Control design for self servo track writer using estimation of the head position

In the production process of hard disk drive (HDD), there is a process of writing servo signals on magnetic disks to move the head to target address. However, such a servo track writer takes a longer time to draw servo signals because of the recent increase of the capacity of HDD. Therefore, a low-cost method to draw servo signals is desired. In order to resolve the problems, SSTW method (self servo track writing) which draws servo signals with its own head was suggested. In the SSTW method, there are two problems to realize it. One is how to know where the absolute position of head is. The other is that written servo tracks diverge because gain of the feedback controller is higher than 0 [dB] in high frequency domain. In this paper, the problems of SSTW are summarized and past work proposed by Bando and Hori (2004) is introduced. This method is essentially different from other methods, and performance is dramatically improved. The main ideas of this method, namely the estimation of the head position and the design of feedforward input, are introduced and simulation results are shown