Position error signal detection from the user sector for high position update rate in patterned media recording technology

Abstract

Achievable high recording track density in hard disk drives (HDDs) is often limited by the servo performance and the presence of disturbances and instability in the HDDs’ structures. For better servo performance, the position error signal (PES) sampling rate should be increased, as it is closer to the corresponding continuous time controller. However, the fixed number of servo sectors within the embedded servo system and the spinning speed limits the upper bound for the PES sampling rate. In this paper, a new PES detection strategy through direct measurement of the head position from the frequency-encoded user data channel is proposed in order to increase measurement accuracy and position update rate, in particular for embedded servo systems. Having a higher sampling rate will be very crucial in order to achieve more than the 1600 kTPI required for the 10 terabits per square inch areal density targeted by the Information Storage Industry Consortium (INSIC). The ability to extract positioning information within the user data sector will allow accurate read back and assist in writing processes.