Practical estimation of CD control performance. I

Abstract

Summary form only given. Sheet and web forming processes cover a wide range of industries. A common aspect of all of these manufacturing processes is the spatiotemporal characteristics of the web with correlated multidimensional behavior. Both the design and performance assessment of cross directional (CD) controllers are current research and development interest especially since the commercial introduction of full width sensors that provide online mapping of complete sheet property profiles. CD controllers can regulate process variability. A model based minimum variance estimation for CD control will be proposed. In addition to measured data, process characteristics including slice (actuator) behavior and constraints will be considered to design an "optimum" controller to minimize variance under similar disturbance conditions. As "perfect" CD controllers cause picketing of the actuators, minimum or optimum variance will be defined in terms of practical limits and constraints. Additional metrics measuring transient CD correlations will be proposed and tested to track control effectiveness.