Low ripple torque control of a permanent magnet motor without using current sensors

• US 6,498,449 B1
• Filed: 09/18/2000
• Issued: 12/24/2002
• 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: Chen, Shaotang, Namuduri, Chandra Sekhar
• Primary Examiner(s): Nappi, Robert E.
• Assistant Examiner(s): San Martin, Edgardo
• Application Number:
  US09/663,900
• Time in Patent Office: 827 Days
• Field of Search: 318/434, 318/798-801, 318/805, 318/806, 318/808-812, 318/599
• US Class Current: 318/434
• 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 method and apparatus for controlling the torque of and reducing torque ripple in a permanent magnet motor without using current sensors. By eliminating the need for current sensors, low frequency torque ripple is reduced. A voltage mode control method is implemented to control the motor. In response to the position and speed of the rotor and a torque command signal, a controller develops motor voltage command signals indicative of the voltage required to produce the desired motor torque. A rotor position encoder determines the angular positions of the rotor. From the angular positions of the rotor, a speed measuring circuit determines the speed of the rotor. The position and speed signals are applied to the controller. The controller uses this information and develops the motor voltage command signals indicative of the voltage needed to produce the desired motor torque. An inverter is coupled between a power source and the controller. The circuit applies phase voltages to the motor, in response to the motor voltage command signals, to produce the desired motor torque.

Claims

1. A method of controlling a sinusoidally excited permanent magnet motor having known motor parameters, comprising:

generating a motor angular position signal indicative of an angular position of the motor;

generating a motor speed signal indicative of a speed of the motor;

determining, in response to the known motor parameters, the motor angular position signal, the motor speed signal, a torque command signal, and amplitudes for input motor phase voltages, the torque command signal being indicative of a desired torque on the motor; and

applying the input motor phase voltages at the amplitudes determined to the motor, wherein the desired torque on the motor is produced.

2. An apparatus for controlling a sinusoidally excited permanent magnet motor having known motor parameters, comprising:

a position encoder associated with the motor for sensing an angular position of the motor and providing a motor angular position signal indicative thereof;

a speed measurement circuit associated with the position encoder for measuring a speed of the motor and providing a motor speed signal indicative thereof;

a controller in communication with the position encoder for receiving the motor angular position signal and in communication with the speed measurement circuit for receiving the motor speed signal, the controller providing, in response to the known motor parameters, the motor angular position signal, the motor speed signal, and a torque command signal, voltage command signals, the torque command signal being indicative of a desired torque on the motor; and

an inverter in communication with the controller for receiving the voltage command signals and in communication with a power source, the inverter applying, in response to the voltage command signals, input motor phase voltages to the motor, wherein the desired torque on the motor is produced.

13. The method of claim 2 wherein the determining further comprises determining phases of the input motor phase voltages so that the phases of the input motor phase voltages are in phase with respective back-emfs of the motor.

14. The method of claim 13 wherein the determining phases of the input motor phase voltages utilizes pulse width modulation.

3. An apparatus for controlling a sinusoidally excited permanent magnet motor having known motor parameters, comprising:

a position encoder associated with the motor for sensing an angular position of the motor and providing a motor angular position signal indicative thereof;

a speed measurement circuit associated with the position encoder for measuring a speed of the motor and providing a motor speed signal indicative thereof;

a controller in communication with the position encoder for receiving the motor angular position signal and in communication with the speed measurement circuit for receiving the motor speed signal, the controller providing, in response to the known motor parameters, the motor angular position signal, the motor speed signal, and a torque command signal, voltage command signals, the torque command signal being indicative of a desired torque on the motor; and

an inverter in communication with the controller for receiving the voltage command signals and in communication with a power source, the inverter applying, in response to the voltage command signals, input motor phase voltages to the motor, wherein the desired torque on the motor is produced; and

wherein said controller does not employ current or voltage feedback.

15. The apparatus of claim 3 wherein the voltage command signals control amplitudes of the input motor phase voltages.

16. The apparatus of claim 3 wherein the voltage command signals control phases of the input motor phase voltages so that the phases of the input motor phase voltages are in phase with respective back-emfs of the motor.

