• 한국위성정보통신학회논문지
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• 제10권3호
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• pp.68-72
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• 2015

철도는 친환경 요소를 두루 갖춘 최첨단 교통수단으로 주목받고 있을 뿐만 아니라 더 나아가 다른 교통수단과의 경쟁에서 우위를 차지하기 위해 여객수송의 품질 향상과 운행에너지 절감을 위한 다양한 연구가 진행되고 있다. 하지만, 도시철도에서는 불특정 다수의 승객에게 서비스하는 업종 특성상 운송효율과 에너지절감을 위한 연구가 대부분이고 여객수송의 품질 향상에 대한 연구는 미비하다. 따라서 본 연구에서는 여객 수송의 품질향상 측면으로 접근하여 도시철도 노선에서 일반열차와 급행열차의 자 수동 운전방식의 3차원 진동 횡가속도를 다양한 환경에서 측정하고, 이 측정된 3차원 진동 횡가속도와 국제철도협회에서 제시한 UIC513R의 통계적인 기법을 기반으로 승차감을 도출하고 비교 분석하였다.

• Journal of Electrical Engineering and Technology
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• 제1권1호
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• pp.101-105
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• 2006

In this paper, a disk-type ultrasonic motor using a combination of radial and bending vibration modes is newly designed and fabricated. The characteristics of the test motor are also measured. By means of traveling elastic wave induced at the surface of circumference of the elastic disk, a steel bar in contact with the surface of circumference of the elastic disk bonded onto the piezoelectric ceramic disks is driven in both directions by changing the sine and cosine voltage inputs. The stator of the motor is composed of two sheets of piezoelectric ceramic disks to bond onto both surfaces of an elastic disk, respectively. As a result, the diameter of the elastic body is increased and the resonant frequency is decreased. The resonant frequency of the stator is about 92 kHz, which is composed with piezoelectric ceramic disks of 28 mm in diameter and 2 mm in thickness, and an elastic body of 32 mm in diameter and 2 mm in thickness. A driving voltage of 20 VPP Produces 200 rpm with a torque of 1Nm and an efficiency of about 10%.

• 드라이브 ㆍ 컨트롤
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• 제14권2호
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• pp.30-36
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• 2017

This paper presents a sliding mode observer-based fault detection algorithm for steering inputs of an all-terrain crane. All-terrain cranes with multi-axles have several steering modes for various working purposes. Since steering angles at the other axles except the first wheel are controlled by using the information of steering angle at the first wheel, a reliable signal of the first axle's steering angle should be secured for the driving safety of cranes. For the fault detection of steering input signal, a simplified crane model-based sliding mode observer has been used. Using a sliding mode observer with an equivalent output injection signal that represents an actual fault signal, a fault signal in steering input was reconstructed. The road steering mode of the crane's steering system was used to conduct performance evaluations of a proposed algorithm, and an arbitrary fault signal was applied to the steering angle at the first wheel. Since the road steering mode has different steering strategies according to different speed intervals, performance evaluations were conducted based on the curved path scenario with various speed conditions. The design of algorithms and performance evaluations were conducted on Matlab/Simulink environment, and evaluation results reveal that the proposed algorithm is capable of detecting and reconstructing a fault signal reasonably well.

• Journal of Biosystems Engineering
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• 제38권4호
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• pp.255-263
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• 2013

