Extended speed range operation of permanent magnet brushless machines using optimal phase angle control in the voltage mode operation

• US 6,373,211 B1
• Filed: 09/18/2000
• Issued: 04/16/2002
• Est. Priority Date: 09/17/1999
• Status: Expired due to Term

• Current Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust), Steering Solutions IP Holding Corporation (Nexteer Automotive Group Ltd.)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Nehl, Thomas Wolfgang, Naidu, Malakondaiah, Henry, Rassem Ragheb, Boules, Nady
• Primary Examiner(s): DANG, KHANH
• Application Number:
  US09/664,178
• Time in Patent Office: 575 Days
• Field of Search: 318/430-439, 318/139, 318/280-293, 180/248, 180/249, 180/443, 180/446, 180/79.1, 701/74, 701/89, 364/424, 364/51, 743/88.PS
• US Class Current: 318/432
• CPC Class Codes: B62D 5/046 Controlling the motor
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop
• CPC Class Codes: H02P 6/06 Arrangements for speed regulation of a single motor wherein the motor speed is measured and compared with a given physical value so as to adjust the motor speed
• CPC Class Codes: H02P 6/08 Arrangements for controlling the speed or torque of a single motor H02P6/10, H02P6/28 take precedence
• CPC Class Codes: H02P 6/10 Arrangements for controlling torque ripple, e.g. providing reduced torque ripple
• CPC Class Codes: H02P 6/17 and for generating speed information

Abstract

A voltage mode control method and apparatus for extending speed range operation from a sinusoidally excited permanent magnet motor is described. The method includes a determination of a maximum value from a first set of parameters with each parameter having a known maximum value as well as a reading of a second set of parameters. A computation of a first derived angle using the first set of parameters and the second set of parameters is then performed. A computation of amplitude of phase voltage and a second derived angle using the first derived angle follows. A resultant output comprising a set of derived command voltages for controlling a power circuit is created whereby the power circuit can achieve required torque levels with lower currents for power switches.

Claims

1. A voltage mode control method for extending speed range operation from a sinusoidally excited permanent magnet motor, comprising:

determining a known maximum allowed value from a first set of parameters with each parameter having said known maximum value;

reading a second set of parameters;

computing a first derived angle using said first set of parameters and said second set of parameters;

computing amplitude and a second derived angle of phase voltage vector using said first derived angle and a third set of parameters; and

outputting a set of derived command voltages for controlling a power circuit whereby the said power circuit can achieve required torque levels with lower currents for power switches.

2. The voltage mode control method of claim 1 wherein said first set of parameters comprises:

a set of tabled available torque having a maximum torque; and

a set of tabled mechanical speed having a maximum mechanical speed, whereby both said set of tabled available torque and said set of tabled mechanical speed are derived from a set of maximum allowed phase rms currents.

3. The voltage mode control method of claim 1 wherein said second set of parameters comprises:

a requisite torque; and

a sensed speed derived from a rotor of said sinusoidally excited permanent magnet motor.

4. The voltage mode control method of claim 3 further comprising:

determining whether said requisite torque is greater than said maximum torque; and

if said requisite torque is greater than said maximum torque, setting said requisite torque as said maximum torque.

5. The voltage mode control method of claim 1 further comprising computing a requisite phase current.

6. The voltage mode control method of claim 1 wherein:

said reading of said second set of parameters comprises;

reading a speed value; and

reading a requisite torque value.

7. The voltage mode control method of claim 1 wherein said first derived angle is computed by:

$\mathrm{\alpha <br><br>}=\cos -1<br><br>\left[\frac{T_{\mathrm{cmd}}}{3<br><br>N_p<br><br>K_e<br><br>I_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h,\text{\hspace{1em}<br><br>}<br><br>r<br><br>\text{\hspace{1em}<br><br>}<br><br>m<br><br>\text{\hspace{1em}<br><br>}<br><br>s}}\right]$

where,

α

=first derived angle,

N_p denotes the number of pole pairs,

K_e denote back-emf constant of the electric machine, rms value,

E_ph,rms=K_eω

_m,

ω

_m is machine mechanical speed, in rad/s,

E_ph,rms is phase rms back-emf.

