Patent Description:
Structures, such as portions of the airframe of an aircraft, may be assembled via the application of fasteners such as lockbolts, pins secured by nuts, rivets, etc. However, fasteners may be particularly difficult to install onto structures that include contours, as alignment of the fasteners with the structure may be more complex. The installation of fasteners onto such structures is therefore either labor intensive, or it necessitates the use of complex robots.

The abstract of <CIT> states: "Riveting process and installation for the construction of aerofoils (e.g., wings and stabilisers for aeroplanes), the installation comprising a riveting head, which is attached in a positionable manner on a carrying bridge; an anvil which is in a position of relative opposition to the aforementioned head; and a series of transverse carriages being mounted for longitudinal displacement, with passage under the bridge, with the carriages including positionable elements intended to support the components of the aerofoil to be riveted. The entire functional assembly is related to a computer control, for the development of a process of automatic riveting.

The abstract of <CIT> states: "A machine comprising a horizontally elongated base having pairs of pylons slidably mounted on opposite sides of the base for horizontal movement along the length thereof, forming in effect, a moveable C-frame. The workpiece is fixedly supported on the base in a substantially vertical position, and the pylons of each pair work together on opposite sides of the workpiece to process rivets/fasteners or perform other functions. Each of the pylons comprises a vertical first component and a horizontal second component. The second component is movable vertically on the first component, and is also movable horizontally toward and away from the workpiece. Carried on the end of each of the horizontal second components adjacent the workpiece is a tool assembly holder that is rotatable about horizontal and vertical axes. Each tool assembly holder is adapted to detachably receive a tool assembly, and each tool assembly consists of tools for successively performing various functions, the tools on one side of the workpiece being axially aligned with an companionate to the tools on the other side, so that simultaneous operation of the opposed tools performs the desired function.

The abstract of <CIT> states: "PROBLEM: To highly precisely perform the positioning between an opening for hole and an area to be riveted by comparing the position of the area to be riveted whose image is picked up by a camera with the position of a riveting means, thereby detecting the movement of the riveting means. SOLUTION: A position detecting means converts the data picked up by a camera into a two-dimensional binary data, and detects the position of the center of the area of a figure formed by the binary data as the position of an area to be riveted. The position of the detected area to be riveted is compared with the position of at least one of a first moving body and a second moving body. The movement of at least one of the first moving body and the second moving body is detected to position drilling means or riveting means provided on the first moving body and the second moving body to the area to be riveted detected by the result of comparison, and either of the riveting means and a work are moved.

The abstract of <CIT> states: " An apparatus may comprise a rail system, a multi-axis carriage, a tool module, and a controller. The rail system may be capable of being attached to a surface on a structure. The multi-axis carriage may be coupled to the rail system. The multi-axis carriage may be capable of moving along the rail system and moving a riveting tool in axes relative to the surface. The tool module may be capable of being removably coupled to the multi-axis carriage. The tool module may comprise a frame and may be capable of receiving the riveting tool. The controller may be capable of controlling movement of the riveting tool to a number of locations on the surface of the structure and may be capable of causing the riveting tool to install a number of rivets in the number of preselected locations in response to a signal.

Therefore, it would be desirable to have a method and system that take into account at least some of the issues discussed above, as well as other possible issues.

The general principle of the claimed invention is to provide end effectors that are arranged on fixed tracks following an Inner Mold Line (IML) and an Outer Mold Line (OML) of a structure that will receive fasteners, wherein the fixed tracks are not attached to the structure itself. Because the fixed tracks correspond with the contours of the structure, the end effectors are held in an enforced alignment with the structure when installing fasteners. This relationship remains true even as the end effectors are moved along the fixed tracks to install fasteners at different radial locations along the structure. The arrangement described above also allows the structure to be moved relative to the end effectors by any desired amount, such that fasteners may be installed at various positions along the length of the structure.

A first aspect of the claimed invention is a method for applying fasteners to a structure as defined in claim <NUM>. The method includes disposing a first set of end effectors along a fixed inner track that follows an Inner Mold Line (IML) surface of a structure, disposing a second set of end effectors along a fixed outer track that follows an Outer Mold Line (OML) surface 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.

A further aspect of the claimed invention is a non-transitory computer readable medium as defined in claim <NUM>. The non-transitory computer readable medium embodies programmed instructions which, when executed by a processor, are operable for performing a method accoding to any one of the claims <NUM> to <NUM> for applying fasteners to a structure using a system according to any one of the claims <NUM> to <NUM>.

Another aspect of the claimed invention is a system for applying fasteners to a structure as defined in claim <NUM>. The system includes a fixed inner track along an Inner Mold Line (IML) side, an IML end effector disposed along the fixed inner track to face an IML surface of the structure. The fixed inner track is shaped to enable the IML end effector to follow the IML surface of a 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 to face an OML surface of the structure. The fixed outer track is shaped to enable an end effector to follow the OML surface of the structure. The end effectors of the first set are configured to operate in tandem with the end effectors of the second set to clamp the structure and install the fasteners.

It is noted that in this application an end effector is an extension and/or platform and/or multi-axis machine to which automated tools can be installed. An end effector may for example comprise four- or five-axis machines that include automated tools for fastener installation (e.g., drills, clamps, suction elements, swage tools, etc.) or to which such tools are connectable.

Other illustrative embodiments (e.g., methods and computer-readable media relating to the foregoing embodiments) may be described below. The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings.

The figures and the following description provide specific illustrative embodiments of the claimed invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the claimed invention and are included within the scope of the appended claims. Furthermore, any examples described herein are intended to aid in understanding the principles of the claimed invention, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the scope of the claimed invention is not limited to the specific embodiments or examples described below, but by the claims.

<FIG> is a schematic block diagram of a fastener installation system <NUM> in an illustrative embodiment. Fastener installation system <NUM> may have one or more work stations in a series of work stations along a pulsed manufacturing line <NUM> where a component and/or assembly of components is moved through the series of work stations via pulsed movements. The fastener installation system <NUM> may be a particular pulsed line system along the pulsed manufacturing line <NUM>, which can include a series of fabrication and/or assembly systems through which the component and/or assembly passes to manufacture a final assembly. A particular example of the fastener installation system <NUM> is a fastener installation system <NUM> (shown in <FIG>). The fastener installation system <NUM> includes at least one installation station. The installation station <NUM> includes a fixed inner track <NUM>, a fixed outer track <NUM>, IML end effectors associated with the fixed inner track <NUM>, and OML end effectors associated with the fixed outer track <NUM>. When the fastener installation system <NUM> includes more than one installation station, a pair <NUM> of end effectors <NUM>, <NUM> at a first installation station can operate simultaneously with another pair <NUM> of end effectors <NUM>, <NUM> in a second installation station. For example, when a surround <NUM> is being secured to the structure <NUM>, at least one pair of end effectors <NUM>, <NUM> operates on a fore portion of the surround <NUM> to install fasteners <NUM>, and at least one other pair of end effectors <NUM>, <NUM> operates on an aft portion of the surround <NUM>, wherein the pairs operate simultaneously on the fore portion and the aft portion.

