Coordinated end effector installation of fasteners to aircraft structures

Abstract

To provide systems and methods for applying fasteners to a structure.SOLUTION: A method includes disposing a first set of end effectors along a fixed inner track that follows an Inner Mold Line (IML) of a structure, disposing a second set of end effectors along a fixed outer track that follows an Outer Mold Line (OML) of the structure, aligning a first end effector at the fixed inner track with a second end effector at the fixed outer track, clamping the structure between the first end effector and the second end effector by pressing the first end effector and the second end effector into the structure, and applying a fastener to the structure.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to the field of assembly, and more particularly to the assembly of structures such as aircraft. [Background technology]

[0002] Structures, such as portions of an aircraft fuselage, can be assembled through the application of fasteners, such as locking bolts, pins secured by nuts, rivets, etc. However, installing fasteners on structures that include contours is particularly difficult because aligning the fasteners with the structure adds complexity. Therefore, installing fasteners on such structures is labor-intensive or requires the use of complex robotics.

[0003] The abstract of EP0956915 states: "A riveting process and installation for the construction of airfoils (e.g., aircraft wings and stabilizers) is described, the installation comprising a rivet head positionably mounted on a carrying bridge; an anvil opposite to said head; and a series of transverse carriages mounted for longitudinal movement with passages below the bridge, the carriages including positionable elements for supporting the airfoil components to be riveted. This entire functional assembly is associated with computer control for the development of an automated riveting process."

[0004] The abstract of U.S. Pat. No. 4,967,947 states: "A machine is described which includes a horizontally extending base having pairs of pylons slidably mounted on opposite sides of the base for horizontal movement along its length, essentially forming a moveable C-frame. A workpiece is fixedly supported on a substrate in a substantially vertical position, with each pair of pylons cooperating on either side of the workpiece to process rivets / fasteners or perform other functions. Each of the pylons includes a vertical first component and a horizontal second component. The second component moves vertically on the first component." The second component is horizontally movable and can move horizontally toward and away from the workpiece. Carried at each end of the horizontal second component adjacent the workpiece is a tool assembly holder rotatable about a horizontal axis and a vertical axis. Each tool assembly holder is adapted to removably receive a tool assembly, each tool assembly consisting of tools for sequentially performing various functions, with the tools on one side of the workpiece axially aligned to cooperate with the tools on the other side, so that the tools on both sides operate simultaneously to perform the desired functions."

[0005] The abstract of JP 2001 / 079637 A states as follows: "Problem: To perform highly precise positioning between the opening of a hole and the area to be riveted by capturing an image of the area to be riveted with a camera and comparing it with the position of the riveting means, thereby detecting the movement of the riveting means. Solution: A position detection means converts data captured by the camera into two-dimensional binary data and detects the center of the area of ​​the image formed by the binary data as the position of the area to be riveted. The detected position of the area to be riveted is compared with the position of at least one of a first moving body and a second moving body. In order to position the drilling means or the riveting means provided on the first moving body and the second moving body relative to the area to be riveted, which is detected based on the result of the comparison, the movement of at least one of the first moving body and the second moving body is detected, and either the riveting means or the workpiece is moved."

[0006] The Abstract of U.S. Patent Application Publication No. 2010 / 122444 states: "The apparatus includes a rail system, a multi-axis carriage, a tool module, and a controller. The rail system can be attached to a surface of a structure. The multi-axis carriage can be coupled to the rail system. The multi-axis carriage can be moved along the rail system and can move a riveting tool in an axis relative to the surface. The tool module can be removably coupled to the multi-axis carriage. The tool module can include a frame and can receive the riveting tool. The controller can control movement of the riveting tool to a number of positions on the surface of the structure and can cause the riveting tool to set a number of rivets at a number of pre-selected positions in response to a signal." Summary of the Invention

[0007] It would therefore be desirable to have a method and system that takes into account at least some of the problems discussed above, as well as other problems that may arise.

[0008] The embodiments described herein provide an end effector positioned on a fixed track that follows the inner mold line (IML) and outer mold line (OML) of a structure to receive a fastener. The fixed track is not attached to the structure itself. Because the fixed track corresponds to the contours of the structure, the end effector is held naturally aligned with the structure when installing a fastener. This relationship remains intact as the end effector moves along the fixed track to install fasteners at different radial locations along the structure. The above configuration also allows the structure to move relative to the end effector so that fasteners can be installed at various locations along the length of the structure.

[0009] One embodiment is a method for applying fasteners to a structure, the method including: positioning a first set of end effectors along a fixed inner track that follows an inner mold line (IML) surface of the structure, positioning a second set of end effectors along a fixed outer track that follows an outer mold line (OML) surface of the structure, aligning the first end effectors on the fixed inner track with the second end effector on the fixed outer track, fastening the structure between the first end effectors and the second end effector by press-fitting the first end effectors and the second end effector into the structure, and applying the fasteners to the structure.

[0010] A further embodiment is a non-transitory computer-readable medium embodied with programmed instructions operable, when executed by a processor, to implement a method for applying fasteners to a structure, the method including positioning a first set of end effectors along fixed inner tracks that follow an inner mold line (IML) surface of the structure, positioning a second set of end effectors along fixed outer tracks that follow an outer mold line (OML) surface of the structure, aligning the first end effectors on the fixed inner tracks with the second end effectors on the fixed outer tracks, press-fitting the first end effectors and the second end effectors into the structure to fasten the structure between the first end effectors and the second end effectors, and applying the fasteners to the structure.

[0011] Another embodiment is a system for applying fasteners to a structure. The system includes a fixed inner track along an inner mold line (IML) side and an IML end effector disposed along the fixed inner track and facing the IML surface of the structure. The fixed inner track has a shape that allows the IML end effector to follow the IML surface of the structure. The system further includes a fixed outer track along an outer mold line (OML) side and an OML end effector disposed along the fixed outer track and facing the OML surface of the structure. The fixed outer track has a shape that allows the end effector to follow the OML surface of the structure. A first set of end effectors is configured to operate in coordination with a second set of end effectors to fasten the structure and install the fasteners.

[0012] It is noted that in this application, an end effector is an extension and / or platform and / or multi-axis machine to which an automated tool can be attached, such as a 4-axis or 5-axis machine that includes an automated tool for fastener installation (e.g., drills, clamps, suction elements, crimping tools, etc.) or to which such tools can be connected.

[0013] Other exemplary embodiments (e.g., methods and computer-readable media related to the above-described embodiments) are described below. The above-described features, functions, and advantages may be realized alone in various embodiments or may be combined in other embodiments, further details of which can be found in the following description and with reference to the drawings.

[0014] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which the same reference numerals represent the same elements or types of elements in all the drawings. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic block diagram of a fastener installation system in an exemplary embodiment. [Figure 2] FIG. 7 is a flow diagram illustrating a method for performing fastener installation in an exemplary embodiment using the fastener installation system shown in FIGS. [Figure 3] 2 is a perspective view of a fastener installation system that is a specific embodiment of the general fastener installation system shown in FIG. 1. [Figure 4] 4 is an end view of the fastener installation system of FIG. 3 prior to receiving a structure, in an exemplary embodiment. [Figure 5] 4 is an end view of the fastener installation system of FIG. 3 after receiving a structure, in an exemplary embodiment. [Figure 6] FIG. 4 is a further perspective view of the fastener installation system of FIG. 3 in an exemplary embodiment. [Figure 7] 1 and 3-6 illustrate further methods for performing fastener installation in exemplary embodiments using the fastener installation system shown in FIGS. [Figure 8] 1 and 3-6 illustrate further methods for performing fastener installation in exemplary embodiments using the fastener installation system shown in FIGS. [Figure 9] 1 and 3-6 illustrate further methods for performing fastener installation in exemplary embodiments using the fastener installation system shown in FIGS. [Figure 10] 1 and 3-6 illustrate further methods for performing fastener installation in exemplary embodiments using the fastener installation system shown in FIGS. [Figure 11] FIG. 11 is a flow diagram of an aircraft manufacturing and service method in an illustrative embodiment, in which the methods shown in FIGS. 1 and 7-10 may be employed. [Figure 12] FIG. 1 is a block diagram of an aircraft in an illustrative embodiment that may be manufactured using the fastener installation system illustrated in FIGS. 1 and 3-6 and / or the method illustrated in FIGS. 1 and 7-10. [Figure 13] 13 is a cross-sectional view of a fuselage that can be used in the aircraft of FIG. 12, which can be manufactured using the fastener installation system shown in FIGS. 1 and 3-6 and / or the method shown in FIGS. 1 and 7-10. DETAILED DESCRIPTION OF THE INVENTION

[0016] The accompanying drawings and the following description provide specific exemplary embodiments of the present disclosure. Thus, those skilled in the art will be able to devise various configurations that embody the principles of the present disclosure and fall within the scope of the present disclosure, even though they are not explicitly described or shown herein. Furthermore, any examples described herein are intended to aid in the understanding of the principles of the present disclosure and should not be construed as being limited to such specifically recited examples and conditions. As a result, the present disclosure is not limited to the specific embodiments or examples described below, but is limited by the scope of the claims.

[0017] FIG. 1 is a schematic block diagram of a fastener installation system 100 in one exemplary embodiment. The fastener installation system 100 may comprise one or more workstations in a series of workstations along a pulsed manufacturing line 10 in which components and / or assemblies of components move through the series of workstations via pulsed movements. The fastener installation system 100 may be a particular pulsed line system along the pulsed manufacturing line 10, which may include a series of manufacturing and / or assembly systems through which the components and / or assemblies pass to produce a final assembly. A particular example of the fastener installation system 100 is fastener installation system 300 (see FIGS. 3-6 ). The fastener installation system 100 includes at least one installation station. The installation station 101 includes a fixed inner track 130, a fixed outer track 150, one or more IML end effectors associated with the fixed inner track 130, and one or more OML end effectors associated with the fixed outer track 150. When fastener installation system 100 includes multiple installation stations, a pair 155 of end effectors 140, 160 at a first installation station can operate simultaneously with another pair 155 of end effectors 140, 160 at a second installation station. For example, when enclosure 119 is secured to structure 110, at least one pair of end effectors 140, 160 operates on a front portion of enclosure 119 to install fasteners 102, and at least one other pair of end effectors 140, 160 operates on a rear portion of enclosure 119, with the pairs operating on the front and rear portions simultaneously.

