• 한국자동차공학회논문집
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• 제22권6호
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• pp.104-112
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• 2014

Generally, numerical approaches of evaluation for vehicle seat comfort have been studied without considering time-dependent characteristics and the only seating moment have been considered in seat design. However, the comfort not only at the seating moment but also in the long-term should be evaluated because the passengers are sitting repeatedly on the seat to drive the vehicle for hours. So, the aim of this paper is to carry out a quantitative evaluation of the time-dependent mechanical characteristics of seat foams and to suggest a process for predicting the viscoelastic deformation of seat foam in response to long-term driving. To characterize the seat materials, uniaxial compression and tension tests were carried out for the seat foam and stress relaxation tests were performed for evaluating the viscoelastic behavior of the seat foam. A unit solid element model was used to verify the reliability of the material model with respect to the compression behavior of the seat foam. It is not straightforward to evaluate the time-dependent compression of foams using the explicit solver because the viscoelastic material model is limited. To use the explicit solver, the material model must be modified using stress-degradation data. Normalized stress relaxation moduli were added to the stress-strain curves obtained under static conditions to achieve a time-dependent set of stress-strain relations that were compatible with the implicit solver. There was good agreement between the analysis results and experimental data.

• Journal of Biosystems Engineering
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• 제21권2호
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• pp.134-145
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• 1996

Since the skid-steer loader is able to work for excavating, lifting and transporting load even at the narrow space, they are widely used in the regular farm and the livestock farm. The skid-steer loader normally adopts the hydrostatic transmission because the power to move the machine backward and forward should be delivered independently on both sides of wheels. Contrast to the mechanical system such as chain and belt transmissions, however, the hydrostatic transmission is less efficient in the use of energy and more difficult in the maintenance. This study was intended to investigate the feasibility of using triangular-type belt clutch and V-belt transmission for the newly developed skid-steer loader in order to overcome the problems stated in the hydrostatic transmission. In the developed triangular-type belt clutch, the centers of driving, driven and idler sheaves are arranged in the triangular shape in a plane, and V-belts were loaded loosely on three sheaves. The power is transmitted by pressing the idler connected to a lever on the loosened V-belt. Contrast to the normal belt clutch using two sheaves, the newly developed belt clutch has the characteristics of small contact-angle of the driving sheave at no bucket load and increasing contact-angle at the time of power transmission. The results of research can be summarized as follows: 1) The developed triangular-type belt clutch adopted a spring-loaded slackside idler which could transmit more power than a fixed idler could by sacrificing the belt life. The life of V-belt used in the power transmission reached at 500 hours(6 months) when the engine power of 11.8 ㎾ was transmitted. Also, it was feasible to develop the large industrial skid-loader with the V-belt transmission by using the proper set of sheaves. 2) The developed skid-steer loader changed the rotating radius and speed with bucket loads as the conventional skid steer loader did. The rotating speed was 47 deg/s at the maximum bucket load of 2.74 kN when the minimum rotating radius was 1.5m. 3) The power required in turning at the bucket load of 2.74 kN was 4 ㎾ and the slippage of V-belt was less than 1%.

• 농업과학연구
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• 제47권2호
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• pp.327-335
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• 2020

The purpose of this study was to analyze the load distribution and contact safety factor for the power take off (PTO) gear of a 71 kW class agricultural tractor. In this study, a simulation model of the PTO gear-train was developed using Romax DESGINER. The face load factor and contact safety factor were calculated using ISO 6336:2006. The simulation time was set at 2,736 hours considering the lifetime of the tractor, and the simulation was performed for each PTO gear stage at the engine rated power conditions. As a result of the simulation, the face load factors for the driving gear at the PTO 1^st, 2^nd and 3^rd stages were 1.644, 1.632, and 1.341, respectively. The contact safety factors for the driving gear at the PTO 1^st, 2^nd and 3^rd stages were 1.185, 1.216, and 1.458, respectively. As the PTO gear stage was increased, the face load factor decreased, and the contact safety factor increased. The load distributions for all the PTO gears were concentrated to the right of the tooth width. This causes stress concentrations and shortens the lifespan of the gears. Therefore, it is necessary to improve the face load factor and the contact safety factor with macro-geometry and micro-geometry.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.247-251
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• 2001

