Sensorless speed control of permanent magnet motors driving an unknown load

A sensorless strategy for speed control of permanent motors driving an unknown load torque is presented. The proposed strategy uses an extended non-linear reduced-order observer that includes information about the waveform of the EMF generated by the motor, which is neither sinusoidal nor trapezoidal. In order to improve the drive performance, the unknown disturbance torque is estimated by means of an adaptive law, and is incorporated as feedforward signal into the control loop. It allows the realization of torque control avoiding position sensor and with minimum torque ripple. Simulation results that validate the proposal are shown.