[0018] Fastener installation system 100 (also known as a "fastener installation station" of pulsed manufacturing line 10) includes any system, apparatus, or component operable to utilize a movable inner mold line (IML) end effector and a movable outer mold line (OML) end effector to perform the installation of fasteners 102 on structure 110. Specifically, the IML end effectors are configured to perform fastener installation on a surface of the inner mold line of structure 110, such as IML surface 316 (see FIG. 3). Similarly, the OML end effectors are configured to perform fastener installation on a surface of the outer mold line of structure 110, such as OML surface 318 (see FIG. 3). Examples of IML end effectors are end effectors 342, 344, and 346 shown in FIGS. 3-6, and examples of OML end effectors are end effectors 362, 364, and 366 shown in FIGS. 3-6. The fasteners 102 may be any suitable type of fastener, such as lock bolts, nuts, rivets, and / or interference fit fasteners.

[0019] The fastener installation system 100 is enhanced to provide end effectors 140, 160 on inner and outer fixed tracks between which the structure 110 passes. One example of the fixed inner track 130 is the fixed inner track 330 shown in FIGS. 3-6 , and one example of the fixed outer track is the fixed outer track 350 shown in FIGS. 3-6 . The end effectors 140, 160 operate in a coordinated manner to install fasteners 102 in holes 104 during pauses between pulsed movements of the structure 110 relative to the fixed track. The pulsed movements involve movement of the structure 110 over a length less than the length L of the structure 110. Each pulse can move the fastener installation location 116 from the previous workstation to the next workstation within the fastener installation system 100. During each pause, the fasteners 102 are installed within the installation tracks of the IML and OML end effectors attached to the fixed tracks.

[0020] In this embodiment, structure 110 includes a semi-cylindrical section of a fuselage (i.e., fuselage portion 308 of the fuselage having an open semi-circular cross-section (see FIG. 3 )) that travels along rails 120 or similar structure between a fixed inner track 130 and a fixed outer track 150. Structure 110 includes a curved section 122. Curved section 122 has a radius R; however, the radius of curved section 122 need not be constant along the entire IML surface 316 of structure 110. Structure 110 also includes a longitudinal portion 124, which is a region of the structure that generally extends along a longitudinal axis A of structure 110. Longitudinal portion 124 receives fasteners 102, which are described in further detail below.

[0021] Rails 120 are part of pulsed manufacturing line 10 and facilitate transporting structure 110 for fabrication via pulsed line assembly techniques. During the pulsed movement of structure 110 along fixed tracks, structure 110 can be indexed and fasteners 102 can be installed by coordinated action of an OML end effector traveling along fixed outer track 150 and an IML end effector traveling along fixed inner track 130.

[0022] As shown in FIGS. 3-6 , multiple IML and OML end effectors can be positioned along different radial portions of their corresponding fixed tracks 130, 150 as first and second sets 340, 360 of end effectors. Each OML end effector engages and works in a paired relationship with a corresponding one of the IML end effectors. A controller 174 operates at least one pair of IML and OML end effectors. Any number of paired end effectors 140, 160 can be utilized to perform this function, with each pair 155 of end effectors 140, 160 capable of working within a predefined portion of a semicircle. An example of paired end effectors is shown in FIG. 4 as pairs 354, 356, 358, each having an IML end effector 342, 344, 346 and an OML end effector 362, 364, 366. The size of the pre-segmented portions depends on the number of paired end effector sets. In a further embodiment, each pair of end effectors has a separate pair of tracks. In this way, each IML end effector and each OML end effector of a paired end effector set operates on different tracks 130, 150 from each other when performing operations on the arc.

[0023] While structure 110 is held in its current cross-sectional shape by braces 112, other embodiments may not have these braces 112 or may maintain the shape of structure 110 by other means. One example of braces 112 is shown in FIG. 3 as brace 370. In further embodiments, structure 110 includes sections of fabrication overage / sacrificial material 114 that may be used to facilitate indexing and / or transportation of structure 110 during assembly operations. Structure 110 also includes locations along its length L where it is desirable to attach one or more fasteners 102 (e.g., fastener attachment locations). Fasteners 102 are attached to hoop-shaped portions 126. For example, hoop-shaped portions 126 may be defined at each fastener attachment location 116 and extend at least partially across curved section 122. In some embodiments, structure 110 also includes cutouts (not shown, but which may be created by a later-arriving workstation) into which enclosures 119 may be placed. Enclosure 119 can be secured to structure 110 at a forward portion, an aft portion, and / or a perimeter of enclosure 119. This can depend on the workstation and / or pulsed line system. For example, some workstations can attach a frame, such as frame 1140 (see FIG. 13), to structure 110 including a skin, such as skin 1142 (see FIG. 13), while other workstations can attach enclosure 119 around a location where an opening in structure 110 is attached.

[0024] Structure 110 has a radius R. The radius (R_INNER) of fixed inner track 130 (including IML end effector 140) is less than R. Furthermore, the radius (R_OUTER) of fixed outer track 150 (including OML end effector 160) is greater than R. However, fixed inner track 130 and fixed outer track 150 do not need to have fixed radii along their entire lengths, as long as there is a gap G for structure 110 to pass through. This is because end effectors 140, 160 can compensate for any variations in the distance between the location of a particular track and the IML surface (e.g., IML surface 316 in FIG. 3 ) or OML surface (e.g., OML surface 318 in FIG. 3 ) of structure 110. This means that structure 110 can move through gap G between IML end effector 140 and OML end effector 160 without hindrance. In this manner, fixed outer track 150 is disposed on OML side 106 of system 100 and / or structure 110 and has a shape that allows OML end effector 160 to follow the OML surface of structure 110. Similarly, fixed inner track 130 is disposed along IML side 108 of fastener installation system 100 and / or structure 110 and has a shape that allows IML end effector 140 to follow the IML surface of structure 110.

[0025] The IML end effector 140 and the OML end effector 160 may include, for example, four-axis or five-axis machines that include automated tools for fastener installation (e.g., drills, clamps, suction elements, crimping tools, etc.). In further embodiments, the end effectors 140, 160 described herein can extend, retract, or otherwise reposition to address separation between their tracks 130, 150 and the IML surface (e.g., IML surface 316 shown in FIG. 3 ) or OML surface (e.g., OML surface 318 shown in FIG. 3 ) of the structure 110. The end effectors 140, 160 can perform this action regardless of whether the amount of separation varies along the tracks 130, 150.

[0026] In a further embodiment, the radius of the fixed inner track 130 and the radius of the fixed outer track 150 vary as the operation progresses, and the associated end effectors 140, 160 move dynamically to accommodate the varying distances from the tracks 130, 150 to the structure 110. In yet a further embodiment, fixed tracks of different radii occupy different sides of the structure 110 to help avoid end effector collisions. For example, the right fixed outer track 150 exhibits a radius of 10 feet (3.05 m), the left fixed outer track 150 exhibits a radius of 11 feet (3.35 m), and the center fixed outer track 150 exhibits a radius of 10.5 feet (3.20 m).

[0027] The operation of the IML end effector 140 and the OML end effector 160 is coordinated via a server 170. In one embodiment, a controller 174 of the server 170 accesses numerical control (NC) program instructions stored in a memory 176 and sends the instructions via an interface (i.e., I / F 172) to manage the operation of the end effectors 140, 160. The controller 174 may be implemented, for example, as custom circuitry, as a hardware processor executing programmed instructions, or some combination thereof.

[0028] Exemplary details of the operation of fastener installation system 100 are described in connection with Figure 2. In one embodiment, structure 110 has completed inspection via non-destructive imaging (NDI) technology and is ready to pass between fixed inner track 130 and fixed outer track 150 to begin fastener installation. Furthermore, in this embodiment, fixed inner track 130 is complementary to (e.g., matches) the contour of the inner surface (e.g., IML) of structure 110, and fixed outer track 150 is complementary to the contour of the outer surface (e.g., OML) of structure 110.

[0029] 2 is a flow diagram illustrating a method 200 for operating a fastener installation system, in one exemplary embodiment. The steps of method 200 are described with reference to fastener installation system 100 of FIG. 1, but one of ordinary skill in the art will understand that method 200 may be implemented in other systems. The steps of the flow diagrams described herein are not exhaustive and may include other steps not shown. The steps described herein may also be implemented in a different order.

[0030] As shown in FIGS. 1 and 2 , in step 202, a first set of one or more IML end effectors (e.g., first set 340 shown in FIG. 3 ) are positioned along a fixed inner track 130. The fixed inner track 130 facilitates movement of the IML end effectors following the curved IML of the structure 110. For example, the IML end effectors move without hitting the IML surface of the structure 110 (e.g., IML surface 316 shown in FIG. 3 ), yet remain close enough to contact the IML surface of the structure 110 at selected locations along the IML surface of the structure 110 to install the fasteners 102. The first set of IML end effectors can include end effectors 140 that each occupy a different radial portion of the fixed inner track 130 (and thus each follow a different arc complementary to the curved IML of the structure 110). One example of this is shown in FIGS. 3-6 . Any number N of IML end effectors can be positioned to pair with the OML end effectors described below with respect to step 204. Positioning 202 the IML end effectors along the fixed inner track 130 can include attaching the IML end effectors to the fixed inner track 130 such that the IML end effectors can adjust their position along the structure 110 (e.g., by advancing along the track 130).

[0031] In step 204, one or more second sets of OML end effectors (e.g., second set 360 shown in FIG. 3 ) are positioned along fixed outer track 150. Fixed outer track 150 facilitates movement of the OML end effectors following the curved OML of structure 110. For example, the OML end effectors move without hitting the OML surface of structure 110 (e.g., OML surface 318 shown in FIG. 3 ), yet remain close enough to contact the OML surface of structure 110 at selected locations along the OML surface of structure 110 to install fasteners 102. The second set of OML end effectors can include end effectors that each occupy a different radial position along fixed outer track 150, as shown in FIGS. 3-6 . Positioning the OML end effectors along the fixed outer track 150 may include attaching the OML end effectors to the fixed outer track 150 so that the end effectors can adjust their position along the structure 110 (e.g., by advancing along the fixed outer track 150).

