Robust Tension Control of Strip for 5-Stand Tandem Cold Mills

Tandem cold rolling process is a nonlinear complex system with external and internal uncertainties and significant disturbances. The improvement in the quality of the final output depends on the control strategy of centerline thickness and interstand tension. This paper focuses on interstand tension control problem in 5-stand tandem cold rolling mills. Tension dynamics can be described by a nominalmodel perturbed by parametric uncertainties. In order to overcome themodel uncertainties and external disturbances, suboptimal.H-8 and mu controllers are proposed and the Hankel-norm approximation is used to reduce the order of mu controller. The performance of the proposed controllers is demonstrated by some simulations.