Bio-inspired approach for autonomous routing in FMS

Today's mass production strategies are unable to cope with the present needs of the manufacturing industry, which is constantly confronted with changing and increasingly complex product requirements as well as mounting pressure to decrease costs. To meet this challenge, Flexible Manufacturing Systems (FMS) must become more robust, scalable, reconfigurable, dynamic, adaptable and even more flexible. The challenge is even greater given that both production program modifications and resource failures can necessitate a partial or total reconfiguration of the FMS routing. Such reconfiguration is difficult to accomplish both because the problem is huge (combinatory explosion) and because each individual failed resource situation requires anticipating a different partial solution. In response to the FMS challenge, this chapter proposes autonomous routing of physical FMS flows. Many international research projects focusing on the design of heterarchical (non-hierarchical) architectures have already been completed. Such architectures play a prominent role in the new control systems that dominate the field of FMS research (Duffie & Prabhu, 1996; Pujo & Kieffer, 2002). Our contribution to such decentralized control is inspired by the biological phenomenon called stigmergy, defined as insects' use of chemicals, called pheromones, to organize group activity. For example, foraging ants are known to lay down chemical trails, which are, in turn, followed by other ants who add their own odour to the trail, thus reinforcing it for future use. This stigmergic activity has an optimizing effect on performance. It allows creatures to communicate indirectly by sensing and modifying their local environment, and it is this communication that determines the creature's behaviour. The next section of this chapter describes the concept of stigmergy. After presenting the different pheromonal characteristics upon which our bio-inspired approach is based, we describe several pheromone emulation mechanisms and some interesting insect-based methods that have been devised for various