• Applied Science and Convergence Technology
• /
• v.23 no.2
• /
• pp.97-102
• /
• 2014

A vacuum chamber for a commercial atomic force microscope (AFM) is designed and fabricated. Only minimal modifications were made to an existing microscope in an effort to work in a vacuum environment, while most of the available AFM functionalities were kept intact. The optical alignment needed for proper AFM operations including a SLD (superluminescent diode) and a photodiode can be made externally without breaking the vacuum. A vacuum level of $5{\times}10^{-3}$ torr was achieved with a mechanical pump. An enhancement of the quality factor was observed along with a shift in the resonance frequency of a non-contact-mode cantilever in a vacuum. Topographical data of a calibration sample were also obtained in air and in a low vacuum using the non-contact mode and the results were compared.

• Journal of the Korean Society for Precision Engineering
• /
• v.12 no.12
• /
• pp.64-71
• /
• 1995

This investigation evaluates dynamic fracture characteristics of two alloy steels (STD-11 and STS-3) and a gray cast iron (GC-30). The dynamic fracture toughness of crack initiation and some of the dynamic fracturing characteristics were evaluated by using the instrumented Charpy impact testing procedures. It was found from experimental results for three kinds of materials that inertia force is directly proportional to impact velocity. The duration time of inertia force was found to be constant regardless of impact velocities in steel specimens.

• 제어로봇시스템학회:학술대회논문집
• /
• 2003.10a
• /
• pp.2445-2450
• /
• 2003

Recently, biological technology industry shows great development. Instruments and systems related biological technology have been developed actively. In this paper, we developed a new micro end-effector for biological cell manipulation. The existing micro end-effector for biological cell manipulation has not any force sensing mechanism. Usually, excessive contact force occurring when the end-effector and a cell collide might make a damage on the cell. However, unfortunately, user can not notice the condition in case of using the existing end-effector. In order to overcome we proposed the improved micro end-effector having a force sensing mechanism. This paper presents the design concepts of the new micro end-effector. We carried out calibration of the force sensor and tested the performance of the proposed micro end-effector. Through a series of experiments the new micro end-effector shows the possibility of application for precision biological cell manipulation such as DNA operation

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.20 no.7
• /
• pp.2213-2222
• /
• 1996

This paper presents the design process and evaluaation results of a two-axis force transducer for measuring flange reaction forces. A double-cantilever beam structure is used as a sensing element, and its optimal configuration is determined based on the derived strain equations to maximize the sensitivity and minimize the regid body displacements. To reduce the coupling errors between two-axis forces, strain distributions by finite elemetns analysis are utilized and the Wheaststone bridge cricuits composed of strain gages are built such that the output voltage should be zero, although strains of four strain gages are not zero. Calibration test shows that the two-azxis force transducer developed in this paper is useful in measuring flange reaction forces within the coupling error of 5.53%.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.2
• /
• pp.170-177
• /
• 2012

A force/torque sensor using carbon fiber plate was designed and developed to make the sensor be able to measure a wide range of multi degree of force and torque. Using carbon fiber plate of 0.3 mm thickness, the sensor was designed and developed, which has a ${\mu}N$ level order of resolution and about 0.01 N ~ 390 N of wide measurement range. The elastic deformation part has a tripod plate structure and strain gauges are attached on the part to detect the force/torque. The coefficient of determination for the sensor is over 0.955 by the calibration experiment so that the linearity of the sensor is confirmed to be good. Also, experiments on applying 0.005 ~ 40 kg (0.05 ~ 390 N) to each axis were implemented and the sensor is proved to be safe under a high load. Finally, to verify the function calculating the direction of load vector, the directions of various load vectors which have the same magnitude but different directions and the directions of the calculated load vectors are compared and analyzed to accord well.

