Tetsuo Semba

AN IDENTIFICATION METHOD OF SEEK-INDUCED VIBRATION MODES IN HARD DISK DRIVES

Abstract A method to identify the transfer function of HDD head/actuator system modes that have gains that are smaller than the rigid-body mode is presented. Pronys method is used to identify the frequency and damping of the modes, and the measured actuator current and PES in the time-domain are used to identify the gain of the transfer function of the modes. Overall accuracy is verified by comparing the measured PES and the estimated PES by the obtained transfer function. Seek simulations are performed that demonstrate that modes which cannot be identified by frequency domain analysis have a significant influence on the seek-settling characteristics. It is also shown that although a smooth actuator current helps to reduce the high frequency vibrations at settling, it degrades the effect of vibrations due to the coil and other low frequency modes, such as the dynamics of the flexible printed circuit attached to the actuator.

Optimal Trajectory to Minimize Mechanical Vibration for Fast Positioning

Input shaping techniques have been proposed to reduce the vibration in the positioning of the manipulators. However, a practical application is not simple as the target requirements becomes more precise, because the number of mechanical resonances that need to be taken into account increases, and the robustness against the resonant frequency variations is more critical. The vibrations of the positioning at the final state are easily estimated by the plant transfer function and the jerk waveforms at acceleration, deceleration, and settling. The optimal control input for faster positioning can be obtained by minimizing the width of the jerk and minimizing the mode excitations at the same time. This optimization process can be performed by an adaptive filtering technique. It is based on the least-square algorithm, which generates the jerk waveform that minimizes the least-square sum of the vibration only at the settling. Effectiveness of the method is demostrated by computer simulations and the results for a hard disk drive application are also presented.© 2006 ASME