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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society for Precision Engineering
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Journal DOI :
Korean Society of Precision Engineering
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Volume & Issues
Volume 28, Issue 12 - Dec 2011
Volume 28, Issue 11 - Nov 2011
Volume 28, Issue 10 - Oct 2011
Volume 28, Issue 9 - Sep 2011
Volume 28, Issue 8 - Aug 2011
Volume 28, Issue 7 - Jul 2011
Volume 28, Issue 6 - Jun 2011
Volume 28, Issue 5 - May 2011
Volume 28, Issue 4 - Apr 2011
Volume 28, Issue 3 - Mar 2011
Volume 28, Issue 2 - Feb 2011
Volume 28, Issue 1 - Jan 2011
Selecting the target year
Effect of Multi-Channel Vibration Stimulation on Somatosensory Sensibility
Bae, Tae-Soo ; Kim, Hyung-Jae ; Kim, Sol-Bi ; Chang, Yun-Hee ; Kim, Shin-Ki ; Mun, Mu-Seong ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 651~656
Although prosthetic training was received, most of amputees mainly depend on visual feedback to use prostheses, not on cutaneous and proprioceptive sensibility. Our objective of this study was to determine if there are changes in the somatosensory sensibility of amputees compared to non-amputees using multi-channel vibration stimulation system. One transradial amputees and ten non-amputees were involved. To investigate changes of residual somatosensory sensibility at stump, we set up custom-made vibration stimulation system including eight actuators (4 medial and 4 lateral) and GUI-based acquisition system. The results showed that there was similar pattern of subjective response at most of channels among group as stimulation increases. However, amputees' subjective response at channel 8 for 238Hz vibration was more sensitive than that of healthy persons. With respect to channels, response at channel 4 (medial) corresponding region to flexor carpi ulnaris for transradial amputees was most sensitive than other channels. In addition, sensitivity of four medial channels was on average about 0.5 scale than that of four lateral channels. Somatosensory sensibility was amputee, women, and men in sensibility order.
Dynamic Analysis of Finger Joint Torque for Tip Pinch Task
Kim, Yoon-Jeong ; Jeong, Gwang-Hun ; Rhee, Kye-Han ; Lee, Soo-Jin ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 657~682
This paper presents the dynamic analysis on the joint torque of a finger for the tip pinch task. The dynamic model on finger movement was developed in order to predict the joint torques of an index finger, and the finger was assumed as a three-link planar manipulator. Analysis of the model revealed that the joint stiffness was one of the most important parameters affecting the joint torque. The stiffness of the finger joint was experimentally measured, and it was used in analyzing the finger joint torque required for performing the tip pinch task. The obtained joint torque for the tip pinch task will be used as the design requirements of the finger exoskeletal orthosis actuated by the polymer actuator whose allowable torque limit is relatively low compared to that of a mechanical actuator.
Estimation of Shoulder Flexion Torque and Angle from Surface Electromyography for Physical Human-Machine Interaction
Park, Ki-Han ; Lee, Dong-Ju ; Kim, Jung ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 663~669
This paper examines methods to estimate torque and angle in shoulder flexion from surface electromyography(sEMG) signals for intuitive and delicate control of robotic assistance device. Five muscles on the upper arm, three for shoulder flexion and two for shoulder extension, were used to offer favorable sEMG recording conditions in the estimation. The methods tested were the mean absolute value (MAV) with linear regression and the artificial neural network (ANN) method. An optimal condition was sought by varying combination of muscles used and the parameters in each method. The estimation performance was evaluated using the correlation values and normalized root mean square error values. In addition, we discussed their possible use as an estimation of motion intent of a user or as a command input in a physical human-machine interaction system.