Universal motors are mainly used for vacuum cleaner application. There are a lot of researches on SRM that applys home appliance throughout the world. The manufacturing cost of SRM drive makes it hard to expand its application to home appliance. This paper presents Single Phase SRM for the vacuum cleaner that has advantge in cost and performance over conventional universal motor. This paper proposes new power device driving scheme by using SRM switching characteristic. The driving scheme is very simple and inexpensive. Dwell Time Control method is used for the minimum switching loss of power device. The switching frequency of power device is less than 4.5kHz at 45,000rpm. By use of this scheme, power device based on very small switching losses can be used on SRM drive. Also, the biggest problem in single phase SRM is starting, this paper shows a new starting algorithm with two hall sensors, accelerating and running sensors, respectively. Finally, the proposed Single Phase SRM achieves higher efficiency and long life time compared to universal motor. Its life time is more than 1500 hours. Its life time is extended 4 times than that of conventional motor and its suction power is increased $20\%$ at the same volume of conventional universal motor.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 춘계학술대회 및 창립 30주년 심포지엄(논문집)
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• pp.247-253
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• 2006

해양 스포츠와 관련하여 체계적인 시스템을 갖추고 있는 대표적인 나라로 호주가 있다. 호주 NSW 주에만 약 45만 명이 레저용 선박 면허를 가지고 있고, 약 20만 명이 등록된 선박의 소유자이며, 이러한 수치는 매년 3-4%씩 증가하고 있다. 본 연구는 이 NSW 주의 보트면허 지침에 관한 조사이다. 면허의 유형과 종류, 선박 등록, 레저용 선박을 선택하고 유지하는 방법, 구비해야 할 안전장비, 항해 전에 점검해야 할 일 등 수상레저를 즐기고자 하는 사람이라면 누구나 알아야 할 필수사항들을 다루고 있다. 그에 더하여 수로 교통법이라든지, 항해표지, 응급 시 대처 방안과 같은 기술적인 면도 언급한다. 최근 주5일 근무제의 확산으로 많은 사람들이 증가된 여가시간을 활용하기 위하여 해상 레포츠에 관심을 기울이고 있는 추세이다. 이러한 수요를 효율적으로 관리 감독하고, 또한 질서 있고 안전한 여가 활동을 제공하기 위하여 좀 더 체계적이고 편리한 레저용 선박 면허제의 도입을 제안하는 바이다.

• 한국지능시스템학회논문지
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• 제20권3호
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• pp.394-399
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• 2010

본 논문은 중량물 운송을 위한 AGV(autonomous guided vehicle)의 주행 제어 방법에 관한 연구이다. 일반적으로 실제 산업 현장에서 하루 20시간 이상 작업하는 경로 추적 방식의 fork-type AGV는 팔레트 하역 작업 시에 목표 지점에 대한 높은 정지 정밀도와, AGV의 정지 정밀도를 높이기 위해 저속으로 주행 하는 기술이 요구 된다. 따라서 본 논문에서는 엔코더의 데이터를 계측 받아 AGV의 주행 속도를 측정 및 분석하여 AGV의 최저 주행 속도 유지 및 AGV의 정지 정밀도를 높이는 주행 제어 방법을 연구 하였다. 본 논문에서 제안한 주행 제어 방법의 실험은 팔레트 앞 4m 지점부터 직선 주행후에 팔레트 하역 작업을 수행하도록 하였고, 총 10회 실험 후에 이들의 정밀도를 분석하였다. 그 결과, 팔레트 하역 시 목표 지점에 대한 정지 정밀도의 최대 오차가 18.64mm이내로 높은 정지 정밀도의 안정적인 주행 제어가 가능함을 확인 할 수 있었다.

• 한국시뮬레이션학회논문지
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• 제29권3호
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• pp.19-25
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• 2020

밭 농업 기계는 심한 경사지와 험로, 재배 작물별 정형화되지 않은 재배양식으로 인해 개발이 어렵다. 특히 고추 수확 작업은 많은 시간과 인력이 요구되는 작업으로 고령화가 가속화되는 국내 농촌의 큰 문제점이다. 본 연구는 부족한 인력을 대체하고 작업 시간을 줄이며 수확 작업을 기계화하기 위해 개발된 고추 수확기의 동적 특성을 연구하고자 한다. 고추 수확기의 동적 특성을 분석하기 위해 동역학 프로그램인 Recurdyn을 이용하여 진행하였으며 모든 분석은 공차를 전제로 분석을 진행하였다. 시뮬레이션 결과에 따라 주행 플랫폼이 주행할 수 있는 안전 범위를 제시하였다.