[0032] One aspect of positioning 202 the first set 340 and positioning 204 the second set 360 includes assigning the end effectors 140, 160. Specifically, as shown in Figures 1, 2, and 4, the method 200 may include assigning the end effectors 140, 342, 344, 346 of the first set 340 to different radial zones 410, 420, 430 of the structure 110, 310, and assigning the end effectors 160, 362, 364, 366 of the second set 360 to different radial zones 410, 420, 430 of the structure 110, 310. Each end effector 140, 342, 344, 346 of the first set 340 and each end effector 160, 362, 364, 366 of the second set 360 operates exclusively within the radial zones 410, 420, 430 to which the end effectors 140, 342, 344, 346 and 160, 362, 364, 366 are assigned.

[0033] In step 206, a first end effector along a fixed inner track (e.g., IML end effector 140 along fixed inner track 130) and a second end effector along a fixed outer track (e.g., OML end effector 160 along fixed outer track 150) are aligned. Alignment may include placing both the first and second end effectors at the same location / position along the curvature of structure 110. Structural components that are desired to be secured to structure 110 may also be aligned with end effectors 140, 160. For example, in embodiments where the structure 110 is a fuselage section 308 of a fuselage (e.g., fuselage 1119 shown in FIGS. 12 and 13 ), a curved frame of the fuselage, e.g., frame 1140 (see FIG. 13 ), is aligned with the end effector 140, 160 such that installation of fasteners 102 secures the frame 1140 to a skin panel of the fuselage 1119 (e.g., skin panel 1142 shown in FIG. 13 ). The frame 1140 itself can be indexed, if desired, using notches or holders located in the fixed inner track 130. In this manner, the portion of the inner track 130 that is fixed relative to the structure 110 is used to position and hold the frame 1140 for installation on the IML surface of the structure 110. In further embodiments, the frame 1140 is held by guides or rails that are separate from other components, such as those described herein.

[0034] Any structure directly coupled to the structure 110 (e.g., the skin 1142 of the fuselage 1119 shown in FIG. 13 ) can be installed through the action of the end effectors 140, 160 described herein. Such structures include door or window enclosures, such as enclosure 119. Fasteners 102 for a door or window enclosure within the reach of the pair 155 of end effectors 140, 160 can be installed during one pause between pulses of the fuselage structure, and then fasteners 102 within the reach during the next pause between pulses can be installed by the same end effector. In this manner, fasteners 102 around the perimeter of the opening in the structure 110 are installed. In a further embodiment, the structural component may include another section of the fuselage that is joined longitudinally with the current section of the fuselage to form a longer fuselage section. In yet a further embodiment, fuselage panels, each comprising a portion of the fuselage radius, can be joined with a longitudinal butt or lap splice to form a more complete fuselage section around the perimeter.

[0035] In a further embodiment, the IML and OML end effectors can be moved longitudinally relative to the structure 110 to install longitudinal splice fasteners within the specific reach of one of a series of workstations, as described in further detail with reference to FIG. 3 . These end effectors 140, 160 can move horizontally over short lengths and install splice fasteners to assemble hemi-tubular sections from individual cylindrical sections, each containing one-sixth of a tube. These smaller cylindrical sections are fastened together with temporary fasteners before permanent fastener installation. This fastener installation system 100 can be used to form hemi-tubular sections for the manufacture of composite or metal aircraft. In this manner, metal aircraft can be assembled on a pulsed line.

[0036] In step 208, the structure 110 is fastened by press-fitting a first end effector, e.g., the IML end effector 140, and a second end effector, e.g., the OML end effector 160, into the structure 110. For example, a "one-up" fastening is performed via application of a suction element of one of the end effectors 140, 160 to the structure 110, or by forcing the end effector 140 of the fixed inner track 130 against the structure 110 and the end effector 160 of the fixed outer track 150 to sandwich the structure 110 in place between the end effectors 140, 160. This allows for sealing, drilling, and fastener installation in a single process, thereby eliminating the need to line up and drill all of the holes 104 in the panel assembly, and allowing the structure to be disassembled for cleaning and deburring prior to sealant application, reassembly, and fastener installation. Drilling the fastener holes may include drilling countersink holes.

[0037] In step 210, the fastener 102 is applied to the structure 110. Applying the fastener 102 to the structure 110 may include drilling a hole 104 through the structure 110 using at least one of the end effectors 140, 160. For example, in one embodiment where the fastener 102 is a lock bolt, the second end effector may drill the hole 104 in the structure 110 and drive the lock bolt through the hole 104, and the first end effector may place a collar on the lock bolt and swage the collar in place. In one embodiment, applying the fastener 102 includes inserting the fastener 102 into the fastener hole 104. In one embodiment, structure 110 comprises fuselage section 308 (see FIG. 3 ) of an aircraft fuselage, and applying fasteners 102 includes driving the fasteners through an IML surface (e.g., IML surface 316 shown in FIG. 3 ) of structure 110 (e.g., fuselage section 308 shown in FIG. 3 ) and a frame (e.g., frame 1140 shown in FIG. 13 ) disposed on structure 110 itself. During steps 208 and 210, forces applied during fastening and fastener installation are transferred through end effectors 140, 160 to fixed tracks 130, 150. In step 212, structure 110 is released by separating the first end effector and the second end effector from structure 110. After step 212, the end effectors 140, 160 may be moved to a different fastener installation location 116 on the structure 110, and / or the structure 110 may be moved to a subsequent workstation and / or pulsed line system in the pulsed manufacturing line 10.

[0038] Steps 206-212 can be repeated multiple times, with the structure 110 paused at the same workstation or in front of a different workstation each time to install multiple fasteners 102 along a different radial location. An iteration can include moving the first and second end effectors to a new position along the curvature of the structure 110 (e.g., see step 206), fastening 208 the structure 110 by press-fitting the first and second end effectors into the structure 110, and applying another fastener 102 to the structure 110.

[0039] Method 200 can provide substantial technical benefits over prior art solutions because it can ensure that movable end effectors, e.g., end effectors 140, 160, are available to install fasteners 102 at various locations along the contoured structure 110. Furthermore, because end effectors 140, 160 are positioned along fixed tracks, e.g., tracks, they can reliably install fasteners 102 at the same location along the contour of structure 110 regardless of the amount of distance structure 110 has traveled along rail 120. Thus, unlike flexible track systems that may require installation and removal of tracks within the fuselage itself (e.g., for each of multiple sections along the length of the fuselage), fastener installation system 100 with fixed tracks described herein can be operated quickly by moving structure 110 lengthwise, pausing structure 110, applying fasteners 102, and then moving structure 110 lengthwise again. Moving lengthwise moves structure 110 in longitudinal direction 103.

[0040] Additionally, a flexible track system can rely on an already assembled structure to provide structural support for the track, and method 200 utilizes a track that is structurally independent of structure 110. Furthermore, a flexible track system may require the track and end effector to be moved to a specific location on structure 110. In this system, structure 110 moves onto the track, and fasteners 102 are pulsed onto structure 110 midway along pulsed manufacturing line 10. Thus, after each pulse of structure 110 movement, structure 110 can quickly index onto the track before starting work. The fastener installation is then performed, the work is stopped, and the next portion of structure 110 is moved into range of end effectors 140, 160 on the fixed track for additional fastener assembly.

[0041] 3-6 illustrate fastener installation in a particular embodiment, where structure 110 (see FIG. 1) is a fuselage section 308 having a constant cross-section along its length, such as structure 310 comprising a semi-cylindrical section of the fuselage. Fuselage section 308 described with reference to FIGS. 3-6 may be a portion of fuselage 1119 shown in FIG. 12.

[0042] FIG. 3 is a perspective view of a fastener installation system 300 in an exemplary embodiment. This fastener installation system 300 is a specific example of the fastener installation system 100 shown generally in FIG. 1. In this embodiment, the fastener installation system 300 includes rails 320 mounted to a factory floor 322. The rails 320 are an example of the rails 120 shown in FIG. 1. The rails 320 move a structure 310 in the longitudinal direction 103 toward and / or through the fastener installation system 300. A mobile cart 314 travels along the rails 320 and includes clamps 312 that hold the structure 310 in the form of a semi-cylindrical section of an aircraft fuselage (e.g., fuselage 1119 shown in FIGS. 12 and 13 ) having an IML surface 316 and an OML surface 318. Braces 370 located at the ends of the structure 310 help maintain the arcuate shape of the structure 310 during transport. However, in further embodiments, the braces 370 are omitted. Brace 370 is one embodiment of brace 112 shown in FIG.

[0043] During the assembly operation, structure 310 rides within gap G between fixed inner track 330 and fixed outer track 350. Fixed inner track 330 is an example of fixed inner track 130 shown in FIG. 1 , and fixed outer track 350 is an example of fixed outer track 150 shown in FIG. 1 . Fixed inner track 330 is positioned on IML side 108 of fastener installation system 300 and / or structure 310, and fixed outer track 350 is positioned on OML side 106 of fastener installation system 300 and / or structure 310. Fixed inner track 330 has a first set 340 of end effectors 342, 344, and 346 arranged along a first semicircle 332. End effectors 342, 344, and 346 are each an example of IML end effector 140 shown in FIG. 1 . Fixed outer track 350 has a second set 360 of end effectors 362, 364, and 366 arranged along a second semicircle 352. End effectors 362, 364, and 366 are each an example of OML end effector 160 shown in FIG. 1. As shown in FIG. 4, each IML end effector 342, 344, and 346 is paired with a respective OML end effector 362, 364, and 366 to create end effector pairs 354, 356, and 358. Each pair 354, 344, and 346 is an example of pair 155 shown in FIG. 1. Although three pairs 354, 356, and 358 of end effectors are shown in FIGS. 4-6, fastener installation system 300 can include any number of pairs 354, 356, and 358.

