Mechanism of interior permanent magnet machine initial position detection

1. A system for determining an initial rotor position of an interior permanent magnet (IPM) machine having a rotor and a stator, the system comprising:

a drive circuit in operative and electrical communication with each phase of the IPM machine; and

a controller in electrical communication with the drive circuit, the controller configured to engage the drive circuit to selectively apply a voltage signal to each phase of the stator of the IPM machine, detect a current signal through each phase corresponding to the applied voltage signal, and calculate the initial rotor position based on a least squares analysis between at least the voltage signal, the current signal and a predefined inductance of the IPM machine including both self-inductance and mutual inductance associated with the IPM machine, the controller configured to calculate the initial rotor position based at least partially on the following equation:

(

cos

⁢

⁢

2

⁢

θ

sin

⁢

⁢

2

⁢

⁢

θ

)

=

(

H

H

⁢

H

)

-

1

⁢

H

H

[

1

j

⁢

⁢

ω

⁢

(

V

a

V

b

V

c

)

-

R

jω

⁢

(

I

a

I

b

I

c

)

-

h

1

]

.

2. The system of claim 1 , wherein the controller and the drive circuit is configured such that the voltage signal applied to each phase of the IPM machine has a substantially high frequency and a substantially low amplitude.

3. The system of claim 2 , wherein the frequency of the voltage signal is approximately 240 Hz.

4. The system of claim 1 , wherein the stator of the IPM machine includes three phases.

5. The system of claim 1 , wherein the controller is further configured to monitor a rotor speed sensor configured to detect a rotor speed of the rotor relative to the stator of the IPM machine.

6. The system of claim 5 , wherein the controller is configured to engage the drive circuit to apply the voltage signal only when the detected rotor speed of the IPM machine is confirmed to be zero.

7. The system of claim 1 , wherein the controller is configured to automatically calculate the initial rotor position at startup of the IPM machine.

8. The system of claim 1 , wherein the controller incorporates the amplitude and phase of each voltage signal for each phase, and the amplitude and phase of each current signal for each phase into the least squares analysis.

9. The system of claim 1 , wherein the controller is preprogrammed with predefined rotor position values that have been mapped with known ranges of voltage and current signals.

10. The system of claim 1 , wherein the controller is configured to automatically calculate the initial rotor position when the IPM machine is determined to be at rest.

11. The system of claim 1 , wherein the controller is configured to automatically calculate the initial rotor position when a predefined operating condition of an associated electric drive system is satisfied.

12. A method of determining an initial rotor position of an interior permanent magnet (IPM) machine having a rotor and a stator, the method comprising the steps of:

applying a voltage signal to each phase of the stator of the IPM machine;

determining a current signal through each phase corresponding to the applied voltage; and

calculating the initial rotor position based on a least squares analysis between at least an amplitude and a phase of each voltage signal, an amplitude and a phase of each current signal, and a predefined inductance of the IPM machine including at least a self-inductance value and a mutual inductance value associated with the IPM machine, the least squares analysis including the following equation:

(

cos

⁢

⁢

2

⁢

⁢

θ

sin

⁢

⁢

2

⁢

⁢

θ

)

=

(

H

H

⁢

H

)

-

1

⁢

H

H

⁡

[

1

j

⁢

⁢

ω

⁢

(

V

a

V

b

V

c

)

-

R

jω

⁢

(

I

a

I

b

I

c

)

-

h

1

]

.

13. The method of claim 12 , wherein the controller and the drive circuit is configured such that the voltage signal applied to each phase of the IPM machine has a substantially high frequency and a substantially low amplitude.

14. The method of claim 13 , wherein the frequency of the voltage signal is approximately 240 Hz.

15. The method of claim 12 , wherein the IPM machine includes three phases.

16. The method of claim 12 , further comprising the step of monitoring a rotor speed sensor configured to detect a speed of the rotor relative to the stator of the IPM machine.

17. The method of claim 16 , wherein the voltage signal is applied only when the detected rotor speed of the IPM machine is confirmed to be zero.

18. The method of claim 12 , wherein the initial rotor position is automatically calculated at startup of the IPM machine.

19. The method of claim 12 , wherein the initial rotor position is further based at least partially on a predefined inductance of the IPM machine.

20. A method of automatically determining an initial rotor position during startup of an interior permanent magnet (IPM) machine having a rotor and a stator, the method comprising the steps of:

receiving a sensor signal from a rotor speed sensor indicative of a speed of the rotor relative to the stator to confirm zero rotor speed;

applying a sinusoidal voltage signal to each phase of the stator of the IPM machine, each voltage signal having a substantially high frequency and a substantially low amplitude;

detecting a current signal through each phase corresponding to the applied voltage signal;

determining a relationship between the voltage signal, the current signal and the initial rotor position based on a least squares analysis and a predefined inductance of the IPM machine including at least a self-inductance value and a mutual inductance value associated with the IPM machine, the least squares analysis including the following equation:

(

cos

⁢

⁢

2

⁢

⁢

θ

sin

⁢

⁢

2

⁢

⁢

θ

)

=

(

H

H

⁢

H

)

-

1

⁢

H

H

⁡

[

1

jω

⁢

(

V

a

V

b

V

c

)

-

R

j

⁢

⁢

ω

⁢

(

I

a

I

b

I

c

)

-

h

1

]

;

⁢

and

and

calculating the initial rotor position based on the relationship.