• Korean Chemical Engineering Research
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• 제61권1호
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• pp.19-25
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• 2023

PEM (Proton Exchange Membrane) 수전해의 성능향상에 대해 많은 연구개발이 진행되었으나, 내구성에 대한 연구는 아직 초기 단계라고 할 수 있다. 본 연구는 성능향상을 위해 PEM 수전해 구동 온도를 상승시켰을 때, 수전해 내구성에 미치는 영향에 대해 연구하였다. 50~80 ℃ 온도 범위에서 일정 전류 조건으로 구동하면서 전압변화, I-V, CV (Cyclic Voltammetry), LSV (Linear Sweep Voltammetry), Impedance, FER (Fluoride Emission Rate) 등을 측정했다. 운전온도가 상승할수록 열화속도가 증가했다. 50~65 ℃에서는 IrO₂ 전극 촉매 열화가 PEM 수전해 셀의 내구성에 주로 영향을 주었다. 80 ℃에서는 고분자 막과 전극 열화가 비슷하게 진행되어 short 저항이 1.0 kΩ·cm² 이하로 감소하면서 shorting 현상에 의해 구동한지 144시간 만에 성능이 초기의 약 1/3로 감소하였다.

• 한국안전학회지
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• 제39권1호
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• pp.55-61
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• 2024

In response to the COVID-19 pandemic, the logistics industry in Korea has rapidly been expanding, with offline demand concentrating on online platforms owing to the development of digital infrastructure. This has increased the workload of courier drivers considerably, along with labor intensity. A delivery driver died recently from overwork due to the continuous increase in delivery volume, which raises social concerns. Delivery drivers work long hours, (over 12 hours) and are greatly affected by weather conditions, such as snow, rain, heat waves, and cold waves. In addition, they lack a fixed workplace; perform atypical work handling workpieces of various sizes, weights, and shapes; and spend a large amount of time driving as part of their work. This work involves a high level of tension and requires attention and concentration. Despite the frequency of industrial accidents in the courier industry, studies on safety and health to quantitatively analyze and systematize the work of courier workers are very scarce. Therefore, to define the work process necessary for investigating the harmful factors in delivery service and the work analysis, this study conducted interviews and on-site surveys to analyze the unit work of the delivery service by targeting delivery workers. In other words, a framework of unit work for work analysis was presented to enable research and analysis by considering the aforementioned characteristics of the courier industry. The process was broadly divided into work, transport, storage, delay, and inspection. Work was divided into loading, sorting, unloading, and door subcategories, and transportation was divided into vehicle, cart, and walking subcategories as well as 10 small processes. Moreover, 22 unit works were again drawn by conducting field surveys and interviews. The risk of unit work derived from this study was ergonomically evaluated, and the ergonomic analysis revealed that uploading and transportation were the most dangerous. The results of this study could be used as basic data for preventing industrial accidents among courier workers, whose work has increased with the logistics volume and the development of the logistics industry.

• 디지털융복합연구
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• 제16권9호
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• pp.1-10
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• 2018

창고형 매장의 성장이 가속화되면서 창고형 매장에 대한 물류의 중요성도 증대되고 있다. 이러한 측면에서 본 연구는 GIS를 사용하여 C사의 Depot 통합운영 후 운송 효율성을 분석하였다. Depot 통합에 따른 컨테이너 출고 물동량 변화를 분석한 결과, 배송시간 측면에서는 Depot 1개를 운영 할 경우 연간 총 1,028,699km 운행이 필요한 것으로 분석되었고, 이는 Depot 3개를 운영할 때 연간 총 2,866,604km 운행이 필요한 상황과 비교할 경우, 연간 1,028,699km 감소가 되는 것을 확인할 수 있다. 배송시간 측면에서도 Depot 1개를 운영 할 경우 일일 62시간의 시간절감과 전체적으로 36%의 절감효과를 기대할 수 있었다. 본 연구는 GIS OD Matrix를 이용하여 Depot 통합과 컨테이너 배송전환에 따른 운영 프로세스 개선, 운송시간 및 거리 절감효과를 제시하였다. 본 연구의 결과는 다른 창고형 할인매장의 배송 프로세스에 영향을 줄 수 있는 중요한 판단지표로 활용될 수 있다.