Abstract:
A Z-form position detector useful for ascertaining the position of Z-forms with respect to underlying composite structure. The device comprises an oscillating laser that generates a line projected onto the Z-form and composite structure at an angle. The line appears discontinuous due to the topography of the Z-form and composite structure. For example, the line is discontinuous at the edges of the Z-form. The device further comprises a sensor sensitive to the frequency of the laser. The sensor scans along the line until a discontinuity (i.e., a break in the line) is detected. Since the discontinuity corresponds to the edge of the Z-form, detection of the discontinuity allows the device to ascertain precise coordinates of a point on the edge of the Z-form. The device thus allows Z-pins to be driven into composite structure automatically for savings on time and cost.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    (Not Applicable) 
     
    
     
       STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT  
         [0002]    (Not Applicable)  
         BACKGROUND OF THE INVENTION  
         [0003]    The following generally relates to positioning systems, and more specifically relates to optical systems used to automatically locate Z-forms with precision for reinforcement of composite structures.  
           [0004]    Manufacturers utilize composite materials in a wide variety of applications. The relatively high strength-to-weight ratio, stiffness-to-weight ratio, and fatigue characteristics of composites have made the material increasingly popular with aerospace, automotive, and other industries.  
           [0005]    To join individual composite parts, manufacturers often use conventional fasteners; however, the use of conventional fasteners typically requires access to both sides of the assembly, and such access can be limited. In these cases, manufacturers usually employ alternative attachment means. For example, the composite parts can be adhesively joined or co-bonded, but these methods often result in an inadequate bond. For a more secure bond, manufacturers insert reinforcing pins, commonly called “Zpins,” through the parts normal to the bondline. As such, the Z-pins bear a portion of the loading that might otherwise damage the bondline.  
           [0006]    Manufacturers typically insert Z-pins with largely non-automated processes. For example, multiple Z-pins held within a foam carrier (collectively referred to as a “Z-form”) are manually positioned on a target area of the composite part. Then, an insertion tool is manually located over the Z-form, after which the inserting tool utilizes ultrasonic energy to force the Z-pins out of the Z-form and into the target area of the composite. However, manufacturers desire a more automated process so that the Z-pinning process can be employed in high yield production faster and cheaper.  
           [0007]    U.S. Pat. No. 5,832,594 to Avila and U.S. Pat. No. 5,919,413 to Avila both disclose a hydraulic Z-pin insertion tool and a method of using the same. As described in these patents, Z-forms are loaded into the tool, which is then positioned over an area of composite to be pinned, and an actuator within the tool drives the pins into the composite. Thus, the tool and insertion method disclosed in the Avila patents allow Z-pins to be inserted automatically, and production costs are partially reduced as result. However, portions of the Z-form can become jammed within the tool as the insertion process takes place. Once jammed, manual labor is required to clear the jam, thereby increasing manufacturing time. As a result, the cost savings resulting from the automated process are less significant or, in some cases, eliminated.  
           [0008]    Thus, there remains a need among composite manufacturers for an improved automated Z-pinning process. Ideally, the automated process would involve pre-positioning the Z-form on the composite target area, separate from the insertion tool, because there is less chance for the insertion tool to become jammed. In order to achieve proper pinning in this manner, the insertion tool should be located according to the position of the Z-form with a high degree of precision (e.g., approximately +/−0.025 inches). However, manual positioning of the composites, tool, and Z-form typically results in a cumulative error of approximately +/−0.25 inches.  
           [0009]    Therefore, it is understood that there is an ongoing need for an apparatus that enables a Z-pin insertion tool to be located with precision relative to a Z-form. Such a tool and its method of use would allow for a more efficient automated manufacturing process and advantageously reduce manufacturing time and costs.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    In response to the aforementioned needs, there is disclosed a Z-form position detector, comprising a light-emitter capable of projecting a light beam onto a Z-form that is positioned adjacent to a composite structure. From a viewpoint looking at the composite structure, the light beam has at least one discontinuity that corresponds with an edge of the Z-form.  
           [0011]    The Z-form position detector further comprises a sensor positioned adjacent to the Z-form. The sensor is capable of detecting the at least one discontinuity and is further capable of correlating the detection of the at least one discontinuity to the approximate position of a point on the edge of the Z-form.  
