducial markers positioned along a mold flange in accordance with an embodiment of the disclosed subject matter. [Figure 2B] 1 is an illustrative view of optical fiducial markers positioned along a mold flange in accordance with an embodiment of the disclosed subject matter. [Figure 2C] 1 is an illustrative view of optical fiducial markers positioned along a mold flange in accordance with an embodiment of the disclosed subject matter. [Figure 3A] 1 is an illustrative diagram of optical fiducial markers positioned at multiple locations within a mold in accordance with an embodiment of the disclosed subject matter. [Figure 3B] 1 is an illustrative diagram of optical fiducial markers positioned at multiple locations within a mold in accordance with an embodiment of the disclosed subject matter. [Figure 3C] 1 is an illustrative diagram of optical fiducial markers positioned at multiple locations within a mold in accordance with an embodiment of the disclosed subject matter. [Figure 4A] 10A-10C are illustrative diagrams of optical fiducial markers positioned along a mold flange and within the mold in accordance with an embodiment of the disclosed subject matter. [Figure 4B] 10A-10C are illustrative diagrams of optical fiducial markers positioned along a mold flange and within the mold in accordance with an embodiment of the disclosed subject matter. [Figure 4C] 10A-10C are illustrative diagrams of optical fiducial markers positioned along a mold flange and within the mold in accordance with an embodiment of the disclosed subject matter. [Figure 4D] 10A-10C are illustrative diagrams of optical fiducial markers positioned along a mold flange and within the mold in accordance with an embodiment of the disclosed subject matter. [Figure 4E]10A-10C are illustrative diagrams of optical fiducial markers positioned along a mold flange and within the mold in accordance with an embodiment of the disclosed subject matter. DETAILED DESCRIPTION OF THE INVENTION

[0037] Reference will now be made in detail to exemplary embodiments of the disclosed subject matter, which are illustrated by way of example in the accompanying drawings, in which the method and corresponding steps of the disclosed subject matter will now be described in conjunction with a detailed description of the system.

[0038] The methods and systems presented herein can be used in the construction of composite structures, such as automotive components, marine components, construction components, and the like. The disclosed subject matter is particularly suited for the construction of wind turbine blades. For purposes of explanation and illustration, but not limitation, an exemplary embodiment of a system according to the disclosed subject matter is shown in FIGS. 2-4C and generally designated by the reference numeral 1000. Similar reference numerals (distinguished by leading numerals) may be used in the various views and figures shown herein to indicate functionally corresponding, but not necessarily identical, structures.

[0039] A wind turbine blade can be formed from two shells or "skins," each composed of multiple layers of composite segments (or "layups") that are placed in a mold and then infused with resin using vacuum infusion resin transfer technology (VARTM) in various embodiments. Additionally or alternatively, the blade shell / skin can be formed from pre-formed or "prepreg" layup segments.

[0040] A blade may include one or more structural components configured to increase stiffness, buckling resistance, and / or strength to the blade. For example, a blade may include one or more longitudinally extending spar caps configured to engage opposing inner surfaces of the pressure and suction sides of the blade. Additionally, one or more shear webs may be disposed between the spar caps to form a beam-like structure. The spar caps may generally be designed to control bending stresses and / or other loads acting on the blade generally in the spanwise direction (a direction parallel to the span of the blade) during operation of the wind turbine. Similarly, the spar caps may also be designed to withstand spanwise compression experienced during operation of the wind turbine.

[0041] The spar cap of the present disclosure is comprised of a plurality of pultruded members that can be assembled to form a first portion of the spar cap. In certain embodiments, the pultruded member can be formed by impregnating a plurality of fibers (e.g., glass or carbon fibers) with a resin and curing the impregnated fibers. The fibers can be impregnated with the resin using any suitable means. Furthermore, the resin can include, but is not limited to, polyester, polyurethane, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), vinyl ester, epoxy, or similar suitable resin materials. Furthermore, as shown, the pultruded members can separate into one or more pultruded member bundles to form a second portion of the spar cap as the spar cap approaches the blade root.

[0042] More specifically, the spar cap is comprised of a plurality of pultruded members that are assembled to form one or more layers. The layers may then be stacked together and bonded together using any suitable means, such as vacuum infusing the members together, or joining the members with adhesives, semi-pregs, pre-pregs, or the like.

