Maxtor Corporation

International Business Machines Corporation

James A Valent

Donovan M Janssen

Harlan P Mathews

John Paul Mantey

Donald F Colglazier

William H Ashbee

Larry E Rittenhouse

Joan Stagaman Goddard

Mark A Beran

William S Seaward

Alan J Kirton

Robert Magno

Wayne A Overby

Ronald J Martin

Richard S Kilen

Gerald P Patch

A method and apparatus for generating a position error signal (PES) voltage v. track distance curve for the head of a hard disk drive. The disk has a dedicated track which contains a plurality of servo bits that allow the head to be centered with the centerline of the track. The dedicated track also has a number of calibration bits each embedded at a known location off-set from the track centerline. The PES voltage v. track distance curve is generated by reading each calibration bit and storing the corresponding amplitude of the position error signal in a memory device of the disk drive. Each calibration bit is located from the track centerline a distance that is different from the other calibration bits so that there are provided multiple points on the track curve.

Method for generating a position error signal calibration curve in a hard disk drive

A head positioning system accurately positions a read/write head along a selected track of a rotating magnetic disk. In one aspect, servo information is embedded along the track with the centerline of the servo information offset a radial distance from the centerline of data stored or written along the track. The head positioning system micro-jogs the read/write head a first and a second radial distance from the centerline of servo information for a read operation and a write operation.

Positioning system for accurately positioning a read/write head over a

MR head differential micro-jog

A method and apparatus for creating a position error signal (PES) voltage v. track distance curve for the head of a hard disk drive. The disk has a dedicated track which contains a plurality of servo bits that allow the head to be centered with the centerline of the track. The dedicated track also has a number of calibration bits each embedded at a known location off-set from the track centerline. The PES voltage v. track distance curve is generated by reading each calibration bit and storing the corresponding amplitude of the position error signal in a memory device of the disk drive. Each calibration bit is located from the track centerline a distance that is different from the other calibration bits so that there are provided multiple points on the track curve.

Off-track PES calibration for a magneto-resistive element

The present invention involves compensating for the irregularity in the torque constant of an electric motor used to move an actuator arm carrying a magnetic read/write head in a disk drive. The torque constant of an electric motor varies across the operating range on a given drive as a function of head location. The present invention provides an apparatus and method for determining the torque constant versus position function of a given disk drive during the servo write process.

Actuator torque non-linearity compensation for hard disk drives

An improved method for compensating for the irregularity in the torque constant of the electric motor used to move the actuator arm carrying the magnetic read/write head in a disk drive is disclosed. The torque constant of the electric motor varies across the operating range on a given drive as a function of head location and the variation in torque constant is compensated for with a torque constant multiplier. The present invention provides a method for accurately determining the torque constant multiplier versus position function of a particular disk drive. In one embodiment, the method of the present invention includes the steps of: determining a nominal operating range for the location of a head over a disk for substantially all disk drives manufactured with the same manufacturing process; determining the offset of the operating range of a particular disk drive relative to the nominal operating range; modifying the location of the head, as determined by reading servo information, of the particular disk drive based on the offset; and obtaining the value of the torque constant multiplier associated with the modified head location.

Non-linearity compensation for hard disk drives

This is an electronic scheme for correcting mechanical misalignment and electrical delays from laser beam to laser beam in the scan direction of a multiple beam laser scanning system for use in an electrophotographic machine. The position at which a reference beam is turned on is sensed and adjusted to a desired position. Thereafter, the positions at which non-reference laser beams are turned on are sensed and adjusted to the desired position. In one enbodiment, the energization of laser beams is positioned at the trailing edge of the second element of a photodector. In a second embodiment, the point of full laser energy is matched, beam to beam, at the junction of the same two elements in a CCD array. Programmable delay lines are used to obtain sub-pel resolution.

Pel placement correction in the scan dimension of a multiple beam laser

An apparatus and method are disclosed for positioning magnetic heads relative to the recording tracks of a recording medium such as a floppy disk having circular, concentric recording tracks formed thereon. The magnetic heads are mounted on a head carriage, and the head carriage is moved, in response to received command pulses, so that the heads are moved linearly, by step increments, along a radius of the floppy disk. The heads are thereby moved across the spaced tracks on the disk, with each incremental movement of the heads being a distance less than the distance between the tracks, and being, for example, one-half or one-fourth of the total distance between tracks. Acoustic noise due to head movement is minimized by moving the heads by increments less than the distance between the tracks, with such movement avoiding exciting the resonances of the head moving apparatus. The magnetic heads are initially moved at a rate known to avoid exciting the resonance and, during such initial movement, the rate of received command pulses is determined. If the received command pulse rate is within a predetermined range, and is a rate that will not excite resonance, continued movement of the head is at the rate of the received command pulses.

Magnetic head positioning apparatus and method

A servo-controlled recirculating automatic document feeder (RADF) includes a plurality of independently driven document transport devices. A picker mechanism separates documents in seriatim from a stack. An entry turnaround transport device buffers and delivers picked documents to a platen transport device for exposure. After exposure, the document is transported along a simplex or duplex path for duplex or simplex copying. The document is then buffered in an exit turnaround transport device and is subsequently returned to the stack. Each transport device is independently driven by a motor and a closed-loop servo. A common reference oscillator generates source signals for the servo-loops. A microcomputer operates on the source signals and generates reference signals for driving the transport devices.

Servo-controlled automatic document feeder

A sheet registration apparatus for positioning sheets in a registered position on a work surface such as the document platen of a convenience copier/duplicator machine. The apparatus includes a bidirectional servo-controlled sheet transport for conveying the sheet over the work surface. A sheet sensing device is disposed within the path of sheet travel. A controller monitors the sensing device and activates a position control routine following the occurrence of a predetermined level change in the signal generated by the sensing device. At the end of the position control routine, the transport is stopped thereby positioning the sheet in the registration zone. The apparatus enables sheet registration for a machine operating in a duplex and/or simplex mode. The apparatus further enables registration at any point on the document platen.

Document feeder electronic registration gate

Device for separating and feeding sheets in seriatim from a stack to a processing station. The device includes a pin which periodically contacts and forms a pivot point on the stack. A rotary wave generator is disposed to rotate about the pivot point. The rotary wave generator periodically contacts a topmost sheet in the stack and shingles (that is separates) the sheet from the stack. The shingled sheet is fed into a paper sheet aligner and into the processing station. A variable or ramped force and/or a variable velocity is applied to the shingler. The force and/or velocity begins at a relatively low value and increases until a sheet is sensed downstream from the stack. This enables the feeding of a wide range of paper types and weights.

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Longmont, CO, United States of America

James A Valent