Fastener installation system <NUM> (also known as a "fastener installation station" of the pulsed manufacturing line <NUM>) comprises any system, device, or component operable to utilize a mobile Inner Mold Line (IML) end effector and a mobile Outer Mold Line (OML) end effector to perform installation of fasteners <NUM> at a structure <NUM>. More specifically, the IML end effector is configured to perform fastener installation at an inner mold line surface, such as IML surface <NUM> (shown in <FIG>), of the structure <NUM>. Similarly, the OML end effector is configured to perform fastener installation at an outer mold line surface, such as OML surface <NUM> (shown in <FIG>), of the structure <NUM>. Examples of the IML end effector are end effectors <NUM>, <NUM>, <NUM> shown in <FIG>, and example of the OML end effector are end effectors <NUM>, <NUM>, <NUM> shown in <FIG>. The fastener <NUM> can be any suitable type of fastener, such as a lockbolt, nut, rivet, and/or an interference-fit fastener.

Fastener installation system <NUM> has been enhanced to provide end effectors <NUM>, <NUM> at inner and outer fixed tracks that a structure <NUM> passes between. An example of the fixed inner track <NUM> is the fixed inner track <NUM> shown in <FIG>, and an example of the fixed outer track is a fixed outer track <NUM> shown in <FIG>. The end effectors <NUM>, <NUM> operate in a coordinated fashion to install fasteners <NUM> in holes <NUM> during pauses between pulsed movements of the structure <NUM> with respect to the fixed tracks. A pulsed movement comprises a motion of the structure <NUM> that proceeds for less than a length L of the structure <NUM>. Each pulse may move a fastener installation location <NUM> from a prior work station to a next work station in the fastener installation system <NUM>. During each pause, fasteners <NUM> are installed within an installation orbit of the IML end effectors and the OML end effectors, which are mounted on fixed tracks.

In this embodiment, a structure <NUM> comprises a half-barrel section of a fuselage (i.e., a fuselage portion <NUM> (shown in <FIG>) of a fuselage having an open, semicircular cross-section) that is moved along a rail <NUM> or similar structure between fixed inner track <NUM> and fixed outer track <NUM>. The structure <NUM> includes a curved section <NUM>. The curved section <NUM> has the radius R; however, the radius of the curved section <NUM> need not be constant along the entire IML surface <NUM> of the structure <NUM>. The structure <NUM> also includes a longitudinal portion <NUM> that is a region of the structure extending generally along a longitudinal axis A of the structure <NUM>. The longitudinal portion <NUM> receives fasteners <NUM> as described in more detail below.

The rail <NUM> is part of the pulsed manufacturing line <NUM> and helps the structure <NUM> to be transported for fabrication via pulsed-line assembly techniques. Between pulsed motions of structure <NUM> along the fixed tracks, the structure <NUM> may be indexed, and fasteners <NUM> may be installed by coordinated actions of an OML end effector that travels along fixed outer track <NUM>, and an IML end effector that travels along the fixed inner track <NUM>.

As shown in <FIG>, numerous ones of IML end effectors and OML end effectors are disposed along different radial portions of their respective fixed tracks <NUM>, <NUM> as first set <NUM> and second set <NUM> of end effectors. Each OML end effector coordinates and works in a paired relationship with a corresponding one of IML end effectors. The controller <NUM> operates at least one pair of an IML end effector and an OML end effector. Any number of paired end effectors <NUM>, <NUM> can be utilized to perform this work, and each pair <NUM> of end effectors <NUM>, <NUM> may perform work within a pre-partitioned portion of a half-circle. Example of paired end effectors are shown in <FIG> as pairs <NUM>, <NUM>, <NUM> each having an IML end effector <NUM>, <NUM>, <NUM> and an OML end effector <NUM>, <NUM>, <NUM>. The size of the pre-partitioned portion depends on the number of sets of paired end effectors. Each pair of end effectors have a pair of discrete tracks. Thus, an IML end effector and an OML end effector in each of the paired sets of end effectors work on different tracks <NUM>, <NUM> from each other as they perform work over an arc.

Structure <NUM> is held in its current cross-sectional shape by braces <NUM>, although other embodiments may not have these braces <NUM> and may maintain the shape of the structure <NUM> through other means. An example of the braces <NUM> is shown in <FIG> as braces <NUM>. In further embodiments, structure <NUM> includes a section <NUM> of manufacturing excess/sacrificial material that may be used to facilitate indexing and/or transport of structure <NUM> during assembly operations. Structure <NUM> also includes locations (e.g., fastener installation locations) along its length L, at which it is desired to install one or more fasteners <NUM>. The fasteners <NUM> are installed in a hoop-wise portion <NUM>. For example, a hoop-wise portion <NUM> can be defined at each fastener installation location <NUM> and extend at least partially across the curved section <NUM>. In some embodiments, structure <NUM> also includes a cut-out (not shown, but made by a later-visited work station) in or to which a surround <NUM> may be placed. The surround <NUM> can be secured to the structure <NUM> at the fore portion, the aft portion, and/or the perimeter of the surround <NUM>. This may depend upon the work station and/or pulsed line system. For example, some work stations may install frames, such as frames <NUM> (shown in <FIG>), to a structure <NUM> comprising a skin, such as skin <NUM> (shown in <FIG>), while other work stations may install surrounds <NUM> around locations where openings within a structure <NUM> will be installed.

Structure <NUM> has a radius R. The radius of fixed inner track <NUM> (including IML end effector <NUM>) (R_INNER) is less than R. Furthermore, the radius of fixed outer track <NUM> (including OML end effector <NUM>) (R_OUTER) is greater than R. However, the fixed inner track <NUM> and the fixed outer track <NUM> do not have to have a fixed radius along their entire lengths, so long as there is a gap G for structure <NUM> to pass through. This is because the end effectors <NUM>, <NUM> can compensate for any distance variation between a particular track location and the IML surface (e.g., IML surface <NUM> in <FIG>) or OML surface (e.g., OML surface <NUM> in <FIG>) of the structure <NUM>. This means that structure <NUM> may move without obstruction through the gap G between IML end effector <NUM> and OML end effector <NUM>. Thus, the fixed outer track <NUM> is disposed at an OML side <NUM> of the system <NUM> and/or the structure <NUM> and is shaped to enable an OML end effector <NUM> to follow the OML surface of a structure <NUM>. Similarly, the fixed inner track <NUM> is disposed along an IML side <NUM> of the fastener installation system <NUM> and/or structure <NUM> and is shaped to enable an IML end effector <NUM> to follow the IML surface of the structure <NUM>.

IML end effector <NUM> and OML end effector <NUM> may comprise, for example, four- or five-axis machines that include automated tools for fastener installation (e.g., drills, clamps, suction elements, swage tools, etc.). In further embodiments, the end effectors <NUM>, <NUM> discussed herein are capable of extending, retracting, or otherwise repositioning in order to account for separation between their tracks <NUM>, <NUM> and the IML surface (e.g., IML surface <NUM> shown in <FIG>) or OML surface (e.g., OML surface <NUM> shown in <FIG>) of the structure <NUM>. The end effectors <NUM>, <NUM> may be capable of performing this action regardless of whether the amount of separation varies along the tracks <NUM>, <NUM>.

In further embodiments, the radii of the fixed inner track <NUM> and the fixed outer track <NUM> vary, and associated end effectors <NUM>, <NUM> dynamically move to account for varying distances from the tracks <NUM>, <NUM> to the structure <NUM> as work progresses. In still further embodiments, to help avoid end effector collisions, fixed tracks of differing radii occupy different sides of the structure <NUM>. For example, a fixed outer track <NUM> on the right may exhibit a <NUM> (ten foot) radius, while a fixed outer track <NUM> on the left may exhibit a <NUM> (an eleven foot) radius and a fixed outer track <NUM> on the center may exhibit a <NUM>(ten and a half foot) radius.

