Hierarchical supervisory control for batch processes

Batch processes take an important place in process industries. A batch process involves a sequence of operations that are carried out on a discrete quantity of material within a piece of operating equipment. A recipe specifies the sequence of operations to be executed and all possible ways the plant can by utilized in order to produce the desired product. A discrete supervisor can be used to coordinate the simultaneous execution of a number of recipes within the same plant. Its task is to ensure that all recipes can be terminated correctly, i.e. it prevents actions that will lead the system into a deadlock. This is done by allowing/disallowing the recipes access to the plant’s different resources. An earlier approach to this problem [4] resulted in a maximally permissive supervisor but the synthesis suffered from the combinatorial explosion of the state space.