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Identification and cross‐directional control of coating processes
Author(s) -
Braatz Richard D.,
Tyler Matthew L.,
Morari Manfred,
Pranckh Ferdinand R.,
Sartor Luigi
Publication year - 1992
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690380903
Subject(s) - coating , controller (irrigation) , control theory (sociology) , noise (video) , actuator , process (computing) , model predictive control , substrate (aquarium) , process control , limit (mathematics) , perpendicular , computer science , identification (biology) , control engineering , control (management) , engineering , materials science , mathematics , nanotechnology , artificial intelligence , mathematical analysis , oceanography , geometry , botany , geology , agronomy , image (mathematics) , biology , operating system
Of special industrial interest is the cross‐directional control of coating processes, where the cross direction refers to the direction perpendicular to the substrate movement. The objective of the controller is to maintain a uniform coating under unmeasured process disturbances. Assumptions that are relevant to coating processes found in industry are used to develop a model for control design. This model is used to derive a model predictive controller to maintain flat profiles of coating across the substrate by varying the liquid flows along the cross direction. Actuator constraints, measurement noise, model uncertainty, and the plant condition number are investigated to determine which of these limit the achievable closed‐loop performance. From knowledge of how these limitations affect the performance we can make some recommendations on how to modify the plant design to improve the coating uniformity. The theory developed throughout the article is rigorously verified through experiments on a pilot plant. The controller rejects disturbances with two sampling times. The proposed controller can reduce the variance in coating thickness by as much as 80% compared to what is possible by manual control or simple control schemes.