Dynamic collar swage conformance checking based on swage tool parameters

Systems and methods are provided for inspecting fastener installation. One embodiment is a method for inspecting installation of a fastener. The method includes determining an initial distance between a nose of a swage tool and an Inner Mold Line (IML) of a part, operating the swage tool to swage a collar onto a fastener that protrudes through the IML of the part, determining a terminal distance of the nose to the IML during swaging, prior to a pintail of the fastener breaking, and arriving at a conclusion indicating a state of a fastener installation, based on the terminal distance.

FIELD

The disclosure relates to the field of assembly, and in particular, to application of fasteners in the form of lockbolts having collars for swaging.

BACKGROUND

The number of fasteners (e.g., bolts) used to assemble aircraft can be astronomical. For example, a midsize commercial jetliner can have several million fasteners that are installed to join different parts together.

Furthermore, a technician must inspect the fasteners installed by an automated tool in order to ensure that work was performed properly. Inspection of the aforesaid millions of fasteners is a labor-intensive process involving manual inspection of fasteners, for example involving manual inspection of each fastener on an aircraft.

Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues. For example, it would be desirable to have a method and apparatus that overcome a technical problem with automating the installation of fasteners.

SUMMARY

Embodiments described herein provide systems and methods which are capable of determining whether or not installation of a fastener has been completed successfully, based on locational information indicating a position of a nose of the automated installation tool. The systems and methods described herein may further consider pressure measurements for a hydraulic system that drives an automated installation tool. This provides a technical benefit because it allows the installation tool to report that a fastener should be reinstalled, if readings indicate that installation has not been completed in a desired manner. Hence, the automated installation tools described herein may forego the need for manual fastener inspection required by prior systems.

One embodiment is a method for inspecting installation of a fastener. The method includes determining an initial distance between a nose of a swage tool and an Inner Mold Line (IML) of a part, operating the swage tool to swage a collar onto a fastener that protrudes through the IML of the part, determining a terminal distance of the nose to the IML during swaging, prior to a pintail of the fastener breaking, and arriving at a conclusion indicating a state of a fastener installation, based on the terminal distance.

A further embodiment is a non-transitory computer readable medium embodying programmed instructions which, when executed by a processor, are operable for performing a method for inspecting installation of a fastener. The method includes determining an initial distance between a nose of a swage tool and an Inner Mold Line (IML) of a part, operating the swage tool to swage a collar onto a fastener that protrudes through the IML of the part, determining a terminal distance of the nose to the IML during swaging, prior to a pintail of the fastener breaking, and arriving at a conclusion indicating a state of a fastener installation, based on the terminal distance.

A further embodiment is an apparatus for inspecting installation of a fastener, the apparatus including a swage tool. The swage tool includes a nose that swages collars onto fasteners, a hydraulic cylinder that drives the nose, fingers that hold collars in place at the fasteners prior to swaging, and a sensor that measures a terminal distance between the nose and an Inner Mold Line (IML) of a part that receives the fastener.

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.

DESCRIPTION

The figures and the following description provide specific illustrative embodiments of the disclosure. 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 disclosure and are included within the scope of the disclosure. Furthermore, any examples described herein are intended to aid in understanding the principles of the disclosure, and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the disclosure is not limited to the specific embodiments or examples described below, but by the claims and their equivalents.

FIG. 1is a block diagram of a fastener installation system100in an illustrative embodiment. Fastener installation system100may comprise a platform that carries an offset collar installer for lockbolts, or may comprise any other suitable components and devices for performing swaging in order to install a fastener (e.g., a lockbolt) in place. Fastener installation system100has been enhanced in order to track a position of a nose142of a swage tool140. By tracking the position of the nose142during swaging operations, each fastener installation may be reviewed in a manner that ensures the fastener was installed in a desired manner.

In this embodiment, fastener installation system100includes controller110, which directs the operations of a hydraulic motor122, as well as other electronically manageable components of fastener installation system100. Controller110may be implemented, for example, as custom circuitry, as a hardware processor executing programmed instructions, or some combination thereof.

