interaction analysis

Interaction in Decentralized Control Systems: Application to Roll-to-Roll Systems

A procedure to analyze interaction in an experimental roll-to-roll system that uses a decentralized control strategy is presented in this paper. A Perron root based interaction metric is employed for the analysis. Experiments conducted on a roll-to-roll system are used to evaluate the interaction between different subsystems of the roll-to-roll system. To minimize interaction between subsystems of the roll-to-roll system, a procedure for designing pre-filters based on the Perron root of the system is also discussed in the paper. Experimental results with and without pre-filter clearly indicate the effectiveness of the pre-filter in minimizing interaction. Discussions regarding the roll-to-roll application, stability considerations and insights on using the Perron root based interaction measure for decentralized control applications are also given.

Modeling, Analysis and Control of Print Registration in Roll-to-Roll Printing Presses

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.

Interaction Analysis of Control Systems Employed in Roll-to-Roll Printing

Roll-to-roll (R2R) machines have been extensively used to manufacture a wide variety of consumer products, such as paper, plastics, textile, etc. R2R machines facilitate continuous processing of materials with minimal stoppage time and provide significant improvement in productivity over batch manufacturing. With recent advances in technology it is now possible to manufacture flexible electronics, flexible digital displays, solar films, etc., using R2R processing. R2R processing of flexible electronics requires better understanding of machine and process dynamics to achieve tight tolerances required in their manufacturing. One of the conventional R2R processes that is critical to enable R2R processing of flexible electronics is printing. In this paper, machine and process dynamics for R2R printing are studied in detail. Specifically two control configurations, depending on the type of control input, are analyzed; a compensator based registration control strategy (CRC) typically used with mechanical line shafts (MLS) and a print cylinder angular position based registration control (PARC) strategy used typically with electronic line shafts (ELS), are compared. A comparison of these strategies is given based on a dynamic model for the print section, which includes governing equations for strain in the material, print cylinder velocities, and registration error (a metric that quantifies print quality). An interaction metric is used to analyze interaction of key process variables between print units. Model simulations are conducted for different scenarios to evaluate the strategies. Results of the model simulations are presented and discussed.