A robust fuzzy logic based control system, combined with Kaiman filter is proposed to control the speed of sensorless permanent magnet synchronous motor (PMSM) drive system in this paper. A novel speed controller is designed using the concept of fuzzy logic, which ensures robust speed control against parameter variations. Sensorless control of PMSM servo drive is implemented using the Kaiman filter and the non linear model of the motor has been linearized on the basis of field orientation principle. Simulations have been 1 carried out to validate the effectiveness of the proposed controller in enhancing robustness and adequate performance in the face of uncertainties. © 2010 IEEE.