타워야더에 의한 집재작업 생산성 및 비용 분석

조민재 ( Min Jae Cho ),조구현 ( Koo Hyun Cho ),오재헌 ( Jae Heun Oh ),한한섭 ( Han Sup Han ),차두송 ( Du Song Cha ) 한국임학회 2014 산림과학 공동학술대회 논문집 Vol.2014 No.-

본 연구는 강원도 양양군 서면 지역의 소나무, 활엽수 혼효임분을 대상으로 임목집재작업에서 사용된 두 기종의 타워야더(Koller K301-4, Koller K300)의 작업생산성 및 비용을 검토하였다. 이용된 작업방식은 모두 전간집재이고, 집재방향 상향집재로 동일한 작업조건이였다. K301-4를 이용한 작업지의 임지경사는 20°이였고, K300를 이용한 작업지의 임지경사는 15°였다. 집재작업 생산성 분석에서 K301-4의 시간당 생산성(4.7㎥/hr)이 K300의 시간당 생산성(2.3㎥/hr) 보다 높았으며, 집재작업 비용은 K300이 61,316원/㎥이고, K301-4는 29,484원/㎥이였다. 두 기종의 동일한 작업조건(평균가로집재거리 7m, 평균 집재본수 2본, 임목재적 0.417㎥)에서, 집재효율성 비교를 위한 집재거리에 따른 민감도분석 결과는 집재거리 50m를 기준으로, 50m 이상은 타워야더(K301-4)를 이용한 작업이, 50m 미만에서는 타워야더(K300)을 이용한 집재가 더 효율적인 것으로 나타났다. This study was conducted to examine harvesting productivity and cost using two different tower-yarders(Koller K301-4 and Koller K300) in a Pine( Pinus densiflora) and Oak spp. mixed stand of Seo-myeon, Yangyang-gun, Kangwon-do. There were the same operation conditions(tree-length logs and uphill yarding) but slope gradients of the site were 20 °(K301-4) and 15 °(K300), respectively. Harvesting productivity by K301-4(4.7 ㎥/hr) was higher than that of K300(2.3 ㎥/hr). Also, harvesting cost by K300(￦ 61,316/㎥) was more expensive than that of K301-4(￦ 29,484/㎥). Under the same operation conditions(average lateral yarding distance (7 m); average the number of logs (2); average volume (0.417 ㎥/log)), the sensitivity consideredthe yarding distance showed that K301-4 had high harvesting productivity at the yarding distance(longer than 50 m), while K300 was efficient at the yarding distance(less than 50 m).

격자형 압력 센서 배치 구조를 이용한 다층 기반 누운 자세 판별 알고리즘

조민재(Min Jae Cho ),홍윤식(Youn-Sik Hong) 한국산학기술학회 2019 한국산학기술학회논문지 Vol.20 No.6

치매 환자나 혼자 힘으로 전혀 움직이지 못하는 노인 환자는 간병 인력 부족으로 낙상 사고 및 욕창 발생 가능성이 매우 크다. 본 논문에서는 이러한 문제를 해결하기 위해 일정 주기마다 감지한 압력 세기를 기준으로 머리, 어깨, 엉덩이 등 주요 신체 부위를 판별하여 환자의 누운 자세를 판별할 수 있는 알고리즘을 제안한다. 신체적 특성에 무관하게 신체 부위 판별이 가능하도록 격자 구조로 압력 센서를 배치한 스마트 매트를 제작하였다. 스마트 매트는 7x7 배열 크기의 2개 모듈을 조합하여 구성하였다. 각 모듈은 모두 49개의 FSR-406 센서로 구성되며 독립적으로 압력을 감지한다. 각 모듈에 대해 필터를 사용한 누적 압력 합 등 압력 분포를 이용해 상체 또는 하체에 해당하는 신체 부위를 순차적으로 판별한다. 제안한 알고리즘은 머리, 어깨, 엉덩이 부위 등 계층-1에 속한 신체 부위간 포함 관계를 조사해 5가지 누운 자세를 판별할 수 있다. Patients with dementia or elderly patients who can not move at all by themselves are at a high risk of falls and bedsore due to lack of caregivers. In this paper, to solve this problem, we propose an algorithm to determine the patient"s lying postures by discriminating the main body parts such as head, shoulders, and hips based on the pressure intensity sensed at regular intervals. A smart mat with a lattice structure in which a pressure sensor is arranged so that the body part can be discriminated irrespective of the physical characteristics has been implemented. It consists of two modules of 7x7 array size. Each module consists of 49 FSR-406 sensors and independently senses pressure. For each module, the body part corresponding to the upper body or the lower body is sequentially discriminated by using a pressure distribution such as a cumulative pressure sum using a filter. The proposed algorithm can identify five lying positions by examining the inclusion relationship between body parts belonging to layer-1 such as head, shoulder, and hip area.

