Automated guided vehicles(AGVs)are key equipment in automated container terminals(ACTs),and their operational efficiency can be impacted by conflicts and battery swapping.Additionally,AGVs have bidirectional transport...Automated guided vehicles(AGVs)are key equipment in automated container terminals(ACTs),and their operational efficiency can be impacted by conflicts and battery swapping.Additionally,AGVs have bidirectional transportation capabilities,allowing them tomove in the opposite directionwithout turning around,which helps reduce transportation time.This paper aims at the problem of AGV scheduling and bidirectional conflict-free routing with battery swapping in automated terminals.A bi-level mixed integer programming(MIP)model is proposed,taking into account task assignment,bidirectional conflict-free routing,and battery swapping.The upper model focuses on container task assignment and AGV battery swapping planning,while the lower model ensures conflict-free movement of AGVs.A double-threshold battery swapping strategy is introduced,allowing AGVs to utilize waiting time for loading for battery swapping.An improved differential evolution variable neighborhood search(IDE-VNS)algorithm is developed to solve the bi-level MIP model,aiming to minimize the completion time of all jobs.Experimental results demonstrate that compared to the differential evolution(DE)algorithm and the genetic algorithm(GA),the IDEVNS algorithmreduces fitness values by 44.49% and 45.22%,though it does increase computation time by 56.28% and 62.03%,respectively.Bidirectional transportation reduces the fitness value by an average of 10.97% when the container scale is small.As the container scale increases,the fitness value of bidirectional transportation gradually approaches that of unidirectional transportation.The results further show that the double-threshold battery swapping strategy enhances AGV utilization and reduces the fitness value.展开更多
Harvester ants are one of the most extensively studied groups of ants,especially the group foraging ants,Messor barbarus(Linnaeus,1767),which construct long-lasting trunk trails.Limited laboratory investigations have ...Harvester ants are one of the most extensively studied groups of ants,especially the group foraging ants,Messor barbarus(Linnaeus,1767),which construct long-lasting trunk trails.Limited laboratory investigations have delved into head-on encounters along foraging trails involving workers moving in opposing directions,with fewer corresponding studies conducted in the natural environment.To address this gap,we devised an in-field experimental design to induce lane segregation on the foraging trunk trail of M.barbarus.Using an image-based tracking method,we analyzed the foraging behavior of this species to assess the costs associated with head-on encounters and to figure out the natural coexistence of outgoing and returning workers on a bidirectional route.Our results consistently reveal heightened straightness and speed in unidirectional test lanes,accompanied by an elevated foraging rate compared to bidirectional lanes.This suggests a potential impact of head-on collisions on foraging behavior,especially on foraging efficiency.Additionally,Kinematic analysis revealed distinct movement patterns between outbound and inbound flows,particularly low speed and sinuous trajectories of inbounding unladen workers.The study of encounter rates in two traffic systems hints at the plausible utilization of individual memory by workers within trails,underscoring the pivotal role of encounters in information exchange and load transfer.展开更多
基金supported by National Natural Science Foundation of China(No.62073212)Shanghai Science and Technology Commission(No.23ZR1426600).
文摘Automated guided vehicles(AGVs)are key equipment in automated container terminals(ACTs),and their operational efficiency can be impacted by conflicts and battery swapping.Additionally,AGVs have bidirectional transportation capabilities,allowing them tomove in the opposite directionwithout turning around,which helps reduce transportation time.This paper aims at the problem of AGV scheduling and bidirectional conflict-free routing with battery swapping in automated terminals.A bi-level mixed integer programming(MIP)model is proposed,taking into account task assignment,bidirectional conflict-free routing,and battery swapping.The upper model focuses on container task assignment and AGV battery swapping planning,while the lower model ensures conflict-free movement of AGVs.A double-threshold battery swapping strategy is introduced,allowing AGVs to utilize waiting time for loading for battery swapping.An improved differential evolution variable neighborhood search(IDE-VNS)algorithm is developed to solve the bi-level MIP model,aiming to minimize the completion time of all jobs.Experimental results demonstrate that compared to the differential evolution(DE)algorithm and the genetic algorithm(GA),the IDEVNS algorithmreduces fitness values by 44.49% and 45.22%,though it does increase computation time by 56.28% and 62.03%,respectively.Bidirectional transportation reduces the fitness value by an average of 10.97% when the container scale is small.As the container scale increases,the fitness value of bidirectional transportation gradually approaches that of unidirectional transportation.The results further show that the double-threshold battery swapping strategy enhances AGV utilization and reduces the fitness value.
文摘Harvester ants are one of the most extensively studied groups of ants,especially the group foraging ants,Messor barbarus(Linnaeus,1767),which construct long-lasting trunk trails.Limited laboratory investigations have delved into head-on encounters along foraging trails involving workers moving in opposing directions,with fewer corresponding studies conducted in the natural environment.To address this gap,we devised an in-field experimental design to induce lane segregation on the foraging trunk trail of M.barbarus.Using an image-based tracking method,we analyzed the foraging behavior of this species to assess the costs associated with head-on encounters and to figure out the natural coexistence of outgoing and returning workers on a bidirectional route.Our results consistently reveal heightened straightness and speed in unidirectional test lanes,accompanied by an elevated foraging rate compared to bidirectional lanes.This suggests a potential impact of head-on collisions on foraging behavior,especially on foraging efficiency.Additionally,Kinematic analysis revealed distinct movement patterns between outbound and inbound flows,particularly low speed and sinuous trajectories of inbounding unladen workers.The study of encounter rates in two traffic systems hints at the plausible utilization of individual memory by workers within trails,underscoring the pivotal role of encounters in information exchange and load transfer.