Controller110also controls placement of pressure foot180. Pressure foot180is utilized to clean and/or inspect one or more holes164drilled into parts160, prior to insertion of lockbolts into those holes164. Pressure foot180also applies a vacuum to facilitate clamp-up for one-up assembly. Pressure foot180may comprise a hollow channel that is placed over a drilled-out portion of part160, and may apply a vacuum that draws loose material from the drilled-out portion before a lockbolt170is inserted into place. When pressure foot180contacts the surface162of part160, a load sensor or other contact sensor coupled with pressure foot180is triggered. Based on a known distance between the pressure foot180and the nose142of swage tool140, a distance from the nose142to the surface162may be determined. After a hole164has been inspected and/or cleaned by pressure foot180, a lockbolt170is driven through the hole. A collar150is provided to fingers144via feed arm148. The collar150is placed over the lockbolt170by fingers144, and awaits swaging onto lockbolt170via action of swage tool140.

To perform swaging, controller110directs hydraulic motor122to actuate the swage tool140. Pressure generated by hydraulic motor122is applied via hydraulic line124to hydraulic cylinder126, and this pressure in hydraulic line124is monitored by a pressure sensor130. Changes in pressure move the hydraulic cylinder126, which in turn drives swage tool140. For example, increases in pressure may cause the hydraulic cylinder126to move nose142of swage tool140into contact with collar150, which is held in position by fingers144. Collar150is held in place at surface162(e.g., an Inner Mold Line (IML)) of part160over lockbolt170, which has been driven through hole164at parts160. As a part of this process, a centerline152of collar150and a centerline172of lockbolt170are made collinear. During a swaging operation, nose142acts as an anvil that swages the collar150onto lockbolt170. The swaging of collar150onto the lockbolt170fastens parts160together, and snaps the pintail174(i.e., a frangible portion of lockbolt170) off of lockbolt170. When the pintail174snaps, nose142slightly rebounds in direction R.

During the swaging process, position sensor146acquires measurements indicating a distance D between nose142and surface162, and pressure sensor130measures pressure at hydraulic cylinder126. Based on these measurements acquired during swaging, controller110characterizes each fastener installation. For example, controller110may evaluate one or more position measurements over time to determine whether the fastener has been installed as desired. In this embodiment, controller110controls the operations of marker182(e.g., an applicator of ink, stickers, or other visually distinguishing marks). Marker182is used to indicate locations of fasteners that have not been installed in a desired manner, such as fasteners that are installed out-of-tolerance. Controller110may also track identifiers or locations of such fasteners, for later reporting.

Illustrative details of the operation of fastener installation system100will be discussed with regard toFIG. 2. Assume, for this embodiment, that fastener installation system has placed a collar150onto a surface162of a part160, and awaits applied pressure that will cause the nose142to swage the collar150onto a lockbolt170.

FIG. 2is a flowchart illustrating a method200for monitoring installation of a fastener in an illustrative embodiment. The steps of method200are described with reference to fastener installation system100ofFIG. 1, but those skilled in the art will appreciate that method200may 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.

In step202, controller110determines an initial distance between nose142of the swage tool140and an IML (e.g., surface162) of part160. The initial distance is determined prior to initiating swaging operations. For example, the initial distance may be determined at the time that pressure foot180contacts the surface162, based on a known separation between a tip of pressure foot180and a tip of nose142. In a further example, the initial distance may be measured via a distancing sensor such as a laser or ultrasonic distancing sensor. In one embodiment, distance measurements for the nose142are determined based on a clamping position, minus a panel datum indicating a location of the surface162, plus a known position of the swage tool based on the clamping position, plus a constant.