17. The apparatus of claim 3 wherein the controller further includes a pulse width modulation circuit for controlling the phases of the input motor phase voltages so that the phases of the input motor phase voltages are in phase with respective back-emfs of the motor.

18. The apparatus of claim 3 wherein the controller comprises a microprocessor.

4. A method of controlling a sinusoidally excited permanent magnet motor having known motor parameters, comprising:

generating a motor angular position signal indicative of an angular position of the motor;

generating a motor speed signal indicative of a speed of the motor;

determining, in response to the known motor parameters, the motor angular position signal, the motor speed signal, a torque command signal, and amplitudes for input motor phase voltages, the torque command signal being indicative of a desired torque on the motor;

applying the input motor phase voltages at the amplitudes determined to the motor, wherein the desired torque on the motor is produced; and

wherein the determining the amplitudes for the input motor phase voltages comprises calculating the amplitudes according to a control equation comprising;

$V=\frac{1}{R<br><br>\text{\hspace{1em}<br><br>}<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\delta <br><br>}+\left(\mathrm{\omega <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>L_s\right)<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\delta <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\frac{R^2+{\left(\mathrm{\omega <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>L_s\right)}^2}{3<br><br>\text{\hspace{1em}<br><br>}<br><br>K_e}<br><br>T_{\mathrm{cmd}}+K_e<br><br>{\mathrm{\omega <br><br>}}_m<br><br>R\right)$

 

where

V=amplitude of the input voltage of the motor;

R=resistance of the motor windings;

X_s=reactance of motor phase winding;

K_e=E/ω

_m which is EMF constant;

ω

_m=speed of the motor;

T_cmd=torque command signal; and

δ

=angle between EMF phasor {right arrow over (E)} and voltage phasor {right arrow over (V)}.

5. A method of controlling a sinusoidally excited permanent magnet motor having known motor parameters, comprising:

generating a motor angular position signal indicative of an angular position of the motor;

generating a motor speed signal indicative of a speed of the motor;

determining, in response to the known motor parameters, the motor angular position signal, the motor speed signal, a torque command signal, and amplitudes for input motor phase voltages, the torque command signal being indicative of a desired torque on the motor;

applying the input motor phase voltages at the amplitudes determined to the motor, wherein the desired torque on the motor is produced; and

wherein the determining the amplitudes for the input motor phase voltages comprises calculating the amplitudes according to a control equation comprising;

6. 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 a method comprising;

generating a motor angular position signal indicative of an angular position of the motor;

generating a motor speed signal indicative of a speed of the motor;

determining, in response to the known motor parameters, the motor angular position signal, the motor speed signal, a torque command signal, and amplitudes for input motor phase voltages, the torque command signal being indicative of a desired torque on the motor;

applying the input motor phase voltages at the amplitudes determined to the motor, wherein the desired torque on the motor is produced; and

wherein said determining does not employ current or voltage feedback.

7. An apparatus for controlling a sinusoidally excited permanent magnet motor having known motor parameters, comprising:

a position encoder associated with the motor for sensing an angular position of the motor and providing a motor angular position signal indicative thereof;

a speed measurement circuit associated with the position encoder for measuring a speed of the motor and providing a motor speed signal indicative thereof;

a controller in communication with the position encoder for receiving the motor angular position signal and in communication with the speed measurement circuit for receiving the motor speed signal, the controller providing, in response to the known motor parameters, the motor angular position signal, the motor speed signal, and a torque command signal, voltage command signals, the torque command signal being indicative of a desired torque on the motor; and

an inverter in communication with the controller for receiving the voltage command signals and in communication with a power source, the inverter applying, in response to the voltage command signals, input motor phase voltages to the motor, wherein the desired torque on the motor is produced; and

wherein the controller calculates the amplitudes according to a control equation comprising;

$V=\frac{1}{R<br><br>\text{\hspace{1em}<br><br>}<br><br>\cos <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\delta <br><br>}+\left(\mathrm{\omega <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>L_s\right)<br><br>\sin <br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\delta <br><br>}}<br><br>\text{\hspace{1em}<br><br>}<br><br>\left(\frac{R^2+{\left(\mathrm{\omega <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>L_s\right)}^2}{3<br><br>K_e}<br><br>T_{\mathrm{cmd}}+K_e<br><br>{\mathrm{\omega <br><br>}}_m<br><br>R\right)$

 

where

V=amplitude of the input voltage of the motor;

R=resistance of the motor windings;

X_s=reactance of motor phase winding;

K_e=E/ω

_m which is EMF constant;

ω

_m=speed of the motor;

T_cmd=torque command signal; and

δ

=angle between EMF phasor {right arrow over (E)} and voltage phasor {right arrow over (V)}.

