Observer-Based Speed Tracking Control for Sensorless Permanent Magnet Synchronous Motors With Unknown Load Torque

The tracking control problem is addressed for sensorless (nonsalient-pole surface) permanent magnet synchronous motors with unknown constant load torque. Assuming that only stator currents and voltages are available for feedback, a novel sixth order nonlinear adaptive control algorithm is designed, which does not rely on nonrobust open loop integration of motor dynamics and guarantees, under persistency of excitation, local exponential rotor speed tracking.