Polynomial solution of the standard H∞ control problem for strip mill gauge control

A solution to the standard H_∞ optimal control problem is presented which is particularly useful in machine control applications where the output to be controlled is different from the signal for feedback. The solution is obtained in polynomial form and the plant structure which is assumed represents a range of applications in the manufacturing and process industries. The results are applied to the design of a thickness-control system for cold-rolling mills subject to a range of disturbance noise inputs