• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.315-321
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• 2014

This paper presents an integrated chassis control system with fail safety using optimum yaw moment distribution for a vehicle with steer-by-wire and brake-by-wire devices. The proposed system has two-level structure: upper- and lower-level controllers. In the upper-level controller, the control yaw moment is computed with sliding mode control theory. In the lower-level controller, the control yaw moment is distributed into the tire forces of active front steering(AFS) and electronic stability control(ESC) with the weighted pseudo-inverse based control allocation(WPCA) method. By setting the variable weights in WPCA, it is possible to take the sensor/actuator failure into account. In this framework, it is necessary to optimize the variables weights in order to enhance the yaw moment distribution. For this purpose, simulation-based tuning is proposed. To show the effectiveness of the proposed method, simulations are conducted on a vehicle simulation package, CarSim.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.971-974
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• 2014

A ventricular assist device (VAD) is used for bridge to heart transplantation and heart diseases. Knowing the status of a pneumatic pulsatile VAD when implanting it into the body is important: when the velocity of blood flow through the VAD is slow, a thrombus may occur, and thrombosis can be fatal to a patient. In order to determine the state of a VAD, various sensors need to be implanted. Because this introduces the risk of infection and difficulties with sensor management, we developed a method for estimating the state of a VAD indirectly via the pressure in an air tube that can be measured in vitro. We compared the measured values to in vitro experimental results. The estimated and measured values showed some errors, but the accuracy can be improved by refining the estimation process to minimize the risk of infection.

• Journal of Power System Engineering
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• v.14 no.2
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• pp.60-64
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• 2010

This paper introduces reliability improvement and time saving in eddy current inspection by signal characteristic optimization of multi-coil eddy current array probe. In the past, Multi-coil array probe and single probe were used for the gas turbine rotor surface inspection & defect evaluation. The multi-coil array probe was used for the broad area inspection. But the signal deviations among multi-coil array probe are maximum 28% in commercial probe. This differences were considered to impedance differences among coils, so it is very difficult to evaluate exact defect size. The signal deviations among multi-coil array probe are maximum 28% in commercial probe. So, single coil inspection was used for exact defect sizing. The purpose of this study is to improve signal deviations of multi-coil array probe. The introduced new technology can improves this deviation by adjusting input voltage in each coil. At first, apply same voltage in each coil and collect signal amplitude of each coil. And calculate new input voltage based on signal amplitude of each coil. If the signal amplitude deviation is within 5% among multi-coil array probe, the signal amplitude of multi-coil array probe is reliable. The proposed technology gives 2% signal deviation among multi-coil array probe. The proposed new technology gives reliability improvement and inspection time saving in eddy current inspection.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.128-128
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• 2017

현재 식물공장에서 사용되고 있는 이식장치는 핀을 이용하여 육묘트레이 위에서 플러그묘를 뽑아 육묘트레이 또는 포트로 옮겨 심는 방식을 채택하고 있다. 이러한 이식 방식은 셀과 셀 사이에 있는 다른 묘의 잎을 파지함으로써 묘를 2개 이상 취출하는 현상이라든지 핀에 의한 잎 손상 등이 우려되고 있어 이에 대한 개선책이 필요하다. 본 연구는 플러그묘의 이식작업 시 잎 손상을 줄이면서 기계 적응성을 향상시킬 수 있는 이식시스템을 개발하기 위해 진공흡인을 이용한 이식 메커니즘에 대해 검토하였다. 플러그묘 이식시스템은 육묘트레이 셀을 X-Y로 옮기는 묘 이송부, 육묘트레이의 셀 하단으로부터 진공을 발생시켜 묘를 떨어뜨리는 진공 흡인부, 낙하되는 묘를 감지하는 센서와 블로워 및 공압 실린더로 구성된 진공 발생부, 혈공된 포트를 진공 발생부의 유도관으로 옮기는 포트 이송부 등으로 설계 제작하였다. 이식 메커니즘은 육묘트레이 하단부로부터 플러그묘를 1개씩 진공흡인하는 방식을 채택하였고, 이를 위해 상하 모두 개방된 72공 육묘트레이($L538{\times}W280{\times}H45mm$)를 윗부분(Ø35mm) 보다 아랫부분(Ø37mm)의 셀이 넓은 형상으로 PP재질의 육묘트레이를 사출금형 제작하였다. 묘 이송부에 장착된 플러그묘는 X축 방향(12개 셀)으로 이식작업이 이루어지고, Y축(6개 셀)으로 이동된 후 다시 동일한 방향으로 연속 작업이 가능하도록 제어프로그램을 구성하였다. 이식 원리는 진공 흡인부에 플러그묘가 이송되면 진공 발생부의 흡착패드가 위로 전진하여 진공을 발생시켜 묘를 흡인하고, 유도관 내에 부착된 광화이버센서에 의해 묘를 감지하여 블로워와 공압실린더를 제어함으로써 이식 공정이 끝나게 된다. 로메인상추의 플러그묘를 대상으로 진공흡인 시험을 실시한 결과 묘 손상없이 이식작업이 가능한 것으로 확인되었다.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.13-18
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• 2011

