Design of LMI-based H∞ servo controller for cold tandem mill

This paper is study on the design of H^∞ servo controller for a cold tandem mill, using LMI (linear matrix inequality)-based techniques. The controller improves the performance of AGC (automatic gauge control) system based on the Taylor linearized model of a cold tandem mill and satisfies robust stability, the restraint of disturbance and robust tracking property. The H^∞ servo control problem is modified as an usual H^∞ control problem, and the solvability condition of H^∞ servo control problem depends on the solvability of modified H^∞ control problem. But this modified problem does not satisfy standard assumptions for H^∞ control problems, it can be solved by using LMI techniques. Consequently, the comparison of the performance between the authors´ H^∞ servo controller and the existing PID/FF (feedforward) controller shows the usefulness of this study