• International Journal of Precision Engineering and Manufacturing
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• v.8 no.2
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• pp.85-89
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• 2007

Linear ball guideways have been used recently in precision or ultra-precision positioning devices. However, when the inner balls begin to roll or the moving direction reverses, these guideways are subject to rolling friction or nonlinear spring behavior. An ultra-precision device with a linear motor, referred to as a 'tunnel actuator' (TA), has been constructed to measure these phenomena. The application of a TA is beneficial for two reasons: it mostly cancels the attractive magnetic force between the stator and mover (armature), and its magnetic flux leakage is very low. The influence of the nonlinear spring behavior in ball guideways was investigated in this study using the pure driving force from a TA. The equilibrium between the driving force from the TA and the nonlinear spring force provided great accuracy for a positioning stage using a linear ball guideway.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.118-122
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• 2000

Recently, High accuracy and precision are required in various industrial field especially, semiconductor manufacturing apparatus, Ultra precision positioning apparatus, Information field and so on. Positioning technology is a very important one among them. For composition of this technology, the development of system with high speed and high resolution is needed. At start point and end position vibration must be repressed on this system for composition of position control. This vibration is arisen nose, is increased setting time, is reduced accuracy. Especially, repressed for the lead with high speed. The small actuator with high speed and high resolution is need to repression against this residual vibration. This actuator is, for example, piezo actuator, piezoelectric material that converting from electronic signal to mechanical force is adequate material, beacause of control of control to position and force. In this study, piezo electric material is used to actuator, ultra precision positioning apparatus with stage of hinge structure is designed, simulation is performed, control performance is tested by producing apparatus. For easy usage and stability in industrial field, we perform to simulation and to position control test by digital PID controller.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.3
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• pp.263-268
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• 2015

This paper describes lost motion analysis for a novel 6-DOF ultra-precision positioning stage. In the case of flexure hinge based precision positioning stage, lost motion is generated when the displacement of actuator is not delivered completely to the end-effector because of the elasticity of flexure hinge. Consequently, it is need to compute amount of lost motion to compensate the motion or to decide appropriate control method for precision positioning. Lost motion analysis for the vertical actuation unit is presented. The analysis results are presented in two ways: analytic and numerical analyses. It is found that they closely coincide with each other by 1% error. In finite element analysis result, the amount of lost motion is turned out to be about 3%. Although, the amount is not so large, it is necessary procedure to check the lost motion to establish the control method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.37-41
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• 2002

Thermal characteristics of hydrostatic guideway is largely depended on the temperature of supplied oil. For improving the positioning accuracy of hydrostatic guideway, relationship between setting temperature of oil cooler and thermal characteristics is analyzed, and influence of thermal characteristics on positioning accuracy is also analyzed experimental1y in this paper. Laser scale which has 0.01 $\mu\textrm{m}$ of resolution is used as feed-back unit. From the experimental results, it is confirmed that positioning error and repeatability is minimize upto 0.21 $\mu\textrm{m}$ and 0.18 $\mu\textrm{m}$ when the temperature of supplied oil is setting equal to temperature of atmosphere, and also confirmed that thermal deformation, which occurs by the temperature deviation between table and rail or scale supporter, works as limit of repeatability in long time operation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.266-272
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• 1994

An essential ingredient in precision machining is a positioning system that responds quickly and precisely to very small input signal. In this paper, two different positioning systems were presented fot the precision positioning control. The one is a friction drive system, the other is a ballscrew system. The friction drive system was composed of an air sliding guide and a friction drive. The ballscrew system was made of a ballscrew and a linear guide. Nonlinear behaviors of the given systems tend to make the system inaccurate. The paper looked at the phenomena that has caused the positioning error. These apparently nonlinear phenomena can be attributed mainly to the presence of the nonlinear friction and slip effect plus the dynamic change from the microdynamic to the macrodynamic and form the macrodynamic to the microdynamic. For the control of the positioning system, the control algorithm based on a neural network is suggested. The FEL(Feedback Error Learning) controller can learn the inverse dynamics of a nonlinear system by using the neural network controller, and stabilize the system by a linear controller. In the experiment, PTP control is implemented withen the maximum error of 0.05 .mu.m ~0.1 .mu. m when i .mu.m step reference input is applied and that of maximum 1 .mu. m when 100 .mu.m step reference input is given. Sinusoidal inputs with the amplitude of 1 .mu.m and 100 .mu. m are used for the tracking control of the positioning system. Experimental results of the proposed algorithm are shown to be superior to those of conventional PD controls.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.465-468
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• 2001

An aerostatic stage has frictionless behavior, so it has a advantage of investigation into positioning characteristics. A one-dimensional aerostatic ceramic stage with ballscrew driven and laser scale feedback system is manufactured, aiming at investigating positioning characteristic of ultra-precision stage. We confirm, this ceramic aerostatic stage has a 10nm micro resolution, and can be reduced mean of position error by compensation of numeric control command. By means of analyzing relationship of position error and change of temperature, we build a on-line compensation algorithm of position error from the measured temperature data. So we can improve repeatability of ultra-precision stage up to 34%($0.095{\mu}$) of the normal condition.

• 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.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.161-166
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• 2002

Recently, researches on precision machining of nato-order, especially in the field of optical components and semi-conductors have been under development very actively. A accuracy of machining and positioning in a critical issue in ultra-precision machining. This paper proposes a new positioning system which can give excellent dynamic characteristics and reduce errors in horizontal, vertical, pitching, and yawing motions. In this paper, we suggest a connecting mechanism (the couplings) to reduce motion errors such as chatter and runout while preserving the positioning accuracy. We verified the good performance in the new connecting systems with various coupling types, which we classified into the fixed type, the spring type, the aeroctatic-nozzle type, and the aeroctatic-porous type according to the way of reducing the chatter and error.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.88-93
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• 1996

The study was carried out development a pricision positioning apparatus, consisting of DG servo motor and piezoelectric actuatior. This system is composed of fine and coarse apparatus, measurement system and control system. Peezoelectric actuator is designed for fine positioning. Coarse positioning using lead screw is droved by DC servo motor. Control system output a signal from laser interfermeter and capacitive sensor to amplifer of DC servo motor and piezoelectric actuator after digital signal processing (DSP). Resolution of this apparatus measure with laser interferometer and microsense

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.621-622
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• 2012