Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1999-02-22
2002-07-02
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06414815
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a hard disk drive, and more particularly, to an apparatus for controlling on-track operation in which an actuator is brought on a predetermined position of a track, and to a method thereof.
2. Description of the Related Art
A hard disk drive is an auxiliary computer memory which stores and retrieves information on a disk using a magnetic head. Two types of motors are used to drive the hard disk drive: a spindle motor for rotating a magnetic disk and a voice coil motor for locating the magnetic head on a target track. The voice coil motor is a linear motor, and is driven by a magnetic force by applying current to a coil in a magnetic field formed by a magnet.
Meanwhile, if the power supply of the disk drive is turned off, the spindle motor stops rotating and the head loses its buoyance, so that the head is parked automatically in a parking zone of the disk. At this time, if external vibration or impact is applied to the hard disk drive, the head contacts a data zone of the disk and can cause hard defects, thereby damaging the disk and losing data. The disk having the hard defects cannot be read or written. Thus, a latch is required to hold an arm on which the head is mounted, with a constant force, to avoid the above problems.
Unlatching is opposite to latching, i.e., a routine in which power is applied to the hard disk drive, various integrated circuits (ICs) are initialized in software, and further the actuator moves from the parking zone to a data zone. The unlatch operation is performed by applying an unlatch current to the voice coil motor, and involves initially seeking or on-track, bringing the actuator on a predetermined track. If the unlatch current applied to the voice coil motor in order to move the actuator is excessively high, then the disk, when the actuator is unlatched, in an inner or outer disk can be impacted, which can thereby damage the head and the disk.
Also, even if the actuator is positioned in the data zone, since disturbance of various devices or circuits is not known, it is difficult to bring the actuator on-track in an initial state. That is, after applying the unlatch current, the actuator has a high speed due to disturbances such as air resistance, bearing friction or offset of the circuit during the initial seek or on-track, so that it is very difficult to perform the initial on-track. The disturbances caused by the apparatus are regular, and typically can be corrected by calculating a mean of the offset. However, since various integrated circuit (IC) and passive elements are random, it is almost impossible to estimate the offset of the circuit.
Accordingly, in order to reduce the influence due to the external disturbances during the initial on-track or seek, there have been developed a bearing having low friction, and a suspension for reducing the air resistance. Further, in order to reduce the offset of the circuit, devices having high accuracy are used. However, all these increase the cost. Also, when the disturbance cannot be reduced, it is difficult to develop a device having high Tracks Per Inch.
U.S. Pat. No. 3,994,016 to Moghadam entitled
Head Positioning Servo System for Disk Drives
, discloses a closed loop head positioning servo system for use in a disk drive employing a disk pack having a dedicated servo surface and a number of data surfaces carrying both data and servo information. It is disclosed that a track counting coarse positioning system is used to move the heads in a ganged assembly to the vicinity of a desired cylinder. A fine positioning system includes one error circuit for generating an error signal representing the deviation of a servo head from a desired cylinder on the dedicated servo surface. Another error circuit generates a second error signal representing the offset of a selected data head from a selected data track in the same cylinder. Analog circuits combine the error signals to produce an output signal which, when applied to an actuator, centers the selected data head on the selected track.
U.S. Pat. No. 4,419,701 to Harrison, et al. entitled
Data Transducer Position Control System for Rotating Disk Data Storage Equipment
, disclose a system for controlling the position of a head carriage structure of a rotating disk data storage system that includes circuitry for generating a polyphase track boundary signal which compensates for drift, and which doubles or further increases the track density to increase storage capacity. A track centerline sensor circuit is simplified by including the function thereof as microcode routines within a dedicated digital control processor. Error signals are measured periodically across the entire useful field of the disk, and they are constantly updated, so that compensation for drift, runout and offset of the disk relative to the data transducer is achieved. Track overshoot during track seeking movements of the transducer is accommodated, enabling reduced track average access time.
U.S. Pat. No. 4,524,397 to Chalmers, et al. entitled
Head Positioning System for a Disc Data Store
, disclose a disc data store, wherein a read/write head is radially positionable by a feedback servomechanism to interact with a selectable one out of a plurality of radially equispaced data storage tracks on a rotary disc. Positioning errors resultant from phase errors between the plural signals available as the output of an optical grating head position transducer are eliminated by replacing one of the data storage tracks with a servo track by arranging that the period of the recursive, triangular wave position indicating signals from the transducer is equal to twice the radial spacing between tracks on the disc, by selecting as the exclusive-used position indicating signal that one of the plurality of transducer signals which brings the head to the center of the servo track with least offset, and while employing that selected signal or its generated inverse as the feedback signal to the servomechanism applying that least offset as a correction when positioning the head over data storage tracks.
U.S. Pat. No. 4,797,756 to Yoshihara, et al. entitled
Method for Positioning Head in Disk Drive Deriving “Position” Offset from “Quadrature
” Signals, disclose for a disk drive servo system using position and position-quadrature signals, a method for automatically effecting “Absolute Track Registration” and compensating for “offsets” by using the peak position of one of the signals to find a “true” position (true offset) for the other, wherein the R/W actuator is brought to rest at a reference position and a sample-offset signal generated, while the corresponding magnitude of related positioning signals are detected. This is repeated until the peak values of the positioning signals are located, whereupon the corresponding position-offset is derived as “true offset”, the actuator then being repositioned by the “true offset” value; and repeating this for a given number of track sites across the disk.
U.S. Pat. No. 4,812,726 to Benii, et al. entitled
Servo Circuit Positioning Actuator
, disclose a servo system for controlling the position of an object in accordance with a servo signal, employing an A/D converter to normalize an error in the position of the object and to enable digital correction of an offset in the system and digital compensation for track jumping and drop outs.
U.S. Pat. No. 4,954,907 to Takita entitled
Head Positioning Control Method and System
, discloses a data recording disk file, wherein head positioning servo information is located in sectors angularly spaced around the disk, and utilizes a head positioning control system for data track following. The control system includes timing circuitry and head position detection circuitry for generating, respectively, a servo sector initiation signal and a signal representative of the head position relative to the centerline of the desired data track to be followed. The control system also includes a velocity detector for determining the velocity of the head re
Bushnell, Esq Robert E.
Hudspeth David
Wong K.
LandOfFree
Apparatus and method for controlling on-track operation of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and method for controlling on-track operation of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and method for controlling on-track operation of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2877290