• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.973-977
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• 2004

A pneumatic cylinder used to sliding seal which seal the element one to another in relative motion. It is difficult to accuracy control because of adhesion phenomenon. To confirm this phenomenon, it is carried to friction force test and analysis for bellows type rodless cylinder. In the rodless cylinder of this type, friction force test is very important. Through the theoretical analysis of shock absorber obtained the optimal design of bellows type rodless cylinder. As the result of the friction force test, LM Guide type is suitable for work under low friction force.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권11호
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• pp.742-748
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• 2000

This paper presents a numerical method to analyze the electromechanical-coupled field in the spindle motor of a computer hard drive and investigates dynamic response due to the electromechanical excitation, i.e. unbalanced magnetic force and centrifugal force for the rotational asymmetric motor. Magnetic field is calculated from Maxwells equation and voltage equation by introducing nonlinear time-dependent finite element analysis. Mechanical motion of rotor is calculated by solving Newton-Euler equation. Electromechanical excitation and dynamic response are characterized by analyzing the free response of a rotating rotor and Fourier analysis of the excitation force and resulting vibration of a rotor. It shows that centrifugal force produces the unbalanced magnetic force even in the rotational symmetric motor. It also shows that resonance produces quite considerable vibration even when the high excitation frequency with small amplitude matches with the natural frequency of the spindle motor.

• 한국항공운항학회지
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• 제31권1호
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• pp.1-10
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• 2023

This study investigated the accident cases of the U.S. Air Force and the R.O.K. Army. It analyzed the accident factors of the unmanned aircraft system using case analysis on unmanned aircraft system operators of the R.O.K. Air Force. Following the analysis this paper suggested safety operation plans for the R.O.K. Air Force. The risk factors of unmanned aircraft system were summarized by collecting and analyzing accident cases of unmanned aircraft system by the U.S. Air Force, collecting and analyzing accident risk factors of RQ-4 operators of the R.O.K. Air Force. Through the analyzed risk factors, a safety operation plan for the semi-automatic unmanned aircraft system and the fully automatic unmanned aircraft system was presented.

• 대한인간공학회지
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• 제36권5호
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• pp.569-578
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• 2017

Objective: The purposes of this experiment are an analysis of accuracy between target force level and subjective rating for the Target Force Level and an analysis of the patterns of subjective rating depending on target force level when there is no feedback from males for analysis. Background: The study of perceived exertion about the static contraction is processed with using among the matching procedure method between contralateral limbs, Exertion vs. Borg CR-10 scale and Exertion vs. %MVC (Maximum Voluntary Contraction). However, when there is no feedback, there is lack of the study on whether the subject can distinguish the subjective rating of the force depending on the target force levels. Method: Total 30 males, healthy subjects are measured the maximum grip strength, MVC, and then, each subject is measured the subjective rating and the accuracy with the random target force level (10, 20, 30, 40, 50, 60, 70, 80, and 90% MVC). Results: In the MVC study, males exerted 256.87N (${\pm}51.33$). In the subjective rating of grip strength increased for each Target Force Level (9 levels), higher subjective rating evaluated (p<0.05). In accuracy examination between target force level and subjective rating of grip strength by each %MVC, 10, 30, 40, 50, 70, 90% target force levels showed accurate strength (p>0.05). However, at 20% target force level, the subjects evaluated less subjective rating of grip strength than the target force (Underestimation), and at 60% and 80% target force level, the subjects evaluated more subjective rating of grip strength than the target force (Overestimation) (p<0.05). Conclusion: In the experiment, the MVC showed 256.87N (${\pm}51.33$) for the male adults and as the subjective rating value increased for each Target Force Level (9 levels), higher subjective rating evaluated (p<0.05). Moreover, the results of the accuracy test between target forces and subjective rating of the subjects showed that most participants rated a fairly accurate assessment of subjective rating of grip strength for Target Force Level (9 levels), except for 20%, 60%, and 80%MVC. Application: This experimental result would be used for basic data for the subjective rating of grip strength pattern by the target force level when the voluntary muscle is contracted.

• 한국정밀공학회지
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• 제24권3호
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• pp.140-146
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• 2007

To understand adhesive phenomena, we need to get force curve between two surfaces. And it is said that high stiffness force analysis system is needed to get precise force curve and more information of the surfaces. Usually the stiffness of the force measurement system is under the order of 10N/m. The stiffer force measurement system, however, results in more information on the surface, because higher stiffness lead to the wider range of force curves, secondly because the force curve obtained through the stiffer one describes more precise relationship between relative tip-sample separation and interaction force. In this paper, considering for stiffness and resolution, the cantilever was designed and we made adhesion force measurement apparatus with high stiffness and high resolution, so we measured adhesive force between Ag-ball and wafer.