• Structural Engineering and Mechanics
• /
• v.46 no.5
• /
• pp.673-693
• /
• 2013

This paper presents a systematic design and training procedure for the feed-forward back-propagation neural network (NN) modeling of both forward and inverse behavior of a rotary magnetorheological (MR) damper based on experimental data. For the forward damper model, with damper force as output, an optimization procedure demonstrates accurate training of the NN architecture with only current and velocity as input states. For the inverse damper model, with current as output, the absolute value of velocity and force are used as input states to avoid negative current spikes when tracking a desired damper force. The forward and inverse damper models are trained and validated experimentally, combining a limited number of harmonic displacement records, and constant and half-sinusoidal current records. In general the validation shows accurate results for both forward and inverse damper models, where the observed modeling errors for the inverse model can be related to knocking effects in the measured force due to the bearing plays between hydraulic piston and MR damper rod. Finally, the validated models are used to emulate pure viscous damping. Comparison of numerical and experimental results demonstrates good agreement in the post-yield region of the MR damper, while the main error of the inverse NN occurs in the pre-yield region where the inverse NN overestimates the current to track the desired viscous force.

• Journal of the Korean Geotechnical Society
• /
• v.40 no.2
• /
• pp.115-123
• /
• 2024

Stress is an invisible physical quantity, necessitating the use of earth pressure cells for its measurement within theground. Traditional strain-gauge type earth pressure cells, due to their rigidity, can distribute stress within the ground and subsequently affect the accuracy of earth pressure measurements. In contrast, force sensing resistors are thin and flexible, enabling the minimization of stress disturbance when measuring stress within the ground. This study developed a system that utilizes force sensing resistors to measure ground stress. It involved constructing a soil chamber for calibrating the force sensing resistors, assessing the variability of measurements from resistors embedded in sand ground, and verifying the attachment of pucks to the sensing area of the resistors.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.6 s.171
• /
• pp.213-221
• /
• 2005

An insole type local shear force measurement system was developed and local shear stresses in the foot were measured during level walking. The shear force transducer based on the magneto-resistive principle, was a rigid 3-layer circular disc. Sensor calibrations with a specially designed calibration device showed that it provided relatively linear sensor outputs. Shear transducers were mounted on the locations of four metatarsal heads and heel in the insole. Sensor outputs were amplified, decorded in the bluetooth transmission part and then transferred to PC. In order to evaluate the developed system, both shear and plantar pressure measurements, synchronized with the three-dimensional motion analysis system, were performed on twelve young healthy male subjects, walking at their comfortable speeds. The maximum peak pressure during gait was 5.00kPa/B.W at the heel. The time when large local shear stresses were acted correlated well with the time of fast COP movements. The anteroposterior shear was dominant near the COP trajectory, but the mediolateral shear was noted away from the COP trajectory. The vector sum of shear stresses revealed a strong correlation with COP movement velocity. The present study will be helpful to select the material and to design of foot orthoses and orthopedic shoes for diabetic neuropathy or Hansen disease.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.10
• /
• pp.923-929
• /
• 2004

In this research, Forced Vibration Test(FVT) on a cable stayed bridge was conducted to examine the validity of the frequency domain pattern recognition method using signal anomaly index and artificial neuralnetwork. 7he considering structure, Samchunpo Bridge, located in Sachun-Shi, Kyungsangnam-Do, is a cable stayed bridge with the 436 meter span. The excitation force was induced by a sudden braking of a fully loaded truck. and vortical acceleration signals were acquired at 14 points. The initial 2-dimensional FE-model was developed from the design documents to prepare the training sets for the artificial neural network, and then the model calibration was performed with the field test data. As a result of the model calibration, we obtained the FFT spectrums from the model simulation, which was similar to those from the vibration test. These tests and the simulation data will be used for the structural identification using arbitrarily added masses to the bridge.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.619-623
• /
• 2003

In this research, Forced Vibration Test(FVT) on a cable stayed bridge was conducted to examine the validity of the frequency domain pattern recognition method using signal anomaly index and artificial neural network. The considering structure, Samchunpo Bridge, located in Sachun-Shi, Kyungsangnam-Do, is a cable stayed bridge with the 436 meter span. The excitation force was induced by a sudden braking of a fully loaded truck, and vertical acceleration signals were acquired at 14 points. The initial 2-dimensional FE-model was developed from the design documents to prepare the training sets for the artificial neural network, and then the model calibration was performed with the field test data. As a result of the model calibration, we obtained the FFT spectrums from the model simulation, which was similar to those from the vibration test. These tests and the simulation data will be used fur the structural identification using arbitrarily added masses to the bridge.