Patent Publication Number: US-10328411-B2

Title: Apparatuses and methods for accurate structure marking and marking-assisted structure locating

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application is a division of U.S. patent application Ser. No. 13/925,865, entitled: Apparatuses and Methods for Accurate Structure Marking and Marking-Assisted Structure Locating, filed on Jun. 25, 2013, the content of which is incorporated herein by reference in its entirety. 
    
    
     TECHNOLOGICAL FIELD 
     The present disclosure relates generally to manufacturing a product and, in particular, to manufacturing a product using markings applied thereto. 
     BACKGROUND 
     The accuracy with which automated manufacturing equipment is able to work parts depends largely on the quality of the location and orientation information used with the equipment. For example, with poor location and/or orientation information about a part, the most state of the art manufacturing equipment will only be able to work the part in a marginal manner. Conversely, with precise location and orientation information, a marginal piece of equipment may be able to perform well. 
     Automated manufacturing processes requiring a moderate amount of accuracy do not call for particular part location and orientation information beyond knowing that the part has been positioned in a standard place. For these processes, the accuracy of standard part positioning allows part working with sufficient accuracy. In these processes, for example, a part to be worked can be placed in a standard location in or near the applicable automated machine, for example by abutting a predetermined edge of the part with a predetermined edge of a work platform and the machine can be programmed to work the part in that standard location. In processes requiring only moderate accuracy, standard part placement and machine operation are precise enough to achieve desired results. 
     Automated manufacturing processes requiring a high level of accuracy call for part locating and/or orienting after the part has been positioned. Some processes require automated machinery to work parts with a very high degree of accuracy. For example, very high accuracy is required where interchangeable hole patterns are being used. Interchangeable hole patterns are those made in product parts likely to be interchanged during the life of the product. For example, while most other parts of aircraft may not require changing, it may be determined that a particular door typically requires replacement at least once during the life of the aircraft. In this example, the mating characteristics of the door and the door mounting location of the plane must lie within tighter than standard tolerances. 
     Although parts of aircraft are generally manufactured at or about the same time and often in the same plant, an aircraft and a replacement part therefor may be manufactured at different plants and far apart in time. For example, an aircraft manufacturer may outsource replacement part manufacture to a supplier. Although various manufacturing inaccuracies in a process repeatedly performed in the same place and time may cancel each other out or aggregate within acceptable limits, a part made decades later at a different location is less likely to have these benefits. For example, manufacturing inaccuracies in formation of a first part are more likely to have inaccuracies that correspond to complimentary inaccuracies made in a second part on the same machine on the same day. 
     Although many part locating and orienting processes are adequate, it is generally desirable to have an improved system and method that takes into account at least some of the issues discussed above, as well as possibly other issues. 
     BRIEF SUMMARY 
     Example implementations of the present disclosure are generally directed to a laser-marking system, working equipment and related methods for marking-assisted structure locating. In conventional machining, a structure may be brought to working equipment to work the structure. As structures grow in size, working equipment are instead more often being brought to the structure to work the structure in a selected zone or working envelope. In a fully-automated and flexible manufacturing environment, example implementations of the present disclosure may enable working equipment to align their coordinate system to that of the structure to be worked by looking at one or more markings applied to the structure (e.g., large-size structure). 
     According to one aspect of example implementations, the laser-marking system includes a laser source configured to emit a laser beam, and a steering assembly configured to steer the laser beam onto a structure to be worked. The laser-marking system also includes a computer system coupled to the laser source and steering assembly. The computer system is configured to direct operation of the laser source to emit the laser beam with one or more controllable parameters to apply a permanent marking to the structure. The computer system is also configured to direct operation of the steering assembly to steer the laser beam to a known location on the structure at which to apply the marking, with the respective location having a known relationship with a working location at which to work the structure. 
     In one example, the steering assembly may include a galvanometer coupled to a mirror configured to reflect the laser beam. The galvanometer and mirror may be controllably rotatable to steer the laser beam in a particular direction. And the steering assembly may include an optical rotary encoder coupled to the computer system and galvanometer, and configured to measure an angular position of the galvanometer. In this regard, the computer system may be configured to determine a location of the laser beam on the structure based on the measurement, and steer the laser beam to the known location based on the determined location. 
     In one example, the laser-marking system may further include a (first) camera coupled to the computer system and configured to capture an image of at least a portion of the structure and including one or more targets on or proximate the structure. Or the laser-marking system may include a laser scanner configured to measure points on a surface of the structure from which a 3D model of the structure is generatable. In this example, the computer system may be configured to process the image or 3D model to determine placement of the structure, and locate the known location at which to apply the marking based on the structure&#39;s placement. 
     In one example, the known location may be a desired location, and in at least one instance the marking may be offset from the desired location. In this example, the laser-marking system may further include a (second) camera coupled to the computer system and configured to capture an image of at least a portion of the structure and including the desired location and marking. The computer system may be configured to process the image to locate the desired location, and determine an offset of the marking from the located desired location. 
     In a further example, the (second) camera may have a field of view steerable by the steering assembly, and the computer system may be configured to direct operation of the steering assembly to steer the field of view to one or more areas within which one or more targets on or proximate the structure are located. For the area(s), the (second) camera may be configured to capture one or more images of at least a portion of the structure and including the target(s). And the computer system may be configured to process the image(s) to determine placement of the structure, and locate the known location at which to apply the marking based on the structure&#39;s placement. 
     In one example, the laser-marking system may further include a second laser source configured to project a laser image on the structure at the location before the laser beam is emitted to apply the permanent marking to the structure at the respective location. 
     In some examples, the laser-marking system may further include one or more metrology systems coupled to the computer system, and include one or more of a laser tracker, range sensor or vibration sensor. The laser tracker may be configured to project one or more steerable laser beams onto retro-reflective targets on or proximate the structure at known locations, and provide measurements of reflected one or more beams from the targets for determination of placement of the structure. The range sensor may be configured to provide range measurements between the laser-marking system and structure for calculation of an initial focus point or focal length for operation of the laser source, or dynamic adjustment of the focal length. The vibration sensor may be configured to provide measurements of vibration of the structure, or the laser-marking system including the vibration sensor disposed thereon, for compensation of vibrational movement of the structure or laser-marking system. 
     According to another aspect of example implementations, the working equipment includes a tool configured to work a structure at a working location thereon, with the structure having a marking applied thereto at a known location with a known relationship with the working location. The working equipment may include a computer system coupled to the tool and configured to determine placement of the structure, and position the tool into at least partial alignment with the working location according to the structure&#39;s placement. In at least one instance, the tool may be aligned with a second location offset from the working location. The working equipment may further include a (second) camera coupled of the computer system and configured to capture an (second) image of at least a portion of the structure and including the marking, and further including the second location with which the tool is aligned. The computer system, then, may be configured to process the image to locate the working location, reposition the tool from the second location and into greater alignment with the located working location, and control the repositioned tool to work the structure at the located working location. 
     In one example, the camera is a second camera configured to capture a second image. In this example, the working equipment may further include a first camera coupled to the computer system and configured to capture a first image of at least a portion of the structure and including one or more targets on or proximate the structure. The computer system, then, may be configured to process the first image to thereby determine the structure&#39;s placement. 
