State-space solution of the standard H∞ control problem for strip mill gauge control

The main purpose of this paper is to design multiloop H, controllers for a strip mill gauge control system. The two-Riccati statespace approach is applied to design H, controllers for both the inner loop (roll force feedback loop) and the outer loop (strip gauge loop). To avoid order propagation of the outer loop controller, a model reduction method is applied after the design of the inner loop is completed. The plant considered in this paper is ihe same as that considered by Grimble in 1995, but the design approach is different. In addition, the advantages of using a multiloop strategy (using both roll force measurement and gaugemeter feedback) are illustrated.