• Journal of Advanced Navigation Technology
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• v.25 no.3
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• pp.177-184
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• 2021

This paper proposes an assessment method using probability-based index for safe and successful underwater docking of autonomous underwater vehicles(AUVs) to the docking stations(DSs). The proposed method assesses the probability of docking according to the degree to which the state of the AUV is consistent with the state criteria for docking. The assessment is performed within a specific area considering the kinematic constraints and docking plans of the AUV. The assessment process is defining probability density function, calculating probabilities for reaching the docking station according to the difference to position and heading criteria, and computing the probability-based index in real-time. We verify the validity of the proposed method through analyzing the data acquired on operation test.

• Journal of KIISE:Software and Applications
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• v.34 no.3
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• pp.235-245
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• 2007

UUV(Unmanned Underwater Vehicle) should possess an intelligent control software performing intellectual faculties such as cognition, decision and action which are parts of domain expert's ability, because unmanned underwater robot navigates in the hazardous environment where human being can not access directly. In this paper, we suggest a RVC intelligent system architecture which is generally available for unmanned vehicle and develope an autonomous navigation system for UUV, which consists of collision avoidance system, path planning system, and collision-risk computation system. We present an obstacle avoidance algorithm using fuzzy relational products for the collision avoidance system, which guarantees the safety and optimality in view of traversing path. Also, we present a new path-planning algorithm using poly-line for the path planning system. In order to verify the performance of suggested autonomous navigation system, we develop a simulation system, which consists of environment manager, object, and 3-D viewer.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.4
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• pp.476-482
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• 2010

In this paper, we propose a robust path tracking control method for autonomous underwater vehicle with variable speed. The proposed path tracking controller consists of a kinematic controller and a dynamic controller. First, the kinematic controller computes the surge speed and yaw rate to follow the reference path with variable speed. Then the dynamic controller controls the thrust force and yaw torque to move the AUV actually. In the dynamic control, we assume that the sway speed is a disturbance. In addition the dynamic controller is designed based on sliding mode conrol. We also demonstrate the stability of the proposed control method by Lyapunov stability theory. Finally, simulation results illustrate the performance of the proposed control method.

• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.24-34
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• 2006

Hydrodynamic coefficients strongly affect the dynamic performance of an AUV. Thus, it is important to know the true values of these coefficients, in order to accurately simulate the AUV's dynamic performance. Although these coefficients are generally obtained experimentally, such as through the PMM test, the measured values are not completely reliable because of experimental difficulties and errors. Another approach, by which these coefficients can be obtained, is the observer method, in which a model-based estimation algorithm estimates the coefficients. In this paper, the hydrodynamic coefficients are estimated using two nonlinear observers: a sliding mode observer and an extended Kalman filter. Their performances are evaluated in Matlab simulations, by comparing the estimated coefficients obtained from the two observer methods, with the experimental values as determined from the PMM test. A sliding mode controller is constructed for the diving and steering maneuver by using the estimated coefficients. It is demonstrated that the controller, applied with the estimated values, maintains the desired depth and path with sufficient accuracy.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.9
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• pp.797-804
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• 2013

In this paper, a study of a new hovering six dof underwater robot with redundant horizontal thrusters, titled HAUV (hovering AUV), is presented. The results of study on the structure design, deployment of thrusters, and development of the developed control system of the AUV was presented. For the HAUV structure, a structure design and an analysis of the thrusting system was performed. For navigation, a sensor fusion board which can proceed various sensor signals to identify correct positions and speeds was developed and a total control system including EKF (Extended Kalman Filter) was designed. Rolling, pitching and depth control tests of the HAUV have been performed, and relatively small angle error and depth tracking error results were shown.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.51-55
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• 1997

