Karuna Hadeli

Self-organising in multi-agent coordination and control using stigmergy

In order to cope with todays dynamic environment, the described manufacturing control system is designed as a self-organising multi-agent system. The design of this novel system implements the PROSA reference architecture [1]. Coordination among agents is done indirectly through a pheromone-based dissipative field as is done by social insects in coordinating their behaviour. In this case, our agents act as social insects interpreting the pheromones put by the others in the environment. This control system is built from the basic elements of any manufacturing controller, namely products, resources and orders. However, the overall control system is constructed not only from those basic elements but also employing the appropriate interaction patterns among the agents who represent them. For coordination purposes, the agents send out a kind of mobile agents - artificial ants - to lay down information on the environment. In our case, where fulfilling the manufacturing orders is the main concern, there are at least 3 types of ant in this system: (1) feasibility ants - to propagate information concerning the feasible finishing routes; (2) exploring ants - to explore the feasible routes; and (3) intention ants - to propagate the route preferences. The overall mechanism enables the system to exhibit a self-organising behaviour.

Towards robust and efficient planning execution

This paper presents a holonic manufacturing execution system (MES) that cooperates with a planning system. This cooperation allows to combine the robustness and flexibility of the holonic MES with the optimisation performed by the planning system. The paper investigates the effect on the global performance of this cooperation for a specific manufacturing case in a series of experiments. It compares the effect of this cooperation when the planning is optimal with regard to the manufacturing case with situations where the planning system is not optimal. More precisely, it compares the performance of the HEMS in situations where the planning systems systematically misestimates the execution time of a workstation (e.g. a poorly maintained workstation or a partially operational workstation) to situations where this is not the case. The experiments are conducted under varying work loads. Also, the effort the Holonic MES puts in finding new solutions resembling the planning is varied. Finally, the paper reports the results of the experiments and draws conclusions.

Multi-agent coordination and control testbed for planning and scheduling strategies

The Multi-Agent Coordination and Control (MACC) testbed is a modelling and simulation environment for manufacturing control. It provides benefits to both the research community and industry. It uses a multi-agent manufacturing execution system, developed at PMA.