International Business Machines Corporation

Volker W Zimmermann

Arno Matla

Horst D Matthaei

Rainer Zuehlke

Gottfried Andreas Goldrian

Richard C Schneider

Armin Bohg

Ludwig Fischer

Hartmut Ulland

David C Graves

Wilhelm G Spruth

Walter H Sakmann

Claus Schuenemann

Helmut H Weis

Heinz Lutz

Karl Heinz Schaller

Bastian Bechtle

Gisbert Skudelny

A type band for a printer comprises a track of marks to be scanned (timing marks) at least one of which is obliquely positioned relative to its adjoining marks. The centers of all marks are equidistantly spaced. When the horizontally moving type band is vertically displaced, the time spacing of the scanning signal of the obliquely positioned timing mark is changed over the scanning signal of its adjacent timing mark. The magnitude of the vertical displacement of the type band is derived from the change in this time spacing. The displacement data thus obtained permit compensating for the vertical displacement of the type band (using, for instance, a stepper motor).

Revolving endless bands comprising means for compensating for a

A device for monitoring and compensating for changes in the flight time of the print hammers of impact printers is disclosed. The flight time of the respectively monitored hammer is calculated from the elapsed time between the moment of firing of a hammer and the moment of impact of the print type carrier against the impact platen. In order to ensure automatic self-adjustment of all print hammers in predetermined test cycles, without the actual printing process itself being affected, and without there being any test imprints on the record carrier, the print type carrier includes, in addition to the standard print types, an additional test type. The impact surface area of the test type is large enough such that no visible imprint is made upon its impact on the record carrier because of the low impact pressure.

Device for monitoring and compensating for changes in the flight time of

An adaptive equalization circuit for magnetic recording channels which derives an error signal to change the equalizer compensation value from the timing of random signal data and provides continuous feedback compensation.

Adaptive equalization circuit for magnetic recording channels utilizing

Method and apparatus for the constant speed control of a brushless DC motor, whose pole windings receive a pulsed control voltage between their commutation points, control being a function of the speed characteristics of the motor, and the commutation points being synchronized with the drop times of the motor current and the control voltage pulses. In a state in which there are no load changes, the motor current substantially rises or drops between a maximum value I.sub.max and a minimum value I.sub.min according to the pulse mode. In the event of changes in the motor load, a mean motor sum current is retained for maintaining the speed.

Method and apparatus for the constant speed control of brushless DC

To compensate for drops in the amplitude of signals read from magnetic records, in particular servo signals, a complementary correction signal is produced from the signal drops by rectifying, low-pass filtering, differentiating, integrating and forming the absolute value. This complementary correction signal is added to the defective signal to obtain a signal which has roughly been corrected to the original magnitude prior to evaluating and forming the position error signal (PES).

Magnetic disk track following servo burst amplitude drop compensation

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

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

Method and apparatus for controlling a stepping motor by storing in a memory, delay time values for the application of motor advance pulses and using motor feedback pulses to access the memory and read out corresponding time delay values after each of which a motor advance pulse is to be generated. The stored time delay values are optimized as to phase angle for the motor advance pulses for acceleration, constant run and deceleration modes of the motor after consideration of motor characteristics and load. Not all feedback pulses have a corresponding time delay value and certain feedback pulses may have two or more time delay values stored therefor. Also disclosed are improved motor coil switching circuits.

Method of controlling a stepper motor

An improved method and apparatus for determining the speed and position values of a stepping motor for controlling or regulating the same. These values are derived from induced voltages within the bifilar windings of the stepping motor combined with voltages across and currents through the same bifilar windings. The speed values are derived from the amplitude of the induced voltages and the position values are derived from the zero transitions of the induced voltages. A desirable advance of the motor is distinguished from an undesirable oscillation of the motor by determining whether the induced voltages in the bifilar windings become zero simultaneously.

Method and apparatus for determining stepping motor parameters from

A rotor stator assembly comprising a stepping motor having an improved torque-to-inertia ratio resulting from a substantial reduction in moment of inertia due to the conical shape of the rotor. A core energized by a DC coil is disposed axially of the base of the conical rotor and the magnetic path is through the base of the rotor, out its periphery, through the stator, through conductive members and back to the core. There is a further increase in torque-to-inertia ratio which is due to a decrease in rotating mass when the rotor is hollow.

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Schoenaich, Germany

Volker W Zimmermann