DC MOTOR ANGULAR VELOCITY ESTIMATING METHOD OF AN ELECTRIC POWER STEERING SYSTEM BY USING AN ANGULAR VELOCITY ESTIMATION FORMULA ACCORDING TO MOTOR SUPPLY VOLTAGE

摘要

PURPOSE: A DC(Direct Current) motor angular velocity estimating method of an electric power steering system is provided to decrease a big estimation error in a range with fine angular velocity by detecting pure outer back electromotive force and estimating the angular velocity of a DC motor according to an angular velocity formula. CONSTITUTION: A DC(Direct Current) motor angular velocity estimating method of an electric power steering system is composed of steps for judging if an electric current of a motor is zero or below a constant value(S11); determining that only pure outer back electromotive force is generated if the electric current of the motor is zero or below the constant value and calculating the angular velocity of the DC motor by a third formula(S12); and judging that the pure outer back electromotive force is not merely generated if the current of the motor is not zero or below the constant value and calculating the angular velocity of the motor by first and second formulas according to motor supply voltage if the current of the motor is not zero or over the constant value(S13).