A receding horizon strategy for the hierarchical control of manufacturing systems

This paper concerns the development of a hierarchical framework for the planning and scheduling of a class of manufacturing systems. In this framework, dynamic optimization plays an important role in order to define control strategies that, by taking into account the dynamic nature of these systems, minimize customized cost functionals subject to state and control constraints. The proposed architecture is composed of two hierarchical levels where a two way information flow, assuming the form of a state feedback control, is obtained through a receding horizon control scheme. At the higher level, an optimal control problem is solved by an iterative algorithm in order to define the control strategies in terms of aggregated production rates for the various subsystems. At the lower level, this control strategy is further refined in such a way that all sequences of operations are fully specified. Although this stage is strongly problem dependent an approach based on the notion of critical machine plays an important role in order to exploit the available flexibility