           [0012]    Also disclosed is a method of detecting a position of a Z-form before insertion of Z-pins into a composite structure. First the method comprises positioning the Z-form over the composite structure. Then, a laser line is projected over the Z-form, wherein the laser line forms at least one discontinuity corresponding to an edge of the Z-form. Next, a sensor is positioned adjacent to the laser line, and the sensor is capable of detecting the at least one discontinuity and translating the detection into positional information pertaining to one point on the edge of the Z-form. Subsequently, the laser line is projected over the Z-form at a different location such that at least one discontinuity is formed corresponding to an edge of the Z-form. Then, the sensor detects the at least one discontinuity and translates the detection into positional information pertaining to another point on the edge of the Z-form. Finally, the two points of positional information are extrapolated into positional information pertaining to the entire edge of the Z-form.  
           [0013]    Both the Z-form location detector and the method of using the same allow the precise locations of Z-forms to be ascertained automatically. Obtaining these precise positional coordinates is advantageously quicker than manually determining the precise location of the Z-forms. Also, the present invention allows for automatic insertion of reinforcing Z-pins into composite structures. Thus, the automation described herein saves time and money in the manufacturing of composite structures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    These as well as other features of the present invention will become more apparent upon reference to the drawings wherein:  
         [0015]    [0015]FIG. 1 is a plan view of a Z-form;  
         [0016]    [0016]FIG. 2 is a cross sectional view of the Z-form illustrated in FIG. 1;  
         [0017]    [0017]FIG. 3A is a perspective view of one embodiment of a Z-form position detector;  
         [0018]    [0018]FIG. 3B is a side view of the Z-form position detector taken from FIG. 3A;  
         [0019]    [0019]FIG. 4 is a top view of one embodiment of the Z-form position detector of FIG. 3;  
         [0020]    [0020]FIG. 5 is a flow chart illustrating a method of utilizing the Z-form position detector; and  
         [0021]    [0021]FIG. 6 is a top view of an alternative embodiment of the Z-form position detector of FIG. 3. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    Referring now to the drawings wherein the showings are for purposes of illustrating preferred embodiments of the present invention only, and not for purposes of limiting the same, FIG. 1 and FIG. 2 illustrate one embodiment of a Z-form  100 . As shown, the Z-form  100  comprises a plurality of Z-pins  102  embedded within a carrier  104 . In one embodiment, the typical Z-pin  102  has a diameter of 0.011 inches and a length of 0.5 inches and is made out of a rigid material such as stainless steel, titanium, copper, graphite, epoxy, composite, glass, carbon, or the like. Typically, the manufacturer embeds an array of Z-pins  102  within the carrier  104 , which is often made of a foam-like material, for shipping purposes. In one embodiment, the manufacturer embeds the Z-pins  102  at a density of 400 per square inch. As will be described in greater detail below, the Z-form  100  is positioned on an uncured composite structure, and an insertion tool moves the Z-pins  102  out of the carrier  104  and into the composite structure to reinforce the same.  
         [0023]    Turning now to FIGS. 3A and 3B, one embodiment of a Z-form position detector  110  is illustrated. The position detector  110  is situated adjacent to a composite structure  180 . In the embodiment shown, the composite structure  180  comprises a laminate skin  182 . As is widely known in the art, the laminate skin  182  comprises a plurality of layers of composite material adhered together.  
         [0024]    Also, the composite structure  180  comprises a hat stiffener  184  positioned atop the laminate skin  182 . Like the laminate skin  182 , the hat stiffener  184  is made out of composite material. As shown in FIGS. 3A and 3B, the hat stiffener  184  includes three portions: a pair of flanges  185   a ,  185   b  that largely lie flush with and are adhered to the laminate skin  182 ; a pair of trusses  186   a ,  186   b  that extend outward away from the laminate skin  182 ; and a top portion  187 , positioned parallel to the laminate skin  182  and extending between the trusses  186   a ,  186   b.    
         [0025]    As is widely known in the art, when the flanges  185   a ,  185   b  are attached to the laminate skin  182 , the orientation of the trusses  186   a ,  186   b  largely inhibits the laminate skin  182  from bending. Advantageously, the hat stiffener  184  increases the stiffness of the laminate skin  182 , thereby broadening the variety of possible applications for the composite structure  180 .  
