Disturbance and nonlinear Luenberger observers for estimating mechanical variables in permanent magnet synchronous motors under mechanical parameters uncertainties

This paper deals with rotor position and speed estimation of permanent-magnet synchronous motors. Two reduced-order observers, a disturbance observer and a nonlinear one, are considered. It is shown that under exact model assumption the nonlinear observer converges in an exponential way, while a residual estimation error appears when the disturbance observer is used. Therefore, uncertainties in the mechanical submodel are taken into account. Estimation error arises due to the model mismatch; bounds for this error are calculated in both observers. Finally, a comparison of the performance of each observer is presented.