• 한국정밀공학회지
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• 제16권5호통권98호
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• pp.151-159
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• 1999

A self-propulsive polishing robot is proposed as a method which automates a floor polisher. The proposed robot with two rotary brushes does not require any mechanism such as wheels to obtain driving forces. When the robot polishes a floor with its two brushes rotating, friction forces occur between the two brushes and the floor. These friction forces are used to move the robot. Thus, the robot can move in any direction by controlling the two rotary brushes properly. In this paper, firstly a dynamics model of a brush is presented. It computes the friction force between the brush and the floor. Secondly, the dynamics of the proposed robot is presented by using the bush dynamics. Finally, the inverse dynamics is solved for the basic motions, such as the forward, backward, leftward, rightward motions and the pure rotaion. This paper will contribute to realize a self-propulsive polishing robot as proposed above, In addition, this paper will give basic ideas to automate the concrete floor finishing trowel, because its basic idea for motion is similar to that of the proposed robot.

• 제어로봇시스템학회논문지
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• 제5권4호
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• pp.454-461
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• 1999

A concrete floor trowel machine, developed in the U.S in 1990's, consists of only two rotary trowels, and doesn't need any other mechanism for motion such as wheels. When the machine flattens a concrete floor with its rotary trowels, the machine can move in any direction by utilizing the unbalanced friction forces occurring between the rotary wheels and the floor when the trowels are tilted in appropriate directions. In order to automate the trowels machine, this paper proposed the self-propulsive concrete finishing trowel robot which has twin trowels. For the control of the robot, this paper discussed the following. Firstly, the dynamics model of the driving frictional force applied on each trowel from the floor is derived. Secondly, the relationship between the driving force for the robot and the control variable of the robot is derived. Finally, the basic motion of the robot are realized by using the obtained relationship. This paper figures out how the concrete floor finishing robot with tow trowels moves and will contribute to realizing it.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.883-898
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• 2019

This paper employs computational tools to predict power increase (or speed loss) and propulsion performances in waves of KVLCC2. Two-phase unsteady Reynolds averaged Navier-Stokes equations have been solved using finite volume method; and a realizable k-ε model has been applied for the turbulent closure. The free-surface is obtained by solving a VOF equation. Sliding mesh method is applied to simulate the flow around an operating propeller. Towing and self-propulsion computations in calm water are carried out to obtain the towing force, propeller rotating speed, thrust and torque at the self-propulsion point. Towing computations in waves are performed to obtain the added resistance. The regular short head waves of λ/LPP = 0.6 with 4 wave steepness of H/λ = 0.007, 0.017, 0.023 and 0.033 are taken into account. Four methods to predict speed-power relationship in waves are discussed; Taylor expansion, direct powering, load variation, resistance and thrust identity methods. In the load variation method, the revised ITTC-78 method based on the 'thrust identity' is utilized to predict propulsive performances in full scale. The propulsion performances in waves including propeller rotating speed, thrust, torque, thrust deduction and wake fraction, propeller advance coefficient, hull, propeller open water, relative rotative and propulsive efficiencies, and delivered power are investigated.

• 한국기계연구소 소보
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• 통권10호
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• pp.49-62
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• 1983

A series of model tests on a container ship in waves was executed at the Experimental Towing Tank of Ship Research Station, KIMM. This paper presents the results of resistance, self-propulsion, propeller open-water and ship motion tests in regular head waves. Firstly, the experimental results of ship motion measured on a towed model and a self-propelled model were compared with those of Japanese results showing fairly good agreements. Secondly, the results of resistance and propulsion tests were analyzed and the data of added resistance, thrust increase, torque increase, revolution increase and self-propulsion factors in waves were presented. Also the diffraction force measured on a fixed model in waves was analyzed. Finally, this report shows the propeller characteristics in calm water based on propeller immersion and in regular waves based on wave length.

• 한국운동역학회지
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• 제19권3호
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• pp.539-547
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• 2009

본 연구의 목적은 낙상 예방을 위한 12주간의 수중 운동 수행 후 장애물 보행의 특성을 운동학 및 운동역학적으로 분석하는 것이다. 여성 노인 8명이 참여하였으며, 대상자들은 수중 운동 전 후에 네 높이의 장애물(0, 2.5, 5.1, & 15.2cm)을 자기선호 속도로 넘었다. 수중 운동 수행 후 고관절의 최대각, 최소각, ROM(Range Of Motion)이 유의하게 증가하였으며, Swing 과 Stance 국면에서 소요시간은 줄어들었다. 수중 운동 후 모든 높이에서 보폭은 유의하게 증가하였고, 보간은 줄어들었다. 수중 운동 후 장애물을 넘는 순간 장애물과 오른발 사이의 수직 최단거리는 증가하였고(15.2cm 장애물 제외), 장애물을 넘는 속도는 증가하였다. 수중 운동 수행 후 제동력, 추진력, 제동 운동량, 추진 운동량은 통계적으로 유의하게 변화하였다. 12주간의 수중 운동은 여성 노인의 근력과 평형성을 향상시켰으며 이는 낙상과 관련된 장애물 보행의 운동학 및 운동역학적 변인의 변화를 가져와 여성 노인들이 장애물을 안전하고 신속하게 넘을 수 있었다. 따라서 노인에게 보행 능력 향상과 낙상 예방 운동으로 수중 운동이 추천된다.

• 대한조선학회지
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• 제26권2호
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• pp.13-24
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• 1989

인력(人力)을 추진동력(推進動力)으로 하는 소형선(小型船)에서 쓰이고 있는 선미노(船尾櫓)의 기하학적(幾何學的)인 특성(特性)과 조작방법(操作方法)이 오래전부터 전승(傳承)되어 왔으나 그 내용이 구체적으로 밝혀져 있지 않음은 물론이고 추력발생기구(推力發生機構)에 대한 과학적(科學的)인 조사(調査)가 이루어진 바 없다. 선미노(船尾櫓)의 사용실태(使用實態)를 조사(調査)하여 기하학적(幾何學的)인 특성(特性)을 조사(調査)하고 숙련(熟練)된 擄手(櫓手)가 선미노(船尾櫓)를 조작(操作)할 때 노(櫓)의 운동(運動)을 6자유도운동계측(自由度運動計測) 장치(裝置)로 측정(測定)하였다. 또한 노(櫓)의 손잡이 부분과 노운동(櫓運動)의 회전중심(回轉中心)이 되는 노봉(櫓棒)위치에 검력계(檢力計)를 설계제작(設計製作)하여 삽입설치(揷入設置)함으로서 노(櫓)가 작동중(作動中)일 때의 검력계(檢力計)의 출력(出力)을 조사(調査)하였다. 계측된 운동과 검력계출력을 해석함으로서 노의 운동(運動)과 추력(推力)사이의 상관관계(相關關係)를 밝히고저 하였다. 얻어진 연구방법론(硏究方法論)을 확장하면 노운동(櫓運動)의 최적조건(最適條件) 구명(究明)에도 활용(活用)될 수 있을 것이며 선측노(船側櫓)를 쓰는 조정(槽艇)에서도 활용될 수 있을 것이다.