COOPERATIVE SCHEDULING AND ITS APPLICATION TO STEELMAKING PROCESSES

This paper proposes a practical approach to actual scheduling problems and describes its application to creating daily schedules for steelmaking processes. Cooperative scheduling is a new paradigm in which procedures, rules, and the user cooperate to make a feasible schedule efficiently. The procedures, collectively called a "scheduling engine," work as a local constraint satisfier to solve general primitive constraints. Rules that represent domain-dependent knowledge then solve the domain-specific constraints by means of a pattern-matching function. Finally, the user evaluates the schedule and modifies it via a user-friendly interface with direct-manipulation functions. The user interaction is therefore included in the system architecture as a global constraint satisfier. The iteration of this cycle improves the schedule until it becomes feasible. Scheplan is a scheduling environment that applies this approach to scheduling steelmaking processes. The system has been transferred to the Keihin plant of Nippon Kokan Co., Ltd. (NKK), which is one of the major steelmaking industries in Japan, and is being tested and evaluated in an actual environment for operational use. According to experimental reports, the daily scheduling time is much lower than in manual scheduling. Furthermore, the quality of the schedule itself is much improved, which results in a saving of about $1 million a year in production costs.