Speed and position estimation for PM synchronous motor using self-compensated back-EMF observers

The paper deals with the self-compensation of the intrinsic estimation error in back-EMF based rotor position observers for PM synchronous motors. The self-compensation is based on the analytical calculation of the rotor position estimation error for two types of popular back-EMF observers, such as the standard-linear Luenberger Observer and the nonlinear Sliding Mode Observer. Once the compensation characteristics are derived, they are included in the observer itself by a proper mechanism in order to cancel the position error affecting the estimation, thus providing the real-time self-compensation scheme. As a consequence, the performance and the robustness of the transducer-less drive can be improved, both at steady state and transient operations. Test results are presented to verify the effectiveness of the method in several operating conditions: both simulation results using a time-continuous Matlab/ Simulink model, and experimental results using a DSP based transducer-less drive.