[0043] This disclosure introduces new tools and techniques in which an overhead optical (e.g., laser) projection system provides calibration and alignment of optical projectors to mold surfaces, thereby verifying accurate assembly of components (e.g., layup segments, spar caps, shear webs, cores, etc.). In various embodiments, the optical projection system can be a laser-based optical system configured to emit a laser beam. In various embodiments, the optical projection system can be a movable (vertically and / or laterally) light-emitting system that emits light at any wavelength in the electromagnetic spectrum, including visible light. In various embodiments, the optical projection system can be positioned at any location relative to the mold components. Those skilled in the art will appreciate that "overhead" is merely one example of the disclosed system and is not intended to limit the location of the projection system or its orientation.

[0044] Laser projection systems configured to assist in the forming process in the manufacture of wind turbine blades may require the projector (or the lines displayed therefrom, e.g., layup edges to guide the installation of layup segments, spar cap locations, etc.) to be calibrated and aligned to the actual / physical mold surface. Upon successful completion of this process, the digital 3D pattern of the blade component is accurately projected into the mold, providing the precision required to support the composite layup process.

[0045] To calibrate an overhead laser projection system, actual geometric reference points are required to host the optical markers. These geometric reference points may be formed as target points. In various embodiments, these reflective target points are formed as flat mirrors mounted in a plastic case, allowing the projector to map the coordinates of the 3D model (projected pattern) to actual locations within the mold workspace. In various embodiments, a minimum of six target points may be used. In various embodiments, more markers may be used, potentially improving the accuracy of the system. According to embodiments, multiple optical markers (target points) may be arranged on the mold in a custom pattern depending on the mold shape and application and the part to be manufactured therefrom. According to embodiments, multiple optical markers (target points) may be arranged on the mold in a pattern corresponding to one or more internal components or locations of the blade to be manufactured. For example, without limitation, multiple optical markers (target points) may be arranged around a particular blade contour, the intended location of a spar cap, or other internal reinforcing component (e.g., forward / aft along the blade span, laterally along the blade chord). According to embodiments, the optical markers may be placed on the mold in a grid pattern, linearly, clustered, or in a custom configuration corresponding to the mold contour. The optical markers may, in embodiments, be placed on the mold according to instructions generated by one or more computers, processors, computer-aided design applications, etc. In various embodiments, the markers (target points) may be placed on the mold corresponding to one or more analyses, such as finite element analysis (FEA). The optical markers may be placed on the mold by a human user or multiple human users.

[0046] In some embodiments of the present disclosure, the laser projection system may include a coordinate mapping algorithm within its processor and create a coordinate system by running an iterative best-fit algorithm based on the spatial data received from the markers. This iterative process may aim to find a coordinate system that minimizes the root-mean-square deviation between the target point's actual (physical) location and its estimated (digital) location. Thus, the accuracy of the estimated location is highest near the physical marker and decreases with increasing distance from the physical reference point. Each projector forms its own local coordinate system and projects the contour accordingly.

[0047] Retroreflective Optical Markers The methods and systems described herein facilitate high-precision placement of components such as spar caps during the forming process. In particular, the present disclosure introduces apparatus and methods that provide precise geometric references across the entire blade span and blade chord. The present disclosure can include overhead optical projection and laser tracking systems that assist with positioning and measurement tools for placing components and reinforcing layers (or "layup" kitting segments) during the layup process.

[0048] FIG. 2A shows a schematic diagram of a longitudinal cross section (i.e., a spanwise view from root to tip) of a blade half, with multiple markers 200 distributed along the blade span. The markers 200 are disposed on the interior or exterior surface of the mold 100 and can be configured as retroreflective optical markers that reflect radiation (e.g., light) back to its source 150 with minimal scattering. In some embodiments, the illumination source is one or more overhead optical (e.g., laser) projectors. In various embodiments, each projector 150 can project multiple beams 110, each beam dedicated to a single marker 200. In various embodiments, the trajectories of the beams 110 can be adjusted to illuminate multiple markers 200. In various embodiments, each projector 150 can project multiple beams 110 toward multiple optical markers. In various embodiments, each projector 150 can project multiple beams 110 toward a subset of the optical markers. In various embodiments, each projector 150 can project multiple beams 110 toward a single optical marker. For purposes of this disclosure, each projector 150 can target one or more optical markers in its field of view within the mold. During the manufacturing process, the relative coordinates of the overhead projector(s) can be fixed with respect to the blade mold. Similarly, in various embodiments, the overhead projector(s) remain fixed during operation. Conversely, in some embodiments, the overhead projector(s) can be adjusted (e.g., laterally, longitudinally, and vertically, such as lowered toward the mold).

