Comparison of linear and nonlinear observers for rotor position and speed estimation in permanent magnet AC drives

This paper deals with position and speed estimation of permanent magnet AC drives. In sensorless drives or for fault detection purposes, rotor positio n and speed (mechanical variables) are estimated using observers based on t he measurements of the stator currents and voltages. Two such observers of reduced order, a linear Luenberger and a nonlinear one, are compared with r espect to their estimation errors. Comparisons are made for perfectly known parameters as well as for the case when there are some uncertainties in th eir knowledge. The analysis and simulations performed on both observers sho w that the nonlinear one has a better performance and is more robust agains t parameter uncertainties, at the expense of a larger computational Load.