Modeling and Control of the In-Situ Thermoplastic Composite Tape-Laying Process

In thermoplastic tape-laying with in-situ consolidation, a laminated composite is constructed by the local application of heat and pressure. A moving head, applying heat and pressure, lays down and bonds a new layer to the previously bonded layers (substrate). The temperature at the interface between the top ply and the substrate is critical to achieving interlaminar bonding. Recent research on the in-situ thermoplastic composite tape-laying process has focused on modeling, numerical analysis and experimental analysis, but little research has considered the control of this process. In this work, a method is proposed for modeling and control of in-situ thermoplastic composite tape-laying. The key to the control algorithm is predicting the temperature at the interface between the top ply and the substrate. Based on a process model, a state feedback controller and a state estimator for temperature are designed for closed-loop control using the linear quadratic method. Two different approaches are used to develop the process model for real-time closed-loop control through temperature feedback. In the first approach, a low-order lumped parameter model is constructed from a finite difference scheme. The second approach constructs an empirical model through system identification. The structures of the two models are identical, but the parameters differ. The experimental results have shown that the developed estimator and controller can accurately estimate and control the bonding temperature using temperature feedback indicating that the proposed modeling and control methodology can produce a high quality thermoplastic composite laminate.