벌도 및 가지제거작업에서 세 가지 인간공학적 위험 평가기법의 비교분석

조민재 ( Min-jae Cho ),정응진 ( Eung-jin Jeong ),오재헌 ( Jae-heun Oh ),한상균 ( Sang-kyun Han ) 한국산림과학회(구 한국임학회) 2021 한국산림과학회지 Vol.110 No.2

우리나라 모든 산업에서 근골격계질환은 작업자들의 안전에 큰 영향을 미치고 있으며, 산림작업은 산업안전보건법에 따라 근골격계 부담작업으로 분류된다. 특히 벌도 및 가지제거작업은 주로 인력작업으로 실시되고 있으며, 작업원의 안정성 확보를 위해 작업자세에 대한 평가가 필요하다. 따라서 본 연구는 체인톱을 이용한 벌도 및 가지제거작업의 작업자를 대상으로 세가지 인간공학적 분석 도구(OWAS, RULA, REBA)를 이용하여 위험도를 평가하고, 평가기법별 작업자세에 대한 영향인자를 분석하였다. 벌도와 가지제거작업자세의 위험도는 RULA, OWAS, REBA 순으로 높게 평가되었으며, 대부분 2∼3단계로 작업자세의 즉각 변경조치는 요구되지 않았다. 하지만 벌도작업에서 허리와 다리를 굽힌자세와 가지제거작업에서 벌도목 위에서 작업하는 자세는 위험도가 매우 높게 분석되었다. 또한 벌도작업의 경우 산지경사, 가지제거작업의 경우는 지상에서부터 벌도목 높이가 작업위험도 평가에 영향이 높은 것으로 분석되었다. 따라서 산림작업에 있어서 작업자의 안전성을 확보하기 위해 작업부하가 낮은 자세(벌도작업: 쪼그리는 자세, 가지제거작업: 허리와 다리가 곧은 자세)로 작업하는 것이 바람직한 것으로 사료된다. Musculoskeletal disorders affect workers' safety in most industries, and forest operations are classified as a musculoskeletal burden according to the Occupational Safety and Health Act in South Korea. In particular, felling and delimbing operations are mainly conducted by manpower, and then, it is necessary to evaluate ergonomic risk assessment for safety of felling and delimbing workers. Three ergonomic risk assessment methods, such as Ovako Working posture Analysis System (OWAS), Rapid Upper Limb Assessment (RULA), and Rapid Entire Body Assessment (REBA), are available for assessing exposure to risk factors associated with timber harvesting operations. Here, three ergonomic risk assessment methods were applied to examine ergonomic risk assessments in chainsaw felling and delimbing operations. Additionally, exposure to risk factors in each method was analyzed to propose an optimal working posture in felling and delimbing operations. The risk levels of these operations were evaluated to be highest in the RULA method, followed by the OWAS and REBA methods, and most of the exposed working postures were examined with a low-risk level of two and three without requiring any immediate working posture changes. However, two significant working postures, including the bending posture of the waist and leg in felling operation and standing posture on the fallen trees in delimbing operation, were assessed as the high-risk level and needed immediate working posture changes. Low-risk work levels were examined in the squatting posture for felling operation and the straightened posture of the waist and leg for delimbing operation. Moreover, the slope in felling operation and the tree height in delimbing operation significantly affected risk level assessment of working posture. Therefore, our study supports that felling and delimbing workers must operate with low-risk working postures for safety.

