SALIENCY TRACKING FOR BRUSHLESS DC MOTORS AND OTHER PERMANENT MAGNET SYNCHRONOUS MOTORS
Saliency tracking for brushless direct current (BLDC) motors and other permanent magnet synchronous motors (PMSMs) is provided. An example method for estimating rotor position of a synchronous machine includes measuring a current relating to a synchronous machine. The example method also includes determining an error signal from the current measured. The example method further includes estimating a rotor position of the synchronous machine with a phase-locked loop (PLL) based at least in part on the error signal.
1 . A method for estimating rotor position of a synchronous machine, the method comprising:
measuring a current relating to a synchronous machine;
determining an error signal from the current measured; and
estimating a rotor position of the synchronous machine with a phase-locked loop (PLL) based at least in part on the error signal.
2 . The method of claim 1 , wherein the current is measured in response to a voltage being injected into the synchronous machine.
3 . The method of claim 2 , further comprising injecting the voltage into the synchronous machine.
4 . The method of claim 2 , wherein the voltage injected is a variable frequency pulsating voltage that can be increased in frequency during motor operation to reduce acoustic noise and increase system bandwidth.
5 . The method of claim 1 , wherein a rotor speed of the synchronous machine is determined based on the rotor position.
6 . The method of claim 1 , wherein the phase-locked loop is a proportional-integral (PI) type phase-locked loop.
7 . The method of claim 1 , further comprising measuring motor phase inductance based at least in part on the current.
8 . The method of claim 1 , further comprising injecting one or more currents to maintain a saliency signal.
9 . The method of claim 8 , wherein the one or more currents injected are introduced as a magnetization current as a percentage of a torque current.
10 . The method of claim 1 , further comprising: extracting harmonic information from the measured current; and identifying a polarity of the error signal based on the extracted harmonic information, wherein the estimated rotor position is further based on the polarity of the error signal.
11 . A rotor position estimator for a synchronous machine comprising:
a detector configured to measure a current, wherein an error signal is determined from the current measured; and
a phase-locked loop (PLL) configured to estimate a rotor position of the synchronous machine based at least in part on the error signal.
12 . The rotor position estimator of claim 11 , wherein the detector comprises an error compensation factor designed to compensate for a saliency ratio of the measured current.
13 . The rotor position estimator of claim 12 , wherein the error compensation factor is designed to be negated in order to obtain a 90° offset of the estimated rotor position from PLL to track either a direct axis or a quadrature axis.
14 . The rotor position estimator of claim 11 , wherein the current is measured in response to a voltage being injected into the synchronous machine.
15 . The rotor position estimator of claim 11 , further comprising a voltage generator configured to inject a voltage into the synchronous machine, wherein the current is measured during injection of the voltage by the voltage generator.
16 . The rotor position estimator of claim 15 , wherein the voltage injected is a variable frequency pulsating voltage that can be increased in frequency during motor operation to reduce acoustic noise and increase system bandwidth.
17 . The rotor position estimator of claim 11 , further comprising a saliency amplification system to maintain a saliency signal by injecting one or more currents.
18 . The rotor position estimator of claim 17 , wherein the one or more currents injected are introduced as a magnetization current as a percentage of a torque current.
19 . The rotor position estimator of claim 11 , wherein the phase-locked loop is a proportional-integral (PI) type phase-locked loop.
20 . The rotor position estimator of claim 11 , wherein the detector is further configured to measure motor phase inductance based at least in part on the current.