Thomas Robert Albrecht

Bio: Thomas Robert Albrecht is an academic researcher from IBM. The author has contributed to research in topics: Servo & Servomechanism. The author has an hindex of 3, co-authored 7 publications receiving 347 citations.

Timing based servo system for magnetic tape systems

Abstract: A track following servo system is disclosed for use with magnetic tape systems in which magnetic servo track patterns contain transitions recorded at more than on azimuthal orientation across the width of the servo track. The timing of a signal derived from reading at any point across the width of such a pattern varies continuously as the read head is moved across the servo track. The pattern is read by a servo read head whose width is small compared to the servo track pattern. The combination of a wide servo pattern and a narrow servo read head offers excellent position sensing linearity and dynamic range. In the preferred embodiment, the servo read head is also narrow with respect to the data tracks, which provides the additional advantages of superior immunity to position sensing errors caused by defects or temporal variations in the servo read head, defects in the servo pattern on the tape, wear of the head or tape, or debris collection on the head or tape. Position sensing with this system is achieved by deriving a ratio of two servo pattern intervals and therefore is insensitive to tape speed during reading. The servo patterns may include spacing intervals recognizable for error detection and correction purposes. Servo tracks are recorded using a patterned multiple gap servo write head whose magnetic gaps have geometries appropriate to generate the desired servo patterns. The patterned gaps of the servo write head are produced by photolithographically defined electroplating of permalloy on a ferrite ring head structure.

Servo control system

Abstract: A track following servo system is disclosed for use with magnetic recording media 20 in which magnetic servo track 27 patterns contain transitions recorded at more than one azimuthal orientation across the width of the servo track. The timing of a signal derived from reading at any point across the width of such a pattern varies continuously as the read head is moved across the servo track. The pattern is read by a servo read head 26 whose width is small compared to the servo track pattern. The combination of a wide servo pattern and a narrow servo read head offers excellent position sensing linearity and dynamic range. In the preferred embodiment, the servo read head is also narrow with respect to the data tracks, which provides the additional advantages of superior immunity to position sensing errors caused by defects or temporal variations in the servo read head, defects in the servo pattern, wear of the head, or debris collection. Position sensing with this system is achieved by deriving a ratio of two servo pattern intervals and therefore is insensitive to medium speed during reading. The servo patterns may include spacing intervals 70 recognizable for error detection and correction purposes. The servo tracks may be recorded using a patterned multiple gap servo write head 400 whose magnetic gaps have geometries appropriate to generate the desired servo patterns.

Servo control system and equipment, and its generating method and storage system

Abstract: A track following servo system is disclosed for use with magnetic recording media 20 in which magnetic servo track 27 patterns contain transitions recorded at more than one azimuthal orientation across the width of the servo track. The timing of a signal derived from reading at any point across the width of such a pattern varies continuously as the read head is moved across the servo track. The pattern is read by a servo read head 26 whose width is small compared to the servo track pattern. The combination of a wide servo pattern and a narrow servo read head offers excellent position sensing linearity and dynamic range. In the preferred embodiment, the servo read head is also narrow with respect to the data tracks, which provides the additional advantages of superior immunity to position sensing errors caused by defects or temporal variations in the servo read head, defects in the servo pattern, wear of the head, or debris collection. Position sensing with this system is achieved by deriving a ratio of two servo pattern intervals and therefore is insensitive to medium speed during reading. The servo patterns may include spacing intervals 70 recognizable for error detection and correction purposes. The servo tracks may be recorded using a patterned multiple gap servo write head 400 whose magnetic gaps have geometries appropriate to generate the desired servo patterns.

Servo control system, data memory system

Abstract: A track following servo system is disclosed for use with magnetic recording media 20 in which magnetic servo track 27 patterns contain transitions recorded at more than one azimuthal orientation across the width of the servo track. The timing of a signal derived from reading at any point across the width of such a pattern varies continuously as the read head is moved across the servo track. The pattern is read by a servo read head 26 whose width is small compared to the servo track pattern. The combination of a wide servo pattern and a narrow servo read head offers excellent position sensing linearity and dynamic range. In the preferred embodiment, the servo read head is also narrow with respect to the data tracks, which provides the additional advantages of superior immunity to position sensing errors caused by defects or temporal variations in the servo read head, defects in the servo pattern, wear of the head, or debris collection. Position sensing with this system is achieved by deriving a ratio of two servo pattern intervals and therefore is insensitive to medium speed during reading. The servo patterns may include spacing intervals 70 recognizable for error detection and correction purposes. The servo tracks may be recorded using a patterned multiple gap servo write head 400 whose magnetic gaps have geometries appropriate to generate the desired servo patterns.

