Abstract: A method is disclosed for identifying wedge time shift zones on a magnetic disk of a disk drive. The disk drive further includes a spindle motor for rotating the disk at an operating speed in response to a spindle control current generated by a spindle control system, and a head that is actuated over the disk. During operation, the control systems causes a seek of the head across the disk and measures wedge-to-wedge times between servo wedges. The control system then calculates a wedge-to-wedge time shift value using the wedge-to-wedge times and determines whether the wedge-to-wedge time shift time value exceeds a predetermined threshold. If the wedge-to-wedge time shift value exceeds the predetermined threshold, then the control system identifies a wedge time shift zone, and stores information for compensating for the identified wedge time shift zone during disk operations.

Abstract: A disk drive is disclosed having hybrid spindle speed control. The disk drive includes a disk having a plurality of servo wedges, and a spindle motor for rotating the disk at an operating speed. The spindle motor generates a back electromotive force (BEMF) voltage. In operation, the disk rotation is maintained at the operating speed during a track following operation by updating, in a wedge spindle speed control mode, the spindle control current in response to a wedge speed error. Before executing a high-speed seek, the disk drive is switched to a BEMF spindle speed control mode, and the disk rotation is maintained at the operating speed during the high speed seek by updating the spindle control current in response to a BEMF speed error signal generated based on the BEMF voltage. During a seek-settle time, the disk drive is switched back to the wedge spindle speed control mode.

Abstract: A disk drive is disclosed comprising a disk having a plurality of tracks, a head actuated over the disk, and a voice coil motor for seeking the head from a first track to a second track. A first seek time is computed corresponding to a first seek profile, and second seek time is computed which is greater than the first seek time. A second seek profile is computed in response to the first seek time, the second seek time, and a scaling factor that accounts for a back EMF voltage generated by the voice coil motor. The voice coil motor is then controlled according to the second seek profile to seek the head from the first track to the second track.

Abstract: Disclosed is a disk drive including an actuator having a coil, a head attached to the actuator, and a disk including at least a first track and a second track, and a processor for controlling operations in the disk drive including a seek operation from the first track to the second track in which the head is moved between the first track and the second track by the movement of the actuator. The processor under the control of a program generates a deceleration velocity profile for the seek operation that is determined based upon a deceleration velocity profile function that includes a back electromagnetic force (BEMF) model to take into account back electromagnetic forces (BEMFs) associated with the coil of the actuator such that the BEMFs are mathematically modeled. The head is commanded to seek to the second track utilizing the deceleration velocity profile function that includes the BEMF model.

Abstract: A disk drive is disclosed employing either back electromotive force (BEMF) spindle speed control mode or wedge spindle speed control mode. A BEMF detector monitors the BEMF voltage generated by the windings of the spindle motor to generate a BEMF speed error. The BEMF spindle speed control mode is used to spin up the disk to an operating speed, and the wedge spindle speed control to maintain the disk at the operating speed. While in the wedge spindle speed control mode, a BEMF detection window is disabled to reduce acoustic noise.

Abstract: A disk drive is disclosed employing either back electromotive force (BEMF) spindle speed control or wedge spindle speed control. The BEMF spindle speed control is used to calibrate a reference time period representing an accumulation of a predetermined number of wedge-to-wedge times. During wedge spindle speed control, a wedge time period representing an accumulation of a predetermined number of wedge-to-wedge times is measured, and a wedge speed error is computed as the difference between the reference time period and the wedge time period.