posted on 2008-03-05, 00:00authored byArul Sundaramoorthy, Christos T. Maravelias
In this article, we present a mixed-integer programming formulation for the simultaneous batching and
scheduling in multiproduct multistage processes. The proposed sequence-based formulation addresses limitations
of existing approaches where batching and scheduling decisions are carried out sequentially. To account for
batching decisions, we use additional batch-selection and batch-size variables and introduce demand-satisfaction
and unit-capacity constraints. Assignment constraints are active only for the subset of batches that are selected,
and sequencing is carried out between batches that are assigned on the same processing unit. We also propose
an alternate formulation to handle sequence-dependent changeover costs. Finally, to enhance the computational
performance of the model, we present methods that allow us to fix a subset of sequencing variables and we
develop a class of tightening inequalities based on time windows.