Robust Decentralized Tension Control in Hot Rolling

Since tension control is the key to successful operations in the hot strip finishing mill, several advanced control schemes have been applied. A decentralized control scheme (Asano, et al., 2000), among them, has a practical structure that allows easy implementation to actual mills and has been in full commercial operation, but it showed oscillatory behavior in rolling operations of hard-to-roll strips. This paper investigates the cause for the degradation of the control performance and proposes an easy retuning procedure based on a robust stability analysis. Experimental results show that the decentralized control scheme can retrieve satisfactory control performance by adjusting only two control parameters, which exemplifies excellent maintainability of the control scheme.