A Scheduling Expert for Steel-Making Process by Cooperative Scheduling

Abstract

This paper proposes cooperative scheduling to solve complex process-scheduling problems in actual plants. Factory management calls for complex decisions and analysis of production processes, incoming orders, cost accounting, etc., based on a wide variety of information on manufacturing systems in today's frequently changing technical and marketing environments. Cooperative scheduling provides a full-screen-oriented interface which displays a graphic diagram of a schedule and allows the user to modify it by direct manipulation. When the user edits a schedule, he can just concentrate on modifying its global structure without paying attentions to some constraints, such as machine conflicts and domain specific constraints. After a user's modification, constraints are automatically satisfied by the system very quickly, while preserving the global structure of the schedule. Some constraints are solved algorithmically, and others are satisfied by using rules. Rule-base capabilities, therefore, are also essential in cooperative scheduling. After constraints are satisfied, the user revise the schedule and modify it if some portions cannot be acceptable. The user repeats these steps until he obtains a feasible schedule. To justify our approach, a system called Scheplan has been developed and tested in an actual plant for an operational use. According to experimental reports, the daily scheduling time is greatly reduced compared with the time done by a limited number of experts. Furthermore, the quality of the daily schedule is much improved.