Abstract: A system is disclosed wherein a plurality of discs in a stack are accessed using a vertical head array including two servo heads, one located at or near each end of the disc stack. In order to exactly center any given data head over a desired data track location in the disc stack, the error distance of the given data head relative to the data track can be determined by combining proportions of the two servo head signals from the top and bottom servo heads, their proportions being based on the vertical distance of each of the servo heads from the given data head which is to be exactly centered over a data track. If the servo distance from the disc edge is represented by S.sub.1 and S.sub.2, and the vertical distances from the head to the center of the servo heads is represented by Y.sub.1, Y.sub.

Abstract: A servo disc in a magnetic disc drive has pulses recorded in frames in concentric data tracks. Each frame includes first and second sync pulse groups of at least one sync pulse each, a first track alignment signal (Quad) following the first sync group, and a second track alignment signal (Sig) following the second sync group. A Guard Band and a data Track Zero are identified by eliminating one sync pulse in selected members of frames. Circuitry including monostable multivibrator, flip-flops, and gates identify the Guard Band and Track Zero.

Abstract: In a device for retrieving and recording (read/write) information on at least one rigid disk, a stepping motor servo system operated in an open-loop manner is provided to rapidly and accurately position read/write heads relative to the disk. A fixed guide shaft adjacent to and transverse to the motor shaft carries a carriage slidably thereon, preferably on oil impregnated bearings, the carriage member including a gear rack and the stepping motor having a pinion gear thereon interfacing with the gear rack. A preload bearing is urged against the carriage at a position between the guide shaft and the pinion gear such that the carriage is rotated around the guide shaft into engagement with the pinion gear at the rack portion thereof.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Flexible disc memory apparatus has a drive for rotating the flexible disc in a cartridge which is opened when inserted into the apparatus by a wedge shaped member inserted into the cartridge. The drive includes a magnetic coupling and centering device for the hub of the flexible disc. A movable head plate carries transducer heads which are positioned at selected track locations by the head. The apparatus also includes a second flexible disc and head plate integrally incorporated in the apparatus.

Abstract: A sector formatting and record addressing scheme and associated electronic recording and detection control systems for a removable cartridge disc used in a magnetic information storage unit. Indelible sector mark and record address/format information are electronically pre-recorded on the disc at the factory using a high precision cartridge writer. This cartridge writer phase-locks the recording clock to a magnetically recorded clocking disc rotating on the same shaft as the disc via an associated position transducer to write an exact number of bytes on each track having a precise physical relationship to each other. Separate recording clocks having a wide bit-frequency spectral separation are used to write sector mark and address/format data to provide maximum sector detection reliability. The cartridge writer control system computes the optimum length of sector code for the customer-specified record size.