An Improved Ant Colony Algorithm for Placing-In and Taking-Out of Wagons in Branch-Shaped Sidings

The key of placing-in and taking-out operations of wagons is how to select a rational sequence, which is hard to solve. According to the analysis of characteristics of placing-in and taking-out operations of wagons in branch-shaped private sidings, we construct Hamilton graph of this problem, and convert this problem into searching Hamilton loop of minimum weight. In this paper, we present an improved ant colony optimization (ACO) algorithm for such a problem. The proposed ACO algorithm has several features, including introducing upper and lower bounds to the values of pheromone trail, and applying local search and modified global search strategy. The improved algorithm is experimented on branch-shaped sidings problem with 6 nodes and shows its advantage over conventional ant colony algorithm. For the large scale branch-shaped sidings problems, this proposed algorithm can save much time.