This study quantitatively investigates the deviation between the ideal and effective amplification ratios of a bridge-type displacement amplification mechanism used in ultra-precision positioning systems. It proposes region-specific optimal design strategies to mitigate this deviation. A Leave-One-Out sensitivity analysis reveals that the dominant factor influencing amplification ratio deviation shifts at an ideal amplification ratio of approximately 10. In the high-amplification region (R > 10), displacement loss due to bending of the input link is identified as the primary cause of deviation. Reinforcing the input link's thickness and incorporating a pocket structure reduces the deviation to within 12.4% while minimizing resonance frequency degradation. Conversely, in the low-amplification region (R < 7), the main issue is dynamic performance deterioration caused by oversized intermediate links. Implementing a hexagonal mass-reduction design enhances the first resonance frequency by up to 28% without compromising the amplification ratio. These findings establish differentiated design guidelines based on the target amplification ratio, enabling simultaneous improvements in precision and dynamic performance for bridge-type displacement amplification mechanisms in positioning systems.
A circular flexure hinge is a core element for force transmission and relative motion of precision stages used in semiconductor processes. When designing a circular flexure hinge, calculation formulas for axial and rotational compliance are essential. However, in the case of axial compliance, results of the existing calculation formulas have significant differences from reliable finite element analysis results. In this study, calculation formulas for axial compliance of the circular flexure hinges were derived based on stress distribution phenomenon. Comparison with finite element analysis results confirmed that the newly developed calculation formulas were more accurate than existing ones. It is anticipated that these enhanced formulas will lead to more precise designs, ultimately reducing both time and costs in research and industry.
This study introduces a novel tip-tilt-piston aligner based on aligned folded beam flexure. It was designed to enhance precision positioning by minimizing parasitic motion. Through finite element analysis, we compared this aligner with a traditional folded beam flexure-based mechanism, revealing a remarkable 135% increase in translational stiffness and superior rotational stiffness ratios. These advancements are expected to reduce parasitic motion arising from actuator misalignment and external disturbances, ultimately elevating positioning accuracy. The aligner’s suitability as a guiding device was affirmed and optimal actuator placement positions were determined. This research provides valuable insights into precision positioning mechanism design, underscoring the role of flexure geometry and precise actuator placement in minimizing parasitic motion for improved accuracy.
Recently, with the development of the space, mobility, semiconductor, and precision machinery industries, the processing of precision mechanical parts has been recognized as an important and a high value-added technology. Research on ultra-precision processing is actively underway to produce such products. In addition, eco-friendliness and 0% carbon are emerging as key keywords in modern industrial society, and the need for this is also increasing in the ultra-precision processing field. As the industry advances, environmental issues are becoming a major concern, and in the processing technology field, environmental destruction caused by cutting oil is becoming an issue. To solve this problem, this study measured the movement precision of the global feed system and instaled a Fine Servo that corrects the nm-level movement of the feed system in real time, using a piezoelectric actuator, to finely drive the cutting tool to control the movement necessary for machining. We intended to control variables for ultra-precision machining and measure cutting heat generation in real time to establish a dry cooling method using thermoelectric elements without using cutting oil.
With advancements in semiconductor manufacturing processes and the development of precision processing technology, flexure hinge-based ultra-precision positioning stages are widely used. In the flexure hinge, axial and bending stiffness properties greatly influence positioning performance. This study examined the stiffness properties of elliptic and parabolic 2-degrees-of-freedom (DOF) hinges, which have not been extensively discussed. The Timoshenko beam theory was applied to derive the stiffness equations for the axial and bending directions of each hinge. The stiffness properties were examined in several design conditions by comparing theoretical and finite element analyses. Based on the results of the analyses, an empirical formula in exponential form for the design of an elliptic hinge was constructed through surface-fitting. The elliptic hinge was found to be a better alternative to a circular hinge under certain design conditions by adjusting two design parameters. In the future, we will develop sophisticatedly designed hinges with improved axial and bending stiffness properties compared to the existing circular and elliptic hinges.
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Derivation and Verification of Novel Phenomenon-based Theoretical Formulas for the Axial Compliance of Circular Flexure Hinges Jun-Hee Moon, Hyun-Pyo Shin Journal of the Korean Society for Precision Engineering.2025; 42(1): 47. CrossRef
In the framework of the 4th industrial revolution, modern machine building rapidly converges with IOT technology. This requires a very high level of precision machining of parts and assemblies, such as electronics, vehicle and components, agricultural and construction machines, optical instruments, and machine tools. However, high precision machinery is considerably expensive, and so a general need for low-cost equipment exists. While many researchers study this, they focus mainly on cutting tools. This study, for its part, focused on compensating errors and enhancing machinery precision, by adding a servo controller to the processing unit. As a result, we designed a fine dual servo system, ensuring 10 nm positioning accuracy and 40 nm of surface roughness.
Flexure hinges are widely used as joint linkages for precision stages applied to lithography processes. Among them, precision stages with 3 DOF (Degrees of Freedom) of x, y and θz prevail in semiconductor manufacturing and they have been adopting single directional flexure hinges as mechanical linkages without backlash and debris. However, new technologies including nano-imprinting, which replaces lithography, needs more than 3 DOF precision positioning stages that adopt cylindrical flexure hinges. In this study, the cylindrical flexure hinges with circular notches were analyzed using the Timoshenko beam theory and FEM (Finite Element Method), with focused on their directional stiffness. Based on the analysis and result comparison between theoretical equations and FEM, several practical suggestions for determining important design variables are provided in the conclusion of this study.
