Simulation models are widely used as powerful tools for scheduling. Simulation is a descriptive  modelling  technique that is used to evaluate schedules through computer-based experiments. This type of modelling is a bridge to AI approaches. Simulation has proved to be an excellent tool for dynamic scheduling. Dynamic scheduling  has  been  shown to be a non-deterministic polynomial (NP) complete problem [39], where there are a large number of possibilities in which job operations can be sequenced. Therefore, dynamic scheduling does not lend itself to a satisfactory mathematical analytical solution, especially for a complex manufacturing system  such as an FMS of a realistic scale. The dynamic nature of such systems demands a scheduling procedure,  which  is  reactive and sensitive to the system’s status,  instead  of  a  predictive one. It is not yet known whether policies and procedures designed to schedule and control traditional manufacturing processes are appropriate for an FMS, which is an advanced manufacturing technology. Thus, in order to enhance the per- formance of existing FMSs and to allow for further develop- ment of these automated manufacturing systems, proper pro- cedures for the scheduling and control of these automated systems must be developed and documented. Since all the system’s data are available and under computer control, more sophisticated procedures can be designed and    implemented.

The objective of this paper is to review simulation study on FMSs scheduling rules. We review the simulation of general FMS scheduling studies in Section 2, multi-criteria scheduling approaches in Section 3, and artificial intelligence (AI) approaches in FMSs in Section 4. In almost all cases, the scheduling problems and the employed performance measures of each approach will be mentioned. Section 5 provides con- clusions and some suggestions for further research and develop- ment. Section 6 gives the acronyms  that are used  throughout the paper.

2. General FMS Scheduling  Studies

2.1 Introduction

Scheduling of FMSs has been one of the most attractive  areas of investigation for both researchers and practitioners in the industrial context, and the literature on FMSs is abundant with papers on scheduling. Several review articles were published which synthesise the literature on different  phases  of FMSs. For example, Spano et al. [15] reviewed the work on the design of FMSs in the areas of facilities design, material handling systems design, control systems design, and scheduling. Rach- amadugu and Stecke [12] classified and reviewed the existing FMSs scheduling procedures. Their classification was based on some key factors such as the FMS type, the mode of system operation, the nature of the  demands  placed  on  the  system, the scheduling environment, and the responsiveness of the system to disturbance. They also discussed the choice of appropriate scheduling criteria.

Basnet and Mize  [40]  reviewed  the  literature  concerning the operational aspects of FMSs. They described scheduling methodology under six different categories: mathematical pro- gramming, multi-criteria decision making, heuristic oriented, control theoretic, simulation, and artificial intelligence. They concluded that the discrete-event simulation technique has the potential to make major contributions to FMS operation and stressed that simulation can be used to model FMSs compre- hensively.

Gupta et al. [41] extended the review to cover simulation approaches to the FMS scheduling problems as well as analyti- cal ones. They pursued  two  objectives:

1. Developing a framework within which the current literature on dispatching rules  can be  discussed.