[0044] As shown in FIG. 3 , second semicircle 352 is larger (i.e., has a larger diameter) than first semicircle 332 and is concentric with first semicircle 332. When structure 310 is positioned between first semicircle 332 and second semicircle 352, IML surface 316 and OML surface 318 are also concentric with first semicircle 332. Movement of structure 310 in the direction indicated by the arrows is periodically paused, causing structure 310 to move in pulses as structure 310 advances between fixed tracks 330, 350. During each pause, end effectors 342, 344, 346 and 362, 364, 366 of tracks 330, 350 install fastener 102 (see FIG. 5 ) in hole 104 (see FIG. 5 ) along the contour of structure 310. Structure 310 then moves again to present another hoop-like (or half-cylinder-shaped) portion of structure 310 along length L of structure 310 for receiving fastener 102 .

[0045] In a further embodiment, structure 310 pulses longitudinally 103 through fastener installation locations, e.g., a distance equal to the spacing between fastener installation locations (see FIG. 1), to install longitudinal rows of fasteners, e.g., for lap or butt splices joining fuselage panels. In yet a further embodiment, multiple end effector pairs install fasteners 102 for longitudinal joints and then switch to installing hoop fasteners for attaching a frame, e.g., securing frame 1140 to skin panel 1142 as shown in FIG. 13.

[0046] In one embodiment, the end effectors 342, 344, 346 and 362, 364, 366 on the fixed inner track 330 and fixed outer track 350 are also capable of limited longitudinal movement in the longitudinal direction 380, as indicated by the arrow. The OML end effectors 362, 364, 366 move in the longitudinal direction 380 in synchronization with the IML end effectors 362, 364, 366. In such an embodiment, the IML end effectors 342, 344, 346 are coupled to the fixed inner track 330 via inner longitudinal rails 372. Similarly, the OML end effectors 362, 364, 366 are coupled to the fixed outer track 350 via outer longitudinal rails 3734. The IML end effectors 342, 344, 346 move longitudinally 380 along inner longitudinal rails 372 relative to the fixed inner track 330. The OML end effectors 362, 364, 366 move longitudinally 380 along outer longitudinal rails 374 relative to the fixed outer track 350. This can facilitate certain assembly operations, such as those involved in making longitudinal splices.

[0047] Figure 4 is an end view of fastener installation system 300 prior to receiving structure 310, corresponding to arrow 4 in Figure 3. In Figure 4, a controller, such as controller 174 shown in Figure 1, has IML end effectors 342-346 assigned to different radial zones 410, 420, 430 of structure 310, and also has OML end effectors 362-366 assigned to different radial zones 410, 420, 430 of structure 310. Although three pairs 354, 356, 358 of end effectors and three radial zones 410, 420, 430 are shown, further embodiments may utilize any suitable number of pairs and radial zones.

[0048] Each IML end effector 342, 344, 346 of first set 340 and each OML end effector 362, 364, 366 of second set 360 operates exclusively within its assigned radial zone 410, 420, or 430. Specifically, end effectors 342, 344, 346 and 362, 364, 366 are grouped into pairs 354, 356, 358 (one inner end effector and one outer end effector), with each pair operating in a coordinated manner to install fasteners 102 in a separate radial zone / portion 410, 420, 430 of structure 310. For example, end effector 342 and end effector 362 operate together as pair 354 in radial zone 410 located between boundary line 402 and boundary line 412, end effector 344 and end effector 364 operate together as pair 356 in radial zone 420 located between boundary line 412 and boundary line 422, and end effector 346 and end effector 366 operate together as pair 358 in radial zone 430 located between boundary line 422 and boundary line 432.

[0049] In further embodiments, the radial zones 410, 420, 430 are not exclusive and therefore overlap, thereby improving the ability of the end effectors 342, 344, 346 and 362, 364, 366 to perform fastener installation in the boundary areas between the radial zones. For example, at least two of the radial zones 410, 430 overlap with another radial zone 420. The actions performed by the end effector pairs 354, 356, 358 are coordinated to prevent collisions between the end effectors 342, 344, 346 and 362, 364, 366 of different pairs. For example, the controller 174 operates the pairs of end effectors 354, 356, 358 such that the end effectors 342, 344, 346 and 362, 364, 366 travel together in a first circumferential direction (e.g., clockwise) across their respective radial portions and then travel in a second circumferential direction (e.g., counterclockwise) across their respective radial portions, thereby ensuring that the pairs of end effectors 354, 356, 358 are maintained separated by a desired amount of free space to prevent collisions.

[0050] In one embodiment, the movements of the end effectors 342, 344, 346 and 362, 364, 366 are programmed into NC programming stored in memory 176 (see FIG. 1 ) of the end effectors 342, 344, 346 and 362, 364, 366 to aid in collision avoidance. In a further embodiment, the NC programming is supplemented with proximity sensors (e.g., laser sensors, cameras, ultrasonic sensors, etc.) that provide input used by the controller 174 to automatically pause or modify the operation of the end effectors 342, 344, 346 and 362, 364, 366 to implement collision avoidance. In this manner, fastener installation may include moving the first set of end effectors 340 and the second set of end effectors 360 along a first circumferential direction, e.g., clockwise direction 450, to apply a plurality of fasteners 102, and moving the first set of end effectors 340 and the second set of end effectors 360 along a second circumferential direction opposite the first circumferential direction, e.g., counterclockwise direction 452, to install additional fasteners (e.g., after the structure 310 has moved in a pulsed manner).

[0051] Figure 5 is an end view of fastener installation system 300 after receiving structure 310. That is, structure 310 has pulsed along rails 320 to a position where a portion of structure 310, ready for fastener installation, is positioned between fixed inner track 330 and fixed outer track 350. In Figure 5, structure 310 is positioned between fixed inner track 330 and fixed outer track 350. For this illustration, it is assumed that the movement of structure 310 has paused. This end view also shows curved section 122 of structure 310.

[0052] End effector pairs 354, 356, 358 advance in a hoop direction to install fasteners 102 into holes 104 in their corresponding zones 410, 420, 430 as end effectors 342, 344, 346 and 362, 364, 366 perform coordinated sweeps in a clockwise or counterclockwise direction (or both) during fastener installation. In one embodiment, end effectors 342, 344, 346 and 362, 364, 366 start in the positions shown in FIG. 5 and work in a counterclockwise direction 452 until they stop at the far end of a counterclockwise arc. End effectors 342, 344, 346 and 362, 364, 366 then wait until the next pause / movement of structure 310 and work in a clockwise direction 450 toward the starting point shown in FIG. 5. That is, each time structure 310 is pulsed through fastener installation system 300, end effectors 342, 344, 346 and 362, 364, 366 switch their direction of motion from counterclockwise direction 452 to clockwise direction 450. In this manner, end effectors 342, 344, 346 and 362, 364, 366 all operate in counterclockwise direction 452, then wait for a pulsed movement, then operate in clockwise direction 450, then wait for a pulsed movement, and so on. This repeated coordinated movement between end effectors 342, 344, 346 and 362, 364, 366 and structure 310 can be accomplished without any kind of "carriage return" type movement.

[0053] In another embodiment, end effector pairs 354, 356, 358 install fasteners 102 in a clockwise direction 450 until they reach the end of their radial zones 410, 420, or 430, and then reset in a counterclockwise direction 452 back to the beginning of their radial zones 410, 420, 430 in a manner similar to the carriage return motion of a typewriter. In this manner, after a pulsed movement, end effector pairs 354, 356, 358 all work in a clockwise direction 450, then return to their starting positions, and work in a clockwise direction 450 again after the next pulsed movement. Of course, similar operations may be performed for counterclockwise movement instead of clockwise movement.

[0054] In yet a further embodiment, after structure 310 is pulsed, end effectors 342, 344, 346 and 362, 364, 366 move incrementally in one direction (e.g., clockwise, counterclockwise) as each end effector 342, 344, 346 and 362, 364, 366 advances across its radial zone 410, 420, 430, installing fastener 102 within hole 104 during the pulse. End effectors 342, 344, 346 and 362, 364, 366 then move in the opposite direction back to their starting positions to prepare for installing fastener 102 after structure 310 is again pulsed. The structure 310 can then be pulsed to the next fastener installation location on the structure 310 (see FIG. 1 ), with the pair of end effectors 354, 356, 358 proceeding to install the fastener within the hole 104 as the pair 354, 356, 359 moves in the counterclockwise direction 452.

[0055] In yet a further embodiment, fixed tracks 330, 350 are positioned near the respective IML or OML surfaces 316, 318 of structure 310 such that IML end effectors 362, 364, 366 are positioned between structural portions of fixed inboard track 330 (or further inboard of fixed inboard track 330), with fixed inboard track 330 positioned a short distance away from IML surface 316 on which operations are performed. In a similar manner, OML end effectors 362, 364, 366 are positioned between structural components of fixed outboard track 350 (or further inboard of fixed outboard track 350), with fixed outboard track positioned a short distance away from OML surface 318 on which operations are performed.

[0056] In yet a further embodiment, one longitudinally moving end effector is provided per rail 320. As shown in Figures 1 and 3, fastener installation system 300 can also have adjacent frame installation stations 101, with end effectors 342, 344, 346 and 362, 364, 366 at each station 101 operating in different or the same circumferential direction, e.g., clockwise 450 or counterclockwise 452 (e.g., to install a splice between half-cylindrical sections or to install a window or door surround). Each frame installation station of fastener installation system 300 includes a fixed inner track 330, a fixed outer track 350, one or more IML end effectors 342, 344, 346 associated with fixed inner track 330, and one or more OML end effectors 362, 364, 366 associated with fixed outer track 350.

[0057] Figure 6 is a further perspective view of fastener installation system 300, corresponding to arrow 6 in Figure 3. As shown in Figure 6, the clearance C between IML end effectors 342, 344, 346 along fixed inner track 330 and OML end effectors 362, 364, 366 along fixed outer track 350 is greater than the thickness T of brace 370. This spacing allows structure 310 to ride between fixed tracks 330, 350 without encountering physical interference.

