Effect of manufacturing system constructs on pick-up and drop-off strategies of multiple-load AGVs

Abstract

This research investigates the interaction between manufacturing system constructs and the operation strategies in a multiple-load Automated Guided Vehicle System (AGVS) when AGVs in a system can carry two or more loads. The load pick-up problem arises when an AGV stops at a pick-up queue and has to decide which part(s) in the queue should be picked up. Since an AGV can carry multiple loads, a drop-off rule is then needed to determine the next stop for the AGV to deliver one or more loads. Several real-time composite heuristic rules for selecting load and determining the next stop are proposed and evaluated in two manufacturing system constructs: the jobshop and the flexible manufacturing system (FMS). A number of simulation models are developed to obtain statistics on various performance measures of the two system constructs under different experimental conditions. The simulation results reveal that the pick-up rules affect the system more than the drop-off rules. In general, rules to avoid starving and blocking in workstations perform better than the rules for shortest distance in throughput. However, the rules perform differently in jobshop and FMS based on other performance measures, indicating an interaction between system constructs and load selection strategies. The difference in rule performance within the same construct is also affected by several AGVS design parameters. Overall our study suggests that no load pick-up rule is always a champion, and the design of an efficient multiple-load AGVS must consider all issues in a global fashion.

A multiple-attribute method for concurrently solving the pickup-dispatching problem and the load-selection problem of multiple-load AGVs

“…Their simulation results indicated load-selection rules and pickup-dispatching rules affected each other's performance. Lee and Srisawat [35] referred to the load-selection problem as the load pick-up problem. They investigated the interaction between manufacturing system constructs and the operations strategies in a multiple-load AGV system.…”

A multiple-criteria real-time scheduling approach for multiple-load carriers subject to LIFO loading constraints

“…With an MBS-y rule, an idle dolly train will wait in the stocking area if the number of reorders is less than y. Note that, for multiple-load carriers in other systems, dispatching rules are usually used to match a pick-up request with an idle carrier (e.g., Sinriech and Kotlarski (2002) and Lee and Srisawat (2006)). For example, the Nearest Vehicle (NV) rule is used to select the carrier closest to the requesting workstation.…”

“…Nayyar and Khator (1993) claimed that the shortest-distance dispatching rule outperformed other rules after comparing several load pick-up and load drop-off rules. Lee et al (1996) and Lee and Srisawat (2006) also compared multiple scheduling rules to observe the interactions between different scheduling rules and certain performance measures.…”

The performance of load-selection rules and pickup-dispatching rules for multiple-load AGVs

“…If there is more than one load waiting in the queue of the pickup point, then the multiple-load AGV, V , must determine which load it should pick up first from the queue of a pickup point. Researchers refer to this problem as the load-selection problem or the load pick-up problem [11][12][13]. In this study, we will follow the multiple-load AGV control process proposed by Ho and Chien [18] and focus on the pickupdispatching problem and the load-selection problem.…”

“…[8][9][10]) guide-path design problems of AGV systems, and still others (e.g. [11][12][13]) the load-selection problem (also known as the load pick-up problem) and/or the load drop-off problem. * Corresponding author.…”