Ultra-precision Positioning Research Articles

弾性変形要素を付加したすべり送りねじによる超精密位置決め １ 摩擦特性と弾性変形機構

The sliding leadscrew is a machine element used most generally in positioning technology. However, because of excessively discontinuous characteristic of friction between a male screw and a female one, it becomes an improper element for ultra-precision positioning. This study aims at improving such negative situation by a new technique. In the technique, axial displacement caused by deformation of an elastic element attached in series to a sliding lead screw is utilized for minute positioning motion under a full-closed displacement control. The deformation generated is adjusted by friction torque within maximum static friction. As the first report, this paper deals with friction characteristic in a sliding lead screw which must be basically known for this technique, and the structure and design of the elastic element. From experiments simulated to the case, it is confirmed that usable state of static friction exists clearly in use of lubricants for positioning. Experiments about function of the elastic elements equipped in a positioning apparatus show good results nearly as expected and possibility of ultra-precision positioning at nano-meter level.

Ultraprecision Positioning by Preload Change of Lead Serews. Characteristics of Fine Feed.

The ultraprecision positioning is examined against the fine feed system utilized the elastic deformation of lead screws accompanying preload change in double nuts. The nonlinear deformation due to Hertzian contact of ball screw can ignore within a feed of 1 μm under adequate initial preload. The influence of load on table displacement of nanometer order is not observed in the range from 10 to 50 kg. The displacement obtained under increase in preload coincide well with the result under decrease in preload also. Feed control with preload change based on one to one correspondence of preload change and displacement is effective to avoid the hysteresis phenomenon of PZT actuator adopted as deformable spacing part between double nuts. Further, preload can use as a measure to detect table displacement in place of position sensor which sometimes shows unreliability owing to unstable situation in nanometer region. The minimum step feed deduced from preload change is 1 nm for sliding screw and 5 nm for ball screw.

専門委員会研究レビュー 超精密位置決め専門委員会 超精密位置決めにおける文献とアンケート調査

専門委員会研究レビュー 超精密位置決め専門委員会 超精密位置決めにおける文献とアンケート調査

Fine Feed by Preload Change of Lead Screws. Application to Ultraprecision Positioning.

In the preloaded double nuts of lead screw, the nuts displace slightly in the axial direction with the preload change because of the deformations of threads and screw, nut body. To apply this small displacement to the fine feed in ultraprecision positioning, the nut displacement characteristics accompanying preload change are examined against ball and sliding screws. Theoretical displacement is the order of nanometer with preload change of 1N and less displacement is easy to obtain under low spacing part stiffness. The experimental results obtained by the feed units show the step feed of from nanometer to submicron and the range of fine feed comes to several microns. The feed drive equipped with preload control lead screw has the advantage of high resolution positioning over a long traverse path by using it in combination with coarse positioning of screw rotation and fine positioning of preload control.

Development of a “walking drive” ultraprecision positioner

The present paper presents a new mechanism to feed a precision table continuously over a long stroke with high rigidity by utilizing deformations of piezoelectric actuators. A driving method names “walking drive” is employed for the mechanism with which the table is driven in a similar way to the walking motions in animals. A precision feed device is developed, and ultraprecision positioning experiments are carried out by using the device combined with a laser-feedback system developed. It is confirmed that the positioner driven by the walking drive has the following advantages: (1) positioning resolution of 5 nm is realized with a simple control method and a simple mechanism, because of no friction against the feed motion; (2) smooth continuous path control with the following error of less than 10 nm is realized over a long stroke despite short strokes of the piezoelectric actuators; and (3) high stiffness of greater than 350 N/μm is realized in the feed direction.

専門委員会研究レビュー 展望 超精密位置決め専門委員会 最新精密・超精密位置決め事情

専門委員会研究レビュー 展望 超精密位置決め専門委員会 最新精密・超精密位置決め事情

Industrial Uses of STM and AFM

We review the field of STM and AFM as applied to industrial problems, and we classify the applications into four classes: research with potential benefit to industry, research performed by industry, applications off-line in manufacturing, and applications on-line in manufacturing. We also discuss the role of metrology for certain applications and briefly review many other types of SPMs besides STM and AFM. We conclude by emphasizing ultra-precision positioning, nanofabrication, and biomedical applications as important future directions in the field.

超精密位置制御に関する研究 (第2報)

超精密位置制御に関する研究 (第2報)

Research and development of an ultraprecision positioning system

This paper describes a positioning system for ultraprecision machine tools. This system has a hydrostatic slide table driven by a hydrostatic lead screw (36 mm diameter, pitch 10 mm) and a laser interferometric positioning system. This means that the table is supported by hydrostatic bearings in any direction absolutely without any mechanical contact. Quite high accuracy of straight motion and positioning is realized and maintained; straightness and angular deviation are better than 50 nm and 2 mu rad respectively, positioning accuracy is about 10 nm within a 200 mm stroke. In addition, the effect obtained by a self-controlled restrictor for screw and by a short-pitch (pitch 6 mm) lead screw is mentioned. The stiffness of the hydrostatic screw in the feed direction can be statically infinite with this restrictor. By the use of this lead screw, positioning accuracy is improved and a 0.1 nm positioning step is possible.

