• Proceedings of KOSOMES biannual meeting
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• 2003.11a
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• pp.123-126
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• 2003

In the present paper, the analysis is on the safe navigation between ships moving each other in restricted waterways under the external force, such as wind or current The numerical simulation of manoeuvring motion was carried out to propose an appropriate safe speed and distance between ships, which is required to avoid marine disasters from the viewpoint of marine safety. From the inspection q this investigation, it indicates the following result In case of proximal navigation between ships under the wind and current, the low-speed vessel is potentially hazardous because the rudder force if low-speed vessel needed for steady-state course-keeping is not sufficient, compared to the high-speed vessel The manoeuvring characteristic based on this investigation will be very useful for keeping the safety of navigation from the practical point of ships design and traffic control in restricted waterways.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.216-217
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• 2005

This paper presents an integrated navagation control concept for underwater vehicles under high speed navigation circumstance. First of all, in order to control an underwater vehicle with respect to automatic navigation, an integrated navigation control method is suggested in view of synchronous control for course keeping, diving and depth control. An exact nonlinear model equation with six-degree-of-freedom is derived for control algorithm. To identify various hydrodynamic coefficients of the equation, an experimental approach is introduced and results are demonstrated for MANTA type model.

• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.191-197
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• 2006

In the paper propose a sensorless sliding mode control method of an induction motor using an adaptive speed control. The control objective is apply to adaptive speed observer instead of a encoder and to remove errors using the sliding mode current controller by parameters variation and disturbances that include the current controller. A stability of the sliding mode current controller and the adaptive speed observer using a design controller is guaranteed by the Lyapunov stability criterion. The performance of the proposed control system is demonstrated by simulation using the matlab silmulink and experimental results using induction motor show that the proposed method can apply an induction motor control.

• Journal of Advanced Navigation Technology
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• v.24 no.2
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• pp.101-106
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• 2020

In order to smoothly control the speed of the induction motor, it is necessary to obtain the required rotor speed information. In order to obtain the speed information, it must be obtained using a sensor, but it can also be obtained using an appropriate algorithm without using a sensor. In order to obtain speed information, a system was designed using a model reference adaptive system (MARS). Indirect vector control, one of the speed control methods of induction motors, was calculated from the motor current and rotor parameter values. The method of obtaining the position information of the magnetic flux by combining the slip frequency with the rotor speed was used. It is possible to simply perform instantaneous current control in a wide speed range without actual magnetic flux information, and has the advantage that the structure of the controller is simple. Therefore, in this paper, the control system was constructed based on the indirect vector control method, and the speed control system of the induction motor was developed by estimating the required rotor speed information as an intelligent algorithm developed without using it as a sensor.

• Journal of Navigation and Port Research
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• v.47 no.2
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• pp.49-56
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• 2023

As interest in autonomous ships continues to grow, researchers around the world are dedicating themselves to the development of relevant technologies. However, these technologies are not yet perfect. Several technical problems remain unresolved. To address these problems, this study presents the implementation of a ship trajectory algorithm for group navigation, where followers can navigate by following the trajectory of a leader. The algorithm works by storing the leader's trajectory as a follow-point and by calculating the azimuth using the line-of-sight guidance law to reach it. A course-keeping controller based on PD control is implemented to follow the target course and a speed control algorithm is designed to prevent collisions. Sea experiments were conducted using 1 m class small RC model boats to verify the proposed algorithm. The follower successfully navigated by following the leader's trajectory and maintained the designated distance to the forward boat. This study is significant in that it implements an algorithm for the follower to follow the trajectory of the leader rather than directly following it as in conventional methods, and verifies it through sea experiments.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.1
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• pp.17-26
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• 2017

Latency occurs in RTK, where the measured position actually outputs past position when compared to the measured time. This latency has an adverse effect on the navigation accuracy. In the present study, a system that estimates the latency of RTK and compensates the position error induced by the latency was implemented. To estimate the latency, the speed obtained from an odometer and the speed calculated from the position change of RTK were used. The latency was estimated with a modified correlator where the speed from odometer is shifted by a sample until to find best fit with speed from RTK. To compensate the position error induced by the latency, the current position was calculated from the speed and heading of RTK. To evaluate the performance of the implemented method, the data obtained from an actual vehicle was applied to the implemented system. The results of the experiment showed that the latency could be estimated with an error of less than 12 ms. The minimum data acquisition time for the stable estimation of the latency was up to 55 seconds. In addition, when the position was compensated based on the estimated latency, the position error decreased by at least 53.6% compared with that before the compensation.

• Journal of the Korean Institute of Navigation
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• v.3 no.2
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• pp.21-30
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• 1979

Echo sounder and Doppler sonar are to theultra-sonic transducers for measuring the depth and the ship's speed respectively. To measure the depth and speed with a single transducer, it is required to control the ultra-sonic beam to optional direction. In the past, the direction of the transducer itself is varied, but such a method provoked much problems in the mechanical design of the equipment. This paper deals with the method to control beam direciton by the phase control of the plural arrangement of transducers, and the results are studied by a computer simulation. The remarkable results of the study is condensed as follows; 1. The greater the interval of arrangement between transducers, the sharper the radiation pattern is, but in this case, the level of undesired sidelobe is also increased. 2. The control of radiation pattern up to 60 degree can be achieved by an adequate arrangement of more than 10 transducers. 3. It is shown that a simultaneous measurement of both depth and speed can be achieved by alternating directivity of the pulse by the method proposed in this paper.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.5
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• pp.444-449
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• 2006

Path planning is a key element in navigation of a mobile robot. Several algorithms such as a gradient method have been successfully implemented so for. Although the gradient method can provide the global optimal path, it computes the navigation function over the whole environment at all times, which result in high computational cost. This paper proposes a high-speed path planning scheme, called a gradient method with topological information, in which the search space for computation of a navigation function can be remarkably reduced by exploiting the characteristics of the topological information reflecting the topology of the navigation path. The computing time of the gradient method with topological information can therefore be significantly decreased without losing the global optimality. This reduced path update period allows the mobile robot to find a collision-free path even in the dynamic environment.

• Journal of Advanced Navigation Technology
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• v.16 no.6
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• pp.1123-1133
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• 2012

This study configuration Vector Control System which is stable and has outstanding Dynamic Characteristics in Very Low Speed Region and Low Speed Region, and proposes Instantaneous Speed Observer and Very Low Speed Control method and vector control system of the speed estimation a using Reduced-Dimensional State Observer. The Observer proposed in this system, by appling Reduced-Dimensional State Observer to Load-Torque estimation and using for speed estimation, implements system composition simply and is capable of accurate Instantaneous Speed estimation in Very Low Speed Region. Also, this study reduces influence by System Noise and suggests an induction motor speed control system which is effective in Load Disturbance, modeling error, estimation noise and so on without changing pole of an Observer.

• Journal of Advanced Navigation Technology
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• v.15 no.1
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• pp.25-31
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• 2011

Recently NMEA 2000 protocol is familiarized as a standard real time instrument network of SOLAS ship. This paper is studied to develop NMEA 2000 based two-dimensional ultrasonic anemometer which is core device for navigation as a sensor of wind speed and direction using ultrasonic including temperature and barometer. Developed system is connected to NMEA 2000 network which is composed of various kinds of merchandised NMEA 2000 device such as depth gauge, speed gauge, GPS device etc. to test connectivity with other NMEA 2000 device and functional test are carried out as weather station in comparison with other merchandised weather station which are developed advanced foreign company to ascertain usability as a weather station on board.