Rotor position sensing system for permanent magnet synchronous motors and related methods
Implementations of a system for sensing rotor position of a PMSM may include: a controller which may be coupled with the PMSM. The controller may be configured to apply a plurality of voltage vectors to the PMSM to generate a plurality of sensing signals from a stator of the PMSM in response. A comparator may be coupled to the PMSM configured to receive and to compare each one of the plurality of sensing signals with a threshold voltage. A rise time measurement circuit may calculate a plurality of rise times using the plurality of sensing signals in response to receiving a signal from the comparator. The rotor-angle estimation circuit may be configured to identify from the plurality of rise times a shortest rise time and a voltage vector corresponding with the shortest rise time and thereby identify the position of the rotor of the PMSM.
1. A system for sensing rotor position of a permanent magnet synchronous motor, comprising:
a controller configured to couple with a permanent magnet synchronous motor (PMSM), wherein the controller is configured to apply a plurality of voltage vectors to the PMSM to generate a plurality of sensing signals from a stator of the PMSM in response;
a rise time measurement circuit configured to couple to the PMSM, wherein the rise time measurement circuit is configured to calculate a plurality of rise times using the plurality of sensing signals;
a memory coupled with the rise time measurement circuit, wherein the memory is configured to store the plurality of rise times;
a rotor-angle estimation circuit coupled with the memory, wherein the rotor-angle estimation circuit is configured to calculate a rotor position relative to the stator of the PMSM using the plurality of rise times; and
a threshold voltage generator coupled to the controller, the threshold voltage generator configured to generate a threshold voltage in response to a command from the controller, wherein the threshold voltage is at least a first threshold voltage and a second threshold voltage.
2. The system of claim 1 , further comprising an amplifier coupled to a resistor, wherein the amplifier is configured to receive and to amplify the plurality of sensing signals to form a plurality of amplified sensing signals.
3. The system of claim 2 , further comprising a comparator coupled to the amplifier and to a threshold voltage generator, wherein the comparator is configured to receive and to compare each one of the plurality of amplified sensing signals with a threshold voltage generated by the threshold voltage generator.
4. The system of claim 2 , wherein the first threshold voltage and the second threshold voltage are calculated using a first threshold voltage equation and a second threshold voltage equation;
wherein the first threshold voltage equation is
V th1 =( G )( R sh )( I th1 )+ V off
and the second threshold voltage equation is
V th2 =( G )( R sh )( I th2 )+ V off
where V th1 is the first threshold voltage, V th2 is the second threshold voltage, G is a gain of the amplifier, R sh is a resistance from the resistor, I th1 is a first threshold current, I th2 is a second threshold current, and V off is the amplifier's offset voltage.
5. The system of claim 4 , wherein the first threshold current and the second threshold current are related by an equation I th1 = 4/3I th2 .
6. The system of claim 1 , wherein the plurality of voltage vectors is one of 12 and 24.
7. The system of claim 1 , further comprising an analog to digital (A/D) converter configured to couple to the PMSM, wherein the A/D converter is configured to convert the plurality of sensing signals into a plurality of digital current signals.
8. The system of claim 7 , wherein the controller is configured to generate a first A/D threshold value and a second A/D threshold value using one of a first A/D threshold value equation and a second A/D threshold value equation;
wherein the first A/D threshold value equation is
AD
th
1
=
V
th
1
(
2
n
Vref
AD
)
and the second A/D threshold value equation is
AD
th
2
=
V
th
2
(
2
n
Vref
AD
)
where AD th1 is the first A/D threshold value, AD th2 is the second A/D threshold value, V th1 is a first threshold voltage, V th2 is a second threshold voltage, n is the A/D resolution, and Vref AD is a full scale voltage value.
9. The system of claim 1 , wherein the rise time measurement circuit measures each rise time using a rise time measurement equation;
wherein the rise time measurement equation is
T
r
=
(
AD
th
-
AD
1
AD
2
-
AD
1
)
(
t
2
-
t
1
)
+
t
1
where T r is the rise time, AD th is one of the first A/D value threshold and the second A/D value threshold, AD 2 is a first value from the A/D converter formed when AD 2 exceeds AD th , AD 1 is a second value from the A/D converter formed prior to AD 1 exceeding AD th , t 2 is a time corresponding with AD 2 , and t 1 is a time corresponding with AD 1 .