In step204, controller operates the swage tool140to swage the collar150onto a fastener (e.g., lockbolt170) that protrudes through the IML. During this operation, changes in position of nose142are constantly sampled at a known rate (e.g., every five milliseconds, every twenty milliseconds, etc.) based on input from hydraulic cylinder126, or a distancing sensor (e.g., an embodiment of position sensor146) disposed at the swage tool140. Measurements of the position of nose142may indicate a distance to surface162of a part160, may indicate a distance traveled by nose142during swaging, or other parameters that may be used to infer an amount of distance that nose142has proceeded onto collar150during swaging. Controller110stores these position measurements in an internal memory. As hydraulic motor122runs, pressure is increased within hydraulic system120, which extends hydraulic cylinder126further outward. Controller110also acquires measurements from pressure sensor130as desired, for example at a sampling rate corresponding with the rate at which position is measured.

In step206, controller110determines a terminal distance of the nose142to the IML during swaging, prior to a pintail174of the fastener snapping off of the fastener. The terminal distance is the shortest distance between the nose142and the IML during the swaging operation. The terminal distance may be determined after-the-fact (i.e., after the pintail has already snapped), based on a retrospective analysis of pressure and position measurements that were acquired during swaging. Controller110may analyze hydraulic pressure readings to identify a point in time that the pintail of the fastener broke, and determine a distance D between the nose and the IML at the point in time.

Pressure measurements form a detectable peak-and-valley pattern when a pintail snaps. According to this pattern, pull pressure (i.e., pressure applied to hydraulic line124during swaging while nose142proceeds towards surface162) (which has been increasing), rapidly reduces and then rapidly increases over the peak, due to the nose142rebounding in direction R ofFIG. 1as the pintail snaps. For example, controller110may detect a point in time at which pressure has dropped at a rate of more than one hundred PSI per second within a period of fifty milliseconds, controller110interprets this point in time as indicating the snap of a pintail. Controller110may then identify a peak preceding the drop in pressure, and may determine the terminal distance based on the position of the nose at a first point in time when the peak was reached. In a further example, controller110may proceed backward from the first point in time until reaching a second point in time at which a threshold value of pressure is reached. The threshold value for pressure may be a predetermined value indicating a minimum pressure at which a pintail could snap, or may be five to ten percent less than that minimum pressure or five to ten percent less than the detected peak in pressure. Controller110may then determine the distance between the nose142and the IML at the second point in time. Thus, during operation the controller110utilizes pressure readings to determine a point in time at which to measure the terminal distance.

In step208, controller110arrives at a conclusion indicating a state of fastener installation for the fastener being installed, based on the terminal distance that was measured at a point in time indicated by pressure measurements. For example, if the terminal distance is less than a threshold amount, controller110concludes that the fastener installation has completed successfully. If the terminal distance is not less than the threshold amount, controller110concludes that the fastener installation has not completed successfully. The threshold amount of distance may be, for example, zero millimeters, less than two millimeters, or any suitable predefined distance which indicates that nose142has fully swaged the collar150into place in an in-tolerance manner.

In step210, controller110reports the state of the fastener installation for review. This may comprise controller110providing the state of the fastener installation in a digital report via a display (e.g., a screen) for review by a technician, generating and transmitting or printing a document that indicates the state of the fastener installation, etc. In one embodiment, a large number of fasteners are installed within each of multiple sections of an aircraft being assembled, and controller110provides a report for each section indicating states of fastener installation for each fastener in that section. In a further embodiment, controller110reports the state of fastener installation by activating marker182at nose142, which applies a marking fluid (e.g., a bright ink) directly onto collar150and/or the fastener to indicate the presence of an unsuccessful fastener installation. This facilitates the speed at which the fastener may be located for manual review and distinguished from other fasteners installed in the same region. In further embodiments, controller110alerts a technician immediately when an out of tolerance condition is detected, via an on-screen visual image and/or an audio indication. Steps206-208and/or210may be performed in real-time for each fastener, prior to installing a next fastener.

Method200provides a technical benefit over prior techniques because it enables the detection of conditions that previously had to be manually inspected for using a manually placed gauge (e.g., a “go-no-go” gauge), and because method200performs this detection without the need for specialized or expensive visual sensing equipment (e.g., cameras).

