Position sensing method and apparatus for synchronous motor generator system

1. A position sensing apparatus for deriving rotor position of a synchronous machine from signals output from said machine, said apparatus comprising:

a bandpass filter that filters phase voltage signals output from main stator windings of said synchronous machine during AC excitation, thereby extracting a rotor position-indicating component from said phase voltage signals;

a converter that converts the filtered phase voltages into balanced two-phase quadrature signals, said balanced two-phase quadrature signals indicating positioning of said rotor; and

an excitation controller for controlling AC excitation frequency, of an AC excitation supplied to an exciter field winding of a stator of said machine, as a function of rotor speed, thereby increasing a position detection range of said position sensing apparatus.

2. The position sensing apparatus of claim 1 , wherein said synchronous machine is a synchronous brushless machine.

3. The position sensing apparatus of claim 1 , wherein said rotor is on a shaft coupled to a gas turbine engine of an aircraft.

4. The position sensing apparatus of claim 1 , wherein said bandpass filter has a fixed passband over a range of rotor speeds.

5. The position sensing apparatus of claim 4 , wherein the fixed passband is defined as a function of:

f sig =2 ·N ph ·f init +f e — st ·(4 ·N ph ±1)

wherein f sig is a frequency of a signal containing rotor position information, N ph is a number of phases in an exciter stator, f e — st is the electrical frequency of a main stator voltage, and f init is an initial AC excitation frequency.

6. The position sensing apparatus of claim 1 , wherein the two-phase quadrature signals are used as inputs to emulate a position sensor in a drive system for the synchronous machine.

7. The position sensing apparatus of claim 6 , wherein the two-phase quadrature signals are used as inputs to emulate a resolver.

8. The position sensing apparatus of claim 1 , wherein

a Clarke transformation is used to convert the filtered phase voltages into the balanced two-phase quadrature signals, and

said position sensing apparatus further comprises:

a rectifier that rectifies exciter voltage signals of the said synchronous machine; and

a second bandpass filter that filters the rectified exciter voltage signals to generate a reference signal.

9. The position sensing apparatus of claim 1 , wherein AC excitation amplitude is maintained substantially constant over a range of rotor speeds.

10. The position sensing apparatus of claim 1 , wherein AC voltage at output terminals of the machine is maintained below a preset level due to a field weakening caused by the AC excitation frequency control.

11. The position sensing apparatus of claim 1 , wherein said excitation controller varies AC excitation frequency to substantially maximize the ratio between a phase voltage frequency component carrying rotor position information and a rotor frequency component.

12. A position sensing method for deriving rotor position of a synchronous machine from signals output from said machine, said method comprising:

bandpass filtering phase voltage signals output from main stator windings of said synchronous machine during AC excitation, thereby extracting a rotor position-indicating component from said phase voltage signals;

converting the filtered phase voltages into balanced two-phase quadrature signals, said balanced two-phase quadrature signals indicating positioning of said rotor; and

controlling AC excitation frequency, of an AC excitation supplied to an exciter field winding of a stator of said machine, as a function of rotor speed, thereby increasing the position detection range of the position sensing method.

13. The position sensing method of claim 12 , wherein said synchronous machine is a synchronous brushless machine.

14. The position sensing method of claim 12 , wherein said rotor is on a shaft coupled to a gas turbine engine of an aircraft.

15. The position sensing method of claim 12 , wherein said bandpass filtering is performed using a fixed passband over a range of rotor speeds.

16. The position sensing method of claim 15 , wherein the fixed passband is defined as a function of:

f sig =2 ·N ph ·f init +f e — st ·(4 ·N ph ±1)

wherein f sig is a frequency of a signal containing rotor position information, N ph is a number of phases in an exciter stator, f e — st is the electrical frequency of a main stator voltage, and f init an initial AC excitation frequency.

17. The position sensing method of claim 12 , wherein the two-phase quadrature signals are used as inputs to emulate a position sensor in a drive system for the synchronous machine.

18. The position sensing method of claim 17 , wherein the two-phase quadrature signals are used as inputs to emulate a resolver.

19. The position sensing method of claim 12 , wherein a Clarke transformation is used to convert the filtered phase voltages into the balanced two-phase quadrature signals, and

said position sensing method further comprises:

rectifying exciter voltage signals of said synchronous machine; and

bandpass filtering the rectified exciter voltage signals to generate a reference signal.

20. The position sensing method of claim 12 , wherein AC excitation amplitude is maintained substantially constant over a range of rotor speeds.

21. The position sensing method of claim 12 , wherein the AC voltage at output terminals of the machine is maintained below a preset limit due to a field weakening caused by the AC excitation frequency control.

22. The position sensing method of claim 12 , wherein said AC excitation frequency control varies AC excitation frequency to substantially maximize the ratio between a phase voltage frequency component carrying rotor position information and a rotor speed frequency component.