         [0026]    It is noted that the composite structure  180  illustrated in FIGS. 3A and 3B is used only for illustration. Thus, the Z-form position detector  110  could be used in conjunction with a variety of composite structures  180  without departing from the spirit of the invention.  
         [0027]    In one embodiment, individual Z-forms  100  are positioned atop the flanges  185   a ,  185   b  so that each of the Z-pins  102  are oriented axially toward the hat stiffener  184  and laminate skin  182 . As will be discussed in greater detail below, the Z-pins  102  are pushed out of the carrier  104  of the Z-form  100  and into the hat stiffener  184  and laminate skin  182  to reinforce the bond between the flanges  185   a ,  185   b  and the laminate skin  182 . However, before this process can be completed, the Z-forms  100  must be located with precision.  
         [0028]    As shown in FIGS. 3A and 3B, the Z-form position detector  110  comprises a laser unit  160 . The laser unit  160  is widely known in the art for emitting a focused beam of light. In the embodiment shown, the laser unit  160  is aimed generally  300  from normal to the surface of the laminate skin  182  and it oscillates in a direction generally parallel to the surface of the laminate skin  182  and at 900 to the longitudinal axis of the Z-form  100  and hat stiffener  184 . As is shown in FIGS. 3A, 3B, and  4 , the oscillations are preferably fast enough such that the laser unit  160  forms the appearance of a line  164  of light across the composite structure  180  and Z-forms  100 .  
         [0029]    As is shown, the line  164  is discontinuous because of the varied topography of the composite structure  180 . Particularly, the line  164  forms a discontinuity  166  where the line  164  intersects the edges of the Z-forms  100 . As will be discussed in greater detail, since the discontinuities  166  accurately correspond to the edges of the Z-form  100 , the discontinuities  166  can be used to detect the position of the Z-forms  100  with precision.  
         [0030]    Moreover, the Z-form position detector  100  comprises a sensor  130 . In one embodiment, the sensor  130  is an analog or digital unit sensitive to the frequency of the light emitted from the laser unit  160 , and it is also calibrated positionally with respect to other components of the Z-form position detector  110 . The sensor  130  is suspended above and pointed normal to the surface of the laminate skin  182 . Oriented as such, the sensor  130  scans the surface of the Z-form  100  and is able to detect frequency of the laser line  164  and any discontinuities  166  (i.e., changes in intensity caused by the transition from a continuous line to a broken or blurred line).  
         [0031]    As shown, the sensor  130  and laser unit  160  are attached to an end effector  132 . In one embodiment, the end effector  132  moves the sensor  130  and laser unit  160  in a direction generally parallel to the surface of the laminate skin  182 .  
         [0032]    In one embodiment, the sensor  130  scans only a predetermined area of the Z-form  100 . This area is known as the sensor window  134  (shown in FIG. 4), and is as long and as wide as the width of the laser line  164  in one embodiment. As stated, both the laser unit  160  and sensor  130  are attached to the end effector  132 , allowing alignment between the laser unit  160  and sensor  130 . Thus, the sensor window  134  is centered over the line  164 .  
         [0033]    As will be described in more detail, the sensor  130  is able to scan the surface of the Z-form  100  falling within the sensor window  134 . The sensor  130  scans along the laser line  164  and recognizes the frequency of that light. However, when the sensor  130  fails to detect the laser line (i.e., when a discontinuity  166  enters the sensor window  134 ), the sensor  130  takes note of the precise positional coordinates of the point where the laser line stopped being detected. These positional coordinates are then used to ascertain the position of the entire Z-form  100  for subsequent Z-pin  102  insertion.  
         [0034]    It is understood that the components used in this embodiment of the Z-form position detector  110  are relatively inexpensive, reliable, and can easily be incorporated into a production environment. Thus, the Z-form position detector  110  does not significantly increase the costs of the automatic pinning process.  
         [0035]    [0035]FIG. 5 illustrates one embodiment of a method  140  of utilizing the Z-form position detector  110  described herein above. Beginning with a first step  142 , a user positions the Z-forms  100  over the composite structure  180 . With respect to the embodiment shown in FIGS. 3A and 3B, performing the first step  142  involves positioning the Z-forms  100  on the flanges  185   a ,  185   b  of the hat stiffener  184  such that the Z-pins  102  are pointed axially toward the flanges  185   a ,  185   b  and the laminate skin  182  lying thereunder.  
