International Business Machines Corporation

Arno Matla

Volker W Zimmermann

Horst D Matthaei

Karl Heinz Schaller

Helmut P Louis

Volker Zimmerman

For the servo track control of magnetic heads over magnetic tracks, in addition to the main servo position signals arranged in offset fashion to the middle of the track, auxiliary servo position signals are provided symmetrically on each side of the middle of the track. These auxiliary servo position signals are offset along the track length relative to each other and are smaller than half the track width. In the determination of the position error signal, they serve to indicate the tilting of the magnetic head relative to the recording track in that they are unequal. If the magnetic head deviates greatly from the middle of the track, these auxiliary servo position signals can be added to the main servo position signals to obtain a stronger position error signal. For determining and compensating uniform disturbance variables, the momentary values of a control signal are measured and a mean value is formed thereof which, at predetermined intervals, is added to a preceding mean value, stored, and entered as an additional control signal to the control path.

Servo track following control for magnetic heads, and method for

A daisy wheel spring disc utilized in conjunction with a daisy wheel print element to control impression. Both the spring disc and the print element have radially extending petals. The print element petals carry a character adjacent their outer extremity. A spring disc petal is associated with each print element petal for which impression is to be controlled. The spring disc petals vary in length relative to the print element petals. The lengths of the spring disc petals depend upon whether the character on the associated print wheel petal has a large or small print surface area. During printing, the spring disc is positioned on the printing side of the print element. When a print element petal is driven out of the plane of the remaining print element petals during printing of a character, the associated spring disc petal will be contacted and will absorb a portion of the energy imparted to the print element petal.

Apparatus for controlling impression in a daisy wheel printer

During the access mode of a movable magnetic head in a disk file, a program of position control signals is derived from a simulator, the input of which is clocked at sector time intervals. The position control signals of the simulator are periodically transferred to the summing point of a servo loop which successively is error conditioned, dependent on the subsequent nominal magnetic head positions derived from the simulator. Servo sectors on the data disk are sampled by the magnetic head, evaluated and converted to a digitally coded position error signal. The error signal is summed with a digital position control signal, and the output sum signal in analog form is applied to the motor that drives the head. The track following function is accomplished by means of a closed servo loop, which is also used in the access mode.

Servo system for track accessing and track following in a disk drive

In a signal storage apparatus employing a rotating record disk, the resonant frequency of a head carriage assembly is tuned to the rotational speed of the record disk. The head carriage assembly, in following a record track on the record disk, has to accommodate record disk rotational perturbations; i.e., run out, eccentric mounting, etc. Such variations are better accommodated in the head carriage assembly by electrically tuning the head carriage assembly to the rotation of the record disk. In a voice coil head assembly actuator, a pair of opposing coils carry equal current amplitudes. These equal current amplitudes are adjusted to rotational speed of the record disk to thereby continuously tune the head carriage assembly to the record disk rotation.

Disk storage apparatus having an electrically tuned head-carriage

The surface of a magnetic disk (23) is divided into servo sectors (S.sub.1) and data sectors (S.sub.2). A selectively positionable magnetic head (24) effects, in predetermined time intervals controlled by clock signals of a clock sensor (26), the transfer of servo and data signals. The servo signals sensed in the servo sectors are used for the track following control of the magnetic head. The servo markings (Ma) recorded in the servo sectors (S.sub.1) are arranged, with twice the width (2d) of the data tracks in radial distances of one respective track width (d), one beside the other in a row along a disk radius. In each servo sector at least three rows (A, B, C) of servo markings (Ma) are provided. The servo markings are arranged in track direction one behind the other in such a manner that between each of the rows (A, B, C) a distance (g) is formed, and that each servo marking of one row overlaps a servo marking of the following row by one track width (d).

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Waldenbuch, Germany

Arno Matla