Joint Torque Estimation of Elbow joint using Neural Network Back Propagation Theory
Jang, Hye-Youn ; Kim, Wan-Soo ; Han, Jung-Soo ; Han, Chang-Soo ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 670~677
This study is to estimate the joint torques without torque sensor using the EMG (Electromyogram) signal of agonist/antagonist muscle with Neural Network Back Propagation Algorithm during the elbow motion. Command Signal can be guessed by EMG signal. But it cannot calculate the joint torque. There are many kinds of field utilizing Back Propagation Learning Method. It is generally used as a virtual sensor estimated physical information in the system functioning through the sensor. In this study applied the algorithm to obtain the virtual senor values estimated joint torque. During various elbow movement (Biceps isometric contraction, Biceps/Triceps Concentric Contraction (isotonic), Biceps/Triceps Concentric Contraction/Eccentric Contraction (isokinetic)), exact joint torque was measured by KINCOM equipment. It is input to the (BP)algorithm with EMG signal simultaneously and have trained in a variety of situations. As a result, Only using the EMG sensor, this study distinguished a variety of elbow motion and verified a virtual torque value which is approximately(about 90%) the same as joint torque measured by KINCOM equipment.
Linear Motion Perception under Additional Somatosensation
Yi, Yong-Woo ; Park, Su-Kyung ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 678~686
When one sensor cannot provide information by sensory deficit or loss, the sensory information can be provided by substituting other sensors for the defected sensor. This sensory substation might be influence on the deteriorated motion perception that consists of multi-sensory information such as visual, vestibular and somatosensory information. In this study, to investigate whether the additional sensation by sensory substitution could be integrated into the motion perception, we examined the effect of substituted postural sway sensation on the directional perception of body movement. Deteriorated motion perception by the reduced plantar sensation was enhanced under sensory substitution condition that provided the body sway information as the plantar vibratory stimulus. These results imply that the additional sensation might be integrated into and improve the motion perception.
Vertical Limb Stiffness Increased with Gait Speed in the Elderly
Hong, Hyun-Hwa ; Park, Su-Kyung ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 687~693
Spring-mass models have been widely accepted to explain the basic dynamics of human gait. Researchers found that the leg stiffness increased with gait speed to increase energy efficiency. However, the difference of leg stiffness change with gait speed between the young and the elderly has not been verified yet. In this study, we calculated the lower limb stiffness of the elderly using walking model with an axial spring. Vertical stiffness was defined as the ratio of the vertical force change to the vertical displacement change. Seven young and eight elderly subjects participated to the test. The subjects walked on a 12 meter long, 1 meter wide walkway at four different gait speeds, ranging from their self-selected speed to maximum speed randomly. Kinetic and kinematic data were collected using three force plates and motion capture cameras, respectively. The vertical stiffness of the two groups increased as a function of walking speed. Maximum walking speed of the elderly was slower than that of the young, yet the walking speed correlated well with the optimal stiffness that maximizes propulsion energy in both groups. The results may imply that human may use apparent limb stiffness to optimize energy based on spring-like leg mechanics.
Fabrication of PCD Micro Tool and its Hybrid Micro Machining
Doan, Cao Xuan ; Kim, Bo-Hyun ; Chung, Do-Kwan ; Chu, Chong-Nam ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 694~700
Since polycrystalline diamond (PCD) has high hardness like diamond, it has been used as tool material for lathe and milling of non-ferrite material. A micro tool fabricated from PCD material can be used for micro machining of hard material such as tungsten carbide, glass, and ceramics. In this paper, micro PCD tools were fabricated by micro EDM (electrical discharge machining) and used for micro grinding of glass. Craters generated on the tool surface by EDM spark work as like grits in grinding process. The effects of tool shapes, tool roughness and PCD grain size were investigated. Also studied was a hybrid process combining electrochemical discharge machining (ECDM) and micro grinding for micro-structuring of glass.