The operations of IML end effector <NUM> and OML end effector <NUM> are coordinated via server <NUM>. In one embodiment, controller <NUM> of server <NUM> accesses instructions in a Numerical Control (NC) program stored in memory <NUM> to direct the actions of the end effectors <NUM>, <NUM>, and transmits the instructions via an interface (i.e., I/F <NUM>). Controller <NUM> may be implemented, for example, as custom circuitry, as a hardware processor executing programmed instructions, or some combination thereof.

Illustrative details of the operation of fastener installation system <NUM> will be discussed with regard to <FIG>. In one embodiment, structure <NUM> has completed inspection via Non-Destructive Imaging (NDI) techniques, and is ready to be passed between a fixed inner track <NUM> and a fixed outer track <NUM> in order for fastener installation to commence. Furthermore, in this embodiment, fixed inner track <NUM> is complementary (e.g., matches) the contour of an inner surface (e.g., IML) of the structure <NUM>, and fixed outer track <NUM> is complementary to the contour of an outer surface (e.g., OML) of the structure <NUM>.

<FIG> is a flowchart illustrating a method <NUM> for operating a fastener installation system in an illustrative embodiment. The steps of method <NUM> are described with reference to fastener installation system <NUM> of <FIG>, but those skilled in the art will appreciate that method <NUM> may be performed in other systems. The steps of the flowcharts described herein are not all inclusive and may include other steps not shown. The steps described herein may also be performed in an alternative order.

Referring to <FIG> and <FIG>, in step <NUM>, a first set (e.g., first set <NUM> shown in <FIG>) of IML end effectors are disposed along the fixed inner track <NUM>. The fixed inner track <NUM> facilitates operation of the IML end effectors to follow a curved IML of the structure <NUM>. For example, the IML end effectors move without touching the IML surface (e.g., IML surface <NUM> shown in <FIG>) of the structure <NUM>, but remain close enough to contact the IML surface of the structure <NUM> at selected positions along the IML surface of the structure <NUM> to install fasteners <NUM>. The first set of IML end effectors may comprise end effectors <NUM> that each occupy a different radial portion of the fixed inner track <NUM> (and hence each follow a different arc that is complementary to the curved IML of the structure <NUM>). An example of this is shown in <FIG>. Any number N of IML end effectors may be arranged for pairing with the OML end effectors discussed below with regard to step <NUM>. Disposing <NUM> the IML end effectors along the fixed inner track <NUM> may comprise mounting the IML end effectors at the fixed inner track <NUM> such that the IML end effectors are capable of adjusting their position along the structure <NUM> (e.g., by traveling along the track <NUM>).

In step <NUM>, a second set (e.g., second set <NUM> shown in <FIG>) of the OML end effectors are disposed along fixed outer track <NUM>. The fixed outer track <NUM> facilitates operation of the OML end effectors to follow a curved OML of the structure <NUM>. For example, the OML end effectors move without touching the OML surface (e.g., OML surface <NUM> shown in <FIG>) of the structure <NUM>, but remain close enough to contact the OML surface of the structure <NUM> at selected positions along the OML surface of the structure <NUM> to install fasteners <NUM>. The second set of OML end effectors may comprise end effectors that each occupy a different radial position along fixed outer track <NUM>, as shown in <FIG>. Disposing the OML end effectors along fixed outer track <NUM> may comprise mounting the OML end effectors at the fixed outer track <NUM> such that the end effectors are capable of adjusting their position along the structure <NUM> (e.g., by traveling along the fixed outer track <NUM>).

An aspect of disposing <NUM> the first set <NUM> and disposing <NUM> the second set <NUM> includes assigning the end effectors <NUM>, <NUM>. More specifically, and referring to <FIG>, <FIG>, and <FIG>, the method <NUM> can further include assigning end effectors <NUM>, <NUM>, <NUM>, <NUM> in the first set <NUM> to different radial zones <NUM>, <NUM>, <NUM> at the structure <NUM>, <NUM> and assigning end effectors <NUM>, <NUM>, <NUM>, <NUM> in the second set <NUM> to the different radial zones <NUM>, <NUM>, <NUM> at the structure <NUM>, <NUM>. Each end effector <NUM>, <NUM>, <NUM>, <NUM> in the first set <NUM> and each end effector <NUM>, <NUM>, <NUM>, <NUM> in the second set <NUM> is operated exclusively within the radial zones <NUM>, <NUM>, <NUM> that the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> have been assigned to.

In step <NUM>, a first end effector along the fixed inner track (e.g., an IML end effector <NUM> along a fixed inner track <NUM>) is aligned with a second end effector along the fixed outer track (e.g., an OML end effector <NUM> along a fixed outer track <NUM>). The alignment may comprise placing both the first end effector and the second end effector at the same location/position along the curvature of the structure <NUM>. A structural component desired to be affixed to the structure <NUM> may also be aligned with the end effectors <NUM>, <NUM>. For example, in embodiments where the structure <NUM> is a fuselage portion <NUM> of a fuselage (e.g., fuselage <NUM> shown in <FIG> and <FIG>), a curved frame, such as the frame <NUM> (shown in <FIG>), for the fuselage may be aligned with the end effectors <NUM>, <NUM> so that installation of a fastener <NUM> secures the frame <NUM> to a skin (e.g., the skin <NUM> shown in <FIG>) of the fuselage <NUM>. The frame <NUM> itself may be indexed using notches or holders disposed at the fixed inner track <NUM>, if desired. In this manner, the position of the fixed inner track <NUM> relative to the structure <NUM> is used to locate and hold frames <NUM> for installation at the IML surface of the structure <NUM>. In further embodiments, the frames <NUM> are held by other components such as guides or rails that are discrete from the components discussed herein.

Any structure that is fastened directly to the structure <NUM> (e.g., a skin <NUM> of a fuselage <NUM> as shown in <FIG>) could be installed via the operations of the end effectors <NUM>, <NUM> discussed herein. These structures include door surrounds or window surrounds, such as the surround <NUM>. Fasteners <NUM> for door or window surrounds within reach of a pair <NUM> of end effectors <NUM>, <NUM> can be installed during one pause between pulses of the fuselage structure, and fasteners <NUM> within reach during a next pause between pulses can then be installed by the same end effectors. In this way, the fasteners <NUM> around a perimeter of an opening in structure <NUM> are installed. In further examples, the structural component may comprise another section of fuselage that will be longitudinally spliced with a current section of fuselage in order to form a longer section of fuselage. In still further examples, fuselage panels that each comprise a portion of the radius of a fuselage may be joined in a butted or lapped longitudinal splice to form a more complete fuselage section circumferentially.

In a further embodiment, the IML end effectors and the OML end effectors are capable of moving longitudinally with respect to structure <NUM>, in order to install longitudinal splice fasteners within a certain reach of a work station in the series of work stations, as described in more detail with respect to <FIG>. These end effectors <NUM>, <NUM> can move horizontally over a short length, installing splice fasteners in order to assemble half barrel sections from individual barrel sections each comprising one-sixth of a barrel. These smaller barrel sections are tacked together with temporary fasteners prior to permanent fastener installation. This fastener installation system <NUM> is capable of being used to form half barrel sections for either composite or metallic aircraft production. In this manner, metallic aircraft can be assembled in a pulsed line.

