Method For Determining Reduced Tolerance For Future Mechanical Shock In A Disk Drive
Original Publication Date: 2002-Sep-30
Included in the Prior Art Database: 2003-Jun-20
Disclosed is a method for determining if excessive movement of the heads and disks in a disk drive has occurred and for predicting whether any additional movement can be tolerated without loss of servo function. The user can be warned that backup of the data is recommended. Disk drives, particularly those used in laptop computers, are exposed to mechanical shocks that can cause the heads and disks inside to move relative to each other. For disk drives using sector servo and more than one disk, it is important that the data tracks on each disk not move relative to the data tracks on the other disks after the drive has been manufactured. If movement does occur, there may be a longer time delay when the active head must switch from one disk to another. In severe cases there may be a complete loss of servo function. When one disk moves radially relative to another after manufacturing due to mechanical shock, the difference between the corresponding tracks on each of these disks is sensed by the servo system as a one-period AC signal. This type of AC difference can also be created when a centerline through the disks on the spindle becomes tilted relative to the axis of rotation of the spindle during the life of the disk drive. When one head shifts radially relative to another during the life of the disk drive due to suspension deformation, the difference between the corresponding tracks under each of these two heads is sensed by the servo as a DC offset. This type of DC difference can also be created when the axis of rotation of the actuator becomes tilted relative to the axis of rotation of the spindle.