Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
1999-01-15
2001-01-16
Letscher, George J. (Department: 2754)
Dynamic magnetic information storage or retrieval
Record medium
Disk
C360S077080
Reexamination Certificate
active
06175472
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for generating a position error signal calibration curve for a read element of a hard disk drive.
2. Description of Related Art
Hard disk drives contain a disk that rotates relative to a head. The head is located at the end of an actuator arm assembly. The actuator arm assembly includes a voice coil motor which can move the head relative to the surface of the disk. The head contains a transducer which can magnetize and sense the magnetic field of the disk.
Data is stored on the disk within a number of concentric radial tracks. Each track is further divided into a plurality of sectors. To accurately write and read data, it is desirable to maintain the head on the center of the track. To assist in controlling the position of the head, each sector of the disk typically contains a number of servo bits accurately located relative to the centerline of the track. The raw signals produced by the servo bits are typically demodulated into a single position error signal (PES). The electronic circuits of the drive utilize the position error signals to determine the position of the head relative to the track, and to move the actuator arm if the head is not located on the track centerline.
The servo routine of a hard disk drive is typically performed with a position error signal voltage v. track distance curve that is stored within memory of the drive. The voltage v. track distance curve provides a correlation between the amplitude of the position error signal and the distance between the head and the center of the track. For example, a PES signal having an amplitude of approximately ½ of the peak amplitude may provide an indication that the head is a ¼ track width away from the track centerline. In accordance with the track curve, the actuator arm is moved a corresponding distance to center the head. The voltage v. track distance curve is typically based on an ideal curve that is generated from an algorithm stored in the read only memory (ROM) of the drive.
Conventional hard disk drive read/write heads typically have a single transducer that both read and write data onto the disk. Generally speaking, conventional single element heads have reached maximum aerial densities (typically measured in gigabits per square inch). There does exist a dual element head that has been found to provide greater aerial densities than single element transducers. Dual element heads contain a single write element and a separate read element that is constructed from a magneto-resistive material. Such dual element transducers are commonly referred to as magneto-resistive (MR) heads.
Because of manufacturing tolerances, the separate magneto-resistive element may be off-center from the write element of the head. Therefore, if data is written off the center of the track, to read the data, the servo system must move the head slightly off-center so that the read element is centered with the written data. The routine of moving an MR head during a read operation is commonly referred to as micro-jogging.
The head can be moved in accordance with the voltage v. track distance curve stored in memory. It has been found that the voltage v. track distance curve for a MR head is nonlinear in nature and varies greatly between different heads. It would therefore be desirable to provide a method for Generating an actual voltage v. track distance for a magneto-resistive head.
SUMMARY OF THE INVENTION
The present invention is 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.
REFERENCES:
patent: 5121260 (1992-06-01), Asakawa et al.
patent: 5400201 (1995-03-01), Pederson
patent: 5436773 (1995-07-01), Hanson
patent: 5455724 (1995-10-01), Suzuki et al.
patent: 5760990 (1998-06-01), Uktani et al.
patent: 5940240 (1998-06-01), Kupferman
patent: 267669 (1988-05-01), None
patent: 361222 (1990-04-01), None
patent: WO 88/03693 (1988-05-01), None
patent: WO 93/10525 (1993-05-01), None
G.S. Mowry, P.K. George, K.M. Loeffler and N.R. Belk, “Thin-Film Magnetorresistive Heads for Narrow-Track Winchester Applications (Invited)”, IEEE Transactions on Magnetics, vol. MAG-22, No. 5, Sep. 1986, pp. 671-676.
Magnetic Recording, vol. I, Mee, Daniel, McGraw-Hill Press, '87, Section 4.4.3, pp. 289-295.
H. Suyama, K. Tsunewaki, M. Fukuyama, N. Saito, T. Yamada and H. Karamon, “Thin Film MR Head for High Density Rigid Disk Drive”, IEEE Transactions on Magnetics, vol. 24, No. 6, Nov. 1988, pp. 2612-2614.
P.I. Bonyhard, “Design Issues for Practical Rigid Disk Magnetoresistive Heads”, IEEE Transactions on Magnetics, vol. 26, No. 6, Nov. 1990, pp. 3001-3003.
Ching Tsang, Mao-Min Chen, Tadashi Yogi, Kochan Ju, “Gigabit Density Recording Using Dual-Element MR/Inductive Heads On Thin-Film Disks”, IEEE Transactions on Magnetics, vol. 26, No. 5, Sep. 1990, pp. 1689-1693.
F.B. Shelledy and J.L. Nix, “Magnetoresistive Heads for Magnetic Tape and Disk Recording”, IEEE Transactions on Magnetics, vol. 28, No. 5, Sep. 1992, pp. 2283-2288.
Letscher George J.
Maxtor Corporation
Sigmond David M.
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