US 5,182,685 AGranted

Stepper motor torque variance compensation using varied applied voltage

AssigneeSeagate Technology LLC

InventorsJames N. Krause, Brian P. Tremaine, Litko R. Chan

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Abstract

The present invention utilizes the output of a voltage regulator to control the drive voltage to the stepper motor driven transducer positioning system. This technique will significantly reduce the access time. More specifically, in this invention, the output of a digital-to-analog converter (DAC) is used to control the output voltage level of a voltage regulator circuit which supplies the voltage of the stepper motor drive transistors. In order to optimize the drive voltage output from the voltage regulator to the stepper motor for each disc drive, circuitry is provided to determine the minimum settling time for a specific actuator movement resulting from the application of a given drive voltage. A detector circuit monitors the settling time of the head over the center of the target track. The data identifying the voltage regulator output which results in minimum settling time is stored and used from then on for that stepper motor disc drive system as the optimum access tuned voltage. This data will be applied by the microprocessor to a DAC, and output from the voltage regulator to the stepper motor drivers during each stepping sequence. Typically, this tuning process is originally accomplished when the disc drive is first powered on and is part of the normal power-on recalibration routine.

Claims13

Dependent claims

In a disc drive system comprising at least one constantly rotating disc for storing data on concentric tracks,

means for rotatably supporting said disc,
an actuator for supporting a transducer over said disc for reading and writing digital information on said disc tracks,
positioning means coupled to said actuator for selectively positioning said transducer in alignment with one of said disc tracks as a target track on said rotating disc for reading and writing data,
said positioning means comprising a multi-phase stepper motor for moving said actuator and thereby said transducer from an initial disc track to said target track, and
voltage control means having outputs connected to the phases of said stepper motor, said voltage control means including:
means for deriving and selecting an optimum voltage to be applied to drive transistors associated with energized phases of the motor, the means for deriving and selecting the optimum voltage derives and selects the optimum voltage on command to compensate for aging, temperature and general wear of the disc drive system then existing;
means for applying different voltages to said phases of said stepper motor, measuring a settling time of said motor to each said voltage, and selecting the voltage which provides the shortest settling time as the optimum voltage;
and
microprocessor means for analyzing the response of said stepper motor to a voltage applied to the phases of said stepper motor, and means responsive to said microprocessor for applying said optimum voltage to the stepper motor phases.

6 more elements

In a disc drive system comprising at least one constantly rotating disc for storing data on concentric tracks, a method for rapidly positioning a transducer in response to a stepper motor over a constantly rotating disc, comprising the steps of

selectively activating the multiple phases of a multi-phase stepper motor for moving said transducer from an initial track to a target track, and
controlling voltages connected to the phases of said stepper motor for energizing the phases of the stepper motor, monitoring the settling time of the motor by detecting the number of target track crossings by the transducer before the transducer settles on the target track, selecting an optimum voltage having the shortest settling time based on at least two monitored SEEKs to said target track with said disc drive and motor, and applying said optimum voltage to drive transistors associated with energized phases of the motor.

Dependencies are inferred from the claim text.