Disk Drive Operating Drop Shock Protection
Original Publication Date: 2001-Sep-13
Included in the Prior Art Database: 2003-Jun-20
Disclosed is a method that allows a disk drive to sense a free-fall condition and to place the heads in a safe position so that the drive will have the best shock protection available before the impending impact. This method is applicable to portable devices. It predicts when a shock is likely to occur and automatically puts the drive in the non-operational shock resistant state while the device is operating. By predicting the shock in the future, the drive can protect itself and have an operating shock specification equal to that of the non-operating specification under certain circumstances. Fortunately the situations that can be predicted are the normal situations and thus provide excellent coverage for portable devices. For disk drives that are used in portable devices, the operating shock specification is significantly less than the non-operating shock specification for disk drives. This difference is usually attributed to a head load/unload feature that separates the heads from the media so that they are less likely to collide in severe shock environments. The heads may also be 'parked' in special locations that are less susceptible to shock. During normal operation, the heads are 'flying' over the media where data is normally read and written. If a shock condition occurs, the head/media separation may be compromised and data loss can occur. Disk drives include accelerometers that can detect large shock conditions and will terminate a write operation if a large enough shock (acceleration) occurs. This prevents the drive from writing over adjacent tracks because the position of the head moves off-track due to the large shock. The accelerometer need only detect large enough accelerations that would cause such off-track conditions small changes in acceleration do not cause problems, so can be ignored. This shock protection does not allow the drive to sustain a shock as large as can be accommodated by the non-op shock protection where the heads are physically placed in a safer location.