Nec Corporation

Terumitsu Okamoto

Tomoaki Nakamura

Yoshihisa Okawa

Takeshi Ikemoto

Takamasa Kitano

After application of power or insertion of a medium, a frequency bandpass digital filter extracts the first-order component, which has one period per revolution of the medium, and the second-order component, which has two periods per revolution of the medium, from the carriage operation amount for one revolution of the medium, this being written into a carriage operation amount compensation table. Then, a position error averaging section calculates the average value of a tracking error signal, and a compensation table updating judgment section monitors this position error average value. If the position error average exceeds a prescribed threshold value for a number of consecutive sectors, the second-order component only is updated in the carriage operation amount compensation table. An actuator driving section controls the carriage in accordance with a corrected operation amount obtained by adding the operation amount obtained at the carriage operation amount calculation section and the compensation amount of the carriage compensation table. The results in stable position control of the head, without the influence of ambient temperature changes on the off-track amount.

Apparatus for driving an information recording medium and a method for

In an induction sensor for sensing the displacement of a movable body by electromagnetic induction, a scaler and a slider are each implemented as a hollow cylinder consisting of a plurality of conductors in the form of a coil. The conductors of each of the scaler and slider alternate with each other in a displacement sensing direction. The sensor can be assembled with a minimum of fine adjustment, eliminates wasteful areas, and provides the slider with high sensing accuracy without increasing currents to flow through the scaler.

Induction sensor responsive to a displacement of a movable body

A magnetic disk apparatus detects servo information on a magnetic disk which includes a plurality of concentric tracks which are provided with an alternate arrangement of data areas and servo areas. The apparatus includes a servo ID detecting circuit which generates a first detection signal when a servo area including an identification signal is detected and a data reproducing circuit which generates a second detection signal when read data pulses are detected on the signal reproduced from the magnetic disk. Sampling pulses are generated when the second detection signal indicates that the generation of read data pulses has terminated, while the first detection signal indicates the presence of the identification signal. The positional error of the magnetic head of the magnetic disk apparatus with respect to the target track of the magnetic disk is determined from the servo information of the signal reproduced from the magnetic disk in synchronism with the sampling pulses.

Magnetic disk apparatus having a circuit for detecting a position of

For controlling a relative position between a magnetic head (15) and a recording medium (10) having a control area (14) indicative of a tracking axis for the magnetic head, a position controlling unit comprises a producing arrangement (28) for producing a position signal, and a control arrangement (29) for controlling the relative position in response to the position signal in a predetermined direction which intersects the tracking axis. More particularly, the producing arrangement comprises a first producing, a second producing, and a processing arrangements (31, 32, 33). Responsive to the detection signal, the first producing arrangement produces a first signal. The processing arrangement processes the first signal into a second signal. Responsive to the first and the second signals, the second producing arrangement produces the position signal. Preferably, the control area has a main area (17) indicative of the tracking axis, and a supplementary area (18) preceding the main area. The magnetic head is for detecting the main and the supplementary areas to produce a main and a supplementary detection signal which collectively serves as the detection signal.

Exact position control of a relative position between a magnetic head

A circuit for controllably and finely driving a stepping motor, which moves a magnetic head over a magnetic disk, by using the combination of current values which are individually approximated to a sine wave and a cosine wave. The circuit allows a magnetic head to move at a high speed across the tracks of a magnetic disk toward a desired track, while after such a movement of the head lowering the remaining oscillation frequency of the stepping motor to allow servo to be applied immediately, thereby enhancing rapid operations of the apparatus.

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Tokyo, Japan

Terumitsu Okamoto