Patent Application
20070097359
The present invention relates generally to automated material placement machines and their use. More particularly (but not exclusively) the present invention relates to systems and methods for inspecting material laid by an automated material placement machine.
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.
The present invention, 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 imperfections in the section.
In another aspect, the invention 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 imperfections in the section.
In yet another aspect, the invention 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 imperfections in the section. One or more cameras are configured to record the section through the one or more transparent portions of the mirror.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating various preferred embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
The following description of various embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.
In some implementations, the invention 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 invention 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 in
One implementation of a method of inspecting material laid by a material placement machine, e.g., the machine 24, is indicated generally in
The light source 124 above the material 28 may be configured to illuminate a full width of the material 28. The laser striping 144 can reveal gaps and/or overlaps in the material 28. Additionally, the striping can enhance the illumination from the light source 124 and 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 source 124 and a single laser source 140 are used in the implementation 100, 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 in
A plurality of light sources 216 are mounted, for example, such that they project light essentially parallel to an axis 220 of placement of the material 28. Light from the light sources 216 may be projected toward the mirror 212 and reflected by the mirror reflective portion(s) onto the material 28 in a direction essentially normal to the material.
A plurality of laser sources 224 mounted to the frame 204 are configured to project laser energy directly onto the material 28 at an angle predetermined to reveal imperfections in the material. The laser sources 224 may be, for example, Lasaris™ SNF line lasers by StockerYale, Inc. of Salem, N.H.
A plurality of cameras 230 are mounted in the frame 204 above the mirror 212. The cameras 230 are configured to image, through one or more transparent portions 234 of the mirror 212, a section of the material 28 illuminated by the light and laser sources 216 and 224. The cameras 230 may be actuated, for example, by the processor 40, which receives images from the cameras 230 and/or memory 44. The processor 40 may process the images to facilitate reliable detection of defects.
The cameras 230 are, for example, Sony XC-HR50 cameras, although other cameras could be used. The cameras 230 collectively 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 camera 230 is 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 sources 216 and 224 are configured to illuminate the full width of the newly laid material 28. The illumination is reflected differently by defects in the material than by portions of the material that are defect-free. Such differences in illumination can be captured in images produced by the cameras 230. The frame 204 may be configured to shield the light sources and cameras so as to optimize the quality of imaging by the cameras 230. 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 sources 216 include 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 material 28 can 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 flaws 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) 216 may depend at least in part on the speed and sensitivity of the cameras 230, speed at which the material 28 is 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 in
When the machine 24 is in operation, motion of the machine may be detected by the processor 40, 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 Defect Characteristics of a Composite Structure”, the disclosure of which is incorporated herein in its entirety. The processor 40 thereby determines that the machine 24 is in operation. The processor 40 actuates the cameras 230 to obtain images at appropriate times based on movement of the machine 24. Specifically and for example, by tracking distances moved by the machine 24, the processor 40 may actuate the cameras 230 to obtain images of material newly placed on the substrate 32 and which is currently being illuminated by the light and laser sources 216 and 224. The processor 40 may receive each image and may assign unique numbers to frames of the image data from the cameras 230. The processor 40 may store image frames in the memory 44 and may use them to track a linear position of the machine 24 as material is placed on the substrate 32.
The processor 40 processes the image data in a frame to detect defects in the imaged section of material 28. The processor 40 also analyzes and displays selected defects on the user interface 50. A defect dimension, for example, a defect width, can be determined as follows. After a digital image of a defect has been acquired, a pixel set is selected from the digital image that represents the width of the defect. The pixels in the pixel set are counted, and the count is correlated with distance to determine the defect width.
The processor 40 may receive images from the cameras 230 and/or memory 44 and may process the images to facilitate the reliable detection of defects. The processor 40 may display information on the user interface display screen 54, for example, as shown in
It should be understood that in various implementations, images from the cameras 230 could be displayed in various ways on the user interface 50. For example, images from two or more cameras 230 could be displayed simultaneously, e.g., side by side in a frame on the screen 54, or sequentially in different frames.
The frame 300 may 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 defects and improve the accuracy of defect 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 defects.
The foregoing systems and methods provide improved illumination and inspection across varying material widths. Various implementations of the invention 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 invention 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 invention 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.
