Motor constant calculating method for PM motor, and motor constant calculating device
View Patent ↗A motor constant calculating method for a PM motor according to the present invention includes a voltage applying step of applying an applied voltage including a DC component and a plurality of frequency components to a PM motor, a motor current detecting step of detecting a motor current flowing depending on the applied voltage applied in the voltage applying step, and a motor constant calculating step of calculating a motor constant of the PM motor based on the applied voltage and the motor current.
1. A motor constant calculating method for a PM motor, comprising:
a voltage applying step of applying to a PM motor a voltage command including a DC component and a plurality of frequency components;
a motor current detecting step of detecting a responsive motor current flowing through the PM motor in response to application of the voltage command applied in the voltage applying step;
a motor frequency characteristic determining step of calculating a transfer function between the applied voltage command and the detected responsive motor current and determining a frequency characteristic of the transfer function; and
a motor constant calculating step of calculating a motor constant of the PM motor based on the determined frequency characteristic of the transfer function.
2. The motor constant calculating method for a PM motor according to claim 1 , further comprising repeating the voltage applying step while changing a value of the DC component.
3. The motor constant calculating method for a PM motor according to claim 1 , wherein the plurality of frequency components of the voltage command is a white noise.
4. The motor constant calculating method for a PM motor according to claim 1 , wherein the plurality of frequency components of the voltage command is an M-sequence signal.
5. The motor constant calculating method for a PM motor according to claim 1 , wherein the plurality of frequency components of the voltage command is a sinusoidal wave whose frequency changes with time.
6. The motor constant calculating method for a PM motor according to claim 1 , wherein the motor constant calculating step comprises calculating the transfer function, in which the voltage command is taken as a temporal series of inputs, and the detected responsive motor current is taken as a temporal series of outputs.
7. The motor constant calculating method for a PM motor according to claim 1 , wherein the motor constant of the PM motor calculated in the motor constant calculating step comprises at least one of an electric time constant, a resistance, and an inductance of the PM motor.
8. The motor constant calculating method for a PM motor according to claim 7 , wherein the motor constant calculating step comprises determining a cut-off frequency of the frequency characteristic of the transfer function, and determining the electric time constant of the PM motor from the determined cut-off frequency.
9. The motor constant calculating method for a PM motor according to claim 7 , wherein the motor constant calculating step comprises determining a cut-off frequency based on a frequency characteristic of a gain derived from the transfer function, and determining the resistance of the PM motor based on the frequency characteristic of the gain derived from the transfer function in a frequency band lower than the cut-off frequency.
10. The motor constant calculating method for a PM motor according to claim 7 , wherein the motor constant calculating step comprises determining a cut-off frequency based on a frequency characteristic of a gain derived from the transfer function, and determining the resistance of the PM motor based on the frequency characteristic of the gain derived from the transfer function at the cut-off frequency.
11. The motor constant calculating method for a PM motor according to claim 7 , wherein the motor constant calculating step comprises determining a cut-off frequency based on a frequency characteristic of a gain derived from the transfer function, determining the electric time constant of the PM motor based on the cut-off frequency, determining the resistance of the PM motor based on the frequency characteristic of the gain derived from the transfer function in a frequency band lower than the cut-off frequency or the frequency characteristic of the gain derived from the transfer function at the cut-off frequency, and calculating the inductance of the PM motor based on the determined electric time constant and the determined resistance.
12. A motor constant calculating device for a PM motor, comprising:
a voltage command generating unit configured to generate a voltage command to be applied to a PM motor, wherein the voltage command comprises a DC component and a plurality of frequency components;
a current detecting unit configured to detect a responsive motor current flowing through the PM motor in response to application of the voltage command; and
a motor constant calculating unit configured to:
calculate a transfer function between the applied voltage command and the detected responsive motor current;
determine a frequency characteristic of the transfer function; and
calculate a motor constant of the PM motor based on the determined frequency characteristic of the transfer function.
13. The motor constant calculating method for a PM motor according to claim 2 , wherein the plurality of frequency components of the voltage command is a white noise.
14. The motor constant calculating method for a PM motor according to claim 2 , wherein the plurality of frequency components of the voltage command is an M-sequence signal.