• Journal of Navigation and Port Research
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• v.33 no.5
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• pp.323-330
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• 2009

We have been developing an underwater robot for harbour construction using a parallel mechanism The robot is attached to the rope of a crane, which curries a large stone into the undersea The robot's yaw and pitch are controlled by hydraulic cylinders but its roll is uncontrollable. We mount propellers in both side of the robot to generate the roll motion This paper studies on the control for the roll motion of a underwater robot. A gyro-sensor is used to measure the angle in a roll motion We develop the dynamic model to describe the robot's roll motion by a second order non-linear system and identify the model parameters by recursive least square and adaptive identifier. PD control, recursive model based control and adaptive model based control are applied with the dynamic model which computes the control input to compensate disturbances. This paper introduces the underwater robot system and presents the simulated and experimental results of the proposed controller.

• Journal of Navigation and Port Research
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• v.42 no.3
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• pp.237-244
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• 2018

When underwater rubble leveling work is carried out by a robot, real-time information on the topography around the robot is required for remote control. If the topographical information with respect to the current position of the robot is displayed as a 3D graphic image, it allows the operator to plan the working schedules and to avoid accidents like rollovers. Up until now, the topographical recognition was conducted by multi-beam sonars, which were only used to assess the quality before and after the work and could not be used to provide real-time information for remote control. This research measures the force delivered to the bucket which presses the mound to determine whether contact is made or not, and the contact position is calculated by reading the cylinder length. A variable bang-bang control algorithm is applied to control the heavy robot arms for the positioning of the bucket. The proposed method allows operators to easily recognize the terrain and intuitively plan the working schedules by showing relatively 3-D gratifications with respect to the robot body. In addition, the operating patterns of a skilled operator are programmed for raking, pushing, moving, and measuring so that they are automatically applied to the underwater rubble leveling work of the robot.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.82-82
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• 2009

Although leakage at a low carbon steel pipe made by electrical resistance welding(ERW) was reported due to grooving corrosion, the cause for the corrosion has not yet been cleared. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the corrosion test carried out using the ERW carbon steel pipe by changed the water speed and heat input in a month. The level of dissolved oxygen is maintained 5~5.5mg/l(amount of dissolved oxygen in tap water). The water speed for corrosion test is 1m/s, 2m/s, 3m/s. As the results, grooving corrosion rate is increased cause by water speed in the pipe. In the case of the ERW pipe with more heat input, grooving corrosion rate is decreased. It is therefore that welding heat input should be controlled based on the carbon content of the pipe in order to improve the corrosion reistance of the ERW pipe.

• Korean Journal of Food Science and Technology
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• v.28 no.2
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• pp.324-329
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• 1996

In order to develop a novel dewatering process for soybean milk residue, hydraulic press with ohmic heating was built and its expression conditions were examined. The electric conductivity of raw soybean milk residue was 0.128 S/m and increased linearly with increasing temperature. Water content of the residue could be reduced to 74% with the conventional hydraulic press, but to less than 70% by applying ohmic heating to the hydraulic press. The most effective dewatering was achieved by applying alternative current with 5 kHz frequency at 60 V during expression. The solid content of the expressed liauid was markedly reduced from 10% to 3.3% by ohmic heating during expression. Temperature of the cake rose to above $95^{\circ}C$ during the dewatering due to ohmic heating.