The State of the Art in Simulation Study on FMS Scheduling: A Comprehensive Survey Scheduling of flexible manufacturing systems (FMSs) has been one of the most attractive areas for both researchers and practitioners. A considerable body of literature has accumu- lated in this area since the late 1970s when the first batch of papers was published. A number of approaches have been adopted to schedule FMSs,  including  simulation  techniques and analytical methods. Numerous articles can be found  on each of these approaches. This paper reviews scheduling stud- ies of FMSs which employ simulation techniques as an analysis tool, since simulation is the most widely used tool for modelling FMSs. Scheduling methodologies are categorised into simul- ation of general scheduling studies, multi-criteria scheduling approaches, and artificial intelligence (AI) approaches  in FMSs. Comments on the publications, and suggestions for further research and development are   given.70587

Keywords: Artificial intelligence (AI); Flexible manufacturing systems;  Multi-criteria;   Scheduling; Simulation

1. Introduction

1.1 Introduction of FMS

Manufacturing emerged in the 1990s as one of the important keys to organisational success, and a number of comprehensive manufacturing strategies are receiving widespread attention   as a result of a renewed emphasis on manufacturing methods [1]. Computer integrated manufacturing, just-in-time (JIT) manufac- turing, factory automation, lean manufacturing, and flexible manufacturing systems (FMSs) are some of the recurring themes.

The largest single factor having a positive impact on manu- facturing  improvement  has  been  the  introduction  of    FMSs.

Correspondence and offprint requests to: Dr F. T. S. Chan, Department of Industrial and Manufacturing Systems Engineering,  The University of Hong Kong, Pokfulam Road, Hong Kong. E-mail: ftschan@hkucc.hku.hk

FMSs are the result of the growth in demand for  product quantity and the concern for the product quality. Another major motivation for FMS has been based on the perceived need for manufacturing industry to respond to change more rapidly than in  the  past [2].

FMSs have been defined in a number of  ways, but there  is not a standard accepted definition for the general term flexible manufacturing system. Most of the  definitions  are  based  on the hardware used in the system. For example, Byrkett et al. [3]  stated that:

A flexible manufacturing system (FMS) is a manufacturing  system in which groups of numerically controlled machines (machine centers) and a material handling system work together under computer control.

O’Keefe and  Kasirajan [4] defined  an FMS   as:

a group of workstations connected together by a material handling system (MHS) producing or assembling a number of different part types  under the  central control of a   computer.

Other definitions are based  on  the  capability  or performance of the system. For example, Kaltwasser et al. [5] stated that:

Flexible manufacturing systems (FMSs) are highly automated pro- duction systems, able to produce a great variety of different parts by  using the  same  equipment  and the  same control  system.

Sarin and Chen [6] stated    that:

FMS is designed to combine the  efficiency  of  a high-production line and the flexibility of a job shop to best suit the batch production  of mid-volume, and mid-variety of    products.

More definitions can be found in the literature (O’Grady [2]; O’Grady and Menon [7]).  Despite  the  range of  definitions, it is accepted that an FMS consists of three basic subsystems: