Seagate Technology Incorporated

Otis L Funches

Randall D Hampshire

Lealon Ray McKenzie

Vladimir Kovner

Roy Lynn Wood

Ryan T Ratliff

Zhiqiang Liu

An apparatus and method for detecting rotational vibration applied to a disc drive having a rotary actuator adjacent a rotatable disc. The actuator supports a head adjacent a recording surface of the disc and an actuator coil in a magnetic field of a magnetic circuit of a voice coil motor. A second, velocity sense coil is further coupled to the actuator and immersed in the magnetic field of the magnetic circuit, with the velocity sense coil being electrically isolated from the actuator coil. Rotational vibration is detected in relation to a sense voltage induced across the velocity sense coil as the magnetic circuit is moved relative to the velocity sense coil. A data transfer operation between the head and a host device is interrupted when the magnitude of the rotational vibration exceeds a specified magnitude. A servo circuit applies current to the actuator coil to position the head relative to the disc recording surface in relation to servo information transduced by the head, as well as in relation to the sensed voltage from the velocity sense coil.

Rotational vibration detection using a velocity sense coil

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.

Object positioning using discrete sliding mode control with variable

Apparatus and method for improved positional control in a disc drive servo loop, wherein the actual velocity of rotary actuator is sensed from the motion-induced back-emf generated by movement of a coil of the actuator through the magnetic field of a voice coil motor. A current sense resistor is used in conjunction with the coil to provide closed loop control of the current applied to the coil. Signals indicative of the voltages across the serial combination of the coil and current sense resistor are provided to a velocity sense circuit, which determines the velocity of the coil by generating and subtracting out values for the dc voltage drops across the coil and the current sense resistor and the ac voltage drop across the coil. A compensation routine is provided to compensate for variations in temperature of the coil during operation. The sensed velocity of the coil is thereafter used in conjunction with other conventionally obtained measurements of estimates of head velocity to improve the accuracy and the reliability of the servo loop.

Velocity sensing using actuator coil back-emf voltage

A method for compensating for position and component induced variations in the acceleration and deceleration capabilities of a voice coil actuator in a disc drive, comprising the steps of dividing the discs radially into a plurality of zones, testing the acceleration and deceleration capability of the disc drive in each zone by performing specially controlled seeks in both inward and outward directions in each zone, comparing the result of these specially controlled seeks with a calculated nominal or desired result, and calculating a compensation factor for each zone which is applied by the servo system to all subsequent seek and track following operations.

Compensating for variations in torque capability of voice coil motors

Disc drive transducer deadbeat settle method utilizing interval

A method for effecting seeks of a transducer head across a data storage disk wherein the head is accelerated over a first sequence of time intervals and decelerated over a second sequence of time intervals. In each time interval of the first sequence, the head is accelerated in relation to the difference between the actual head velocity and a current demand velocity that is determined by incrementing the demand velocity for the previous interval by an amount that is a fraction of the difference between the previous demand velocity and a stored profile velocity selected in accordance with the current location of the head. In each time interval of the second sequence, the head is decelerated in relation to the difference between the actual head velocity and a stored profile velocity selected in accordance with the current location of the head.

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Oklahoma City, OK, United States of America

Otis L Funches