Browsing by Subject "Roll-to-roll manufacturing"

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A computational fluid dynamics and machine learning study on web flutter during an oven drying process in roll-to-roll manufacturing
(2020-05-08) Ahmed, Muhammad Bilal; Li, Wei (Of University of Texas at Austin); Suryanarayanan, Saikishan
Fluttering of a web is a major problem during the oven drying process of roll-to-roll manufacturing. In this study, two-dimensional (2D) computational fluid dynamics (CFD) models were developed to understand the flutter phenomenon. The CFD results revealed meandering of air jets as a source of flutter through air-web interactions. The root mean squared pressure (P [subscript RMS]) and mean wall shear stress (τmean) were identified as reasonable measures of web flutter cause and web drying efficiency, respectively. Machine learning models were then trained using the results of CFD simulations. It was shown that machine learning models captured the underlying physics of CFD simulations and were able to make accurate predictions. Using the machine learning models, optimization of parameters was performed where several key design and process parameters of the oven were adjusted to reduce the web flutter while keeping the rate of drying unchanged. Optimization produced promising results that showed about 30% reduction in P [subscript RMS] or web flutter could be achieved. Results of optimization were confirmed to be accurate by performing further CFD simulations
Control of high precision roll-to-roll manufacturing systems
(2018-12) Zheng, Grant; Chen, Dongmei, Ph. D.
The flexible electronic industry has been growing rapidly over the past decade. One of the barriers to commercialization is the high cost of manufacturing micro- and nano-scale printed electronics using traditional methods. Roll-to-roll manufacturing has been identified as a method of achieving low cost and high throughput. A dynamic model of a roll-to-roll system is presented. In all roll-to-roll applications, tension and velocity must be accurately controlled to desired reference trajectories to ensure a quality finished product. Additionally, a registration error model is presented for the control design. Minimization of the registration is the primary objective for flexible electronics, but web tension and velocity cannot be neglected. The model is needed in order to formulate a methodology that can simultaneously control tension, velocity, and registration error in the presence of disturbances. Micro and nano-scale features are susceptible to damage from friction between the web and the roller. Therefore, tension estimation techniques is highly desired to eliminate load cells from the system. The reduced order observer, extended Kalman filter, and an unknown input observer is presented. Development of tension and velocity control strategies have historically revolved around decentralized SISO control schemes. In order to achieve higher precision, a centralized MIMO strategy is proposed and compared to decentralized SISO. The advantage of the MIMO controller improved handling of the tension velocity coupling in roll-to-roll systems. The tension observer is introduced to the control design and evaluated for overall effectiveness. In simulation, the centralized MIMO control with the unknown input observer demonstrated superior tension and velocity tracking as well as minimal registration error. Development of the proposed MIMO control strategy can enable flexible electronic fabrication using roll-to-roll manufacturing.