[0049] In the embodiment shown in FIG. 2A , the markers 200 are housed within bushing holes and positioned on the mold flange. In some embodiments, the markers 200 are movable (or removable / replaceable) relative to the stem to which they are attached. In some / all embodiments, the orientation of the markers 200 (e.g., pitch / angle relative to the mold surface) is adjustable (so that the marker reflects the beam at a predetermined angle of incidence). Because the location of these reference points is outside the edge of the part being formed (i.e., outside the wind turbine blade and outside the closed mold when the top half is placed on the bottom mold half shown), there is no interference between the markers 200 and the blade manufacturing process (e.g., layup or injection). In other words, because the markers are positioned only outside the mold, they do not obstruct or interfere with the manufacturing processes occurring within the mold.

[0050] However, as the distance from the flange increases, the accuracy of the projection line 110 decreases. This error is shown by the dashed line in FIG. 2B, with the largest magnitude of error at the center of the blade chord (farthest from marker location 200 in FIG. 2A). This furthest distance on the mold—i.e., the center of the mold relative to the end—is where the spar cap(s) are located. The spar cap is one of the most critical (load-bearing) components of the blade. This lack of accuracy can lead to out-of-tolerance positioning of the girder or shear web 300, as shown in FIG. 2C. In FIG. 2C, the projection 110 is not oriented vertically, representing the midpoint 300 where the girder should be located, but instead is angled off, resulting in the girder being positioned off-center, thus jeopardizing the blade's integrity and performance.

[0051] To address this issue, another embodiment of the present disclosure provides an in-mold marker placement, as shown in Figures 3A-3C. This marker placement is particularly advantageous in blade sections near the blade's maximum chord, where the distance from the flange to the center of the airfoil is critical. Providing an additional marker(s) in the center of the mold, as shown in Figure 3A, provides an additional reference point in the center of the tool for locating critical load-bearing components. This results in improved positional accuracy, as shown by the dashed projection line in Figure 3B (which is largely obscured by the mold surface line, indicating a virtual zero error). In various embodiments, multiple markers may be placed near the center of the mold or at selected high-priority locations on the mold. In various embodiments, multiple markers may track or surround the location of an internal component to be placed. Compare Figure 2B (without a central mold marker 200) with Figure 3B (with a central mold marker) and note the difference between the predicted position and the actual position error. In the absence of a central marker (as shown in Figure 3A), the projected position (dashed line) will be incorrectly tilted in a sinusoidal pattern above (e.g., at the center point) and below the mold surface, as shown in Figure 2B. Similarly, the shear web in Figure 3C (with a centrally placed marker) is correctly positioned at the center of the blade, while the shear web in Figure 2C is displaced / tilted toward the leading edge of the blade.

[0052] According to one aspect of the present disclosure, the internal marker(s) 201 can be removably or releasably attached to the mold 100. For example, the mold 100 can include a first set of reflective optical targets 202 disposed on the mold flange and a second set of reflective optical markers 212 disposed within the mold (see FIG. 4A ). An enlarged cross-sectional view of the first set of reflective optical targets 202 is shown in FIG. 4B , where the targets 202 can fit directly within the recesses 102 of the mold 100. In various embodiments, an exemplary reflective marker can be mushroom-shaped with a spherical top portion 202 a for reflecting the beam from the projector 150 and an elongated stem 202 b for insertion into the mold recesses 102. The stem and the spherical portion can be integrally molded or formed as separate, removable components. The stem 202 b can be formed with an adjustable (e.g., telescoping) height so that the reflective spherical portion can be raised or lowered to a desired height.