Purpose: It is not easy to drive a rice-transplanter avoiding underlapped or overlapped transplanting in paddy fields. An automated guidance system for the riding-type rice-transplanter would be necessary to operate the rice-transplanter autonomously or to assist the beginning drivers as a driving aid. Methods: A prototype of guidance system was composed of embedded computers, RTK-GPS, and a power-steering mechanism. Two Kalman filters were adopted to overcome sparse positioning data (1 Hz) from the RTK-GPS. A global Kalman filter estimated the posture of rice-transplanter every one second, and a local Kalman filter calculated the posture from every new estimation of the global Kalman filter with an interval of 200 ms. A PID controller was applied to the row-following mode control. A control method of U-turning mode was developed as well. A stepping motor with a reduction gear set was used to rotate the shaft of steering wheel. Results: Test trials for U-turning and row-following modes were done in a paddy field after some parameters have been tuned at the ground speed range of 0.3 ~ 1.2 m/s. The minimum RMS error of offset was 3.13 cm at the ground speed of 0.3 m/s while the maximum RMS error was 13.01 cm at 1.2 m/s. The offset RMS error tended to increase as the ground speed increased. The target point distance, LT also affected the system performance and PID controller parameters should be adjusted on different ground speeds. Conclusions: A target angle-based PID controller plus stationary steering angle controller made it possible for the rice-transplanter to steer autonomously by following a reference line accurately and even on U-turning mode. However, as condition in paddy fields is very complicated, the system should control the ground speed that prevents it from deviating too much due to ditch and slope.

• International Journal of Aeronautical and Space Sciences
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• 제16권4호
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• pp.520-528
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• 2015

The piezoelectric-hydraulic actuator is a hybrid device that consists of a hydraulic pump driven by a piezo-stack coupled to a conventional hydraulic cylinder. The actuator is of compact size, but can produce a moderate energy output. Such hybrid actuators are currently being researched and developed in many industrialized countries due to the requirement for high performance and compact flight systems. In a previous study, we designed and manufactured a unidirectional hybrid actuator. However, the blocking force was not as high as expected. Therefore, in this study, we redesigned the pump chamber and hydraulic cylinder and also improved the system by removing the air bubbles. Two different types of piezo-stacks were used. In order to achieve bidirectional capabilities in the actuator, commercial solenoid valves were used to control the direction of the output cylinder. Experimental testing of the actuator in unidirectional and bidirectional modes was performed to examine performance issues related to driving frequency, bias pressure, reed valve thickness, etc. The results showed that the maximum blocking force was measured as 970.2N when the frequency was 185Hz.

• 한국철도학회논문집
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• 제18권2호
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• pp.94-104
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• 2015

트램은 1900년대 초중반 대중교통으로서 많이 이용되어 왔으나, 이 후 교통체계가 자동차 중심으로 발전됨에 따라, 도시교통난 유발과 도시환경미관을 저해하는 등의 이유로 활용성이 낮아졌다. 최근에는 친환경적 최첨단 트램기술이 개발되어 트램에 대한 수요가 점차 증가하고 있는 상황이다. 이러한 트램 교통시스템이 철도와 도로교통의 두 가지 특성을 갖고 있음에도 불구하고 우리나라에서는 관련 법령에 트램 운전자의 자격에 대해서 규정하고 있지 않다. 트램은 도로 교통과 인접하거나 연계되어 운영되기 때문에 자동차와의 사고발생 가능성이 높으므로, 우리나라에 효과적으로 도입하기 위해서는 운전자의 자격요건을 정립함으로써 사고 시 피해를 최소화하고 신속한 대응이 가능하도록 해야 할 필요가 있다. 본 연구에서는 이를 위하여 해외 트램 운전자격제도를 조사, 검토하였고 이를 통해 철도안전법 및 하위법령 등 관련 법에 대한 보완방안을 고찰하였다.

• 한국전기전자재료학회논문지
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• 제34권6호
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• pp.480-486
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• 2021

Magnetoelectric (ME) composite is composed of a piezoelectric material and a magnetostrictive material. Among various ME structures, 2-2 type layered ME composites are anticipated to be used as high-sensitivity magnetic field sensors and energy harvesting devices especially operating at its resonance modes. Rosen type piezoelectric transducer using piezoelectric material is known to amplify a small electrical input voltage to a large electrical output voltage. The output voltage of these Rosen type piezoelectric transducers can be further enhanced by modifying them into ME composite structures. Herein, we fabricated Rosen type ME composites by sandwiching Rosen type PMN-PZT single crystal between two Ni layers and studied their ME coupling. However, the voltage step-up ratio at the resonance frequency was found to be smaller than the value calculated with α_ME value. The ATILA FEA (Finite Elements Analysis) simulation results showed that the position of the nodal point was changed with the presence of a magnetostrictive layer. Thus, while designing a Rosen type ME composite with high performance in a resonant driving situation, it is necessary to optimize the position of the nodal point by optimizing the thickness or length of the magnetostrictive layer.

