Sensorless displacement estimation for an electrostatic film motor using driving currents

Article type: Research Article

Authors: Zhang, Guangwei^a; | Yamamoto, Akio^a

Affiliations: [a] Department of Precision Engineering, University of Tokyo, Tokyo, Japan

Correspondence: [*] Corresponding author: Guangwei Zhang, Department of Precision Engineering, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. Tel.: +81 3 5841 6466; Fax: +81 3 5841 6460; E-mail: guangwei@aml.t.u-tokyo.ac.jp

Abstract: This work proposes a self-sensing method for a synchronous electrostatic film motor. The method utilizes the relation between the driving voltages and currents of the motor. Through several signal conversions on the measured motor currents, the system distills the information of the slider position to realize displacement sensing. The resulting system can track the slider position both for synchronous and non-synchronous operations. The system assumes stepwise motions of the slider and fully exploits the characteristic current features of the motions. Two different signal conversion methods have been tested using numerically simulated motor currents and real motor currents. The two methods differ in terms of accuracy and noise immunity. Considering that the currents of the electrostatic motor are relatively small, the method with high noise immunity and relatively low accuracy was found useful for practical applications. The position resolution achieved by the method was in the order of the electrode pitch, which is 200 μm in the prototype motor used in this work.

Keywords: Electrostatic film motor, displacement estimation, sensorless

DOI: 10.3233/JAE-180068

Journal: International Journal of Applied Electromagnetics and Mechanics, vol. 60, no. 2, pp. 247-261, 2019