Disclosed are methods and apparatus for digital control of a head-disk
assembly actuator with dynamic velocity compensation. In preferred
methods of the invention steps are disclosed in which, the actuator
voltage in an HDA is sampled and a velocity error is determined. The
voltage applied to the actuator is compensated for the velocity error.
Disclosed methods of the invention also include steps for measuring the
actual voltage at the actuator motor and alternatively, for calculating
the actuator motor voltage using digital processing techniques. A digital
voltage command is then provided for applying compensated voltage to the
actuator motor. Apparatus for implementing the methods of the invention
in a hard drive assembly having an actuator motor is also described. The
apparatus includes a sampler for sampling an actuator motor voltage, a
timer, and a digital processing engine for receiving a target actuator
voltage command and the digital actuator motor voltage sample and for
outputting a digital voltage command for controlling the actuator motor.