Challenges and Limits of Extended Kalman Filter based Sensorless Control of Permanent Magnet Synchronous Machine Drives Zdeněk Peroutka 1 , Václav Šmídl 2 and David Vošmik 1 1 UNIVERSITY OF WEST BOHEMIA IN PILSEN Univerzitní 8, 306 14 Plzeň, Czech Republic Tel.: +420 / 37763-4443 (-4446). Fax: +420 / 37763 4402. E-Mail: peroutka@ieee.org , vosmik1@kev.zcu.cz URL: http://www.fel.zcu.cz 2 INSTITUTE OF INFORMATION THEORY AND AUTOMATION ACADEMY OF SCIENCE OF THE CZECH REPUBLIC Pod vodárenskou věží 4, 182 08 Prague, Czech Republic Tel.: +420 / 266 052 420. Fax: +420 / 266 052 068. E-Mail: smidl@utia.cas.cz URL: http://www.utia.cz Acknowledgements This research has been supported by the Czech Science Foundation under project GAČR 102/08/P250. Keywords Control of Drive, Estimation technique, Intelligent drive, Permanent magnet motor, Sensorless control. Abstract A sophisticated simulator of permanent magnet synchronous machine (PMSM) drive was developed and is used for research into model-based sensorless control strategies. In this paper, we focus on estimators based on the extended Kalman Filter (EKF). The limits and possible improvements of the EKF are investigated using the developed simulator and real data recorded on designed laboratory prototypes of PMSM drives. From the viewpoint of possible improvement of the estimator, the main attention has been paid to the following phenomena: (i) uncertainty of a stator voltage vector (effects of dead-times, non-linear voltage drops on power devices, etc.), (ii) impact of imperfect model discretization, and (iii) impact of unknown load torque. These phenomena are analyzed and the results are used to tune covariance matrices of the EKF via a semi-analytical approach. Theoretical results are verified by experiments made on two developed prototypes of PMSM drive of rated power of 10.7kW and 310W. Finally, this paper summarizes the major limits of EKF and proposes prospective ways for further research leading to reduction of these limits. Introduction This research was motivated by demand of our industrial partners for proposal of a prospective sensorless control strategy for permanent magnet synchronous machine (PMSM) drives operated in modern transport systems. The sensorless control of PMSM drives is well established and discussed in the literature. Several interesting papers and books covering this issue were published, e.g. [1]. However, this problem is still open for further research. Specifically, sensorless operation of the drive in standstill and in low speeds is not satisfactorily resolved. We have focused in the first part of our research on model-based sensorless techniques. One of our important tasks was to design a model of