Apparatus and methods for inspecting a composite structure for inconsistencies

A system and method of inspecting material laid by a material placement machine. Light is directed onto the material in a direction essentially normal to the material to illuminate a section of the material. Laser energy is projected onto the section at an angle predetermined to reveal inconsistencies in the section. This system provides improved illumination for material widths exceeding six inches and is scalable for inspecting various material widths.

FIELD

The present disclosure relates generally to automated material placement machines and their use. More particularly (but not exclusively) the present disclosure relates to systems and methods for inspecting material laid by an automated material placement machine.

BACKGROUND

Automated material placement processes and machines are widely used in aerospace and other industries in the fabrication of large composite structures. Systems are available by which automated visual inspection can be performed while the material is being laid. These systems have been shown to be effective in reducing machine down-time for inspection purposes. Current inspection systems, however, have limited effectiveness when used to inspect materials wider than about six inches.

SUMMARY

The present disclosure, in one aspect, is directed to a method of inspecting material laid by a material placement machine. Light is directed onto the material in a direction essentially normal to the material to illuminate a section of the material. Laser energy is projected onto the section at an angle predetermined to reveal inconsistencies in the section.

In another aspect, the disclosure is directed to a system for inspecting material laid by a material placement machine. The system includes a mirror and one or more light sources configured to project light onto the mirror. The mirror is configured to reflect the projected light onto a section of the material in a direction essentially normal to the section. One or more laser sources are configured to project laser energy onto the section at an angle predetermined to reveal inconsistencies in the section.

In yet another aspect, the disclosure is directed to a system for inspecting material laid by a material placement machine. The system includes a mirror suspended over a section of the material that has been laid. The mirror has one or more transparent portions. One or more light sources are configured to project light onto one or more reflective portions of the mirror. The mirror is further configured to reflect the projected light onto the material section in a direction essentially normal to the section. One or more laser sources are configured to project laser energy onto the section at an angle predetermined to reveal inconsistencies in the section. One or more cameras are configured to record the section through the one or more transparent portions of the mirror.

DETAILED DESCRIPTION

The following description of various embodiments is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses.

In some implementations, the disclosure is directed to systems and methods of inspecting material laid by a material placement machine. The placement machine could be, for example, a multi-head tape lamination machine (MHTLM), a fiber placement (FP) machine, or a contour tape lamination (CTL) machine. It should be noted that implementations of the disclosure may be practiced in connection with a wide variety of material placement machines and processes.

A block diagram of an exemplary material placement system is indicated generally inFIG. 1by reference number20. A material placement machine24is used to lay down composite material28onto a substrate32to fabricate a composite structure. The machine24includes a roller, compaction shoe and/or other component, numbered as36and dependent on the type of placement machine, for laying the material28onto the substrate32. The system20includes a processor40having a memory and/or storage device44. The processor40is in communication with the machine24. A user interface50may be, e.g., a computer monitor including a display screen54and an input device such as a keyboard and mouse (not shown). The user interface50is in communication with the processor40.

One implementation of a method of inspecting material laid by a material placement machine, e.g., the machine24, is indicated generally inFIG. 2by reference number100. A width of the material28is newly laid on the substrate32by the machine24. Light is directed onto the material28in a direction120essentially normal to the material to illuminate the material. Specifically and for example, the light is projected from a light source124onto a reflective surface128and reflected by the surface128onto the material28to illuminate a section132of the laid material. The method100also includes projecting laser energy onto the section132at an angle predetermined to reveal inconsistencies in the section132. In the present implementation, a laser source140projects the laser energy as one or more lines144onto the section132. The lines or stripes are projected, for example, across an axis148of placement of the material28. It should be noted that other implementations are contemplated in which different laser patterns and/or laser projection orientations may be used.

The light source124above the material28may be configured to illuminate a full width of the material28. The laser striping144can reveal gaps and/or overlaps in the material28. Additionally, the striping can enhance the illumination from the light source124and can help reveal such items as fuzz balls, resin balls, and backing materials.

