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

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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.