Semi-heterarchical control of FMS: From theory to application

This paper presents both a model and a real implementation of a semi-heterarchical control system for flexible manufacturing systems (FMS). After presenting the concepts of heterarchical and semi-heterarchical control, a product-based control structure, composed of a dynamic allocation process (DAP) and a dynamic routing process (DRP), is proposed. Though the associated control processes (DAP and DRP) are hierarchically dependant, each is managed heterarchically, with no supervisor. The dynamic allocation algorithms are presented, and our highly distributed approach to routing control is then explained in detail. A real distributed application of the active entities and the control architecture was implemented in the AIP-PRIMECA pole at the University of Valenciennes, and this implementation is described in detail. A mixed-integer linear model of the FMS was used to compute lower bounds. The flexibility and robustness of our approach are highlighted through several real experiments.