무인항공기 사진측량 방법에 의한 산림 미세지형 평가

조민재 ( Min-jae Cho ),최윤성 ( Yun-sung Choi ),오재헌 ( Jae-heun Oh ),이은재 ( Eun-jai Lee ) 한국산업융합학회 2021 한국산업융합학회 논문집 Vol.24 No.3

Unmanned aerial vehicles(UAV) photogrammetry provides a cost-effective option for collecting high-resolution 3D point clouds compared with UAV LiDAR and aerial photogrammetry. The main objectives of this study were to (1) validate the accuracy of 3D site model generated, and (2) determine the differences between Digital Elevation Model(DEM) and Digital Surface Model(DSM). In this study, DEM and DSM were shown to have varying degree of accuracy from observed data. The results indicated that the model predictions were considered tend to over- and under-estimated. The range of RMSE of DSM predicted was from 8.2 and 21.3 when compared with the observation. In addition, RMSE values were ranged from 10.2 and 25.8 to compare between DEM predicted and field data. The predict values resulting from the DSM were in agreement with the observed data compared to DEM calculation. In other words, it was determined that the DSM was a better suitable model than DEM. There is potential for enabling automated topography evaluation of the prior-harvest areas by using UAV technology.

풋 밸브가 적용된 지열 천공 DTH 해머의 성능 특성에 대한 실험적 연구

조민재(Min Jae Cho),심정보(Jung-Bo Sim),김영원(Young Won Kim) 한국지열·수열에너지학회 2021 한국지열에너지학회논문집 Vol.17 No.1

Drilling equipment is an essential part used in various fields such as construction, mining, etc., and it has drawn increasing attention in recent years. The drilling method is generally divided into three types. There are a top hammer method that strikes on the ground, a DTH (Down-The-Hole) method that directly strikes a bit in an underground area, and a rotary method that drills by using rotational force. Among them, the DTH method is most commonly used because it enables efficient drilling compared to other drilling methods. In the conventional DTH hammer, the valve between the piston and the bit is opened and closed using a face to face method. In order to improve the power of the DTH hammer, a DTH hammer with foot valve which is capable of instantaneous opening and closing is used in the drilling field. In this study, we designed a lab-scale DTH hammer with the foot valve, and manufactured an evaluation device for the experiment of the DTH hammer. In addition, we analyzed the performance of the DTH hammer adopted with foot valve according to the pressure range of 3-10 bar. As a result, the internal pressure distribution in the DTH hammer was experimentally analyzed, and then, the movement of the piston according to the pressure was predicted. We believe that this study provides the useful results to explain the performance characteristics of the DTH hammer with the foot valve.

임목수확방법별 벌도작업 생산성 및 비용 분석

조민재 ( Min-jae Cho ),최윤성 ( Yun-sung Choi ),문호성 ( Ho-seoung Mun ),이충건 ( Chung-geon Lee ),이은재 ( Eun-jai Lee ),정응진 ( Eung-jin Jung ),오재헌 ( Jae-heun Oh ),한상균 ( Sang-kyun Han ),김대현 ( Dae-hyun Kim ),차두송 ( Du 한국임학회 2016 한국산림과학회지 Vol.105 No.4

