Rejection of disk drive vibration and shock disturbances with a disturbance observer

Improving the position control of the disk drive read/write heads is an important step in increasing the storage capacity of a drive, especially in the presence of internal and external disturbances. To address this problem, the typical feedback loop of a disk drive servo system was augmented with a disturbance observer. The disturbance observer uses the position error signal and a nominal model of the plant to create an estimate of the disturbance. This estimate is then used to compensate for the disturbance effects. The effectiveness of the disturbance observer in rejecting shock and vibration disturbances is demonstrated in simulation and shake table experiments. The effects of noise in the position error signal are also discussed.