[0053] The marker(s) 212 may be disposed within the mold, and each marker 212 may include an anchor member 210 integrally molded within the mold; in some cases, the anchor member 210 may be embedded between the inner and outer surfaces of the mold, as shown in FIG. 4D . In some embodiments, the anchor member 210 may be flush with the inner surface of the mold (thereby providing shape to the composite structure formed therein). In various embodiments, the anchor member 210 may include any contours of the mold, such that the flush portion of the anchor member 210 does not protrude above the mold surface. In various embodiments, the anchor member 210 may be disposed deeper than the surface of the mold, for example, the anchor member 210 may be disposed within a cavity within the mold.

[0054] In various embodiments, the anchor member 210 can include a magnet that releasably connects or couples with the magnetic marker 212 to securely hold the magnetic marker 212 and enable calibration of the optical projector 150. In some embodiments, the magnet of the anchor member 210 is a rare earth magnet. Additionally or alternatively, an electromagnet can be used, if desired. In various embodiments, the magnetic attraction of the anchor member 210 can be selectively or adjustably manipulated, such that the anchor member 210 can be turned off to release the magnetic marker 212. In various embodiments, the anchor member 210 can incorporate a selectively strong magnet, for example, a magnet configured to increase its attractive force with increasing applied current.

[0055] The coupling of magnetic markers 212 and magnetic anchors 210 allows for a strong bond between the components without creating recesses or voids in the interior surface of mold 100. In various embodiments, this bond may be temporary and releasable. As shown in the cross-sectional view of Figure 4E, the interior surface of the mold is continuous and has a constant radius of curvature directly above anchors 210 and across its entire width.

[0056] One of the major concerns with implementing in-mold markers is the potential complications that arise after the reflector 212 is removed. In the installation of side flange markers 202, the bushing holes 102 housing the marker mirrors 202 are located outside the blade edge and therefore do not interfere with the manufacturing process, such as resin infiltration during vacuum-assisted resin impregnation (Figure 4C). However, a similar arrangement (male / female mechanical interlock) for in-mold markers 212 could pose a problem as the infused resin would penetrate openings and recesses within the mold. To address this issue, a built-in magnetic attachment configuration, such as anchor 210, is provided, as shown in Figure 4E. In this setup, the tool surface remains intact after the marker is removed (after calibration). In various embodiments, a mechanical interlock with an integrated sealing feature, such as an O-ring or gasket, can be used to prevent liquid resin infiltration.

[0057] The markers 200, 212 may be configured as separate devices or components attached to the blade mold 100. Additionally or alternatively, the internal markers may include a first portion 210 integrally molded with the mold and removable (and reflective) surface features 212. The number and location of markers may vary depending on blade design specifications, such as the number, location, and size of spar caps and shear webs. The distribution of markers need not be uniform but may instead be concentrated in specific regions of the blade. Additionally, the number, distribution, and shape of markers may vary along the blade span. For example, a higher concentration of markers may be present in locations with large / heavy internal components and / or locations with more complex shapes or surface contours. For example, more markers may be located closer to the blade root compared to the blade tip.

[0058] While FIGS. 4A-4D show exemplary embodiments of markers 202, 212 having a spherical, e.g., hemispherical, shape, alternative shapes (e.g., curved, nonlinear) are within the scope of the present disclosure. In some embodiments, the markers are comprised of a curved surface(s). In various embodiments, the markers may have a compound curved shape, such as a rivet head shape. Additionally, or alternatively, in some embodiments, the markers are formed with linear surfaces (e.g., facets). In various embodiments, faceted markers may have facets that point toward one or more optical projectors or another portion of the mold. By way of example and without limitation, a marker can have any number of facets, such as a bolt head. As shown, retroreflective optical markers 202, 212 positioned in / on mold 100 allow an overhead projection system to verify and calibrate the component's digital spatial location with its actual physical location within the mold. In embodiments where full three-dimensional (3D) tracking is desired, multiple markers can be included at different points on the mold. Although a single mold half is shown for simplicity, the present disclosure can be used for both the top and bottom mold halves, if desired. In various embodiments, both the top and bottom molds can include multiple markers, and one or more projection systems can be positioned above or near the molds. In various embodiments, the top and bottom molds are formed opposite each other, and a projection system is positioned between them that can simultaneously project beams in opposite directions.

