Thesis/Dissertation

In roll-to-roll processes the presence of non-ideal elements, such us out-of-round or eccentric rollers is fairly common. Periodic oscillations in web tension and web velocity are observed because of the presence of such non-ideal elements. Models of web transport on rollers based on the ideal behavior of various machine elements are not able to reproduce these oscillations in model simulations but can only follow the average of the measured tension and velocity signals. In order to reproduce the tension oscillations the models have to be modified to include the mechanism that creates the oscillations.

This research presents a control algorithm for the cooperative control of unmanned mobile robots. The algorithm relies on continuously solving an open loop mixed integer linear programming optimization problem. Since the model can become quite complex when the number of robots and the complexity of the environment increase, computational problems can arise. To overcome these problems an approach involving a hierarchical decentralized formulation of the optimization problem is proposed.

Print registration in roll-to-roll (R2R) printing process is investigated in this dissertation. Print registration is the process of aligning multiple images that are printed in consecutive print units. The quality of the print output depends on the proper alignment of these images. A new mathematical model for print registration is developed by considering the effect of key process variables, such as web tension and transport velocity, print cylinder angular position and velocity, and the compensator roller position. Sources of machine induced disturbances and their effect on print registration are also investigated and machine design recommendations to mitigate these disturbances are given. Propagation of disturbances between print units due to web transport is investigated. The interaction, or the disturbance propagation behavior, between print units is studied by developing a new interaction metric called the Perron Root based Interaction Metric (PRIM). The new interaction metric, for large-scale interconnected systems employing decentralized controllers, is developed using tools from the Perron-Frobenius theory. A systematic procedure to minimize interaction is given by designing pre-filters for decentralized control systems. The disturbance propagation behavior with two registration control strategies is compared using the PRIM and it is found that a compensator based registration control (CRC) has smaller magnitude of disturbance propagation when compared to a print cylinder angular position based registration control (PARC). It is also found that a simple, decentralized, memoryless, state feedback controllers stabilizes print units with CRC. Results from a number of model simulations and experiments are provided to support the recommendations and conclusions.

The term web is used to describe materials which are typically manufactured in a roll-to-roll manner. A wide variety of materials such as textile, paper, plastics, composites and metals are manufactured in rolled form because roll-to-roll manufacture of materials is convenient for transport and storage, saves time and reduces costs. As the web is transported in the processing machinery, inherent machine misalignment and process induced disturbance cause lateral fluctuations. These lateral fluctuations, if not controlled, can result in inferior quality of the finished product. The primary focus of this research is on the development and implementation of adaptive control strategies for controlling the lateral fluctuations (lateral control or lateral guiding) in a web processing line. New performance measures which can better assist machine operators in diagnosing lateral behavior were also investigated. A novel model reference adaptive controller, which is referred to as the ``Guide Adaptive Controller'' (GAC), was developed for web guiding applications. The GAC was implemented on an experimental web line and the performance of the controller was compared with an existing industrial controller. The adaptive control strategy resulted in better performance compared to an industrial controller especially when used with difference web materials with opacity and gage variations. Compared to the existing industrial controller, the adaptive controller does not require re-tuning when the operating conditions change because the GAC adapts to process variations and attenuates disturbances. Additionally, the same adaptive controller can be used with different guide mechanisms. Two simplified approximations of GAC were also developed and implemented on an experimental web line in order to observe the adaptive behavior of the controllers. Based on these observations a systematic procedure for industrial implementation of the adaptive control strategy was developed. Extensive experimental results on commercial guides with different operating conditions and disturbances indicate that GAC can provide improved guiding performance when compared to an existing industrial controller. Therefore, GAC has a high potential to successfully replace existing guide controllers. A novel performance metric which provides a better characterization of the guiding performance when compared to existing metrics was developed. The developed metric is based on histograms. Commonly observed histograms were studied and their occurrence in web guiding applications were analyzed. The performance metric can be used as a diagnostic tool in the web processing industry to monitor the occurrence of different machine and process induced disturbances, and also to compare controllers.