Estimation of Part Waiting Time and Fleet Sizing in AGV Systems

Abstract

As manufacturing systems have grown in size and complexity, material flow control has become one of the key issues for system efficiency, and determination of the number of vehicles required is an important issue in the design of the AGV (automatic guided vehicle) systems for automated material flow control. In an AGV system, a part issues a delivery request for its transportation, and then an empty vehicle is assigned based on a pre-determined vehicle selection rule and provides delivery service.This research presents a fleet sizing procedure for an AGV system with multiple pickup and delivery stations. A queueing model is used to estimate part waiting times. The fleet sizing procedure estimates the minimum number of vehicles needed to ensure a predefined part waiting time limit. While most stochastic models assume firstcome-first-served or random vehicle selection rules for the selection of an empty vehicle, this model considers such additional rules as the nearest vehicle selection rule, which is the most popular among all vehicle selection rules. The performance of the proposed model is examined through computational experiments.

Performance evaluation of flexible manufacturing systems under uncertain and dynamic situations

“…The constraints are defined in the equation (17) - (22). The constraint defined in equation (17) governs for the avoidance of the deadlocks.…”

“…Constraint (21) need to be at least greater than 1 m  for the dedicated scenario to become more desirable. Equation (22) indicates that machining time for any operation can't exceed the capacity of any machine.…”

The Integrated Room Layout for a Semiconductor Facility Plan

“…Egbelu and Tanchoco [27] report that the selection of a part to transport by an idle vehicle impacts the performance of a material handing system less than the selection of an idle vehicle by a part. An estimation of the means and variances of a vehicle's empty travel time and a vehicle's loaded travel time, and a part's mean waiting time for vehicles under the NIV and FCFS rules can be obtained from [28] and [29]. The procedure uses the distances and travel frequencies between ports.…”

Dynamic vehicle allocation in Automated Material Handling System

“…Some previous research have been devoted to vehicle management of AMHS in which the attention was put on the AMHS configuration to avoid vehicle collision, deadlock or blockage, and to prevent the paralysis of handling system [1,2,3,4]. Some investigations were also made on the dispatching rules for the vehicles to improve the performance of the system [5,6,7,8,9].…”