Disturbances to actuator control caused by external vibrations are
corrected using feed-forward techniques that are selectively enabled or
disabled based on signal values within a track follow loop. An increase
in data integrity and reliability may be achieved by reducing off-track
reads and writes caused by physical disturbances to disk drives during
operation. Accelerometers detect external forces imparted on a disk and
an acceleration feed-forward (AFF) signal is generated to compensate for
disturbances to the location of a head caused by such external forces.
Application of the AFF signal to an actuator may be based on whether
signal values along the track follow loop exceed a certain threshold.