A reactive GRASP metaheuristic for the container retrieval problem to reduce crane’s working time

A Coronavirus Optimization Algorithm for Solving the Container Retrieval Problem

“…Consequently, although the relocation operations are time-consuming and have to be avoided as much as possible, obtaining the solution with the minimum crane operating time, by seeking the sequence of operations with the minimum number of relocations, is not reliable [10]. The studies in [9,31,46] have already indicated that minimizing the number of relocations does not ensure the solution with the minimum operating time since the number of relocation operations and the crane operating time are not always proportionate. Thus, a few works deal with other optimization goals that differ from the number of relocations.…”

“…Thus, a few works deal with other optimization goals that differ from the number of relocations. In [8,21,32], the objective function is to minimize, respectively, the crane's trajectory, the fuel consumption, and the operating costs, while the studies in [2,9,10,22,23,26,29,31,46] address the crane's operating time.…”

“…For example, in [2], authors consider the crane operating time for picking up and placing down containers to be constant and independent from the number of tiers that are crossed in the vertical movement. In [22,23], when the crane is carrying or not carrying a container, the crane speed for a horizontal movement is the same in both cases, unlike [9,10,32]. Furthermore, [17] addresses the crane operating time where the crane's vertical travel time is not considered.…”

“…Despite the differences in the computation of the crane's operating time, some recent works [9,10,29,31,32,46] converge towards a more accurate calculation of operating time, recognizing the following aspects. The crane's operating time is computed using the crane speeds and the distances (horizontal and vertical) traveled by the crane for performing any operation.…”

Optimizing pre-processing and relocation moves in the Stochastic Container Relocation Problem

“…As a result, the stack to which a container is relocated does not have a big influence on the total relocation time of a container. There are a few articles in the literature in which Assumption 4 is relaxed and in which the objective is to minimize a weighted average of the number of relocation moves and the total working time of the crane (see, e.g., Lin, Lee, &Lee, 2015 andda Silva Firmino, de Abreu Silva, &Times, 2019 ). In a recent study, Voß and Schwarze (2019) show that if the crane's working time is the objective that is minimized, then also the number of relocation moves is close to the minimum number of relocation moves.…”