Simple yet stable bearing-only navigation

This article describes a simple monocular navigation system for a mobile robot based on the map-and-replay technique. The presented method is robust and easy to implement and does not require sensor calibration or structured environment, and its computational complexity is independent of the environment size. The method can navigate a robot while sensing only one landmark at a time, making it more robust than other monocular approaches. The aforementioned properties of the method allow even low-cost robots to effectively act in large outdoor and indoor environments with natural landmarks only. The basic idea is to utilize a monocular vision to correct only the robot's heading, leaving distance measurements to the odometry. The heading correction itself can suppress the odometric error and prevent the overall position error from diverging. The influence of a map-based heading estimation and odometric errors on the overall position uncertainty is examined. A claim is stated that for closed polygonal trajectories, the position error of this type of navigation does not diverge. The claim is defended mathematically and experimentally. The method has been experimentally tested in a set of indoor and outdoor experiments, during which the average position errors have been lower than 0.3 m for paths more than 1 km long

Design and construction of a configurable full-field range imaging system for mobile robotic applications

Mobile robotic devices rely critically on extrospection sensors to determine the range to objects in the robot’s operating environment. This provides the robot with the ability both to navigate safely around obstacles and to map its environment and hence facilitate path planning and navigation. There is a requirement for a full-field range imaging system that can determine the range to any obstacle in a camera lens’ field of view accurately and in real-time. This paper details the development of a portable full-field ranging system whose bench-top version has demonstrated sub-millimetre precision. However, this precision required non-real-time acquisition rates and expensive hardware. By iterative replacement of components, a portable, modular and inexpensive version of this full-field ranger has been constructed, capable of real-time operation with some (user-defined) trade-off with precision

BRAHMS: Novel middleware for integrated systems computation

Biological computational modellers are becoming increasingly interested in building large, eclectic models, including components on many different computational substrates, both biological and non-biological. At the same time, the rise of the philosophy of embodied modelling is generating a need to deploy biological models as controllers for robots in real-world environments. Finally, robotics engineers are beginning to find value in seconding biomimetic control strategies for use on practical robots. Together with the ubiquitous desire to make good on past software development effort, these trends are throwing up new challenges of intellectual and technological integration (for example across scales, across disciplines, and even across time) - challenges that are unmet by existing software frameworks. Here, we outline these challenges in detail, and go on to describe a newly developed software framework, BRAHMS. that meets them. BRAHMS is a tool for integrating computational process modules into a viable, computable system: its generality and flexibility facilitate integration across barriers, such as those described above, in a coherent and effective way. We go on to describe several cases where BRAHMS has been successfully deployed in practical situations. We also show excellent performance in comparison with a monolithic development approach. Additional benefits of developing in the framework include source code self-documentation, automatic coarse-grained parallelisation, cross-language integration, data logging, performance monitoring, and will include dynamic load-balancing and 'pause and continue' execution. BRAHMS is built on the nascent, and similarly general purpose, model markup language, SystemML. This will, in future, also facilitate repeatability and accountability (same answers ten years from now), transparent automatic software distribution, and interfacing with other SystemML tools. (C) 2009 Elsevier Ltd. All rights reserved

Towards an Autonomous Walking Robot for Planetary Surfaces

In this paper, recent progress in the development of the DLR Crawler - a six-legged, actively compliant walking robot prototype - is presented. The robot implements a walking layer with a simple tripod and a more complex biologically inspired gait. Using a variety of proprioceptive sensors, different reflexes for reactively crossing obstacles within the walking height are realised. On top of the walking layer, a navigation layer provides the ability to autonomously navigate to a predefined goal point in unknown rough terrain using a stereo camera. A model of the environment is created, the terrain traversability is estimated and an optimal path is planned. The difficulty of the path can be influenced by behavioral parameters. Motion commands are sent to the walking layer and the gait pattern is switched according to the estimated terrain difficulty. The interaction between walking layer and navigation layer was tested in different experimental setups

Design of Interactive Service Robots applying methods of Systems Engineering and Decision Making

