Comparative Study of an Adaptive Sliding Observer and an EKF for Speed Sensor-less DTC IPM Synchronous Motor Drives

The accuracy of the open-loop estimation of the stator flux and speed for direct torque controlled (DTC) IPM synchronous motor drives drops as the mechanical speed reduces. At lower speed, inaccurately estimated stator flux and stator resistance mismatch have significant influence on the steady state and transient performance of the drive system. The robustness against parameter detuning and signal noises can be improved by deploying closed-observers to estimate the stator flux and rotor speed. This paper presents a comparative analysis of two stator flux+speed observers for DTC IPM motor drives: the adaptive sliding observer and the Extended Kalman Filter (EKF). The experimental comparison evaluation of the adaptive sliding observer and the EKF regards steady state and dynamic performance, robustness against parameter uncertainties, stability and computational complexity. Recommendations for observer selection and the effectiveness of the various schemes are concluded.