The Levitation Mass Method

Yusaku Fujii 한국정밀공학회 2008 International Journal of Precision Engineering and Vol.9 No.3

The present status and future prospects of the levitation mass method(LMM), a technique for precision mass and force measurement, are reviewed. In the LMM, the inertial force of a mass levitated using a pneumatic linear bearing is used as the reference force applied to the objects being tested, such as force transducers. materials, or structures. The inertial force of the levitated mass is measured using an optical interferometer. We have modified this technique for dynamic force calibration of impact, oscillation, and step loads. We have also applied the LMM to material testing. providing methods for evaluating material viscoelasticity under an oscillating or impact load. evaluating material friction, evaluating the biomechanics of a human hand, and generating and measuring micro-Newton-level forces.

The Levitation Mass Method: A Precision Mass and Force Measurement Technique

Fujii, Yusaku Korean Society for Precision Engineering 2008 International Journal of Precision Engineering and Vol.9 No.3

The present status and future prospects of the levitation mass method (LMM), a technique for precision mass and force measurement, are reviewed. In the LMM, the inertial force of a mass levitated using a pneumatic linear bearing is used as the reference force applied to the objects being tested, such as force transducers, materials, or structures. The inertial force of the levitated mass is measured using an optical interferometer. We have modified this technique for dynamic force calibration of impact, oscillation, and step loads. We have also applied the LMM to material testing, providing methods for evaluating material viscoelasticity under an oscillating or impact load, evaluating material friction, evaluating the biomechanics of a human hand, and generating and measuring micro-Newton-level forces.

다축 힘/모멘트 센서 교정기의 개발 및 불확도 평가

김갑순(Gab-Soon Kim),신희준(Hyi-Jun Shin),김현민(Hyeon-Min Kim) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

This paper describes the development of multi-axis force/moment sensor calibration system and its uncertainty evaluation. This sensor, which has maximum capacities of 2000N in forces and 400Nm in moments, can generate the continuous forces (±Fx, ±Fy and ±Fz) and moments (±Mx, ±My and ±Mz.). In order to be used multi-axis force/moment sensors in many kinds of industries, they are carried out the characteristic test or the calibration with the system that can generate the forces and the moments. The developed calibrating systems are the disadvantages of the low capacity, the generation of step force and moment with weights, the high coasts in manufacture and so on. In this paper, the multi-axis force/moment sensor calibration system that can generate the continuous forces and moments was developed. Its maximum capacities are 2000N in forces and 400Nm in moments. And the system was evaluated in the expanded relative uncertainty. They were ±0.0004 in forces ±Fx , ±Fy, ±Fz, and ±0.0004 in moments ±Mx, ±My, ±Mz.

Uncertainty Evaluation of a multi-axis Force/Moment Sensor

Kim, Gab-Soon Korean Society for Precision Engineering 2002 International Journal of the Korean Society of Pre Vol.3 No.3

This paper describes the methods for calibration and evaluation of the relative expanded uncertainty of a multi-axis force/moment sensor. In order to use the sensor in the industry, it should be calibrated and its relative expanded uncertainty should be also evaluated. At present, the confidence of the sensor is shown with only interference error. However, it is not accurate, because the calibrated multi-axis force/moment sensor has an interference error as well as a reproducibility error of the sensor, etc. In this paper, the methods fur calibration and for evaluation of the relative expanded uncertainty of a multi-axis force/moment sensor are newly proposed. Also, a six-axis force/moment sensor is calibrated with the proposed calibration method and the relative expanded uncertainty is evaluated using the proposed uncertainty evaluation method and the calibration results. It is thought that the methods fur calibration and evaluation of the uncertainty can be usually used for calibration and evaluation of the uncertainty of the multi-axis force/moment sensor.

A fingertip force sensor for underwater dexterous hand

Hua Wang 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.2

In order to safely grasp an unknown object and accurately perceive its position in the fingers, a finger-tip force sensor which can detect the force and position simultaneously was developed for the underwater dexterous hand. This paper introduced the finger-tip force sensor model which was built by a cylinder elastic body. The principle of force measuring was analyzed theoretically, which proved the reasonableness of the structure and the equation was inferred for measuring force. Because of nonlinear and coupling, a feedforward artificial neural network was employed to calibrate the sensor utilizing the data which were obtained from the tests. The characteristic tests of the sensor showed the maximum error was below 6% in force measurements and the maximum position error was Ф1.6 mm. Then, the application experiments were carried out and the results showed the finger system can track the expectation of force trajectory, which indicated measurement accuracy of the sensor met the demands of research on the underwater dexterous hand. What’s more, the sensor structure can compensate the effect of water pressure. So the sensor can be integrated into the finger of the underwater manipulator and used under the water.

