• Journal of Ocean Engineering and Technology
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• v.22 no.6
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• pp.64-74
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• 2008

The flaw around a ROV (Remotely Operated Vehicle) has been numerically investigated to improve resistance performance by modifying the hull form of the ROV. For the base hull form considered in this study, the form drag rather than the friction drag is dominant to the total drag Subsequently, the surfaces on which the local pressure highly acts have been modified to produce the streamlined-shape. Based on the surface modification, seven different hull forms have been chosen as candidates for drag reduction. Among the candidates, the semi-sphericalized housing and the streamlined-bow achieved greatest drag reduction comparing with the others. Consequently, the hull form combined with the semi-sphericalized housing and the streamlined-bow gave approximately 17% drag reduction at the design velocity of 3 knots.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.3
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• pp.463-471
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• 2020

Recently, various tries to apply ROV (Remotely Operated Vehicle) into underwater are being developed. However, due to underwater environment uniqueness, the additional problem must be taken into account when designing an ROV for the inspection of the underwater structure. This is because a GPS-based information method cannot be applied, and the obtainable image is also dependent on the turbidity. Also, it is necessary to be able to satisfy waterproof and operating speeds in consideration of most practical application environments. This paper describes the design results of the ROV system for underwater structure inspection considering the above problems. The designed system applied INS / DVL for location recognition and was configured to support 3D mapping and stereo camera-based image information using sonar depending on visibility. To satisfy the waterproof, a pressure vessel using a composite material was applied. And over-actuated system using eight thrusters to maintain a stable posture and operating speed was applied also. The designed system was verified by structural analysis and flow analysis also.

• Journal of Ocean Engineering and Technology
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• v.34 no.3
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• pp.180-193
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• 2020

In this study, the end-effector tracking performance of a manipulator installed on a remotely operated vehicle (ROV) for autonomous underwater intervention is verified. The underwater manipulator is an ARM 7E MINI model produced by the ECA group, which consists of six joints and one gripper. Of the six joints of the manipulator, two are revolute joints and the other four are prismatic joints. Velocity control is used to control the manipulator with forward and inverse kinematics. When the manipulator approaches a target object, it is difficult for the ROV to maintain its position and posture, owing to various disturbances, such as the variation in both the center of mass and the reaction force resulting from the manipulator motion. Therefore, it is necessary to compensate for the influences and ensure the relative distance to the object. Simulations and experiments are performed to track the trajectory of a virtual object, and the tracking performance is verified from the results.

• Journal of information and communication convergence engineering
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• v.19 no.1
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• pp.61-66
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• 2021

An underwater remotely operated vehicle (ROV) has been implemented. It can inspect foreign substances through a CCD camera while the ROV is running in water. The maximum thrust of the ROV's running thruster is 139.3 N, allowing the ROV to move forward and backward at a running speed of 1.03 m/s underwater. The structural strength of the guard frame was analyzed when the ROV collided with a wall while traveling at a speed of 1.03 m/s underwater, and found to be safe. The maximum running speed of the ROV is 1.08 m/s and the working speed is 0.2 m/s in a 5.8-m deep-water wave pool, which satisfies the target performance. As the ROV traveled underwater at a speed of 0.2 m/s, the inspection camera was able to read characters that were 3 mm in width at a depth of 1.5 m, which meant it could sufficiently identify foreign objects in the water.

• The Journal of Korea Robotics Society
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• v.18 no.1
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• pp.82-87
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• 2023

This paper proposes a disturbance observer-based control for 6-DOF remotely operated underwater vehicles with model uncertainties. The sum of external disturbance and the forces generated from model parameters except for the inertial matrix of the hydrodynamic model is defined as a lumped disturbance in this paper. Then, the lumped disturbance caused by model uncertainties and the external forces is estimated using the disturbance observer. Fortunately, the disturbance observer is constructed as a linear form because all the elements of the inertial matrix of the hydrodynamic model are constants. To verify the proposed control scheme, we show that the actual lumped disturbance is similar to the estimated lumped disturbance obtained by the disturbance observer. Finally, the position tracking performance in the disturbance environment is confirmed through the comparative study with a traditional inverse dynamics PD controller.

• The Journal of Korea Robotics Society
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• v.19 no.1
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• pp.8-15
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• 2024

This paper proposes a linear model predictive control of 6-DOF remotely operated underwater vehicles using nonlinear robust internal-loop compensator (NRIC). First, we design a integrator embedded linear model prediction controller for a linear nominal model, and then let the real model follow the values calculated through forward dynamics. This work is carried out through an NRIC and in this process, modeling errors and external disturbance are compensated. This concept is similar to disturbance observer-based control, but it has the difference that H_∞ optimality is guaranteed. Finally, tracking results at trajectory containing the velocity discontinuity point and the position tracking performance in the disturbance environment is confirmed through the comparative study with a traditional inverse dynamics PD controller.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.11
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• pp.1973-1977
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• 2006

This paper reports the absolute position tracking algorithm of underwater vehicles such as ROV, AUV in global region by fusing sensor informations of IMU, DVL, USBL, DGPS etc. This algorithm is to be used in the position tracking of the 6,000m class deep-sea unmanned underwater vehicle, HEMIRE for scientific exploration.

• The Journal of Korea Robotics Society
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• v.15 no.1
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• pp.39-47
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• 2020

This paper presents a control and operation system for a remotely operated vehicle (ROV). The ROV used in the study was equipped with a manipulator and is being developed for underwater exploration and autonomous underwater working. Precision position and attitude control ability is essential for underwater operation using a manipulator. For propulsion, the ROV is equipped with eight thrusters, the number of those are more than six degrees-of-freedom. Four of them are in charge of surge, sway, and yaw motion, and the other four are responsible for heave, roll, and pitch motion. Therefore, it is more efficient to integrate the management of the thrusters rather than control them individually. In this paper, a thrust allocation method for thruster management is presented, and the design of a feedback controller using sensor data is described. The software for the ROV operation consists of a robot operating system that can efficiently process data between multiple hardware platforms. Through experimental analysis, the validity of the control system performance was verified.

• Proceedings of the KIEE Conference
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• 2007.04a
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• pp.319-321
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• 2007

This paper introduces a general overview of the 6000m class deep-sea ROV. Hemire and Henuvy. and then describes its motion control system. It is developed by Korea Ocean Research & Development Institute(KORDI) for 6 years since 2001. sponsored by the Ministry of Maritime Affairs and, Fisheries (MOMAF). Hemire is remotely operated by a fiber optic telemetry. where 6 thrusters are controlled by operator in manual mode and by auto depth control and auto heading control in auto mode. In this paper. operational mechanism of manual and automatic mode with some convenient functions for operator is desc.ribed. Finally, results of sea trial conducted at the Philippine sea where a depth is 5.770m are shown.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.9
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• pp.813-821
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• 2013

In this paper, we present the development of P-SURO II hybrid AUV (Autonomous Underwater Vehicle) which can be operated in both of AUV and ROV (Remotely Operated Vehicle) modes. In its AUV mode, the vehicle is supposed to carry out some of underwater missions which are difficult to be achieved in ROV mode due to the tether cable. To accomplish its missions such as inspection and maintenance of complex underwater structures in AUV mode, the vehicle is required to have high level of autonomy including environmental recognition, obstacle avoidance, autonomous navigation, and so on. In addition to its systematic development issues, some of algorithmic issues are also discussed in this paper. Various experimental studies are also presented to demonstrate these developed autonomy algorithms.