Collective behavior based on self-organization has been shown in group-living animals from insects to vertebrates. These findings have stimulated engineers to investigate approaches for the coordination of autonomous multirobot systems based on self-organization. In this experimental study, we show collective decision-making by mixed groups of cockroaches and socially integrated autonomous robots, leading to shared shelter selection. Individuals, natural or artificial, are perceived as equivalent, and the collective decision emerges from nonlinear feedbacks based on local interactions. Even when in the minority, robots can modulate the collective decision-making process and produce a global pattern not observed in their absence. These results demonstrate the possibility of using intelligent autonomous devices to study and control self-organized behavioral patterns in group-living animals.

Abstract-This paper presents a detailed characterization of the Hokuyo URG-04LX 2D laser range finder. While the sensor specifications only provide a rough estimation of the sensor accuracy, the present work analyzes issues such as time drift effects and dependencies on distance, target properties (color, brightness and material) as well as incidence angle. Since the sensor is intended to be used for measurements of a tubelike environment on an inspection robot, the characterization is extended by investigating the influence of the sensor orientation and dependency on lighting conditions. The sensor characteristics are compared to those of the Sick LMS 200 which is commonly used in robotic applications when size and weight are not critical constraints. The results show that the sensor accuracy is strongly depending on the target properties (color, brightness, material) and that it is consequently difficult to establish a calibration model. The paper also identifies cases for which the sensor returns faulty measurements, mainly when the surface has low reflectivity (dark surfaces, foam) or for high incidence angles on shiny surfaces. On the other hand, the repeatability of the sensor seems to be competitive with the LMS 200.

This paper describes the Magnebike robot, a compact robot with two magnetic wheels in a motorbike arrangement, which is intended for inspecting the inner casing of ferromagnetic pipes with complex-shaped structures. The locomotion concept is based on an adapted magnetic wheel unit integrating two lateral lever arms. These arms allow for slight lifting off the wheel in order to locally decrease the magnetic attraction force when passing concave edges, as well as laterally stabilizing the wheel unit. The robot has the main advantage of being compact (180 × 130 × 220 mm) and mechanically simple: it features only five active degrees of freedom (two driven wheels each equipped with an active lifter stabilizer and one steering unit). The paper presents in detail design and implementation issues that are specific to magnetic wheeled robots. Low-level control functionalities are addressed because they are necessary to control the active system. The paper also focuses on characterizing and analyzing the implemented robot. The high mobility • Journal of Field Robotics-2009is shown through experimental results: the robot not only can climb vertical walls and follow circumferential paths inside pipe structures but it is also able to pass complex combinations of 90-deg convex and concave ferromagnetic obstacles with almost any inclination regarding gravity. It requires only limited space to maneuver because turning on the spot around the rear wheel is possible. This high mobility enables the robot to access any location in the specified environment. Finally the paper analyzes the maximum payload for different types of environment complexities because this is a key feature for climbing robots and provides a security factor about the risk of falling and slipping. C 2009 Wiley Periodicals, Inc.

S u m m a r y . This paper describes a novel solution to a mobile climbing robot on magnetic wheels, designed for inspecting the interior surfaces in gas tanks made out of thin metal sheets. These surfaces were inaccessible by previous climbing robots due to the following restrictions: 1. Ridges, where the magnetic force decreases to almost zero 2. Angular transitions between the surfaces (135°) 3. Thin metal sheets that cannot provide high magnetic forces The main optimization criterion for this robot was to design it as light as possible, as the surface was also considered to be very fragile. As the here described type of application is very special and was not examined much in previous publications, this work also stresses on the early analysis phase. This phase mainly consists of tests to optimize magnetic wheels for thin surfaces and mechanical calculations for robots on magnetic wheels. The chosen concept is described in detail, explaining how the robot moves around and passes the obstacles. The analysis of the most critical cases is presented, as well as some details about magnetic wheels and actuators.

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Abstract-This paper describes a novel magnetic wheel unit integrating a mechanism that can be used for lifting and stabilizing the unit. The mechanism consists of 2 active lever arms mounted on each side of the wheel and rotating coaxially with the wheel. This mechanism allows slightly lifting the magnetic wheel at any desired position on the wheel circumference and consequently decreasing the magnetic force at this specific location. The same mechanism can also be used to stabilize the wheel, when external forces are unfavorable. This paper also describes the potential of this concept for in-pipe inspection technologies. Indeed it can be used to increase the mobility of magnetic wheels robots which are currently not able to negotiate complex obstacles. At the same time, it allows building smaller robots, since the self stabilizer system allows reducing the amount of required magnetic wheels to only two units.

The MagneBike inspection robot is a climbing robot equipped with magnetic wheels. The robot is designed to drive on three-dimensional (3D) complexly shaped pipe structures; therefore it is necessary to provide 3D visualization tools for the user, who remotely controls the robot out of sight. The localization system is required to provide a 3D map of the unknown environment and the 3D location of the robot in the environment's map. The localization strategy proposed in this paper consists of combining 3D odometry with 3D scan registration. The odometry model is based on wheel encoders and a three-axis accelerometer. Odometry enables the tracking of the robot trajectory between consecutive 3D scans and is used as a prior for the scan matching algorithm. The 3D scan registration facilitates the construction of a 3D map of the environment and refines the robot position computed with odometry. This paper describes in detail the implementation of the localization concept. It presents the lightweight, small-sized 3D range finder that has been developed for the MagneBike. It also proposes an innovative 3D odometry model that estimates the local surface curvature to compensate for the absence of angular velocity inputs. The different tools are characterized in detail based on laboratory and field experiments. They show that the localization concepts reliably track the robot moving in the specific application environment. We also describe various techniques to optimize the 3D scanning process, which is time consuming, and to compensate for the identified limitations. These techniques are useful inputs for the future automatization of the robot's control and optimization of its localization process. C 2010 Wiley Periodicals, Inc.The MagneBike application implies 3D localization in a new type of environment for mobile robots. In this section, we describe the specifics of this environment and the required accuracy of the localization system. Once the constraints are presented, related work is discussed and a localization strategy is proposed. The MagneBike's Environment: Specificity and RequirementsThe environment specifications were presented in a paper primarily focusing on requirements and constraints for the locomotion system. Typical environments ( Figure 3) are analyzed again, but this time from the point of view of the localization problem. The following constraints are important because they differ from the conventional indoor and outdoor robotic applications:a. The robot drives in a confined space. It is then important to provide a 3D visualization tool to the user who cannot see the robot at all once it has entered the structure.

Abstract-Climbing is a challenging task for autonomous mobile robots primarily due to requirements for agile locomotion, and high maneuverability as well as robust and efficient attachment and detachment. A novel miniature wall-climbing robot is proposed. The robot is adapted for the wall-climbing task by taking advantage of down scaling and its low design. Challenges encountered during robot miniaturization and performances of the robot are reported. The miniature robot prototype proved to be able to climb on inclined surfaces with a slope of up to 90° at a speed of 3.3mm/s. It is equipped with sensors that enable it to avoid obstacles, follow walls and detect free-falls. It can be controlled by remote control or act autonomously. Animals, such as Geckos, have developed amazing climbing ability through micro-and nano-fibers on their feet. These structures have inspired the study of dry adhesion and the design of synthetic fibrillar pads presented in the paper.