Sub-Nanometer Positioning Combining New Linear Motor with Linear Motion Ball Guide Ways

A new type of linear motor described in this paper has some advantages compared with the usual types of motors. The attractive magnetic force between the stator (permanent magnets) and mover (armature) is diminished almost to zero. The efficiency is better because the magnetic flux leakage is very small, the size of motor is smaller and detent (force ripple) is smaller than the general motors. Therefore, we think that this motor is greatly suitable for ultra-precision positioning as an actuator. An ultra-precision positioning device using this motor and liner motion ball guide ways is newly developed. Moreover, the positioning performance is evaluated by a positioning resolution, deviational and dispersion errors. As the results of repeated step response tests, the positioning resolution is 0.3 nm, the deviational error is -0.001nm and the dispersion error (3σ) is 0.29 nm. Consequently, the positioning device achieves sub-nanometer positioning. In addition, very large rigidity can be achieved.

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Sub-Nanometer Resolution Positioning Device Driven by New Type of Linear Motor with Linear Ball Guideways – Considering Time Lag of Electric Control System –

International Journal of Automation Technology ◽

10.20965/ijat.2011.p0832 ◽

2011 ◽

Vol 5 (6) ◽

pp. 832-841 ◽

Cited By ~ 1

Author(s):

Toshiharu Tanaka ◽

◽

Jiro Otsuka ◽

Ikuro Masuda ◽

Yasuaki Aoyama ◽

...

Keyword(s):

Control System ◽

Time Constant ◽

Current System ◽

Time Lag ◽

Linear Motor ◽

Current Control ◽

Nonlinear Spring ◽

Electric Control ◽

Positioning Device ◽

New Type

We have developed an ultra-precision positioning device that has the following characteristics: 1) The 210 mm strokes stage is driven by a new type of linear motor called “Tunnel Actuator (TA).” 2) The stage has very rigid structure so as not to cause vibration and to achieve high resolution for its feed-back system. 3) The stage is supported by linear ball guideways that have nonlinear spring behavior in the small stroke range. 4) Much attention has been paid to the time lag of the electric control system in the PID control using a linear encoder of 0.034 nm resolution for the feed-back system. The electric control system compensates for the disturbance of induced electromotive voltage that is generated in proportion to the stage velocity. We have studied how the equivalent time constant T of the control system affects the stage displacement deviation Δx when the command of stage displacement xr is kept at zero. The following results have been obtained: 1)With a decrease in time constant T of the current control system, the change in the motor current Io becomes smaller, and, at the same time, the change in stage deviation Δx becomes smaller. 2) At the smallest time constant T of the current system, a displacement resolution of 0.2 nm has been obtained under the nonlinear spring behavior of linear ball guideways. 3) There is a possibility of obtaining a displacement resolution of less than 0.1 nm with a further decrease in T.

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Development of ultra-precision positioning technique with linear motor.

Journal of the Japan Society for Precision Engineering ◽

10.2493/jjspe.56.1829 ◽

1990 ◽

Vol 56 (10) ◽

pp. 1829-1834

Author(s):

Masanori SUEMATSU ◽

Takao FUJII ◽

Atsushi KAWAHARA ◽

Tomoaki TANIMOTO ◽

Toshio MATSUMOTO ◽

...

Keyword(s):

Linear Motor ◽

Precision Positioning ◽

Ultra Precision ◽

Positioning Technique

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On-Line Force Ripple Identification and Compensation in Precision Positioning of Wafer Stages

Volume 9: Mechanical Systems and Control, Parts A, B, and C ◽

10.1115/imece2007-42563 ◽

2007 ◽

Cited By ~ 1

Author(s):

Shu-Wen Yu ◽

Sandipan Mishra ◽

Masayoshi Tomizuka

Keyword(s):

Adaptive Estimation ◽

Tracking Error ◽

Linear Motor ◽

Feedback Controller ◽

Precision Positioning ◽

Positioning Systems ◽

Line Force ◽

Nonlinear Force ◽

On Line ◽

Force Ripple

This paper presents the design and implementation of a composite controller to reduce the effect of force ripple in a linear motor wafer stage system. The composite controller consists of two components: 1) a PID feedback controller and 2) an adaptive feedforward compensator. The feedback controller is tuned to achieve good transient response and enhanced robustness of the system. Force ripples are a major source of tracking error in linear motor precision positioning systems. An approximation of the nonlinear force ripple model can be obtained by expressing the ripple as the sum of a sequence of sinusoidal harmonics, multiplied by the motor current. The force ripple is first approximated by on-line adaptive estimation of the unknown coefficients associated with each harmonic, and then compensated with a feedforward term. Experimental results on a prototype single degree of freedom wafer stage are presented to show the performance improvement obtained by the proposed control scheme.

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Ultra-Precision Positioning Using Linear Motion Ball Bearings and Linear Motor

Journal of the Japan Society for Precision Engineering ◽

10.2493/jjspe.82.881 ◽

2016 ◽

Vol 82 (10) ◽

pp. 881-887

Author(s):

Toshiharu TANAKA ◽

Kazuki ADACHI ◽

Takaaki OIWA ◽

Akira KOTANI ◽

Jiro OTSUKA

Keyword(s):

Linear Motor ◽

Ball Bearings ◽

Linear Motion ◽

Precision Positioning ◽

Ultra Precision

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Magnetic suspension mechanism using rotary permanent magnets

International Journal of Applied Electromagnetics and Mechanics ◽

10.3233/jae-209412 ◽

2020 ◽

Vol 64 (1-4) ◽

pp. 977-983

Author(s):

Koichi Oka ◽

Kentaro Yamamoto ◽

Akinori Harada

Keyword(s):

Permanent Magnets ◽

Suspension System ◽

Magnetic Suspension ◽

Horizontal Force ◽

Mechanical Contact ◽

New Type ◽

Magnetic Suspension System

This paper proposes a new type of noncontact magnetic suspension system using two permanent magnets driven by rotary actuators. The paper aims to explain the proposed concept, configuration of the suspension system, and basic analyses for feasibility by FEM analyses. Two bar-shaped permanent magnets are installed as they are driven by rotary actuators independently. Attractive forces of two magnets act on the iron ball which is located under the magnets. Control of the angles of two magnets can suspend the iron ball stably without mechanical contact and changes the position of the ball. FEM analyses have been carried out for the arrangement of two permanent magnets and forces are simulated for noncontact suspension. Hence, successfully the required enough force against the gravity of the iron ball can be generated and controlled. Control of the horizontal force is also confirmed by the rotation of the permanent magnets.

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