• Journal of the Korean Society for Precision Engineering
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• v.29 no.4
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• pp.367-372
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• 2012

The biggest factors that lower the machining accuracy are thermal deformation and chatter vibration. In this article, we introduce the study case of technology that can automatically compensate the errors of these factors of a machine during processing on the machine tool's CNC(Computerized Numerical Controller) in real time. This study is related to the detection and compensation of thermal deformation and chatter vibration that can compensate for faster and produce processed goods with more precision by autonomous compensation. In addition, this study is related to the active control of vibration during machining, monitoring of cutting force and auto recognition of machining axes origin. Thus, we attempt to introduce the related contents of the development we have made in this article.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.5
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• pp.65-72
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• 2002

In this study, actuator, sensor, guide, power transmission element and control method are considered for ultra-precision positioning apparatus. Through previous process, single plane X-Y stage with ultra-precision positioning is manufactured. Global stage for the purpose of materialization with robust system, is combined by using AC servo motor and ball screw and rolling guide. And ultra-precision positioning system is developed by micro stage with elastic hinge type and piezo element. global servo and micro servo for the purpose of materialization positioning accuracy with nm(nanometer) are controlled simultaneously by using incremental encoder and laser interferometer as displacement measurement sensor. Through previous process, ultra-precision positioning system(100mm stroke and $\pm$ l0nm positioning accuracy) with single plane X-Y stage are materialized.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.249-254
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• 1992

Hydrostatic Bearings have been applied to ultra high precision machine tools and precision instruments, because of their low friction characteristic, high load carrying capacity and high moving accuracy at all range of speed. In regard to realizing the Hydrostatic Bearing, various restrictors such as capillary, orifice, diaphram valve, spool valve, and etc can be used. However, their stiffness and flexibility are not sufficient in practical use for ultra precision machine tool elements. In this study dynamic equations were derived and the dynamic characteristics were simulated for both orifice and flow control servo valve. Simulation was carried out on the condition that static and sinusoidal dynamic loads were applied to the table of CNC jig Boring machine. The simulation results indicate the improvement of the performance of the Bearing system when flow control servo valve has been used as restrictor of Hydrostatic Bearing.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.4
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• pp.463-467
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• 2014

High precision machining technology has become one of the most important parts in the development of a precision machine. Such a machine requires high precision positioning as well as high speed on a large workspace. For machining systems having high precision positioning with a long stroke, it is necessary to examine the repeatability of the reference position decision. Though ball-screw driven linear stages equipped with linear scale have high precision feed drivers and a long stroke, they have some limitations for reference position decisions if they have not been equipped with an accurate home sensor. This study is performed to experimentally examine the repeatability for home position decision of a photo micro sensor as a home switch of a ball-screw driven linear stage by using a capacitance probe.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.228-233
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• 2009

An ultra-precision stage is used in many industrial areas such as precision machine tools or semiconductor apparatus. These stages used to be driven by piezoelectric actuators in order to obtain ultra precision positioning resolution. Piezoelectric actuator can be moved fast in nanometer resolution. However, it has relatively large non-linear characteristics like hysteresis and creep curve. Although several kinds of control techniques have been developed, controller design method is still complicated. In this paper fuzzy control rules are developed intuitively. In order to verify the performance a series of experiments were conducted and the results were compared with those of the PID controller case.

• 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.16 no.5 s.98
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• pp.186-193
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• 1999

Sensor feedback for process control is one of the essential elements is an automated deburring procedure. This paper presents the implementation of acoustic emission (AE), which has been developed as a feedback sensing technique for precision (mechanical) deburring, in a precision laser deburring process. AE signals were sampled for laser machining/deburring under various experimental conditions and analyzed using several signal-processing methods including AErms and spectral analysis. The results, such as the sensitivity of AE signals for different laser cutting depths, edge detection capability and the frequency analysis show a clear correlation between physical process parameters and the AE signals. A subsequent control strategy for deburring automation is also briefly discussed.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.11
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• pp.9-15
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• 1999

A piezoelectric actuator is widely used in precision positioning applications due to its excellent positioning resolution. However, the piezoelectric actuator lacks in repeatability because of its inherently high hysteresis characteristic between voltage and displacement. In this paper, a controller is proposed to compensate the hysteresis nonlinearity. The controller is composed of a PID and a neural network part in parallel manner. The output of the PID controller is used to teach the neural network controller by the unsupervised learning method. In addition, the PID controller stabilizes the piezoelectric actuator in the beginning of the learning process, when the neural network controller is not learned. However, after the learning process the piezoelectric actuator is mainly controlled by the neural netwok controller. In this paper, the excellent tracking performance of the proposed controller was verified by experiments and was compared with the classical PID controller.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.123-124
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.21-22
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• 2008