Improved Coordinated Response and Disturbance Rejection in the Critical Sections of Paper Machines

Critical sections of paper machines like presses, size presses, on-machine coaters and reels are required to undergo through eventually large and fast load changes, while maintaining the ongoing sheet tension as constant as possible to avoid wrinkling or breaks. This paper evaluates two disturbance rejection control techniques, one using disturbance feedforward (or disturbance input decoupling) based on a nip pressure disturbance observer, and the other using a 2-dof controller. Evaluations were done in both a press section and a size press section of lightweight paper machines and results showed that both methods are very effective reducing the maximum speed deviation to about 10% of the values without compensation, and that can operate combined with torsional oscillation compensation without interference between them