Anarchy, state, and utopia

Swarm robotics is an approach to collective robotics that takes inspiration from the self-organized behaviors of social animals. Through simple rules and local interactions, swarm robotics aims at designing robust, scalable, and flexible collective behaviors for the coordination of large numbers of robots. In this paper, we analyze the literature from the point of view of swarm engineering: we focus mainly on ideas and concepts that contribute to the advancement of swarm robotics as an engineering field and that could be relevant to tackle real-world applications. Swarm engineering is an emerging discipline that aims at defining systematic and well founded procedures for modeling, designing, realizing, verifying, validating, operating, and maintaining a swarm robotics system. We propose two taxonomies: in the first taxonomy, we classify works that deal with design and analysis methods; in the second taxonomy, we classify works according to the collective behavior studied. We conclude with a discussion of the current limits of swarm robotics as an engineering discipline and with suggestions for future research directions.

/pdf/swarm-robotics-a-review-from-the-swarm-engineering-46mfc058e6.pdf

Swarm robotics: a review from the swarm engineering perspective

This self-contained introduction to the distributed control of robotic networks offers a distinctive blend of computer science and control theory. The book presents a broad set of tools for understanding coordination algorithms, determining their correctness, and assessing their complexity; and it analyzes various cooperative strategies for tasks such as consensus, rendezvous, connectivity maintenance, deployment, and boundary estimation. The unifying theme is a formal model for robotic networks that explicitly incorporates their communication, sensing, control, and processing capabilities--a model that in turn leads to a common formal language to describe and analyze coordination algorithms.Written for first- and second-year graduate students in control and robotics, the book will also be useful to researchers in control theory, robotics, distributed algorithms, and automata theory. The book provides explanations of the basic concepts and main results, as well as numerous examples and exercises.Self-contained exposition of graph-theoretic concepts, distributed algorithms, and complexity measures for processor networks with fixed interconnection topology and for robotic networks with position-dependent interconnection topology Detailed treatment of averaging and consensus algorithms interpreted as linear iterations on synchronous networks Introduction of geometric notions such as partitions, proximity graphs, and multicenter functions Detailed treatment of motion coordination algorithms for deployment, rendezvous, connectivity maintenance, and boundary estimation

/pdf/distributed-control-of-robotic-networks-a-mathematical-1q6nfcvi2l.pdf

Distributed Control of Robotic Networks: A Mathematical Approach to Motion Coordination Algorithms

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http://carmenere.ucsd.edu/pdfs/DCRN-BulloCortesMartinez-bibliography.pdf

Distributed Control of Robotic Networks

This paper is concerned with the collective behavior of a group of n > 1 mobile autonomous agents, labelled 1 through n, which can all move in the plane. Each agent is able to continuously track the positions of all other agents currently within its "sensing region" where by an agent's sensing region is meant a closed disk of positive radius r centered at the agent's current position. The multi-agent rendezvous problem is to devise "local" control strategies, one for each agent, which without any active communication between agents, cause all members of the group to eventually rendezvous at single unspecified location. This paper describes two types of strategies for solving the problem. The first consists of agent strategies, which are mutually synchronized, in the sense that all depend on a common clock. The second consists of strategies, which can be implemented independent of each other, without reference to a common clock.

http://www.eeci-institute.eu/GSC2012/Photos-EECI/EECI-GSC-2012-M15/handout2/rendezvous/Rend.sync.cdc.pdf

The multi-agent rendezvous problem

Shape formation has been recently studied in distributed systems of programmable particles. In this paper we consider the shape recovery problem of restoring the shape when f of the n particles have crashed. We focus on the basic line shape, used as a tool for the construction of more complex configurations.We present a solution to the line recovery problem by the non-faulty anonymous particles; the solution works regardless of the initial distribution and number f

Line Recovery by Programmable Particles

Over the past few years, the focus of robotic design has been moving from a scenario where a few specialized (and expensive) units were used to solve a variety of tasks, to a scenario where many general purpose (and cheap) units are used to achieve some common goal. Consequently, part of the focus has been to understand better how to coordinate and control a set of such “simpler” mobile units efficiently. Studies can be found in different disciplines, from engineering to artificial life: a shared feature of the majority of these works has been the design of algorithms based on heuristics, with no main concern on their correctness and termination. Few researchers have focused on trying to model formally an environment constituted by mobile units, analyzing which kind of capabilities they must have in order to achieve their goals; in other words, to study the problem from a computational point of view. In this paper we do a direct comparison between two models, ATOM and CORDA, introduced in two studies leading in this direction. First their main features are described, and then the main differences are highlighted, showing the relationship between the class of problems solvable in the two models.

