Motor control device and motor control method

1. A motor control device to drive an electric motor, the motor control device comprising:

a first torque estimator to determine a first torque estimation value based on at least a coil interlinkage flux and a motor current;

a second torque estimator to determine a second torque estimation value based on at least a motor input power and a motor rotational speed; and

a weighting adjuster to adjust weightings respectively applied to the first torque estimation value and the second torque estimation value in accordance with a predetermined condition, and to calculate a torque estimation value of the electric motor.

2. The motor control device according to claim 1 , wherein

the weighting adjuster calculates a torque estimation value {circumflex over (T)} of the electric motor according to:

{circumflex over (T)} =(1−α) T 1 +αT 2   (1)

where, T 1 represents the first torque estimation value, T 2 represents the second torque estimation value, and α(0≤α≤1) represents a weighting coefficient of the weighting adjustment; and

T 1 =N pp {(ϕi q +(L d −L q )i d i q }, where N pp represents a number of motor pole pairs, L d and L q represent motor inductances in a rotation vector coordinate system, ϕ represents the coil interlinkage flux, and i d and i q represent the motor currents, and T 2 =P/ω m , where P represents the motor input power, and ω m represents the motor rotational speed.

3. The motor control device according to claim 2 , wherein the weighting adjuster is operable to adjust the weighting coefficient α based on an output of the electric motor as the predetermined condition.

4. The motor control device according to claim 2 , wherein the weighting adjuster is operable to adjust the weighting coefficient α based on a rotational speed of the electric motor as the predetermined condition.

5. The motor control device according to claim 2 , wherein the weighting adjuster is operable to adjust the weighting coefficient α based on a current flowing through a coil of the electric motor as the predetermined condition.

6. The motor control device according to claim 2 , further comprising an input power estimator to estimate the motor input power P using:

P=v d i d +v q i q −P c −P i   (2)

where, v d and v q represent voltages applied to the motor in the rotation vector coordinate system, P c represents a copper loss, and P i represents a loss other than the copper loss.

7. The motor control device according to claim 6 , further comprising a copper loss estimator to estimate the copper loss P c using:

P c =R ( i d 2 +i q 2 )  (3)

where, R represents a coil resistance value of the electric motor.

8. The motor control device according to claim 7 , further comprising:

a detector to detect a coil temperature of the electric motor; and

a corrector to correct the coil resistance value using the coil temperature.

9. The motor control device according to claim 1 , further comprising:

a detector to detect a magnet temperature of a magnet provided in a rotor of the electric motor; and

a corrector to correct a coil interlinkage flux of the electric motor using the magnet temperature.

10. The motor control device according to claim 1 , further comprising:

a current command value calculator to calculate a current command value based on the torque estimation value of the electric motor and a predetermined torque command value;

a pulse width modulation (PWM) signal generator configured to generate a predetermined PWM signal based on the current command value; and

an inverter controller configured or programmed to drive and control the electric motor using the PWM signal.

11. A motor control device of an electric power steering to assist a driver in steering a vehicle or the like, the motor control device comprising:

an electric motor to provide steering assistance to the driver; and

a driver to drive and control the electric motor by the motor control device according to claim 1 .

12. An electric power steering system comprising the motor control device of the electric power steering according to claim 11 .

13. An electric vehicle including an electric motor as a power source, the electric vehicle comprising:

a driver to drive and control the electric motor by the motor control device according to claim 1 .

14. A hybrid vehicle including an electric motor and an internal combustion engine as power sources, the hybrid vehicle comprising:

a driver to drive and control the electric motor by the motor control device according to claim 1 .

15. A motor control method for driving an electric motor, the motor control method comprising:

determining a first torque estimation value based on at least a coil interlinkage flux and a motor current;

determining a second torque estimation value based on at least motor input power and a motor rotational speed; and

adjusting weightings respectively applied to the first torque estimation value and the second torque estimation value in accordance with a predetermined condition, and calculating a torque estimation value of the electric motor.

16. The motor control method according to claim 15 , wherein

the adjusting weightings includes calculating a torque estimation value {circumflex over (T)} of the electric motor according to:

{circumflex over (T)} =(1−α) T 1 +αT 2   (1)

where T 1 represents the first torque estimation value, T 2 represents the second torque estimation value, and α(0≤α≤1) represents a weighting coefficient of the weighting adjustment; and

where, T 1 =N pp {ϕi q +(L d −L q )i d i q }, where N pp represents a number of motor pole pairs, L d and L q represent motor inductances in a rotation vector coordinate system, ϕ represents the coil interlinkage flux, and i d and i q represent the motor currents, and T 2 =P/ω m , where P represents the motor input power, and ω m represents the motor rotational speed.