TMR Analysis and Controller Design for Self - ServoWriting in High-Density Hard Disk Drives

This paper analyzed and modeled the major contributors of track misregistration (TMR) in HDD self servowriting (SSW). Self servowriting is a process whereby the position and timing burst information are written on the disk surface by using the servo information from previously written tracks as seed tracks for writing the burst information on the remaining tracks. One of the most significant issues in this process is radial error propagation which is built up while successive tracks are written. These written-in disturbances are main source of the repeatable runout (RRO) which may greatly degrade the HDD servo performance. In this paper, in order to improve the SSW servo performance with higher density, we designed the servo controller by using loop shaping method which is able to achieve higher bandwidth and better error rejection. To minimize the radial error propagation, we further designed the feed-forward compensator using the identified disturbances models, to reduce the written-in RRO. Simulation results illustrate the capability of the proposed compensators