The continuous wet draping process enables the automated production of fiber composite components with high geometric complexity and enables new possibilities for efficient manufacturing of complex lightweight structures. The flexibility required for this is provided by the a draping element developed at IFW. This module consists of six serially arranged, pneumatically operated continuum actuators (CA) that expand lateral with an nearly consistent diameter when intrinsically pressurized. The draping element is shaped by two control mechanisms. The two-dimensional positioning of the actuator interfaces is ensured by seven two-axis parallel kinematics. The combination of two-dimensional positioning and intrinsic pressure on the KA CA enables the draping module to represent a three-dimensional spline. The underlying spline, also known as the draping line, is derived from an idealized, geometry-based draping simulation.
In an initial investigation, the focus was placed on the two-dimensional positioning of the parallel kinematics. The systems are equipped with Hall effect encoders, which enable precise adjustment of the desired angles of the KACA. In addition, an optical measuring system has been integrated to detect the actual position of the draping element. For this purpose, a , but these do not provide any information about the actual position of the draping module in space. To quantify the deviation between the target position and the actual position, a system consisting of four PrimeX-13 cameras from Optirack is used, which . This system can be used to measures the three-dimensional spatial coordinates of the markers located on the draping moduleelement. In order to take the actual position into account in the simulation, a calibration script was created that captures the spatial coordinates of the reference points throughout the entire movement range of the parallel kinematics. The measurement points and target coordinates are used to generate deviation fields that can be used to determine the deviation of the x, y, and z coordinates as a function of the motor angles. This empirical data is taken into account both in the simulation and in the creation of the control data in order to improve the positioning accuracy of the parallel kinematics.
As the project progresses, the aim is to increase not only two-dimensional positioning but also three-dimensional positioning accuracy. To this end, the relationship between the internal pressure of the continuum actuatorsCA and the resulting elongation will be examined in more detail so that this can be taken into account when generating the control data. Precompensation, which results from the combination of two-dimensional and three-dimensional empirical models, is intended to improve the mapping quality of the draping line and reduce potential placement defects. In addition to this precompensation, the coordinate data will also be used in a real-time control to further reduce shape deviations.
We would like to thank the Deutschen Forschungsgemeinschaft (DFG) for its financial funding of the project “Optidrap – Model predictive impedance control of pneumatic continuum actuators in the continuous wet draping process.”
