| Microwave processing of composites in a single-mode resonant cavity using fixed frequency technology, was automated to advance the current state of technology by bridging the gap between device and process. Automatic hardware and software for controlling the non-linear and complex electromagnetic interactions during composite curing were developed. Efficient coupling, uniform and controlled heating were the control objectives which were achieved through mode switching, mode tuning, and power control.;The developed controllers were integrated into an overall closed-loop feedback control system that was implemented in a control program called LabView. Another control system was also built and demonstrated by interfacing with a knowledge-based system planner. The control systems were implemented in a newly designed automated cavity with novel mechanized drives and axial and radial mounted microwave coupling probes.;Composites curing showed that the ease and flexibility in operating the automated microwave process was comparable to automated thermal processes, although it contains extensive electronics and involves complex control tasks. Compared with the manually operated system, sample temperature gradients were reduced by 60%, mode switching times were reduced by 67%, mode tuning reproducibility was significantly improved and data acquisition was enhanced for processing and for diagnostics.;This marks a notable step in the advancement of the current state of technology; from that of a manual lab-scale device to a fully automated "First generation prototype" process. The application potential of this technology has been greatly enhanced by this development.;For mode tuning a non-traditional control methodology using a 2-dimensional simplex minimization method was used, and shown to be more efficient than manual univariate methods. In the development of the uniform heating controller theoretical empty cavity solutions were used to develop empirical correlations to characterize the loaded cavity. This was necessary to overcome the computationally intensive calculations required for solving loaded cavity equations for control purposes. Using these empirical correlations, mode switching for achieving uniform or controlled heating was constructed and shown to be highly effective. Power control was based upon traditional proprotional-intergal-derivative (PID) control methodology and shown to be more proficient than the previous on/off control. |
