Browsing by Author "Schmid, Jorg Peter"

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    Optimising the passage through charted minefields by path planning and mine removal
    (Stellenbosch : Stellenbosch University, 2006-04) Schmid, Jorg Peter; Bekker, James; Stellenbosch University. Faculty of Engineering. Dept. of Industrial Engineering.
    ENGLISH ABSTRACT: Shipping is the lifeline to maritime nations. Therefore it is essential that approaches to harbours and other strategic areas are kept free of threats by sea mines. With the technological possibility of remotely surveying threatening sea minefields, it has become necessary to develop a method by which such a charted minefield can be transited with least risk to shipping. To achieve this, two areas of interest have to be addressed and the resulting questions solved. This thesis addresses that requirement by meeting the following objectives: - to propose a methodology by which the risk involved in transiting a minefield can be managed so that paths of acceptable risks can be taken through a minefield; - if acceptable paths do not exist, to develop a methodology by which the minimum number of mines can be identified for removal so that a sufficiently safe path is established. These objectives were met by following the approach outlined below: - defining the problem in the context of traditional and developing mine warfare and mine countermeasures; - clearly stating the problems that have to be solved; - investigating the enablers available to solve the problems; - selecting and motivating a suitable approach; - describing the background knowledge to the proposed solutions; - implementing the solutions in a useable computer application; - investigating the parameters that pertain to the solution and presenting the findings; - drawing conclusions from the results and insights obtained from exposure to the problem and the solution strategies. The presented methodology uniquely combines two methods of combinatorial optimisation to give an integrated solution to the two stated problems of quantifying a risk methodology and removing required mines. The methods use the well known shortest path algorithm, Dijkstra's Algorithm, and a Genetic Algorithm for the basis of the proposed solution. Also, elements of the principle of the Efficient Frontier Graph are integrated to illustrate the aspects of return versus risk. The solution to finding a safe path through a charted minefield is approached from two risk principles: - Finding a path that is optimised for minimum risk over the entire length of the path. Here risk is a function of the distance between the mine and the ship. - Defining a maximum allowable risk and minimising the path length. Here risk is translated into the closest distance that a ship is allowed to approach a mine with the areas closer than that, being declared out of bounds. The sea mine removal problem is solved primarily by using a Genetic Algorithm that bases the quality of a solution on a parameter obtained by applying the methodology developed for solving the problem of optimising a path. This is achieved by minimising the number of sea mines to be removed to create a safe path.