Abstract: A digital servo control system for disk drives is an “embedded” system—one in which servo control information is embedded on the same disk surface as the user data. In contrast to known embedded-servo systems in which a space-consuming series of many dibit pairs is present, the present system provides only a single dibit pair in a fractional positional error (PESF) area. Thus, the disk drive's read head encounters only a single dibit pair per sample period (or per data sector), thus saving valuable disk space that may be used for user data. Various pre-processing methods may be provided so as to pre-process the measurement derived from the single dibit pair per sample period (or data sector), so as to compensate for non-ideal characteristics of the dibit measurement. The system thus provides an accurate and robust servo control system, while sacrificing a minimum amount of valuable disk space to the servo information field.

Abstract: A high capacity computer disk drive system operating a micro-hard disk drive is disclosed in which the hard disk rotates at a speed of approximately 2746 r.p.m. and in which the data received from the host computer for storage on the hard disk is converted to 2,7 RLL coding prior to being written onto the disk. The disk drive system disclosed herein has a formatted data storage capacity in excess of 10 MB and an unformatted digital information storage capacity in excess of 12.5 MB, using both sides of the disk. The micro-hard disk drive system is connected to a host computer using a Small Computer Systems Interface (SCSI) which eliminates the need to provide additional disk controller hardware and software in the host computer. The micro-Winchester disk drive system is particularly suited to meet the needs of a portable computer system.

Abstract: In a digital servo control system especially suitable for use in disk drives, a sample integrity tester is provided. Sample measurements, indicating the position of a disk drive's read/write head relative to tracks of information on a recording medium, are subject to error due to noise. The sample integrity tester 2410, 2420, 2430 effectively filters out noise-corrupted measurements and thus prevents clearly erroneous measurements from contaminating calculations performed within the servo controller's control loop. If a measured position signal falls outside a given window (indicating a possible spurious position value has been read), an observer's predicted value is used rather than the spurious value. Using the predicted value allows the loop to operate in a "freewheel" (open-loop) mode. A preferred implementation of the sample integrity tester involves a coarse window that is static, and a fine window that changes dynamically based on an effort signal.

Abstract: In a servo controller for controlling the position of a read/write head of a disk drive, a calibrated controller is dedicated to fixed-distance seeks, especially for "single-track seeks" (seeks to an immediately-adjacent track). The controller is first calibrated during a calibration period that precedes an operational period. The purpose of the calibration period is to determine an optimum combination of "calibrated values" for the fixed-distance seeks. "Calibrated values" may include: acceleration pulse magnitude, acceleration pulse duration, deceleration pulse magnitude, and deceleration pulse duration. During the calibration period, various combinations of possible calibrated values are tested during a series of test seeks of the predetermined fixed distance.

Abstract: A servo control system provides adaptive compensation for a variety of tracking and seek problems found in disk drives. The servo control system is ideally implemented in digital form for accuracy, speed and compactness. A first embodiment includes two modes, a tracking (or position) mode and a seek (or velocity) mode, each mode employing a variety of compensation functions. A second embodiment includes a single comprehensive control system which functions during both tracking and seek operations.

Abstract: A servo control system provides adaptive compensation for a variety of tracking and seek problems found in disk drives. The servo control system is ideally implemented in digital form for accuracy, speed and compactness. A first embodiment includes two modes, a tracking (or position) mode and a seek (or velocity) mode, each mode employing a variety of compensation functions. A second embodiment includes a single comprehensive control system which functions during both tracking and seek operations.

Abstract: A servo control system provides adaptive compensation for a variety of tracking and seek problems found in disk drives. The servo control system is ideally implemented in digital form for accuracy, speed and compactness. A first embodiment includes two modes, a tracking (or position) mode and a seek (or velocity) mode, each mode employing a variety of compensation functions. A second embodiment includes a single comprehensive control system which functions during both tracking and seek operations.

Abstract: A servo control system provides adaptive compensation for a variety of tracking and seek problems found in disk drives. The servo control system is ideally implemented in digital form for accuracy, speed and compactness. A first embodiment includes two modes, a tracking (or position) mode and a seek (or velocity) mode, each mode employing a variety of compensation functions. A second embodiment includes a single comprehensive control system which functions during both tracking and seek operations.

Abstract: A servo control system provides adaptive compensation for a variety of tracking and seek problems found in disk drive. The servo control system is ideally implemented in digital form for accuracy, speed and compactness. A first embodiment includes two modes, a tracking (or position) mode and a seek (or velocity) mode, each mode employing a variety of compensation functions. A second embodiment includes a single comprehensive control system which functions during both tracking and seek operations.

Abstract: A servo control system provides adaptive compensation for a variety of tracking and seek problems found in disk drives. The servo control system is ideally implemented in digital form for accuracy, speed and compactness. A first embodiment includes two modes, a tracking (or position) mode and a seek (or velocity) mode, each mode employing a variety of compensation functions. A second embodiment includes a single comprehensive control system which functions during both tracking and seek operations.

Abstract: A magnetic disk drive design provides reduction of vibration and acoustic noise, and damping of mechanical resonances to mechanical components such as a base assembly. Based on applications of the principles of constrained layer damping, a layer of adhesive material is inserted between the base assembly and a circuit board assembly. In this manner, numerous advantages are provided, including reducing the acoustic noise produced by the drive, providing damping to structural resonances in the drive, and reliable attachment of the circuit board to the base assembly.

