Motor drive apparatus and motor drive method

A motor drive apparatus to perform vector control of a motor which includes a stator having a u-phase coil, a v-phase coil and a w-phase coil and a rotor having a permanent magnet fixed thereto, comprising:

• an A/D converter which acquires a first motor current constituted with a u-phase motor current, a v-phase motor current and a w-phase motor current flowing respectively through the u-phase coil, the v-phase coil and the w-phase coil and which respectively digitalizes the u-phase motor current, the v-phase motor current and the w-phase motor current;
• a vector control unit which generates a second motor current constituted with a d-axis motor current and a q-axis motor current by performing coordinate conversion to convert from a uvw-coordinate system into a dq-coordinate system on the first motor current digitalized by the A/D converter;
• and which acquires a first motor voltage constituted with a d-axis motor voltage and a q-axis motor voltage based on the second motor current, a motor parameter, and a desired angular speed of the rotor;
• and which generates a second motor voltage constituted with a u-phase motor voltage, a v-phase motor voltage and a w-phase motor voltage by performing reverse conversion of the first coordinate conversion on the first motor voltage;
• the motor parameter including a motor resistance, a d-axis motor inductance, a q-axis motor inductance and a motor inductive voltage constant;
• a PWM generator which generates a PWM signal for driving the motor based on the second motor voltage acquired by the vector control unit;
• and
• a parameter estimation unit which estimates the motor resistance, the d-axis motor inductance and the q-axis motor inductance based on a maximum peak value and a minimum peak value of the d-axis motor current and a maximum peak value and a minimum peak value of the q-axis motor current in a direct current excitation control state where the rotor of the motor is fixed at a predetermined rotor angle;
• and which estimates the motor inductive voltage constant based on a predetermined angular speed, the motor resistance, the d-axis motor inductance and the q-axis motor inductance in a forced commutation control state where the rotor of the motor is rotating at the predetermined angular speed;
• and which loads the estimated motor parameter to the vector control unit.