• Journal of Institute of Control, Robotics and Systems
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• v.19 no.8
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• pp.702-708
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• 2013

Underwater TRN (Underwater Terrain Referenced Navigation) estimates an underwater vehicle state by measuring a distance between the vehicle and undersea terrain, and comparing it with the known terrain database. TRN belongs to absolute navigation methods, which are used to compensate a drift error of dead reckoning measurements such as IMU (Inertial Measurement Unit) or DVL (Doppler Velocity Log). However, underwater TRN is different to other absolute methods such as USBL (Ultra-Short Baseline) and LBL (Long Baseline), because TRN is independent of the external environment. As a magnetic-field-based navigation, TRN is a kind of geophysical navigation. This paper develops an EKF (Extended Kalman Filter) formulation for underwater TRN. A filter propagation part is composed by an inertial navigation system, and a filter update is executed with echo-sounder measurement. For large-initial-error cases, an adaptive EKF approach is also presented, to keep the filter be stable. At the end, simulation studies are given to verify the performance of the proposed TRN filter. With simplified sensor and terrain database models, the simulation results show that the underwater TRN could support conventional underwater navigation methods.

• Journal of Ocean Engineering and Technology
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• v.30 no.3
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• pp.221-226
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• 2016

An attitude controller for a 6-DOF hovering autonomous underwater vehicle (HAUV) is implemented. We add a vertical thruster, an underwater camera, a wireless communication device, and a DVL to the HAUV that was developed a year ago. The HAUV is composed of 5 thrusters, 2 servo-motors, and 4 apparatus parts. Two rotating thrusters control the surge, heave, and roll of the vehicle. The vertical thruster controls the pitch, and two horizontal thrusters control the sway and yaw of the vehicle. The HAUV’s movement in each direction is controlled by 6 PID controllers. Each PID controller controls the propulsive force and angle of a thruster. In a horizontal and vertical movement experiment, we showed the feasibility of the proposed controller by maintaining a given depth and heading angle of the HAUV.

• 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.

• The Journal of Korea Robotics Society
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• v.10 no.1
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• pp.1-8
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• 2015

This paper proposes a study for accurate surface localization system using DWT(Discrete Wavelet Transform) and GPS/INS fusion algorithm. Because the propagation in the underwater is not passed by characteristics of the medium unlike the ground, the sonar system like DVL is used instead of GPS. But since these systems are installed on the seafloor and operated, a long time is required for installation and navigation systems are limited outside of the range area. And it is difficult to estimate position in a three-dimensional considering the depth in actual marine environment. In this paper, before the development of underwater localization system, precisely estimated position system is proposed in a two-dimensional by developing surface localization system using removing noise and disturbance with DWT and relatively inexpensive GPS and INS sensor.

• The Journal of Korea Robotics Society
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• v.9 no.1
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• pp.28-38
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• 2014

This paper verifies the performance of Extended Kalman Filter(EKF) and MCL(Monte Carlo Localization) approach to localization of an underwater vehicle through experiments. Especially, the experiments use acoustic range sensor whose measurement accuracy and uncertainty is not yet proved. Along with localization, the experiment also discloses the uncertainty features of the range measurement such as bias and variance. The proposed localization method rejects outlier range data and the experiment shows that outlier rejection improves localization performance. It is as expected that the proposed method doesn't yield as precise location as those methods which use high priced DVL(Doppler Velocity Log), IMU(Inertial Measurement Unit), and high accuracy range sensors. However, it is noticeable that the proposed method can achieve the accuracy which is affordable for correction of accumulated dead reckoning error, even though it uses only range data of low reliability and accuracy.

• Journal of Ocean Engineering and Technology
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• v.30 no.5
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• pp.367-373
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• 2016

This paper describes the development of a navigation HILS (hardware in the loop simulation) system for an integrated navigation performance analysis of a large diameter unmanned underwater vehicle (LDUUV). The HILS system was used for the performance analysis of the LDUUV. When a conventional HILS system is used, it is not possible to calculate the velocity and position using an inertial navigation system (INS). To cope with this problem, an external acceleration was generated. To evaluate the proposed method, we compare the results of a Monte Carlo simulation and navigation HILS experiment.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.198-203
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• 2004

This paper describes a real-time control architecture for DUSAUV (Dual Use Semi-Autonomous Underwater Vehicle), which has been developed at Korea Research Institute of Ships & Ocean Engineering (KRISO), KORDI, for being a test-bed oj development of technologies for underwater navigation and manipulator operation. DUSAUV has three built-in computers, seven thrusters for 6 degree of freedom motion control, one 4-function electric manipulator, one pan/tilt unit for camera, one ballasting motor, built-in power source, and various sensors such as IMU, DVL, sonar, and so on. A supervisor control system for GUI and manipulator operation is mounted on the surface vessel and communicates with vehicle through a fiber optic link. Furthermore, QNX, one of real-time operating system, is ported on the built-in control and navigation computers of vehicle for real-time control purpose, while MicroSoft OS product is ported on the supervisor system for GUI programming convenience. A hierarchical control architecture which consist of three layers (application layer, real-time layer, and physical layer) has been developed for efficient control system of above complex underwater robotic system. The experimental results with implementation of the layered control architecture for various motion control of DUSAUV in a basin of KRISO is also provided.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.6
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• pp.33-42
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• 2010

This research propose a practical guidance system considering ocean currents in real sea operation. Optimality of generated path is not an issue in this paper. Way-points from start point to possible goal positions are selected by experienced human supervisors considering major ocean current axis. This paper also describes the implementation of a precise underwater navigation solution using multi-sensor fusion technique based on USBL, GPS, DVL and AHRS measurements in detail. To implement the precise, accurate and frequent underwater navigation solution, three strategies are chosen. The first one is the heading alignment angle identification to enhance the performance of standalone dead-reckoning algorithm. The second one is that absolute position is fused timely to prevent accumulation of integration error, where the absolute position can be selected between USBL and GPS considering sensor status. The third one is introduction of effective outlier rejection algorithm. The performance of the developed algorithm is verified with experimental data of mine disposal vehicle and deep-sea ROV.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.3
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• pp.108-118
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• 2017

This paper presents experimental results of realtime sonar-based SLAM (simultaneous localization and mapping) using probability-based landmark-recognition. The sonar-based SLAM is used for navigation of underwater robot. Inertial sensor as IMU (Inertial Measurement Unit) and DVL (Doppler Velocity Log) and external information from sonar image processing are fused by Extended Kalman Filter (EKF) technique to get the navigation information. The vehicle location is estimated by inertial sensor data, and it is corrected by sonar data which provides relative position between the vehicle and the landmark on the bottom of the basin. For the verification of the proposed method, the experiments were performed in a basin environment using an underwater robot, yShark.

• Development and Reproduction
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• v.11 no.3
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• pp.141-153
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• 2007

The Wnt signaling pathway regulates cell proliferation and differentiation during development of multicellular organisms and plays pivotal roles in the maintenance of homeostasis in adult tissues. Therefore misregulation of Wnt signaling could be a pathogenesis of diverse human diseases such as cancers. Recently, the list of diseases that may be linked to the misregulation of Wnt signaling has exploded and more people are getting interested in the way of controlling Wnt signaling. There are a lot of review papers, however, since most of them have focused on specific issues for experts in Wnt signaling it may be difficult for new comers to understand the overall background and current status of Wnt signaling. In this review, we present data and interpretations for the overall processes of Wnt signal transduction to understand the past and current status of Wnt signaling.