Robotic vision system to locate Z-forms

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.

CROSS-REFERENCE TO RELATED APPLICATIONS

BACKGROUND OF THE INVENTION

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.

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.

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 “Z-pins,” through the parts normal to the bondline. As such, the Z-pins bear a portion of the loading that might otherwise damage the bondline.

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.

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.

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.

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

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.

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.

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.

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.

DETAILED DESCRIPTION OF THE INVENTION

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. 1andFIG. 2illustrate one embodiment of a Z-form100. As shown, the Z-form100comprises a plurality of Z-pins102embedded within a carrier104. In one embodiment, the typical Z-pin102has 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-pins102within the carrier104, which is often made of a foam-like material, for shipping purposes. In one embodiment, the manufacturer embeds the Z-pins102at a density of 400 per square inch. As will be described in greater detail below, the Z-form100is positioned on an uncured composite structure, and an insertion tool moves the Z-pins102out of the carrier104and into the composite structure to reinforce the same.

Turning now toFIGS. 3A and 3B, one embodiment of a Z-form position detector110is illustrated. The position detector110is situated adjacent to a composite structure180. In the embodiment shown, the composite structure180comprises a laminate skin182. As is widely known in the art, the laminate skin182comprises a plurality of layers of composite material adhered together.

Also, the composite structure180comprises a hat stiffener184positioned atop the laminate skin182. Like the laminate skin182, the hat stiffener184is made out of composite material. As shown inFIGS. 3A and 3B, the hat stiffener184includes three portions: a pair of flanges185a,185bthat largely lie flush with and are adhered to the laminate skin182; a pair of trusses186a,186bthat extend outward away from the laminate skin182; and a top portion187, positioned parallel to the laminate skin182and extending between the trusses186a,186b.

As is widely known in the art, when the flanges185a,185bare attached to the laminate skin182, the orientation of the trusses186a,186blargely inhibits the laminate skin182from bending. Advantageously, the hat stiffener184increases the stiffness of the laminate skin182, thereby broadening the variety of possible applications for the composite structure180.

It is noted that the composite structure180illustrated inFIGS. 3A and 3Bis used only for illustration. Thus, the Z-form position detector110could be used in conjunction with a variety of composite structures180without departing from the spirit of the invention.

In one embodiment, individual Z-forms100are positioned atop the flanges185a,185bso that each of the Z-pins102are oriented axially toward the hat stiffener184and laminate skin182. As will be discussed in greater detail below, the Z-pins102are pushed out of the carrier104of the Z-form100and into the hat stiffener184and laminate skin182to reinforce the bond between the flanges185a,185band the laminate skin182. However, before this process can be completed, the Z-forms100must be located with precision.

As shown inFIGS. 3A and 3B, the Z-form position detector110comprises a laser unit160. The laser unit160is widely known in the art for emitting a focused beam of light. In the embodiment shown, the laser unit160is aimed generally about 20° to about 40°, and preferably, 30° from normal to the surface of the laminate skin182and it oscillates in a direction generally parallel to the surface of the laminate skin182and at 90° to the longitudinal axis of the Z-form100and hat stiffener184. As is shown inFIGS. 3A,3B, and4, the oscillations are preferably fast enough such that the laser unit160forms the appearance of a line164of light across the composite structure180and Z-forms100.

As is shown, the line164is discontinuous because of the varied topography of the composite structure180. Particularly, the line164forms a discontinuity166where the line164intersects the edges of the Z-forms100. As will be discussed in greater detail, since the discontinuities166accurately correspond to the edges of the Z-form100, the discontinuities166can be used to detect the position of the Z-forms100with precision.

Moreover, the Z-form position detector100comprises a sensor130. In one embodiment, the sensor130is an analog or digital unit sensitive to the frequency of the light emitted from the laser unit160, and it is also calibrated positionally with respect to other components of the Z-form position detector110. The sensor130is suspended above and pointed normal to the surface of the laminate skin182. Oriented as such, the sensor130scans the surface of the Z-form100and is able to detect frequency of the laser line164and any discontinuities166(i.e., changes in intensity caused by the transition from a continuous line to a broken or blurred line).

As shown, the sensor130and laser unit160are attached to an end effector132. In one embodiment, the end effector132moves the sensor130and laser unit160in a direction generally parallel to the surface of the laminate skin182.

