Apparatus and method for estimating initial position of rotor of motor

1. A permanent magnet synchronous machine (PMSM), the PMSM comprising:

a signal processor for outputting an angular error component from a change amount of a q-axis current in an estimated rotor reference frame;

a position estimator for estimating an electrical position of a rotor from the angular error component;

a magnetic pole determination portion for outputting magnetic pole determination information according to a sign of a magnetic pole determination signal determined based on a change amount of a d-axis current in the estimated rotor reference frame and based on a d-axis voltage; and

a first addition portion for outputting an initial position of the rotor by adding the magnetic pole determination information to the electrical position,

wherein the PMSM controls a torque of the rotor based on the initial position of the rotor, and

wherein the magnetic pole determination information is π when the magnetic pole determination signal has a positive sign, and is 0 when the magnetic pole determination signal has a negative sign.

2. The PMSM of claim 1 , wherein the magnetic pole determination portion determines the magnetic pole determination signal based on a fundamental wave component of the change amount of the d-axis current.

3. The PMSM of claim 1 , further comprising:

a first delay portion for delaying the q-axis current;

a second delay portion for delaying the d-axis current;

a first operation portion for determining the change amount of the q-axis current by operating a difference between the q-axis current and the delayed q-axis current; and

a second operation portion for determining the change amount of the d-axis current by operating a difference between the d-axis current and the delayed d-axis current.

4. The PMSM of claim 3 , wherein the first and second delay portions delay the q-axis current and the d-axis current by one sampling period, respectively.

5. The PMSM of claim 1 , wherein the signal processor delays the d-axis voltage, and outputs the angular error component by using a sign of the delayed d-axis voltage and the change amount of the q-axis current.

6. The PMSM of claim 5 , wherein the signal processor includes:

a third delay portion for delaying the d-axis voltage by a predetermined sampling period;

a first sign determination portion for determining the sign of the delayed d-axis voltage; and

a third operation portion for determining the angular error component by multiplying the sign of the delayed d-axis voltage by the change amount of the q-axis current.

7. The PMSM of claim 6 , wherein the third delay portion delays the d-axis voltage by two sampling periods.

8. The PMSM of claim 1 , wherein the position estimator includes:

a first application portion for applying a proportional gain to the angular error component;

a second application portion for applying an integral gain to the angular error component;

a first integral portion for integrating an output of the second application portion;

a second addition portion for adding an output of the first application portion to an output of the first integral portion; and

a second integral portion for integrating an output of the second addition portion to determine the electrical position of the rotor.

9. The PMSM of claim 1 , wherein the magnetic pole determination portion includes:

a fourth delay portion for delaying the d-axis voltage;

a second sign determination portion for determining a sign of the delayed d-axis voltage;

a fourth operation portion for multiplying the sign of the delayed d-axis voltage by the change amount of the d-axis current;

a fifth operation portion for multiplying an output of the fourth operation portion by the d-axis voltage; and

an integrator for integrating an output of the fifth operation portion and thereby outputting the magnetic pole determination signal.

10. The PMSM of claim 9 , wherein the magnetic pole determination portion further includes:

a determination portion for outputting a first angle when the magnetic pole determination signal has a positive sign, and for outputting a second angle when the magnetic pole determination signal has a negative sign;

a providing portion for providing a delta function which becomes 1 after a predetermined time lapses; and

a sixth operation portion for outputting the magnetic pole determination information by multiplying the delta function by an output of the determination portion.

11. The PMSM of claim 10 , wherein the first angle is π, and the second angle is 0.

12. The PMSM of claim 1 , wherein if the magnetic pole determination signal has a positive sign, the first addition portion adds π to the electrical position to determine the initial position.

13. The PMSM of claim 1 , wherein if the magnetic pole determination signal has a negative sign, the first addition portion determines the electrical position as the initial position.

14. The PMSM of claim 9 , wherein the fourth delay portion delays the d-axis voltage by two sampling periods.

15. A controlling method for a permanent synchronous machine (PMSM), the method comprising:

determining an angular error component from a change amount of a q-axis current in an estimated rotor reference frame;

estimating an electrical position of a rotor from the angular error component;

determining magnetic pole determination information according to a sign of a magnetic pole determination signal determined based on a change amount of a d-axis current in the estimated rotor reference frame and based on a d-axis voltage;

determining an initial position of the rotor by adding the magnetic pole determination information to the electrical position; and

controlling a torque of the rotor based on the initial position of the rotor,

wherein the magnetic pole determination information is π when the magnetic pole determination signal has a positive sign, and is 0 when the magnetic pole determination signal has a negative sign.