Sag feedback based multi-roll coordinating optimal control of a low-tension roll-to-roll system

Abstract

The roll-to-roll (R2R) system is crucial for manufacturing low-strength sheets. And the speed control of rolls in this multi-roll system has a significant influence on the quality of the fragile sheets. However, the previous system with tension-based feedback control methods might crack the low-tension sheets during transportation. And few studies have carried out other effective control strategies for the R2R system. In this paper, the sag of sheets between rolls is chosen to be the feedback quantity, which provides a low-tension condition. A multi-roll coordinating optimal control method for the R2R system is introduced to keep sags stable by adjusting rolls’ speeds when the linear velocity of the upstream roll changes. A multiple-input multiple-output (MIMO) linear-quadratic-integral (LQI) controller is designed for the system. Several simulations and experiments are performed to confirm its validity. The effects of the hyperparameters in the proposed controller are also investigated. Compared with the series single-input single-output (SISO) PID control method, the proposed control method does better in reducing the speed fluctuation and eliminating error propagation and amplification in the low-tension R2R system. This control method and controller meet the needs of manufacturing low-strength sheets and show potential in enhancing the performance of the R2R system.