     In one example, the working equipment may further include a movable end effector assembly coupled to the computer system, and including an end effector and the tool. In this example, the camera may be secured to the end effector assembly. Also in this example, the computer system may be configured to position the end effector assembly and thereby the tool, with the camera also being thereby positioned such that a field of view of the camera encompasses the marking. 
     In one example, the (second) camera has a field of view divided into a plurality of concentric zones of increasing size about the second location with which the tool is aligned. In this example, the zones include a first zone that defines an acceptable offset, and a larger second zone located outside the first zone that defines an unacceptable offset. Also in this example, the computer system may be configured to control the tool to work the structure without repositioning in an instance in which the located working location is within the first zone, or reposition the tool before controlling the tool to work the structure in an instance in which the located working location is within the second zone. 
     In other aspects of example implementations, methods are provided for application of a marking to a structure, and locating the structure or locations thereon based on the marking. The features, functions and advantages discussed herein may be achieved independently in various example implementations or may be combined in yet other example implementations further details of which may be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
       Having thus described example implementations of the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein: 
         FIGS. 1 and 2  illustrate a system according to respective example implementations of the present disclosure; 
         FIGS. 3-6  illustrate respective arrangements of a structure-marking system relative to a structure according to various example implementations; 
         FIG. 7  illustrates a laser-marking system according to one example implementation; 
         FIG. 8  illustrates a rotary encoder according to one example implementation; 
         FIG. 9  illustrates working equipment according to one example implementation; 
         FIG. 10  illustrates a field of view of a camera according to one example implementation; 
         FIGS. 11-16  illustrate laser-marking systems according to other respective example implementations; 
         FIG. 17  illustrates an apparatus that may be configured to function as or otherwise implement one or systems, working equipment or components thereof, according to various example implementations; 
         FIGS. 18 and 19  are flowcharts illustrating various steps in methods according to various example implementations; 
         FIG. 20  is an illustration of a flow diagram of aircraft production and service methodology according to one example implementation; and 
         FIG. 21  is an illustration of a block diagram of an aircraft according to one example implementation. 
     
    
    
     DETAILED DESCRIPTION 
     Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout. 
       FIG. 1  illustrates a system  100  according to one example implementation of the present disclosure. As shown, the system  100  may include a structure-marking system  102  and working equipment  104  that operate on one or more structures  106  (e.g., aircraft parts) in one or more work spaces, such as a fabrication or manufacturing work space  108 . In some examples, the structure-marking system  102  and working equipment  104  may be separately packaged; or in other examples, the structure-marking system  102  and working equipment  104  may be co-located within an integrated package. 
     The structure-marking system  102  may be generally configured to apply one or more permanent markings  110  such as linear-measurement markings (e.g., similar to a ruler), fiducial markings or the like for accurate structure locating and/or orienting, with the marking(s) being applied to the structure  106  at respective one or more known locations  112 . For the sake of simplicity,  FIG. 1  illustrates application of one marking  110  at a respective location  112 , although more markings may be applied. Further, the marking  110  may have any of a number of different geometries, such as a circle, polygon (e.g., triangle, rectangle, square, star) and the like. 
     In one example, the structure-marking system  102  is configured to determine the location  112  on the structure  106  at which to apply the marking  110  based on a file  114  including information that defines the structure  106  and specifies the location  112 . Although termed a “file,” it should be understood that this and any other file herein may be formatted in any of a number of different manners, such as in one or more electronic files, one or more databases or the like. 
     The working equipment  104  is generally configured to work the structure  106 , and may include one or more tools  116  for working the structure  106  at one or more working locations  118  thereon (one shown for example). The structure  106  may have the marking  110  applied thereto at a known location  112  with a known relationship with the working location  118 . In some examples, the working location  118  may be coincident with or determinable from the marked location  112 . The working equipment  104  may include a computer system  120  configured to determine the location and orientation of the structure  106  to thereby determine its placement (defined by its location and orientation). The computer system  120  may then be configured to position the tool  116  into at least partial alignment with the working location  118  according to the structure&#39;s placement. In some instances, however, the positioned tool  116  may still be at least slightly misaligned with the working location  118 . That is, the tool  116  may be aligned with another (second) location  122  offset from the working location  118 . 
     In accordance with example implementations of the present disclosure, the working equipment  104  may include a camera  124  (e.g., digital camera, laser camera, infrared camera, thermal camera, depth-aware or range camera, stereo camera) configured to capture an image of at least a portion of the structure  106  and including the marking  110 . The computer system  120  may be configured to direct the camera  124  to capture the image, which in some examples may also include the other location  122  with which the tool  116  is aligned. The computer system  120  may process the image to more-precisely locate the working location  118  on the structure  106 . The computer system  120  may then reposition the tool  116  from the other location  122  and into greater alignment with the located working location  118 . The computer system  120  may then control the repositioned tool  116  to work the structure  106  at the respective location  118 . 
     The working equipment  104  may be configured to work the structure  106  in any of a number of different manners, with each instance of work to the structure generally including one or more fabrication or manufacturing operations. In some examples, the working equipment  104  may include an appropriate tool  116  for drilling a hole at the working location  118 , installing a fastener in a hole at the respective location  118 , and the like. In another example, the working equipment  104  may include an appropriate tool  116  for cutting through the structure  106  along a line that includes the working location  118 . In yet another example, the working equipment  104  may include an appropriate tool  116  for routing out a portion of the structure  106  that includes the working location  118 . 
     As shown in  FIG. 1 , the structure-marking system  102  and working equipment  104  may operate on the structure  106  in a common work space  108 .  FIG. 2  illustrates another example, however, in which each of the structure-marking system  102  and working equipment  104  may operate on the structure  106  in a respective work space  108 . As shown in  FIG. 2 , in this other example, the structure-marking system  102  may be configured to apply the marking  110  to the structure  106  in a first work space  200  (e.g., fabrication work space). The structure  106  may thereafter be transported and placed at a second work space  202  where the working equipment  104  may be configured to position its tool  116  and work the structure  106 . 
     The structure-marking system  102  and structure  106  may be arranged in any of a number of different manners to carry out the marking application. As shown in  FIG. 3 , for example, the structure-marking system  102  may be equipped on a machine tool  300  configured to machine the structure  106  from raw material  302 . Examples of suitable machine tools  300  include milling machines, lathes, drill presses and the like. In another example, as shown in  FIG. 4 , a robot may include a movable arm  400  with an end effector  402  (e.g., detachable end effector) on which the structure-marking system  102  may be equipped and moved relative to a machined structure  106 .  FIG. 5  illustrates another example in which the structure-marking system  102  may be equipped on a stationary overhead system  500  underneath which the structure  106  may be movable or otherwise carried by a movable support  502 . Conversely,  FIG. 6  illustrates an example in which the structure-marking system  102  may be equipped on a movable overhead system  600  that may be configured to move over the structure  106 , which may be stationary or otherwise carried by a stationary support  602 . 