• 한국기계가공학회지
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• 제11권4호
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• pp.7-12
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• 2012

The cutting force for peripheral end-milling considering run-out property was estimated and its result was compared with that of measured one. An experimental coefficient modelling was used for the formulation of theoretical end-milling force by considering the specific cutting force coefficient. Also, the specific cutting force, that is the multiplication of specific cutting force coefficient and uncut chip thickness, was used for the prediction of end-milling force. The end-milling force mechanics with run-out was presented for the estimation of theoretical force in peripheral end-milling by considering the geometric shape of the workpiece part. As a result, the estimated end-milling force shows a good consistency with the measured one. And it can be used for the prediction of force history in end-milling with run-out which incurs different start and exit immersion angle in entering and exiting condition.

• 센서학회지
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• 제30권1호
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• pp.42-46
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• 2021

In this paper, we describe the development of a force sensor to measure the tool gripping force of the BT50 spindle. The force sensor for a BT50 must be installed inside the gripping force tester; hence, it must be of an appropriate size and have a rated capacity suitable for measuring the gripping force. So, the structure of the force sensor for BT50 was modeled, the size of the sensing part was determined by structural analysis, and the force sensor was manufactured by attaching a strain gauge. The characteristic test results of the manufactured force sensor, indicated that the nonlinearity error, hysteresis error, and reproducibility errors were each within 0.91%, Therefore it was determined that the manufactured force sensor can be used for checking the spindle tool gripping force.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1588-1593
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• 2008

This paper describes a real-time isometric pinch force prediction algorithm from surface electromyogram (sEMG) using multilayer perceptron (MLP) for human robot interactive applications. The activities of seven muscles which are observable from surface electrodes and also related to the movements of the thumb and index finger joints were recorded during pinch force experiments. For the successful implementation of the real-time prediction algorithm, an off-line analysis was performed using the recorded activities. Four muscles were selected for the force prediction by using the Fisher linear discriminant analysis among seven muscles, and the four muscle activities provided effective information for mapping sEMG to the pinch force. The MLP structure was designed to make training efficient and to avoid both under- and over-fitting problems. The pinch force prediction algorithm was tested on five volunteers and the results were evaluated using two criteria: normalized root mean squared error (NRMSE) and correlation (CORR). The training time for the subjects was only 2 min 29 sec, but the prediction results were successful with NRMSE = 0.112 ${\pm}$ 0.082 and CORR = 0.932 ${\pm}$ 0.058. These results imply that the proposed algorithm is useful to measure the produced pinch force without force sensors in real-time. The possible applications include controlling bionic finger robot systems to overcome finger paralysis or amputation.

• Structural Engineering and Mechanics
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• 제65권3호
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• pp.263-274
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• 2018

In this study, we propose a frequency domain spectral element method (SEM) for the vibration analysis of a multi-span beam subjected to a moving point force. This study is an extension of the authors' previous study for a single-span beam subjected to a moving point force, where the two-element model-based SEM was applied. In this study, each span of a multi-span beam is represented by the Timoshenko beam model and the moving point force is transformed into the frequency domain as a series of each stationary point force distributed on the multi-span beam. The span at which a stationary point force is located is represented by two-element model, but all other spans are represented by one-element models. The vibration responses to a moving point force are obtained by superposing all individual vibration responses generated by each stationary point force. The high accuracy and computational efficiency of the proposed SEM are verified by comparing the solutions by SEM with exact analytical solutions by the integral transform method (ITM) as well as the solutions by the finite element method (FEM).

• 한국정밀공학회지
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• 제32권11호
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• pp.945-952
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• 2015

In drawing sheet metal, the blank holding force is applied to prevent wrinkling of the product and to add a tensile stress to the material for the plastic deformation. Applying an inappropriate blank holding force can cause wrinkling or fracture. Therefore, it is important to determine the appropriate blank holding force. Recent developments of the servo cushion open up the possibility to reduce the possibility of fracture and wrinkling by controlling the blank holding force along the stroke. In this study, a method is presented to find the optimal variable blank holding force curve, which uses statistical analysis with consideration of the nonlinear deformation path. The optimal blank holding force curve was numerically and experimentally applied to door inner parts. Consequently, it was shown that the application of the variable blank holding force curve to door inner parts could effectively reduce the possibility of fracture and wrinkling.