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    MAGNETIC HEAD POSITIONING APPARATUS AND METHOD
    3.
    发明专利
    MAGNETIC HEAD POSITIONING APPARATUS AND METHOD 未知

    公开(公告)号：CA1236568A

    公开(公告)日：1988-05-10

    申请号：CA529772

    申请日：1987-02-16

    Applicant: IBM

    Inventor： ASHBEE WILLIAM HENRY ,  KILEN RICHARD SCOTT ,  KIRTON ALAN JOHN ,  RITTENHOUSE LARRY EDWARD ,  VALENT JAMES ALFRED

    IPC: G11B21/08 ,  G11B5/55 ,  G11B21/10

    Abstract: MAGNETIC HEAD POSITIONING APPARATUS AND METHOD 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, onehalf 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.

    5.
    发明专利
    未知

    公开(公告)号：DE3682706D1

    公开(公告)日：1992-01-16

    申请号：DE3682706

    申请日：1986-03-21

    Applicant: IBM

    Inventor： KILEN RICHARD SCOTT ,  RITTENHOUSE LARRY EDWARD

    IPC: H02P29/00 ,  H02P23/00 ,  H03L7/06 ,  H03L7/085 ,  G05D13/62

    Abstract: @ The speed of a DC motor is controlled by a servo which includes a digital phase lock loop. The motor drives a tachometer whose pulse (22) frequency is low relative to the frequency of a clock - (21). The clock continuously drives a counter (200) whose ever increasing number content is gated to a data latch (26) upon the occurrence of each successive tachometer pulse, thus this data latch contains a first time-number of ever increasing magnitude. A second data latch (24) contains a second number. The difference in magnitude of two consecutive time-numbers is indicative of motor speed. Initially, this second number is set to contain a reference number (REF) which is equal in magnitude to the number of clock pulses which will occur between adjacent tachometer pulses when the motor is running at desired speed. A pair of limit numbers - (RANGEL and RANGEH) are provided to define the upper and lower limits of servo saturation. The difference between the first number and the second number is detected upon the occurrence of each tachometer pulse to generate a third or difference number (ERRA). This difference number is compared to the two limit numbers to determine if the servo is in saturation. If it is not in saturation, the second number is reset to a value which is equal to the old value plus the reference number. If the servo is in saturation, the second number is reset to a number which is a function of the first number, the reference number, and that limit number which is associated with the particular mode of saturation.

    DATA PROCESSING SYSTEM
    6.
    发明专利
    DATA PROCESSING SYSTEM 未知

    公开(公告)号：GB1292568A

    公开(公告)日：1972-10-11

    申请号：GB1362371

    申请日：1971-05-07

    Applicant: IBM

    Inventor： EVANGELISTI CARLO JOHN ,  RITTENHOUSE LARRY EDWARD

    IPC: G06F17/30 ,  G11B20/12 ,  G11B27/10 ,  G11B27/11 ,  G11B27/32

    Abstract: 1292568 Storage addressing system INTERNATIONAL BUSINESS MACHINES CORP 7 May 1971 [12 June 1970] 13623/71 Heading G4C A storage file, e.g. disc, drum, tape, delay line, is divided into blocks, each of which contains a plurality of data files and a directory containing the names of the data files in the block and their intra-block addresses, the data file names are used for pointing to the block in which the files are contained, a pointed-to block is accessed first at its directory to obtain the intra-block address of a desired data file by comparison of file names, and then at the remainder of the block to obtain the desired file by comparison of intra-block addresses. In the described embodiment, the file names are processed by a hashcoding algorithm to obtain the block pointers and while a disc transducing head is being moved to access the block containing the desired file, the file name is entered in a register 12. When the appropriate block is being accessed, its directory is searched in real time by reading the directory serially by bit into a shift register 10 and comparing the contents of one section of the register 10 with those of register 12 in a comparator 22. On detecting a match, the intra-block start address of the desired file and of the following file (or the file end address if the desired file is the last in the block) are transferred to registers 14, 16 for subsequent comparison with an incremented intra-block address register 18 which is started when the end of the directory is reached. The begin and stop read signals from comparators 28, 32 are used to transfer the desired file from shift register 10 to an output device. By adding duplicate circuits, more than one file may be accessed from a block in a single seek and read operation, and the files may be of variable length.

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