     The structure-marking system  102  may be configured to apply a marking  110  at a location  112  on the structure  106  in accordance with any of a number of different processes. Examples of suitable processes include laser marking, chemical etching, photo etching, ink-jet printing, mechanical stamping, nameplates, casting/molding, pneumatic pin or dot-peen marker, vibratory pencil, CO 2  laser mask marking and the like.  FIG. 7  illustrates a laser-marking system  700  according to one example implementation, and which may be one example of the structure-marking system  102  of the system  100  of  FIG. 1 . As shown, the laser-marking system  700  includes a laser source  702  configured to emit a laser beam  704  through a lens assembly  706  (e.g., objective lens) and onto a structure  708  (e.g., structure  106 ). 
     The laser-marking system may include a steering assembly  710  configured to steer the laser beam  704  onto the structure  708 . As shown, for example, the steering assembly  710  may include first and second galvanometers  712 ,  714  coupled to respective first and second mirrors  716 ,  718 , such as by respective first and second galvanometer shafts  720 ,  722  of the galvanometers  712 ,  714 . The illustrated steering assembly  710  may be capable of steering the laser beam  704  in multiple directions (e.g., Cartesian x, y) within an envelope  724 . In other examples, the steering assembly  710  may include only the first galvanometer  712  and mirror  716 , or second galvanometer  714  and mirror  718 , to steer the laser beam  704  in either the x or y direction. And in some examples, the lens assembly  706  may include a dynamic focus module (DFM) to further enable steering the laser beam  704  in the z direction. 
     The laser source  702  may be coupled to a laser controller  726  configured to manage its operation. Likewise, the steering assembly  710  may include one or more galvanometer controllers  728  coupled to the galvanometers  712 ,  714  and configured to manage their operation, separately or together. As shown, the laser-marking system  700  may also include a computer system  730  coupled to the controllers 726 ,  728 . The computer system  730  may be configured to direct operation of the laser source  702  and galvanometers  712 ,  714  to steer the laser beam  704  from the laser source  702 . In some examples, the laser-marking system  700  including each of its components may be arranged together relative to the structure  708  (e.g.,  FIGS. 3-6 ). In other examples, the computer system  730  may be arranged separate from the other components, and may be configured to communicate with the other components by wire or wirelessly. 
     In operation, the computer system  730  may transmit a control signal to the laser controller  726 , which may receive the control signal and cause the laser source  702  to emit the laser beam  704  with one or more controllable parameters such as power, wavelength and the like. The laser beam  704  may be directed through the lens assembly  706  and onto the first mirror  716  reflect onto the second mirror  718 , and impinge onto the structure  708 . The computer system  730  may transmit one or more additional control signals to the galvanometer controller  728 . The galvanometer controller  728  may receive the additional control signals and controllably position the galvanometers  712 ,  714  which may, in turn, controllably position respective mirrors  716 ,  718  to steer the laser beam  704 . In one example, each galvanometer  712 ,  714  may be controlled to rotate to any position within an approximately 40° range. The laser beam  704  may thereby leave the second mirror  718  in a controlled vector direction over a desired range of angles in the x and y directions. 
     To enable the laser-marking system  700  to steer the laser beam  704  with increased precision, the first and second galvanometers  712 ,  714  may be coupled to respective first and second positional-feedback encoders  732 ,  734 , such as absolute optical rotary encoders (transmissive or reflective). The encoders  732 ,  734  may be coupled to one or more encoder controllers  736  configured to manage their operation, separately or together. The positional-feedback encoders  732 ,  734  may be configured to measure angular position of the galvanometers  712 ,  714 , or more specifically their respective shafts  720 ,  722 , and transmit the angular-position measurements to the computer system  730  via the encoder controller  736 . The computer system  730  may in turn be configured to determine the location of the laser beam  704  (e.g., Cartesian x, y coordinates) on the structure  708  based on the angular position measurements, and may steer the laser beam  704  to the known location  112  based on the determined location. In some examples, the laser-marking system  700  may include other optics (e.g., periscopes, prisms, etc.) that may facilitate directing the laser beam  704  onto the structure  704 , which may enable both line-of-sight and out-of-sight positioning of the laser beam  704 . 
       FIG. 8  illustrates a transmissive optical rotary encoder  800  according to one example implementation, and which may be one example of a positional-feedback encoder  732 ,  734  of the laser-marking system  700  of  FIG. 7 . As shown, the rotary encoder  800  includes a circular, transparent and rotatable encoder plate  802  (sometimes referred to as a disc) that has one or more code patterns  804  disposed about its periphery. The rotary encoder  800  also includes a light source  806  (e.g., light-emitting diode) and photodetector  808  aligned with one another on respective opposing sides  810   a ,  810   b  of the encoder plate  802 , both of which remain stationary in relation to rotation of the encoder plate  802 . The light source  806  may be configured to emit a light beam  811  onto the encoder plate  802  directly or, as shown, through a condenser assembly  812 . The light beam  811  may impinge on a part of the code pattern  804  aligned with the light source  806 , and an amount of the light  811  may pass through the code pattern  804 , and in turn the transparent encoder plate  802 , based on the pattern&#39;s density. The amount of light  811  that passes through the encoder plate  802  may be detected by the photodetector  808  directly or, as shown, through a stationary mask  814 . And the photodetector  808  may be configured to produce an electrical signal indicative of the magnitude of the amount of light that passed through the encoder plate  802 . 
     As also shown, the encoder plate  802  may be mounted on a rotatable shaft  816 , which may be in turn mounted to a galvanometer shaft  818  (e.g., shaft  720 ,  722 ). This may thereby provide rotation of the encoder plate  802  in concert with rotation of the galvanometer shall  818  and its mirror (e.g., mirror  716 ,  718 ) coupled thereto. As the mirror changes position, the encoder plate  802  may rotate, thereby increasing or decreasing the intensity of the light beam detected by the photodetector  808 . The code pattern  804  may be designed to indicate an absolute position of the encoder plate  802 , and the shafts  816  and  818  may be coupled to one another with their respective encoder plate  802  and mirror in a known position relative to one another. The intensity of the detected light beam  814  may thereby provide an indication of the position of the encoder plate  804 , which may in turn provide an indication of the position of the mirror coupled to the galvanometer shaft  818 . 
     Returning to  FIG. 7 , the laser source  702  may include any of a number of different types of lasers capable of producing a laser beam  704 , which is in turn capable of producing a marking  738  (e.g., marking  110 ) at location  740  (e.g., location  112 ) on the structure  708 . Examples of suitable types of lasers include gas lasers (e.g., CO lasers, CO 2  lasers, excimer lasers), solid-state lasers (e.g., Nd:YAG lasers), semiconductor lasers, fiber lasers and the like. The laser-marking system  700  may be configured to mark the structure  708  according to any of a number of different laser-marking processes, which may be varied by controlling parameters (e.g., power, wavelength) of the laser beam  704  from the laser source  702 . In some examples, suitable laser-marking processes may depend on the material of which the structure  708  is formed. Some examples of suitable materials include metals (e.g., stainless steel, aluminum, gold, silver, titanium, bronze, platinum, copper), plastics (e.g., ABS, polycarbonate, polyamide, PMMA, plastics with laser additives), coated metals, coated plastics, paints, wood, glass, fiber composites, foils, films, packaging, laminates and the like. 