FIGS. 3-12illustrate an animation of an inner mold line machine of a fastener installation system that tracks nose position via a pressure sensor in accordance with an illustrative embodiment. Specifically,FIG. 3illustrates a swage tool300poised above a part350(e.g., a splice between skin panels354) into which a fastener will be installed. Fingers of the swage tool300are not shown in order to enhance clarity, but retain the collar330in place at nose310. As shown inFIG. 3, a feed arm340has supplied a collar330to a nose310of the swage tool. A pressure foot320is disposed next to the nose310, and is actuatable to be placed onto IML352of part350. Nose310has a tip312, and pressure foot320has a tip322.

InFIG. 4, feed arm340has been retracted, which prepares the nose310for swaging to be performed, by removing a component that would otherwise cause physical interference. InFIG. 5, pressure foot320is driven downward until tip322is placed into contact with part350. This operation inFIG. 5is performed in order to determine a distance (D1) between nose310and part350. Pressure foot320applies a vacuum that holds it in place at IML352. Contact between pressure foot320and IML352triggers a load cell610at swage tool300. After the load cell610is triggered, a position of the pressure foot320is determined based on a current amount of extension of the pressure foot320from a retracted position as depicted inFIG. 4(e.g., as indicated by an actuator for pressure foot320). Based on this position of tip322of pressure foot320and a known separation between tip322and tip312, an initial distance (D1) between tip312of nose310and IML352is determined inFIG. 5. InFIG. 6, an Outer Mold Line (OML) machine (not shown) drills out a hole600at part350while the vacuum is applied. Detritus resulting from drilling is removed via the vacuum applied by pressure foot320. InFIG. 7, pressure foot320is retracted, and inFIG. 8, swage tool300is laterally repositioned to align the nose310with hole600. InFIG. 9, nose310is driven downwards until collar330is placed into contact with IML352, while collar330remains axially aligned with hole600, such that both are centered at axis900.

InFIG. 10, a fastener1000is driven through hole600and collar330, such that a pintail1010of the fastener has entered nose310. A hydraulic motor is then activated, and nose310proceeds over collar330to swage the collar330into place on fastener1000as shown inFIG. 11. This results in lip1120at collar330, and also causes pintail1010to snap off of fastener1000. A controller of the swage tool300determines a position of nose310at or before the moment that pintail1010snapped (e.g., as indicated by an actuator for nose310). Based on this position, a terminal distance (D2) of nose310to IML352is determined. If the terminal distance is less than a threshold, then the fastener has been installed as desired. InFIG. 12, swage tool300is retracted, leaving the fastener1000in place.

With a discussion provided above of an exemplary technique for fastener installation,FIG. 13illustrates a further potential embodiment of a swage tool that includes an active distancing sensor such as a laser or LIDAR sensor, andFIG. 14illustrates pressure and position measurements that may be utilized to determine whether a fastener installation has been performed successfully.

FIG. 13illustrates an inner mold line machine of a fastener installation system that includes a distancing sensor1310an illustrative embodiment. In this embodiment, a swage tool1300includes the distancing sensor1310in the form of an infrared, ultrasound, or laser distancing sensor that measures distance (D) to a splice1320. By comparing distances measured by the distancing sensor1310initially before swaging begins, and immediately before a pintail of a fastener has snapped, a controller of swage tool1300may determine whether swaging has been completed successfully for a fastener. The difference between the initial distance (e.g., D1as discussed in the prior FIGS.) and terminal distance (e.g., D2as discussed in the prior FIGS.) may be compared, and if the difference is less than a desired amount indicated in design parameters, the swaging operation may be flagged as being out-of-tolerance. In further embodiments, the swage tool1300is coupled with a sensor in the form of a load cell that detects distance by reporting when a nose of the swaging tool1300has contacted an IML of the part (i.e., by reporting that the distance between the nose and the IML is zero).

