Adaptive Cancellation of Self-Induced Vibration

When a hard disk drive (HDD) performs track-seeking operations, mechanical vibration modes are often excited and the performance of the HDD is degraded. Unlike disturbances coming from outside of the drive, self-induced vibrations are excited by seek motions of the HDD, but they are amplified by internal and/or external mechanical modes of the HDD. A soft mounting mechanism of a HDD in a laptop PC to protect from externally-generated shock can be excited by seek motions and sometimes contributes to seek-settling vibrations. A method to cancel self-induced vibrations of the HDD using an adaptive technique without modifying the sensitivity function is presented in this paper. The vibration effects are cancelled by adding a vibration model in the servo loop. Since the vibration gain and frequency vary due to the properties of the soft mounting mechanism, an adaptive technique is developed to adjust the model in real-time to ensure robustness. Experimental results of seek settling waveforms and seek time variations show reasonable convergence speed and good suppression of the vibration effects.