     Examples of suitable laser marking processes include laser engraving, removing, staining, annealing and foaming. Laser engraving generally involves using the laser beam  704  to melt and evaporate the surface of the structure  708  to produce an impression in the surface. Removing generally involves using the laser beam  704  to remove one or more top coats applied to the surface of the structure  708 , which may produce a contrast in instances in which the top coat and structure  708  have different colors. Staining generally involves the laser beam  704  generating a heat effect that causes a chemical reaction on the surface of the structure  708 , which may result in discoloration of the surface. In accordance with various staining processes, the beam energy may be adjusted to change the surface properties of coating layer, although reflected energy may also be used for this purpose. 
     In an annealing process, the heat effect of the laser beam  704  may cause oxidation underneath the surface of the structure  708 , which may result in discoloration of the surface. The foaming process generally uses the laser beam  704  to melt the structure  708  to produce gas bubbles on its surface. The gas bubbles may diffusely reflect light to produce an area lighter in color than other areas of the surface. 
     The computer system  730  may be configured to control parameters of the laser beam  704  from the laser source  702  to apply marking(s)  738  on the structure  708  according to a desired marking process. The computer system  730  may be also configured to control the galvanometers  712 ,  714  according to a scanning pattern that may define the location(s)  740  on the structure  708  at which to apply the marking(s)  738 . The computer system  730  may be manually or automatically operated to control the galvanometers  712 ,  713 , and thereby apply the marking(s)  738 . 
     In one example, the computer system  730  may be coupled to or configured to implement an engineer station  742 , which may be arranged together with or separate from and in communication with (by wire or wirelessly) the laser-marking system  700 . The engineer station  742  may be configured to execute appropriate software such as Unigraphics, CATIA or another CAD/CAM-type application to allow a user (e.g., design engineer) to create a design master file  744  relating to the structure  708 . The design master file  744  may specify edge-of-structure information that relates to structure geometry (e.g., points, angles, lines) that defines the structure  708 . In one example, the edge-of-structure information may include for each edge of the structure  708 , a series of point objects connectable in a graph to form an image of the edge. 
     The design master file  744  may also include calibration point information from which placement of the structure  708  may be determined to enable accurate alignment of the laser beam  704  with the location  740  at which to apply the marking  738 . As explained below, this information may also enable alignment of a tool (e.g., tool  116 ) for working the structure  708 . In one example, calibration point information may provide the known locations of multiple targets on or proximate the structure  708 . In various examples, these targets may include corners, edges or other features of the structure  708 , which may be distinct from the marking  738 . 
     The design master file  744  may also specify location information for marking and working the structure  708 . The location information may identify one or more locations  740  at which to mark the structure  708 . The location information may also identify one or more working locations  746  for working the structure, such as a location for drilling a hole, installing a fastener, cutting, routing and the like. In one example, the location information may be provided by absolute coordinates (e.g., Cartesian x, y, z), or coordinates or distances relative to one or more corners, edges or other features of the structure  708  to be marked and worked. As explained above the working location  746  may be coincident with or otherwise determinable from the marking  738  at its known location  740 . Thus, in one example, the working location  746  may be provided by coordinates or distances relative to one or more markings  738 . 
     Regardless of the exact content of the design master file  744 , the engineer station  742 , the computer system  730  or another facility coupled to either or both of the engineer station  742  or computer system  730  may process and/or reformat the design master file  744  to produce one or more laser marking output files  748  (e.g., file  114 ). The laser marking output file  748  may include edge-of-structure information, calibration point information, and location information for marking the structure  708 , in a format understood by the computer system  730 . In one example, the laser marking output file  748  may also include parameters of the laser beam  704  to carry out the desired marking process. In other examples, the computer system  730  may separately receive the parameters, or the laser source  702  may be more directly configured to produce the laser beam  704  with the parameters. 
     In some examples, the laser marking output file  748  may be transferred from the engineer station  742  or other facility to the computer system  730  (downloaded or uploaded). In other examples, the design master file  744  may be transferred from the engineer station  742  to the computer system  730  (downloaded or uploaded), with the computer system  730  itself producing the laser marking output file  748  (or causing the other facility to produce the laser marking output file  748 ). Once the computer system  730  has received (or produced) the laser marking output file  748 , the computes system  730  may use the laser marking output file  742  for alignment and projection of the laser beam  704  on the structure  708  to apply the marking  738  at the location  740  thereon. 
       FIG. 9  illustrates working equipment  900  (electro-mechanical machine) according to one example implementation, and which may be one example of the working equipment  104  of the system  100  of  FIG. 1 . In one example, the working equipment  900  may be implemented a stationary or mobile robot. As shown, the working equipment  900  may include an arm  902  that has an end effector assembly  904 . The end effector assembly  904  includes an end effector  906  and a tool  908  (e.g., tool  116 ) that may be integrated with or otherwise secured to the end effector  908 . The end effector assembly  904  may be moveable (directly or via the arm  902 ) around one or more axes (x, y, z) to position the tool  908  relative to a structure  910  for working the structure  910  (e.g., structure  106 ,  708 ), which as explained above, may generally include one or more fabrication or manufacturing operations (e.g., drilling hole(s), installing fastener(s), cutting, routing). 
     The working equipment  900  may be configured to work the structure  910  at one or more working locations  912  (e.g., location  118 ,  746 ) thereon, which may be coincident with or otherwise determinable from one or more markings  914  (e.g., marking  110 ,  738 ) at respective one or more known locations  916  (e.g., location  112 ,  740 ). To enable the working equipment to position its tool  908  into alignment with the working location  912 , the working equipment  900  may also include one or more cameras, such as one or more digital cameras, laser cameras, infrared cameras, thermal cameras, depth-aware or range cameras, stereo cameras or similar devices configured to capture electronic images. As shown, for example, the working equipment  900  may include first and second cameras  918 ,  920  configured to capture respective images within respective first and second fields of view  922 ,  924 . In some examples, the first camera  918  may be in a fixed position relative to the working equipment  900 , while the second camera  920  may be secured to the end effector assembly  904 . 
     The arm  902 , end effector  906  and/or tool  908  may be coupled to one or more controllers  926  configured to manage their operation. The working equipment  900  may also include a computer system  928  (e.g., computer system  120 ) coupled to the controller  926 , as well as the cameras  918 ,  920 . The computer system  928  may be configured to direct the cameras  918 ,  920  to capture and provide images of the structure  910 . The computer system  928  may be configured to process the images to determine placement (location and orientation) of the structure  910  and locate, the working location  912  at which to work the structure  910 . The computer system  928  may also be configured to direct the controller  926  to position the tool  908  into alignment with the working location  912  based on the placement of the structure  910  and the working location  912 . And the computer system  928  may direct controller  926  to in turn control the tool  908  to work the structure  910  at the location  912 . The same or a similar positioning and working process may then repeat for any other working locations  912 . 
     According to various more particular examples, the computer system  928  may transmit a control signal to the first camera  918 , which may receive the control signal and capture a first image of the structure  910  covering the first field of view  922  within which one or more targets may be located. As suggested above, examples of suitable targets include corners  930 , edges  932  or other features of the structure  910 . The first camera  918  may transmit the first image to the computer system  928 , which may process the first image to determine the placement of the structure  914 ). 
