Modeling and control for self-servowriting in hard disk drives: a repetitive process approach

This paper considers modeling and correction signal design for self servo writing in disk drives. Self-servowriting is a process whereby the position and timing burst information are written on the disk surface by using the servo information from a previously written track as a reference (seed) for writing the burst information on a subsequent track, and repeating the process. An obstacle to this process is radial error propagation, whereby the distortion in the successive written tracks builds up. In this paper, a reference correction signal is designed which when added to the position error signal (PES) prevents the radial error propagation. The design of the correction signal is carried out through a repetitive systems approach and does not require several revolutions of track following in order to compute it. The analysis is verified by means of simulations which show the containment of radial error propagation.