In step <NUM>, the structure <NUM> is clamped by pressing the first end effector, such as the IML end effector <NUM>, and the second end effector, such as the OML end effector <NUM>, into the structure <NUM>. For example, a "one-up" clamping may be performed via application of a suction element in one of the end effectors <NUM>, <NUM> to the structure <NUM>, or a clamp may be performed by pressing an end effector <NUM> at the fixed inner track <NUM> against the structure <NUM> and an end effector <NUM> at the fixed outer track <NUM>, thereby sandwiching the structure <NUM> in place between the end effectors <NUM>, <NUM>. This enables operations of sealing, drilling, and fastener installation to be performed in one single process, which can eliminate the need to match drill all of the holes <NUM> in a panel assembly and take structures apart for cleaning and deburring before adding sealant, reassembling, and installing fasteners. Drilling a fastener hole may include drilling a countersink hole.

In step <NUM>, the fastener <NUM> is applied to the structure <NUM>. Applying the fastener <NUM> to the structure <NUM> can include drilling a hole <NUM> through the structure <NUM> using at least one of the end effectors <NUM>, <NUM>. For example, in an embodiment where the fastener <NUM> is a lockbolt, the second end effector may drill out a hole <NUM> in the structure <NUM> and drive a lockbolt through the hole <NUM>, and the first end effector may dispose a collar over the lockbolt and swage the collar into place. In one embodiment, applying the fastener <NUM> comprises inserting a fastener <NUM> into the fastener hole <NUM>. In one embodiment, the structure <NUM> comprises a fuselage portion <NUM> (shown in <FIG>) of a fuselage of an aircraft, and applying the fastener <NUM> comprises driving the fastener through a frame (e.g., the frame <NUM> shown in <FIG>) disposed at the IML surface (e.g., IML surface <NUM> shown in <FIG>) of the structure <NUM> (e.g., the fuselage portion <NUM> shown in <FIG>) as well as the structure <NUM> itself. During step <NUM> and step <NUM>, forces applied during clamping and fastener installation are transferred through the end effectors <NUM>, <NUM> and into the fixed tracks <NUM>, <NUM>. At step <NUM>, the structure <NUM> is released by separating the first end effector and the second end effector from the structure <NUM>. After step <NUM>, the end effectors <NUM>, <NUM> can be moved to a different fastener installation location <NUM> on the structure <NUM> and/or the structure <NUM> can be moved to a subsequent work station and/or pulsed line system in the pulsed manufacturing line <NUM>.

Steps <NUM>-<NUM> may be iterated multiple times each time that the structure <NUM> is paused in the same work station or to a different work station, in order to install a large number of fasteners <NUM> along different radial positions. The iteration may comprise moving the first end effector and the second end effector to a new position along a curvature of the structure <NUM> (see, e.g., step <NUM>), clamping <NUM> the structure <NUM> by pressing the first end effector and the second end effector into the structure <NUM>, and applying another fastener <NUM> to the structure <NUM>.

Method <NUM> can provide a substantial technical benefit over prior solutions, because method <NUM> can ensure that mobile end effectors, such as end effectors <NUM>, <NUM>, may be utilized to install fasteners <NUM> at a variety of locations along a contoured structure <NUM>. Furthermore, because the end effectors <NUM>, <NUM> are disposed along fixed tracks, such as tracks, the end effectors <NUM>, <NUM> can reliably install fasteners <NUM> in the same positions along the contour of the structure <NUM>, regardless of the amount of distance that the structure <NUM> has traveled along rail <NUM>. Hence, unlike flexible track systems that can require installation and removal of a track within the fuselage itself (e.g., for each of multiple portions along the length of the fuselage), the fastener installation system <NUM> having fixed tracks described herein may be rapidly operated by moving the structure <NUM> lengthwise, pausing the structure <NUM>, applying fasteners <NUM>, and then moving the structure <NUM> lengthwise again. Moving lengthwise moves the structure <NUM> in the longitudinal direction <NUM>.

Furthermore, flex track systems can rely upon a structure already being assembled in order to provide structural support for the track, while method <NUM> utilizes a track that is structurally independent of structure <NUM>. Still further, flex track systems can require that the track and end effector be moved to a particular location at a structure <NUM>. In the present system, the structure <NUM> is moved to the track and fasteners <NUM> are installed in pulses in between movements of the structure <NUM> along the pulsed manufacturing line <NUM>. Therefore, after each pulse of movement of structure <NUM>, the structure <NUM> can be rapidly indexed to the tracks before work begins. Fastener installation is then performed, work is stopped, and a next portion of the structure <NUM> is brought into range of the end effectors <NUM>, <NUM> on the fixed tracks for additional fastener assembly.

<FIG> illustrate fastener installation in a specific embodiment where the structure <NUM> (shown in <FIG>) is a structure <NUM> that comprises a fuselage portion <NUM>, such as a half-barrel section of a fuselage, having a constant cross-section along its length. The fuselage portion <NUM> described with respect to <FIG> can be a portion of the fuselage <NUM> shown in <FIG>.

<FIG> is a perspective view of a fastener installation system <NUM> in an illustrative embodiment. The fastener installation system <NUM> is a particular example of the fastener installation system <NUM> shown schematically in <FIG>. In this embodiment, fastener installation system <NUM> includes rails <NUM> which are installed at a factory floor <NUM>. The rails <NUM> are an example of the rail <NUM> shown in <FIG>. The rails <NUM> move the structure <NUM> in a longitudinal direction <NUM> toward and/or through the fastener installation system <NUM>. Mobile carts <NUM> travel along the rails <NUM> and include clamps <NUM> which hold the structure <NUM> in the form of a half-barrel section of an aircraft fuselage (e.g., fuselage <NUM> shown in <FIG> and <FIG>) having an IML surface <NUM> and an OML surface <NUM>. Braces <NUM> disposed at ends of the structure <NUM> help to retain an arcuate shape of the structure <NUM> during transport. However, in further embodiments the brace <NUM> is omitted. The braces <NUM> are an example of the braces <NUM> shown in <FIG>.

During assembly operations, structure <NUM> proceeds within the gap G between a fixed inner track <NUM> and a fixed outer track <NUM>. The fixed inner track <NUM> is an example of the fixed inner track <NUM> shown in <FIG>, and the fixed outer track <NUM> is an example of the fixed outer track <NUM> shown in <FIG>. The fixed inner track <NUM> is positioned on an IML side <NUM> of the fastener installation system <NUM> and/or the structure <NUM>, and the fixed outer track <NUM> is positioned on OML side <NUM> of the fastener installation system <NUM> and/or structure <NUM>. Fixed inner track <NUM> has a first set <NUM> of end effectors <NUM>, <NUM>, and <NUM> disposed along a first semicircle <NUM>. The end effectors <NUM>, <NUM>, and <NUM> are each an example of the IML end effector <NUM> shown in <FIG>. Fixed outer track <NUM> has a second set <NUM> of end effectors <NUM>, <NUM>, and <NUM> disposed along a second semicircle <NUM>. The end effectors <NUM>, <NUM>, and <NUM> are each an example of the OML end effector <NUM> shown in <FIG>. Referring to <FIG>, each IML end effector <NUM>, <NUM>, and <NUM> is paired up with a respective OML end effector <NUM>, <NUM>, and <NUM> to create pairs <NUM>, <NUM>, <NUM> of end effectors. Each pair <NUM>, <NUM>, and <NUM> is an example of a pair <NUM> as shown in <FIG>. Although three pairs <NUM>, <NUM>, <NUM> of end effectors are shown in <FIG>, any number of pairs <NUM>, <NUM>, <NUM> can be included in the fastener installation system <NUM>.

