Patent ID: 8855857

Claim:
An electric motor controller for controlling an electric motor and that includes a rotor and a stator that faces the rotor, the electric motor controller comprising: a current drive unit that drives the electric motor based on an axis current value in a rotating coordinate system that rotates in accordance with a control angle that is a rotational angle used in a control and calculated without using a rotational angle sensor that detects a rotation angle of the rotor so that the control angle is determined independently from the rotation angle of the rotor; an addition angle calculation unit that calculates, without detecting a change of the rotation angle of the rotor, an addition angle that is added to the control angle; a control angle calculation unit that obtains a current value of the control angle by adding the addition angle to an immediately preceding value of the control angle in each predetermined calculation cycle; a torque detection unit that detects a torque applied to a motor driven member except a motor torque applied thereto by the electric motor; a changing unit that changes a parameter for controlling the electric motor in accordance with a detected torque that is detected by the torque detection unit; a suspending unit that suspends such operation of the changing unit until an absolute value of the detected torque becomes equal to or smaller than a predetermined value; and a command torque setting unit that sets a command torque based on a predetermined characteristic, wherein the addition angle calculation unit calculates the addition angle based on a proportional integral control to a deviation of the detected torque from the command torque without using a rotational angle sensor that detects a rotation angle of the rotor, wherein the changing unit changes the addition angle as the parameter to zero when the absolute value of the detected torque is equal to or smaller than the predetermined value, and wherein the changing unit changes the parameter when the absolute value of the detected torque is equal to or larger than a first value that is equal to or larger than the predetermined value.