본 연구는 동일한 임분조건에서 작업자 2명(A: 작업경력 5년 이하, B: 작업경력 15년 이상)을 대상으로 임목수확방법별(전목수확·전간수확·단목수확)에 따른 벌도작업의 작업생산성과 비용을 분석하였다. 전목작업에서 작업자A의 생산성은 10.3 m³/SMH, 작업비용은 2,066원/m³이며, 작업자 B는 생산성 12.7 m³/SMH, 작업비용 2,201원/m3으로 산출되었으며, 시간당 생산성은 작업자 B가 다소 높았지만, 작업비용은 작업자 B의 높은 임금으로 작업자 A가 약간 낮게 나타났다(p>0.05). 전간작업의 경우 작업자 A와 B의 생산성은 각각 2.2 m³/SMH과 3.3 m3/SMH이며, 작업비용은 각각 9,890원/m³과 8,459원/m³으로, 작업자 B가 A보다 생산성은 높게, 작업비용은 낮게 산출되어 작업의 숙련도에 따라 큰 차이를 보이고 있었다(p< 0.05). 단목작업에서 작업자 A와 B의 생산성은 2.3 m³/SMH과 3.0 m³/SMH, 작업비용은 9,584원/m3, 9,395원/m³으로, 작업자 B의 생산성이 높고, 작업비용은 낮게 산출되었다(p >0.05). 이와 같이 벌도작업 중에서도 임목의 절단작업과 같이 높은 숙련도를 요구하지 않는 단순작업에서는 오히려 작업자의 임금이 생산비용에 크게 영향을 미치는 것으로 나타났다. 또한 가지정리와 같이 임지 내 벌도목 사이를 이동하며, 작업하는 것은 작업자의 높은 숙련도가 작업경비의 저감에 영향을 미치는 것으로 판단된다. The purpose of this study was to broaden our knowledge on the productivity and costs of felling operation in three different harvesting methods(whole tree, tree-length and cut-to-length). Felling was conducted in three different harvesting methods with two workers who have different work experiences. Worker A and B have had felling experiences for about 5 years and 15 years, respectively. Felling productivity in whole tree method was 10.3 m³/SMH for worker A and 12.7 m³/SMH for worker B. Felling costs for worker A and B were 2,066 won/m3 and 2,201won/m³, respectively. Although felling productivity of worker B in whole tree method was higher than worker A, felling costs of worker A were similar to worker B because the wage of worker B was more expensive than the wage of worker A (p>0.05). In tree-length method, felling cost of worker B were cheaper than that of worker A. Felling productivity and cost in tree-length method were 2.2 m³/SMH and 9,890 won/m3 for worker A and 3.3 m³/SMH and 8,459 won/m³ for worker B, respectively (p< 0.05). In cut-to-length method, felling productivity and cost were 2.3 m³/SMH and 9,584 won/m³ for worker A and 3.0 m³/SMH and 9,395 won/m³ for worker B, respectively. Felling productivity of worker B was higher than that of worker A (p >0.05). Our preliminary results found that harvesting methods and worker`s experiences highly affect on the productivity and costs of felling operations. These results should be useful for forest managers when planning cost-effective harvesting operations.

설문조사에 의한 임업기능인의 적정 임금체계에 관한 연구

조민재 ( Min Jae Cho ),김명환 ( Myung Hwan Kim ),민도홍 ( Do Hong Min ),한원성 ( Won Sung Han ),한한섭 ( Han Sup Han ),차두송 ( Du Song Cha ) 한국임학회 2014 산림과학 공동학술대회 논문집 Vol.2014 No.-

본 연구는 국·사유림 기능인 영림단을 대상으로 임업기능인의 현실적인 적정 임금수준을 제시하고자 실시하였다. 직종구분은 현재 사용되고 있는 3가지(보통인부, 특별인부, 벌목부)로 구분하였다. 설문조사는 총 19문항으로, 총 659명에게 우편을 통하여 실시하였고, 이 중 30.3%의 회신율을 보였다. 조사된 영림단의 평균 임금은 지역별로 다소차이를 보였으나, 보통인부가 97,680원/일, 특별인부 127,559원/일, 벌목부는 152,403원/일로 나타났다. 소속별(산림사업법인, 산림조합, 국유림) 영림단임금의 차이는 작은 것으로 분석되었다. 현재 분류되고 있는 3가지(보통인부, 특별인부, 벌목부) 직종에서, 보다 산림작업의 특수성을 반영할 수 있는 5가지 직종(산림환경작업부, 초급산림작업인, 중급 산림작업인, 고급산림작업인, 산림장비운전사)으로 구분하면, 임업기능인을 위한 현실적으로 안정된 임금체계를 제시 할 수 있을 것이라 사료된다. There has been a concern on the current pay system for forest workers because it does not effectively reflect the characteristics of typical working conditions in the forest. We addressed the fair wages to forest workers by investigating the current workers wage system. The occupation was classified into 3 types(worker, special worker and feller). We mailed the survey questionnaire consisting of 19 questions to 659 forest workers and received 213 responses resulting in a 30.3% response rate. The results showed that the average wages of forest worker, special worker and feller were ￦ 97,680/day, ￦ 127,559/day and ￦ 152,403/day, respectively though there were variations depending on the regions. In addition, there were little difference in terms of the forest workers`` wage among three different workers`` contraction(private, National Forestry Cooperative Federation, government). We suggest the current work types(worker, special worker and feller) could be divided into 5 work types(forest-environment workers, forest operations in beginner, forest operations in intermediate, forest operations in advanced and forest equipment operator) reflecting specialty of forest operation thereby stabilizing the wage system for forest workers.