As shown in <FIG>, the second semicircle <NUM> is larger than the first semicircle (i.e., has a larger diameter) and is concentric with the first semicircle <NUM>. When structure <NUM> is placed between the first semicircle <NUM> and the second semicircle <NUM>, the IML surface <NUM> and OML surface <NUM> are also concentric with first semicircle <NUM>. The motion of structure <NUM> in the direction indicated by the arrow is periodically paused, causing the structure <NUM> to move in pulses as the structure <NUM> proceeds between the fixed tracks <NUM>, <NUM>. During each pause, the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> of the tracks <NUM>, <NUM> install fasteners <NUM> (shown in <FIG>) into holes <NUM> (shown in <FIG>) along the contour of the structure <NUM>. The structure <NUM> is then moved again, presenting another hoop-wise (or half-barrel-shaped) portion of the structure <NUM> along the length L of the structure <NUM> for receiving fasteners <NUM>.

In a further embodiment, the structure <NUM> is pulsed a distance equal to the space between fastener installation locations, such as fastener installation locations (shown in <FIG>), in the longitudinal direction <NUM> and longitudinal rows of fasteners are installed, such as for lap or butt splices to join fuselage panels. In still further embodiments, multiple end effector pairs install fasteners <NUM> for longitudinal splices and then switch to installing fasteners in a hoop-wise fashion to install frames, such as securing the frame <NUM> to the skin <NUM> as shown in <FIG>.

In one embodiment, end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> on the fixed inner track <NUM> and the fixed outer track <NUM> are also capable of limited longitudinal motion in the longitudinal directions <NUM> indicated by the arrow. The OML end effectors <NUM>, <NUM>, <NUM> move synchronously with the IML end effectors <NUM>, <NUM>, <NUM> in the longitudinal direction <NUM>. In such an embodiment, the IML end effectors <NUM>, <NUM>, <NUM> are coupled to the fixed inner track <NUM> via inner longitudinal rails <NUM>. Similarly, the OML end effectors <NUM>, <NUM>, <NUM> are coupled to the fixed outer track <NUM> via outer longitudinal rails <NUM>. The IML end effectors <NUM>, <NUM>, <NUM> move with respect to the fixed inner track <NUM> in the longitudinal directions <NUM> along the inner longitudinal rails <NUM>. The OML end effectors <NUM>, <NUM>, <NUM> move with respect to the fixed outer track <NUM> in the longitudinal directions <NUM> along the outer longitudinal rails <NUM>. This may facilitate certain assembly operations, such as those related to performing longitudinal splices.

<FIG> is an end view of the fastener installation system <NUM> prior to receiving the structure <NUM>, and corresponds with view arrows <NUM> of <FIG>. In <FIG>, a controller, such as the controller <NUM> shown in <FIG>, has assigned IML end effectors <NUM>-<NUM> to different radial zones <NUM>, <NUM>, <NUM> at the structure <NUM> and has also assigned OML end effectors <NUM>-<NUM> to the different radial zones <NUM>, <NUM>, <NUM> at the structure <NUM>. While three pairs <NUM>, <NUM>, <NUM> of end effectors and three radial zones <NUM>, <NUM>, <NUM> are shown, in further embodiments any suitable number of pairs and radial zones can be utilized.

Each IML end effector <NUM>, <NUM>, <NUM> in the first set <NUM> and each OML end effector <NUM>, <NUM>, <NUM> in the second set <NUM> is operated exclusively within the radial zone <NUM>, <NUM>, or <NUM> that it has been assigned to. Specifically, the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> are grouped into pairs <NUM>, <NUM>, <NUM> (one inner end effector and one outer end effector) that each operate in a coordinated fashion to install fasteners <NUM> in a separate radial zone/portion <NUM>, <NUM>, <NUM> of the structure <NUM>. For example, end effector <NUM> and end effector <NUM> operate together as a pair <NUM> in radial zone <NUM> disposed between boundary <NUM> and boundary <NUM>, end effector <NUM> and end effector <NUM> operate together as a pair <NUM> in radial zone <NUM> disposed between boundary <NUM> and boundary <NUM>, and end effector <NUM> and end effector <NUM> operate together as a pair <NUM> in radial zone <NUM> disposed between boundary <NUM> and boundary <NUM>.

In further embodiments, radial zones <NUM>, <NUM>, <NUM> are not exclusive and therefore partly overlap, which facilitates the ability of end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> to perform fastener installation in boundary areas between radial zones. For example, at least two of the radial zones <NUM>, <NUM> partially overlap another radial zone <NUM>. Actions performed by pairs <NUM>, <NUM>, <NUM> of end effectors are coordinated to prevent collisions between end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> in different pairs. For example, the controller <NUM> may operate pairs <NUM>, <NUM>, <NUM> of end effectors such that the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> proceed in a first circumferential direction (e.g., clockwise) together across their respective radial portions, and then proceed in a second circumferential direction (e.g., counter-clockwise) together across their respective radial portions. This ensures that the pairs <NUM>, <NUM>, <NUM> of end effectors remain separated by a desired amount of empty space in order to prevent collisions.

In one embodiment, the motions of the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> are preprogrammed into the NC programing saved in the memory <NUM> (shown in <FIG>) for the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> to help ensure collision avoidance. In further embodiments, NC programming is supplemented with proximity sensors (e.g., laser sensors, cameras, ultrasonic sensors, etc.) that provide input used by the controller <NUM> to automatically pause or alter operations of the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> in order to perform collision avoidance. In this manner, fastener installation may include moving the first set <NUM> of end effectors and the second set <NUM> of end effectors along a first circumferential direction, such as the clockwise direction <NUM>, to apply multiple fasteners <NUM>, and moving the first set <NUM> of end effectors and the second set <NUM> of end effectors along a second circumferential direction, such as the counterclockwise direction <NUM>, that is opposed to the first circumferential direction to apply additional fasteners (e.g., after the structure <NUM> has been pulsed).

<FIG> is an end view of the fastener installation system <NUM> after receiving the structure <NUM>. That is, structure <NUM> has been pulsed along rails <NUM> to a location where a portion of structure <NUM> ready for fastener installation is disposed between fixed inner track <NUM> and fixed outer track <NUM>. In <FIG>, structure <NUM> is illustrated disposed between fixed inner track <NUM> and fixed outer track <NUM>. Assume for this depiction that movement of structure <NUM> has paused. Also in this end view, the curved section <NUM> of the structure <NUM> is shown.

The pairs <NUM>, <NUM>, <NUM> of end effectors proceed to install fasteners <NUM> into holes <NUM> within their corresponding zones <NUM>, <NUM>, <NUM> in a hoop-wise direction as the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> perform coordinated sweeps in clockwise or counterclockwise directions (or both) during fastener installation. In one embodiment, the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> initiate in the positions depicted in <FIG> and work in a counterclockwise direction <NUM> until stopping at the far end of the counter clockwise arc. The end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> then wait until the next pulse/movement of the structure <NUM> and work in a clockwise direction <NUM> toward the starting point shown in <FIG>. That is, after each pulsed movement of the structure <NUM> through the fastener installation system <NUM>, the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> switch their direction of operation from the counterclockwise direction <NUM> to the clockwise direction <NUM>. Thus, all of the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> work in the counterclockwise direction <NUM>, then wait for a pulsed movement, then work in the clockwise direction <NUM>, then wait for a pulsed movement, and so on. This iterative, coordinated movement between the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> and the structure <NUM> may be performed without any type of "carriage return" type of operation.

