Ki-Yin Chang

Optimal Path Planning for Mobile Robot Navigation

Some optimal path planning algorithms for navigating mobile rectangular robot among obstacles and weighted regions are presented. The approach is based on a higher geometry maze routing algorithm. Starting from a top view of a workspace with obstacles, the so-called free workspace is first obtained by virtually expanding the obstacles in the image. After that, an 8-geomerty maze routing algorithm is applied to obtain an optimal collision-free path with linear time and space complexities. The proposed methods cannot only search an optimal path among various terrains but also find an optimal path for the 2-D piano movers problem with 3 DOF. Furthermore, the algorithm can be easily extended to the dynamic collision avoidance problem among multiple autonomous robots or path planning in the 3-D space.

A Fuzzy Logic Method for Collision Avoidance in Vessel Traffic Service

Currently Vessel Traffic Service (VTS) does not have enough technical capability to monitor a crowded surveillance area to maintain safety. Without an efficient alerting system, many marine accidents have occurred due to operator oversight. In this article, a new fuzzy logic method is proposed to add vessel collision avoidance capability to VTS/AIS systems for all potential collision ships in the surveillance area. Starting from the VTS standpoint and integrating AIS data into the Marine Geographic Information System (MGIS) as a platform, the calculations of ship domain and ship inertial force are utilized to generate models of a guarding ring and danger index. By this means, a precise prediction of collision time and position can be achieved using a marine GIS spatial analyst module. The proposed method is able to enhance the VTS operators decision-making abilities by providing a collision avoidance alerting system.

A method for searching optimal routes with collision avoidance on raster charts

Collision avoidance is an intensive discussion issue for navigation safety. This article introduces a new routing algorithm for finding optimal routes with collision detection and avoidance on raster charts or planes. After the required data structure of the raster chart is initialized, the maze routing algorithm is applied to obtain the particular route of each ship. Those ships that have potential to collide will be detected by simulating the particular routes with ship domains. The collision avoidance scheme can be achieved by using the collision-area-marking method with collision avoidance rules at sea. The algorithm has linear time and space complexities, and is sufficiently fast to perform real-time routing on the raster charts.

A 4-geometry maze router and its application on multiterminal nets

The maze routing problem is to find an optimal path between a given pair of cells on a grid plane. Lees algorithm and its variants, probably the most widely used maze routing method, fails to work in the 4-geometry of the grid plane. Our algorithm solves this problem by using a suitable data structure for uniform wave propagation in the 4-geometry, 8-geometry, etc. The algorithm guarantees finding an optimal path if it exists and has linear time and space complexities. Next, to solve the obstacle-avoiding rectilinear and 4-geometry Steiner tree problems, a heuristic algorithm is presented. The algorithm utilizes a cost accumulation scheme based on the maze router to determine the Torricelli vertices (points) for improving the quality of multiterminal nets. Our experimental results show that the algorithm works well in practice. Furthermore, using the 4-geometry router, path lengths can be significantly reduced up to 12&percent; compared to those in the rectilinear router.

A new maze routing approach for path planning of a mobile robot

A new path planning approach for a mobile robot among obstacles of arbitrary shape is presented. This approach is based on a higher geometry maze routing algorithm. Starting from a top view of a workspace with obstacles, the so-called free workspace is first obtained by virtually expanding the obstacles in the image. After that, the 8-geometry maze routing algorithm is applied to obtain a shortest collision-free path. The proposed method is not only able to search a shortest path with rotation scheme but also capable to rotate the robot configuration to pass a narrow passage intelligently. The time complexity of the algorithm is O(N), where N is the number of pixels in the free workspace. Furthermore, for many researchers who work on dynamic collision avoidance for multiple autonomous robots and optimal path searching among various terrains (weighted regions), the concept of this algorithm can be applied to solve these problems.

