An Identification Method of Seek-Induced Vibration Modes in Hard Disk Drives

A method to identify the transfer function of HDD actuator system modes that have gains that are smaller than the rigid-body mode is presented. Prony's 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 low frequency modes, such as the flexible printed circuit attached to the actuator.