[0058] 7-11 illustrate additional methods for performing fastener installation using the fastener installation system 100, 300 (see FIGS. 1 and 3). Methods 700, 800, 900, and 1000 include pulsating the structure 110, 310 toward and / or through the fastener installation system 100, 300. The pulsating movement enables the methods 700, 800, 900, 1000 to install the fasteners 102 by installing the fasteners 102 along the longitudinal axis A of the structure 110, 310, installing the fasteners 102 along the longitudinal portion 124 of the structure 110, 310. Installing the fasteners 102 can secure a component such as a frame 1140 (see FIG. 13) or an enclosure 119 (see FIGS. 1 and 13) to the structure 110, 310 (e.g., a fuselage section 308 having a skin 1142).

[0059] Method 700 provides another technique for utilizing the end effector and track system described herein, in one exemplary embodiment. According to method 700 of FIG. 7, step 702 includes pulsing a structure 110, 310 (see FIGS. 1 and 3 ) including a fastener installation location 116 toward the fastener installation system 100, 300. For example, the structure 110, 310 moves in the longitudinal direction 103 shown in FIG. 3 . During the pulsing movement, the structure 110, 310 moves along rails 120, 320 that are part of the pulsed production line 10. In one embodiment, the pulsing movement includes moving the structure 110 longitudinally (e.g., a distance of 2.44 meters (8 feet)) toward and / or through the fastener installation system 100, 300. For example, during the pulsing movement, the structure 110, 310 moves in the longitudinal direction 103 a predetermined distance. The movement of the structure 110, 310 is then paused to allow the fastener installation system 100, 300 to perform the task.

[0060] In step 704, at least one fastener 102 is installed at the fastener installation location 116 via end effectors 140, 342, 344, 346 and 160, 362, 364, 366 (see FIGS. 1 and 3) supported by tracks 130, 330 and 150, 350 (see FIGS. 1 and 3) that are independent of the structure 110, 310. Step 704 may be performed via the coordinated end effector motion described above with respect to method 200 of FIG. 2. The installation may include installing the fastener 102 along a curved section 122 (see FIG. 5) of the structure 110, 310. Additionally, the installation may include installing the fastener 102 along a longitudinal portion 124 of the structure 110, 310. Longitudinal motion may further support installation of the fastener 102 for a door surround, stringer splice, or other component.

[0061] Method 800 provides yet another technique for utilizing the end effector and track system described herein, in one exemplary embodiment. According to method 800 of FIG. 8, step 802 includes pulsing a structure 110, 310 including a fastener installation location 116 toward a fastener installation system 100, 300 (see FIGS. 1 and 3). In one embodiment, pulsing 802 the structure 110, 310 includes moving the structure 110, 310 longitudinally toward and / or through the fastener installation system 100, 300 (e.g., 4 feet, 8 feet, etc.). Movement of the structure 110, 310 is then paused to allow the fastener installation system 100, 300 to perform an operation. This is similar to step 702 of method 700 of FIG. 7.

[0062] In step 804, the structure 110 is fastened between the IML end effectors 140, 342, 344, 346 and the OML end effectors 160, 362, 364, 366 of the fastener installation system 100, 300. Fastening 804 may be performed by forcing the end effectors 140, 342, 344, 346 and 160, 362, 364, 366 toward each other while the end effectors are positioned over the fastener installation location 116, as described with respect to steps 206 and 208 of FIG. 2. Step 804 is performed while movement of the structure 110, 310 is paused.

[0063] In step 806, the fastener 102 is installed in the structure 110, 310 via the IML end effectors 140, 342, 344, 346 and the OML end effectors 160, 362, 364, 366. The installation step may include the end effectors 140, 342, 344, 346 and 160, 362, 364, 366 drilling the hole 104, cleaning the hole 104, and installing the fastener 102 in the hole 104 at the desired location. This may be performed via the coordinated end effector movements described above with respect to the method 200 of FIG. 2, specifically via step 210. The installation may include installing the fastener 102 along the curved section 122 (see FIG. 5) of the structure 110, 310. Additionally, the attachment may include attaching the fasteners 102 along the longitudinal portion 124 of the structure 110,310.

[0064] In further embodiments, one-up assembly can be performed as method 800 via the end effectors 140, 342, 344, 346 and 160, 362, 364, 366 described herein, where forces applied by the end effectors 140, 160 during drilling and fastener installation are resisted by one or more indexing elements that hold the structure 110, 310 in place. Additionally, forces applied during fastening 804 and fastener installation are transmitted through the end effectors 140, 160 into the tracks 130, 150.

[0065] Method 900 provides a technique for utilizing end effectors that move longitudinally / lengthwise relative to a structure to facilitate fastener installation. Method 900 can be used when fastener installation system 100, 300 has end effectors 342, 344, 346 and 362, 364, 366 in fixed inner track 330 and fixed outer track 350 that are capable of longitudinal movement limited to longitudinal direction 380 shown in FIG.

[0066] According to method 900, step 902, similar to steps 702 and 802 described with respect to Figures 7 and 8, involves longitudinally pulsating structure 110, 310, including fastener installation location 116, toward and / or through fastener installation system 100, 300. In step 904, at least one fastener 102 is installed at fastener installation location 116 via end effectors 140, 342, 344, 346 and 160, 362, 364, 366 disposed on IML surface 316 and OML surface 318 of structure 110, 310. Installation step 904 is similar to step 802 (see Figure 8), step 704 (see Figure 7), and step 210 (see Figure 2).

[0067] In step 906, the end effectors 140, 342, 344, 346 and 160, 362, 364, 366 are moved longitudinally 380 relative to the structures 110, 310. For example, the end effectors 140, 342, 344, 346 and 160, 362, 364, 366 are moved by independently advancing longitudinally 380 along inner longitudinal rails 372 and outer longitudinal rails 374 relative to the fixed inner tracks 130, 330 and fixed outer tracks 150, 350, respectively.

[0068] In step 908, additional fasteners are installed via end effectors 140, 342, 344, 346 and 160, 362, 364, 366 after the end effectors 140, 342, 344, 346 and 160, 362, 364, 366 have moved. The installation is similar to step 904, and steps 904 and 908 can be performed as described with respect to method 200 (see FIG. 2). The installation can include installing fasteners 102 along curved sections 122 (see FIG. 5) of structures 110, 310. Additionally, installation 904, 908 can include installing fasteners 102 along longitudinal portions 124 of structures 110, 310. In this manner, end effectors 140, 342, 344, 346 and 160, 362, 364, 366 install fasteners 102 along longitudinal portions 124 of newly exposed structures 110, 310. In further embodiments, end effectors 140, 342, 344, 346 and 160, 362, 364, 366 also move in an arc relative to structures 110, 310 during fastener installation, such as in a clockwise direction 450 and / or a counterclockwise direction 452, as shown in FIG. In the manner of method 900, even though the structures 110, 310 are already pulsating longitudinally in a periodic manner, the end effectors 140, 342, 344, 346 and 160, 362, 364, 366 can perform a limited amount of longitudinal movement to further facilitate longitudinal splices, stringer splices, or during attachment of intercostal sections, enclosures, clips / supports, etc.

[0069] Method 1000 illustrates a technique for installing an enclosure, such as the enclosure 119 shown in FIGS. 1 and 13, in one exemplary embodiment. Step 1002 involves pulsing a structure 110, 310 having fastener installation locations 116 toward and / or through a fastener installation system 100, 300. Step 1002 is similar to steps 902, 802, and 210 described above. Step 1004 involves installing a first subset of fasteners 102 for the enclosure 119 (e.g., a door enclosure, a window enclosure, etc.) over a cutout to be subsequently located in the structure 110, 310 via end effectors 140, 342, 344, 346 and 160, 362, 364, 366 supported by tracks 130, 330 and 150, 350 independent of the structure 110, 310. The first subset of fasteners 102 may include fasteners 102 currently installed in locations within reach of end effectors 140, 342, 344, 346 and 160, 362, 364, 366. Installation 1004 of fasteners 102 is similar to the manner in which fasteners 102 are installed in method 200 (see FIG. 2) described above.

[0070] Step 1006 further includes pulsing the structure 110, 310 through the fastener installation system 100, 300. This operation is similar to step 1002, with the end effectors 140, 342, 344, 346 and 160, 362, 364, 366 creating remaining positions for installing fasteners 102 in the available enclosure 119. After each pulsing step (which may include the pulsing steps described with reference to FIGS. 7-9 ), the method 1000 may include indexing the structure 110, 310. For example, the structure 110, 310 may be indexed using the sections of fabrication overage / sacrificial material 114, using notches or holders located in the fixed inner track 130 and / or the fixed outer track 150, and / or using one or more indexing elements that hold the structure 110, 310 in place.

[0071] In step 1008, a second subset of fasteners 102 is installed for enclosure 119 via end effectors 140, 342, 344, 346 and 160, 362, 364, 366, similar to step 1004. In one embodiment, installing 1008 the second subset of fasteners 102 includes distributing the fastener installation operations for enclosure 119 across different end effectors. The installing step secures enclosure 119 to structure 110, 310 such that the enclosure covers the cutout in structure 110, 310. The installing step can be performed by at least one pair of end effectors 140, 160 operating on a forward portion of enclosure 119 and by at least one other pair of end effectors 140, 160 operating on a rearward portion of enclosure 119, with pair 115 operating on both the forward and rearward portions simultaneously.

[0072] Additionally, the installation of the fastener 102 can include installing the fastener 102 along the curved section 122 (see FIG. 5 ) of the structure 110, 310. Additionally, the installation 1004, 1008 can include installing the fastener 102 along the longitudinal portion 124 of the structure 110, 310.

[0073] Installing the fasteners described in methods 200, 700, 800, 900, and 1000 above may include installing fasteners 102 along the hoop portion 126 of the structure 110, 310, installing fasteners 102 along the length L of the structure 110, 310, securing an enclosure 119 over a cutout in the structure 110, 310 (e.g., by installing fasteners along the perimeter of the enclosure 119 via different end effectors), securing a frame 1140 to an outer skin 1142 of the structure 110, 310 (see FIG. 13 ), etc. Methods 700, 800, 900, and 1000 include repeatedly pulsing the structure 110, 310 toward and / or through the fastener installation system 100, 300 and installing fasteners 102 in the structure 110, 310.