Precision position control of piezoelectric actuators using charge feedback

The issue of precision position control is critical if piezoelectric actuator technology is to be applied in increasingly demanding applications. In one particular application, the NASA NAOMI project, piezoelectric actuators have been proposed as the pointing and focusing elements for thousands of small mirror-lenslets because of their fast response time and load- carrying ability. In this application the positions of these actuators must be precisely controlled both statically and dynamically to the nanometer level. This requirement necessitates a careful study of the concept and design of the driving electronics of the system. This paper is focused on finding an appropriate method for driving piezoelectric stack actuators for ultraprecision position and motion control. In this paper the theoretical basis of the electrical control of piezoelectric stack actuators is derived using the fundamental physical laws governing dielectrics and piezoceramics. It is shown that the relationships used for voltage control of piezoelectric actuators result from an approximation of the constitutive equations. An exact input/output relationship for piezoelectric actuators is derived and shows that displacement relies fundamentally on charge, not voltage. Experimental verification was obtained to illustrate the differences between driving piezoactuators with voltage control and charge control.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Walking Driveによる精密送り機構の開発 (第2報)

This paper presents a method to control feed velocity of precision feed devices driven by means of walking drive, and ultraprecision positioning is realized by a laser feedback controller developed. It is confirmed that the feed velocity can be controlled easily and simply by the method presented. Major results obtained are as follows ; (1) Positioning accuracy of 5 nm is realized, because of no friction against the feed motion. (2) Smooth continuous path control is realized despite short strokes of the piezoelectric actuators. (3) High stiffness of about 40 N/μm is realized in the feed direction.

超精密位置決めのための最新技術 変位センサと超精密位置決め

超精密位置決めのための最新技術 変位センサと超精密位置決め

超精密位置決めのための最新技術 アンケート調査に見る超精密位置決め技術に関する現状と期待

超精密位置決めのための最新技術 アンケート調査に見る超精密位置決め技術に関する現状と期待

An angstrom-positioning system using a twist-roller friction drive

We propose a positioning system with an angstrom resolution. The positioning system has a table guided by a hydrostatic guideway, and a twist-roller friction drive is incorporated into the table. The friction drive converts the rotation of an AC servo driving motor into the linear motion of the table. The twist-roller friction drive is advantageous for ultraprecision positioning, because its lead can be less than 0.1 mm. Monitoring the displacement of the table by a fiber optic displacement sensor, a microcomputer in the system controls the rotational angle of the AC servomotor. Step positioning with several step widths is executed, and it is proved that the positioning resolution is 0.2 nm (2Å). The stroke of the system can be several hundred millimeters. Thus, it is shown that the twist-roller friction drive is suitable for the angstrom-positioning system.

超精密位置決めのための最新技術 超精密位置決め技術の現状と今後

超精密位置決めのための最新技術 超精密位置決め技術の現状と今後

超精密位置決めのための最新技術 インテリジェント制御による位置決め技術

超精密位置決めのための最新技術 インテリジェント制御による位置決め技術

超精密位置決めのための最新技術 工作機械の超精密化と高剛性化の同時達成技術

超精密位置決めのための最新技術 工作機械の超精密化と高剛性化の同時達成技術

超精密位置決めのための最新技術 ステッパの新露光方式と位置決め技術の改新

超精密位置決めのための最新技術 ステッパの新露光方式と位置決め技術の改新

Control and Elimination of Lead Screw Backlash for Ultra-Precision Positioning

This paper describes the principle of an active lead screw mechanism (ALSM)and the basic characteristics of its experimental mechanism. The ALSM comprises a lead screw, two nuts, piezoelectric actuators (PEAs) and a movable table. The table is connected to the nuts through the PEAs so that the PEAs can control not only the backlash between the screw and nuts but also the position of the table. The ALSM has the following capabilities : (1) when the table is to be driven at a high speed and positioned coarsely by a motor, sufficient backlash can be created between the screw and nuts, (2) after the table is positioned coarsely, the backlash can be eliminated by the PEAs so as to give the ALSM a sufficient stiffness, and (3) while keeping the backlash at zero, the table can be positioned precisely by the PEAs. The experimental mechanism achieved the following : (1) the maximum table speed of 130mm/s, (2)the positioning accuracy of better than 10nm, and (3) the positioning time for a 10mm step input of 369ms.

超精密位置決めのための最新技術 ナノメートルからピコメートルへ 変位センサの高精度・高性能化

超精密位置決めのための最新技術 ナノメートルからピコメートルへ 変位センサの高精度・高性能化