Servo control system, servo write head, servo pattern write apparatus, magnetic memory medium, and method for generating servo pattern on magnetic memory medium

Abstract: PROBLEM TO BE SOLVED: To more easily detect a position signal error by setting a width of a servo read head to be smaller than half a width of a narrowest data read head when the width is defined as a size of the head in a direction perpendicular to a conversion direction SOLUTION: A relative move of a servo read head 26 in a conversion direction of a tape head whereby the servo read head can read a servo pattern is generated when a tape 20 moves straight with respect to the servo read head 26 in a longitudinal direction of a center line 30 of a servo track The servo pattern of a magnetic flux transition is detected, and a servo read head signal of an analog form is generated and supplied to a signal decoder 36 The signal decoder 36 processes the signal and supplies via a position signal line 38 to a servo controller 40 The servo controller 40 monitors a position signal from the signal decoder 36 and generates a control signal necessary for the head to reach a desired position

Disk drive demodulating a time-based servo pattern

Abstract: A disk drive is disclosed including a disk having a first and second set of time-based servo patterns. The first set of time-based servo patterns comprises a first cyclical pattern that repeats radially over the disk, and the second set of time-based servo patterns comprises a second cyclical pattern that repeats radially over the disk, wherein each cyclical pattern comprises a plurality of timing marks. One of the first cyclical patterns overlaps at least part of a first servo track, and one of the second cyclical patterns overlaps at least part of the first servo track. At least one of the first and second set of time-based servo patterns are demodulated by detecting first and second time intervals relative to the timing marks, and a control signal for actuating the head is generated in response to the first and second time intervals.

Disk drive comprising slanted line servo bursts having reverse polarity segments

Abstract: A disk drive is disclosed comprising a disk having servo data defining a plurality of servo tracks. The servo data comprises a preamble, and a plurality of slanted line servo bursts recorded at a tilt angle with respect to the preamble. At least one of the slanted line servo bursts comprises a first polarity along a first segment of the slanted line and a second polarity along a second segment of the slanted line. A position error signal (PES) is generated in response to a phase difference when reading the preamble and the slanted line servo bursts.

Disk drive comprising slanted line servo burst sets offset radially

Abstract: A disk drive is disclosed comprising a disk having servo data defining a plurality of servo tracks. The servo data comprises a preamble, and a plurality of slanted line servo bursts recorded at a tilt angle with respect to the preamble. The slanted line servo bursts comprises a first plurality of slanted line servo bursts and a second plurality of slanted line servo bursts, wherein the second plurality of slanted line servo bursts are offset radially from the first plurality of slanted line servo bursts. A position error signal (PES) is generated in response to a phase difference when reading the preamble and the slanted line servo bursts.

Disk drive comprising slanted line servo bursts having a varying tilt angle

Abstract: A disk drive is disclosed comprising a disk having servo data defining a plurality of servo tracks. The servo data comprises a preamble comprising a varying length across a radius of the disk, and a plurality of slanted line servo bursts recorded at a tilt angle with respect to the preamble. The tilt angle varies across the radius of the disk commensurate with the varying length of the preamble. A position error signal (PES) is generated in response to a phase difference when reading the preamble and the slanted line servo bursts.

System and method for writing servo sectors in a perpendicular media recording environment

Abstract: A perpendicular media recording (PMR) servo track writer (STW) system and method for writing servo sectors onto a disk is disclosed. The servo writer includes a head positioner to position a head of a head disk assembly (HDA) relative to a disk, wherein the head writes servo sectors onto the disk with a perpendicular flux. The servo writer includes a controller to control the head positioner such that the head writes servo sectors onto the disk from one of an inner diameter (ID) or an outer diameter (OD) of the disk to a middle diameter (MD) of the disk, respectively, followed by writing servo sectors between the other of the OD or the ID of the disk to the MD of the disk, respectively.