A FLEXIBLE SIMULATION SYSTEM FOR SCHEDULING WITH VARIOUS CONSTRAINTS

A simulation system, which can be widely used to determine the startin g times of operations for general batch plants, is proposed. The opera tions of a batch plant are first expressed by a sequence of basic oper ations such as filling, processing, discharging and cleaning. By using these basic operations, the simulation problem can be reduced to that of determining the starting times of the basic operations. A variety of constraints are grouped into four types, and it is demonstrated tha t the constraints on finite intermediate storage can be converted into the constraints on precedence relationships of basic operations. Then , for each of the three types of constraints, simulation modules to ca lculate the earliest and latest starting times of basic operations are developed. A simulation program to calculate the starting times of ba sic operations which satisfy all types of constraints can be generated by combining these simulation modules. The major feature of the propo sed method is that the simulation program can be easily modified by re combining the simulation modules. Therefore, a simulation program with sufficient flexibility can be developed by using the proposed method.