GENERAL-APPROACH AND TOOL FOR THE SCHEDULING OF COMPLEX PRODUCTION SYSTEMS

The aim of this paper is to present a flexible modelling framework imp lemented into a basic general scheduling tool for both, the study of s cheduling problems (for application developers and analysts) and as an efficient way to find practical solutions in complex industrial appli cations (for users). Thus, the basis to assist process modelling (simu lation and simple optimisation procedures) is provided as well as an o pen framework capable to be easily customised (implementation of parti cular constraints, rules, exceptions, etc.). This approach and tool ha ve been especially addressed to complex manufacturing systems (batch c hemical processes,;pharmaceutical, fine chemicals, etc.). Thus, the ki nd of recipes considered require a detailed description of tasks and s ubtasks and of the hard time and storage constraints implicated (simul taneous activities, unstable intermediates, product synthesis and othe r concurrent processes...). Towards this end, this work presents a gen eral and practical description of production processes and recipes, as well as the mathematical model for the timing of the activities invol ved. Yet, the compact description attained does not introduce extra co mplexity to simpler cases. The approach introduced is based in a hiera rchical description of the production processes and activities in whic h schedules are described by means of sequences of production runs ass ociated to structured sets of assigned activities. This work shows how this sequences may be rearranged using general techniques as simulate d annealing (SA), proving that this can be successful when specific ru les are not available. Finally, different case studies are analysed to show the-potential and flexibility of the approach presented. (C) 199 8 Published by Elsevier Science Ltd. All rights reserved.