[0059] The coordinates of the selected markers are predetermined to accurately support the tracking process. Therefore, the locations of the fiducial markers are initially specified in a 3D manufacturing model of the blade mold and are specific to the component's shape and the data desired to be collected. To manufacture a mold (used in manufacturing wind turbine blades), a male "plug" is first formed, serving as a structure that imparts the specified shape to the mold. During the construction of the plug, marker points are formed. In various embodiments, the marker points may be formed in the mold by computer numerical control (CNC) machining or other automated methods. In various embodiments, the marker points may be formed in the plug by one or more manual procedures, such as with a drill press or hand tools. Optical markers, i.e., marker points, may be manufactured in the mold during the resin impregnation process. The locations of the marker anchors 210 are then transferred or applied to the final mold, where they can serve as seats to host or accept retroreflective markers 212.

[0060] The reflective magnetic marker 212 can be manually removed or separated from the magnetic anchor 210 by applying sufficient physical force to overcome the magnetic force. In some embodiments, multiple reflective magnetic markers 212 can be coupled to a single or common anchor 210. According to embodiments, the magnetic marker 212 may include a magnetic anchor 210 configured for use with an electromagnet. The electromagnet may be configured to generate a magnetic field when an electric current is passed through it. When the electric current is turned off, the electromagnet may be configured to lose its magnetic field, thereby releasing the magnetic anchor 210 and, therefore, the magnetic marker 212.

[0061] After the markers 212 are removed (at least from the interior portion of the mold cavity), the anchor member 210 remains fixed within the mold 100, the blade layup segments can be placed, and the resin impregnation process can be carried out (while the anchor member 210 remains within the mold 100 below the layup segments and resin). As noted above, the sealed anchor 210 does not have any gaps or openings to prevent unwanted resin infiltration. The mold closing operation then begins (i.e., the lower mold containing the blade half and the upper mold containing the blade half rotate together to form the complete blade).

[0062] The tracking system disclosed herein allows for the identification (and correction) of discrepancies between the digital mold / blade design and the actual physical mold / blade's reference point location(s), preventing misalignment of various components during blade assembly. The tracking system disclosed herein also allows for the calibration / verification (and subsequent correction) of blade model shape misalignments relative to multiple axes, reference planes, and reference points. In some embodiments, an overhead laser can: i) detect discrepancies between the digital reference locations and the physical marker locations; and ii) provide correction instructions, e.g., superimpose visual (and audio) aids instructing the operator how far and in what direction to move the digital marker locations to the correct location. In various embodiments, visual aids, such as one or more arrows or dotted lines, may be projected. As discussed above, the projection device need not necessarily use a laser or be located overhead as described in the exemplary embodiment.

[0063] The projection coordinates can be transmitted electronically, visually, or optically to all optical projectors, or in some embodiments, only to selected projectors (e.g., the projection location of a route marker is transmitted only to the optical projector above the route section of the mold / blade). Projection files can also include a key (e.g., a prefix or suffix, similar to Internet Protocol packet addressing) that indicates that two particular projection files are to be maintained sequentially when directed to adjacent panels in the mold. In various embodiments, one or more users and / or computers can identify which coordinates to send to which optical projectors. For example, route data can be transmitted to the route optical projector. In another example, route data can be transmitted to one or more midspan projectors depending on one or more applications.

[0064] During the core placement process on the factory floor, the projected laser line is used to identify structures or surfaces that deviate from the model. In some embodiments, the identification of deviations can be performed automatically (e.g., by one or more cameras, such as optical cameras operating in any band of the electromagnetic spectrum), within a predefined acceptable tolerance range. Additionally or alternatively, the identification of deviations can be performed by manual inspection by an operator (or confirmed if first performed automatically). If deviations beyond acceptable limits are identified, digital or physical markers can be repositioned as needed or discarded. In various embodiments, the deviations can be visually assessed by one or more optical markers, such as lasers or reflections. Additionally, if the deviations exceed acceptable tolerances, an alert can be issued to highlight or flag the deviation. In some embodiments, confirmation that the deviations have been addressed must be entered before the next projection pattern can be projected.

[0065] The amount of allowable error / deviation may depend on the materials used and the operating environment of the particular blade. In some embodiments, the allowable error or tolerance may vary along and across the location of the blade. For example, the range of allowable tolerance or deviation may be smaller at material and / or thickness transition locations, and along the leading and trailing edges.

