Hierarchical Control of Hybrid Systems

The topic of this contribution is the synthesis of hierarchical control systems for hybrid problems. We outline a method that is based on a hierarchy of models describing the plant at various levels of abstraction and a decomposition of the overall specification. The proposed method captures several key requirements for hierarchical control: it includes the notion of information aggregation between adjacent control levels; it allows for a combination of continuous and discrete event controllers on various levels of the hierarchy; complexity of the synthesis procedure and the resulting control scheme is considerably reduced when compared to an unstructured (and therefore non-hierarchic) approach; finally, it provides a mathematical guarantee that the specified hierarchical interaction between the different controller levels does indeed solve the overall problem. The method is illustrated by an example from process control, the synthesis of a discrete start-up scheme for a distillation column.