• 전기전자학회논문지
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• 제22권4호
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• pp.941-947
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• 2018

일반적으로 커패시터는 빈번한 충 방전으로 시스템의 수명에 큰 영향을 미친다. 본 논문에서는 고전압, 대전류의 HVDC 서브모듈용 필름 커패시터의 핵심 고장원인을 분석하여 커패시터의 설계 및 제조공정의 주의사항을 분석한다. 먼저 커패시터의 FMEA 수행을 통해 고장원인, 고장모드, 고장영향에 대해 분석한다. 커패시터의 고장에 가장 큰 영향을 주는 고장원인과 영향을 정량적으로 평가하기 위해 커패시터에 대한 고장나무(Fault-tree)를 제시하고 설계인자와 구동환경의 조건에 따른 고장률을 분석한다. 커패시터 고장의 핵심 원인이 커패시턴스 변화에 있음을 확인하고, 커패시터의 고장률 저감을 위해서 커패시터의 설계와 제조공정 중 온도상승, 코로나 발생, 전극팽창, 절연거리 감소를 최소화할 필요가 있음을 검증한다.

• 전기전자학회논문지
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• 제23권1호
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• pp.254-260
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• 2019

본 논문에서는 양방향 dc-to-dc 컨버터의 고장원인, 고장영향, 고장 결과를 파악하기 위한 failure mode and effect analysis(FMEA)와 양방향 컨버터의 위험도를 고려한 fault-tree analysis(FTA)를 통해 고장률을 예측한다. 전기차의 구동전압을 효율적으로 상승시키기 위해 인버터 앞단에 부착되는 양방향 컨버터는 배터리 전력을 dc-link 커패시터로 방전시키는 승압모드와 회생전력을 배터리로 충전시키는 강압모드를 가진다. 양방향 컨버터의 동작 특성을 고려한 FMEA 결과를 바탕으로 컨버터의 위험도를 고려한 고장나무를 설계한다. 전기차 MCU용에 맞는 설계 파라메타를 설정하고 출력전압 리플과 인덕터 전류 리플에 따른 커패시터와 인덕터의 부품 고장률을 분석한다. 또한 동작 온도에 따른 주요부품의 고장률을 MIL-HDBK-217F를 이용하여 구한다. 마지막으로 부품 고장률을 고장나무의 기본 사상의 고장률로 반영하여 컨버터 고장률과 평균고장시간을 예측한다.

• 한국입자에어로졸학회지
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• 제20권2호
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• pp.47-56
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• 2024

In this study, an empirical study was conducted to investigate the clean air delivery rate (CADR) and the proper particle cleaned air delivery per hour (PCH) of the air cleaning device installed in passenger car cabin. Changes in internal particle concentration were measured in the cabins of the pick-up type engine-driven car and the electric vehicle depending on cabin air filters, ventilation modes, and blower settings. In the tested cars, PM_2.5 collection efficiency of the HEPA filter was higher than that of the genuine filter. The PM_2.5 collection efficiency of each cabin air filter was measured to be similar regardless of the blower setting of the tested cars. This means that the higher the blower setting, the higher the CADR and the PCH. The infiltration rate varies depending on the air tightness of the car. The cabin was more contaminated with particles under driving. From the CADRs measured inside the passenger car cabin, the recirculation mode of HVAC system is a more effective for managing ultrafine particles than the fresh air mode. From a few assumptions, the proper PCH was derived about 0.8 times/min (48 times/h). From this result and several experiments, the proper operation setting of air cleaning device installed inside cars can be found out to control indoor air quality. Also, an appropriate operation settings of HVAC system can be found with considering cooling and heating conditions for thermal comfort in passenger car cabin.