Multilayer Thin Electrostatic Actuator Supported by Lubricating Oil

Electrostatic actuators have advantages in terms of their simple structures, low heat production, the large number of available materials, etc. Multilayer structures enable the actuators to produce a large thrust force. However the multilayer structure requires good lubricating characteristics between the mover and stator layers. The characteristics greatly influence the driving performance. For the good lubricating characteristics, ball bearings are generally used. However, ball bearings require complex fabrication processes for the guide structure and numerous micro balls between them.

The purpose of the present research is to realize an easy-to-maintain multilayer thin electrostatic actuator having a simple structure for high-precision motion. For that purpose, lubricating oil is used to support the mover, which is constructed of thin electrodes, but not the ball bearings. The experimental results using prototype multilayer thin electrostatic actuators show that the motion characteristics depend on the driving signal and frictional condition is changed by the driving signal. Suitable driving signals provide the function to adjust the frictional effect for fine motion with a large holding force and a wide and fast motion. The control system including a PID compensator and a driving signal unit that generated two effective driving signals were designed and their effects were experimentally examined. The actuator exhibits a positioning error of less than 14 nm with a continuous holding force of 0.205 N.

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Fig.1. Electrostatic actuator supported by lubricating liquid

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Fig.2. Motion of the electrostatic actuator using suitable driving signals

Key papers

[1]
Kaiji Sato and Tsubasa Yagi : Long Stroke Electrostatic Linear Motor Supported by Only Lubricating Liquid, Proceedings of the 6th International Conference on Positioning Technology (ICPT2014), (Kitakyushyu, Japan), (2014.11) pp.201-203.
[2]
Mariam Md Ghazaly, Kaiji Sato: Characteristic switching of a multilayer thin electrostatic actuator by a driving signal for an ultra-precision motion stage, Precision Engineering, Vol.37, No.1, (2013) pp.107-116.
[3]
Mariam Md Ghazaly, Kaiji Sato: Basic Characteristics of a Multilayer Thin Electrostatic Actuator Supported by Lubricating Oil for a Fine-motion Stage, Precision Engineering, Vol.36, No.1, (2012) pp.77-83.
[4]
Mariam Md Ghazaly, Kaiji Sato: Control Performances of a Fine Motion Stage using a Multilayer Electrostatic Actuator without Precise Balls for Lubrication, Proc. of the 4th International Conference on Mechatronics Technology (ICMT2010), (Osaka, Japan), (2010.11)
[5]
Mariam Md Ghazaly, Kaiji Sato: Open-loop Characteristics of a Multilayer Electrostatic Actuator for a Fine Motion Stage, Proc. of ICMT2010, (Osaka, Japan), (2010.11)