Abstract: A data storage and retrieval system is disclosed which includes a transducer for data transfer with a rotating magnetic disk having a multiplicity of addressable annular data tracks formed concentrically on at least one of the major surfaces thereof. The transducer reads the prerecorded addresses on the successive data tracks being traversed during each track seeking operation. Periodically sampling the track addresses being read by the transducer, a microprocessor determines the data track on which the transducer is currently positioned, and computes the remaining number of tracks to be traversed until the transducer arrives at a destination track. Should there be errors in the track address samples, due for example to the failure of the transducer to read some track addresses, the microprocessor might become unable to determine the correct current transducer position, with the consequent possibility of transducer overrun beyond the data storage zone on the disk surface.

Abstract: A motor speed control system is disclosed as adapted for the traveling speed control of a transducer on a pivotal support beam driven by a voice coil motor in a rotating disk data storage apparatus. The speed control system includes a speed sensor having a speed sensing coil for electromagnetically generating a motor speed signal representative of the actual traveling speed of the transducer. Since the speed sensing coil is of necessity disposed adjacent the drive coil of the voice coil motor, the motor speed signal contains a noise component due to the mutual induction between the two coils. For the elimination of the noise component from the motor speed signal, which is to be utilized for the feedback speed control of the voice coil motor, a differentiator circuit is provided for deriving a noise suppression signal, which is equivalent to the noise component, from a motor speed control signal representative of the desired traveling speed of the transducer.

Abstract: A transducer position control method suitable for practice with a magnetic disk of the kind wherein the data tracks are divided into a plurality of groups, each group of tracks being individually identified by the same set of address code characters prerecorded thereon for the simplicity of the address code. As the transducer travels at controlled speed from a departure track to a destination track, reading the address code characters on the successive tracks being traversed, the address code characters are sampled at regular intervals. The transducer may skip over one complete track group during each sampling interval as the seek speed is made higher than heretofore. Therefore, each time an address code sample is obtained, the actual rate of transducer moving during the previous sampling interval is compared with an expected rate of transducer movement for the same sampling interval in order to determine the current transducer position and the remaining number of tracks to the destination track.

Abstract: A system for positioning a transducer with respect to a multiplicity of concentric annular data tracks on a rotating hard magnetic disk. Included is a differential amplifier for providing an output proportional to the difference between a transducer speed signal representative of the actual traveling speed of the transducer and a seek speed signal representative of desired variable speed at which the transducer is to be moved to any desired destination track. A low pass filter is provided for eliminating an undesirable higher frequency component from the output from the differential amplifier, before this output is sent to a driver circuit for a transducer positioning motor such as a voice coil motor. In order to minimize the adverse effects arising from the phase lag introduced by the low pass filter, this filter is made switchable between two different cutoff frequencies. Each track seeking operation starts with the low pass filter held at the lower cutoff frequency.

Abstract: A disklike record medium such as a magnetic data storage disk, and a closed-loop servo control system for positioning a transducer such as a magnetic read/write head on any of a multiplicity of concentric tracks on the record medium. The tracks on the record medium are divided into a plurality of groups, and each track of each group has a different code character prerecorded thereon as in the form of discretely magnetized regions. All the groups of tracks have the same set of code characters assigned thereto for the simplicity of the code characters. Read by the transducer, the code characters enable the control system to individually identify all the tracks of all the groups. In response to an externally supplied track command indicative of a destination track on which the transducer is to be positioned, and to internally supplied track code data, the control system causes translation of the transducer from a departure track to the destination track during track seek operations.