Abstract: “The nondominated sorting genetic algorithm with elitism (NSGA-II) is widely used due to its good performance on solving multiobjective optimization problems. In each iteration of NSGA-II, truncation selection is performed based on the rank and crowding distance of each solution. There are, however, drawbacks in this process. These drawbacks to some extent cause overlapping solutions in the population and have an affection on the spread of nondominated solutions, which reduces the diversity of the obtained solution set. In this paper, 4 causes for generation of the overlapping solutions are investigated firstly. A new technique for alleviating this phenomenon is incorporated to enhance the capability of NSGA-II. The improved algorithm is referred to as NSGA-II+ in this paper. In NSGA-II+, overlapping solutions are removed during the truncation selection from the merged population (which is a combination of parent population and offspring population) after ranking in each iteration. The”

Keywords: nondominated sorting genetic algorithm, overlapping solutions, truncation selection, composite wing structur