Emerging robot swarm traffic

We discuss traffic patterns generated by swarms of robots while commuting to and from a base station. The overall question is whether to explicitly organise the traffic or whether a certain regularity develops `naturally'. Human driven motorized traffic is rigidly structured in two lanes. However, army ants develop a three-lane pattern in their traffic, while human pedestrians generate a main trail and secondary trials in either direction. Our robot swarm approach is bottom-up: designing individual agents we first investigate the mathematics of cases occurring when applying the artificial potential field method to three 'perfect' robots. We show that traffic lane pattern will not be disturbed by the internal system of forces. Next, we define models of sensor designs to account for the practical fact that robots (and ants) have limited visibility and compare the sensor models in groups of three robots. In the final step we define layouts of a highway: an unbounded open space, a trail with surpassable edges and a hard defined (walled) highway. Having defined the preliminaries we run swarm simulations and look for emerging traffic patterns. Apparently, depending on the initial situation a variety of lane patterns occurs, however, high traffic densities do delay the emergence of traffic lanes considerably. Overall we conclude that regularities do emerge naturally and can be turned into an advantage to obtain efficient robot traffic

Experiments in cooperative human multi-robot navigation

In this paper, we consider the problem of a group of autonomous mobile robots and a human moving coordinately in a real-world implementation. The group moves throughout a dynamic and unstructured environment. The key problem to be solved is the inclusion of a human in a real multi-robot system and consequently the multiple robot motion coordination. We present a set of performance metrics (system efficiency and percentage of time in formation) and a novel flexible formation definition whereby a formation control strategy both in simulation and in real-world experiments of a human multi-robot system is presented. The formation control proposed is stable and effective by means of its uniform dispersion, cohesion and flexibility

Dynamic graph-based search in unknown environments

A novel graph-based approach to search in unknown environments is presented. A virtual geometric structure is imposed on the environment represented in computer memory by a graph. Algorithms use this representation to coordinate a team of robots (or entities). Local discovery of environmental features cause dynamic expansion of the graph resulting in global exploration of the unknown environment. The algorithm is shown to have O(k.nH) time complexity, where nH is the number of vertices of the discovered environment and 1 <= k <= nH. A maximum bound on the length of the resulting walk is given

Multi-robot team formation control in the GUARDIANS project

Purpose The GUARDIANS multi-robot team is to be deployed in a large warehouse in smoke. The team is to assist firefighters search the warehouse in the event or danger of a fire. The large dimensions of the environment together with development of smoke which drastically reduces visibility, represent major challenges for search and rescue operations. The GUARDIANS robots guide and accompany the firefighters on site whilst indicating possible obstacles and the locations of danger and maintaining communications links. Design/methodology/approach In order to fulfill the aforementioned tasks the robots need to exhibit certain behaviours. Among the basic behaviours are capabilities to stay together as a group, that is, generate a formation and navigate while keeping this formation. The control model used to generate these behaviours is based on the so-called social potential field framework, which we adapt to the specific tasks required for the GUARDIANS scenario. All tasks can be achieved without central control, and some of the behaviours can be performed without explicit communication between the robots. Findings The GUARDIANS environment requires flexible formations of the robot team: the formation has to adapt itself to the circumstances. Thus the application has forced us to redefine the concept of a formation. Using the graph-theoretic terminology, we can say that a formation may be stretched out as a path or be compact as a star or wheel. We have implemented the developed behaviours in simulation environments as well as on real ERA-MOBI robots commonly referred to as Erratics. We discuss advantages and shortcomings of our model, based on the simulations as well as on the implementation with a team of Erratics.</p

Total absolute curvature as a tool for modelling curves and surfaces

Total absolute curvature (TAC) is proposed as a tool for modelling curves and surfaces from discrete two– or three–dimensional data

On Flips in Polyhedral Surfaces: a new development

Let V be a finite point set in 3D and let ST(V ) be the set of closed triangulated polyhedral surfaces with a vertex set V. Those surfaces can be dened as 2:5D (closed) triangulations of the given discrete data set V. We generalise the operation of diagonal flip for 2:5D triangulations by omitting the usual restriction that the flip operation should not produce a self-intersecting triangulation. We denote this flip operation by EDF (extended diagonal flip). Among all possible 2:5D triangulations with the vertex set V we first single out those that are topologically equivalent to the 2D sphere. We show that any two such 2:5D triangulations (if V is situated in general position), are equivalent under EDF, i.e., they can be transformed into each other via a finite sequence of EDF

Curvature criteria to fit curves to discrete data

Several geometric criteria to fit a polygonal closed curve to discrete two-dimensional data are considered and analysed. Most of these criteria are related to the concept of curvature, for example, one criterion is minimisation of total absolute curvature. On the basis of these criteria algorithms to construct a polygonal curve which is optimal with respect to a specific criterion, are designed

Mesh optimisation based on Willmore energy

An algorithm for improving the quality of an initial triangulation on a fixed set of vertices is suggested. The edge flip operation is performed consecutively, aiming to minimise the discrete Willmore energy over a triangulated surface (or mesh). The Will- more energy of a surface is a function of Gaussian and mean curvature, and measures local deviation from a sphere. Virtual points are introduced in the triangulation to overcome the local invariance of Willmore energy under edge flips. Some experimental results are given

Modelling interaction patterns and group behaviour in a three-robot team

The research reported in this paper is part of a project investigating distributed control architec- tures for groups of autonomous robots. The focus of this paper is on modelling interaction patterns occurring in robot group behaviour. As such, we do not focus on defining control architectures for individual robots, instead, we focus on individual behaviour patterns to develop a formal theory of group behaviour resulting from multiple robot in- teraction. The problem underlying the research is that concepts relating to group behaviour have to be imposed upon the robots and the understand- ing of these patterns will lead to more efficient control and the realisation of cooperative tasks that would not be possible otherwise. The paper considers a balanced conflict in a system of three robots where action comes to a halt and a slightly deviating conflict in which action is continued in a predictable pattern. We prove how the group behaves in both types of conflicts. We introduce practical constraints of robot design such as limitations of a sensory system and discuss simulations of both types of conflicts incorporating these constraints. Having proved the behaviour of the group starting from these conflicts, the conflicts might be used to test and calibrate robots; we discuss the constraints to meet