A hard disk drive that has a reaction mass and a transducer that can be used
to
move and/or sense the acceleration of an actuator arm of the drive. The transducer
is coupled to a disk controller that can provide output signals which induce a
movement of the reaction mass. Movement of the reaction mass will cause a responsive
movement of a head(s) coupled to the actuator arm. The transducer can also provide
input signals to the controller that correspond to an acceleration of the actuator
arm. The acceleration signal can provide force feedback for a servo system of the drive.
