Abstract
An H∞ design method of a robust controller with tuning parameter is applied to a hard disk positioning control. On the gain diagram, sensitivity and complementary sensitivity functions can be moved along frequency axis by tuning parameter. A good system with sensitivity and robust stability being balanced adequately can be obtained by tuning it. Analytical solutions of Riccati equations which contain a parameter are required in the design. Since the plant transfer function has a special form of a/sn in this case, they can be easily constructed from numerical solutions of Riccati equations and it is not necessary to solve it analytically. This controller is compared with a fixed controller designed by a mixed sensitivity design method by simulation.
