• Journal of Biosystems Engineering
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• v.33 no.4
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• pp.224-229
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• 2008

This study was aimed to minimize the impact force and vibration transmitted to the transporting materials from the trailer and wheel shaft by installing the leaf spring suspension device at the space between the wheel shaft and frame of power tiller trailer. The developed trailer equipped with leaf spring suspension device was compared to the existing trailer without suspension device, in order to identify the vibration absorption effect of the leaf spring. The results of this study could be summarized as follows; (1) The length and the maximum bending amount of the leaf spring were designed as 1,000 mm and 42 mm, respectively, considering the possible space for installing at below the trailer. When 4 leaf springs were installed on both wheel shafts, the allowable maximum load was identified as 9,418 N. (2) The average vibration accelerations for the frequency less than 20 Hz, where the severe transporting loss could be represented, were $0.017\;m/s^2$ and $0.133\;m/s^2$ for the developed and the existing trailer, respectively, showing the vibration absorption effect of about 87%. And the average vibration accelerations on the driver's seat for the frequency less than 20 Hz were $0.01\;m/s^2$ and $0.20\;m/s^2$ for the developed and the existing trailer, respectively, which showed the similar vibration absorption effect. (3) The change of the average vibration accelerations for the frequency from 20 Hz to 80 Hz showed the similar tendency with the result for the frequency less than 20 Hz, but the effect for developed trailer was reduced slightly. And the effect of vibration absorption for the above 80 Hz was reduced highly. However, by installing the leaf spring suspension device at the trailer, the low frequency below 40 Hz, which could affect on transporting loss severely, could be reduced highly. (4) The maximum vibration acceleration for the frequency less than 20 Hz were $0.027\;m/s^2$ and $1.267\;m/s^2$ for the developed and the existing trailer, respectively. And the change of maximum acceleration between 20 Hz and 120 Hz was showed similar tendency with the result for the frequency less than 20 Hz, but the width of change was reduced highly.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.9
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• pp.129-134
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• 2016

This paper studies the high frequency PWM (pulse width modulation) driving technique to increase an optical efficiency and to prevent an optical color quenching of blue laser for head up display on vehicles using digital micro mirror device (DMD) panel and yellow phosphor wheel. The proposed approach adaptively drives the current pulse width modulated signals of high optical power of blue laser to increase the lifetime and to decrease the stem temperature of laser. This method stabilizes the temperature of laser according to the driving environment and the forward current capacity. By the proposed method, the brightness of blue laser is improved by about 37% compared to the continuous waveform current driving method.

• Design & Manufacturing
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• v.18 no.2
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• pp.1-8
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• 2024

Unlike the roll-to-roll process that uses a steel roll and a nip roll, a vacuum roll can hold and transfer a thin film using a single roll. To precisely manufacture a vacuum roll, a thin outer cylinder must be machined, which is assembled on the outside of the roll and contacts the film via vacuum pressure. In this study, the effects of jaw width and chucking force on the deformation of the outer cylinder during the turning process were investigated using analysis, and a precision machining and burr removal process was developed. The deformation of the outer cylinder decreased almost linearly with increasing jaw width and increased with higher chucking force and larger cylinder diameter. Additionally, the deflection due to the weight of the outer cylinder was approximately three times greater than that caused by film tension. For the machined outer cylinder, a burr removal experiment was conducted, and concentricity and cylindricity were measured. Using a device that removes burrs by rotating a wheel connected to the main shaft at high speed, it was found that burrs generated on the inner diameter could be removed very efficiently. On the vacuum side, the concentricity errors of the inner and outer diameters were 0.015 mm and 0.014 mm, respectively, and on the opposite side, they were 0.006 mm and 0.010 mm, respectively. Additionally, the measurement of Total Indicator Runout (TIR) according to the angle showed that the maximum cylindricity of the outer and inner diameters was 0.02 mm and 0.025 mm, respectively. Finally, through burr-height measurement at the hole boundary, it was found that the heights were within 0.05 mm.

• Korean Journal of Agricultural Science
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• v.37 no.1
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• pp.37-43
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• 2010

This study carried out to develop barrier-free certification program in forest trail. It is done to provide the certification system presented about certification organized, certification standard and indexes, evaluation method and operation plan. In order to develop certification program in forest trail, detailed measurement index must be developed earlier based on an accessbility, a stability, a preservation and a walking continuity. The suitable forest trail for weak pedestrian was investigated that running slope should be 1/20(5%) maximum, cross slope cannot exceed 1/50(2%) maximum and clear tread width should be above of minimum 90cm. In addition, the trail type is designed as a mixed trail system which is a combination of the loop and the line form and its distance should be 225~675m. Finally, forest trail should be manage sustainably by having regular monitoring and evaluation.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.2
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• pp.231-237
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• 2017

