High-Precision and Fast Response Control for Complex Mechanical Systems - Servo performance of dedicated servo recording systems

The dedicated servo recording system for hard disk drives (HDDs) has servo bursts continuously stored in between data recording layer and the soft underlayer of conventional perpendicular magnetic recording media. It provides high sampling rate for the servo control of the mechanical actuation system, which is thus enabled to quickly respond to high-frequency vibrations and achieve high positioning accuracy. The servo performance of the dedicated servo HDDs is investigated by applying low-frequency external vibrations, and its advantages over conventional servo are evaluated and verified. Dual-stage actuation mechanism is further applied to enhance the servo performance for effective utilizing the high sampling rate for the servo control. The high servo bandwidth, such as 5 and 10 kHz, is then achieved with sufficient position error signal (PES) samples provided by the dedicated servo. Not only to the low-frequency vibrations, the servo control loop with the high servo bandwidth is also able to significantly reduce the audio vibration impact on the PES. Simulation and testing results are provided, in this paper, to study and verify the servo performance of the dedicated servo recording systems.