Emotional Intervention on Stigmergy Based Foraging Behaviour of Immune Network Driven Mobile Robots

Abstract

Stigmergy is an indirect means of communication between multiple agents, involving modifications made to the environment. The agents are programmed so that they obey a simple set of rules and recognize local information to perform a small task. The agent carrying out its task, makes changes in the environment, which stimulates another (or the same) agent to continue working on the task. The environment itself acts as a shared external memory in the context of the system as a whole. The mechanism of stigmergy, combined with environmental physics, provides the basic elements of self-organization. Selforganization is a set of dynamical mechanisms whereby structures appear at the global level of a system as a result from interactions among its lower-level components However, the relationship between local and global types of behaviour is not easy to understand and small changes at a local level might result in drastic and sometimes unpredictable changes at the global level. Four basic ingredients and three characteristic features (signatures) of self-organization have been identified. The ingredients are: positive feedback, negative feedback, amplification of fluctuations and presence of multiple interactions; the signatures are: creation of spatiotemporal structures in an initially homogeneous medium, possible attainability of different stable states, and existence of parametrically determined bifurcations Stigmergic concepts have been successfully applied to a variety of engineering fields such as combinatorial optimization In robotics, by means of simulated robot teams The robots have been equipped with two infra-red (IR) sensors, a gripper for pushing objects around, and a switching mechanism, which can sense the local concentration of objects only as below or above a fixed threshold. They have obeyed very simple behavioural rules and have required no capacity for spatial orientation and memory. Holland & Melhuish (1999) have proposed a very similar approach that examines the operation of stigmergy and self-organization in a homogeneous group of physical robots, in the context of the task of clustering and sorting objects (Frisbees) of two different types. Stigmergy fits excellently into the behaviour-based robot control architecture, which is robust and flexible against the continually changing world. The real-world physics of the environment may be a critical factor for a system level behaviour to emerge. Simulation can provide a picture of possibilities for emergent behaviour. But the use of simulation means that the system is not "grounded" and is unable to exploit the real world physics of the environment. It is for this reason that some authors However, the evolutionary simulation is perhaps the best methodology for the moment for investigating stigmergic phenomena in general, as the real experiments are expensive, time consuming and destructive. Experiments, similar to those, reported by Stigmergy based foraging robots need random movements in order to ensure exploration of all the places of the arena within a www.intechopen.com