The present method can be implemented in various ways on various placement machines. Additionally, and as further described below, implementations of the present method can be scaled to various widths of material to be inspected. For example, although a single light source124and a single laser source140are used in the implementation100, a plurality of light sources and/or a plurality of laser sources may be used in other implementations.

One exemplary embodiment of a system for inspecting material laid by a material placement machine is indicated generally inFIGS. 3-7by reference number200. The system200includes a frame204having brackets208configured for attachment to a placement machine, e.g., the machine24(shown inFIG. 1). It should be noted that other embodiments of the system200could be configured in various ways in relation to material placement machines, dependent on width of material to be inspected and placement machine configuration. For purposes of describing the present embodiment, it shall be assumed that component36of the machine24is a compaction roller. The frame204is configured for attachment, for example, above and behind the compaction roller36such that the frame204overhangs newly laid material28. A mirror212is mounted in the frame204, for example, at a 45-degree angle. The mirror212is at least partially silvered to provide one or more reflective portions.

A plurality of light sources216are mounted, for example, such that they project light essentially parallel to an axis220of placement of the material28. Light from the light sources216may be projected toward the mirror212and reflected by the mirror reflective portion(s) onto the material28in a direction essentially normal to the material.

A plurality of laser sources224mounted to the frame204are configured to project laser energy directly onto the material28at an angle predetermined to reveal inconsistencies in the material. The laser sources224may be, for example, Lasaris™ SNF line lasers by StockerYale, Inc. of Salem, N.H.

A plurality of cameras230are mounted in the frame204above the mirror212. The cameras230are configured to image, through one or more transparent portions234of the mirror212, a section of the material28illuminated by the light and laser sources216and224. The cameras230may be actuated, for example, by the processor40, which receives images from the cameras230and/or memory44. The processor40may process the images to facilitate reliable detection of inconsistencies.

The cameras230are, for example, Sony XC-HR50 cameras, although other cameras could be used. The cameras230collectively have fields of view sufficiently broad to image a full width of the newly laid material. A wide range of cameras can be used, including commercially available cameras capable of acquiring black-and-white images. In one embodiment, a camera230is a television or other type of video camera having an image sensor and a lens through which light passes when the camera is in operation. Other types of cameras or image sensors can also be used, such as an infrared-sensitive camera, a visible light camera with infrared-pass filtration, a fiber-optic camera, a coaxial camera, charge-coupled device (CCD), or complementary metal oxide semiconductor (CMOS) sensor.

The light and laser sources218and224are configured to illuminate the full width of the newly laid material28. The illumination is reflected differently by inconsistencies in the material than by portions of the material that are free of inconsistencies. Such differences in illumination can be captured in images produced by the cameras230. The frame204may be configured to shield the light sources and cameras so as to optimize the quality of imaging by the cameras230. It should be noted that various lighting and reflective configurations are possible. For example, a half-mirror could be used such that light from light sources is reflected by the mirror onto the material, and the cameras are directed not through, but past the mirror.

In the present configuration, the light sources216include high-intensity red LEDs which produce area light. Other or additional types of lighting, including but not limited to fluorescent lights, could be used. The quality and magnitude of surface illumination of the material28can be affected by ambient lighting and by reflectivity of the material. Accordingly, in one embodiment, one or more infrared light sources and/or light sources having an infrared component may be used to illuminate dark inconsistencies on a dark background. In other embodiments, a strobe or stroboscopic light source, a noble gas arc lamp (e.g., xenon arc), metal arc lamp (e.g., metal halide) and/or laser (e.g., pulsed laser, solid state laser diode array and/or infrared diode laser array) could be used. Power levels and wavelengths for light source(s)216may depend at least in part on the speed and sensitivity of the cameras230, speed at which the material28is being laid, delivery losses, and reflectivity of the material being inspected. For example, in another embodiment, wavelengths and power levels suitable for inspecting highly reflective materials may be employed.