This study is devote to developing navigation filter for detecting sensor failure in multi-sensor navigation system. In multi-sensor navigation system, Kalman filter is generally used to fuse data of each sensors. Sensor failure is fatal in case that the sensor is used as external measurement of Kalman filter therefore detection and recovery of sensor failure is one the important feature of navigation filter. Generally each sensors have its specific feature in measuring navigational information. Fuzzy theory is proposed to detect external sensor failure and provide valid external measurement to Kalman filter avoiding filter divergence and instability. This idea is applied to Autonomous Underwater Vehicle(AUV) which has two navigation sensor i. e self contained inertial sensor and acoustic external sensor. 2 dimensional simulation result shows acceptable failure detection and recovery

• Advances in Computational Design
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• v.5 no.3
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• pp.233-260
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• 2020

The main purpose to introduce model based controller in proposed control technique is to provide better and fast learning of the floating dynamics by means of fuzzy logic controller and also cancelling effect of nonlinear terms of the system. An iterative adaptive dynamic programming algorithm is proposed to deal with the optimal trajectory-tracking control problems for autonomous underwater vehicle (AUV). The optimal tracking control problem is converted into an optimal regulation problem by system transformation. Then the optimal regulation problem is solved by the policy iteration adaptive dynamic programming algorithm. Finally, simulation example is given to show the performance of the iterative adaptive dynamic programming algorithm.

• The Journal of Korea Robotics Society
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• v.18 no.4
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• pp.472-480
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• 2023

This paper describes the development of a test-equipment for the pre-verification of navigation performance in cluster-based AUVs (Autonomous Underwater Vehicle). In the development of an AUV, conducting hardware and software development sequentially is not efficient due to the limited research and development period. Therefore, in order to reduce the overall development time and achieve successful development results, it is essential to pre-validate the navigation system and navigation algorithms. Accordingly, this paper explains the test-equipment for pre-verification of navigation performance, and ultimately confirms the stability of the navigation system and the performance of the navigation algorithms through the analysis of five types of navigation sensor data stored during real-sea experiments. The results demonstrate that through the development and verification of the test-equipment, it is possible to shorten the overall development period and improvement of product quality in the process of developing multiple AUVs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.179-189
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• 2000

Recently, due to the increasing interests in deep sea development, all possible efforts to the development of underwater unmanned working vehicles such as AUV(Autonomous Underwater Vehicle) or underwater robot are exerted. This paper proposes a new efficient acoustic-based underwater image data communication system, which ensures a certain level of maximum throughput regardless of the propagation delay of ultrasonic and allowsfast data transmission through the multiple ultrasonic communication channel. Proposed system consists of an acoustic transducer which operates at 136kHz center frequency and it's 10kHz bandwidth, pre-amplifier, $\pi/4 QPSK$(Quadrature Phase Shift Keying) modulation/demodu-lation method, image compressing method using JPEG technique and modified Stop & Wait protocol. The experimental result of the system make it possible to transfer the underwater image as a high throughput at the basin test. The results of test are also verified which allows to desirable transmission performance compared with the existing developed system and the possibility to put the practical use of survey and investigation in the water.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.201-204
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• 2002

This paper describes the hydrodynamic characteristics of a test-bed AUV SNUUV-I constructed at Seoul National University. The main purpose of the AUV is to carry out fundamental control and hydrodynamic experiments. Its configuration is basically a long cylinder of 1.35m in length and 0.25m in diameter with delta-type wings near its rear end. On the edge of each wing, a thruster of 1/4HP is mounted, which is used for both drive and turn the vehicle for horizontal movement as the output control power is varied. A pair of control surfaces installed near its font part generates pitch moments for vertical movement. The 6 DOF mathematical model of SNUUV-I contains hydrodynamic forces and moments expressed in terms of a set of hydrodynamic coefficients. These coefficients can be classified into linear damping coefficients, linear inertial coefficients and nonlinear damping coefficients. It is important to estimate the exact value of these coefficients to control the vehicle precisely. Among these, the linear coefficients are known to affect the motion of the vehicle dominantly. The linear damping coefficients are estimated by using Extended Kalman Filter. The responses of the vehicle to input signals are used to estimate the hydrodynamic coefficients, which can be inferred from output signals measured from an IMU (inertial motion unit) sensor, while the linear inertial coefficients are calculated by a potential code. By using these coefficients estimated as described above, a simulation program is constructed using Matlab.