On CD coat weight control

Increasing demands for consistent print quality and higher production yields have generated strong interest in CD (cross direction) coat weight control. On a blade coater, the incremental gain between blade pressure and coat weight varies over time due to blade wear and changing operating point. Possible process control solutions to reduce CD coat weight variations on bent blade coaters are discussed, including a fixed-parameter Dahlin controller with a decoupling matrix, passive certainty equivalence adaptive control, and active suboptimal dual control. Simulations comparing those various schemes indicate the benefits of dual control