     In some examples, the computer system  928  may be coupled to or configured to implement an engineer station  934  the same as or similar to engineer station  742 . Similar to engineer station  742 , the engineer station  934  may be arranged together with or separate from and in communication with (by wire or wirelessly) the working equipment  900 . Also similar to engineer station  742 , the engineering station  934  may be used to create a master design file  936  the same as or similar to master design file  744 . As explained above, the master design file  936  may specify edge-of-structure information that relates to structure geometry, and include calibration point information with the known locations of the targets  930 ,  932 . In one example, then, the computer system  928  may process the first image using the master design file  936 . 
     In one example, the working equipment  900  may include a laser scanner  938  (e.g., 3D scanner) in addition to or in lieu of the first camera  918 . In this example, the laser scanner  926  may function similar to the first camera  918  to enable the computer system  928  to determine the placement of the structure  910 . The laser scanner  938  may be configured to scan the structure  910  and provide measurements of points on the surface of the structure  910 . The laser scanner  938  may transmit the measurements to the computer system  928 , which may process the measurements generate a point cloud or other 3D model of the structure  910 . The computer system  928  may then process the 3D model to determine the placement of the structure  910 . And similar to before, in one example, the computer system  928  may process the measurements or 3D model using the master design file  936 . 
     As also explained above, the master design file  936  may also specify location information that identifies the working location  912 . In one example, the computer system  928  may transmit an additional control signal to the controller  926  to position the tool  908  based on the placement of the structure  910  and the working location  912 . In this regard, the controller  926  may receive the control signal and controllably position the end effector assembly  904  to thereby controllably position the tool  908  into at least partial alignment with the location  912 . In some instances, however, the positioned tool  908  may still be at least slightly misaligned with the working location  912 . That is, the tool  908  may be aligned with another location  940  (e.g., location  122 ) offset from the working location  912 . 
     According to example implementations, the second camera  920  (e.g., camera  124 ) may enable repositioning of the tool  908  to move its alignment with the other location  940  to the working location  912  (or closer thereto). In some examples, the computer system  928  may transmit a control signal to the second camera  920 , which may receive the control signal and capture a second image of the structure  910  covering the second field of view  924  within which the marking  914  may be located, and which may also include the other location  940 . The second image may thereby include the marking  914 , In one example in which the second camera  920  may be secured to the end effector assembly  904 , the second field of view  924  may be smaller than the first field of view  922 . In this example, the tool  908  being positioned into even its misalignment with the working location  912  may also position the second camera  920  so that its field of view  924  encompasses the marking  914 . The second camera  920  may transmit the second image to the computer system  928 , which may process the second image to more precisely locate the working location  912  on the structure  910 . In one example, the geometry of the marking  914  may indicate the manner of working the structure  910 , and in this example, the computer system  928  may further process the second image to determine the respective manner of working the structure  910 . In some examples, the location information of the master design file  936  may further identify the location  916  of the marking  914 , in addition to the working location  912 . In these examples, the computer system  928  may process the second image again using the master design file  936 . 
     After locating the working location  912 , the computer system  928  may transmit a further control signal to the controller  926  to reposition the tool  908  based on the located working location  912 . Similar to before, the controller  926  may receive the control signal and controllably position the arm  902  and/or end effector assembly  904  to thereby controllably position the tool  908  into increased alignment with the location  912 . In the same or yet other control signals, the computer system  928  may also direct the controller  926  to in turn control the tool  908  to work the structure  910  at the location  912 . In some examples, the controller  926  may be directed to control the tool  908  to work the structure  910  according to the manner indicated by the geometry of the marking  914 . The same or a similar positioning and working process may then repeat for any other working locations  912 . 
     In some examples, the computer system  928  may be configured to reposition the tool  908  in instances in which the offset from its aligned location  940  to the working location  912  is greater than a predetermined threshold.  FIG. 10  illustrates the field of view  924  of the second camera  920 , and including the location  940  with which the tool  908  is aligned instead of the working location  912 . The field of view  924  may be divided into a plurality of concentric zones of increasing size about the aligned location  940 , including in one example a first zone  1000 , a larger second zone  1002  located outside the first zone  1000 , and an even larger third zone  1004  located outside the second zone  1002 . The zones may be sized according to desirable thresholds for an acceptable offset or unacceptable offset of the aligned location  940  from the working location  912 . For example, the first zone  1000  may define an acceptable offset, and the second and third zones  1002 ,  1004  may define an unacceptable offset. 
     In an instance in which the working location  912  is within the first zone  1000 , the working equipment  900  may control the tool  908  to work the structure  910  without repositioning. The working equipment  900  may instead reposition the tool  908  before working the structure  910  in instances in which the working location  914  is within the second and/or third zones  1002 ,  1004 . In one more particular example, the working equipment  900  may reposition the tool  908  in an instance in which the working location  912  is within the second zone  1002 . In an instance in which the working location is within the third zone  1004 , the working equipment  900  may produce a visual and/or audible error notification to an operator, in addition to or in lieu of repositioning the tool  908 . 
     As shown and described with respect to  FIG. 9 , the working equipment  900  may include cameras  918  and  920  for placing the structure  910  and positioning/repositioning the tool  908  into alignment with the working location  912  of the structure  910 . In some examples, the laser-marking system  700  may further include one or more cameras that may enable the laser-marking system  700  to similarly place the structure  708 , and may further enable the laser-marking system  700  to inspect one or more marks  738  applied at respective one or more locations  740 .  FIG. 11  illustrates one example of a laser-marking system  1100  similar to that of  FIG. 7  but further including first and second cameras  1102 ,  1104  coupled to the computer system  730  and configured to capture respective images within respective first and second fields of view  1106 ,  1108 . In some examples, the first field of view  1104  may be fixed, while the second field of view  1106  may be steerable. In the illustrated example, the second camera  1104  may be positioned with its field of view  1108  directed to an optical filter  1110  in line with the laser beam  704 . The optical filter  1110  may be configured to pass the laser beam  704 , and reflect light to the second camera  1104 . In this example, the second field of view  1108  may be steerable by the steering assembly  710  in a manner similar to the laser beam  704 . 
     In a manner similar to that described above with respect to  FIG. 9 , the computer system  730  may be configured to direct the first camera  1102  to capture and provide a first image of the structure  708  including one or more targets such as corners  1112 , edges  1114  or other features of the structure  708 . Similar to the working equipment  900 , in one example, the laser-marking system  1100  may include a laser scanner  1116  (e.g., 3D scanner) in addition to or in lieu of the first camera  1102 . Similar to laser scanner  938 , laser scanner  1116  may be configured to scan the structure  708  and provide measurements of points on the surface of the structure  708 , from which the computer system  730  may generate a point cloud or other 3D model of the structure  708 . The computer system  730  may process the first image or 3D model to determine placement (location and orientation) of the structure  708 . 
     The computer system  730  may locate the location  740  at which to apply the marking  738  based on the structure&#39;s placement, and direct the steering assembly  710  to position the laser beam  704  into alignment with the respective location  740 . And the computer system  730  may direct the laser controller  726  to in turn control the laser source  702  to produce the laser beam  704  to apply the marking  738  at the location  740 . The same or a similar positioning and marking process may then repeat for any other markings  738 . 
