• Journal of the Korean Society for Precision Engineering
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• v.16 no.5 s.98
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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.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.4
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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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• v.11 no.2
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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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• s.10
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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.

• Korean Journal of Applied Biomechanics
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• v.19 no.3
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• pp.539-547
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• 2009

The purpose of this study was to investigate the changes of kinetic and kinematic parameters in obstacle gaits after 12 weeks of an aquatic exercise program. Eight female elders walked in four different heights of obstacles(0, 2.5, 5.1, & 15.2cm) on their self-selected speed. The ROM of hip was significantly increased after the aquatic exercise program. Swing and Stance duration were decreased. The step length was significantly increased and the step width was decreased. After the exercise program the clearance between the right foot and the top of obstacle(except 15.2cm) increased and the crossing speed was increased. The braking force, propulsive force, braking impulse, and propulsive impulse were significantly changed after the aquatic exercise program. The 12 weeks of the aquatic exercise program resulted in lower body strength and balance gains in female elders. The improvements were associated with changes in kinetic and kinematic parameters leading to an obstacle-crossing speed and a safer lower-limb control. The aquatic exercise program is suggested as an effective intervention to promote gait ability and prevent fall-related to the injuries.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.13-24
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• 1989

The geometrical characteristics of sculls which are in use for propulsion of Korean traditional row boats were briefly surveyed. A typical dimension of the scull was selected and prototype for test was prepared. Angular displacements and the force components at handle and pivoting point were measured when the scull was operated in moored condition by skilled fisherman. Time histories and trajectories of motion were analyzed with the force generated at the scull blade. It was found out that the thrust of the scull was generated mainly by reaction force. The direction of improvement for better rowing motion could be also suggested. Continued study on this topic in a self-propulsion condition will provide us another interesting informations and prepare a possibility of application in evaluating rowing motion of oar.