Skip to main content

2015 | Buch

Distributed Consensus with Visual Perception in Multi-Robot Systems

insite
SUCHEN

Über dieses Buch

This monograph introduces novel responses to the different problems that arise when multiple robots need to execute a task in cooperation, each robot in the team having a monocular camera as its primary input sensor. Its central proposition is that a consistent perception of the world is crucial for the good development of any multi-robot application. The text focuses on the high-level problem of cooperative perception by a multi-robot system: the idea that, depending on what each robot sees and its current situation, it will need to communicate these things to its fellows whenever possible to share what it has found and keep updated by them in its turn. However, in any realistic scenario, distributed solutions to this problem are not trivial and need to be addressed from as many angles as possible.
Distributed Consensus with Visual Perception in Multi-Robot Systems covers a variety of related topics such as:
• distributed consensus algorithms;
• data association and robustness problems;
• convergence speed; and
• cooperative mapping.
The book first puts forward algorithmic solutions to these problems and then supports them with empirical validations working with real images. It provides the reader with a deeper understanding of the problems associated to the perception of the world by a team of cooperating robots with onboard cameras.

Academic researchers and graduate students working with multi-robot systems, or investigating problems of distributed control or computer vision and cooperative perception will find this book of material assistance with their studies.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Introduction
Abstract
The first chapter of this book is devoted to discuss the concept of a multi-robot system and its applications in our society. Then, we analyze the implications of using vision sensors in such systems and the problems that need to be addressed in such a setup. Finally, the chapter presents a detailed outline of the rest of the chapters of the book, including a high level description of the particular topics treated inside them.
Eduardo Montijano, Carlos Sagüés
Chapter 2. Robotic Networks and the Consensus Problem
Abstract
This chapter introduces the necessary concepts to understand the topics studied in the book. We provide the basic definitions to characterize a robotic network. First, we describe the robots we will use and their way to interact with each other and with the world. Then, we express the communications of the network using fixed and time-varying graphs and we give some definitions of interest. After that, in the chapter we review the distributed algorithms based on linear iterations and the application of this kind of algorithms to achieve the consensus using different weights. To conclude the chapter, we show some examples of different consensus applications solved using linear iterations.
Eduardo Montijano, Carlos Sagüés
Chapter 3. The Data Association Problem
Abstract
“It is said that one image is worth a thousand words.” In order to reach a consensus, the first required step for the team of robots is to globally identify these “words.” In this chapter we address the problem of finding global correspondences between the observations of all the robots in a distributed manner. At the beginning, each robot finds correspondences only with the robots that can directly communicate with it. This is done using existing matching techniques for pairs of images. After that, we study a distributed algorithm that propagates the local correspondences through the network. We formally demonstrate the main properties of the algorithm and prove that after executing our method, the team of robots finishes with a globally consistent data association. The performance of the algorithm is tested with extensive simulations and real images at the end of the chapter.
Eduardo Montijano, Carlos Sagüés
Chapter 4. D-RANSAC: Distributed Robust Consensus
Abstract
“Robustness is the ability of a system to cope with errors during the execution.” This property is essential in any robotic system. A reliable robotic network must be able to fuse its perception of the world in a robust way. Data association mistakes and measurement errors are some of the factors that can contribute to an incorrect consensus value. In this chapter, we present a distributed scheme for robust consensus in autonomous robotic networks. The method is inspired by the RANdom SAmple Consensus (RANSAC) algorithm. We study a distributed version of this algorithm that enables the robots to detect and discard the outlier observations during the computation of the consensus. The basic idea is to generate different hypotheses and vote for them using a dynamic consensus algorithm. Assuming that at least one hypothesis is initialized with only inliers, we show theoretically and with simulations that the studied method converges to the consensus of the inlier observations.
Eduardo Montijano, Carlos Sagüés
Chapter 5. Fast Consensus with Chebyshev Polynomials
Abstract
“No matter how fast your computer system runs, you will eventually think of it as slow.” When the number of robots in the network is large, distributed averaging methods usually have a slow convergence rate. In this chapter, we analyze the use of Chebyshev polynomials in the distributed consensus problem to reduce the number of iterations required to achieve a good consensus. We present a distributed linear iteration using these polynomials that compared to other approaches, is able to achieve the average of the initial conditions in a small number of iterations. In this chapter we characterize the main properties of the algorithm for both, fixed and switching communication topologies. Additionally, we provide a second algorithm for the adaptive selection of the parameters to optimize the convergence rate. We validate the studied method with extensive simulations.
Eduardo Montijano, Carlos Sagüés
Chapter 6. Cooperative Topological Map Building Using Distributed Consensus
Abstract
“A good map is both a useful tool and a magic carpet to far away places.” We have studied how to modify the consensus iteration to handle different perception issues. In this chapter we present an application of such algorithms in the problem of cooperative mapping with cameras. The approach builds topological maps from the sequences of images acquired by each robot, grouping the features in planar regions and fusing them using consensus. The use of planar regions to represent the map has many advantages both in the mapping task and in the achievement of the consensus. First of all, using inter-image homographies, the individual maps are easy to create and the data association between different maps is simple. The computation of a global reference frame to represent the features, which is in general quite complicated, but necessary to reach a consensus, is reduced to a simple max-consensus method multiplying different homographies. Finally, homographies between images can be computed without knowing the internal parameters of the cameras, which makes the approach robust to calibration issues. The result is a simple but very effective distributed algorithm that creates a global map using the information of all the robots. Experiments with real images in complex scenarios show the good performance of the studied distributed solution.
Eduardo Montijano, Carlos Sagüés
Chapter 7. Conclusions
Abstract
“It’s all said and done, it’s real, and it’s been fun.” In this book we have studied different topics to develop a set of distributed algorithms that allow a team of robots equipped with monocular cameras achieve a consensus in different perception tasks. We have placed a great effort in three issues related with this problem, the data association of the features observed by the different robots, the identification of the outliers and the convergence speed to reach the consensus. Then we have used these algorithms to study a distributed solution based on consensus to the problem of cooperatively build a topological map of the environment. Conclusions obtained throughout this work are finally summarized in this chapter.
Eduardo Montijano, Carlos Sagüés
Backmatter
Metadaten
Titel
Distributed Consensus with Visual Perception in Multi-Robot Systems
verfasst von
Eduardo Montijano
Carlos Sagüés
Copyright-Jahr
2015
Electronic ISBN
978-3-319-15699-6
Print ISBN
978-3-319-15698-9
DOI
https://doi.org/10.1007/978-3-319-15699-6

Neuer Inhalt