Safety in Numbers: Fault Tolerance in Robot Swarms

The swarm intelligence literature frequently asserts that swarms exhibit high levels of robustness. That claim is, however, rather less frequently supported by empirical or theoretical analysis. But what do we mean by a 'robust' swarm? How would we measure the robustness or – to put it another way – fault-tolerance of a robotic swarm? These questions are not just of academic interest. If swarm robotics is to make the transition from the laboratory to real-world engineering implementation, we would need to be able to address these questions in a way that would satisfy the needs of the world of safety certification. This paper explores fault-tolerance in robot swarms through Failure Mode and Effect Analysis (FMEA) and reliability modelling. The work of this paper is illustrated by a case study of a wireless connected robot swarm, employing both simulation and real-robot laboratory experiments

AVI as a mechanical tool for studying thin-shells based on Kirchhoff-Love constraints

Thin-shell and rod theory using discrete mechanics applied to structures in civil engineering. The aim is to apply structure preserving algorithms to concrete problems in construction. The major objectives of this interdisciplinary work is the search and the development of a practical tool to study irregular surfaces

Code and its image: the functions of text and visualisation in a code-based design studio

Traditionally, design learning in the architecture studio has taken place through a combination of individual work and joint projects. The introduction of code-based design practices in the design studio has altered this balance, introducing new models of joint authorship and new ways for individuals to contribute to co-authored projects. This paper presents a case study describing four design studios in a higher education setting that used code as a tool for generating architectural geometry. The format of the studios encouraged the students to reflect critically on their role as authors and to creatively address the multiple opportunities for shared authorship available with code-based production. The research question addressed in this study involved the role of code-based practices in altering the model of architectural education in the design studio, in particular the role of visual representations of a code-based design process in the production of shared knowledge

Assembly of Configurations in a Networked Robotic System: A Case Study on a Reconfigurable Interactive Table Lamp

In the present study, we are interested in verifying how the progressive addition of constraints on communication and localization impact the performance of a swarm of small robots in shape formation tasks. Identified to be of importance in a swarm-user interaction context, the time required to construct a given spatial configuration is considered as a performance metric. The experimental work reported in this paper starts from global and synchronized localization information, shown to be successful both on a real hardware system and in simulation. In a second step, communication is constrained to a local scale, thus obliging a single designated robot to disseminate the global localization information to the other agents. The reliability of the radio communication channel and its impact upon the performance of the system are considered

Asynchronous variational integrators as a mechanical tool for dimensioning thin-shell structures

Thin-shell and rod theory using discrete mechanics applied to structures in civil engineering. The aim is to apply structure preserving algorithms to concrete problems in construction. The major objectives of this interdisciplinary work is the search and the development of a practical tool to study irregular surfaces

Flexible beam in R3 under large overall motions and Asynchronous Variational Integrators

The theory of discrete variational mechanics has its roots in the optimal control literature of the 1960's. The past ten years have seen a major development of discrete variational mechanics and corresponding numerical integrators, due largely to pioneering work by Jerrold Marsden and his collaborators at Caltech. Discrete mechanics emerged from the interplay of classical theoretical mechanics, numerical analysis, and computer science. Recent years have seen an explosive growth of research in discrete mechanics, discrete exterior calculus, and corresponding integrators capable of preserving geometric structure in mechanical systems. There has been a growing realization that stability of numerical methods can be obtained by methods which are compatible with these structures in the sense that many discrete variational integrators are symplectic-momentum methods. That is, they preserve the symplectic structure of phase space and momentum maps arising from the symmetries and invariants of the system. Moreover asynchronous variational integrators (AVI) conserve energy. Remarkably, to our knowledge, there is no major application of these discrete mechanics techniques to civil engineering. In particular, we are not aware of any application of discrete mechanics to the study of beams and surfaces formed by elements tied by multi-edges, exhibiting sharp corners under constraints and with large deflections. Applying geometric mechanics methods that can more faithfully recapitulate global behavior by decoupling it from constraints for local accuracy permits the development of dynamic modeling and static two-dimensional simulations

Modelling a wireless connected swarm of mobile robots

It is a characteristic of swarm robotics that modelling the overall swarm behaviour in terms of the low-level behaviours of individual robots is very difficult. Yet if swarm robotics is to make the transition from the laboratory to real-world engineering realisation such models would be critical for both overall validation of algorithm correctness and detailed parameter optimisation. We seek models with predictive power: models that allow us to determine the effect of modifying parameters in individual robots on the overall swarm behaviour. This paper presents results from a study to apply the probabilistic modelling approach to a class of wireless connected swarms operating in unbounded environments. The paper proposes a probabilistic finite state machine (PFSM) that describes the network connectivity and overall macroscopic behaviour of the swarm, then develops a novel robot-centric approach to the estimation of the state transition probabilities within the PFSM. Using measured data from simulation the paper then carefully validates the PFSM model step by step, allowing us to assess the accuracy and hence the utility of the model. © Springer Science + Business Media, LLC 2008