Seagate Technology Incorporated

Zhiqiang Liu

Randall D Hampshire

Otis L Funches

Apparatus and method for attenuating effects of externally generated vibration applied along multiple axes of a disc drive. The disc drive includes a disc with a recording surface, a read/write head and a servo circuit which detects and corrects head position error. The servo circuit determines a plant estimate indicative of transfer function response of the disc drive while the disc drive is operated off-line. A sensor network concurrently generates a plurality of acceleration signals each along a different axis of the disc drive and indicative of a different component of the externally generated vibration applied along the corresponding axis. An adaptive filter network adaptively filters the acceleration signals to generate a compensation signal. The compensation signal is fed forward to the servo circuit to remove the effects of the externally generated vibration.

Adaptive attenuation of multi-axis vibrational disturbance

Apparatus and method for reducing the generation of acoustic noise in a disc drive. A seek is carried out to move a head from an initial track to a destination track on a corresponding disc surface using a servo circuit which outputs a series of current command values indicative of successive magnitudes of current to be applied to an actuator motor. A velocity profile provides a sequence of demand velocities indicative of the desired velocity as the head is decelerated to the destination track. During the seek, open loop current is applied to the actuator motor to accelerate the head away from the initial track, the current command values defining a rising portion wherein the current is successively increased to a first level and a subsequent falling portion wherein the current is successively decreased to a second level, the rising and falling portions each preferably characterized as a one quarter sine wave at a selected frequency. The head is subsequently decelerated to the destination track by applying current in relation to velocity error determined as the difference between the velocity profile and the actual velocity of the head.

Current profile shaping to reduce disc drive seek time variation and acoustic noise generation

An apparatus and method are disclosed for minimizing settling time in a disc drive servo system. The disc drive includes a head adjacent a rotatable disc on which a plurality of tracks are defined and a motor which controllably positions the head in response to current applied to the motor. A servo circuit is provided to settle the head onto a destination track at the conclusion of a seek operation by determining velocity of the head at a selected distance from the destination track, comparing the velocity to a desired velocity of the head at the selected distance from the destination track, adding a settling gain to a current command signal to generate a modified current command signal in relation to a difference between the velocity and the desired velocity, and using the modified current command signal to settle the head onto the destination track. The addition of the settling gain serves to add an additional zero to the response of the servo circuit, with the placement of the zero preferably determined in relation to a weighting of the locations of the closest two poles of the response.

Minimizing settling time in a disc drive servo system

Apparatus and method for improving vibration and mechanical shock response of a system through the use of discrete-time sliding mode control with variable parameters are disclosed. A servo circuit for positioning a control object (such as a head of a disc drive) includes a reference generator generating position and velocity references, an observer generating position and velocity estimates, and circuitry for determining position and velocity errors therefrom. Variable position and velocity gains are applied to the position and velocity errors, respectively, the position and velocity gains varying with respect to at least the magnitudes of the position errors.

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Oklahoma City, OK, United States of America

Zhiqiang Liu