Xerox Corporation

James O Jacques

Martin O Halfhill

Leonard R Shenfield

Stipe Cizmic

Douglas K Mahon

Wayne L Edwards, Jr

Ronald W Votaw

David L Griffith

Robert Dale Carlson

A method of transferring data between a data supply and a disk having a track divided into sectors, each sector having an address recording area followed by a data recording area. The method includes detecting a defective area on a data recording area; writing an address of the defective area on the corresponding address recording area; recording data on the data recording area by detecting the defective area with the address and writing part of the data on the data recording area up to the defective area, and writing the remaining data on the data recording area succeeding the defective area; and retrieving the written data by reading the address of the defective area and then reading the recorded data. The apparatus includes a circuit to record a test pattern on the disk, a circuit to sense the recorded test pattern and provide an address of a defective area, a circuit to write the address on the address recording area, a circuit to write data on the disk, and a circuit to read the recorded area.

Method and apparatus for recording data without recording on defective

A servo system including a recording head to sense servo data on a disk track for fine positoning of the head and an external transducer for generating signals representing the coarse position of the head. A micro-processor stores the coarse positon signals which include information as to repeatable error such as wobble of the disk. A compensator maintains information concerning small offsets of the disk due to, for example, temperature variations. During coarse positioning of the head, from one track to a desired track, the stored repeatable error information and stored offset information is used to generate error signals to control movement of a carriage connected to the head, whereby the head follows the repeatable error and offset to arrive coarsely on the desired track. After coarse positioning is complete, fine positioning information from the recording head, which information includes the offset information, and the stored repeatable error information are used to generate error signals to control movement of the carriage for fine positioning purposes.

Utilization of stored run-out information in a track following servo

A higher order servo system including a phase transducer which produces two triangular waveforms, phase displaced 90.degree. in relation to each other, representing the positions of a movable member, and a commutating circuit, responsive to the triangular waveforms, for generating a sawtooth waveform and a velocity signal which is linear and continuous over the whole range of movement of the member. A counter and converter, responsive to pulses also generated by the commutating circuit, generates a staircase waveform, representing predetermined positions of the member, which is added to the sawtooth waveform to produce a positional error signal which is linear and continuous over the whole range of movement of the member. Optimal velocity and acceleration signals are derived from these two linear and continuous signals to drive the member to a desired position over the shortest path, in the minimal amount of time, and with no oscillatory motion at the desired position.

Apparatus for generating linear and continuous positional error and

A phase-sensitive transducer apparatus comprises first and second relatively movable members, the first relatively movable member having a plurality of windings and the second relatively movable member having a winding. Means are included for applying a first input signal to one of the windings of the first relatively movable member and a second input signal to another of the windings of the first relatively movable member. An output signal is developed on the winding of the second relatively movable member. The first and second input signals are sinusoidal in nature of substantially identical frequency and peak amplitude and are phase-displaced by a predetermined amount, and the output signal is substantially constant in peak amplitude and variable in phase during relative movement of the first and second relatively movable members. Further means is included which responds to the first input signal and to the output signal for generating a position signal indicative of the relative movement of the first and second relatively movable members, the position signal alternating during such relative movement between first and second voltage levels. Also, additional means is included which responds to the first input signal and to the second input signal for generating a d-c reference signal having a voltage level substantially equal to the voltage level of the position signal when the first input signal and the output signal are phase-displaced by said predetermined amount. Comparator means is included which responds to the position signal and to the d-c reference signal for offsetting the position signal by an amount represented by the voltage level of the d-c reference signal.

Phase-sensitive transducer apparatus with improved signal offset means

An exerciser is provided for use with a disk drive of the type having a microprocessor, a first memory for storing microcoded control programs for the drive, a second memory for storing instructions for the head carriage servo control apparatus, an address bus for supplying address signals from the microprocessor to the first and second memories, and a data bus for supplying program instructions from the first memory to the microprocessor, and for supplying instructions from the second memory to the servo control apparatus. The exerciser developes track address signals that are supplied onto the data bus for application to the microprocessor. A third memory is included in the exerciser for storing diagnostic programs. A decoder is also included for decoding an address signal on the address bus in order to generate a new address signal for the third memory. Program instructions accessed from the third memory are supplied onto the data bus for application to the microprocessor.

Self-diagnostic method and apparatus for disk drive

A data recording and reproducing system in which a disk having a plurality of data tracks has a track following code stored thereon, enabling a recording head moved by a servo system to be centered in relation to a desired track. The code includes, on one side of the track centerline, first regions of magnetic flux in which there is a first area of magnetic flux reversal, and, on the other side of the track centerline, second regions of magnetic flux in which there is a second area of opposite flux reversal adjacent the first area. The lines of flux in each area are equal. A recording head, when centered on the track centerline, detects no difference in the number lines of flux between the first and second areas due to its self-nulling properties, though the output signal of the head, which represents the rate of change of detected flux as the head traverses the two areas, may show differences at different points in time of detection. An integrator integrates the head output signal, which integrated signal thus represents such difference in the number of lines of flux and is an error signal used in the servo system to move the head on center, if needed. If the head is off center, a difference in number of lines of flux will be detected, thereby producing the error signal to move the head on center.

Track following servo system and track following code

A disk drive comprises a housing having a door through which a cartridge including a recording disk therein may be inserted. A spindle drive assembly is mounted in the housing and is responsive to a first set of instructions for rotating the recording disk of a disk cartridge loaded into the housing through the door and onto the spindle drive assembly. An actuator is also mounted in the housing and is capable of controlled reciprocal movements relative to the axis of rotation of the spindle drive assembly. A head carriage assembly is mounted in the housing to the actuator and includes at least one electromagnetic read/write head thereon for reading data from the writing data onto tracks of the recording disk of a cartridge loaded onto the spindle drive assembly. Servo control apparatus is mounted in the housing and is responsive to a second set of instructions for controlling the speed and direction of the reciprocal movements of the actuator. Additionally, read/write apparatus is mounted in the housing and is responsive to a third set of instructions for controlling the reading and writing of data by the electromagnetic head. Further, programmed data processing means is mounted in the housing and is connected to the spindle drive assembly, the servo control system and the read/write apparatus for generating the first, second and third sets of instructions under program control.

Control system for disk drive

A method and apparatus for restoring the electromagnetic read/write head of a disk drive from a position between a data-field track located closest to the axis of rotation of a disk loaded in the drive and a data-field track located furthest to such axis of rotation, to a position over the latter data-field track. A first predetermined code is prerecorded on each data-field track and a second predetermined code is prerecorded on each of a plurality of guard-band tracks. The head is first moved in a direction away from the axis of rotation of the disk at a predetermined velocity. The code stored on each track is read and detected as the head is moved thereover. The head is stopped over a track when the code read and detected therefrom is the second predetermined code. Then, the head is moved in a direction toward the axis of rotation of the disk and stopped over the data-field track located furthest from the axis of rotation of the disk.

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Tracy, CA, United States of America

James O Jacques