Velocity control apparatus for disk drive

Claim 1

Velocity control apparatus for a disk drive of the type comprising a recording disk rotatable about its axis, an electromagnetic read/write head for reading data from and writing data onto tracks on a surface of said disk, and means coupled to said head and responsive to velocity command signals for controlling the direction and speed of movement of said head relative to the axis of rotation of said disk in order to position said head over a desired track on said disk surface, said velocity control apparatus comprising: a memory divided into a plurality of sections respectively associated with different ranges of desired distances to be traveled by said head, each section containing a predetermined number of addressable storage locations having velocity command signals stored therein together defining an approximation of a desired velocity trajectory curve for a desired distance to be traveled included within the range associated with that section; first means for generating a first position signal representative of a particular desired distance to be traveled and a second position signal representative of a predetermined fraction of said particular desired distance to be traveled, said first means including means responsive to said first position signal for generating a trajectory index signal identifying the section of said memory associated with the range in which said particular desired distance lies; second means coupled to said first means and being responsive to said second position signal for generating a counting signal representative of the distance actually traveled by said head; third means coupled to said first means and to said second means and being responsive to said trajectory index signal and to said counting signal for applying an address signal to said memory means for sequentially addressing the addressable storage locations of the associated section of said memory during movement of said head said particular desired distance to be traveled thereby providing a sequence of said velocity command signals together defining an approximation of the associated desired velocity trajectory curve; and fourth means for coupling said velocity command signals to said means for controlling.