In one embodiment, the sensor130scans only a predetermined area of the Z-form100. This area is known as the sensor window134(shown inFIG. 4), and is as long and as wide as the width of the laser line164in one embodiment. As stated, both the laser unit160and sensor130are attached to the end effector132, allowing alignment between the laser unit160and sensor130. Thus, the sensor window134is centered over the line164.

As will be described in more detail, the sensor130is able to scan the surface of the Z-form100falling within the sensor window134. The sensor130scans along the laser line164and recognizes the frequency of that light. However, when the sensor130fails to detect the laser line (i.e., when a discontinuity166enters the sensor window134), the sensor130takes 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-form100for subsequent Z-pin102insertion.

It is understood that the components used in this embodiment of the Z-form position detector110are relatively inexpensive, reliable, and can easily be incorporated into a production environment. Thus, the Z-form position detector110does not significantly increase the costs of the automatic pinning process.

FIG. 5illustrates one embodiment of a method140of utilizing the Z-form position detector110described herein above. Beginning with a first step142, a user positions the Z-forms100over the composite structure180. With respect to the embodiment shown inFIGS. 3A and 3B, performing the first step142involves positioning the Z-forms100on the flanges185a,185bof the hat stiffener184such that the Z-pins102are pointed axially toward the flanges185a,185band the laminate skin182lying thereunder.

Next, in a second step143, the oscillating laser unit160functions to form the line164on the composite structure180. As described above, the line164includes discontinuities166due to the topography of the composite structure180.

Furthermore, in a third step146of the method140, the end effector132moves the sensor130approximately parallel to surface of the laminate skin182, moving the sensor window134along the line164. The method140continues into a first decision state148, wherein it is asked whether a discontinuity166is detected within the sensor window134. If the sensor130does not detect a discontinuity166(i.e., if the sensor130recognizes a continuous laser line within the sensor window134), the fourth step146continues and the sensor130actuates along the line164.

However, if the sensor130does detect a break in the laser line within the sensor window134(i.e., the sensor window134encompasses a discontinuity166), then the first decision state148can be answered in the affirmative, giving way to a fourth step150. In the fourth step150, the sensor130sends 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 discontinuity166corresponds with the edge of the Z-form100, these positional coordinates represent a point on the edge of the Z-form100. In the preferred embodiment, the positional coordinates obtained by the sensor130are accurate within +/−0.05 inches, and more preferably, within +/−0.025 inches or better.

The method140then moves into a second decision state152. If additional coordinates of the edge of the Z-form100are needed before the Z-pins102can be driven into the composite structure180, then the method140moves into a fifth step154. In the fifth step154, the end effector132moves the laser unit160and sensor130along the axis of the Z-form100. Then, the second step143is repeated so as to generate a new line166over a different section of the Z-form100. The method140continues as detailed above and new coordinates are procured, until no new coordinates are needed. For example, it is understood that after two discontinuities166at different axial positions are detected, accurate positional coordinates for the entire edge of the Z-form100are known. However, it is also understood that the number of measurements can be increased for more overall accuracy. Therefore, in one embodiment, the method140is used to locate three discontinuities166at different axial positions of the Z-form100for a more accurate representation of the edge of the Z-form100.

Upon completion of the method140, the procured positional coordinates allow an insertion tool (not shown) to automatically move precisely above the Z-form100and drive the Z-pins102out of the carrier104and into the composite structure180. The Z-pins102reinforce the attachment between the hat stiffener184and the laminate skin182.

In one embodiment, the end effector132is attached to the insertion tool (not shown). As such, since the laser unit160and sensor130are located on the insertion tool, the insertion tool requires less movement, thereby reducing manufacturing time and cost.

Both the Z-form location detector110and the method140of 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.

Turning now toFIG. 6, an alternative embodiment of the Z-form position detector110is illustrated. This embodiment is similar to the embodiment described above, except that the sensor130is capable of scanning more of the line164at one time. In other words, the sensor window134is relatively long and can encompass more of the portion of the line164falling on the Z-form100. Preferably, its size allows the sensor window134to encompass a discontinuity166without having to physically move the sensor130. For instance, a linear array sensor130is used in one embodiment so that the sensor130need not move. As such, this absence of actuation speeds up the process of detecting the discontinuities166. Advantageously, since the sensor130is not actuated, manufacturing time and costs are advantageously reduced.