Apparatus and method of determining rotor position in a salient-type motor
View Patent ↗An example apparatus includes a controller configured to control operation of a salient-type, multiphase motor in accordance with a technique including periodic on and off-times, the motor including a stator and a rotor. The controller is configured to calculate or receive values representing changes in current to the motor during the respective on and off-times or measurements proportional thereto, and calculate an inductance of the motor as a function of the values and a supply voltage to the motor. And the controller is configured to determine a position of the rotor based on the inductance of the motor, and control operation of the motor based on the position of the rotor.
1. An apparatus comprising:
a controller configured to control operation of a salient-type, multiphase motor in accordance with a technique including periodic on and off-times, the motor including a stator and a rotor,
wherein the controller is configured to receive, as values, measurements proportional to changes in current to the motor during the respective on and off-times, the measurements being of voltages from a differentiator circuit, and calculate an inductance of the motor as a function of the values and a supply voltage to the motor, and
wherein the controller is configured to determine a position of the rotor based on the inductance of the motor, and control the operation of the motor based on the position of the rotor.
2. The apparatus of claim 1 , wherein the controller is configured to selectively determine the position of the rotor based on the inductance of the motor, or a back electromotive force generated in the motor, based on a speed of the motor.
3. The apparatus of claim 1 , wherein the stator includes a plurality of windings for a plurality of phases of the motor,
wherein the controller is configured to control operation of the motor according to a commutation sequence including a plurality of steps each of which include periodic on and off-times, and during each of which the windings of a pair of the phases of the motor are energized, and
wherein during at least one step of the commutation sequence, the values represent changes in current through the windings of a respective pair of phases during the respective on and off-times or measurements proportional thereto.
4. The apparatus of claim 1 , wherein the controller is configured to control operation of the motor in accordance with a pulse width modulation (PWM) technique including periodic PWM high and low-times corresponding to the periodic on and off-times, and
wherein the controller is configured to calculate the values representing changes in current during the respective PWM high and low-times.
5. The apparatus of claim 4 , wherein the controller is configured to control operation of the motor in accordance with the PWM technique including the controller being configured to receive measurements of current to the motor during the respective PWM high and low-times,
wherein the controller is further configured to receive second measurements of current to the motor during the respective PWM high and low-times, and calculate the changes in current to the motor during the respective PWM high and low-times as function of the measurements and second measurements.
6. The apparatus of claim 1 , wherein the controller is configured to calculate the inductance L of the motor according to the following:
L
=
2
V
DC
(
ⅆ
i
ⅆ
t
+
ⅆ
i
1
ⅆ
t
1
)
in which
ⅆ
i
ⅆ
t
and
ⅆ
i
1
ⅆ
t
1
represent the changes in current during the respective on and off-times, and V DC represents the supply voltage to the motor.
7. The apparatus of claim 1 , wherein the controller is configured to receive a sample from the differentiator for each high-time and low-time, the sample being one of the received values.
8. A method comprising:
controlling operation of a salient-type, multiphase motor in accordance with a technique including periodic on and off-times, the motor including a stator and a rotor;
receiving, as values, measurements proportional to changes in current to the motor during the respective on and off-times, the measurements being of voltages from a differentiator circuit, and calculating an inductance of the motor as a function of the values and a supply voltage to the motor; and
determining a position of the rotor based on the inductance of the motor, and controlling the operation of the motor based on the position of the rotor.
9. The method of claim 8 , wherein determining the position of the rotor comprises selectively determining the position of the rotor based on the inductance of the motor, or a back electromotive force generated in the motor, based on a speed of the motor.
10. The method of claim 8 , wherein the stator includes a plurality of windings for a plurality of phases of the motor,
wherein operation of the motor is controlled according to a commutation sequence including a plurality of steps each of which include periodic on and off-times, and during each of which the windings of a pair of the phases of the motor are energized, and
wherein during at least one step of the commutation sequence, the values represent changes in current through the windings of a respective pair of phases during the respective on and off-times or measurements proportional thereto.
