Disk drive seeking to OD track and then ramping velocity to implement fast unload

摘要

A disk drive is disclosed including a disk having a plurality of tracks, wherein each track comprises a plurality of embedded servo sectors. A head connected to a distal end of an actuator arm is rotated about a pivot by a voice coil motor (VCM) in order to actuate the head radially over the disk. The actuator arm is unloaded onto a ramp by seeking the head to a track near an outer diameter of the disk in response to the embedded servo sectors, switching to a velocity control mode to unload the actuator arm onto the ramp at a controlled unload velocity in response to a back electromotive force voltage generated by the VCM, and ramping a velocity command so that the velocity of the actuator arm when contacting the ramp is less than half the maximum unload velocity while traveling along the ramp.