Apparatus and method for monitoring magnet flux degradation of a permanent magnet motor

A system comprising:

• one or more sensors, configured to measure a motor current measurement, a motor reference voltage or measured voltage, and an estimated temperature from an electric motor;
• a flux observer module comprising one or more processors configured by programming instructions encoded on non-transient computer readable media, the flux observer module configured to:
• determine a reference flux linkage estimate (λpm,ref) from a lookup table based on the motor current measurement and the estimated temperature;
• determine a back-EMF (electromotive force) estimate based on the motor current measurement, the motor voltage and the estimated temperature;
• and
• determine an observed flux linkage estimate (λpm,obs) from the back-EMF estimate;
• and
• a magnet strength module comprising one or more processors configured by programming instructions encoded on non-transient computer readable media, the magnet strength module configured to:
• determine a magnetic strength as a ratio of the observed flux linkage estimate to the reference flux linkage estimate;
• and
• cause a diagnostic trouble code to be set indicating that a rotor magnet in the electric motor is not performing to operational standards when the magnetic strength is below a threshold level.

A vehicle, comprising:

• an electric permanent magnet motor;
• one or more sensors, configured to measure a motor current measurement, a motor reference voltage or measured voltage, and an estimated temperature from the electric motor;
• and
• a controller comprising one or more processors and non-transient computer readable media encoded with programming instructions, the controller configured to:
• determine a reference flux linkage estimate (λpm,ref) from a lookup table based on the motor current measurement and the estimated temperature;
• determine a back-EMF (electromotive force) estimate based on the motor current measurement, the motor voltage and the estimated temperature;
• determine an observed flux linkage estimate (λpm,obs) from the back-EMF estimate;
• determine a magnetic strength as a ratio of the observed flux linkage estimate to the reference flux linkage estimate;
• set a diagnostic trouble code in the vehicle indicating that a rotor magnet in the electric motor is not performing to operational standards when the magnetic strength is below a threshold level.