11. The method of claim 8 , wherein operation of the motor is controlled in accordance with a pulse width modulation (PWM) technique including periodic PWM high and low-times corresponding to the periodic on and off-times, and
wherein calculating or receiving values comprises calculating the values representing changes in current during the respective PWM high and low-times.
12. The method of claim 11 , wherein operation of the motor is controlled in accordance with the PWM technique including receiving measurements of current to the motor during the respective PWM high and low-times,
wherein the method further comprises receiving second measurements of current to the motor during the respective PWM high and low-times, and
wherein calculating the values comprises calculating the changes in current to the motor during the respective PWM high and low-times as function of the measurements and second measurements.
13. The method of claim 8 , wherein calculating the inductance comprises calculating the inductance L of the motor according to the following:
L
=
2
V
DC
(
ⅆ
i
ⅆ
t
+
ⅆ
i
1
ⅆ
t
1
)
in which
ⅆ
i
ⅆ
t
and
ⅆ
i
1
ⅆ
t
1
represent the changes in current during the respective on and off-times, and V DC represents the supply voltage to the motor.
14. The method of claim 8 , further comprises receiving a sample from the differentiator for each high-time and low-time, the sample being one of the received values.
15. A computer-readable storage medium for controlling operation of a salient-type, multiphase motor in accordance with a technique including periodic on and off-times, the motor including a stator and a rotor, the computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program portions comprising:
a first executable portion configured to calculate or receive, as values, measurements proportional to changes in current to the motor during the respective on and off-times, the measurements being of voltages from a differentiator circuit, and calculate an inductance of the motor as a function of the values and a supply voltage to the motor; and
a second executable portion configured to determine a position of the rotor based on the inductance of the motor to thereby permit controlling operation of the motor based on the position of the rotor.
16. The computer-readable storage medium of claim 15 , wherein the second executable portion is configured to selectively determine the position of the rotor based on the inductance of the motor, or a back electromotive force generated in the motor, based on a speed of the motor.
17. The computer-readable storage medium of claim 15 , wherein the stator includes a plurality of windings for a plurality of phases of the motor,
wherein operation of the motor is controlled according to a commutation sequence including a plurality of steps each of which include periodic on and off-times, and during each of which the windings of a pair of the phases of the motor are energized, and
wherein during at least one step of the commutation sequence, the values represent changes in current through the windings of a respective pair of phases during the respective on and off-times or measurements proportional thereto.
18. The computer-readable storage medium of claim 15 , wherein operation of the motor is controlled in accordance with a pulse width modulation (PWM) technique including periodic PWM high and low-times corresponding to the periodic on and off-times, and wherein the first executable portion is configured to calculate the values representing changes in current during the respective PWM high and low-times.
19. The computer-readable storage medium of claim 18 , wherein operation of the motor is controlled in accordance with the PWM technique including receiving measurements of current to the motor during the respective PWM high and low-times,
wherein the computer-readable program portions further comprise a third executable portion configured to receive the measurements and second measurements of current to the motor during the respective PWM high and low-times, and
wherein the first executable portion is configured to calculate the values comprises calculating the changes in current to the motor during the respective PWM high and low-times as function of the measurements and second measurements.
20. The computer-readable storage medium of claim 15 , wherein the first executable portion is configured to calculate the inductance comprises calculating the inductance L of the motor according to the following:
L
=
2
V
DC
(
ⅆ
i
ⅆ
t
+
ⅆ
i
1
ⅆ
t
1
)
in which
ⅆ
i
ⅆ
t
and
ⅆ
i
1
ⅆ
t
1
represent the changes in current during the respective on and off-times, and V DC represents the supply voltage to the motor.
21. The computer-readable storage medium of claim 15 , wherein the first executable portion is configured to receive a sample from the differentiator for each high-time and low-time, the sample being one of the received values.