Stepper motor torque variance compensation using varied applied voltage

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.