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ELECTRIC POWER STEERING APPARATUS

  • US 20070284180A1
  • Filed: 06/07/2007
  • Published: 12/13/2007
  • Est. Priority Date: 06/07/2006
  • Status: Abandoned Application
First Claim
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1. An electric power steering apparatus comprising:

  • a steering torque detection part which detects steering torque inputted to a steering mechanism;

    a current command value calculation part which calculates a current command value on the basis of at least the steering torque detected by the steering torque detection part;

    an electric motor which generates a steering assist torque applied on a steering shaft of the steering mechanism; and

    a motor control part which controls the electric motor by a pulse-width modulating signal on the basis of the current command value,wherein the motor control part comprises;

    a motor torque detection part which detects a motor torque generated between the electric motor and the steering shaft;

    a motor torque change rate detection part which calculates a change rate of the motor torque detected by the motor torque detection part; and

    a duty ratio limiting part which judges that a duty ratio limiting condition is satisfied when the change rate of the motor torque calculated by the motor torque change rate detection part is not less than a threshold value for judging a steering limit, andwherein the duty ratio limiting part fixes a duty ratio of the pulse-width modulating signal to a predetermined value for limiting a torque transmitted to a torque transmitting member between the steering shaft of the steering mechanism and a steering road wheel when the duty ratio limiting condition is satisfied.

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