Abstract: The subject invention uses a dither technique and a Discrete Fourier Transform to simultaneously align optical components along two axes orthogonal to the optic axis. The dither technique and the magnitude of the transmitted light are used to detect the misalignment in both directions simultaneously, and the Discrete Fourier Transform is used to detect the size and direction of the misalignment.

Abstract: A disk drive includes a voice coil motor (VCM) and a VCM power source circuit which is coupled to a standard power supply having a fixed voltage. During seek operations the VCM power source circuit provides a boosted voltage, greater than the fixed supply voltage, for the VCM. The VCM power source circuit provides the boosted voltage independently from the back EMF generated in the voice coil motor. The increased VCM voltage allows faster access times and more efficient VCM operation.

Abstract: A direct access storage device and a method of operation thereof where the output of the circuit which controls energy to the position actuator for the head may be changed at times between receipt of sequential position error signals from the medium. Instead of waiting for the next position error signal, a computation is done based on at least the current position and the desired position of the head as to when the head velocity will be equal to a desired velocity. The optimum time to switch is estimated, the energy required to achieve a predetermined velocity and a predetermined offset with respect to the desired position are computed, and operation is conducted accordingly. The amount of energy may again be changed at a time subsequent to the estimated time. The predetermined velocity and the predetermined offset may be zero or may have values other than zero in accordance with the requirements of the track following controller.

Abstract: In a disk storage device dedicated servo system, a reference track is written in the outer guardband of the servo surface and each of the data surfaces. Supplemental position error signal (PES) values are obtained from the difference of servo and data surface samples at a plurality of locations around the disk and stored for access during read/write operations. The supplemental PES values are combined with the dedicated surface PES values to yield a composite PES that more accurately follows the data track centerline of the disk surface being addressed. The supplemental PES values are also periodically updated. To provide a more accurate correction of the composite PES, two consecutive supplemental values are used and an interpolation is calculated to provide a continuously changing supplemental PES value for modification of each sector actuator drive pulse between the two current supplemental PES values.

Abstract: Disclosed is a method for performing a seek operation in a disk drive using current in the saturation mode to accelerate and decelerate the actuator arm. In a first embodiment, several measurements are made during the acceleration portion of the seek to estimate the deceleration available in saturation mode. In a second embodiment, the point at which the current is switched from acceleration current to deceleration current is adjusted based upon the position where the actuator arm comes within a desired amount of the velocity of a velocity profile assuming worst case conditions.

Abstract: A controller for a voice coil motor driven disk file actuator is described. The device has an online adjustable gain characteristic for controlling movement of the actuator assembly and an estimator that estimates actuator velocity and bias. Forward gain is estimated from position and coil current measurements and compared with a nominal value to create an error signal used to adjust the controller and estimator gain characteristics. The control technique allows changes in the open loop system without changing the closed loop performance. By monitoring loop gain it is possible to alter compensator gains to maintain a constant closed loop performance.

Abstract: A three level motor speed control for a device such as a magnetic disk drive requiring a closely regulated running speed provides for acceleration, deceleration, obtaining close speed regulation and maintaining speed regulation of a rotating device during operation. The first level control provides acceleration or deceleration while checking velocity each eighth revolution and the second level control uses single revolutions to measure speed over an accurate rotational distance to obtain close speed regulation. Both level one and level two are controlled by the device controller. During run conditions with no error signal, a third level of control of the closely regulated velocity is maintained by separate hardware circuits which frees the processor for other uses. An error condition forces control to level one for re-establishment of the regulated running speed and a command to stop the drive forces control to level one for deceleration and stop procedures.