Fault Tolerant Control of PMSM Drive Using Luenberger and Adaptive Back-EMF Observers Slimane Medjmadj Laboratory of Control of Setif (LAS) and university Bordj Bou Arréridj, Algeria Corresponding Author Email: s.medjmadj@univ-bba.dz https://doi.org/10.18280/ejee.210311 Received: 11 March 2019 Accepted: 20 May 2019 ABSTRACT In this paper, we propose to design a sensorless controller that can cope both with performance and robustness by the hybridization of two controllers. The strategy introduced in this paper includes the sensorless active fault tolerant controller of the PMSM drive at high speed. It is built with the combination of a vector controller, two virtual sensors: Luenberger and adaptive back-EMF observers, and a voting algorithm using Newton-Raphson method. Simulation results are provided to verify effectiveness of the proposed strategy of a 1kW PMSM motor driven by fault tolerant control in case of position sensor outage. Keywords: PMSM, fault tolerant control (FTC), mechanical sensor failure, voting algorithm, sensorless control 1. INTRODUCTION Permanent Magnet Synchronous Motors (PMSMs) are more and more present in numerous industry domains. Although rotor position and velocity can be used to achieve precise control of these motors, position sensors have several problems such as cost and durability. Therefore, many sensorless control methods have been proposed [1-2]. The PMSMs have attracted increasing interest in recent years for industrial drive application. The high efficiency, high power density, high steady state torque density and simple controller of the motor drives compared with the induction motor drives make them a good alternative in certain applications [2]. They have increasingly been used in Electric Vehicles (EVs) or Hybrid Electric Vehicles (HEV), aircraft, nuclear power stations, submarines, robotic applications, medical, industrial and military applications due to several outstanding characteristics. In some of these applications, continuous operation is necessary and thus a breakdown of the PMSM drive is unacceptable [2]. In the past decade, vector control of PMSM has emerged as a mature technology. A rotor shaft attached position sensor (encoder, resolver, Hall-effect sensor, etc.) is needed in order to achieve precise rotor position/speed control. Because of economical and reliability reasons, the elimination of the position sensors is of high interest. PMSM drive research has been concentrated on the elimination of the mechanical sensors at the motor shaft. In sensorless vector control, the position sensor is replaced by a position observer using electric variables measurements. The advantages of sensorless ac drives are the lower cost, reduced size of the motor set, cable elimination, and increased reliability [2]. We find in the literature several methods of PMSM speed or rotor control. They are distinguished by: - The type of the speed control, - The mode of operation (with or without a rotor position sensor), - The operation speed range (low speed or medium to high speed range). Many methods have been presented in the literature for the estimation of the rotor speed and position for the PMSM drive. In general there are three different approaches [3-4]. The first approach focuses on estimation of the motor back electromotive force (EMF) [5-7].The second uses position dependence on motor inductances due to magnetic saliency [8] while the third one is based on the linear or non-linear state observers, such as: Luenberger observer, reduced order observer, Fuzzy logic control, sliding mode observer and Kalman filter, [9-11]. There are numerous study results about fault detection and fault-tolerant control [12-13], but most of them focused on the faults at high speed of the PMSM. In this paper an active position sensor fault tolerant controller (AFTC) is presented at high speed. It is based on the combination of the actual sensor and two virtual ones: Luenberger observer and a back electromotive-force-based observer (EMF Observer). A simple algorithm, which allows the switching from the mechanical sensor output to the outputs of the virtual sensors. The simulation results have verified the effectiveness and viability of the method presented in this paper. This paper is organized as follows; the description of the sensorless algorithms of the PMSM is described in section II. In section III, the algorithm for the fault tolerant control is presented. Section IV presents the simulation results. Finally some concluding remarks end the paper. 2. POSITION AND SPEED OBSERVERS To have a strategy for the fault tolerant control position/speed sensor, we used the method based on analytical redundancy. This method is based on the combination of the actual sensor position and two virtual position/speed sensors: Luenberger and Adaptive Back-EMF observers. 2.1 Luenberger observer In this work the Luenberger observer design is used to estimate speed and position. The stator voltage model in the rotor reference frame for a PMSM is given by [14-15]: European Journal of Electrical Engineering Vol. 21, No. 3, June, 2019, pp. 333-339 Journal homepage: http://iieta.org/journals/ejee 333