In the configuration shown inFIGS. 3-7, two light sources216, three laser sources224, and three cameras230are used. Each laser source224and camera230can cover, e.g., material widths of between about three and four inches. Coverage could be greater or smaller than the foregoing range depending, for example, on lens type, distance between material and cameras and/or laser sources, and other factors. Depending, for example, on a width of material to be inspected and placement system configuration, different numbers of light sources, laser sources and/or cameras could be included to facilitate material inspection. The system200thus can be scaled up or down to accommodate different material widths.

When the machine24is in operation, motion of the machine may be detected by the processor40, for example, via a code ring on the compaction roller and photo-interrupter as disclosed in U.S. patent application Ser. No. 10/726,099 entitled “Systems and Methods For Determining Inconsistency Characteristics of a Composite Structure”, the disclosure of which is incorporated herein in its entirety. The processor40thereby determines that the machine24is in operation. The processor40actuates the cameras230to obtain images at appropriate times based on movement of the machine24. Specifically and for example, by tracking distances moved by the machine24, the processor40may actuate the cameras230to obtain images of material newly placed on the substrate32and which is currently being illuminated by the light and laser sources216and224. The processor40may receive each image and may assign unique numbers to frames of the image data from the cameras230. The processor40may store image frames in the memory44and may use them to track a linear position of the machine24as material is placed on the substrate32.

The processor40processes the image data in a frame to detect inconsistencies in the imaged section of material28. The processor40also analyzes and displays selected inconsistencies on the user interface50. An inconsistency dimension, for example, an inconsistency width, can be determined as follows. After a digital image of an inconsistency has been acquired, a pixel set is selected from the digital image that represents the width of the inconsistency. The pixels in the pixel set are counted, and the count is correlated with distance to determine the inconsistency width.

The processor40may receive images from the cameras230and/or memory44and may process the images to facilitate the reliable detection of inconsistencies. The processor40may display information on the user interface display screen54, for example, as shown inFIG. 8. A window300includes a frame304showing at least part of a section308of material28imaged by the cameras230. For example, an illuminated area312of the section308is shown in the window300. Laser lines320produced by the laser sources224also are visible above the area312. Inconsistencies324may be labeled and are shown in the window300. A foreign object/debris (FOD)330struck by the laser lines320may be accentuated by the processor40for display in the frame300. The laser striping320can provide a “second-look” enhancement of areas lighted by the light sources216and thus can assist in revealing inconsistencies such as fuzz balls, resin balls, and backing materials. It should be noted, however, that although the laser striping320strikes the material28above the illuminated area312in the frame300, other arrangements of light source and laser source illumination are possible. In some embodiments, illumination from the light and laser sources216and224could be configured to overlap to a greater degree, or alternatively to strike material farther apart, than as shown inFIG. 8

It should be understood that in various implementations, images from the cameras230could be displayed in various ways on the user interface50. For example, images from two or more cameras230could be displayed simultaneously, e.g., side by side in a frame on the screen54, or sequentially in different frames.

The frame300may include a processed or unprocessed camera image. Additionally or alternatively, the frame may include an image that has been binarized. During binarization, all shades of gray above a predetermined threshold value can be changed to white, while all gray shades below the threshold are changed to black to heighten the contrast of inconsistencies and improve the accuracy of inconsistency detection. In other embodiments, the binarization operation need not be performed but instead the raw image, rates of change of the light levels in the raw image, and/or color changes in the images can be used to identify the inconsistencies.

The foregoing systems and methods provide improved illumination and inspection across varying material widths. Various implementations of the disclosure provide the ability to inspect wider bands of material more effectively than possible with current inspection systems, which use low-incident-angle side lighting to illuminate material under inspection. The dual on-axis lighting provided by implementations of the disclosure can provide even illumination across material widths and is scalable to varying widths.

While various preferred embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the inventive concept. The examples illustrate the disclosure and are not intended to limit it. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.