     As or after the laser-marking system  1100  applies a marking  738 , the laser-marking system  1100  may use the second camera  1104  to inspect the applied marking  738 , such as for its proper geometry, location and the like. In some examples, the marking  738  may be applied at another location (cf. location  940 ) offset from its desired location  740  (cf. working location  912 ). In a manner similar to that described above with respect to  FIG. 9 , then, the computer system  730  may be configured to direct the second camera  1004  to capture and provide a second image that may include the desired location  704 , and the marking applied at the other location. The computer system  730  may be configured to process the second image to precisely locate the desired location  740  on the structure  708 , and determine any offset of the marking  738  from the located desired location  740 . In some examples, an offset within a predetermined threshold (e.g., within a first zone  1000 ) may be considered acceptable, while the computer system  730  may produce a visual and/or audible error notification to an operator in instances in which the offset is greater than the predetermined threshold (e.g., within second or third zones  1002 ,  1004 ). 
     In other examples, a camera similar to the second camera  1104  may be used not only for inspecting an applied marking  738 , but for placing the structure  708 .  FIG. 12  illustrates an example laser-marking system  1200  according to another example implementation. The laser-marking system  1200  of  FIG. 12  is similar to the system  1100  of  FIG. 11 , but including a single camera  1202  with a steerable field of view  1204 . In this example, the computer system  730  may direct the steering assembly  710  to steer the camera&#39;s field of view  1204  to one or more areas within which one or more targets may be located. Similar to above, examples of suitable targets include corners  1112 , edges  1114  or other features of the structure  708 . The computer system may direct the camera  1202  to capture an image of the structure  708  at each area, from which the computer system may place the structure  708 , such as in a manner similar to that described above but with a first image. The same camera  1202  may then be used during or after markings  738  are applied to the structure. 
     In some examples, the laser-marking system  700 ,  1100 ,  1200  may further project a temporary laser image at the location  740  on the structure  708  before application of the mark  738 , which may facilitate a visual inspection of the placement of the marking  738  before it&#39;s applied.  FIG. 13  illustrates an example laser-marking system  1300  that may correspond to any of the aforementioned implementations of the laser-marking system  700 ,  1100 ,  1200 —but shown without appropriate camera(s)  1102 ,  1104 ,  1202  or optical filter  1110 . As shown, the laser-marking system  1300  may include a second laser source  1302  configured to project a laser image  1304  directed to an optical filter  1306  (the same or different from optical filter  1110 ) in line with the laser beam  704 . This optical filter  1306  may be configured to pass the laser beam  704 , and reflect laser image  1304 . The laser image  1304  may be steerable by the steering assembly  710  in a manner similar to the laser beam  704 . That is, the laser image  1304  may be steered by the steering assembly  710  in multiple directions within an envelope  1306 , which may coincide with envelope  724 . In this example, the laser image  1304  may be steered to location  740  before the laser beam  704 , and may thereby provide a visual indication of the location  740  before the marking  738  is applied. 
     In some examples, the laser-marking system  700 ,  1100 ,  1200 ,  1300  may further include one or more metrology systems such as laser trackers, range sensors, vibration sensors and the like, which may further facilitate placement of the structure  708  and/or marking  738 .  FIG. 14  illustrates an example laser-marking system  1400  that may correspond to any of the aforementioned implementations of the laser-marking system  700 ,  1100 ,  1200 ,  1300  but shown without appropriate camera(s)  1102 ,  1104 ,  1202 , optical filter  1110  or laser source  1302 . As shown, the laser-marking system  1400  may include one or more laser trackers  1402  configured to project one or more steerable laser beams  1404  onto retro-reflective targets  1406  (distinct from markings  738 ) on or proximate the structure  708  at known locations. The targets  1406  may reflect the beam(s) back to the laser tracker(s)  1402 , which may measure the reflected beam(s) and provide the measurements to the computer system  928 . The computer system  928  may process the measurements from the laser tracker(s)  1402  to determine placement of the structure  708 . Laser tracker(s)  1402  may provide very accurate measurements from which accurate placement of the structure  708  may be determined. Examples including laser tracker(s)  1402  may be particularly beneficial where highly-accurate marking is desirable such as on large and/or irregular structures  708 . 
       FIG. 15  illustrates an example laser--marking system  1500  that may correspond to any of the aforementioned implementations of the laser-marking system  700 ,  1100 ,  1200 ,  1300 ,  1400  but shown without appropriate camera(s)  1102 ,  1104 ,  1202 , optical filter  1110 , laser source  1302  or laser tracker  1404 . As shown, the laser-marking system  1500  may include one or more range sensors  1502  configured to provide range measurements between the laser-marking system  1500  and the structure  708 , or more particularly the between the range sensor(s) and the structure  708 . Examples of suitable range sensors include laser rangefinders, LiDAR (Light Detection and Ranging) sensors, sonar sensors, camera or other visual sensors, or the like. For straight and flat structures, range sensor(s)  1502  may be useful to calculate an initial laser focus point or focal length for operation of the laser source  702 . Range sensor(s)  1502  may also be useful to dynamically adjust the focal length as the laser-marking system  1500  applies markings  738  at various points on an uneven structure  708 . 
       FIG. 16  illustrates an example laser-marking system  1600  that may correspond to any of the aforementioned implementations of the laser-marking system  700 ,  1100 ,  1200 ,  1300 ,  1400 ,  1500 —but shown without appropriate camera(s)  1102 ,  1104 ,  1202 , optical filter  1110 , laser source  1302 , laser tracker  1404  or range sensor  1502 . As shown, the laser-marking system  1600  may include one or more vibration sensors  1602  configured to provide measurements of vibration of the structure  708 , or the laser-marking system  1600  including the vibration sensor(s)  1602  disposed thereon. Examples of suitable vibration sensors include any of a number of different types of vibrometers, laser Doppler vibrometers (LDVs) or the like. Vibration sensor(s)  1602  may be useful to compensate for any vibrational movement of the structure  708  and/or laser-marking system  1600 , which may facilitate accurate application of markings  738 . 
     According to example implementations of the present disclosure, the system  100  including its structure-marking system  102  and working equipment  104  may be implemented by various means. Similarly, the examples of a laser-marking system  700 ,  1100 ,  1200 ,  1300 ,  1400 ,  1500 ,  1600  and working equipment  900  including each of their respective components, may be implemented by various means according to example implementations. Means for implementing the systems  100 ,  700 ,  1100 ,  1200 ,  1300 ,  1400 ,  1500 ,  1600  and working equipment  900  and their respective components may include hardware, alone or under direction of one or more computer program code instructions, program instructions or executable computer-readable program code instructions from a computer-readable storage medium. 
