Hybrid modelling and optimal control of a multi product batch plant

This paper addresses the problem of optimally selecting the production plan for a Multiproduct Batch Plant. The proposed approach can also be applied to a broader class of optimal control problems for systems with discrete inputs. The plant is modelled as a Discrete Hybrid Automaton (DHA) using the high level modelling language, HYbrid System DEscription Language (HYSDEL), which allows conversion of the DHA model into an Mixed Logical Dynamical (MLD) model. The solution algorithm, which takes into account a model of a hybrid system described as an MLD system, is based on reachability analysis ideas. The algorithm abstracts the behaviour of the hybrid system into a “tree of evolution”, where nodes of the tree represent reachable states of the system, and branches connect two nodes if a transition exists between the corresponding states. To each node a cost function value is associated and, based on this value, the tree exploration is driven, searching for the optimal control profile

Scheduling of hybrid systems: multi product batch plant

The paper proposes a solution to a class of scheduling problems where the goal is to minimize the schedule (production) time. The algorithm. which takes into account a model of a hybrid system described as MLD (mixed logical dynamical) system, is based on performance driven reachability analysis. The algorithm abstracts the behavior of the hybrid system by building a tree of evolution. Nodes of the tree represent reachable states of a process, and the branches connect two nodes if a transition exists between the corresponding states. To each node a cost function value is associated and based on this value. the tree exploration is driven. As soon as the tree is explored. the global solution to the scheduling problem is obtained

Multiple pressures and their combined effects in Europe's seas

This report presents for the first time in Europe an overview of anthropogenic pressures and their combined effects in Europe’s seas. The assessment covers the period of 2011-2016 but also presents how human activities and pressures at sea have changed over a longer time horizon. Practically the entire European marine area is under multiple pressures – such as hazardous substances, fish stock exploitation, climate change, underwater noise, non-indigenous species, seafloor damage, marine litter and nutrient enrichment. Shelf areas and coastal zone are affected by physical disturbance of seabed, eutrophication and non-indigenous species. The highest potential combined effects are found along coastal areas of the North Sea, Southern Baltic Sea, Adriatic and Western Mediterranean. The good news from this assessment is that many of the dangerous trends seem to have reversed. We have shown that the nutrient levels, hazardous substances, northern fish stocks and tuna stocks in the open seas show improvement. However, extensive pressures from several human activities still threaten the marine ecosystem, such as disturbance of seabed, and no trend reversal was seen in this assessment