낙엽송 간벌작업에서 전간수확시스템의 작업비용 분석

조구현 ( Koo Hyun Cho ),조민재 ( Min Jae Cho ),한한섭 ( Han Sup Han ),한상균 ( Sang Kyun Han ),차두송 ( Du Song Cha ) 한국산림과학회 2015 한국산림과학회지 Vol.104 No.2

The purpose of study was to broaden our knowledge on the productivity and cost of thinning operations which has become increasingly practiced in Korea. The thinning operations were conducted in a 40- year old larch (Larix leptolepis) stand, including chainsaw felling and processing at the stump, followed by yarding tree-length logs using a Koller K301-4 tower yarder. The logs were further processed and sorted into 1.8 m and 3.6 m log piles at the landing. We used a standard time study method to evaluate key variables that affect the productivity of thinning operations. The total stump-to-pile operational cost was 41,707 won/m3. The highest cost activity was the yarding phase which cost 20,083 won/m3 (48.2% of the total cost), followed by the costs of processing tree-length materials into marketable log lengths (12,143 won/m3; 29.1%), and then by the costs of sorting/piling the processed logs (5,039 won/m3; 12.1%). It was interesting to see that felling and processing trees at the stump had low costs at 1,315 won/m3 (3.2%) and 3,127 won/m3 (7.5%), respectively. We used the detailed time study data to develop regression equations which were to predict yarding productivity. Our analysis showed that harvesting system cost was highly sensitive to the number of logs, yarding distance and lateral distance per turn, respectively.

비철금속 선별 효율 향상을 위한 삼각 측량 센서의 사각지대 데이터 보완 기법

박선균(Sun Kyoon Park),조민재(Min Jae Cho),권은성(Eun Sung Kwon),박기환(Kyi Hwan Park) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.5

모니터 영상을 통한 원격제어 임업용 장비의 원목상차작업 생산성

최윤성 ( Yun-sung Choi ),조민재 ( Min-jae Cho ),오재헌 ( Jae-heun Oh ) 한국산업융합학회 2021 한국산업융합학회 논문집 Vol.24 No.3

Forest operations like timber harvesting have already been mechanized to reduce hazards to the worker and increase productivity. However, timber harvesting operations have still been considered potentially dangerous and expensive on steep terrain. Teleoperation, to control the timber harvesting machine at a distance, has the potential to improve the safety, productivity and efficiency of harvesting operations on steep terrain. To verify the effects of teleoperation, an experimental prototype system of a monitor image-based teleoperation was constructed using a real forestry machine. In this study, the productivity of excavator based grapple loader, which is one of the most used mechanized harvesting equipment in the timber production, was analyzed using time-study method. Factors like skill and age of operators, influencing loader productivity in timber loading operation were also evaluated by statistical analysis. Productivity analysis results showed that less experienced operators were more productive than experienced operators for teleoperation through image of monitors in the operator cabin. These results are shown to be unfamiliar to the monitor image and different loading operation pattern by operators. According to the results, the monitor image-based teleoperation system of forestry machine need to improve the resolution and installation position of camera. It was expected that additional studies will be needed for real-time remote control of forestry machine in the future.