Abstract: Method and apparatus for performing a seek operation to move a data transducing head from an initial track to a destination track on a rotatable recording surface. A servo control circuit operates to sweep the head across the recording surface. Servo data from an intermediary track are transduced to obtain a detected angular position value for the head with respect to the recording surface. When the detected angular position value differs from a predicted angular position value for the head, the servo control circuit initiates an index qualification routine at the conclusion of the seek. The qualification routine involves transducing the servo data from the destination track to verify the accuracy of the predicted angular position value. In this way, the effects of spurious (false) index signals obtained from the servo data transduced during the seek operation are minimized, and unnecessary reinitializations of the servo control circuit are avoided.

Abstract: Method and apparatus for reducing and dispersing wear to the surface of a rotatable disc in a disc drive using an adaptive dither process. The disc drive includes an actuator assembly that is secured in a parked position by a latch when not in use. The method includes determining an open latch current required to open the latch as the actuator assembly is moved from the parked position to a position over a user data storage portion of the disc. A dither current is subsequently applied to the actuator assembly to induce a reciprocating lateral displacement of the actuator assembly when the actuator assembly is secured in the parked position, wherein the maximum amplitude of the dither current is selected to be less than the open latch current.

Abstract: Method and apparatus for performing a seek operation to move a data transducing head from an initial track to a destination track on a rotatable recording surface. A servo control circuit operates to sweep the head across the recording surface. Servo data from an intermediary track are transduced to obtain a detected angular position value for the head with respect to the recording surface. When the detected angular position value differs from a predicted angular position value for the head, the servo control circuit initiates an index qualification routine at the conclusion of the seek. The qualification routine involves transducing the servo data from the destination track to verify the accuracy of the predicted angular position value. In this way, the effects of spurious (false) index signals obtained from the servo data transduced during the seek operation are minimized, and unnecessary reinitializations of the servo control circuit are avoided.

Abstract: Method and apparatus for controlling a motor below a threshold velocity. During a velocity control mode, the motor is accelerated to an operational velocity, receives a commanded velocity value, and switches from a first control method to a second control method below the threshold velocity. The threshold velocity is determined from limitations of control electronics that do not function well when a motor current drops below the threshold level. The sliding mode control method measures the measured motor velocity, compares the velocity to the commanded velocity, applies a current value when the measured value is less than the commanded value and applies a negligible current value when the measured value is greater than the commanded value. The threshold level is dictated by the first control method. Back electromotive force (bemf) detection circuitry is used to measure the motor current.

Abstract: Method and apparatus for reducing and dispersing wear to the surface of a rotatable disc in a disc drive using an adaptive dither process. The disc drive includes an actuator assembly that is secured in a parked position by a latch when not in use. The method includes determining an open latch current required to open the latch as the actuator assembly is moved from the parked position to a position over a user data storage portion of the disc. A dither current is subsequently applied to the actuator assembly to induce a reciprocating lateral displacement of the actuator assembly when the actuator assembly is secured in the parked position, wherein the maximum amplitude of the dither current is selected to be less than the open latch current.