Pesearch On Collective Construction Mechanisms In A Biologically Inspired Swarm Robotic System

A swarm robotic system is a special type of multiple robot system, which focuses on the study of how a large number of relatively simple physically embodiment agents can be designed such that the global pattern of the system emerges from the local interactions among agents and between agents and the environment. Swarm robotics takes its inspiration from biology, in particular social insects, therefore, it exhibits many functional properties including flexibility, robustness, decentralization, self-organization, etc., which are desirable properties required in many wide-ranging potential applications.Swarm robotics is a novel approach to the coordination of large number of robots. Researchers typically focus on one problem domain to study the underlying properties of system. This dissertation focuses on the problem of collective construction which is concerned with the building of a geometric structure with a collection of robots working in parallel, without centralized control. Robots in the swarm have to coordinate their building activities both in space and time such that a consistent structure can be achieved. For a given structure, how the robot can be designed such that the given structure can be built is still an open question in swarm robotics. Although it has drawn increasing attention over the last decade and many achievements have been made, swarm robotics is still a brand new research field and no systematic theoretical methodology has been established. This dissertation focuses on the coordination mechanisms involved in collective construction. The main works and contributions are summarized as follows:(1) Inspired by honeybee visual navigation behavior, a visual template mechanism is proposed in which a natural landmark serves as a visual reference or template for distance determination as well as for navigation during collective construction. This mechanism can make use of an interesting landmark, reference point or salient object in the construction environment which allows for robots manipulating homogeneous bricks in a non-communicative way. Therefore, such a mechanism has an obvious appeal to those researching collective construction for applications in unknown environments.(2) The visual template mechanism allows the robots to finish simple construction tasks. But when it comes to a more complicated task, robots would become complex. Complexity refers to the hardware and software complexity of the robots. Aiming at the drawbacks of the visual template mechanism, a spatio-temporal varying template mechanism is proposed which uses the robot itself as a template without referring to the outside world. This self-generated template varies spatially and temporally when the robot varies in position. This means the various moving pattern of the robot makes a variety of template patterns. This mechanism is a more general mechanism because it is possible for robots to build complex structures. Furthermore, the robot serving as a template is not fixed, and all the other robots could possibly become a template. This role-changing mechanism makes the system less prone to system failure when the individual malfunctions such that the robustness of the system can be increased.(3) A new spatio-temporal coordination mechanism is proposed in the case of stigmergy-based collective construction. The originality of the work lies in the increase in the capabilities of the construction robot. Endowed with the system state assessment capability, construction robots can collective build the desired structure using only a simple rule set.(4) A preliminary study of the emergence behavior in collective construction is given in a pheromone-based collective construction system. First the termite's royal chamber construction is studied and then agent-based collective construction model is abstracted and established. This model consists of two parts:one is a dynamic model of the environment and the other is an individual behavior model. Based on this model, several different objective structures are studied and how simple rules give rise to a complex global pattern is also discussed.