Marvell International Limited

Marvell Asia Pte., Ltd.

Takahiro Inoue

Kiyotada Ito

Foo Leng Leong

Takao Sugawara

Shinichiro Kuno

Methods and systems are disclosed for controlling fly-height of a read/write (RW) head. In an embodiment, a RW channel detects a servo gate signal and toggles a mode signal within a preamplifier from a RW data mode signal to a fly-height control (FHC) mode signal. In response to the FHC mode signal, the RW channel transmits FHC data over a differential interface to the preamplifier.

Differential interface transmission of fly-height control data

Methods, systems, and computer program products for compensating unstable linear time-invariant due to input nonlinearities are described. In one implementation, compensating a controlled device may include controlling the controlled device using feedforward control. In another implementation, compensating the controlled device may include controlling the controlled device using feedback control.

Controller and design support apparatus

In some implementations, a method includes receiving rotational speed information corresponding to a rotational speed of a spindle motor having a plurality of poles, down sampling the rotational speed information to obtain speed-related information associated with the spindle motor, and adjusting the rotational speed of the spindle motor based on the speed-related information.

Down sampling method for hard disk speed control loop

Systems, methods and computer program products for removing speed adjustment errors attributed by pole asymmetry are described. In some implementations, the spindle motor speed can be down sampled. Down sampling the spindle motor speed can include determining the spindle motor speed every two (or multiple of two) electrical cycles. Determining the spindle motor speed every two electrical cycles can lead to an accurate determination of the actual spindle motor speed, as the timing and position differences between two adjacent poles can be equalized (e.g., timing and position errors associated with the second pole can be used to cancel out the timing and position characteristics errors with the first pole).

A system including an error signal generating module to generate an error signal based on (i) back electromotive force sensed from a motor and (ii) a predetermined speed of the motor. The error signal includes noise due to mismatched poles of the motor. A noise elimination module eliminates components of the noise having frequencies N times a frequency of rotation of the motor from the error signal and generates a corrected error signal, where N is an integer greater than or equal to zero. A control module generates a first control signal based on components of the corrected error signal, generates a second control signal based on components of the error signal, and rotates the motor at the predetermined speed based on (i) the first control signal and (ii) the second control signal. The components of the corrected error signal have higher frequencies than the components of the error signal.

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Chigasaki, Japan

Takahiro Inoue