Interaktive Service Roboter werden heute bereits in einigen Anwendungsszenarien eingesetzt, in denen sie beispielsweise Menschen durch Gebäude geleiten oder bei häuslichen Aufgaben unterstützen. Dennoch gibt es bislang kein System, das den erwarteten Marktdurchbruch geschafft hat. Die hohe Komplexität solcher Systeme und vielfältige Anforderungen durch Benutzer und Betreiber erschweren die Entwicklung von erfolgreichen Service Robotern. In dieser Arbeit wurden zwei interaktive Service Roboter entwickelt, die das Potential haben, die beschriebenen Hinderungsgründe für einen breiten Einsatz zu überwinden. Das erste Robotersystem wurde als Shopping Roboter für Baumärkte entwickelt, in denen es Kunden zu gesuchten Produkten führt. Das zweite System dient als interaktiver Pflegeroboter älteren Menschen in häuslicher Umgebung bei der Bewältigung täglicher Aufgaben. Diese Arbeit beschreibt die Realisierung der Embedded Systems beider Robotersysteme und umfasst insbesondere die Entwicklung der Low-Level System Architekturen, Energie Management Systeme, Kommunikationssysteme, Sensorsysteme, sowie ausgewählte Aspekte der mechanischen Umsetzung. Die Entwicklung einer Vielzahl von Steuerungsmodulen, notwendig für die Realisierung interaktiver Service Roboter, wird beschrieben. Die vorliegende Arbeit verwendet und erweitert Methoden des Systems Engineerings, um die hohe Systemkomplexität von interaktiven Service Robotern sowie die vielfältigen Anforderungen an deren späteren Einsatz beherrschen zu können. Der Entwicklungsprozess der beiden Roboter basiert auf dem V-Model, welches einen strukturierten Entwurfsablauf unter Berücksichtigung aller Systemanforderungen erlaubt. Es zwingt ferner zur frühzeitigen Spezifikation von Prüfabläufen, was die Qualität und Zuverlässigkeit der Entwicklungsergebnisse verbessert. Für die Unterstützung von Entscheidungen im Entwicklungsprozess schlägt diese Arbeit eine Kombination aus dem V-Model und dem Analytic Hierarchy Process (AHP) vor. Der AHP hilft bei der Auswahl verfügbarer technischer Alternativen unter Berücksichtigung von Prioritäten im Entwicklungsprozess. Diese Arbeit spezifiziert sieben Kriterien, die Service Roboter charakterisieren: Anpassbarkeit, Laufzeit, Benutzbarkeit, Robustheit, Sicherheit, Features und Kosten. Die Prioritäten dieser Kriterien im Entwicklungsprozess werden für jeden Roboter individuell bestimmt. Der AHP ermittelt die beste Lösung basierend auf diesen gewichteten Kriterien und den bewerteten technischen Alternativen. Die Einbindung des AHP in den V-Model Prozess wurde am Entwurf des Shopping Roboter entwickelt und geprüft. Die Allgemeingültigkeit dieser Methode wurde während der Entwicklung des Pflegeroboters verifiziert.Interactive service robots have already been developed and operate as example installations taking over guidance tasks or serving as home assistants. However, none of these systems have become an off-the-shelf product or have achieved the predicted breakthrough so far. The challenges of the design of such systems are, on the one hand, the combination of cutting edge technologies to a complex product; on the other hand, the consideration of requirements important for the later marketing during the design process. In the framework of this dissertation, two interactive service robot systems are developed that have the potential to overcome current market entry barriers. These robots are designed to operate in two different environments: one robot guides walked-in users in large home improvement stores to requested product locations and interacts with the customer to provide product information; the other robot assists elderly people to stay longer in their homes and takes over home-care tasks. This work describes the realization of the embedded systems of both robots. In particular, the design of low-level system architectures, energy management systems, communication systems, sensor systems, and selected aspects of mechanical implementations are carried out in this work. Multiple embedded system modules are developed for the control of the robots' functionalities; the development processes as well as the composition and evaluation of these modules are presented in this work. To cope with the complexity and the various factors that are important for the design of the robots, this thesis applies and further develops system engineering methods. The development process is based on the V-Model system design method. The V-Model helps to structure the design process under consideration of all system requirements. It involves evaluation procedures at all design levels, and thus increases the quality and reliability of the development outputs. To support design decisions, this thesis proposes to combine the V-Model with the Analytic Hierarchy Process (AHP) method. The AHP helps to evaluate technical alternatives for design decisions according to overall criteria, a system has to fulfill. This thesis defines seven criteria that characterize a service robot: Adaptability, Operation Time, Usability, Robustness, Safeness, Features, and Costs. These criteria are weighted for each individual robot application. The AHP evaluates technical design alternatives based on the weighted criteria to reveal the best technical solution. The integration of the AHP into the V-Model development is tested and improved during the design process of the shopping robot system. The generality of this combined systematic design approach is validated during the design of the home-care robot system

Machine Vision for intelligent Semi-Autonomous Transport (MV-iSAT)

AbstractThe primary focus was to develop a vision-based system suitable for the navigation and mapping of an indoor, single-floor environment. Devices incorporating an iSAT system could be used as ‘self-propelled’ shopping carts in high-end retail stores or as automated luggage routing systems in airports. The primary design feature of this system is its Field Programmable Gate Array (FPGA) core, chosen for its strengths in parallelism and pipelining. Image processing has been successfully demonstrated in real-time using FPGA hardware. Remote feedback and monitoring was broadcasted to a host computer via a local area network. Deadlines as short as 40ns have been met by a custom built memory-based arbitration scheme. It is hoped that the iSAT platform will provide the basis for future work on advanced FPGA-based machine-vision algorithms for mobile robotics

Ultra Wide-Band Localization and SLAM: A Comparative Study for Mobile Robot Navigation

In this work, a comparative study between an Ultra Wide-Band (UWB) localization system and a Simultaneous Localization and Mapping (SLAM) algorithm is presented. Due to its high bandwidth and short pulses length, UWB potentially allows great accuracy in range measurements based on Time of Arrival (TOA) estimation. SLAM algorithms recursively estimates the map of an environment and the pose (position and orientation) of a mobile robot within that environment. The comparative study presented here involves the performance analysis of implementing in parallel an UWB localization based system and a SLAM algorithm on a mobile robot navigating within an environment. Real time results as well as error analysis are also shown in this work