Towards optimal slip force and stiffness distribution in designing friction dampers

Pourya Sam-Daliri,Seyed Mehdi Zahrai,Hamid Dahaghin 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.79 No.3

The considerable capacity of friction dampers in energy dissipation makes them a good choice for vibration control of structures. The slip force of friction dampers and also the stiffness of the corresponding bracing system are the major parameters that must be chosen carefully in the design procedure of these dampers. This paper presents an innovative approach to determine these parameters using the data extracted from a series of analyses conducted on three different structures, subjected to five different earthquake records. For this purpose, 900 time-history analyses are conducted. The responses extracted from these analyses are used to compare the effect of different slip forces and to choose the optimum case. Also, a stiffness calibration method is proposed to determine the bracing system stiffness. Finally, two multi-functional optimization methods are introduced to find a single value for optimal slip force. It is shown that between 56 to 74% of the input energy can be dissipated by friction dampers, using this design approach. Additionally, up to 20, 45, 64, and 62% reductions in maximum displacement, velocity, acceleration, and base shear are achieved respectively for the structures studied in this research.

나노 힘 측정 및 표준

김민석(M. S. Kim),박연규(Y. K. Park),최재혁(J. H. Choi),김종호(J. H. Kim),강대임(D. I. Kang) 한국정밀공학회 2005 한국정밀공학회 학술발표대회 논문집 Vol.2005 No.10월

Small force measurements ranging from 1 pN to 100 μN, we call it Nano Force, become the questions of common interests of biomechanics, nanomechanics, material researches, and so on. However, unfortunately, quantitative and accurate force measurements have not been taken so far. This is because there are no traceable force standards and a calibration scheme. This paper introduces a quantitative force metrology, which provides traceable link to SI (International Systems of Units). We realize SI traceable force ranging from 1 nN to 100 μN using an electrostatic balance and disseminate it through transfer standards, which are self-sensing cantilevers that have integrated piezoresistive strain gages. We have been built a prototype electrostatic balance and Nano Force Calibrator (NFC), which is an AFM cantilever calibration system. As a first experiment, we calibrated normal spring constants of commercial AFM cantilevers using NFC. Calibration results show that the spring constants of them are quite differ from each other and nominal values provided by a manufacturer (up to 240 % deviation).

Improved lateral force calibration based on the angle conversion factor in atomic force microscopy

CHOI, DUKHYUN,HWANG, WOONBONG,YOON, EUISUNG Blackwell Scientific 2007 Journal of Microscopy Vol.228 No.2

<P>Summary</P><P>A novel calibration method is proposed for determining lateral forces in atomic force microscopy (AFM), by introducing an angle conversion factor, which is defined as the ratio of the twist angle of a cantilever to the corresponding lateral signal. This factor greatly simplifies the calibration procedures. Once the angle conversion factor is determined in AFM, the lateral force calibration factors of any rectangular cantilever can be obtained by simple computation without further experiments. To determine the angle conversion factor, this study focuses on the determination of the twist angle of a cantilever during lateral force calibration in AFM. Since the twist angle of a cantilever cannot be directly measured in AFM, the angles are obtained by means of the moment balance equations between a rectangular AFM cantilever and a simple commercially available step grating. To eliminate the effect of the adhesive force, the gradients of the lateral signals and the twist angles as a function of normal force are used in calculating the angle conversion factor. To verify reliability and reproducibility of the method, two step gratings with different heights and two different rectangular cantilevers were used in lateral force calibration in AFM. The results showed good agreement, to within 10%. This method was validated by comparing the coefficient of friction of mica so determined with values in the literature.</P>

A new method for lateral force calibration in Atomic Force Microscopy

Fei Wang,Hong Joon Kim,Eui-Sung Yoon,Hosung Kong 한국트라이볼로지학회 2005 한국트라이볼로지학회 학술대회 Vol.2005 No.6

A new calibration method for quantitative lateral force measurement in atomic force microscope (AFM) is presented to measure lateral force accurately in nanotribology. The effect of contact stiffness on the conversion factor between lateral force and lateral signal is analyzed, and a new conversion factor involving a contact factor in the calibration procedure is proposed. The contact factor is affected by tip and cantilever stiffness and contact stiffness. Conventional conversion factor is determined experimentally and modified to involve the contact factor. The calibration results show that the dependency of the conventional conversion factor on the normal load and sample materials is eliminated by using the proposed method.

AFM을 이용한 나노스케일 힘의 정량적 측정

정구현(Koo-Hyun Chung) 한국트라이볼로지학회 2012 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.28 No.2

Atomic force microscopy (AFM) has been widely utilized as a versatile tool not only for imaging surfaces but also for understanding nano-scale interfacial phenomena. By measuring the responses of the photo detector due to bending and torsion of the cantilever, which are caused by the interactions between the probe and the sample surface, various interfacial phenomena and properties can be explored. One of the challenges faced by AFM researchers originates in the physics of measuring the small forces that act between the probe of a force sensing cantilever and the sample. To understand the interactions between the probe and the sample quantitatively, the force calibration is essential. In this work, the procedures used to calibrate AFM instrumentation for nano-scale force measurement in normal and lateral directions are reviewed.