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 (PMSMs). 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 exponential way, while a residual estimation error appears when a disturbance observer is used. Therefore, uncertainties in the mechanical submodel are taken into account. Estimation error arises due to the mismatch model; bounds for this error are calculated in both observers. Finally, a comparison of the observers performances is presented.