MULTISTAGE is a program for optimizing cyclic schedules of multiproduct continuous plants according to Jose M. Pinto and Ignacio E. Grossmann (1994). These are multistage plants which consist of a sequence of stages each involving one production line that are interconnected by storage tanks.The basic model is Mixed Integer Nonlinear Programming (MINLP).
Given is a number of specified products that are to be manufactured in a plant consisting of several stages that are interconnected by intermediate inventory tanks for each product. It is assumed that every product must be processed in the same sequence thoughout all the stages (i.e. flowshop plant). Each stage consists of one production line with equipment which is interconnected with a fixed topology. Transition times that arise between the processing of two products are sequence dependent. Given are also constant demand rates in the form of lower bounds that are to be satisfied. The problem then consists in determining the following for a cyclic schedule
- sequencing of products
- length of cycle time
- length of production times
- amounts of products to be products
- levels of intermediate storage and final product inventories.
The criterion used is the maximization of profit, that includes income from the sales of the products and inventory and transition costs.
This interface is written in language C and it is implemented on Windows NT, IBM RS6000, HP and SUN (SunOS and Solaris) workstations. The way this interface works is through the use of different menus; it is flexible and easy to use.Given the data of the problem, MULTISTAGE creates a new GAMS file containing the model equations and optimizes the problem using subroutines of DICOPT++, and plots the Gantt chart and Intermediate inventory profiles between each stage.
DICOPT++ ( DIscrete and Continuos OPTimizer ) was developed by J. Viswanathan and Ignacio E. Grossmann at the Engineering Research Center (EDRC) of the Carnegie Mellon University .It is based on the extensions of the outer-approximation algorithm for equality relaxation strategy.
MULTISTAGE has been developed by Arzu Türkay under the supervision of Ignacio E. Grossmann .
References for MULTISTAGE:
- Pinto J.M. and I. E. Grossmann, Optimal Cyclic Scheduling of multistage continuous multiproduct plants , Computers chem Engng. Vol. 18, No. 9, pp. 797-816, 1994.
- Türkay, Arzu, Guidelines for MULTISTAGE Interface , Carnegie Mellon University, Engineering Design Research Center, Pittsburgh, PA.