High performance digital servo design for HDD by using sampled-data H/sub /spl infin// control theory

In the head positioning control of hard disk drives, a digital control is widely used. Therefore, if a small sampling period could be used, the performance obtained by the digital controller is not so deteriorated compared with the one obtained by the analog controller. However, in hard disk systems, the sampling period cannot be chosen arbitrarily small, since it is determined by factors which have nothing to do with control requirements in most cases. In this paper we apply the sampled-data H/sub /spl infin// control synthesis to the head positioning control of the hard disk drive. This method enable us to design a desirable digital controller directly by taking into account of intersampling behaviors. Experimental results show that a good following performance can be achieved by the long sampling period.