The Effect of Synchronicity on the Behavior of Autonomous Mobile Robots

The gathering problem requires a set of mobile agents, arbitrarily positioned at different nodes of a network to group within finite time at the same location, not fixed in advanced. 
The extensive existing literature on this problem shares the same fundamental assumption: the topological structure does not change during the rendezvous or the gathering; this is true also for those investigations that consider faulty nodes. In other words, they only consider static graphs. In this paper we start the investigation of gathering in dynamic graphs, that is networks where the topology changes continuously and at unpredictable locations. 
We study the feasibility of gathering mobile agents, identical and without explicit communication capabilities, in a dynamic ring of anonymous nodes; the class of dynamics we consider is the classic 1-interval-connectivity. 
We focus on the impact that factors such as chirality (i.e., a common sense of orientation) and cross detection (i.e., the ability to detect, when traversing an edge, whether some agent is traversing it in the other direction), have on the solvability of the problem. We provide a complete characterization of the classes of initial configurations from which the gathering problem is solvable in presence and in absence of cross detection and of chirality. The feasibility results of the characterization are all constructive: we provide distributed algorithms that allow the agents to gather. In particular, the protocols for gathering with cross detection are time optimal. We also show that cross detection is a powerful computational element. 
We prove that, without chirality, knowledge of the ring size is strictly more powerful than knowledge of the number of agents; on the other hand, with chirality, knowledge of n can be substituted by knowledge of k, yielding the same classes of feasible initial configurations.

Gathering in Dynamic Rings

Consider a set of $n\neq 4$ simple autonomous mobile robots (decentralized, asynchronous, no common coordinate system, no identities, no central coordination, no direct communication, no memory of the past, deterministic) initially in distinct locations, moving freely in the plane and able to sense the positions of the other robots. We study the primitive task of the robots arranging themselves equally spaced along a circle not fixed in advance (Uniform Circle Formation). In the literature, the existing algorithmic contributions are limited to restricted sets of initial configurations of the robots and to more powerful robots. The question of whether such simple robots could deterministically form a uniform circle has remained open. In this paper, we constructively prove that indeed the Uniform Circle Formation problem is solvable for any initial configuration of the robots without any additional assumption. In addition to closing a long-standing problem, the result of this paper also implies that, for pattern formation, asynchrony is not a computational handicap, and that additional powers such as chirality and rigidity are computationally irrelevant.

Distributed Computing by Mobile Robots: Solving the Uniform Circle Formation Problem

The Rendezvous of anonymous mobile agents in a anonymous network is an intensively studied problem; it calls for k anonymous, mobile agents to gather in the same site. We study this problem when in the network there is a black hole: a stationary process located at a node that destroys any incoming agent without leaving any trace. The presence of the black hole makes it clearly impossible for all agents to rendezvous. So, the research concern is to determine how many agents can gather and under what conditions. In this paper we consider k anonymous, asynchronous mobile agents in an anonymous ring of size n with a black hole; the agents are aware of the existence, but not of the location of such a danger. We study the rendezvous problem in this setting and establish a complete characterization of the conditions under which the problem can be solved. In particular, we determine the maximum number of agents that can be guaranteed to gather in the same location depending on whether k or n is unknown (at least one must be known for any non-trivial rendezvous). These results are tight: in each case, rendezvous with one more agent is impossible. All our possibility proofs are constructive: we provide mobile agents protocols that allow the agents to rendezvous or near-gather under the specified conditions. The analysis of the time costs of these protocols show that they are optimal. Our rendezvous protocol for the case when k is unknown is also a solution for the black hole location problem. Interestingly, its bounded time complexity is Θ(n); this is a significant improvement over the O(n log n) bounded time complexity of the existing protocols for the same case.

Giuseppe Prencipe

Papers

Line Recovery by Programmable Particles

The Effect of Synchronicity on the Behavior of Autonomous Mobile Robots

Gathering in Dynamic Rings

Distributed Computing by Mobile Robots: Solving the Uniform Circle Formation Problem

Multiple agents Rendezvous in a ring in spite of a black hole