Hitachi Global Storage Technologies Netherlands B.v.

Hitachi, Ltd.

Yoshio Soyama

Masahito Kobayashi

Yuji Hata

Takashi Kouno

Toshihiro Arisaka

Masahiko Sega

Hidehiko Numasato

Shinsuke Nakagawa

Katsumoto Onoyama

Iwao Oshimi

Akio Shioya

Kiyotada Itou

A magnetic disk drive is to be provided wherein oscillations in thrust, conical and translational modes of a spindle caused by disturbance are to be damped to diminish a positioning error and thereby attain a high recording density and improved accessing performance. In one embodiment, there is provided a compensation circuit using acceleration or angular acceleration sensors, the sensors being disposed on a base, a cover or a PCB (printed circuit board) of a magnetic disk drive so that they can detect disturbance effectively, and wherein a mechanical system transfer characteristic of and other parameters in thrust, conical, or translational mode of a spindle are acquired or calculated by a processor and unnecessary oscillation in each mode is compensated. In another embodiment, to measure a transfer characteristic of the spindle in thrust mode and other parameters after installation of the magnetic disk drive in a case, piezoelectric elements are provided as one of oscillating means. The measurement may be made repeatedly at predetermined intervals.

Magnetic disk drive with compensation against disturbance

Embodiments of the invention lower the servo sector's share of each track and ensure that servo sector numbers are reliably determined. According to the embodiment, in the servo sector number (SSA) section of each servo sector, servo sector number information whose bit length (k bits) is shorter than the bit length required to express the servo sector number itself is preliminarily written. The servo sector number of each servo sector is determined by using the servo sector number information in m successive servo sectors, that is, a total of m&#xd7;k bits of information. Note that they satisfy the m(2&#x2212;1)&#x2266;N relation where N denotes the total number of servo sectors per track.

Servo sector in magnetic disk drive

In one embodiment, a magnetic disk apparatus comprises a magnetic disk for recording information; a magnetic head that reads information from, or writes information to, the magnetic disk; an actuator device that drives the magnetic head; and a control system that controls the driving of the actuator device. The actuator device is configured by a dual stage actuator comprising a fine actuator that drives the head and a coarse actuator that drives the magnetic head together with the fine actuator. The control system includes a fine controller that generates an operational value for driving the fine actuator and a coarse controller that generates an operational amount for driving the coarse actuator. The control system includes a mechanism for smoothly changing the operational amount generated by the fine controller immediately before saturation resulting from an applied voltage limit of the fine actuator or at the time the fine actuator returns to a control range from the saturation.

Magnetic disk apparatus with dual stage actuator

In a magnetic disk drive that performs the seek operation of a magnetic head by a VCM, a characteristic that is excellent in fault tolerance that will not generate a fault in severe environment, such as a high temperature and the issue of high frequency command without requiring a special device and special operation and without deteriorating access performance. For this purpose, a VCM current and a VCM voltage are measured and VCM back electromotive force is calculated based on both results. At seek operation, position information located on a magnetic disk is sampled and a traveling velocity is detected from the difference of the sampled result. VCM coil temperature is estimated from the difference between the traveling velocity and the VCM back electromotive force. The magnetic disk drive moves low velocity seek mode when the estimated value of this VCM coil temperature exceeded a specified value.

Magnetic disk drive and control method thereof

A disk apparatus has a position signal detector for detecting the position of a head with a specified sampling period, a controller operating a manipulated variable to control positioning of the head using a microprocessor and a digital/analogue converter with which the manipulated variable is converted. At least one or more timing registers set the timing of the conversion carried out by the D/A converter and at least one or more manipulated variable registers set a manipulated variable that is converted into digital/analogue form at the set timing. In addition, the controller has advancing means to make a target position trajectory advance towards a specified time, a feedforward controller to receive the output of the advancing means and to calculate a feedforward control variable on the basis of a target trajectory, and a feedback controller to produce a feedback output variable on the basis of a target trajectory that is delayed relative to a target position trajectory by a specified time.

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Kanagawa, Japan

Yoshio Soyama