A Study on the Characteristics of Internal-Face Magnetic Abrasive Finishing for Titanium Pipe
Li, Li-Hai ; Mun, Sang-Don ; Kim, Young-Whan ; Park, Won-Ki ; Yang, Gyun-Eui ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 701~708
Although Titanium material has superior properties, it belongs to difficult-to-machine materials. The present research applies magnetic abrasive finishing to precision machining of internal-face of titanium pipes, and analyzed & assessed the influence of grinding conditions on magnetic abrasive effects through the removed amount and surface roughness of materials. There was the influence on grinding properties according to change of rotational speed, a total input of mixed powder and an input of grinding liquid, and when the total input, rotational speed and ratio of electrolytic iron versus magnetic abrasives are 8g and 1000rpm, it was most advantageous in aspects of surface roughness and material removal amount, and the grinding liquid remarkably improved the surface roughness and material removal amount only with addition of trace amounts of light oil rather than dry machining conditions. And a result of considering the influence on grinding properties by using an inert gas (Argon gas) for improving grinding properties of the internal-face of titanium pipe, the present research has obtained improvement effects in the removal amount and surface roughness through utilization of an inert gas.
The Vibration Measurement of Boring Process by Using the Optical Fiber Sensor at inside of Boring Bar
Song, Doo-Sang ; Hong, Jun-Hee ; Guo, Yang-Yang ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 709~715
Chattering in cutting operations are usually a cumbersome part of the manufacturing process in mechanical. Particular, machining performance such as that of the boring process is limited by cutting condition at the movable components. Among various sources of chatter vibration, detrimental point in cutting condition is found a mechanical condition on overhang. It limits cutting speed, depth, surface roughness and tool wear failure as result because the all properties are varying with the metal removal process. In this case, we have to observe the resonance frequencies of a boring bar for continuous cutting. In the established research, boring bar vibration of cutting system has been measured with the aid of accelerometer. However, the inherent parameters of internal turning operations are severely limit for the real time monitoring on accelerometers. At this point, this paper is proposed other method for real time monitoring during continuous cutting with optical fiber at the inside of boring bar. This method has been used a plastic fiber in the special jig on boring bar by based on experimental modal analysis. In this study, improvement of monitoring system on continuous internal cutting was attempted using optical fiber sensor of inside type because usually chattering is investigated experimentally measuring the variation in chip thickness. It is demonstrated that the optical fiber sensor is possibility to measure of chattering with real time in boring process.
A Study on the Design of High-Voltage Connector for Green Car using FEM
Kim, Sung-Woong ; Choi, Jung-Wook ; Kim, Hyeung-Rak ; Kwon, Young-Seok ; Kang, Nam-Jin ; Choi, Kyung-Seok ; Park, Hyung-Pil ; Cha, Baeg-Soon ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 716~723
The battery capacity of electric/hybrid vehicle is much larger than present automobile. For that reason, the connector of Green Car should be designed to transmit the high-electric voltage. In addition, the electromagnetic wave should be shielded to protect communication and signal circuits. In this study, shielding performance of the connector was analyzed through electromagnetic shield analysis, and a connector of Green Car was designed using thermoelectrical analysis, which is capable of transmitting the high-electric power. In the design of connector structure, the improved stability and workability was considered.
A Study on the Reduction of Dew Generation on a Surface Using Induced Heat from Room Temperature
Kim, Seong-Jin ; Kang, Seok-Hoon ; Park, Ki-Hong ; Yoo, Won-Sul ; Park, Sang-Hu ; Choi, Ho-Jin ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 724~731
Dew generation on an outer surface is considered as an important issue to be settled in the field of home appliances. In the case of a refrigerator that is subject to the dew generation problem on the surface of an outer-door of refrigeration thread, and so as to solve this problem, the electric heater is generally used for drying the dew. However, the heater inevitably requires electrical power consumption that is one of critical issues on the refrigerator. In this study, to prevent dew generation without the heater, a method of using induced heat from room temperature was proposed. In edge sides of a door, high conductive plates are installed and received the heat from outside that is relatively high temperature, and the heat is transferred onto dew generation region. Using prototypes, performance test was conducted under a certain temperature and humidity condition. The experimental results show that the surface temperature on the dew generation region was increased about
without use of any heater.