[0074] In one embodiment, the method further includes aligning an outer mold line (OML) end effector and an inner mold line (IML) end effector with the structure and installing the fastener via the OML and IML end effectors. Another possible additional step may include indexing the structure after pulsing the structure. This may include positioning the structure in a known position relative to the track (e.g., by positioning the structure relative to an indexing element whose position is fixed relative to the track) to determine the structure's position in a coordinate space used by the OML and IML end effectors. In a further embodiment, the installing is performed by at least one pair of end effectors operating at a front portion of the enclosure and at least one pair of end effectors operating at a rear portion of the enclosure, the pairs operating simultaneously.

[0075] Example In the following examples, additional processes, systems, and methods are described in terms of a fastener installation system. Any or all of the methods 200, 700, 800, 900, and 1000 described herein may be embodied in a non-transitory computer-readable medium as programmed instructions.

[0076] 11 and 12 in more detail, embodiments of the present disclosure may be described in terms of an aircraft manufacturing and service method 1100 shown in FIG. 11 and an aircraft 1102 shown generally in FIG. 12. During pre-production, method 1100 may include specification and design 1104 of the aircraft 1102 and material procurement 1106. During production, component and subassembly manufacturing 1108 and system integration 1110 of the aircraft 1102 occurs. Methods 200, 700, 800, 900, and 1000 (see FIGS. 2 and 7-10) may be performed during component and subassembly manufacturing 1108.

[0077] The aircraft 1102 then goes through certification and delivery 1112 and is placed into service 1114. While in service with a customer, the aircraft 1102 is scheduled for routine maintenance and service 1116 (which may include modification, reconfiguration, refurbishment, etc.). Systems and methods embodied herein may be employed at any suitable stage or stages of the production and service described in method 1100 (e.g., specification and design 1104, materials procurement 1106, component and subassembly manufacturing 1108, system integration 1110, certification and delivery 1112, operation 1114, maintenance and service 1116) and / or any suitable component of the aircraft 1102 (e.g., airframe 1118, systems 1120, interior 1122, propulsion system 1124, electrical system 1126, hydraulic system 1128, environmental system 1130).

[0078] Each of the processes of method 1100 may be performed or carried out by a system integrator, a third party, and / or an operator (e.g., a customer). For purposes of this specification, a system integrator may include, but is not limited to, any number of aircraft manufacturers and major system subcontractors; a third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers; an operator may be an airline, a leasing company, a military entity, a service organization, etc.

[0079] 12 , an aircraft 1102 produced by method 1100 may include an airframe 1118 with multiple systems 1120 and an interior 1122. The airframe 1118 includes a fuselage 1119, which includes a structure 110 assembled using fastener attachment system 100 (see FIG. 1 ) and method 200 (see FIG. 2 ). Examples of systems 1120 include one or more of a propulsion system 1124, an electrical system 1126, a hydraulic system 1128, and an environmental system 1130. Any number of other systems may be included. While an aerospace-related example is shown, the principles of the invention may be applied to other industries, such as the automotive industry.

[0080] Figure 13 is a cross-sectional view of the aircraft 1102 shown schematically in Figure 12. The aircraft 1102 includes an airframe 1118 having a fuselage 1119. The portion of the fuselage 1119 shown in Figure 13 may be the fuselage section 308 of the structure 110, 310 assembled using the fastener attachment system 100, 300 and method 200, 700, 800, 900, 1000. The fuselage 1119 and fuselage section 308 include a frame 1140. The frame 1140 has fasteners 102 driven therethrough. The fasteners 102 attach the frame 1140 to an outer skin 1142 of the fuselage 1119 (and fuselage section 308). For example, holes 104 extend through frame 1140 and skin 1142, and fasteners 102 are inserted into holes 104 to secure frame 1140 to skin 1142. Fuselage 1119 also includes stringers 1144. In the embodiment shown in FIG. 13, the fuselage also includes enclosure 119.

[0081] As described above, fastener installation systems 100, 300 and methods 200, 700, 800, 900, 1000 embodied herein may be employed during any one or more of the manufacturing and service stages described in method 1100. For example, components or subassemblies corresponding to component and subassembly manufacturing 1108 may be fabricated or manufactured in a manner similar to components or subassemblies manufactured while the aircraft 1102 is in service. Also, one or more system embodiments, method embodiments, or a combination thereof may be utilized during subassembly manufacturing 1108 and system integration 1110, for example, by substantially streamlining the assembly of or reducing the cost of the aircraft 1102. Similarly, one or more system embodiments, method embodiments, or a combination thereof may be utilized while the aircraft 1102 is in service, for example, during maintenance and service 1116. For example, techniques and systems described herein may be used for material procurement 1106, component and subassembly manufacturing 1108, system integration 1110, operation 1114, and / or maintenance and service 1116, and / or may be used in the airframe 1118 and / or interior 1122. Such techniques and systems may also be utilized in systems 1120, including, for example, propulsion system 1124, electrical system 1126, hydraulic system 1128, and / or environmental system 1130.

[0082] In one embodiment, a part, e.g., structure 110, 310 (see FIGS. 1 and 3), comprises a portion of an airframe 1118 and is manufactured during component and subassembly manufacturing 1108, for example, using method 200 (see FIG. 2). The part may then be incorporated into an aircraft during system integration 1110 and subsequently utilized in service 1114 until wear renders the part unusable. The part may then be discarded and replaced with a newly manufactured part during maintenance and service 1116. Components and methods of the present invention may be utilized throughout component and subassembly manufacturing 1108 to manufacture new parts.

[0083] Any of the various control elements (e.g., electrical or electronic components) shown in the figures or described herein may be implemented as hardware, processor-implemented software, processor-implemented firmware, or some combination thereof. For example, an element may be implemented as dedicated hardware. A dedicated hardware element may be referred to as a “processor,” “controller,” or some similar terminology. When provided by a processor, functionality may be provided by a single dedicated processor, by a single shared processor, or by multiple individual processors, some of which may be shared. Furthermore, explicit use of the terms “processor” or “controller” should not be construed as referring only to hardware capable of executing software, but may implicitly include, without limitation, digital signal processor (DSP) hardware, network processors, application-specific integrated circuits (ASICs) or other circuitry, field-programmable gate arrays (FPGAs), read-only memory (ROM) for storing software, random access memory (RAM), non-volatile storage, logic, or any other physical hardware component or module.

[0084] Also, a control element may be implemented as instructions executable by a processor or computer to perform the function of the element. Some examples of instructions are software, program code, and firmware. When executed by a processor, the instructions are operable to direct the processor to perform the function of the element. The instructions may be stored in a storage device readable by the processor. Some examples of storage devices are digital or solid-state memory, magnetic storage media such as magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media.

[0085] The present disclosure also includes the following examples.

[0086] Example 1. A first example relates to a method (200) for applying a fastener (102) to a structure (110, 308, 310), the method (200) comprising: - positioning (202) a first set (340) of end effectors (140, 342, 344, 346) along fixed inner tracks (130, 330) that follow an inner mold line (IML) surface (316) of the structure (110, 310); - positioning (204) a second set (360) of end effectors (160, 362, 364, 366) along fixed outer tracks (150, 350) that follow an outer mold line (OML) surface (318) of the structure (110, 310); - aligning (206) a first end effector (140, 342) along a fixed inner track (130, 330) and a second end effector (160, 362) along a fixed outer track (150, 350); - fastening (208) the structure (110, 310) between the first end effector (140, 342) and the second end effector (160, 362) by press-fitting the first end effector (140, 342) and the second end effector (160, 362) into the structure (110, 310); and - applying (210) a fastener (102) to a structure (110, 310) Includes:

[0087] Example 2. - positioning (202) the first set (340) of end effectors (140, 342, 344, 346) includes positioning (202) the first set (340) of end effectors (140, 342, 344, 346) within a radius (R_INNER) that is smaller than the radius (R) of the structure (110, 310); - positioning (204) the second set (360) of end effectors (160, 362, 364, 366) includes positioning (204) the second set (360) of end effectors (160, 362, 364, 366) within a radius (R_OUTER) that is greater than the radius (R) of the structure (110, 310); The method (200) according to Example 1.

[0088] Example 3. - moving the first end effector (140, 342) and the second end effector (160, 362) along the curvature of the structure (110, 310) to the new fastener installation location (116); - fastening (208) the structure (110, 310) by press-fitting the first end effector (140, 342) and the second end effector (160, 362) into the structure (110, 310); and - applying (210) another fastener (102) to a structure (110, 310); The method (200) of Example 1 or 2, further comprising:

[0089] Example 4. Applying (210) the fastener (102) comprises: - drilling fastener holes (104) including countersink holes; and - inserting the fastener (102) into the fastener hole (104); The method (200) of any one of Examples 1 to 3, comprising:

[0090] Example 5. - assigning a first set (340) of end effectors (140, 342, 344, 346) to different radial zones (410, 420, 430) of the structure (110, 310); - assigning the end effectors (160, 362, 364, 366) of the second set (360) to different radial zones (410, 420, 430) of the structure (110, 310); and - exclusively operating each of the end effectors (140, 342, 344, 346) of the first set (340) and each of the end effectors (160, 362, 364, 366) of the second set (360) within different radial zones (410, 420, 430) to which each of the end effectors (140, 342, 344, 346 and 160, 362, 364, 366) is assigned. The method (200) of any one of Examples 1 to 4, further comprising:

[0091] Example 6 - positioning (202) the first set (340) of end effectors (140, 342, 344, 346) and positioning (204) the second set (360) of end effectors (160, 362, 364, 366) by: - moving the first set (340) of end effectors (140, 342, 344, 346) and the second set (360) of end effectors (160, 362, 364, 366) along a first circumferential direction (450) to apply a plurality of fasteners (102); and moving the first set (340) of end effectors (140, 342, 344, 346) and the second set (360) of end effectors (160, 362, 364, 366) along a second circumferential direction (452) opposite the first circumferential direction (450) to apply additional fasteners (102); The method (200) of Example 5, comprising:

[0092] Example 7. The method (200) of Example 5 or 6, wherein assigning the end effectors (140, 342, 344, 346) of the first set (340) and assigning the end effectors (160, 362, 364, 366) of the second set (360) includes assigning each end effector (140, 342, 344, 346) of the first set (340) and each end effector (160, 362, 364, 366) of the second set (360) to different radial zones (410, 420, 430), and at least two of the radial zones (410, 430) partially overlap another radial zone (420).

