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A Fuzzy Logic Concept Design or Improving the Angular Resolution of Permanent Magnet Stepper Machine

Ecole Nationale d’Ingénieurs de Tunis, Department of Electrical Engineering
BP. 37, le Belvédère, 1002 Tunis-Tunisia

Abstract: In this paper, is presented a fuzzy logic strategy in order to improve the angular resolution of the permanent magnet (PM) stepper actuator. Then, is described and discussed, in the first part, the conventional open loop microstepping technique which is realised by a Pulse Width Modulation. In the second part, a design of a new approach structured around the fuzzy logic controller is proposed. This control approach needs only the rotor position, which can be easily measured, to compute the control law. Finally, obtained simulation results are presented and discussed. These results confirm the efficiency of the proposed controller for the considerable improvement of the static and dynamic performances.

Keywords: Fuzzy logic controller, Microstepping, Permanent magnet stepper motor, Incremental torque, positioning error.

El Manâa Barhoumi received the Master degree in Electrical Engineering from the Ecole Nationale d’Ingénieurs de Tunis-Tunisia in 2008. He is a member of Laboratory of Electrical Systems (LSE) ENIT, Tunis- Tunisia.

Kais Mhatli received the Dipl.-Ing. and the M.Sc. degrees in Electrical Engineering from Ecole Nationale d’Ingénieurs de Tunis (ENIT), Tunisia, in 2000 and 2004 respectively. In September 2005, he joined the Institut Supérieur des Etudes technologiques de Radès (ISET Radès), Tunisia, as associate professor. He works now in the Ph.D. degree in the field of power systems design and control.

Boujemâa Ben Salah received the Master degree in Electrical Engineering from Ecole Normale Superieure de l’Enseignement Technique de Tunis (ENSET) in 1986. Also, He received the Doctorat and Habilitation Universitaire (HDR) from ENIT in 1997 and 2003 respectively. From 1988 to 1997 he was employed at the ENIT as an Assistant. From 1997 to 2003, he has been Associate Professor in the same school. From 2003 up to now, he is a full professor in electrical engineering at ENIT Univ. Tunis. From 2000 he is currently a visiting professor in the Ecole Centrale de Lille-FRANCE. His main research interests are actuators design and control, power control, speed AC drives.

>>Full text
El Manâa BARHOUMI, Kais MHATLI, Boujemâa BEN SALAH, A Fuzzy Logic Concept Design or Improving the Angular Resolution of Permanent Magnet Stepper Machine, Studies in Informatics and Control, ISSN 1220-1766, vol. 17 (3), pp. 285-296, 2014.

1. Introduction

The essential property of a stepper motor is the translation of the switching excitation changes into precisely defined rotor increments. Because of its precise open loop functioning, the PM stepper motor is used in many applications, ranging from simple applications to high end space applications such as positioning mechanisms for telescopes.

However, some oscillations and a long settling time of the position evolution are the main disadvantage of the PM stepper motor. Moreover, the oscillations can induce the PM stepper motor at some control frequencies to an erratic working. Also, the angular resolution of the PM stepper motor is small, but many applications require accurate positioning and a fine resolution.

In order to solve these problems, we propose in this paper a new closed loop control strategy based on the use of a fuzzy logic concept, which improve the angular resolution.

Fuzzy logic control (FLC) is mainly applied to complex plants where it is difficult to obtain accurate mathematical model or when the model is severely non linear. FLC has the ability to handle numeric and linguistic knowledge simultaneously. FLC gives good performances when it is applied to electrical machines.

This paper is organized as follow. The description and mathematical model of the PM stepper motor are presented in section 3. Section 4 is consecrated to the full step working. Section 5 and 6 are reserved to microstepping obtained by conventionally technique. The new proposed closed loop fuzzy logic concept is developed in section 7. The validation and the commentary of this approach are also explained in this section. Finally, section 8 presents our conclusion.

6. Conclusion

In this paper, a closed loop Fuzzy Logic Controller and a modelling approach are proposed for a permanent magnet stepper actuator. This strategy have the advantage to convert a conventional permanent magnet stepping machine with a fixed step-size into one with a programmable step angle, thereby improving motor positioning resolution by a high factor.

Also, this control approach attenuates, in a very much reduced settling time, the oscillations and eliminates the problems of overshoot and resonance. Hence, this method contributes to the improvement of the dynamic stability of a PM stepper machine functioning in lower speed.


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