• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.3
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• pp.281-287
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• 2023

Establishing a ship's passage plan is an essential step before it starts to sail. The research related to the automatic generation of ship passage plans is attracting attention because of the development of maritime autonomous surface ships. In coastal water navigation, the land, islands, and navigation rules need to be considered. From the path planning algorithm's perspective, a ship's passage planning is a global path-planning problem. Because conventional global path-planning methods such as Dijkstra and A^* are time-consuming owing to the processes such as environmental modeling, it is difficult to modify a ship's passage plan during a voyage. Therefore, the D^* algorithm was used to address these problems. The starting point was near Busan New Port, and the destination was Ulsan Port. The navigable area was designated based on a combination of the ship trajectory data and grid in the target area. The initial path plan generated using the D^* algorithm was analyzed with 33 waypoints and a total distance of 113.946 km. The final path plan was simplified using the Douglas-Peucker algorithm. It was analyzed with a total distance of 110.156 km and 10 waypoints. This is approximately 3.05% less than the total distance of the initial passage plan of the ship. This study demonstrated the feasibility of automatically generating a path plan in coastal navigation for maritime autonomous surface ships using the D^* algorithm. Using the shortest distance-based path planning algorithm, the ship's fuel consumption and sailing time can be minimized.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.1
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• pp.58-66
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• 2009

Formation controller for multiple spacecrafts is designed based on a decentralized approach. The objective of the proposed controller is to make each spacecraft fly to the desired waypoints, while keeping the formation shape of multiple spacecrafts. To design the decentralized formation controller, the output feedback linearization technique using error functions for goal convergence and formation keeping is utilized for spacecraft dynamics. The primary contribution of this paper is to proposed optimal controller for formation flying based on the decentralized approach. To design the optimal controller, eigenvalue assignment technique is used. To verify the effectiveness of the proposed controller, numerical simulations are performed for three-dimensional waypoint-passing missions of multiple spacecrafts.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.676-687
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• 2015

Path planning algorithms are used to allow mobile robots to avoid obstacles and find ways from a start point to a target point. The general path planning algorithm focused on constructing of collision free path. However, a high continuous path can make smooth and efficiently movements. To improve the continuity of the path, the searched waypoints are connected by the proposed polynomial interpolation. The existing polynomial interpolation methods connect two points. In this paper, point groups are created with three points. The point groups have each polynomial. Polynomials are made by matching the differential values and simple matrix calculation. Membership functions are used to distribute the weight of each polynomial at overlapped sections. As a result, the path has $G^2$ continuity. In addition, the proposed method can analyze path numerically to obtain curvature and heading angle. Moreover, it does not require complex calculation and databases to save the created path.

• The Journal of Korea Robotics Society
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• v.5 no.4
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• pp.302-308
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• 2010

A gradient method can provide a global optimal path in indoor environments. However, the optimal path can be often generated in narrow areas despite a sufficient wide area which lead to safe navigation. This paper presents a novel approach to path planning for safe navigation of a mobile robot. The proposed algorithm extracts empty regions using a ray-casting method and then generates temporary waypoints in wider regions in order to reach the goal fast and safely. The experimental results show that the proposed method can generate paths in the wide regions in most cases and the robot can reach the goal safely at high speeds.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.2
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• pp.15-20
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• 2015

This paper introduces a new airspace design method for continuous climb operation (CCO). The optimization problem is formulated as Mixed-Integer Linear Program (MILP) to maximize the upper limits of altitude on the waypoints to facilitate continuous climb for aircraft. In the proposed method, the interactions with other flight procedures are considered as well as various aircraft flight performances. The proposed method is applied to one of the departure procedures of Incheon International Airport (ICN) to demonstrate its performances.

• Journal of Korea Multimedia Society
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• v.23 no.1
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• pp.102-110
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• 2020

This study covers exploration of seabed around Heuksando Island using hover drones. To do so, we inspected the terrain of the island and set autonomous flight waypoints on each area of the island's shores. Next, we designated seabed scan radius for drones. Then the drones fitted with laser sensor hover autonomously on their assigned area and acquire seabed data. Finally, we match the seabed data on all areas according to GPS. Our final goal is to make immersive VR maritime cultural map based on 『Jasan Urbo』.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.2
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• pp.12-22
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• 2009

This paper deals with the State-Dependent Riccati Equation (SDRE) Technique for the design of rotorcraft waypoint guidance. To generate the flight trajectory through multiple waypoints, we use the trigonometric spline. The controller design and its validation is based upon a level 2 simulation rotorcraft model and the designed SDRE controller is applied to the trajectory tracking problems. To verify the designed guidance law, the simulation environment of high fidelity rotorcraft model is developed using three independent PCs. This paper focuses on the validation of rotorcraft waypoint guidance law which is designed by using SDRE Controller.

• Journal of Institute of Control, Robotics and Systems
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• v.11 no.3
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• pp.240-245
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• 2005

In this paper, planar waypoint guidance synthesis for UAVs using the LQ optimal impact-angle-control guidance law is proposed. We prove that the energy-optimal control problem with the constraint of passing through the waypoints is equivalent to the problem of finding the optimal pass angles on each waypoint of the optimal impact-angle-control law. The optimal pass angles can be obtained as a numerical solution of the simple pass angle optimization problem that requires neither input parameterization nor constraints. The trajectory obtained by applying the optimal impact-angle-control law with these optimal pass angles becomes energy optimal.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.241-249
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• 2014

This paper presents a path planning algorithm of an autonomous vehicle (ADAM III) for collision avoidance in the presence of multiple obstacles. Under the requirements that a low-cost GPS is used and its computation should be completed with a sampling time of sub-second, heading angle estimation is proposed to improve performance degradation of its measurement and a hierarchical structure for path planning is used. Once it is decided that obstacle avoidance is necessary, the path planning consists in three steps: waypoint generation, trajectory candidate generation, and trajectory selection. While the waypoints and the corresponding trajectory candidates are generated based on position of obstacles, the final desired trajectory is determined with considerations of kinematic constraints as well as an optimal condition in a term of lateral deviation. Finally the proposed algorithm was validated experimentally through field tests and its demonstration was performed in Autonomous Vehicle Competition (AVC) 2013.

• International Journal of Aeronautical and Space Sciences
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• v.2 no.1
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• pp.93-102
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• 2001

Flight control design for the autonomous waypoint navigation of aircraft is presented in this study. The waypoints are defined in terms of desired longitude and latitude. The control design is conducted in longitudinal and lateral directions, respectively. The lateral control is based upon coordinated turn strategy for which no sideslip is allowed under the turning maneuver. The longitudinal control is mainly focused on altitude hold during navigation. Neural network control approach is applied to the altitude-hold mode control. Simulation of the proposed control strategy has been performed under various conditions. A graphical simulation tool was developed to visually demonstrate the control technique developed in this study. A method to simulate the gas turbine transient behavior is developed. The basic principles of the method.