[0093] Example 8. The method (200) of any one of Examples 1 to 7, wherein applying (210) the fastener (102) to the structure (110, 308, 310) comprises driving the fastener (102) through a frame (1140) disposed on an IML surface (316) of the fuselage section (110, 308) and through the fuselage section (110, 308).

[0094] Example 9. - positioning (202) a first set (340) of end effectors (140, 342, 344, 346) along the fixed inner track (130, 330) includes positioning (202) the first set (340) along the fixed inner track (130, 330) including a first semicircle (332); - positioning (204) the second set (360) of end effectors (160, 362, 364, 366) along the fixed outer track (150, 350) includes positioning (204) the second set (360) along the fixed outer track (150, 350) including a second semicircle (352) larger than and concentric with the first semicircle (332); The method (200) of any one of Examples 1 to 8.

[0095] Example 10. - positioning (202) a first set (340) of end effectors (140, 342, 344, 346) along the fixed inner track (130, 330) includes positioning (202) the first set (340) to follow the curved IML surface (316); - positioning (204) a second set (360) of end effectors (160, 362, 364, 366) along the fixed outer track (150, 350) includes positioning (204) the second set (360) to follow the curved OML surface (318); The method (200) of any one of Examples 1 to 9.

[0096] Example 11. A non-transitory computer-readable medium embodying programmed instructions, the instructions, when executed by a processor, are operable to perform a method (200) according to any one of Examples 1 to 10 for applying a fastener (102) to a structure (110, 308, 310).

[0097] Example 12. A portion of an aircraft (1102) assembled according to the method (200) of any one of Examples 1 to 10 and / or the method (200) defined by instructions stored on a computer-readable medium of Example 11.

[0098] Example 13. A system (100, 300) for applying a fastener (102) to a structure (110, 310), comprising: - fixed inner tracks (130, 330) along the inner mould line (IML) side (108); - an IML end effector (140, 342) disposed along a fixed inner track (130, 330) facing the IML surface (316) of the structure (110, 310), the IML end effector (140, 342) being able to follow the IML surface (316) of the structure (110, 310) due to the shape of the fixed inner track (130, 330); - fixed outer tracks (150, 350) along the outer mold line (OML) side (106); and - an OML end effector (160, 362) disposed along a fixed outer track (150, 350) facing the OML surface (318) of the structure (110, 310), the OML end effector (160, 362) being able to follow the OML surface (318) of the structure (110, 310) due to the shape of the fixed outer track (150, 350); wherein the IML end effector (140, 342) is configured to operate in conjunction with the OML end effector (160, 362) to fasten the structure (110, 310) and install the fastener (102).

[0099] Example 14. - the IML end effector (140, 342) is mounted on a fixed inner track (130, 330), the fixed inner track (130, 330) having a radius (R_INNER) that is smaller than the radius (R) of the structure (110, 310); - the OML end effector (160, 362) is mounted on a fixed outer track (150, 350), the fixed outer track (150, 350) having a radius (R_OUTER) greater than the radius (R) of the structure (110, 310); The system (100, 300) of Example 13.

[0100] Example 15. The system (100, 300) of Example 13 or 14, further comprising a controller (174) that operates at least one pair (155) including an IML end effector (140, 342) and an OML end effector (160, 362), wherein the controller (174) operates each pair (155) exclusively within a different radial zone (410, 420, 430) to install a fastener (102) therein.

[0101] Example 16. a controller (174) commands the IML end effectors (140, 342) and the OML end effectors (160, 362) to move along a first circumferential direction (450) to apply a plurality of fasteners (102); the controller (173) commands the IML end effectors (140, 342) and the OML end effectors (160, 362) to move along a second circumferential direction (452) opposite the first circumferential direction (450) to apply additional fasteners (102); The system (100, 300) of Example 15.

[0102] Example 17. The system (100, 300) of Examples 15 or 16, wherein each radial zone (410, 430) overlaps another radial zone (420).

[0103] Example 18. The system (100, 300) of any one of Examples 13 to 17, wherein the fixed inner track (130, 300) includes a first semicircle (332) and the fixed outer track (150, 350) includes a second semicircle (352) that is larger than and concentric with the first semicircle (332).

[0104] Example 19. The system (100, 300) of any one of Examples 13 to 18, wherein the IML surface (316) is curved and the OML surface (318) is curved.

[0105] Example 20. Manufacturing a portion of an aircraft (1102) using the system (100, 300) of any one of Examples 13 to 19.

[0106] The present disclosure also includes the following examples, which should not be confused with the claims that determine the scope of protection.

[0107] Example 1A. A method (700, 800, 900, 1000) for applying a fastener (102) to a structure (110, 310), comprising: - pulsating (702, 802, 902, 1002) a structure (110, 310) including a fastener installation location (116) toward a fastener installation system (100, 300); and - installing (704, 806, 904, 1004) at least one fastener (102) at a fastener installation location (116) via an end effector (140, 160) supported by a track (130, 150) independent of the structure (110, 310); Methods including (700, 800, 900, 1000).

[0108] Example 2A. The method (700, 800, 900, 1000) of Example 1A, wherein the pulsing (702, 802, 902, 1002) comprises moving the structure (110, 310) along a rail (120) that comprises a portion of the pulsed production line (10).

[0109] Example 3A. The method (800) of Example 1A or 2A, including fastening (804) structures (110, 310) between end effectors (140, 160) supported by tracks (130, 150).

[0110] Example 4A. The method (800) of Example 3A, further comprising transmitting the force applied during fastening (804) and installing (806) the fastener through the end effector (140, 160) and into the track (130, 150).

[0111] Example 5A. The method (700, 800, 900, 1000) of any one of Examples 1A to 4A, wherein attaching (704, 806, 904, 908, 1004) includes attaching the fastener (102) along the curved section (122) of the structure (110, 310).

[0112] Example 6A. The method (700, 800, 900, 1000) of any one of Examples 1A to 5A, wherein attaching (704, 806, 904, 908, 1004) includes attaching the fastener (102) along the longitudinal portion (124) of the structure (110, 310).

[0113] Example 7A. The method (1000) of any one of Examples 1A to 6A, wherein attaching (1004, 1008) secures the enclosure (119) to the structure (110, 310) such that the enclosure (119) covers the cutout portion of the structure (110, 310).

[0114] Example 8A. The method (700, 800, 900) of any one of Examples 1A to 7A, wherein the attaching (704, 806, 904, 908) secures the frame (1140) to the structure (110, 310).

[0115] Example 9A. The method (700, 800, 900, 1000) of any one of Examples 1A to 8A, further comprising aligning (206) an outer mold line (OML) end effector (160) and an inner mold line (IML) end effector (140) with the structure (110, 310), wherein the attaching (704, 806, 904, 1004) is performed via the OML end effector (160) and the IML end effector (140).

[0116] Embodiment 10A. The method (700, 800, 900, 1000) of any one of embodiments 1A to 9A, wherein attaching (704, 806, 904, 908, 1004) places an interference fit fastener at the fastener attachment location (116).

[0117] Example 11A. The method (800) of any one of Examples 3A to 10A, wherein fastening (804) includes fastening (804) the structure (110, 310) between an IML end effector (140) and an OML end effector (160) of the fastener installation system (100, 300); and attaching (806) includes attaching (806) the fastener (102) to the structure (110, 310) via the IML end effector (140) and the OML end effector (160).

[0118] Example 12A. The method (800) of any one of Examples 1A to 11A, wherein attaching (802) includes attaching fasteners (102) along the hoop body (126) of the structure (110, 310).

[0119] Example 13A. The method (800, 900) of any one of Examples 1A to 12A, wherein attaching (806, 904, 908) includes attaching fasteners (102) along the length (L) of the structure (110, 310).

[0120] Example 14A. The method (800, 900) of any one of Examples 1A to 13A, wherein pulsing (802, 902, 1002, 1006) the structure (110, 310) includes moving the structure (110, 310) a distance less than the length (L) of the structure (110, 310) before pausing the movement of the structure (110, 310).

[0121] Example 15A. - fastening (804) the structure (110) between a fixed inner track (130) that tracks the IML surface (316) of the structure (110, 310) and a fixed outer track (150) that tracks the OML surface (318) of the structure (110, 310) in the fastener attachment system (100, 300); Further comprising: - attaching (806) includes attaching (806) the fastener (102) to the structure (110) via end effectors (140, 160) disposed in the fixed inner track (130) and the fixed outer track (150); The method (800) of any one of Examples 1A to 10A.

[0122] Example 16A. The attaching (904) includes attaching (904) at least one fastener (102) to the fastener attachment location (116) via end effectors (140, 160) disposed on the OML surface (318) and the IML surface (316) of the structure (110, 310); - moving (906) the end effector (140, 160) in a longitudinal direction (380) relative to the structure (110, 310); and - After the end effectors (140, 160) have moved (906), installing (908) additional fasteners (102) through the end effectors (140, 160). The method (900) of any one of Examples 1A to 15A, further comprising:

[0123] Example 17A. The method (900) of any one of Examples 1A to 16A, wherein pulsing (902) the structure (110, 310) includes moving the fastener installation location (116) from a previous workstation of the pulsed production line (10) to the fastener installation system (100, 300).

[0124] Example 18A. The attaching (1004) includes attaching (1004) a first subset of fasteners (102) for the enclosure (119) disposed via end effectors (140, 160) supported by tracks (130, 150) independent of the structure (110, 310); - further pulsing (1006) the structure (110, 310) through the fastener attachment system (100, 300); and - installing (1008) a second subset of fasteners (102) for the enclosure (119) via the end effectors (140, 160); The method (1000) of any one of Examples 1A to 17A, further comprising:

[0125] Example 19A. The method (1000) of any one of Examples 1A to 18A, wherein the attaching (1004, 1008) is performed by a pair (155) of end effectors (140, 160) working in conjunction.