Abstract: A spindle assembly with air bearings for use in a hard disk storage device. The spindle assembly consists of a stationary shaft assembly and a rotating hub assembly that is supported in rotation by self-acting air bearings formed between adjacent axial and radial surfaces of the shaft assembly and the hub assembly. The shaft assembly includes a stationary shaft. A cylindrically hollow ceramic sleeve is fitted around the shaft. A double herringbone groove pattern is indented into the outer cylindrical surface of the sleeve. A further hollow ceramic cylinder fits over the sleeve such that a suitable air bearing can develop between the outer surface of the sleeve and an inner surface defined in the cylinder. Two disk-shaped ceramic thrust plates are fitted around the shaft, one on either side of the hollow sleeve.

Abstract: The invention provides a magneticf actuator lock for the head positioning actuator of a disk drive. The magnetic actuator lock comprises a magnet, and first and second stop means, one of which is attached to the head positioning actuator. The stop means constitute a low reluctance pathway for magnetic flux, thus attracting and "latching" the two stop means together. This magnetic actuator lock does not require an additional permanent magnet but may use the magnetic force of the permanent magnet in a voice coil motor.

Abstract: A very high capacity, closed-loop Winchester disk drive system particularly suited to meet the demands of a portable computer system is disclosed. The micro-Winchester disk is a Winchester disk of 95 mm in diameter. The disk drive system of the present invention, by virtue of its small size and vibration isolation, is ideally suited for use in portable computer systems. The micro-Winchester disk drive system was developed to store data at a density in excess of 1000 tracks per inch utilizing a closed-loop rotary voice coil positioning mechanism. This disk drive system provides fast access data storage for use with small business computers, terminals and microprocessor-based systems, portable or otherwise, and many other areas where compact, rugged, and lightweight hard disk storage is required. The disk drive system of the present invention normally utilizes between two and four hard disks, such as Winchester disks, with one disk containing a dedicated servo surface.

Abstract: A fine position closed loop servo system is disclosed for magnetic disk storage media having a plurality of data storage disks in which a first servo burst is contained on the surface of one of the data storage disks, the servo burst data being spaced at radial positions one-half track displaced from each of the odd-numbered concentric track centerlines and a second servo burst signal is contained on the surface of another of the data storage disks, the second servo burst signal being recorded at radial positions one-half track displaced from the even-numbered concentric track centerlines. Both the first and second servo burst data are read simultaneously utilizing the data transducers associated with the surfaces of the respective data storage disks and the envelopes of each of the servo burst signals are simultaneously, separately detected.

Abstract: A method of and apparatus for generating and protecting hard sector pulses using the read/write heads of the disk drive without using any external transducers is disclosed. Each track of the disk is pre-formatted with a pattern of a burst of data followed by a short erased gap repeated around the track once per sector. The data bursts are converted to digital pulses which are used to trigger a monostable as long as the read/write heads are positioned over data. The lack of an output signal from the monostable is used to detect the erased gaps. At the end of the erased gap, a sector marker pulse is generated. Various protection signals are also generated. The high capacity hard sectored computer disk drive system disclosed herein utilizes a hard disk which rotates at a speed of approximately 2750 r.p.m. The data received from the host computer for storage on the hard disk is converted to 2,7 RLL coding prior to being written onto the disk.

Abstract: An active termination circuit for a computer interface for reducing line reflection of logic signals. A first and second resistor combination is permanently connected to a cable that couples a plurality of peripheral devices to one another. The other ends of the first and second resistors are connected through a switching device to a positive voltage supply line and to logic ground, respectively. That switching device may be a transistor. When termination of multiple devices is required, a plurality of resistor combinations is provided but on/off control of the switch is achieved by one control that is located remote from the termination circuit.

Abstract: An improved servo positioning system for a Winchester disk drive system is disclosed. A plurality of concentric servo tracks are provided on the surface of one disk. Each track is comprised of an equal number of frames of a preterminded length. Four basic frame patterns are utilized. In addition, a frame may also have a code bit in a predetermined position, in order to define the frame as a "one" or "zero" frame. The servo data is read by a dedicated servo head, digitized and fed to a logic array which receives as its only other input an 8 megahertz clock signal. The logic array detects the sync signals present in each frame and generates index, guardband and no sync signals therefrom. In addition, a plurality of windows, each corresponding to a predetermined portion of each frame, is generated. Those window signals are utilized to control a window control circuit which sequentially enables four similar peak dectors, one for each window.

Abstract: A fine position closed loop servo system is disclosed for magnetic disk storage media having a plurality of data storage disks in which a first servo burst is contained on the surface of one of the data storage disks, the servo burst data being spaced at radial positions one-half track displaced from each of the odd-numbered concentric track centerlines and a second servo burst signal is contained on the surface of another of the data storage disks, the second servo burst signal being recorded at radial positions one-half track displaced from the even-numbered concentric track centerlines. Both the first and second servo burst data are read simultaneously utilizing the data transducers associated with the surfaces of the respective data storage disks and the envelopes of each of the servo burst signals are simultaneously, separately detected.

Abstract: A micro-Winchester disk drive system particularly suited to meet the demands of a portable computer system. The micro-Winchester disk is a Winchester disk of 85-100 mm in diameter. This disk drive system by virtue of its small size and vibration isolation is ideally suited for use in portable computer systems. The micro-Winchester disk drive system was developed to store data at a density of 600 tracks per inch utilizing open-loop positioning mechanism. This disk drive system provides fast access data storage for use with small business computers, terminals and microprocessor based systems, portable or otherwise, and many other areas where compact, rugged light-weight hard-disk storage is required. The disk drive system of the present invention normally utilizes either one or two hard disks such as Winchester disks and provides data storage on each disk in excess of 5 Megabytes, once the disks are formatted.