         [0036]    Next, in a second step  143 , the oscillating laser unit  160  functions to form the line  164  on the composite structure  180 . As described above, the line  164  includes discontinuities  166  due to the topography of the composite structure  180 .  
         [0037]    Furthermore, in a third step  146  of the method  140 , the end effector  132  moves the sensor  130  approximately parallel to surface of the laminate skin  182 , moving the sensor window  134  along the line  164 . The method  140  continues into a first decision state  148 , wherein it is asked whether a discontinuity  166  is detected within the sensor window  134 . If the sensor  130  does not detect a discontinuity  166  (i.e., if the sensor  130  recognizes a continuous laser line within the sensor window  134 ), the fourth step  146  continues and the sensor  130  actuates along the line  164 .  
         [0038]    However, if the sensor  130  does detect a break in the laser line within the sensor window  134  (i.e., the sensor window  134  encompasses a discontinuity  166 ), then the first decision state  148  can be answered in the affirmative, giving way to a fourth step  150 . In the fourth step  150 , the sensor  130  sends a detection signal to external circuitry and logic (not shown), which translates the detection signal into precise positional coordinates of the point at which the laser line discontinuity occurs. Since the discontinuity  166  corresponds with the edge of the Z-form  100 , these positional coordinates represent a point on the edge of the Z-form  100 . In the preferred embodiment, the positional coordinates obtained by the sensor  130  are accurate within +/−0.025 inches or better.  
         [0039]    The method  140  then moves into a second decision state  152 . If additional coordinates of the edge of the Z-form  100  are needed before the Z-pins  102  can be driven into the composite structure  180 , then the method  140  moves into a fifth step  154 . In the fifth step  154 , the end effector  132  moves the laser unit  160  and sensor  130  along the axis of the Z-form  100 . Then, the second step  143  is repeated so as to generate a new line  166  over a different section of the Z-form  100 . The method  140  continues as detailed above and new coordinates are procured, until no new coordinates are needed. For example, it is understood that after two discontinuities  166  at different axial positions are detected, accurate positional coordinates for the entire edge of the Z-form  100  are known. However, it is also understood that the number of measurements can be increased for more overall accuracy. Therefore, in one embodiment, the method  140  is used to locate three discontinuities  166  at different axial positions of the Z-form  100  for a more accurate representation of the edge of the Z-form  100 .  
         [0040]    Upon completion of the method  140 , the procured positional coordinates allow an insertion tool (not shown) to automatically move precisely above the Z-form  100  and drive the Z-pins  102  out of the carrier  104  and into the composite structure  180 . The Z-pins  102  reinforce the attachment between the hat stiffener  184  and the laminate skin  182 .  
         [0041]    In one embodiment, the end effector  132  is attached to the insertion tool (not shown). As such, since the laser unit  160  and sensor  130  are located on the insertion tool, the insertion tool requires less movement, thereby reducing manufacturing time and cost.  
         [0042]    Both the Z-form location detector  110  and the method  140  of using the same allow the precise locations of Z-forms to be ascertained automatically. Obtaining these precise positional coordinates is advantageously quicker than manually determining the precise location of the Z-forms. Also, the present invention allows for automatic insertion of reinforcing Z-pins into composite structures. Thus, the automation described herein advantageously saves time and money in the manufacturing of composite structures.  
         [0043]    Turning now to FIG. 6, an alternative embodiment of the Z-form position detector  110  is illustrated. This embodiment is similar to the embodiment described above, except that the sensor  130  is capable of scanning more of the line  164  at one time. In other words, the sensor window  134  is relatively long and can encompass more of the portion of the line  164  falling on the Z-form  100 . Preferably, its size allows the sensor window  134  to encompass a discontinuity  166  without having to physically move the sensor  130 . For instance, a linear array sensor  130  is used in one embodiment so that the sensor  130  need not move. As such, this absence of actuation speeds up the process of detecting the discontinuities  166 . Advantageously, since the sensor  130  is not actuated, manufacturing time and costs are advantageously reduced.  
         [0044]    This disclosure provides exemplary embodiments of the present invention. The scope of the present invention is not limited by these exemplary embodiments. Numerous variations, whether explicitly provided for by the specification or implied by the specification, such as variations in structure, dimension, type of material and manufacturing process may be implemented by one of skill in the art in view of this disclosure.