• Journal of the Korean Society for Precision Engineering
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• v.19 no.7
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• pp.64-70
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• 2002

The positioning system fur the ultraprecision machine tool should have nanometer order of positioning resolution. For the purpose of achieving that resolution, various feed drive devices have been proposed and currently hydrostatic lead screw and friction drive are paid attention. It is reported that an angstrom resolution can be achieved by using twist-roller friction drive. So we have manufactured ultraprecision feeding system driven by the twist-roller friction drive and perform performance assessment for problem definition and solution finding. As a result, we found that the twist-roller friction drive is mechanically suitable for ultraprecision positioning but some considerations are needed to get higher resolution.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.2
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• pp.44-49
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• 2008

This paper describes the problem of ultraprecision positioning with a ball screw mechanism in the microdynamic range, along with its solution. We compared the characteristics of two ball screw mechanisms with different table masses. The experimental results showed that the vibration resulting from the low stiffness of the ball screw degraded the positioning performance in the microdynamic range for the heavyweight mechanism. The proposed nominal characteristic trajectory following (NCTF) controller was designed for ultra precision positioning of the ball screw mechanism. The basic NCTF control system achieved ultra precision positioning performance with the lightweight mechanism, but not with the heavyweight mechanism. A conditional notch filter was added to the NCTF controller to overcome this problem. Despite the differences in payload and friction, both mechanisms then showed similar positioning performance, demonstrating the high robustness and effectiveness of the improved NCTF controller with the conditional notch filter. The experimental results demonstrated that the improved NCTF control system with the conditional notch filter achieved ultra precision positioning with a positioning accuracy of better than 10 nm, independent of the reference step input height.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.9-15
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• 2000

• Journal of the Korean Society for Precision Engineering
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• v.30 no.12
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• pp.1313-1320
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• 2013

An ultraprecision multi-axis machine tool has been designed and developed in our laboratory. The machine tool has four moving axes which are composed of three linear axes and one rotational axis. It has a gantry type structure and the Z-axis is on the X-axis and the C-axis, on which a workpiece is located, is inside the Y-axis. This paper shows control performance improving method and procedure for the ultra-precision positioning control of a hydrostatic bearing guided linear axis. Through improvements of electrical and mechanical components for the control system such as control electronics and oil pumping systems, the control disturbing noise is decreased. Also by the frequency domain analysis of control system those problem-making system components are identified and modified with analytical methods. The controller is analyzed and designed from frequency domain data and system information. In the experimental control results the nanometer order control result is successfully presented.

• International Journal of Precision Engineering and Manufacturing
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• v.6 no.3
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• pp.8-12
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• 2005

The positioning system for an ultra precision machine tool must be accurate to the order of a nanometer. Various feed drive devices have been proposed to achieve this resolution; currently, most attention is directed towards hydrostatic lead screws and friction drives. It has been reported that a positioning resolution accurate to an angstrom can be achieved using a twist-roller friction drive. Therefore, we manufactured an ultra precision positioning system driven by a twist-roller friction drive and assessed its performance when defining problems and finding solutions. Our study showed that the twist-roller friction drive is mechanically suitable for ultra precision positioning, but some considerations are required to obtain a higher resolution.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.658-661
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• 1996

For ultraprecision positioning, the use of the twist roller-type friction drive is proposed. In our study, it is difficult to decrease the resolution of positioning below 100 nm when we use general servo motors. Therefore we propose the feed hive with a small lead like a the cam-roller type traction drive leadscrew and modify it more accurately. By using the semi-loop control system, the positioning resolution of the drive can be 22.4 nm, where the pulse per revolution of the motor is 655360 and the the lead is 0.734 mm.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.6
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• pp.7-16
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• 2010

Physical fundamentals of ultrashort femtosecond lasers are addressed along with emerging applications for precision manufacturing and metrology. Femtosecond lasers emit short pulses whose temporal width is in the range of less than a picosecond to a few femtoseconds, thereby enabling extremely high peak-power machining with less thermal damages. Besides, the broad spectral bandwidth of femtosecond lasers constructed in the form of frequency comb permits absolute distance measurements leading to ultraprecision positioning control and dimensional metrology.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.123-128
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• 2005

A novel tri-mode ultraprecision positioning system for machine tools and measuring machine is proposed. The basic coarse mode uses a Twist-roller Friction Drive (abbr. TFD), and controls several tens of millimeters of the machine-table travel with nanometer order of positioning resolution. The fine mode also utilizes the TFD with a fine adjusting mechanism. The resolution of the fine mode is in the range of sub-nanometer. For realizing picometer positioning, the ultra-fine mode is executed by using an active aerostatic guideway. On the bearing surface of this active guideway, several Active Inherent Restrictors (abbr. AIRs) are embedded for controlling the table position. An AIR unit consists of a piezoelectric actuator having a through hole, one end of the hole on the bearing surface acts as an inherent restrictor. Owing to the aerostatic mechanism of the AIR, the deformation of the piezoelectric actuator in the AIR unit causes much reduced table displacement. Such motion reduction is effective for ultraprecision positioning. Current positioning resolution of the ultra-fine mode is 50pm, however the final goal of the positioning resolution is expected to be in the order of picometer.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.249-254
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• 1993

In order to respond to the increasing demands of ultraprecision positioning mechanism in the field of precision engineering, more accurate stages are needed whose positioning uncertainty should be in the unprecedented level of nanometers, while maintaining a long travek range. For this application, most conventional stage mechanisms are found not suitable, so the concept of dual servo, which uses two different servos, is one of the new design and control strategies being extensively investigated these days, This paper presents a fine motion mechanism as a part of research on the dual servo control. The stage is made of a single structure of elastic flexure, whose xy .theta. motions are induced in the form of elastic deformation activated by three piezoelectric actuators. Experimental results show that the translational and rotational motions of the stage can be controlled with resolutions of 5 nm and 0.1 arcsec, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.175-178
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• 2000

An aerostatic stage has frictionless behavior, so it has a advantage of investigation into positioning characteristics. A one-dimensional aemstatic ceramic stage with ballscrew driven and laser scale feedback system is manufactured. aiming at investigating positioning characteristic of aerostatic stage, especially position error and repeatability, we analyze positioning behavior with other factors such as angular error, temperature. Experimemal results show that the aerostatic stage has a l0nm micro step response. Comparing experimental results and calculated abbe's error, we confirm that mean of position error is owing to angular error. And, also we confirm the temperature is dominant factor of repeatability in ten nm order.