     In one example, one or more apparatuses may be provided that are configured to function as or otherwise implement one or more of the controllers  726 ,  728 ,  736 , computer system  730  and/or engineer station  742  of the any of the example laser-marking systems  700 ,  1100 ,  1200 ,  1300 ,  1400 ,  1500 ,  1600 . Similarly, one or more apparatuses may be provided that are configured to function as or otherwise implement one or more of the controller  926 , computer system  928  and/or engineer station  934  of the example working equipment  900 . In examples involving more than one apparatus, the respective apparatuses may be connected to or otherwise in communication with one another in a number of different manners, such as directly or indirectly via a wire or wireles sly. 
     Reference is now made to  FIG. 17 , which illustrates an example apparatus  1700  that may be configured to function as or otherwise implement one or more of the aforementioned components of the any of the example laser-marking systems  700 ,  1100 ,  1200 ,  1300 ,  1400 ,  1500 ,  1600 , and/or one or more of the aforementioned components of the example working equipment  900 . Generally, the apparatus  1700  of example implementations of the present disclosure may comprise, include or be embodied in one or more fixed or portable electronic devices. The apparatus  1700  may include one or more of each of a number of components such as, for example, a processor  1702  connected to a memory  1704 . 
     The processor  1702  is generally any piece of computer hardware that is capable of processing information such as, for example, data, computer-readable program code, instructions or the like (generally “computer programs,” e.g., software, firmware, etc.), and/or other suitable electronic information. The processor is composed of a collection of electronic circuits some of which may be packaged as an integrated circuit or multiple interconnected integrated circuits (an integrated circuit at times more commonly referred to as a “chip”). The processor  1702  may be configured to execute computer programs, which may be stored onboard the processor  1702  or otherwise stored in the memory  1704  (of the same or another apparatus  1700 ). 
     The processor  1702  may be a number of processors, a multi-processor core or some other type of processor, depending on the particular implementation. Further, the processor  1702  may be implemented using a number of heterogeneous processor apparatuses in which a main processor is present with one or more secondary processors on a single chip. As another illustrative example, the processor  1702  may be a symmetric multi-processor apparatus containing multiple processors of the same type. In yet another example, the processor  1702  may be embodied as or otherwise include one or more application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs) or the like. Thus, although the processor  1702  may be capable of executing a computer program to perform one or more functions, the processor  1702  of various examples may be capable of performing one or more functions without the aid of a computer program. 
     The memory  1704  is generally any piece of computer hardware that is capable of storing information such as, for example, data, computer programs and/or other suitable information either on a temporary basis and/or a permanent basis. In one example, the memory  1704  may be configured to store various information in one or more databases. The memory  1704  may include volatile and/or non-volatile memory, and may be fixed or removable. Examples of suitable memory  1704  include random access memory (RAM), read-only memory (ROM), a hard drive, a flash memory, a thumb drive, a removable computer diskette, an optical disk, a magnetic tape or some combination of the above. Optical disks may include compact disk-read only memory (CD-ROM), compact disk-read/write (CD-R/W), DVD or the like. In various instances, the memory  1704  may be referred to as a computer-readable storage medium which, as a non-transitory device capable of storing information, may be distinguishable from computer-readable transmission media such as electronic transitory signals capable of carrying information from one location to another. Computer-readable medium as described herein may generally refer to a computer-readable storage medium or computer-readable transmission medium. 
     In addition to the memory  1704 , the processor  1702  may also but need not be connected to one or more interfaces for displaying, transmitting and/or receiving information. The interfaces may include one or more communications interfaces  1706  and/or one or more user interfaces. The communications interface  1706  may be configured to transmit and/or receive information, such as to and/or from other apparatus(es), network(s) or the like. The communications interface  1706  may be configured to transmit and/or receive information by physical (by wire) and/or wireless communications links. Examples of suitable communication interfaces include a network interface controller (NIC), wireless NIC (WNIC) or the like. 
     The user interfaces may include a display  1708  and/or one or more user input interfaces  1710 . The display  1708  may be configured to present or otherwise display information to a user, suitable examples of which include a liquid crystal display (LCD), light-emitting diode display (LED), plasma display panel (PDP) or the like. The user input interfaces  1710  may be by wire or wireless, and may be configured to receive information from a user into the apparatus  1700 , such as for processing, storage and/or display. Suitable examples of user input interfaces  1710  include a microphone, image or video capture device, keyboard or keypad, joystick, touch-sensitive surface (separate from or integrated into a touchscreen), biometric sensor or the like. The user interfaces may further include one or more interfaces for communicating with peripherals such as printers, scanners or the like. 
     As indicated above, program code instructions may be stored in memory, and executed by a processor, to implement functions of the system, apparatuses and their respective elements described herein. As will be appreciated, any suitable program code instructions may be loaded onto a computer or other programmable apparatus from a computer-readable storage medium to produce a particular machine, such that the particular machine becomes a means for implementing the functions specified herein. These program code instructions may also be stored in a computer-readable storage medium that can direct a computer, a processor or other programmable apparatus to function in a particular manner to thereby generate a particular machine or particular article of manufacture. The instructions stored in the computer-readable storage medium may produce an article of manufacture, where the article of manufacture becomes a means for implementing functions described herein. The program code instructions may be retrieved from a computer-readable storage medium and loaded into a computer, processor or other programmable apparatus to configure the computer, processor or other programmable apparatus to execute operations to be performed on or by the computer, processor or other programmable apparatus. 
     Retrieval, loading and execution of the program code instructions may be performed sequentially such that one instruction is retrieved, loaded and executed at a time. In some example implementations, retrieval, loading and/or execution may be performed in parallel such that multiple instructions are retrieved, loaded, and/or executed together. Execution of the program code instructions may produce a computer-implemented process such that the instructions executed by the computer, processor or other programmable apparatus provide operations for implementing functions described herein. 
     Execution of instructions by a processor, or storage of instructions in a computer-readable storage medium, supports combinations of operations for performing the specified functions. It will also be understood that one or more functions, and combinations of functions, may be implemented by special purpose hardware-based computer systems and/or processors which perform the specified functions, or combinations of special purpose hardware and program code instructions. 
       FIG. 18  illustrates various steps in a method  1800  according to example implementations of the present disclosure. The method  1800  may include capturing an image of at least a portion of a structure  708  to be worked, and including one or more targets  1112 ,  1114  on or proximate the structure  708 , as shown in block  1802 . Or in another example, the method may include measuring points on a surface of the structure from which a 3D model of the structure is generatable. The method  1800  may also include processing the image or 3D model to determine placement of the structure  708 , and locating a known location  740  at which to apply a permanent marking  738  based on the structure&#39;s placement, as shown in block  1804 . In one example, the method  1800  may include projecting a laser image  1304  on the structure  708  at the location  740 , as shown in block  1806 . 
     The method  1800  may include directing operation of a steering assembly  710  to steer a laser beam  704  to the known location  740  on the structure  708  at which to apply the marking  738 , as shown in block  1808 . The respective location  740  may have a known relationship with a working location  746  at which to work the structure  708 . The method  1800  may include directing operation of a laser source  702  to emit the laser beam  704  onto the structure  708 , as shown in block  1810 . The laser beam  704  may be emitted with one or more controllable parameters to apply the permanent marking  738  to the structure  708 . 
