In this paper, a motion planning method for two stacker cranes in an Automated Storage and Retrieval System (AS/RS) is proposed. For the cranes to operate cooperatively, they must perform tasks while avoiding collisions. In addition, the requirements, which include fast operation and short calculation time, must be satisfied, along with a specific mechanical constraint on the motion of the stacker cranes. For these problems, an approach is proposed in which a motion is generated on two levels. On the first, collision is avoided by using constraint on trajectories. A trajectory generated on this level ensures the shortest travel time. If a collision cannot be avoided on the first level, the system shifts to the second, in which heuristics are used for collision avoidance. The proposal is for highspeed heuristics based on a binary search. The effectiveness of the proposed algorithm is shown through simulations. The simulation results indicate that, in a layout of 60 racks in the horizontal direction and 10 in the vertical direction under standard task conditions, the method has an efficiency of 1.91 with respect to a single crane system and 1.66 seconds for the motion planning of one task when a computer with a 3.0 GHz CPU is used.

We propose a control methodology of stacker cranes to avoid collisions in warehouse environment including the constraint on trajectories caused by dynamics. In a warehouse environment, there are three problems: constraint on trajectories caused by the consideration of dynamics (e.g., vibration control), safety in the case of an emergency stop, and practical calculation time. In the proposed method, the motion is planned through two approaches. In the first, the trajectories of cranes are chosen from candidates that satisfy the constraint on dynamics and checked to determine whether the selected trajectory ensures safety in an emergency. The calculation cost is reduced by confining the candidate trajectories using the characteristic of the number of cranes. If a collision cannot be avoided in the first approach, we adjust the confined candidate trajectories and find a suboptimal trajectory. Measures used in the second approach are to delay the movement of cranes or to generate detours. The simulation results show the effectiveness of the proposed method.

Currently, container ships move cargo with minimal participation from external trucks. However, there is slack time between the departure of container ships and the completion of cargo handling by container ships without the participation of external trucks; therefore, external trucks can be used to move cargo without delaying the departure time. In this paper, we propose a solution involving the control algorithms of transfer cranes (TCs) because the efficiency of yard operations depends largely on the productivity of TCs. TCs work according to heuristic rules using the forecasted arrival times of internal and external trucks. Simulation results show that the proposed method can reduce the waiting time of external trucks and meet the departure time of container ships.

For an efficient seapornerminal management ， we propose a novel opeTational mode 】 ， namely ． a double container − handling operatlon among opera ［ ing machines ， such as au 匸omated guided v 巳 hicles ( AGVs ) ， automated 1ransfer cranes ( ATCs ) ． and quay con 【 ainer cranes ( QCCs) ． In addi 重 iQn， a passing lane is provided in a container storage yard in order to activate lhe container − handhng operation performed by the AGVs and ATCs ． In this paper， the effect of the double container − handling Qperatio " and passing lane on the system utilizatien isexamined ． Finally ， the effectiveness of the proposed operational model with a passing lane is discussed on the basis of the operating time and obtained number ofoperating machines for a given demand in consideration of a mega − co コtainer terminal． Key Wor 日s： Double container handling， seaport terminal rnanagement ， automated guided vehlcle