Two-degree-of-freedom control of a PMSM drive without mechanical sensor

For high performance application, fast acting current loops using PI controllers are usually employed for PMSM drives. Although this leads to a simple design, it is difficult to achieve good command tracking and load regulation characteristics simultaneously. In this paper, the authors investigate a new approach for both the current loops and the speed loop based on the RST method. In the proposed scheme, a feedback controller and a feedforward compensator have been used to accomplish two-degree-of-freedom of control. To estimate the rotor position, a minimal order observer has been developed in the αβ co-ordinate. By the elimination of the expensive mechanical sensors, they have achieved the mechanical sensorless control of the drive. Simulation and experimental results have verified the effectiveness of both the control and estimation schemes