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Derivation and Verification of Novel Phenomenon-based Theoretical Formulas for the Axial Compliance of Circular Flexure Hinges Jun-Hee Moon, Hyun-Pyo Shin Journal of the Korean Society for Precision Engineering.2025; 42(1): 47. CrossRef
Analysis on Elliptic and Parabolic 2-DOF Flexure Hinges for Spatial Positioning Stages Hyun-Pyo Shin, Jun-Hee Moon Journal of the Korean Society for Precision Engineering.2023; 40(3): 229. CrossRef
In ultra-precision processes, such as aerospace parts and precision mold machining, the accuracy of a feed drive system should be secured to achieve sufficient form accuracy. Dual-Servo stages, which compensate for multi-DOF motion errors, are being developed depending on the applied processes. This paper deals with the fine stage of a dual-servo stage to compensate for 6-DOF motion errors of a linear stage. The proposed fine stage measured 6-DOF errors of the linear stage motion with capacitive sensors, a reference mirror, and an optical encoder. It compensated for the errors using the flexure hinge mechanism with piezo actuators. The error equations and the inverse kinematics were derived to calculate the 6- DOF errors and displacements of piezo actuators for 6-DOF motions, respectively. Performance evaluation was implemented to verify feasibility of the developed fine stage of the fabricated dual-servo stage. Through the step response test of the fine stage, compensation resolutions for the translational and the rotational motion were confirmed to be less than 10 nm and 1/3 arcsec, respectively. The 6-DOF motion errors in the verification test were reduced by 73% on average.
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Development of an Ultra-precision Air-bearing Stage Integrated with Real-time Motion Error Measurement and Compensation Functions Eun Young Ko, Hoon Hee Lee, Kwang Il Lee, Seung Han Yang Journal of the Korean Society for Precision Engineering.2026; 43(2): 167. CrossRef
Study on Comparison of Friction Force between Ball- and Roller-LM Guides Hyeon Jeong Ra, Dong Wook Kim, Jun Man Lee, Han Seon Ryu, Jae Han Joung, Young Hun Jeong Journal of the Korean Society for Precision Engineering.2023; 40(11): 907. CrossRef
In the framework of the 4th industrial revolution, modern machine-building rapidly converges with IOT technology. This requires very high precision machining of the parts and assemblies, such as electronics, vehicle and components, agricultural and construction machines, optical instruments, and machine tools. However, high precision machinery is quite expensive, and there exists a general need for low-cost equipment. While many researchers are working on this, their major focus is on cutting tools. This study aimed to compensate for errors and enhance machinery precision by adding a servo controller to the processing unit. Consequently, the study is on servo control and processing precision for processing utilizing ECTS (Error Compensation Tool Servo) to compensate for errors.
Recently, instrument stages using flexure guide mechanisms and piezo actuators have been widely used for an ultra-precision positioning system in various industries. Research into ultra-precision position control aiming at nanoscale position errors during stage driving is being actively conducted, as well as various studies on the motion profile adjusting the reference input. In this study, we suggested a motion profile with snap and feedforward for use with a high speed nano scanning system, as compared and analyzed with the position tracking error through feedback control, and also compared to the related feed with the forward control noted as minimized at the position error to 14.19 nm. As a result, a tracking error when applying the fourth profile with snaps to the piezoelectric stage, is obtained with an error reduction effect of about 15%, as compared to when the second profile is applied.
This study investigated the role of multi-layer lever type flexure hinges for high magnification of piezoelectric actuators and their optimal design. In order to obtain a displacement higher than 700 μm with a common PZT actuator of displacement less than 15 μm, the magnification ratio of a flexure hinge must be at least 50 or higher. Under a limited compact space, a multi-layer lever structure represents a useful alternative. Restricting the important design parameters to the number of layers and rotational stiffness of notch, the maximum required input displacement/force and the maximum output displacement were analyzed according to the number of layers. The two-layer structure was selected as the best option for large magnification ratio because the required input displacement was drastically reduced. FEM analysis revealed that the lever thickness should be larger than 12 mm to exhibit a rigid body behavior. The output displacement was 664 μm, which was less than 704 μm expected in the design stage. It might be attributed to elastic deformation of the notches of 1st and 2nd layers, which was not considered in the design stage.
The goal of this study is to develop a fast, controllable PZT-driven depth adjustment device with a flexure hinge. The device can be used to trace rapidly a flat or curved surface with several hundreds of micrometers’ variance in height. The lever type flexure hinge designed for a magnification ratio of 10 and no other axes motion has been confirmed through FEM analysis; the actual performance has been verified through static/dynamic experiments. A micro-depth control system, which is comprised of a DAQ with a LabVIEW, PZT amplifier, PZT actuator, flexure hinge, and laser displacement sensor, is implemented, and its static/dynamic characteristics of depth control is investigated with a PID gain tuned control algorithm on LabVIEW. It has been verified that the developed device can trace a micro-depth command as fast as 0.5 s to get an accurate position of 0.1 μm, even under a load of 1 N.
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Optimal Design of a Multi-Layer Lever Type Flexure Hinge for High Magnification Cui Xun, Hwa Young Kim, Jung Hwan Ahn Journal of the Korean Society for Precision Engineering.2018; 35(12): 1191. CrossRef
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