Observer-based speed tracking control for sensorless permanent magnet synchronous motors with unknown load torque

We address the tracking control problem for sensorless (nonsalient-pole surface) permanent magnet synchronous motors with unknown constant load torque. On the basis of stator current and voltage measurements only and without relying on nonrobust open loop integration of motor dynamics, a novel sixth order nonlinear adaptive control algorithm is designed, which guarantees, under persistency of excitation, local exponential rotor speed tracking. Simulation results illustrate the closed loop performance and show the effectiveness of the proposed solution even in the presence of current sensor noise and stator resistance variations.