State observer for the permanent-magnet synchronous motor

Controller for a permanent magnet synchronous motor having a single harmonic of air gap flux driven by known motor phase voltages, comprising:

• apparatus adapted to measure motor phase currents;
• computing apparatus adapted to compute estimates of electrical and mechanical states of the motor from observer model equations, said electrical states being parameters relating to the motor phase currents and said mechanical states being parameters relating to rotor speed and position, said observer model equations being derived from state equations of motor dynamics transformed into the rotor frame of reference, the computation being performed in response to the motor phase voltages and a parameter relating to the difference between measurements of the motor phase currents and estimates of the motor phase currents obtained from the estimates of the electrical states of the motor, and
• means responsive to said estimates of the electrical and mechanical states of the motor for controlling the phase voltages of the motor.