Time aggregation in production control and scheduling: towards efficient decision-support systems

A software system is developed for efficient optimal scheduling and production control in process industries modelled by production departments separated by buffers in serial or recycled paths. The new concept of time aggregation presented is easily implementable allowing a very fast solution of the optimal control of buffer levels. This optimal control problem is a large scale singular one (due to the chosen cost function) conveniently solved by a special technique of hierarchical calculus:'the iterative solution of a sequence of nonsin-gular problems converging to the singular one. Numerical results applied to a pulp and paper mill show that the new algorithm is substantially faster than the one previously used. This fact allowed the development of a complete software platform, presented in the paper, composed of several modules: modelling of industrial complex, (re)configuration, simulation, optimization, user interface—aiming at the realization of a decision support system for interactive use by daily operators and in instruction activities.