Real-time inspection of automated ribbon placement
A technique for automated online inspection of manufacture of a fibre reinforced polymer composite part during automated ribbon placement (e.g. ATL or AFP) uses interferometric inspection (e.g. OCT) to detect deviations from a planned lay-up for the part, to identify defects. On line, real-time inspection (i.e. on-the-fly) is demonstrated, and edge type defects and whole surface defects are identifiable. A sensor is demonstrated that does not extend a working envelope of the robotic head used for rib bon placement.
1. An automated process for online monitoring of Automated Ribbon Placement ARP, the process comprising:
feeding a ribbon while providing robotic control to move an applicator against a previously deposited layer composed of one or more ribbons, to press the ribbon against the layer to build up a fibre reinforced composite;
scanning a beam of light across a surface of the ribbon at a first location of the ribbon after the pressing, while the same ribbon is being pressed on the layer at a second location, the beam illuminating a spot on the surface;
collecting light scattered from the spot to obtain a sample beam;
directing the sample beam and a reference beam onto a photodetector, to obtain an electrical interference signal;
receiving a plurality of the electrical interference signals that characterizes a topography of the deposited ribbon on the surface; and
processing the plurality of the electrical interference signals to identify whether a deviation from a planned lay-up of the ribbon is manifest.
2. The process according to claim 1 wherein collecting the scattered light comprises collecting back-reflected light from the first location.
3. The process according to claim 2 wherein scanning the beam and collecting the light are jointly performed by an optical device mounted to a robotic head that includes the applicator.
4. The process according to claim 3 wherein the optical device is statically mounted to the robotic head, whereby the first and second locations have constant separation except for a bounded variation caused by a tilting of the robotic head, and the optical device is centered on the ribbon except for a bounded variation caused by a steering of the ribbon.
5. The process according to claim 3 wherein scanning further comprises line scanning the spatial illumination pattern in a direction that is generally transverse to the ribbon, whereby, in each cycle of the line scan, the spatial illumination pattern illuminates at least part of a width the ribbon including at least one edge thereof.
6. The process of according to claim 5 wherein the optical device couples light to at least one optical fibre.
7. The process according to claim 5 wherein during the line scanning a distance between where the applicator meets the surface and the spot is maintained between ⅓ and 3 times a radius of the applicator.
8. The process according to claim 3 wherein the electrical interference signal includes tomographic and topographic information that collectively characterize the topography of the surface and the ribbon.
9. The process according to claim 5 wherein the ribbon is composed of high absorption, carbon-fibres.
10. The process according to claim 3 further comprising generating the beam of light and reference beam from a white light source, a swept wavelength source, a laser, or a diode, where receiving the plurality of electrical interference signals comprises applying signal processing according to an associated interferometric technique.
11. The process according to claim 3 where processing the plurality of signals is based on the processing of a single scan, a combination of successive scans, or a combination of scans on adjacent regions.
12. A kit for adapting an Automated Ribbon Placement ARP head for online monitoring, the kit comprising:
an interferometric topographic sensor adapted to generate an interferometric signal;
instructions or mounting supplies for mounting the sensor to the AFP head at a position and orientation to record a topography of a surface of a ribbon after deposition; and
program instructions that, run on a processor enables to processor to:
process the interferometric signal in real-time to obtain topographical information characterizing the ribbon after deposition; and
use the topographical information to determine whether a planned lay-up is being executed flawlessly, or whether a defect is present.
13. The kit as claimed in claim 12 further comprising the ARP head, which comprises:
at least a part of a ribbon supply for feeding a ribbon composed of a carbon fiber reinforced polymer (CFRP);
a ribbon cutter for cutting the ribbon fed through the part of the ribbon supply; and
an applicator for pressing the fed ribbon against a tooling to build up a CFRP composite part, under a control and guidance of the robot.
14. The kit as claimed in claim 12 wherein the interferometric topographic sensor is an OCT sensor with a sampling rate above 50 KHz, with a scanner for moving a spot of illumination on the surface in a direction that is generally transverse to the ribbon after deposition, the scanner having a speed of at least 1 cm per second.
15. The kit as claimed in claim 12 wherein the sensor comprises: a beam source, focusing and collecting optics, and a photodetector; wherein an angle of incidence of the beam on the surface, the focusing and collecting optics, a power of the beam source, and a sensitivity of the photodetector are chosen so that the interferometric signal generated provides tomographic and topographic information that collectively characterize the topography of the surface for a ribbon composed of high absorption, carbon-fibres.
16. The kit as claimed in claim 12 wherein the instructions or mounting supplies for mounting to the AFP head places the sensor entirely within a previously established envelop of the AFP head.
17. The kit as claimed in claim 12 wherein the interferometric topographic sensor is a Swept Source OCT sensor.
18. The kit as claimed in claim 13 wherein the kit is assembled and mounted to a robot.
19. The kit as claimed in claim 13 wherein the interferometric topographic sensor is an OCT sensor with a sampling rate above 50 KHz, with a scanner for moving a spot of illumination on the surface in a direction that is generally transverse to the ribbon after deposition, the scanner having a speed of at least 1 cm per second.
20. The kit as claimed in claim 19 wherein the sensor comprises: a beam source, focusing and collecting optics, and a photodetector; wherein an angle of incidence of the beam on the surface, the focusing and collecting optics, a power of the beam source, and a sensitivity of the photodetector are chosen so that the interferometric signal generated provides.