Timing Error Compensator Design for Self-Servowriting System in Hard Disk Drives

In Self-Servowriting (SSW) process, an accurate timing system is required for propagating the servo patterns. The timing jitters in this process induce significant timing error propagation in both radial direction and circumferential direction. In this paper, a control scheme based on Adaptive Feedforward Compensation (AFC) is proposed for SSW timing control loop. An adaptive filter is designed to minimize the closure error along circumferential direction and contain the timing error propagation along radial direction. The Filtered-X Least Mean Square (FXLMS) technique is used to design the adaptive filter. Simulation results prove that the proposed control method has achieved its objectives.