A hard disk drive that determines a saturation current of a voice coil motor (VCM) during the acceleration portion of a seek operation, and uses the information to advantageously adjust current profile for subsequent portion of the seek. One example of determining the saturation current is utilization of the peak value of the saturated acceleration current whose magnitude depends on operating conditions such as temperature and supply voltage. Traditional hard disk drives use predetermined seek current profiles that are formed conservatively to account for such variations in the available current to the VCM, at the expense of sacrificing some seek performance. By determining the available current for each seek operation, the current profile can be adjusted on the fly so as to improve the seek performance.

A method of controlling track seeking and track following of a head in a disk file having servo information recorded thereon to provide a track number and a position error signal (PES). The physical parameters of the disk file are modeled by at least three sets of constants associated with selected numbers of tracks. An actuator is connected to the head by a support arm assembly and is responsive to a control signal for positioning the head. The method comprises, for each servo information sample, the steps of predicting a relative position, velocity, and bias of a data head. It is determined whether the predicted relative data head position corresponds to the selected number of tracks, if not, at least the predicted relative data head position is rescaled to form the predicted relative data head position to correspond to the selected number of tracks of the predicted data head position prior to rescaling. The set of the one of at least three sets of constants is changed to correspond to the selected number of tracks of the predicted data head position prior to rescaling. A measured relative data head position is formed from the track number, the PES and the target track. An error in a relative data head position is estimated. A control signal as a function of the relative position error, the predicted relative position, the predicted velocity, the predicted bias, and the adjusted velocity, of the data head, is generated.

An improved method for compensating for the irregularity in the torque constant of the electric motor used to move the actuator arm carrying the magnetic read/write head in a disk drive is disclosed. The torque constant of the electric motor varies across the operating range on a given drive as a function of head location and the variation in torque constant is compensated for with a torque constant multiplier. The present invention provides a method for accurately determining the torque constant multiplier versus position function of a particular disk drive. In one embodiment, the method of the present invention includes the steps of: determining a nominal operating range for the location of a head over a disk for substantially all disk drives manufactured with the same manufacturing process; determining the offset of the operating range of a particular disk drive relative to the nominal operating range; modifying the location of the head, as determined by reading servo information, of the particular disk drive based on the offset; and obtaining the value of the torque constant multiplier associated with the modified head location.

Provided is a disk drive with a disk and an actuator assembly on which a communication device is mounted for communication with the disk. Position information read from the disk is processed through a channel that generates an analog position error signal that is then converted to a digital position error signal by a first signal converter. Based on the digital position error signal, a controller determines whether realignment of the communication device with the disk is required. The operation of the first signal converter is only periodically required. When realignment is required, then a digital position control signal is generated by the controller and is then converted to an analog position control signal by a second signal converter, which shares circuitry with the first signal converter. Normally, the second signal converter is operating to realign the communication device. Therefore, the shared circuitry is normally operating as part of the second signal converter. Operation of the shared circuitry between the first signal converter and the second signal converter is switched by a switch controlled by the controller. Based on the analog position control signal, a servo system causes the actuator assembly to reposition the communication device for fine adjustment to maintain proper alignment with the disk.

A spindle motor control method and apparatus for spindle motor control are provided for use in a direct access storage device. A plurality of operational modes of the direct access storage device are detected. The operational modes of the direct access storage device include start-up and idle operational modes and predetermined critical operational modes that include reading of data and reading of servo information. A pulse width modulation (PWM) mode control for applying driving current to the spindle motor is provided responsive to detecting a start-up or an idle operational mode. A linear mode control for applying driving current to the spindle motor is provided responsive to detecting one of the predetermined critical operational modes. During operation of the disk file, a small percentage of the overall file power-on time is spent performing critical file operations so that substantial power savings are achieved by the PWM mode control. Also since the integrity of the data transferred is critical, the error rate reduction that results by operating in the linear mode during the critical file operations is advantageous.