Background
Composite materials have become a critical component in high-performance aerospace systems. However, fabrication of composite-based parts is still a time-consuming and expensive process, in many cases requiring significant manual labor. This project involves further development of technologies aimed at autonomous layup of prepreg composite plies—sheets of woven material, typically carbon fibers, pre-impregnated with resin—onto molds to fabricate aerospace parts. The end goal of the project is a robotic workcell with the capabilities needed to perform automated composite layup.
The work is a joint effort between SwRI, the Advanced Robotics for Manufacturing Institute (ARM), the University of Southern California (USC), and Lockheed Martin. USC recently led a project, funded by ARM, that demonstrated a complete automated layup work cell; SwRI supported the system architecture and the operator interaction system as part of that project. In parallel to the ARM-funded project, SwRI is internally developing complementary technology for additional parts and layup methods.
Approach
The approach involves determining algorithms to autonomously define and plan robot motions for handling prepreg composite plies. The project uses a two-robot work cell where one robot is tasked to hold a ply above the mold, letting it hang loosely. A second robot uses a tool to press the ply onto the mold, conforming it to the mold geometry, which is known as draping. Since the mold geometry is known ahead of time, it can be used to generate a sequence of individual robot motions to achieve a consistent drape over the full surface of the mold.
To generate the sequence of robot motions, the current approach assumes there is an expert operator who can input information about which regions of the mold should be draped and in what order. Software developed in this project can then take over and determine a set of positions for the draping tool to move through using high-level parameters that control the draping behavior. Additional software is then used to find robot trajectories (i.e., how the robot manipulates its various joints to move the tool through the desired positions). In the end, the framework enables the full layup of a mold with multiple plies and consistency comparable to a human operator.
Accomplishments
The project has successfully demonstrated composite layup of full parts in functional robot work cells. The ARM-funded project concluded successfully at USC when the robotic system performed a complete layup of a large aerospace part mounted on a rotating mold. This system made use of SwRI’s operator interface software for monitoring the layup progress. At SwRI, a work cell with two collaborative robots successfully performed layup of two different mold geometries.