Following control of a hard disk drive by using sampled-data H∞ control

In the head positioning control of hard disk drives, digital control is widely used. Therefore, if a small sampling period could be used, the performance obtained by the digital controller is not deteriorated compared with the one obtained by an analog controller. However, in hard disk systems, the sampling period cannot be chosen arbitrarily. Because it is determined by the another factor which is nothing to do with control requirements in most cases. We apply sampled-data H_∞ 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 intersampling behaviors. Experimental results show that good following performances can be achieved by the long sampling period