The profile of unpaved road is an important issue in the reliability of endurance test. Efforts on measuring 2D road profile and analyzing the severity have been continued in the study of performing reliable endurance test evaluations through reflecting the results of such measurement and analysis. However, 2D road profile has limitation in measuring the profile in the road width direction because data is obtained along the trailer wheel track. Therefore, in order to measure 3-dimensional shape of road surface and construct severity DB of 3D road profile, Changwon Proving Ground(CPG) of Agency for Defense Development(ADD) developed 3D profilometer which is composed of laser scanner, IMU, GPS, encoder and so on. This paper focuses on the analysis of unpaved road severity using 3D road profile for army operation roads. This results will be used to manage test courses severity of CPG.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.2
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• pp.147-158
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• 2020

In this paper, we will review the thruster based reaction wheel momentum dumping method for low Earth orbit satellite. Thruster based momentum dumping is widely used in GEO satellites by performing momentum dumping and attitude control using thrusters at the specific time. LEO satellite should perform momentum dumping at any time, thus it is not appropriate to use GEO satellite's momentum dumping method. In this research, we will review the method for LEO satellite, which perform momentum dumping always and use reaction wheels for attitude control during dumping. To reduce thruster's valve on and off counts, we propose to use the maximum pulse width for thruster operation. To prevent attitude error increase by thrusters, we adjust the thruster operation interval. Through simulation, we verify the proposed method's effects.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.3
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• pp.122-129
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• 2012

This study investigates structural and vibration analyses according to the thickness of bicycle frame tube. The model of bicycle frame has the dimension as length of 862mm, width of 100mm and hight of 402.5mm. There are 3 kinds of models with tubes of top, down and seat at bicycle frame as thicknesses of 10, 15 and 20mm. The maximum displacement and stress occur at the center part of seat stay and at the installation part of rear wheel respectively. Maximum displacements become 0.031936, 0.029159 and 0.027984mm in cases of thicknesses of 10, 15 and 20mm respectively. In case of thickness of 20mm among 3 cases, maximum displacement becomes lowest. But maximum stresses become 10.019, 8.5492 and 9.2511MPa in cases of thicknesses of 10, 15 and 20mm respectively. In case of thickness of 15mm among 3 cases, maximum stress becomes lowest. There is no resonance at practical driving conditions and natural frequency remains almost unchanged along the change of thickness. In case of the displacement due to vibration mode, the displacement difference at thickness between 15mm and 20mm becomes 1/2 times than that between 10mm and 15mm. Design at bicycle frame tube becomes most economical and durable effectively in case of thickness of 15mm among 3 cases.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.30-37
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• 2012

Pneumatic Active Engine Mount(PAEM) with open-loop control system has been developed to reduce the transmission of the idle-shake vibration induced by engine effectively and economically. A solenoid valve installed between PAEM and vacuum tank is on-off switched by the Pulse Width Modulate(PWM) control signal to decrease the dynamic stiffness of the engine mount. This paper presents the methodology to identify the optimal values of control parameters of a PAEM, i.e, turn-on timing and duty ratio of PWM signal for 6 different idle driving conditions. A scanning algorithm was first applied to the vehicle test to obtain the approximate optimal control parameters minimizing the vibration at front seat rail and at steering wheel. Then the PAEM system identification was fulfilled to find accurate optimal control parameters by using multi-layer neural networks of Levenberg-Marquardt algorithm with vehicle test data.

• Journal of Biomedical Engineering Research
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• v.17 no.1
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• pp.1-10
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• 1996

In this paper, describe the automatic climbing wheelchair system use an articulated crawler mobile robot. This wheelchair system(call system) is composed of sensor detecting part and wireless communication part with PC. The sensor parts are consisted of sloping sensor and ultrasonic sensor part. The sloping sensor measures the sloping angle of system, and the ultrasonic sensor measures the distance of system's front wheel center from stair. PC will generate the operation data to climb up the stair using the measured data and make primitives for the system. At firsts This system transfer from sensor data to the PC. PC calculate the operation data to climb up the stair from the internal algorithm. We simulated the system in various stair angle slope($25^{\circ}$, $30^{\circ}$, $45^{\circ}$), and tested it on the real staircase with width 37cm, highlt 18cm, Angle $26^{\circ}$ . There were $0.350^{\circ}$ - $1.060^{\circ}$ Angle errors while climbing because adapted sensor has a precision $0.35^{\circ}$ in resolution. Finally, We implemented the sensor detecting part and the wireless communication park and practiced our system in 4cm/sec speed.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.676-681
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• 2001

ABS is a safety device, which adds hydraulic system to the existing brake system to prevent wheel from locking, so we can obtain maximum braking force on driving. The hydraulic system to control braking pressure consists of sol-flow type using solenoid valve, flow control valve or consists of sol-sol type using two solenoid valve. In this paper, the hydraulic system in ABS is composed of sol type using a 3port-2position solenoid valve, and vehicle system is composed of 1/4 vehicle model. And slip ratio is controlled using PWM (Pulse-Width-Modulation) control algorithm. Braking friction coefficient and tracking friction coefficient which are described by slip ratio's function have maximum value when slip ratio has its value from 0.1 to 0.3. And slip ratio is controlled constantly in this boundary value even in the variation of road's condition in some boundary.