Overhead-hoist-transporters (OHTs) have become the most appropriate tools to transport wafer lots between inter-bay and intra-bay in united layouts of automated material handling systems (AMHSs) in 300 mm semiconducto...Overhead-hoist-transporters (OHTs) have become the most appropriate tools to transport wafer lots between inter-bay and intra-bay in united layouts of automated material handling systems (AMHSs) in 300 mm semiconductor wafer fabrications. To obtain a conflict-free scheduling solution, an intelligent multi-agent-based control system framework was built to support the AMHSs. And corresponding algorithms and rules were proposed to implement cooperation among agents. On the basis of the mentioned above, a time-constraint-based heuristic scheduling algorithm was presented to support the routing decision agent in searching the conflict-free shortest path. In the construction of the algorithm, the conflicted intervals of the k-shortest-route were identified with the time window theory. The most available path was chosen with an objective of the minimum completion time. The back tracking method was combined to finish the routing scheduling. Finally, experiments of the proposed method were simulated. The results show that the multi-agent framework is suitable and the proposed scheduling algorithm is feasible and valid.展开更多
An edge-colored graph G is conflict-free connected if any two of its vertices are connected by a path,which contains a color used on exactly one of its edges.The conflict-free connection number of a connected graph G,...An edge-colored graph G is conflict-free connected if any two of its vertices are connected by a path,which contains a color used on exactly one of its edges.The conflict-free connection number of a connected graph G,denoted by cf c(G),is defined as the minimum number of colors that are required in order to make G conflict-free connected.In this paper,we investigate the relation between the conflict-free connection number and the independence number of a graph.We firstly show that cf c(G)≤α(G)for any connected graph G,and give an example to show that the bound is sharp.With this result,we prove that if T is a tree with?(T)≥(α(T)+2)/2,then cf c(T)=?(T).展开更多
For automated container terminals,the effective integrated scheduling of different kinds of equipment such as quay cranes(QCs),automated guided vehicles(AGVs),and yard cranes(YCs)is of great significance in reducing e...For automated container terminals,the effective integrated scheduling of different kinds of equipment such as quay cranes(QCs),automated guided vehicles(AGVs),and yard cranes(YCs)is of great significance in reducing energy consumption and achieving sustainable development.Aiming at the joint scheduling of AGVs and YCs with consideration of conflict-free path planning for AGVs as well as capacity constraints on AGV-mate which is also called buffer bracket in blocks,a mixed integer programming model is established to minimize the energy consumption of AGVs and YCs for the given loading/unloading task.A solution method based on a novel bi-level genetic algorithm(BGA),in which the outer and the inner layer search the optimal dispatching strategy for QCs and YCs,respectively,is designed.The validity of the model and the algorithm is verified by simulation experiments,which take the Port of Qingdao as an example and the performance under different conflicting resolution strategies is compared.The results show that,for the given task,the proposed solution to conflict-free path and the schedule provided by the algorithm can complete the task with minimum energy consumption without loss of AGVs utilization,and the number of AGV-mates should be adjusted according to the task rather than keeping unchanged.Comparison results indicate that our proposed approach could efficiently find solutions within 6%optimality gaps.Energy consumption is dropped by an average of 15%.展开更多
基金National Natural Science Foundations of China(No. 61273035,No. 71071115)National High-Tech R&D Program for CIMS,China(No. 2009AA043000)
文摘Overhead-hoist-transporters (OHTs) have become the most appropriate tools to transport wafer lots between inter-bay and intra-bay in united layouts of automated material handling systems (AMHSs) in 300 mm semiconductor wafer fabrications. To obtain a conflict-free scheduling solution, an intelligent multi-agent-based control system framework was built to support the AMHSs. And corresponding algorithms and rules were proposed to implement cooperation among agents. On the basis of the mentioned above, a time-constraint-based heuristic scheduling algorithm was presented to support the routing decision agent in searching the conflict-free shortest path. In the construction of the algorithm, the conflicted intervals of the k-shortest-route were identified with the time window theory. The most available path was chosen with an objective of the minimum completion time. The back tracking method was combined to finish the routing scheduling. Finally, experiments of the proposed method were simulated. The results show that the multi-agent framework is suitable and the proposed scheduling algorithm is feasible and valid.
基金supported by Hunan Education Department Foundation(No.18A382)。
文摘An edge-colored graph G is conflict-free connected if any two of its vertices are connected by a path,which contains a color used on exactly one of its edges.The conflict-free connection number of a connected graph G,denoted by cf c(G),is defined as the minimum number of colors that are required in order to make G conflict-free connected.In this paper,we investigate the relation between the conflict-free connection number and the independence number of a graph.We firstly show that cf c(G)≤α(G)for any connected graph G,and give an example to show that the bound is sharp.With this result,we prove that if T is a tree with?(T)≥(α(T)+2)/2,then cf c(T)=?(T).
基金This study is supported by the Natural Science Foundation of China under Grant Nos.61673228 and 61072260the Science Technology Program of Qingdao(21-1-2-16-zhz).
文摘For automated container terminals,the effective integrated scheduling of different kinds of equipment such as quay cranes(QCs),automated guided vehicles(AGVs),and yard cranes(YCs)is of great significance in reducing energy consumption and achieving sustainable development.Aiming at the joint scheduling of AGVs and YCs with consideration of conflict-free path planning for AGVs as well as capacity constraints on AGV-mate which is also called buffer bracket in blocks,a mixed integer programming model is established to minimize the energy consumption of AGVs and YCs for the given loading/unloading task.A solution method based on a novel bi-level genetic algorithm(BGA),in which the outer and the inner layer search the optimal dispatching strategy for QCs and YCs,respectively,is designed.The validity of the model and the algorithm is verified by simulation experiments,which take the Port of Qingdao as an example and the performance under different conflicting resolution strategies is compared.The results show that,for the given task,the proposed solution to conflict-free path and the schedule provided by the algorithm can complete the task with minimum energy consumption without loss of AGVs utilization,and the number of AGV-mates should be adjusted according to the task rather than keeping unchanged.Comparison results indicate that our proposed approach could efficiently find solutions within 6%optimality gaps.Energy consumption is dropped by an average of 15%.