FIG. 14is a chart illustrating relationships between pressure, position, and time during fastener installation in an illustrative embodiment.FIG. 14illustrates measured positions1410, pull pressures1420, and return pressures1430for a swage tool over time. A controller of the swage tool is able to retrospectively determine whether swaging was performed in a desired manner, by reviewing pull pressure1420for a first point in time (P1) where pressure dropped precipitously before rising again (i.e., due to physical rebounding after a pintail has broken). The controller may then determine a position of a nose of the swage tool at the first point in time, or at a second point in time (P2) prior to the first point when the pressure was less than a predefined threshold (e.g., five to ten percent less than a minimum break pressure known for pintails).

In one embodiment, swage nose position is calculated by the following formula:
SwageNosePosition=ClampAxisPosition−PanelDatum+SwageToolPosition+SystemOffsetConstant  (1)

According to this formula, PanelDatum is measured as an initial distance discussed above, clamp axis is the direction shown by the arrow onFIG. 5, the SystemOffsetConstant is calculated by comparing controller measurements to direct inspection measurements for a set of holes, and SystemOffsetConstant is chosen such that it minimizes the difference between the T distance values and measured T values for the swaged collar (T is the swage nose position at the time of pintail pop or preceding the pop based on a pressure threshold). Thus, SystemOffsetConstant is a calibration factor. In one embodiment, the nose position data is filtered out during and/or after at pintail breaks. Note that this equation assumes all axes are oriented in the same direction for simplicity.

EXAMPLES

In the following examples, additional processes, systems, and methods are described in the context of a fastener installation system.

Referring more particularly to the drawings, embodiments of the disclosure may be described in the context of aircraft manufacturing and service in method1500as shown inFIG. 15and an aircraft1502as shown inFIG. 16. During pre-production, method1500may include specification and design1504of the aircraft1502and material procurement1506. During production, component and subassembly manufacturing1508and system integration1510of the aircraft1502takes place. Thereafter, the aircraft1502may go through certification and delivery1512in order to be placed in service1514. While in service by a customer, the aircraft1502is scheduled for routine work in maintenance and service1516(which may also include modification, reconfiguration, refurbishment, and so on). Apparatus and methods embodied herein may be employed during any one or more suitable stages of the production and service described in method1500(e.g., specification and design1504, material procurement1506, component and subassembly manufacturing1508, system integration1510, certification and delivery1512, service1514, maintenance and service1516) and/or any suitable component of aircraft1502(e.g., airframe1518, systems1520, interior1522, propulsion system1524, electrical system1526, hydraulic system1528, environmental1530).

As shown inFIG. 16, the aircraft1502produced by method1500may include an airframe1518with a plurality of systems1520and an interior1522. Examples of systems1520include one or more of a propulsion system1524, an electrical system1526, a hydraulic system1528, and an environmental system1530. 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.

As already mentioned above, apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service described in method1500. For example, components or subassemblies corresponding to component and subassembly manufacturing1508may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft1502is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the subassembly manufacturing1508and system integration1510, for example, by substantially expediting assembly of or reducing the cost of an aircraft1502. Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft1502is in service, for example and without limitation during the maintenance and service1516. For example, the techniques and systems described herein may be used for material procurement1506, component and subassembly manufacturing1508, system integration1510, service1514, and/or maintenance and service1516, and/or may be used for airframe1518and/or interior1522. These techniques and systems may even be utilized for systems1520, including, for example, propulsion system1524, electrical system1526, hydraulic1528, and/or environmental system1530.

In one embodiment, a part comprises a portion of airframe1518, and is manufactured during component and subassembly manufacturing1508. The part may then be assembled into an aircraft in system integration1510, and then be utilized in service1514until wear renders the part unusable. Then, in maintenance and service1516, the part may be discarded and replaced with a newly manufactured part. Inventive components and methods may be utilized throughout component and subassembly manufacturing1508in order to install fasteners during the manufacture of new parts.