International Business Machines Corporation

Christopher N Wallis

Philip J Murfet

Michael John Palmer

Adrian C Lee

William John Case

Thomas Winlow

Stephen Furniss

A data storage device for use with a rotatable data storage medium having a data head and a controller for controlling movement of said data head characterized in that said controller varies the time taken for moving said data head between given positions in response to the state of said device. Particular embodiments of the invention coordinate the movement of the data head with the rotational position of the data storage medium so that the data head arrives at the desired position at the same time as the portion of the data storage medium to be accessed arrives beneath the data head. In other embodiments the time taken to move the data head between given positions is increased if the temperature of the mechanism for moving the data head exceeds a predetermined value.

Actuator arm controller for a storage device

An asynchronous serial data receiver utilizes plural samples of each data bit in a word to assure detection and reading of the midpoint of each bit to mitigate problems associated with noise and mismatches between the data and sampling rates. To this end, a shift register having plural stages for each bit samples the data stream at a clock rate which is a multiple of the data rate which provides multiple samples of each incoming bit. When the data word is fully read into the shift register the start bit is detected and initiates a parallel transfer of the data word using bit values taken from the midpoint of each bit period.

Asynchronous serial data receiver with capability for sampling the

An asynchronous serial data receiver for receiving a stream of data bits, characterized by a plurality of shift registers (54) into which samples corresponding to points within said data bit stream are read, different shift registers (54) holding a different set of said samples, said points being separated by most one half of a data bit period, and a decoder (60-90) responsive to said samples held in said shift registers (54) for recognizing points of known phase within said data assessed relative to which samples which corresponding to points within said data bits may be identified for reading. The invention provides a high speed serial receiver which is particularly suitable for use within disc drives and data storage and retrieval systems in general. The serial data receiver of the present invention does not require a clock synchronized with the incoming data. Furthermore the serial data receiver is able to share the sampling of the data bit stream between a plurality of shift registers (54) none of which need be clock more than once per data bit period.

Serial data receiver with phase shift detection

The performance of a track-following servo system for a disk file is improved by the feeding forward of a prediction of track eccentricity into the normal feedback control loop. The eccentricity related function is derived by combining functions of the position error signal and of the input signal to the head position actuator during at least one revolution of the disk. The eccentricity function is stored and then fed forward to the actuator during a subsequent revolution of the disk. The eccentricity function may be a track shape position signal formed from the difference of the PES and the double time integral of the actuator current. Alternatively it may be an actuator current profile formed from the difference between the actual current and the double time derivative of the PES.

Track following servo system for a disk file

Servo records provided at intervals on a record medium are used in a sampled servo system to define data tracks on the medium. Asperities in the medium, or problems arising from the servo writing process can in some instances lead to mis-alignment of a servo path 33 defined by a servo sample with the corresponding desired data track. This causes non-zero position error signals to be produced even when the track following head is accurately positioned over the data track. The problem is solved by measuring the position error signals derived from each servo sample with the head constrained in the correct on-track position. The value of each of these position error signals is then stored as a digital number forming part of a correcting byte in the data section immediately preceding the associated faulty sample. The correction byte also includes a flag bit which is set to demark the next servo sample if the error is so large as to be deemed uncorrectable. Thereafter, in use if the flag bit is unset, the servo system reads the digital number from the correction byte, and uses it to dynamically correct the position error signal from the associated faulty servo sample. If the flag bit is set, the position error signal from the previous sample is carried forward and used instead of the position error signal from the current sample.

Sampled servo position control system

An actuator comprising a transformer having a fixed primary winding on a magnetic core and a pivotally movable coil linked with the magnetic core and forming a secondary winding of the transformer. A permanent magnet generates a static magnetic field in which the coil is disposed. A transducer arm capable of pivotal movement is attached to the coil. When a current pulse is applied to the primary winding, a current is induced in the coil which reacts with the static magnetic field to cause pivotal movement of the coil and attached arm.

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Winchester, United Kingdom

Christopher N Wallis