Use of Command Input Shaping Method to Compensate Clock/Seed Timing Track Closure in Phase Lock Loop

In all servo writing technologies used in hard disk drives industry, servo track propagation process has to be synchronized using clock/seed timing track in order to ensure proper alignment of the propagated servo patterns. Before the clock/seed timing track can be used to synchronize the servo propagation, clock/seed timing track closure must be guaranteed. Incorrect closure disturbs the operation of the phase-lock loop circuit and adversely affect the quality of the propagated servo patterns. This paper proposes a novel method for fast compensation of clock/seed timing track closure. The method is based on command input shaping technique. A compensation signal is injected between phase detector and low pass filter of the phase-lock loop circuit to compensate the clock/seed timing track closure. Experimental and simulation results verifying the proposed method are presented