8. An apparatus for controlling a sinusoidally excited permanent magnet motor having known motor parameters, comprising:

a position encoder associated with the motor for sensing an angular position of the motor and providing a motor angular position signal indicative thereof;

a speed measurement circuit associated with the position encoder for measuring a speed of the motor and providing a motor speed signal indicative thereof;

a controller in communication with the position encoder for receiving the motor angular position signal and in communication with the speed measurement circuit for receiving the motor speed signal, the controller providing, in response to the known motor parameters, the motor angular position signal, the motor speed signal, and a torque command signal, voltage command signals, the torque command signal being indicative of a desired torque on the motor; and

an inverter in communication with the controller for receiving the voltage command signals and in communication with a power source, the inverter applying, in response to the voltage command signals, input motor phase voltages to the motor, wherein the desired torque on the motor is produced; and

wherein the controller calculates the amplitudes according to a control equation comprising;

9. A power steering assist apparatus 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 motor controller further comprises;

a position encoder associated with the motor for sensing an angular position of the motor and providing a motor angular position signal indicative thereof;

a speed measurement circuit associated with the position encoder for measuring a speed of the motor and providing a motor speed signal indicative thereof;

a controller in communication with the position encoder for receiving the motor angular position signal and in communication with the speed measurement circuit for receiving the motor speed signal, the controller providing, in response to the known motor parameters, the motor angular position signal, the motor speed signal, and a torque command signal, voltage command signals, the torque command signal being indicative of a desired torque on the motor and wherein said controller does not employ current or voltage feedback; and

an inverter in communication with the controller for receiving the voltage command signals and in communication with a power source, the inverter applying, in response to the voltage command signals, input motor phase voltages to the motor, wherein the desired torque on the motor is produced.

10. A method for reducing torque ripple in a sinusoidally excited permanent magnet motor, comprising:

generating a motor angular position signal indicative of an angular position of the motor;

generating a motor speed signal indicative of a speed of the motor;

determining, in response to the known motor parameters, the motor angular position signal, the motor speed signal, and a torque command signal, amplitudes for input motor phase voltages, the torque command signal being indicative of a desired torque on the motor;

applying the input motor phase voltages at the amplitudes determined to the motor, wherein the desired torque on the motor is produced; and

wherein said determining does not employ current or voltage feedback.

11. An apparatus for reducing torque ripple in a sinusoidally excited permanent magnet motor having known motor parameters, comprising:

a position encoder associated with the motor for sensing an angular position of the motor and providing a motor angular position signal indicative thereof;

a speed measurement circuit associated with the position encoder for measuring a speed of the motor and providing a motor speed signal indicative thereof;

a controller in communication with the position encoder for receiving the motor angular position signal and in communication with the speed measurement circuit for receiving the motor speed signal, the controller providing, in response to the known motor parameters, the motor angular position signal, the motor speed signal, and a torque command signal, voltage command signals, the torque command signal being indicative of a desired torque on the motor, and wherein said controller does not employ current or voltage feedback; and

an inverter in communication with the controller for receiving the voltage command signals and in communication with a power source, the inverter applying, in response to the voltage command signals, input motor phase voltages to the motor, wherein the desired torque on the motor is produced.

12. A method of controlling a sinusoidally excited permanent magnet motor having known motor parameters, comprising:

generating a motor angular position signal indicative of an angular position of the motor;

generating a motor speed signal indicative of a speed of the motor;

determining, in response to the known motor parameters, the motor angular position signal, the motor speed signal, a torque command signal, and amplitudes for input motor phase voltages, the torque command signal being indicative of a desired torque on the motor;

applying the input motor phase voltages at the amplitudes determined to the motor, wherein the desired torque on the motor is produced; and

wherein said determining does not employ current or voltage feedback.