Route planning and cost analysis for travelling through the Arctic Northeast Passage using public 3D GIS

To plan undeveloped optimal routes between Asia and Europe via the Arctic Northeast Passages using a 3D geographic information system (GIS), voyage paths are simulated in a 3D visual form. This ensures that the distances are calculated accurately, and that other voyage data such as water depths, sea ice distribution, and seashore topology are also easily deciphered, giving a more direct and clear demonstration compared to simplified presentations on an Electronic Chart Display & Information System (ECDIS). This article also implements a higher-geometry maze router in ice zone areas to obtain the optimal path in relation to safety and costs. This article compares the optimal Arctic Northeast Passages with traditional routes through the Suez Canal for dynamic analyses of the cost efficiency (including time costs, fuel costs, and other factors) of travel between major ports in Asia and Europe. The average benefit assessment is around 30–45% in a bulk carrier comparison. Thus, a 3D GIS can easily obtain and demonstrate safe navigation routes, providing a very convenient tool for initial planning.

Optimal Interceptions on Two-Dimensional Grids with Obstacles

(Email: b0170@mail.ntou.edu.tw)This article presents efficient and practical methods for path planning of optimal intercep-tions on two-dimensional grids with obstacles, such as raster charts or non-distorted digitalmaps. The proposed methods search for optimal paths from sources to multiple moving-targets by a novel higher geometry wave propagation scheme in the grids, instead of thetraditional vector scheme in the graphs. Byintroducing a time-matching scheme, the optimalinterception paths from sources to all the moving-targets are obtained among the combi-nations with linear time and space complexities. Two optimal path planning methods formultiple one-to-one interceptions, the MIN-MAX and MIN-AVG, are applied to emulatethe real routing.KEY WORDS

An efficient method for single-facility location and path-connecting problems in a cell map

This article presents an efficient method for simultaneously finding both the Weber cell and optimal connective paths in a grid. As numerous barriers of arbitrary shape and weighted regions are distributed in the cell map of this research, the problem scenario is similar to working out a real-life facility location selection and path-routing problems in a geographical map. In this study, the Weber problem of finding a single-facility location from an accumulation cost table is generated by a grid wave propagation method (higher-geometry maze router). After finding the Weber point (cell), optimal connective paths with minimum total weighted cost are backtracked between the Weber location cell and the demand cells. This new computation algorithm with linear time and space complexity can be integrated as a spatial analytical function within GIS.

A study of the distribution of marine incidents in the harbours and waters surrounding Taiwan

This research aims to discover information underlying the historical records of marine incidents in order to develop an effective marine traffic management system and rescue resource allocation system in the harbours and waters surrounding Taiwan. Data were collected from the official records of the Taiwanese Ministry of Transportation and Communications and the Coast Guard Administration of Taiwan. Data analysis and Google Earth were utilized to determine the locations of the occurred incidents. The results revealed that on an annual basis, the proportion of marine incidents outside of harbours was much higher than the incidents that took place within harbours. The results also showed that the rate of increase for marine incidents significantly decreased outside of harbours, but increased within harbours, both for commercial vessels and fishing boats from 2005 to 2009. Certain events, such as collisions/contacts, groundings/standings, mechanical malfunctions/failures, and fires/explosions accounted for more than half of the occurred accidents. Finally, the identification of incident locations provides visual evidence to elucidate precisely where the problems are and where rescue resources should be optimally allocated. Recommendations and implications for marine traffic management policy were discussed.

Study on fuzzy GIS for navigation safety of fishing boats

ABSTRACT Maritime ship collisions involving fishing boats have often been reported, and the major factors have been human error and unpredictable conditions. This paper aims to create a set of collision-avoidance measures for operating fishing boats or a vessel traffic service by way of time and space management. It proposes a novel safe collision-avoidance safeguarding ring for navigational safety between operating fishing boats and merchant ships with a dummy automatic identification system (AIS) to enable fishing boats to establish a dynamic state when approaching ships under operation (fishing). The approach method utilises the maximum relative speed, sea state, and escape time as three linguistic input variables for fuzzy logic control application. After the radius of the safeguarding ring is obtained and shown on a marine geographic information systems (MGIS) platform, the danger index of two ships is evaluated based on the area difference calculated through the MGIS. The software was installed in the dummy AIS receivers of fishing boats for experimentation in a Taiwan harbour. It was able to enhance the collision-avoidance ability of the operating fishing boats effectively and reduce marine disasters involving fishing boats.