Patent ID: 6841968

Claim:
A driver circuit for driving a permanent-magnet electric motor, comprising: an inverter for generating an electric current to be applied to the permanent-magnet motor, according to a commanded voltage value applied thereto; a motor-drive-current detector operable to detect the drive current of the motor; a current detector operable to detect a d-axis current and a q-axis current which are respectively an exciting current component and a torque current component of the detected drive current; and a controller operable to calculate a d-axis current difference between the detected d-axis current and a commanded d-axis current value, and a q-axis current difference between the detected q-axis current and a commanded q-axis current value, said controller being further operable to calculate a d-axis difference signal which is a function of a d-axis input voltage of the motor and is not a function of a q-axis input voltage of the motor, and a q-axis difference signal which is a function of the q-axis input voltage and is not a function of the d-axis input voltage, said controller controlling said inverter on the basis of the calculated d-axis and q-axis difference signals, such that the d-axis and q-axis difference signals are zeroed, wherein said controller generates a value xd as said d-axis difference signal, and a value xq as said q-axis difference signal, based on factors including an inductance of the motor and an electric resistance of the motor, wherein said factors further include an angular velocity of the motor, wherein the values xd and xq being represented by the following equation: ( xd xq ) = ( R - ω ⁢ ⁢ dLd - ω ⁢ ⁢ Lq ω ⁢ ⁢ Ld R - ω ⁢ ⁢ dLq ) ⁢ ( jd jq ) + ( ω ⁢ ⁢ dLd 0 0 ω ⁢ ⁢ dLq ) ⁢ ( idr - id iqr - iq ) ⅆ ⅆ t ⁢ ( jd jq ) = ( - ω ⁢ ⁢ d 0 0 - ω ⁢ ⁢ d ) ⁢ ( jd jq ) + ( ω ⁢ ⁢ d 0 0 ω ⁢ ⁢ d ) ⁢ ( idr - id iqr - iq ) wherein id is said d-axis current, iq is said q-axis current, idr is said commanded d-axis current value, iqr is said commanded q-axis current value, vd is a d-axis voltage applied to the motor, vq is a q-axis voltage applied to the motor, Ld is an inductance of the d-axis of the motor, Lq is an inductance of the q-axis of the motor, R is an electric resistance of the motor, ω is an angular velocity of a rotor of the motor, Φ is a number of magnetic cross fluxes of a permanent magnet of the motor, jd is a d-axis state quantity of said controller, jq is a q-axis state quantity of said controller, and ωd is a coefficient.