10. The system of claim 1 , wherein the controller is configured to generate a first threshold current and a second threshold current, wherein the first threshold current and the second threshold current are related by the equation I th1 = 4/3I th2 where I th1 is the first threshold current and I th2 is the second threshold current.
11. A method for sensing a rotor position of a permanent magnet synchronous motor, the method comprising:
applying a plurality of voltage vectors to a stator of a permanent magnet synchronous motor (PMSM);
generating a plurality of sensing current signals from the stator in response to the plurality of voltage vectors applied to the PMSM;
converting the plurality of sensing current signals into a plurality of sensing voltage signals using a resistor coupled to the stator;
comparing each of the plurality of sensing voltage signals with a threshold voltage generated by a threshold voltage generator using a comparator coupled to the PMSM;
calculating a plurality of rise times using the plurality of sensing voltage signals and a signal from the comparator using a rise time measurement circuit coupled to the comparator;
storing the plurality of rise times in a memory coupled with the rise-time measurement circuit;
determining a rotor position relative to the stator of the PMSM using a rotor-angle estimation circuit by calculating the rotor position relative to the stator using the plurality of rise times; and
generating the threshold voltage using the threshold voltage generator in response to a command from a controller coupled with the threshold voltage generator, wherein the threshold voltage is one of a first threshold voltage and a second threshold voltage.
12. The method of claim 11 , further comprising an amplifier configured to receive and to amplify the plurality of sensing voltage signals to form a plurality of amplified sensing voltage signals and wherein the first threshold voltage and the second threshold voltage are calculated using one of a first threshold voltage equation and a second threshold voltage equation;
wherein the first threshold voltage equation is
V th1 =( G )( R sh )( I th1 )+ V off
and the second threshold voltage equation is
V th2 =( G )( R sh )( I th2 )+V off
where V th1 is the first threshold voltage, V th2 is the second threshold voltage, G is a gain of the amplifier, R sh is a resistance from the resistor, I th1 is a first threshold current, I th2 is a second threshold current, and V off is the amplifier's offset voltage.
13. The method of claim 12 , wherein the first threshold current and the second threshold current are related by an equation I th1 = 4/3I th2 .
14. The method of claim 11 , wherein the plurality of voltage vectors is one of 12 and 24.
15. A method for sensing rotor position of a permanent magnet synchronous motor, the method comprising:
applying a plurality of voltage vectors to a stator of a permanent magnet synchronous motor (PMSM);
generating a plurality of sensing current signals from the stator in response to the plurality of voltage vectors applied to the PMSM;
converting a plurality of sensing current signals into a plurality of digital current signals using an analog to digital (A/D) converter coupled to the PMSM;
generating a threshold current using a controller, the threshold current being at least a first threshold current and a second threshold current;
calculating a plurality of rise times, using a rise-time measurement circuit coupled to the A/D converter and to the controller, based upon the plurality of digital current signals received from the A/D converter and at least the first threshold current and the second threshold current;
storing the plurality of rise times in a memory coupled with the rise-time measurement circuit; and
using a rotor-angle estimation circuit coupled with the memory to determine a rotor position relative to a stator using the plurality of rise times.
16. The method of claim 15 , wherein the first threshold current and the second threshold current are related by an equation I th1 =¾I th2 where I th1 is the first threshold current and I th2 is the second threshold current.
17. The method of claim 15 , further comprising measuring each rise time with the rise time measurement circuit using a rise time measurement equation;
wherein the rise time measurement equation is
T
r
=
(
AD
th
-
AD
1
AD
2
-
AD
1
)
(
t
2
-
t
1
)
+
t
1
where T r is the rise time, AD th is one of a first A/D value threshold and a second A/D value threshold, AD 2 is a first value from the A/D converter formed when AD 2 exceeds AD th , AD 1 is a second value from the A/D converter formed prior to AD 2 exceeding AD th , t 2 is a time corresponding with AD 2 , and t 1 is a time corresponding with AD 1 .
18. The method of claim 15 , wherein the plurality of voltage vectors is one of 12 and 24.