Abstract: A step-by-step electro-hydraulic servo system is presented for improvement of the head of band in a hot rolling mill for offering a cost saving. Including the position-adjusting loop and the pressure-adjusting loop, this system applies a simplified Hm mixed sensitivity algorithm to the closed-loop shaping. The core of the algorithm is to shape T, tire transfer function of the closed1 loop system, then the controller K is directly designed without selection of any weighting function, The result shows that with the algorithm, (lie Ha, controller obtained is effective for the step-by-step control system.

Key words: Mixed sensitivity Simplified algorithm, H∞ controller, Step-by-step control