In another embodiment, the pairs <NUM>, <NUM>, <NUM> of end effectors install fasteners <NUM> in the clockwise direction <NUM> until reaching the end of their radial zone <NUM>, <NUM>, or <NUM>, and then reset in the counterclockwise direction <NUM> back to the beginning of their radial zone <NUM>, <NUM>, <NUM> in a manner similar to operating a carriage return of a typewriter. Thus, the pairs <NUM>, <NUM>, <NUM> of end effectors all work in the clockwise direction <NUM> after a pulsed movement, then return to their starting positions and work in the clockwise direction <NUM> again after a next pulsed movement. Similar operations may, of course, be performed for counterclockwise operation instead of clockwise operation.

In still further embodiments, after the structure <NUM> has been pulsed, the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> move incrementally in one direction (e.g., clockwise, counterclockwise), and install fasteners <NUM> into holes <NUM> in between the pulsed movements, as each end effector <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> proceed across its radial zone <NUM>, <NUM>, <NUM>. Then the end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> move in an opposite direction back to a starting point in order to prepare for installing fasteners <NUM> after the structure <NUM> has been pulsed again. The structure <NUM> may then be pulsed to the next fastener installation location (shown in <FIG>) on the structure <NUM>, and the pairs <NUM>, <NUM>, <NUM> of end effectors proceed to install fasteners into holes <NUM> as the pairs <NUM>, <NUM>, <NUM> move in the counterclockwise direction <NUM>.

In a still further embodiment, the fixed tracks <NUM>, <NUM> are located closer to the respective IML surface <NUM> or OML surface <NUM> of the structure <NUM>, such that IML end effectors <NUM>, <NUM>, <NUM> are located between the structural portions of the fixed inner track <NUM> (or even inboard of the fixed inner track <NUM>) and the fixed inner track <NUM> is located just off of the IML surface <NUM> on which work is to be performed. In a similar fashion, OML end effectors <NUM>, <NUM>, <NUM> are located between structural components of the fixed outer track <NUM> (or even outboard of the fixed outer track <NUM>) and the fixed outer track located just off of the OML surface <NUM> on which work is to be performed.

Referring to <FIG> and <FIG>, the fastener installation system <NUM> can also have adjacent frame installation stations <NUM>, wherein end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> in each station <NUM> operate in different circumferential directions, or in the same circumferential direction, such as the clockwise direction <NUM> or the counterclockwise direction <NUM> (e.g., to install a splice between half-barrel sections, or to install a window or door surround). Each frame installation station of the fastener installation system <NUM> includes a fixed inner track <NUM>, a fixed outer track <NUM>, IML end effectors <NUM>, <NUM>, <NUM> associated with the fixed inner track <NUM>, and OML end effectors <NUM>, <NUM>, <NUM> associated with the fixed outer track <NUM>.

<FIG> is a further perspective view of the fastener installation system <NUM> that corresponds with view arrows <NUM> of <FIG>. As shown in <FIG>, a clearance C between the IML end effectors <NUM>, <NUM>, <NUM> along the fixed inner track <NUM> and the OML end effectors <NUM>, <NUM>, <NUM> along the fixed outer track <NUM> is greater than a thickness T of brace <NUM>. This spacing ensures that structure <NUM> may proceed between the fixed tracks <NUM>, <NUM> without encountering physical interference.

<FIG> illustrate further methods for performing fastener installation using the fastener installation system <NUM>, <NUM> (shown in <FIG> and <FIG>). The methods <NUM>, <NUM>, <NUM>, and <NUM> include pulsing the structure <NUM>, <NUM> towards and/or through the fastener installation system <NUM>, <NUM>. Pulsing enables the methods <NUM>, <NUM>, <NUM>, <NUM> to install fasteners <NUM> by attaching the fasteners <NUM> along the longitudinal portion <NUM> of the structure <NUM>, <NUM>, which attaches the fasteners <NUM> along the longitudinal axis A of the structure <NUM>, <NUM>. The installation of the fasteners <NUM> can secure a component, such as a frame <NUM> (shown in <FIG>) or a surround <NUM> (shown in <FIG> and <FIG>) to the structure <NUM>, <NUM> (e.g., a fuselage portion <NUM> having skin <NUM>).

Method <NUM> provides an alternate technique for utilizing the end effector and track systems discussed herein in an illustrative embodiment. According to method <NUM> of <FIG>, step <NUM> comprises pulsing a structure <NUM>, <NUM> (shown in <FIG> and <FIG>) comprising a fastener installation location <NUM> towards the fastener installation system <NUM>, <NUM>. For example, the structure <NUM>, <NUM> is moved in the longitudinal direction <NUM> shown in <FIG>. During the pulsing, the structure <NUM>, <NUM> is moved along the rail <NUM>, <NUM> that is part of the pulsed manufacturing line <NUM>. In one embodiment, pulsing includes moving the structure <NUM> longitudinally (e.g., a distance of <NUM> meters (eight feet)) towards and/or through the fastener installation system <NUM>, <NUM>. For example, during a pulse, the structure <NUM>, <NUM> is moved in the longitudinal direction <NUM> by a predetermined distance. The motion of structure <NUM>, <NUM> may then be paused in order for work to be performed by the fastener installation system <NUM>, <NUM>.

In step <NUM>, at least one fastener <NUM> is installed at the fastener installation location <NUM> via end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> (shown in <FIG> and <FIG>) that are supported by tracks <NUM>, <NUM> and <NUM>, <NUM> (shown in <FIG> and <FIG>) that are independent of the structure <NUM>, <NUM>. Step <NUM> may be performed via the coordinated end effector operations discussed above with regard to method <NUM> of <FIG>. The installation can include attaching fasteners <NUM> along the curved section <NUM> (shown in <FIG>) of the structure <NUM>, <NUM>. Further, the installation can include attaching the fasteners <NUM> along the longitudinal portion <NUM> of the structure <NUM>, <NUM>. Longitudinal operations may further support installation of fasteners <NUM> for door surrounds, stringer splices, or other components.

Method <NUM> provides a further alternate technique for utilizing the end effector and track systems discussed herein in an illustrative embodiment. According to method <NUM> of <FIG>, step <NUM> comprises pulsing a structure <NUM>, <NUM> comprising a fastener installation location <NUM> towards the fastener installation system <NUM>, <NUM> (shown in <FIG> and <FIG>). In one embodiment, pulsing <NUM> the structure <NUM>, <NUM> comprises moving structure <NUM>, <NUM> longitudinally towards and/or through the fastener installation system <NUM>, <NUM> (e.g., by <NUM> meters (four feet), <NUM> meters (eight feet), etc.). The motion of structure <NUM>, <NUM> may then be paused in order for work to be performed by the fastener installation system <NUM>, <NUM>. This is similar to step <NUM> in method <NUM> in <FIG>.

In step <NUM>, the structure <NUM> is clamped between an IML end effector <NUM>, <NUM>, <NUM>, <NUM> and an OML end effector <NUM>, <NUM>, <NUM>, <NUM> at the fastener installation system <NUM>, <NUM>. The clamping <NUM> may be performed by pressing the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> towards each other while the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> are disposed over a fastener installation location <NUM>, as described with respect to steps <NUM> and <NUM> in <FIG>. Step <NUM> is performed while movement of the structure <NUM>, <NUM> is paused.