8. The voltage mode control method of claim 1 further comprising:

computing a phase rms voltage given by;

$V_{\mathrm{ph},\mathrm{rms}}=\sqrt{E_{\mathrm{ph},\mathrm{rms}}^2+I_{\mathrm{ph},\mathrm{rms}}^2<br><br>\left(R_{\mathrm{ph}}^2+X_{\mathrm{ph}}^2\right)+2<br><br>E_{\mathrm{ph},\mathrm{rms}}<br><br>I_{\mathrm{ph},\mathrm{rms}}<br><br>\left(R_{\mathrm{ph}}<br><br>\cos <br><br>\left(\mathrm{\alpha <br><br>}\right)-X_{\mathrm{ph}}<br><br>\sin <br><br>\left(\mathrm{\alpha <br><br>}\right)\right)}.$

9. The voltage mode control method of claim 1 wherein:

said second derived angle is computed by;

where, $\mathrm{\delta <br><br>}={\sin }^{-1}<br><br>\left[\frac{I_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h,\text{\hspace{1em}<br><br>}<br><br>r<br><br>\text{\hspace{1em}<br><br>}<br><br>m<br><br>\text{\hspace{1em}<br><br>}<br><br>s}<br><br>R_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h}<br><br>\sin <br><br>\left(\mathrm{\alpha <br><br>}\right)+I_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h,r<br><br>\text{\hspace{1em}<br><br>}<br><br>m<br><br>\text{\hspace{1em}<br><br>}<br><br>s}<br><br>X_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h}<br><br>\cos <br><br>\left(\mathrm{\alpha <br><br>}\right)}{V_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h,\text{\hspace{1em}<br><br>}<br><br>r<br><br>\text{\hspace{1em}<br><br>}<br><br>m<br><br>\text{\hspace{1em}<br><br>}<br><br>s}}\right]$$\mathrm{\alpha <br><br>}=\mathrm{first}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{derived}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{angle}$

10. The voltage mode control method of claim 1 wherein said set of derived command voltages comprises:

V_a V_b and V_c with V_a V_b and V_c denoted by;

11. The voltage mode control method of claim 1 wherein said power circuit comprises an inverter.

12. The voltage mode control method of claim 1 wherein said third set of parameters comprises rms phase current, rms voltage, phase impedance, and phase resistance.

13. The voltage mode control method of claim 12 wherein said phase resistance is compensated for temperature variations by a method comprising:

measuring the temperature of the phase windings; and

calculating the actual phase resistance by using the equation;

14. A power steering assist system comprising:

a steering wheel and column;

an electric motor comprising a motor controller, said electric motor adapted to impart rotational force to said steering column;

a power steering controller adapted to control said electric motor in a manner effective in providing power steering assist to an operator of said steering wheel; and

wherein said electric motor controller operates by the method of claim 1.

15. A voltage mode control method for reducing torque ripple in an electric motor, comprising:

providing a sinusoidally excited permanent magnet motor without current sensors;

determining a known maximum allowed value from a first set of parameters with each parameter having said known maximum value;

reading a second set of parameters;

computing a first derived angle using said first set of parameters and said second set of parameters;

computing amplitude and a second derived angle of phase voltage vector using said first derived angle and a third set of parameters; and

outputting a set of derived command voltages for controlling a power circuit whereby the said power circuit can achieve required torque levels with lower currents for power switches.

16. A storage medium encoded with machine-readable computer program code for extending speed range operation from a sinusoidally excited permanent magnet motor, said storage medium including instructions for causing a computer to implement a method comprising:

determining a known maximum allowed value from a first set of parameters with each parameter having said known maximum value;

reading a second set of parameters;

computing a first derived angle using said first set of parameters and said second set of parameters;

computing amplitude and a second derived angle of phase voltage vector using said first derived angle and a third set of parameters; and

outputting a set of derived command voltages for controlling a power circuit whereby the said power circuit can achieve required torque levels with lower currents for power switches.

17. The storage medium of claim 16 wherein said first set of parameters comprises:

a set of tabled available torque having a maximum torque; and

a set of tabled mechanical speed having a maximum mechanical speed, whereby both said set of tabled available torque and said set of tabled available mechanical speed are derived from a set of maximum allowed phase rms currents.

18. The storage medium of claim 16 wherein said second set of parameters comprises:

a requisite torque; and

a sensed speed derived from a rotor of said sinusoidally excited permanent magnet motor.

19. The storage medium of claim 18 further comprising instructions for causing a computer to implement the procedure of:

determining whether said requisite torque is greater than said maximum torque; and

if said requisite torque is greater than said maximum torque, setting said requisite torque as said maximum torque.

20. The storage medium of claim 16 further comprising instructions for causing a computer to implement the procedure of:

computing a requisite phase current.