     In one example, directing operation of the steering assembly  710  may include controllably rotating a galvanometer  712 ,  714  coupled to a mirror  716 ,  718  configured to reflect the laser beam  704 , with the galvanometer  712 ,  714  and mirror  716 ,  718  being controllably rotated to steer the laser beam  704  in a particular direction (e.g, x, y). In this example, an angular position of the galvanometer  712 ,  714  may be measured by an optical rotary encoder  732 ,  734  coupled to the galvanometer  712 ,  714 . And a location of the laser beam  704  on the structure  708  may be determined based on the measurement, and the laser beam  704  may be steered to the known location  740  based on the determined location. 
     In one example, the known location  740  is a desired location, and in at least one instance the marking  738  is offset from the desired location  740 . In this example, the method  1800  may further include capturing an image of at least a portion of the structure  708  and including the desired location  740  and marking  738 , as shown in block  1812 . The image may be processed to locate the desired location  740 , and the offset of the marking  738  from the located desired location  740  may be determined, as shown in block  1814 . This may enable inspection of the marking  738  applied to the structure  708 . 
     In a further example, the image may be captured by a camera  1202  having a field of view  1204  steerable by the steering assembly  710 . In this example, the method  1800  may further include directing operation of the steering assembly  710  to steer the field of view  1204  to one or more areas within which one or more targets  1112 ,  1114  on or proximate the structure  708  are located. Also in this example, the method  1800  may include capturing for the one or more areas, one or more images of at least a portion of the structure  708  and including the target(s)  1112 ,  1114 . The image(s) may then be processed to determine placement of the structure  708 , and the known location  740  at which to apply the marking  738  may be located based on the structure&#39;s placement. 
     This process may then repeat to apply the marking  738  at any other desirable locations  740 , as shown in block  1816 . 
       FIG. 19  illustrates various steps in a method  1900  according to other example implementations of the present disclosure. The method  1900  may include determining placement of a structure  910  having a marking  914  applied thereto at a known location  916  with a known relationship with a working location  912  thereon, as shown in block  1902 . The method  1900  may include positioning a tool  908  into at least partial alignment with the working location  912  according to the structure&#39;s placement, as shown in block  1904 . In at least one instance, however, the tool  908  may be aligned with another location  940  offset from the working location  912 . The method  1900  may also include capturing an image of at least a portion of the structure  910  and including the marking  914 , and further including the other location  940  with which the tool  908  is aligned, as shown in block  1906 . 
     In one example, the image is a second image captured by a second camera  920 . In this example, determining the structure&#39;s placement may include capturing by a first camera  918 , a first image of at least a portion of the structure  910  and including one or more targets  930 ,  932  on or proximate the structure  910 . The first image may then be processed to thereby determine the structure&#39;s placement. 
     In one example, a movable end effector assembly  904  may include an end effector  906  and the tool  908 , the image may be captured by a camera  920  secured to the end effector assembly  904 . In this example, positioning the tool  908  may include positioning the end effector assembly  904  and thereby the tool  908 , with the camera  920  also being thereby positioned such that a field of view  924  of the camera  920  encompasses the marking  914 . 
     The method  1900  may further include processing the (second) image to locate the working location  912 , as shown in block  1908 . The method may then at times include repositioning the tool  908  from the other location  940  and into greater alignment with the located working location  912 , and controlling the repositioned tool  908  to work the structure  910  at the located working location  912 . In one example in which the image is captured by a camera  920 , its field of view  924  may be divided into a plurality of concentric zones of increasing size about the other location  940  with which the tool  908  is aligned. The zones may include a first zone  1000  that defines an acceptable offset, and a larger second zone  1002  located outside the first zone  1000  that defines an unacceptable offset. Repositioning the tool  908  and controlling the repositioned tool  908  to work the structure  910 , then, may include repositioning the tool  908  before controlling the tool  908  to work the structure  910  in an instance in which the located working location is within the second zone, as shown in blocks  1910  and  1912 . Or controlling the tool  908  to work the structure  910  without repositioning in an instance in which the located working location  912  is within the first zone  1000 , as in block  1912 . 
     This process may then repeat to work other working locations  912  on the structure  910 , such as using the same or other images including the same or other markings  914 , as shown in block  1914 . 
     Implementations of the disclosure may find use in a variety of potential applications, particularly in the transportation industry, including for example, aerospace, marine and automotive applications. Thus, referring now to  FIGS. 20 and 21 , example implementations may be used in the context of an aircraft manufacturing and service method  2000  as shown in  FIG. 20 , and an aircraft  2100  as shown in  FIG. 21 . During pre-production, the example method may include specification and design  2002  of the aircraft  2100 , manufacturing sequence and processing planning  2004  and material procurement  2006 . The disclosed method may be specified for use, for example, during material procurement  2006 . 
     During production of the aircraft  2100 , component and subassembly manufacturing  2008  and system integration  2010  takes place. The disclosed system and method may be used to mark structures and/or work marked structures of the aircraft  2100  either or both of the component and subassembly manufacturing process  2008  or system integration  2010 . Thereafter, the aircraft  2100  may go through certification and delivery  2012  in order to be placed in service  2014 . While in service  2014  by a customer, the aircraft  2100  may be scheduled for routine maintenance and service  2016  (which may also include modification, reconfiguration, refurbishment or the like). Structures of the aircraft  2100  may be marked and/or worked according to the disclosed method while in service  2014 , and in one example, during the maintenance and service  2016 . 
     Each of the processes of the example method  2000  may be performed or carried out by a system integrator, third party and/or operator (e.g., customer). For the purposes of this description, a system integrator may include for example any number of aircraft manufacturers and major-system subcontractors; a third party may include for example any number of vendors, subcontractors and suppliers; and an operator may include for example an airline, leasing company, military entity, service organization or the like. 
     As shown in  FIG. 21 , an example aircraft  2100  produced by the example method  2000  may include an airframe  2102  with a plurality of systems  2104  and an interior  2106 . Structures marked and/or worked according to the disclosed method and system may be used in the airframe  2102  and within the interior. Examples of high-level systems  2104  include one or more of a propulsion system  2108 , electrical system  2110 , hydraulic system  2112 , environmental system  2114  or the like. Any number of other systems  2104  may be included. Although an aerospace example is shown, the principles of the disclosure may be applied to other industries, such as the marine and automotive industries. 
     Systems, apparatuses and methods embodied herein may be employed during any one or more of the stages of the example production and service method  2000 . For example, components or subassemblies corresponding to production process  2008  may be marked and/or worked according to the disclosed method while the aircraft  2100  is in service  2014 . Also, one or more example system implementations, apparatus implementations, method implementations or a combination thereof may be utilized to mark structures and/or work marked structures during the production stages  2008  and  2010 , which may substantially expedite assembly of or reduce the cost of an aircraft  2100 . Similarly, one or more of system implementations, apparatus implementations, method implementations or a combination thereof may be utilized while the aircraft  2100  is in service  2014 , for example. 
     Many modifications and other implementations of the disclosure set forth herein will come to mind to one skilled in the art to which these disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the disclosure are not to be limited to the specific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Moreover, although the foregoing descriptions and the associated drawings describe example implementations in the context of certain example combinations of elements and/or functions, it should be appreciated that different combinations of elements and/or functions may be provided by alternative implementations without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and/or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.