This thesis is about the result of conducting a specific experiment for the development of noncontact vibration displacement sensor for measuring the spindle vibration that is used for conditional monitoring of machinery. One should be careful when using the eddy current type displacement sensor because the sensitivity of it is different according to the quality of the material. While the probe used for nondestructive inspection adopts the effect of transmitting the material by using the high frequency domain, the eddy current type displacement sensor uses the lower frequency of around 1MHz. Also, while the nondestructive probe uses the method of enhancing output by using the resonance zone, the vibration displacement sensor utilizes the stable zone by avoiding the resonance zone. Since the oscillator of the converter uses the "L" element as Probe, its characteristic changes with the variation of a relevant impedance. In other words, if the length of Probe's Cable gets extended (Impedance increase), the sensitivity declines accordingly. The effect of surrounding temperature was small, but the influence of the quality of Sensor Coil used was high. Moreover, following an experimental demonstration of the phenomenon where the sensitivity decreases as the frequency of the tested material increases from a frequency response test, the maximum frequency that could be measured was approximately 1KHz. It was noted that the degree of precision could be maintained by using the gap of the probe in the linear zone at the installation site.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.469-475
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• 2017

Workers in industrial fields are highly exposed to accidents or injuries caused by long working hours. An exoskeleton that is able to support the arm muscles of the worker and thereby reduce the probability of an accident and enhance working efficiency could be a solution to this problem. However, existing exoskeletons demand the use of high-priced sensors and motors, which makes them difficult to use in industrial fields. To solve this problem, we developed an arm assisting exoskeleton that consists only of mechanical components without any electronic sensors or motors. The exoskeleton follows the movement of the human arm by shoulder joint and ankle joint. In addition, counterbalance mechanisms are installed on the exoskeleton to support arm strength. The experimental validation of the exoskeleton was conducted using an EMG sensor, confirming the performance of the exoskeleton.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.5
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• pp.772-778
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• 2018

Due to the recent advances in computing, communication and micro-electromechanical technology, Wireless Sensor Networks (WSNs) applications have been extended from military to many commercial areas such as object tracking, wire detection, and vehicular sensor networks. In some applications bursty data from many sensor nodes may be generated and the generated data from the monitoring area may be sent in a limited time to the final destination, sink node. In this paper, we present a BTF-MAC protocol adequate for WSNs applications in which bursty data packets are required to be transmitted in a limited time. The BTF-MAC is a synchronous duty-cycle MAC protocol and uses a slot-reserved and operational period extension mechanism adapted to the traffics. Our numerical analysis and simulation results show that BTF-MAC outperforms other related protocols such as DW-MAC and SR-MAC in terms of energy consumption and transmission delay.

• Journal of Sensor Science and Technology
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• v.3 no.3
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• pp.45-53
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• 1994

A new type of Si diaphragm was fabricated using Si-wafer direct bonding and two-step electrochemical etch-stopping methods. Using the new diaphragm structure in mechanical sensors, more precise control of cavity depth and diaphragm thickness was achievable. Also, the propagation of the stress, which was generated near the bonding interface, to the surface can be avoided. Finally, a piezoresistive-type Si pressure sensor was fabricated utilizing the diaphragm and a digital pressure gauge, which can display units of pressure, was realized.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.1
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• pp.42-48
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• 2011

This paper presents the vibration reduction algorithm at the walking-will recognition sensors on the uneven terrain. Recently, concern about walking assistant aids is increasing according to the increase in population of elder and handicapped person. However, most of walking aids don't have any actuators for its movement. So, general walking aids have weakness for its movement to upward/download direction of slope. To overcome the weakness of the general walking aids, many researches for active type walking aids are being progressed. Especially, vibration analysis and impulse reduction are one of the important elements of the active-type walking aid during moving on the outdoor area because the ground has many kinds of obstacles such as speed dumps, puddles and so on. So, we analyze the influence from vibration by uneven terrain. And then, we propose the impulse reduction algorithm to overcome the vibration. All the processes are verified experimentally in an active-type walking aid.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.6
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• pp.1949-1954
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• 2010

The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region(dead band) due to the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference, and an angular increment is not detected. This problem can be overcome by mechanically dithering the gyroscope. This paper presents the design method of mechanical dither by the theoretical considerations and the verification of the theoretical equations through FEM(Finite Element Method) applications. As a result, the maximum prediction error of resonant frequency and peak dither rate was under 5 percent. The theoretical equations for the mechanical performances of dither can be said to be feasible.