A Job Shop Scheduling and Location of Battery Charging Storage for the Automated Guided Vehicles (AGVs)

When the Automated Guided Vehicles (AGVs) are transferring the parts from one machine to another in a job shop environment, it is possible that AGVs stop on their guide paths since their batteries are discharged. Consequently, it is essential to establish at least one Battery Charging Storage (BCS) to replace full batteries with empty batteries for the stopped AGVs. Due to non-predictable routes for AGVs in the manufacturing systems, to find the best place to establish the BCS can impact performance of the system. In this paper, an integrated mathematical model of job shop and AGV scheduling with respect to the location of a BCS is proposed. The proposed nonlinear model is transformed into a linear form to be efficiently solved in GAMS software. Finally, several numerical examples are presented to test the validity of the proposed mathematical model. The results show that the optimal cost and location of BCS can be obtained with respect to the number of AGVs, machines, parts, and other problem parameters. In addition, it is concluded that the increasing number of AGVs in a manufacturing system cannot be always a suitable policy for reducing the cost because in such conditions. Further to that, the conflict of AGVs may increase leading to the increase of the makespan. In other words, following the optimal point, increasing AGVs leads to the increase in costs.