## 3 Design AGV Scheduling Strategies
### AGV Standby Strategy  
The AGV standby strategy is a critical factor in optimizing the efficiency of automated production systems. It determines how AGVs operate after completing their current tasks, directly influencing the execution efficiency of subsequent tasks. A well-designed standby strategy minimizes delays between tasks, ensures that AGVs are ready to begin the next task on time, and maximizes their utilization. If the standby position of an AGV is far from the location of the next task, the initiation of the task may be delayed, ultimately impacting the production schedule. Therefore, selecting an appropriate standby strategy is essential for improving production efficiency and maintaining a stable production pace. The three AGV standby strategies involved in this study are as follows:(1) In the Charging Room Standby (CRS) strategy, the AGV returns to the charging room after completing its task and waits for the next assignment. This strategy ensures that the AGV maintains sufficient battery levels, making it suitable for production environments that require periodic charging. However, if the next task is far from the charging room, the AGV's travel time may cause production delays.  
(2) The Current Position Standby (CPS) strategy requires the AGV to stay at its position after completing a task. It waits there for the next assignment. This strategy reduces the AGV's travel distance. It works well when tasks are close to each other. However, if the next task is far away, this strategy can cause the AGV to block other operations. This reduces overall efficiency.  
(3) In the Next Task Standby (NTS) strategy, the AGV moves in advance to the starting position of the next task. This reduces the transition time between tasks. This strategy works well in production environments where tasks are farther apart. It improves operational efficiency. However, it requires precise scheduling and prediction. This prevents the AGV from remaining idle for extended periods.  
The AGV standby strategy significantly impacts production efficiency. Each strategy has its advantages and drawbacks, and the optimal choice depends on the layout of the production environment and the distribution of tasks. The selection of AGV scheduling strategies in this study is based on both practical industrial requirements and theoretical considerations. The Random Choice strategy serves as a baseline approach, ensuring an even distribution of AGV workload. The Sequential Choice strategy is inspired by traditional first-come-first-served principles, prioritizing AGVs in order of availability to maintain scheduling stability. The Nearby Choice strategy, on the other hand, introduces a distance-based optimization aspect, aiming to minimize unnecessary AGV travel and improve response time. The novelty of our approach lies in the integration of these strategies with a pulsating assembly flow shop environment, where dynamic AGV assignments play a critical role in optimizing production efficiency. Furthermore, by combining these AGV selection strategies with different standby strategies, we systematically evaluate their impact on scheduling performance under varied conditions, which has not been extensively explored in previous studies.