• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.637-641
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• 1991

One of the most difficult problems in depth control for underwater vehicle is the effect of seaway disturbance. When a underwater vehicle operates in a near surface environment, the seaway generates essentially two types of stochastic disturbances that influence the boat notion. One component of the seaway forces is of large magnitude with a relatively narrow-band, first order component. The other component is generally of somewhat smaller magnitude, second order component. Since the magnitude of the first order component is generally such greater than the compensating force that can be generating by the planes, it is undesirable for the controller to generate a control command. In this paper, we used LPC(Linear Predictive Coding) processing to uncontrollable seaway disturbance. This method can be used extensively in sensor signal processing of underwater vehicles.

• 한국전자통신학회논문지
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• 제1권1호
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• pp.42-48
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• 2006

본 논문에서는 해저의 이동체 사이의 효과적인 다중 초음파 데이타 통신을 위한다중 초음파 접속제어 프로토콜을 제안 하였다. 논리계층에서의 프로토콜은 모선과 수중 이동체간에 다중 채널 통신이 가능하고 논리계층간의 peer to peer 통신이 가능함을 확인하였다. 본 논문에서 제안된 접속제어 프로토콜은 수중 통신 시스템의 여러 가지 수중 물리적 환경에서 전파지연 시간에 무관하게 최대 수율을 보장하고 서로 다른 주파수 대역을 사용하는 다중 전송채널을 이용하여 수중에서 고속 데이터 전송의 가능함을 확인하였다.

• 제어로봇시스템학회논문지
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• 제3권3호
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• pp.227-237
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• 1997

Autonomous Underwater Vehicles(AUVs) have become an important tool for various purposes in subsea: inspection, recovery, construction, etc., and the development of autonomous control system is luglay desirable- thete zffe many problems associated with designing the control system for AUV due to unknown underwater envimn-Tnent, the possibility of subsystem failures, and unpredictable changes in the dynamics of the vehicle. In this paper, an autonomous control system based on the intelligent control theory to enhance operation efficiency of the ALTV is presented. The control system has a hierarchical structure which consists of mission planning level, mission control level, navigation level, and execution level. The performance of the control system is investigated by computer simulation. The results show that the proposed control system can be applied successfully to the AUV in spite of the possibility of failures in the vehicle and the collision hazard in the sea environment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2619-2621
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• 2001

This study proposes a new efficient MAC(media access control) protocol to establish the ultrasonic communication network for under water vehicles, which ensures a certain level of maximum throughput regardless of the propagation delay of ultrasonic and allows fast data transmission through the multiple ultrasonic communication channel. In this study, a media access control protocol for underwater communication network that allows 'peer-to-peer' communication between a surface ship and multiple underwater system is designed, and the proposed control protocol is implementde for its verification.

• 로봇학회논문지
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• 제18권1호
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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.

• Ocean Systems Engineering
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• 제13권3호
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• pp.269-286
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• 2023

Autonomous Underwater Gliders (AUGs) are a type of Underwater Vehicles that move without the help of a standard propeller. Gliders use buoyancy engines to vary their weight or buoyancy and traverse with the help of the Lift and Drag forces developed from the fuselage and the wings. The Lift and Drag Coefficients, also called Hydrodynamic coefficients (HDCs) play a major role in glider dynamics. This paper examines the effect of the different types of glider fuselages based on the bodies of revolution (BOR) of NACA sections. The HDCs of the glider fuselages are numerically estimated at a low-speed regime (10⁵ Reynolds Number) using Computational Fluid Dynamics (CFD). The methodology is validated using published literature, and the results of CFD are discussed for possible application in the estimation of glider turning motion.

• 로봇학회논문지
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• 제19권1호
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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.

• 제어로봇시스템학회논문지
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• 제21권4호
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• pp.349-355
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• 2015

Underwater robots generally show better performances for tasks than humans under certain underwater constraints such as. high pressure, limited light, etc. To properly diagnose in an underwater environment using remotely operated underwater vehicles, it is important to keep autonomously its own position and orientation in order to avoid additional control efforts. In this paper, we propose an efficient method to assist in the operation for the various disturbances of a remotely operated vehicle for the diagnosis of underwater structures. The conventional AHRS-based bearing estimation system did not work well due to incorrect measurements caused by the hard-iron effect when the robot is approaching a ferromagnetic structure. To overcome this drawback, we propose a sensor fusion algorithm with the camera and AHRS for estimating the pose of the ROV. However, the image information in the underwater environment is often unreliable and blurred by turbidity or suspended solids. Thus, we suggest an efficient method for fusing the vision sensor and the AHRS with a criterion which is the amount of blur in the image. To evaluate the amount of blur, we adopt two methods: one is the quantification of high frequency components using the power spectrum density analysis of 2D discrete Fourier transformed image, and the other is identifying the blur parameter based on cepstrum analysis. We evaluate the performance of the robustness of the visual odometry and blur estimation methods according to the change of light and distance. We verify that the blur estimation method based on cepstrum analysis shows a better performance through the experiments.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.142-148
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• 2002

Autonomous underwater vehicles (AUVs) are unmanned underwater vessels to investigate sea environments, oceanography and deep-sea resources autonomously. Docking systems are required to increase the capability of the AUVs to recharge the batteries and to transmit data in real time for specific underwater works, such as repeated jobs at sea bed. This paper presents a visual servo control system for an AUV to dock into an underwater station with a camera mounted at the nose center of the AUV. To make the visual servo control system, this paper derives an optical flow model of a camera, where the projected motions of the image plane are described with the rotational and translational velocities of the AUV. This paper combines the optical flow equation of the camera with the AUVs equation of motion, and derives a state equation for the visual servoing AUV. This paper proposes a discrete-time MIMO controller minimizing a cost function. The control inputs of the AUV are automatically generated with the projected target position on the CCD plane of the camera and with the AUVs motion. To demonstrate the effectiveness of the modeling and the control law of the visual servoing AUV, simulations on docking the AUV to a target station are performed with the 6-dof nonlinear equations of REMUS AUV and a CCD camera.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.338-339
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• 2010