[0126] Example 20A. The method (1000) of any one of Examples 1A to 19A, wherein the attaching (1004, 1008) is performed by at least one pair (155) of end effectors (140, 160) operating at a forward portion of the enclosure (119) and by at least one other pair (155) of end effectors (140, 160) operating at a rearward portion of the enclosure (119), the pairs (155) operating simultaneously at the forward and rearward portions.

[0127] Example 21A. The method (1000) of any one of Examples 1A to 20A, wherein the attaching (1004, 1008) is performed by an IML end effector (140) and an OML end effector (160).

[0128] Example 22A. The method (1000) of any one of Examples 1A to 21A, further comprising indexing the structures (110, 310) after pulsing (1002, 1006) the structures (110, 310).

[0129] Example 23A. The method (1000) of any one of Examples 1A to 22A, wherein fasteners (102) are attached (1004, 1008) along the perimeter of enclosure (119).

[0130] Example 24A. The method (1000) of any one of Examples 1A to 23A, wherein fastener attachment (1004, 1008) for the enclosure (119) is distributed among different end effectors (140, 160).

[0131] Example 25A. The method (1000) of any one of Examples 1A to 24A, wherein the installing (1004, 1008) of the first and second subsets of fasteners (102) installs interference fit fasteners.

[0132] Example 26A. A portion of an aircraft (1102) assembled according to the method (700, 800, 900, 1000) of any one of Examples 1A to 25A.

[0133] Although specific embodiments are described herein, the scope of the disclosure is not limited to those specific embodiments, but is instead defined by the claims.

Claims

1. A method (200) for applying a fastener (102) to a structure (110, 308, 310) comprising: - positioning (202) a first set (340) of end effectors (140, 342, 344, 346) along a fixed inner track (130, 330) that follows an inner mold line (IML) surface (316) of the structure (110, 310) and includes a first semicircle (332) by longitudinal movement of the structure (110, 310); - positioning (204) a second set (360) of end effectors (160, 362, 364, 366) along a fixed outer track (150, 350) that follows an outer mold line (OML) surface (318) of the structure (110, 310) and includes a second semicircle (352) that is larger than and concentric with the first semicircle (332) due to the longitudinal movement of the structure (110, 310); - aligning (206) a first end effector (140, 342) along said fixed inner track (130, 330) and a second end effector (160, 362) along said fixed outer track (150, 350) by moving them in said longitudinal direction; fastening (208) the structure (110, 310) between the first end effector (140, 342) and the second end effector (160, 362) by press-fitting the first end effector (140, 342) and the second end effector (160, 362) into the structure (110, 310); and - applying (210) a fastener (102) to said structure (110, 310); A method (200) comprising:

2. applying (210) the fastener (102) to the structure (110, 310) includes installing the fastener (102); and / or the first set of end effectors (140) and the second set of end effectors (160) comprise four-axis or five-axis machines including automated tools for fastener installation, such as drills, clamps, suction elements, and / or crimping tools, and / or the end effectors (140, 160) can be extended, retracted, or otherwise repositioned to address separation between their respective tracks (130, 150) and the IML surface (316) or the OML surface (318) of the structure (110); The method (200) of claim 1.

3. - positioning (202) the first set (340) of end effectors (140, 342, 344, 346) includes positioning (202) the first set (340) of end effectors (140, 342, 344, 346) within a radius (R_INNER) that is smaller than the radius (R) of the structure (110, 310); positioning (204) the second set (360) of end effectors (160, 362, 364, 366) includes positioning (204) the second set (360) of end effectors (160, 362, 364, 366) within a radius (R_OUTER) greater than the radius (R) of the structure (110, 310); 3. The method according to claim 1 or 2.

4. - moving the first end effector (140, 342) and the second end effector (160, 362) along the curvature of the structure (110, 310) to a new fastener installation location (116); - fastening (208) the structure (110, 310) by press-fitting the first end effector (140, 342) and the second end effector (160, 362) into the structure (110, 310); and - applying (210) another fastener (102) to said structure (110, 310); and / or Applying (210) the fastener (102) comprises: - Drilling fastener holes (104), including countersink holes; and - inserting a fastener (102) into said fastener hole (104); The method (200) of any one of claims 1 to 3, comprising:

5. - allocating the end effectors (140, 342, 344, 346) of said first set (340) to different radial zones (410, 420, 430) of said structure (110, 310); assigning the second set (360) of end effectors (160, 362, 364, 366) to the different radial zones (410, 420, 430) of the structure (110, 310); and - operating each end effector (140, 342, 344, 346) of the first set (340) and each end effector (160, 362, 364, 366) of the second set (360) exclusively within the different radial zones (410, 420, 430) to which each end effector (140, 342, 344, 346 and 160, 362, 364, 366) is assigned; and optionally further comprising: positioning (202) the first set (340) of end effectors (140, 342, 344, 346) and positioning (204) the second set (360) of end effectors (160, 362, 364, 366) by: moving the first set (340) of end effectors (140, 342, 344, 346) and the second set (360) of end effectors (160, 362, 364, 366) along a first circumferential direction (450) to apply a plurality of fasteners (102); and moving the first set (340) of end effectors (140, 342, 344, 346) and the second set (360) of end effectors (160, 362, 364, 366) along a second circumferential direction (452) opposite the first circumferential direction (450) to apply additional fasteners (102); The method (200) of any one of claims 1 to 4, comprising:

6. - allocating the end effectors (140, 342, 344, 346) of the first set (340) and allocating the end effectors (160, 362, 364, 366) of the second set (360) comprises allocating each end effector (140, 342, 344, 346) of the first set (340) and each end effector (160, 362, 364, 366) of the second set (360) to different radial zones (410, 420, 430), at least two of the radial zones (410, 430) overlapping another radial zone (420); The method (200) of claim 5.

7. applying (210) the fasteners (102) to the structure (110, 308, 310) comprises driving the fasteners (102) through a frame (1140) arranged on an IML surface (316) of a fuselage section (110, 308) and through the fuselage section (110, 308); and / or - positioning (202) a first set (340) of the end effectors (140, 342, 344, 346) along the fixed inner track (130, 330) includes positioning (202) the first set (340) to follow the curved IML surface (316); - positioning (204) a second set (360) of the end effectors (160, 362, 364, 366) along the fixed outer track (150, 350) comprises positioning (204) the second set (360) to follow the curved OML surface (318); The method (200) of any one of claims 1 to 6.

8. the radii of the fixed inner track (130) and the fixed outer track (150) are varied, and the associated end effectors (140, 160) are configured to move dynamically to accommodate the changing distances from the tracks (130, 150) to the structure (110) as the operation progresses; and / or advancing the structure (310) within the gap G between the fixed inner track (330) and the fixed outer track (350) such that during an assembly operation, the structure (310, 110) is able to move without obstruction through the gap G between the IML end effector (140) and the OML end effector (160); The method (200) of any one of claims 1 to 7.

9. 9. The method (200) of any one of claims 1 to 8, wherein the IML end effector (140, 342) is configured to operate in coordination with the OML end effector (160, 362) to tighten the structure (110, 310) and install the fastener (102).

10. 10. A non-transitory computer-readable medium embodying programmed instructions that, when executed by a processor, are operable to perform the method (200) of any one of claims 1 to 9 for applying a fastener (102) to a structure (110, 308, 310).

11. 11. A portion of an aircraft (1102) assembled according to the method (200) of any one of claims 1 to 9 and / or the method (200) defined by instructions stored on a computer-readable medium of claim 10.

12. A system (100, 300) for applying a fastener (102) to a structure (110, 310), comprising: a fixed inner track (130, 330) along the inner mould line (IML) side (108) including a first semicircle (332); an IML end effector (140, 342) arranged along the fixed inner track (130, 330) and configured to oppose the IML surface (316) of the structure (110, 310) by longitudinal movement of the structure (110, 310), the shape of the fixed inner track (130, 330) enabling the IML end effector (140, 342) to follow the IML surface (316) of the structure (110, 310); a fixed outer track (150, 350) along the outer mould line (OML) side (106), said fixed outer track (150, 350) including a second semicircle (352) larger than and concentric with said first semicircle (332); and an OML end effector (160, 362) arranged along the fixed outer track (150, 350) and configured to oppose the OML surface (318) of the structure (110, 310) by said movement in the longitudinal direction of the structure (110, 310), the OML end effector (160, 362) being able to follow the OML surface (318) of the structure (110, 310) due to the shape of the fixed outer track (150, 350); It is equipped with The system (100, 300) is configured to operate in coordination with the OML end effector (160, 362) by moving the IML end effector (140, 342) and the OML end effector (160, 362) in the longitudinal direction to tighten the structure (110, 310) and install the fastener (102).

13. - said IML end effector (140, 342) is mounted on said fixed inner track (130, 330), said fixed inner track (130, 330) having a radius (R_INNER) smaller than the radius (R) of said structure (110, 310); - said OML end effector (160, 362) is mounted on said fixed outer track (150, 350), said fixed outer track (150, 350) having a radius (R_OUTER) greater than the radius (R) of said structure (110, 310); The system (100, 300) of claim 12.

14. a controller (174) for operating at least one pair (155) comprising said IML end effector (140, 342) and said OML end effector (160, 362); wherein the controller (174) exclusively operates each pair (155) within a different radial zone (410, 420, 430) for installing the fastener (102) therein; and / or the controller (174) commands the IML end effector (140, 342) and the OML end effector (160, 362) to move along a first circumferential direction (450) to apply a plurality of fasteners (102); the controller (173) commands the IML end effectors (140, 342) and the OML end effectors (160, 362) to move along a second circumferential direction (452) opposite the first circumferential direction (450) to apply additional fasteners (102); and / or said radial zones (410, 430) each partially overlap another radial zone (420), and / or: - the IML surface (316) is curved and the OML surface (318) is curved; A system (100, 300) according to claim 12 or 13.

15. Manufacture of a portion of an aircraft (1102) using a system (100, 300) according to any one of claims 12 to 14.

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