[0066] In the exemplary embodiment shown, a series of lasers are positioned above the wind turbine mold and project patterns toward the mold during the manufacturing process. The number of laser projectors depends on the length of the blade and the height of the projectors relative to the mold surface. While the projectors in this exemplary embodiment may be fixed in position, each projector may include a galvo-driven mirror integrated therein, allowing one or more laser beams to be reflected and moved to create the 3D contours. While the lasers shown are mounted independently in fixed positions, alternative configurations are contemplated in which all or some of the laser projectors are movable relative to one another. For example, the laser projectors can be adjusted in vertical position relative to the blade mold, e.g., lowered from the ceiling to be closer to the mold, thereby providing a more highly resolved, focused line. In various embodiments, one or more of the projectors may be positioned on a gimbal, a robotic arm, an articulated non-robotic arm, etc. In various embodiments, one or more projectors may be automatically or manually positioned relative to the mold. The projectors can be programmed with predefined patterns to project onto the blade mold (and / or layup material that may be placed thereon). Each blade design may require a different projection pattern and therefore a unique program to be input into the projection system.

[0067] While the subject matter disclosed herein has been described with reference to certain preferred embodiments, those skilled in the art will recognize that various modifications and improvements can be made thereto without departing from the scope of the disclosed subject matter. Furthermore, even if individual features of one embodiment of the disclosed subject matter are discussed herein or shown in the drawings of one embodiment but not other embodiments, it will be apparent that individual features of one embodiment can be combined with one or more features of other embodiments or with features of multiple embodiments.

Claims

1. A method for manufacturing a composite structure, comprising: providing a mold configured to form a composite structure; providing at least one magnetic anchor disposed within the mold; providing at least one optical marker magnetically coupled to the at least one magnetic anchor; providing an optical projector that projects at least one light beam toward at least one optical marker; receiving at least one reflected beam from the at least one optical projector to identify the location of the optical marker located on the mold; calibrating the optical projector by comparing predetermined virtual optical marker positions with the identified optical marker positions; A method comprising:

2. The method of claim 1 , further comprising the step of detaching the at least one optical marker from the magnetic anchor.

3. The method of any one of claims 1 to 2, further comprising depositing a plurality of layup segments in the mold after the at least one optical marker is removed.

4. The method of any one of claims 1 to 3, further comprising the step of injecting resin through the plurality of lay-up segments after the at least one optical marker is removed.

5. The method according to any one of claims 1 to 4, wherein the at least one lay-up segment is placed on top of the magnetic anchor.

6. The method of any one of claims 1 to 5, wherein the composite structure is a wind turbine blade.

7. The method according to any one of claims 1 to 6, wherein the at least one magnetic anchor is arranged on a flange of a leading edge of the wind turbine blade.

8. The method of any one of claims 1 to 7, wherein the at least one magnetic anchor is positioned at the midpoint of the blade chord.

9. The method of any one of claims 1 to 8, wherein the at least one magnetic anchor is positioned at a blade location coincident with a spar cap.

10. The method of any one of claims 1 to 9, wherein a plurality of magnetic anchors are provided, said plurality of magnetic anchors being positioned within the mould at positions corresponding to maximum blade chord lengths.

11. The method of any one of claims 1 to 10, wherein a plurality of optical markers are positioned between the leading and trailing edges of the blade.

12. The method of any one of claims 1 to 11, wherein the at least one magnetic anchor is positioned below the surface of the mold.

13. The method according to any one of claims 1 to 12, wherein the at least one optical marker is configured as a mirror.

14. 14. The method of any one of claims 1 to 13, wherein a comparison of the predetermined digital optical marker position(s) with the identified physical optical marker positions results in a discrepancy, and the predetermined digital optical marker positions are adjusted.

15. The method according to any one of claims 1 to 14, wherein the projection is performed by a plurality of lasers.

16. The method of any one of claims 1 to 15, wherein the laser is configured to move relative to the mold.

17. A method according to any preceding claim, wherein the lasers are arranged to move relative to each other.

18. The method of any one of claims 1 to 17, wherein multiple optical beams are projected simultaneously towards multiple optical markers.

19. A method according to any one of the preceding claims, wherein the selected beams are projected sequentially.

20. The method according to any one of the preceding claims, wherein the optical markers are removed from the surface of the wind turbine blade before closing the first mould half onto the second mould half.

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