Error Propagation Suppression in Self-servo Track Writer by Time-domain Control Design

Control design of Self-servo Track Writer (SSTW) has become an important issue in Hard Disk Drive research. This paper discusses the error propagation problem in SSTW control. Although the Iterative Learning Control (ILC) has been suggested as a solution to suppress the error propagation in SSTW, existing suggestions design controllers in the iteration domain requiring considerable computation and complicated optimization algorithm. For this reason, this paper suggests SSTW control design in the time domain. First, reference correction to suppress the error propagation is suggested based on the error propagation study and a novel reference correction is suggested to control the amount of the converged error. Then, a state space approach is suggested developing a Kalman filter to estimate the absolute head position. The state space based design is extended and provides a formulation for a more general time-domain design of SSTW control.