ASAP Projects: Fuzzy Multicriteria Approaches to Scheduling and Rescheduling

Title: Fuzzy Multicriteria Approaches to Scheduling and Rescheduling Problems in Uncertain Environments

Aim and Objectives:
The main aim of this research is to propose a new methodology for developing automated production scheduling systems using multiple scheduling criteria, in the presence of uncertainty. Scheduling problems will be modelled as decision analysis problems under uncertainty and, consequently, scheduling experts will be given a more important and active role than in classical approaches. The key objectives of the research are:

1. To identify and analyse sources of uncertainty, which are inherent in real-world production scheduling problems, including both parameters and constraints. The identified uncertainties will be formalised using fuzzy logic-based techniques.

2. To propose a suitable framework for the design and development of scheduling models for complex production environments. This will involve: (a) investigation of measures of fuzzy constraint satisfaction, and (b) modelling the preference structure of the schedulers. Based on these, two new types of models will be developed that include the uncertainties identified in 1.) and make compromise solutions across multiple criteria that describe different schedule performance measures, taking into consideration the preferences of the scheduling experts, namely (c) fuzzy multicriteria models based on dispatching rules, and (d) fuzzy multicriteria meta-heuristics for production scheduling. A successful outcome of the modelling effort will result in a tool, which is usable in real-world scheduling environments. In addition, we are aware of the problem of interfacing to a Computer Aided Manufacturing (CAM) platform in order to collect real world data and will address this issue as a feature of the framework.

3. To extend the scheduling framework developed in 2.) with rescheduling models. This will involve: (a) identification of various types of disruptions and uncertainty that can affect a production schedule, (b) development of new rescheduling methods which take into consideration identified disruptions and related uncertainties and use multiple criteria for new schedule construction, based on measures of performance and measures of reschedule stability, and (c) studying the effects of various disruption scenarios on the rescheduling performance measures.

4. To perform sensitivity analysis in order to provide a better understanding of the scheduling models and requirements in different scheduling situations. The sensitivity analysis will be carried out in two directions: (a) investigating how changes to uncertainty in parameters and constraints employed in the developed models affect the schedules; (b) evaluating the sensitivity of schedules to changes of scheduler's preferences toward the performance measures used to evaluate schedules.

Funding Body: EPSRC, Reference number: GR/R95319/01