21. The storage medium of claim 16 wherein said reading of said second set of parameters comprises:

reading a speed value; and

reading a requisite torque value.

22. The storage medium of claim 16 wherein said first derived angle is computed by:

$\mathrm{\alpha <br><br>}=\cos -1<br><br>\left[\frac{T_{\mathrm{cmd}}}{3<br><br>N_p<br><br>K_e<br><br>I_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h,\text{\hspace{1em}<br><br>}<br><br>r<br><br>\text{\hspace{1em}<br><br>}<br><br>m<br><br>\text{\hspace{1em}<br><br>}<br><br>s}}\right]$

where,

α

=first derived angle,

N_p denotes the number of pole pairs,

K_e denote back-emf constant of the electric machine, rms value,

E_ph,rms=K_eω

_m,

ω

_m is machine mechanical speed, in rad/s,

E_ph,rms is phase rms back-emf.

23. The storage medium of claim 16 further comprising instructions for causing a computer to implement the procedure of:

computing a phase rms voltage given by;

$V_{\mathrm{ph},\mathrm{rms}}=\sqrt{E_{\mathrm{ph},\mathrm{rms}}^2+I_{\mathrm{ph},\mathrm{rms}}^2<br><br>\left(R_{\mathrm{ph}}^2+X_{\mathrm{ph}}^2\right)+2<br><br>E_{\mathrm{ph},\mathrm{rms}}<br><br>I_{\mathrm{ph},\mathrm{rms}}<br><br>\left(R_{\mathrm{ph}}<br><br>\cos <br><br>\left(\mathrm{\alpha <br><br>}\right)-X_{\mathrm{ph}}<br><br>\sin <br><br>\left(\mathrm{\alpha <br><br>}\right)\right)}.$

24. The storage medium of claim 16 wherein said second derived angle is computed by:

$\mathrm{\delta <br><br>}={\sin }^{-1}<br><br>\left[\frac{I_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h,\text{\hspace{1em}<br><br>}<br><br>r<br><br>\text{\hspace{1em}<br><br>}<br><br>m<br><br>\text{\hspace{1em}<br><br>}<br><br>s}<br><br>R_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h}<br><br>\sin <br><br>\left(\mathrm{\alpha <br><br>}\right)+I_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h,r<br><br>\text{\hspace{1em}<br><br>}<br><br>m<br><br>\text{\hspace{1em}<br><br>}<br><br>s}<br><br>X_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h}<br><br>\cos <br><br>\left(\mathrm{\alpha <br><br>}\right)}{V_{p<br><br>\text{\hspace{1em}<br><br>}<br><br>h,\text{\hspace{1em}<br><br>}<br><br>r<br><br>\text{\hspace{1em}<br><br>}<br><br>m<br><br>\text{\hspace{1em}<br><br>}<br><br>s}}\right]$

where,

α

=first derived angle.

25. The storage medium of claim 16 wherein said set of derived command voltages comprising:

V_a V_b and V_c with V_a V_b and V_c denoted by;

26. The storage medium of claim 16 wherein said power circuit comprises an inverter.

27. The storage medium of claim 16 wherein said third set of parameters comprises rms phase current, rms voltage, phase impedance, and phase resistance.

28. The storage medium of claim 27 wherein said phase resistance is compensated for temperature variations by a method comprising:

measuring the temperature of the phase windings; and

calculating the actual phase resistance by using the equation;

29. A power steering assist system comprising:

a steering wheel and column;

an electric motor comprising a motor controller having a storage medium, said electric motor adapted to impart rotational force to said steering column;

a power steering controller adapted to control said electric motor in a manner effective in providing power steering assist to an operator of said steering wheel; and

wherein said storage medium operates said electric motor controller by the method of claim 16.

30. A method of reducing torque ripple in an electric motor, comprising:

providing a sinusoidally excited permanent magnet electric motor without current sensors;

providing a controller for controller said electric motor;

said controller having a storage medium encoded with machine-readable computer program code, said code comprising instructions for causing a computer to implement a procedure comprising;

determining a known maximum allowed value from a first set of parameters with each parameter having said known maximum value;

reading a second set of parameters;

computing a first derived angle using said first set of parameters and said second set of parameters;

computing amplitude and a second derived angle of phase voltage vector using said first derived angle and a third set of parameters; and

outputting a set of derived command voltages for controlling a power circuit whereby the said power circuit can achieve required torque levels with lower currents for power switches.