Stress Analysis and Design Modification of the Planetary Gear Reducer of an In-wheel System
Jung, Sung-Pil ; Chung, Won-Sun ; Park, Tae-Won ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 732~737
The planetary gear reducer becomes more and more widely used in machine industries. The planetary gear reducer has a significant role to transmit power to wheel & tire module in the In-wheel system. Thus, the planetary gear reducer should have strong stiffness and durability. In this paper, the contact and bending stresses at the tooth of the planetary gear reducer are analyzed using MASTA, a commercial gear design and analysis software. Stress distribution at the tooth face of the sun, planetary and annulus gears are obtained using the finite element method. The design modification is performed using the response surface method. The usefulness of the design modification and optimization method presented in this paper is verified by comparing the maximum stresses of the original and optimized planetary gear tooth.
Development of Crack Detecting Method at Steam Turbine Blade Root Finger using Ultrasonic Test
Yun, Wan-No ; Kim, Jun-Sung ; Kang, Myung-Soo ; Kim, Duk-Nam ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 738~744
The reliability of blade root fixing section is required to endure the centrifugal force and vibration stress for the last stage blade of steam turbine in thermal power plant. Most of the domestic steam turbine last stage blades have finger type roots. The finger type blade is very complex, so the inspection had been performed only on the exposed fixing pin cross-section area due to the difficulty of inspection. But the centrifugal force and vibration stress are also applied at the blade root finger and the crack generates, so the inspection method for finger section is necessary. For the inspection of root finger, inspection points were decided by simulating ultra-sonic path with 3D modeling, curve-shape probe and fixing jig were invented, and the characteristics analysis method of ultrasonic reflection signal and defect signal disposition method were invented. This invented method was actually executed at site and prevented the blade liberation failure by detecting the cracks at the fingers. Also, the same type blades of the other turbines were inspected periodically and the reliability of the turbine increased.
A Computational Investigation on Airflow Structures Inside a Ball Bearing at High-Speed Rotation
Kim, Dong-Joo ; Oh, Il-Suk ; Hong, Seong-Wook ; Kim, Kyoung-Jin ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 745~750
In a hope to better understand the flow and convective heat transfer characteristics inside a ball bearing, air flow between the rolling elements and raceways at high speed bearing rotation is numerically investigated using a simplified inner geometry of bearing and a CFD technique. Flow simulation results reveal the pressure distribution of airflow and the shear stress distribution on the ball surface, of which nonuniformity becomes significant with the increasing rotational speed. Also, the local point of maximum shear stress coincides with the stagnation flow area on the surface of rolling elements. A complex pattern of three-dimensional vortex structures is found in the air flow due to the relative motion of bearing elements and three different types of vortex pairs exist around the rotating and orbiting rolling elements.
A Study on Design of an Effective Micromixer using Horizontal and Vertical Multi-mixing (HVM) Flow Motion
Yoo, Won-Sui ; Kim, Sung-Jin ; Kang, Seok-Hoon ; Kim, Pan-Guen ; Park, Sang-Hu ;
Journal of the Korean Society for Precision Engineering, volume 28, issue 6, 2011, Pages 751~757
Subminiature devices such as Lab-on-a-chip and p-TAS(Micro Total Analysis System) have been intensively studied in biotechnology and chemistry, In many cases, a micromixer was widely used to mix different solutions for synthesizing novel materials. However, in microfluidic system, there is generally a laminar flow under very small Reynolds number so it is difficult to mix each solution perfectly. To settle this problem, we propose a new mixing mechanism which generates a horizontal and vertical multi-mixing (HVM) flow for effective mixing within a short mixing section. We evaluated the proposed mechanism using CFD analysis, and the results showed that the HVM mechanism had a relative high-effectiveness comparing to the existing methods.