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Position Hysteresis Error Reduction in Stepper Motors Using Dither Currents During Microstepping

IP.com Disclosure Number: IPCOM000041244D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Chiang, WW: AUTHOR

Abstract

Position hysteresis error in stepper motors can be caused by magnetic hysteresis and/or mechanical friction. The position hysteresis error becomes larger during microstepping than in regular stepping, even though the driving and loading conditions remain the same. The position hysteresis error can be substantially reduced, for example to less than half, by dithering the motor currents about the nominal values during microstepping. The method does not require any changing of the mechanical design of the stepper motor and still retains the convenience of open loop control. The only modification required is the electronic motor control circuit to apply the dither currents.

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Position Hysteresis Error Reduction in Stepper Motors Using Dither Currents During Microstepping

Position hysteresis error in stepper motors can be caused by magnetic hysteresis and/or mechanical friction. The position hysteresis error becomes larger during microstepping than in regular stepping, even though the driving and loading conditions remain the same. The position hysteresis error can be substantially reduced, for example to less than half, by dithering the motor currents about the nominal values during microstepping. The method does not require any changing of the mechanical design of the stepper motor and still retains the convenience of open loop control. The only modification required is the electronic motor control circuit to apply the dither currents.

The selection of the frequency of the dither current is determined by determining the mechanical frequency response of the system which the stepper motor is driving. A frequency close to an anti-resonant frequency is the optimum frequency at which the dither current should be applied to the nominal current value in order to reduce the position hysteresis. The application of dither current at an anti-resonant frequency of the mechanical system will allow the maximum amplitude of dither current to be applied to break the friction and/or magnetic hysteresis.

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