In step <NUM>, a fastener <NUM> is installed at the structure <NUM>, <NUM> via the IML end effector <NUM>, <NUM>, <NUM>, <NUM> and the OML end effector <NUM>, <NUM>, <NUM>, <NUM>. The installation step may comprise the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> performing drilling a hole <NUM>, cleaning the hole <NUM>, and installation of the fastener <NUM> into the hole <NUM> in a desired location. This may be performed via the coordinated end effector operations discussed above with regard to method <NUM> of <FIG> and, more specifically, via step <NUM>. The installation can include attaching fasteners <NUM> along the curved section <NUM> (shown in <FIG>) of the structure <NUM>, <NUM>. Further, the installation can include attaching the fasteners <NUM> along the longitudinal portion <NUM> of the structure <NUM>, <NUM>.

In further embodiments, a one-up assembly may be performed as the method <NUM> via the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> discussed herein, wherein forces applied by the end effectors <NUM>, <NUM> during drilling and fastener installation are resisted by one or more indexing elements that hold the structure <NUM>, <NUM> in place. Further, forces applied during clamping <NUM> and fastener installation are transferred through the end effectors <NUM>, <NUM> and into the tracks <NUM>, <NUM>.

Method <NUM> provides a technique for utilizing an end effector that moves longitudinally/lengthwise with respect to a structure to facilitate fastener installation. Method <NUM> could be used when the fastener installation system <NUM>, <NUM> has end effectors <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM> on the fixed inner track <NUM> and the fixed outer track <NUM> that are capable of limited longitudinal motion in the longitudinal directions <NUM> shown in <FIG>.

According to method <NUM>, step <NUM> includes pulsing the structure <NUM>, <NUM> comprising a fastener installation location <NUM> longitudinally towards and/or through the fastener installation system <NUM>, <NUM>, similarly to steps <NUM> and <NUM> described with respect to <FIG>. In step <NUM>, at least one fastener <NUM> is installed at the fastener installation location <NUM> via end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> disposed at an IML surface <NUM> and an OML surface <NUM> of the structure <NUM>, <NUM>. Installation step <NUM> is similar to step <NUM> (shown in <FIG>), step <NUM> (shown in <FIG>), and step <NUM> (shown in <FIG>).

In step <NUM>, the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> move in the longitudinal directions <NUM> with respect to the structure <NUM>, <NUM>. For example, the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> move by independently traveling in the longitudinal direction <NUM> with respect to the fixed inner track <NUM>, <NUM> and the fixed outer track <NUM>, <NUM> along the inner longitudinal rails <NUM> and outer longitudinal rails <NUM>, respectively.

In step <NUM>, additional fasteners are installed via the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> after the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> have been moved. The installation is similar to step <NUM>, and steps <NUM> and <NUM> can be performed as described with respect to method <NUM> (shown in <FIG>). The installation can include attaching fasteners <NUM> along the curved section <NUM> (shown in <FIG>) of the structure <NUM>, <NUM>. Further, the installation <NUM>, <NUM> can include attaching the fasteners <NUM> along the longitudinal portion <NUM> of the structure <NUM>, <NUM>. In this manner, the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> install fasteners <NUM> along newly exposed longitudinal portions <NUM> of the structure <NUM>, <NUM>. In further embodiments, the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> also move in an arc-wise direction, such as a clockwise direction <NUM> and/or counterclockwise direction <NUM>, relative to the structure <NUM>, <NUM> during fastener installation, as shown in <FIG>. In the manner of method <NUM>, the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> may perform a limited amount of longitudinal motion in order to enhance the ease of performing a lengthwise splice, stringer splices, or while installing intercostals, surrounds, clips/supports, etc., even though structure <NUM>, <NUM> is already being periodically pulsed in the longitudinal direction.

Method <NUM> illustrates a technique for installing surrounds, such as surround <NUM> shown in <FIG> and <FIG>, in an illustrative embodiment. Step <NUM> comprises pulsing a structure <NUM>, <NUM> having a fastener installation location <NUM> towards and/or through the fastener installation system <NUM>, <NUM>. Step <NUM> is similar to steps <NUM>, <NUM>, and <NUM> as previously described. Step <NUM> includes installing a first subset of fasteners <NUM> for a surround <NUM> (e.g., a door surround, window surround, etc.) that will cover a later-placed cut-out in the structure <NUM>, <NUM>, via end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM> that are supported by tracks <NUM>, <NUM> and <NUM>, <NUM>, which are independent of the structure <NUM>, <NUM>. The first subset of fasteners <NUM> may comprise fasteners <NUM> installed at locations that are presently within reach of the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM>. The installation <NUM> of the fasteners <NUM> is similar to how the fasteners <NUM> are installed in the previously-described method <NUM> (shown in <FIG>).

Step <NUM> comprises pulsing the structure <NUM>, <NUM> further through the fastener installation system <NUM>, <NUM>. This operation is similar to step <NUM> and makes remaining locations for installing fasteners <NUM> in the surround <NUM> available to the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM>. After each pulsing step (which may include pulsing steps described with respect to <FIG>), the method <NUM> can include indexing the structure <NUM>, <NUM>. For example, the structure <NUM>, <NUM> can be indexed using the section <NUM> of manufacturing excess/sacrificial material, using notches or holders disposed at the fixed inner track <NUM> and/or fixed outer track <NUM>, and/or using one or more indexing elements that hold the structure <NUM>, <NUM> in place.

In step <NUM>, a second subset of fasteners <NUM> are installed for the surround <NUM> via the end effectors <NUM>, <NUM>, <NUM>, <NUM> and <NUM>, <NUM>, <NUM>, <NUM>, similarly to step <NUM>. In one embodiment, installing <NUM> the second subset of fasteners <NUM> comprises distributing fastener installation operations for the surround <NUM> among different end effectors. The installing steps secure the surround <NUM> to the structure <NUM>, <NUM>, such that the surround will cover a cut-out in the structure <NUM>, <NUM>. The installing steps can be performed by at least one pair of end effectors <NUM>, <NUM> operating on a fore portion of the surround <NUM>, and by at least one other pair of end effectors <NUM>, <NUM> operating on an aft portion of the surround <NUM>, wherein the pairs <NUM> operate simultaneously on the fore portion and the aft portion.

Further, installation of the fasteners <NUM> can include attaching the fasteners <NUM> along the curved section <NUM> (shown in <FIG>) of the structure <NUM>, <NUM>. Further, the installation <NUM>, <NUM> can include attaching the fasteners <NUM> along the longitudinal portion <NUM> of the structure <NUM>, <NUM>.

Installing fasteners as discussed in the above methods <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may comprise attaching fasteners <NUM> along a hoop-wise portion <NUM> of a structure <NUM>, <NUM>, attaching fasteners <NUM> along a length L of the structure <NUM>, <NUM>, securing a surround <NUM> that covers a cut-out in the structure <NUM>, <NUM> (e.g., by installing fasteners along a perimeter of the surround <NUM>, via different end effectors), securing a frame <NUM> to a skin <NUM> of the structure <NUM>, <NUM> (shown in <FIG>), etc. The methods <NUM>, <NUM>,<NUM>, and <NUM> include iteratively pulsing the structure <NUM>, <NUM> toward and/or through the fastener installation system <NUM>, <NUM> and installing fasteners <NUM> to the structure <NUM>, <NUM>.

