Model-predictive impedance control of pneumatic continuum actuators in the continuous wet draping process (OptiDrap)

• Applicant: Professor Dr.-Ing. Berend Denkena
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 495148995

High-performance components made of fiber reinforced plastics can be produced in automated draping processes. The components can be highly complex in shape limited, among other things, by the textile properties. However, the ability of the draping system to reproduce the required draping shapes and to lay up the web-shaped semi-finished fiber-textile close to the final contours and with a foreseeable orientation of the fibers has a far more restrictive effect with increasing complexity of the components.In own previous simulative investigations on the continuous draping of web-shaped semi-finished products, it was found that the line along which the textile is pressed against the tool surface at a certain point in time during draping can be approximated sufficiently well as a three-dimensional spline. This draping spline is chosen so that the textile experiences the most constant tension over its entire width. Its shape changes continuously during draping depending on the surface geometry. A flexible draping element was developed for continuous pressing of the textile on the draping line and implemented in a test rig. Pneumatic continuum actuators (CA) interpolate the draping line between rigid support points. The project OptiDrap follows the research hypothesis that it is possible to regulate the textile tension by adapting the draping spline during lay up and that the impedance of the CA in the contact trajectory can be observed and regulated. Derived from this, the project aims at researching and modeling the interactions of textile, surface geometry and draping element for integration into a process control dependent on textile tension.Basic knowledge of the interactions occurring in the draping process in the deposit area depending on draping kinematic parameters is obtained experimentally. Based on the knowledge gained in the course of the investigations, an existing process model for the CWD (continuous wet draping) process is expanded to include precisely these technology-related interactions and an online-capable calculation of the state of the fabric lay-up is established with the sensory detection of the textile tension.The CA of the draping element has infinite degrees of freedom due to the elastic sleeve material and enables stretching well over 100%, which makes it difficult to detect the dynamic state of deformation and contact forces. In the field of soft robotic, model-based control concepts are therefore used. A sub-goal of the project is therefore the constitutive modeling of the interaction of the CA when draping and the design of an impedance control based on this modeling to influence the surface pressure at the contact trajectory. This enables the system to adaptively compensate the textile tension by changing the draping spline in the process.

• DFG Programme: Research Grants