Head position control system for fixed drive including position encoder, temperature sensor and embedded fine servo information

A head positioner control system for use within a fixed disk drive data storage subsystem for controlling a hermetically enclosed had and disk assembly of the system including therewith a drive had positioner means for positioning a drive data transducer head relative to selected ones of multiple concentric data tracks formed on a data storage surface of a drive storage disk rotating relative to a drive base, the control system comprising:

• coarse servo means including position encoder means within the head and disk assembly and coupled between the drive head positioner and the drive base for generating and putting out coarse head position information,
• fine servo means including embedded fine servo information readible by the drive data transducer at selected locations on the data surface for providing fine head position information,
• temperature sensor means within the head and disk assembly in direct thermal contact with the drive base for sensing temperature of the drive base at the immediate vicinity of the position encoder means and for putting out sensed temperature information,
• head positioner driver means for supplying driving current to the drive head positioner,
• drive controller means responsive to the fine servo means for obtaining and storing fine head position information during a calibration operation, responsive to changes in the sensed temperature information provided by the temperature sensor means for carrying out a recalibration operation for updating the stored fine head position information as a reference and angle offset, and further responsive to requests for storage and retrieval of data blocks via an interface means with a host computing system, the drive controller means being connected to the coarse servo to receive the coarse position information and connected to the head positioner driver means for generating a head position signal to cause the head positioner to seek to a data storage track, to settle at the data storage track, and to follow a centerline of the data storage track during transfer of a data block from or to the data storage track, the head position signal being calculated by the drive controller means in reference to the coarse position information currently being supplied to the controller means by the coarse servo and in further reference to the reference and angle offset stored within the controller means.

A track following servo for a disk drive comprising a data storage disk rotating at a predetermined constant velocity relative to a base, and a positionable data transducer head for writing data to, and reading data from, a multiplicity of concentric data tracks defined on a storage surface of the data storage disk during data track following operations, the data transducer head being positioned by head position actuator means referenced to the base and which is controlled by the track following servo at least during the data track following operations, comprising:

• polyphase position encoder means coupled between the head position actuator means and the base for providing phase shifted relative position signals,
• analog to digital conversion means for converting the phase shifted relative position signals into digital measured position values,
• digital processing means for processing the digital measured position values into a measured angle of the actuator means relative to the base,
• reference angle determination means for determining from prestored reference and angle slope digital values a reference angle corresponding to track centerline at a particular data track being followed,
• digital difference junction means for determining a difference between the measured angle and the reference angle to provide an angle error value,
• actuator driver means for converting the angle error value into a correction signal and for applying the correction signal to the actuator means thereby to cause the data transducer head to approach and follow the centerline of the said particular data track during the track following operation.