In one embodiment, the methods discussed above further include aligning an Outer Mold Line (OML) end effector and an Inner Mold Line (IML) end effector with the structure, and the installing the fasteners via the OML end effector and the IML end effector. Other potential additional steps may include indexing the structure after the structure is pulsed. This may comprise placing the structure in a known location relative to the tracks (e.g., by placing the structure against an indexing element which is fixed in position relative to the tracks), in order to determine a location of the structure in a coordinate space used by the OML end effectors and the IML end effectors. In a further embodiment, the installing is performed by at least one pair of end effectors operating on a fore portion of the surround, and by at least one pair of end effectors operating on an aft portion of the surround, wherein the pairs operate simultaneously.

In the following examples, additional processes, systems, and methods are described in the context of a fastener installation system. Any or all of the methods <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> described herein can be embodied on a non-transitory computer-readable medium as programmed instructions.

Referring more particularly to <FIG>, embodiments of the disclosure may be described in the context of aircraft manufacturing and service in method <NUM> as shown in <FIG> and an aircraft <NUM> as schematically shown in <FIG>. During pre-production, method <NUM> may include specification and design <NUM> of the aircraft <NUM> and material procurement <NUM>. During production, component and subassembly manufacturing <NUM> and system integration <NUM> of the aircraft <NUM> takes place. The methods <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> (shown in <FIG> and <FIG>) may be performed during component and subassembly manufacturing <NUM>.

Thereafter, the aircraft <NUM> may go through certification and delivery <NUM> in order to be placed in service <NUM>. While in service by a customer, the aircraft <NUM> is scheduled for routine work in maintenance and service <NUM> (which may also include modification, reconfiguration, refurbishment, and so on). Systems and methods embodied herein may be employed during any one or more suitable stages of the production and service described in method <NUM> (e.g., specification and design <NUM>, material procurement <NUM>, component and subassembly manufacturing <NUM>, system integration <NUM>, certification and delivery <NUM>, service <NUM>, maintenance and service <NUM>) and/or any suitable component of aircraft <NUM> (e.g., airframe <NUM>, systems <NUM>, interior <NUM>, propulsion system <NUM>, electrical system <NUM>, hydraulic system <NUM>, environmental system1130).

As shown in <FIG>, the aircraft <NUM> produced by method <NUM> may include an airframe <NUM> with a plurality of systems <NUM> and an interior <NUM>. The airframe <NUM> includes a fuselage <NUM>, and the fuselage <NUM> includes the structure <NUM> as assembled using the fastener installation system <NUM> (shown in <FIG>) and the method <NUM> (shown in <FIG>). Examples of systems <NUM> include one or more of a propulsion system <NUM>, an electrical system <NUM>, a hydraulic system <NUM>, and an environmental system <NUM>. Any number of other systems may be included. Although an aerospace example is shown, the principles of the invention may be applied to other industries, such as the automotive industry.

<FIG> is a cross-sectional view of the aircraft <NUM> shown schematically in <FIG>. The aircraft <NUM> includes the airframe <NUM> having the fuselage <NUM>. The portion of the fuselage <NUM> shown in <FIG> can be the fuselage portion <NUM> of the structure <NUM>, <NUM> that was assembled using the fastener installation system <NUM>, <NUM> and the methods <NUM>, <NUM>, <NUM>, <NUM>, <NUM>. The fuselage <NUM>, and fuselage portion <NUM>, includes frames <NUM>. The frames <NUM> have fasteners <NUM> driven therethrough. The fasteners <NUM> attach the frames <NUM> to a skin <NUM> of the fuselage <NUM> (and fuselage portion <NUM>). For example, holes <NUM> extend through the frame <NUM> and skin <NUM>, and the fasteners <NUM> are inserted through the holes <NUM> to secure the frame <NUM> to the skin <NUM>. The fuselage <NUM> also includes stringers <NUM>. In the example shown in <FIG>, the fuselage also includes surrounds <NUM>.

As already mentioned above, fastener installation system <NUM>, <NUM> and methods <NUM>, <NUM>, <NUM>, <NUM>, <NUM> embodied herein may be employed during any one or more of the stages of the production and service described in method <NUM>. For example, components or subassemblies corresponding to component and subassembly manufacturing <NUM> may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft <NUM> is in service. Also, one or more system embodiments, method embodiments, or a combination thereof may be utilized during the subassembly manufacturing <NUM> and system integration <NUM>, for example, by substantially expediting assembly of or reducing the cost of an aircraft <NUM>. Similarly, one or more of system embodiments, method embodiments, or a combination thereof may be utilized while the aircraft <NUM> is in service, for example and without limitation during the maintenance and service <NUM>. For example, the techniques and systems described herein may be used for material procurement <NUM>, component and subassembly manufacturing <NUM>, system integration <NUM>, service <NUM>, and/or maintenance and service <NUM>, and/or may be used for airframe <NUM> and/or interior <NUM>. These techniques and systems may even be utilized for systems <NUM>, including, for example, propulsion system <NUM>, electrical system <NUM>, hydraulic system <NUM>, and/or environmental system <NUM>.

In one embodiment, a part, such as the structure <NUM>, <NUM> (shown in <FIG> and <FIG>), comprises a portion of airframe <NUM>, and is manufactured during component and subassembly manufacturing <NUM> using, for example, the method <NUM> (shown in <FIG>).

Claim 1:
A method (<NUM>) for applying fasteners (<NUM>) to a structure (<NUM>, <NUM>, <NUM>), the method (<NUM>) comprising:
- disposing (<NUM>) a first set (<NUM>) of end effectors (<NUM>, <NUM>, <NUM>, <NUM>) along a fixed inner track (<NUM>, <NUM>) that follows an Inner Mold Line (IML) surface (<NUM>) of the structure (<NUM>, <NUM>);
- disposing (<NUM>) a second set (<NUM>) of end effectors (<NUM>, <NUM>, <NUM>, <NUM>) along a fixed outer track (<NUM>, <NUM>) that follows an Outer Mold Line (OML) surface (<NUM>) of the structure (<NUM>, <NUM>);
- aligning (<NUM>) a first end effector (<NUM>, <NUM>) along the fixed inner track (<NUM>, <NUM>) with a second end effector (<NUM>, <NUM>) along the fixed outer track (<NUM>, <NUM>);
- clamping (<NUM>) the structure (<NUM>, <NUM>) between the first end effector (<NUM>, <NUM>) and the second end effector (<NUM>, <NUM>) by pressing the first end effector (<NUM>, <NUM>) and the second end effector (<NUM>, <NUM>) against the structure (<NUM>, <NUM>); and
- applying (<NUM>) a fastener (<NUM>) to the structure (<NUM>, <NUM>).
wherein the fixed inner track (<NUM>, <NUM>) includes a first semicircle (<NUM>) and wherein the fixed outer track (<NUM>, <NUM>) includes a second semicircle (<NUM>) that is larger than the first semicircle (<NUM>) and concentric with the first semicircle (<NUM>) such that there is a gap G between the fixed inner track and the fixed outer track for a structure (<NUM>) to pass through;
or
wherein the fixed inner track (<NUM>, <NUM>) and the fixed outer track (<NUM>, <NUM>) have varying radii along their entire lengths, and wherein there is a gap G between the fixed inner track and the fixed outer track for a structure (<NUM>) to pass through.