The biology and technology of intelligent autonomous agents

Guest editorial.We thank Dr. L. Veiga da Cunha, director of the NATO ASI program for the support throughout the whole administrative process associated with the Nato funding. This funding is hereby gratefully acknowledged.Peer Reviewe

Analysing the relative importance of robot brains and bodies

The evolution of robots, when applied to both the morphologies and the controllers, is not only a means to obtain high-quality robot designs, but also a process that results in many body-brain-fitness data points. Inspired by this perspective, in this paper we investigate the relative importance of robot bodies and brains for a good fitness. We introduce a method to isolate and quantify the effect of the bodies and brains on the quality of the robots and perform a case study. The method is general in that it is not restricted to evolutionary systems. For the case study, we use a system of modular robots, where the bodies are evolvable and the brains are evolvable and learnable. These case studies validate the usefulness of our method and deliver interesting insights into the interplay between bodies and brains in evolutionary robotics

Complexity Measures: Open Questions and Novel Opportunities in the Automatic Design and Analysis of Robot Swarms

Complexity measures and information theory metrics in general have recently been attracting the interest of multi-agent and robotics communities, owing to their capability of capturing relevant features of robot behaviors, while abstracting from implementation details. We believe that theories and tools from complex systems science and information theory may be fruitfully applied in the near future to support the automatic design of robot swarms and the analysis of their dynamics. In this paper we discuss opportunities and open questions in this scenario

Analysis of Embodied and Situated Systems from an Antireductionist Perspective

The analysis of embodied and situated agents form a dynamical system perspective is often limited to a geometrical and qualitative description. However, a quantitative analysis is necessary to achieve a deep understanding of cognitive facts. The field of embodied cognition is multifaceted, and the first part of this thesis is devoted to exploring the diverse meanings proposed in the existing literature. This is a preliminary fundamental step as the creation of synthetic models requires well-founded theoretical and foundational boundaries for operationalising the concept of embodied and situated cognition in a concrete neuro-robotic model. By accepting the dynamical system view the agent is conceived as highly integrated and strictly coupled with the surrounding environment. Therefore the antireductionist framework is followed during the analysis of such systems, using chaos theory to unveil global properties and information theory to describe the complex network of interactions among the heterogeneous sub-components. In the experimental section, several evolutionary robotics experiments are discussed. This class of adaptive systems is consistent with the proposed definition of embodied and situated cognition. In fact, such neuro-robotics platforms autonomously develop a solution to a problem exploiting the continuous sensorimotor interaction with the environment. The first experiment is a stress test for chaos theory, a mathematical framework that studies erratic behaviour in low-dimensional and deterministic dynamical systems. The recorded dataset consists of the robots’ position in the environment during the execution of the task. Subsequently, the time series is projected onto a multidimensional phase space in order to study the underlying dynamic using chaotic numerical descriptors. Finally, such measures are correlated and confronted with the robots’ behavioural strategy and the performance in novel and unpredictable environments. The second experiment explores the possible applications of information-theoretic measures for the analysis of embodied and situated systems. Data is recorded from perceptual and motor neurons while robots are executing a wall-following task and pairwise estimations of the mutual information and the transfer entropy are calculated in order to create an exhaustive map of the nonlinear interactions among variables. Results show that the set of information-theoretic employed in this study unveils characteristics of the agent-environemnt interaction and the functional neural structure. This work aims at testing the explanatory power and impotence of nonlinear time series analysis applied to observables recorded from neuro-robotics embodied and situated systems

Local Positive Velocity Feedback for the movement control of elastic joints in closed kinematic chains : a modelling and simulation study of a 2DoF arm and a 3DoF insect leg

Schneider A. Local Positive Velocity Feedback for the movement control of elastic joints in closed kinematic chains : a modelling and simulation study of a 2DoF arm and a 3DoF insect leg. Bielefeld (Germany): Bielefeld University; 2006.In der Beinbewegungssteuerung von laufenden Tieren (z.B. in unserem Modellsystem, der indischen Stabheuschrecke Carausius morosus) unterscheidet man Stemm- und Schwingbewegungen. Während einer Schwingbewegung hat das schwingende Bein keinerlei Objektkontakt, da es vom Boden abgehoben duch die Luft nach vorne geführt wird. Das Bein kann als offene kinematische Kette betrachtet und jedes Gelenk der Kette frei bewegt werden. Während der Stemmbewegung haben alle beteiligten Beine Bodenkontakt und bilden somit geschlossene kinematische Ketten. Die Gelenkwinkel derjenigen Beine, die an diesen geschlossenen kinematischen Ketten beteiligt sind, sind nicht mehr frei wählbar. Eine beliebige Einzelbewegung eines Gelenks führt zu Verspannungen in den kinematischen Ketten, die nur durch die aktive (entspannende) Bewegung anderer Gelenke aufgelöst werden können. Ähnliche Probleme treten auch bei Bewegungen mit Armen und Händen auf, wenn diese Manipulationsaufgaben mit Objektkontakt ausführen (z.B. beim Öffnen einer Tür durch einen Menschen). Aufgabenstellungen dieser Art werden in der Robotik unter dem Begriff "compliant motion tasks" zusammengefasst. Beispiele hierfür sind Kontaktschweißen, kooperative Manipulation von Objekten durch mehrere Roboter, Pick-and-Place Aufgaben bei Montagerobotern und, wie erwähnt, auch Stemmbewegungen bei Laufmaschinen. Klassische Lösungsansätze für diese Art von Problemen basieren auf dem "hybrid control" Ansatz von Raibert und Craig (Raibert and Craig, 1981, Trans. of the ASME, 102: 126-133) oder auf dem "impedance control" Ansatz von Hogan (Hogan, 1985, ASME J. Dynam. Syst., Meas., Contr., 107: 1-23). Für die Ansteuerung einer sechsbeinigen Laufmaschine mit insgesamt 18 Gelenken müssen dafür die entsprechenden kinematischen und dynamischen Gleichungen bekannt sein und in jedem Regleraufruf neu berechnet werden. Es scheint unwahrscheinlich, dass Tiere diese Berechnungen explizit durchführen. Cruse und Mitarbeiter (Cruse et al., 1995, Advances in Artificial Life, 668-678) schlugen vor, dass Insekten diese Aufgabe unter Ausnutzung der in der Literatur vielfach beschriebenen Reflexumkehr (auch Unterstützungsreflex) bewältigen (siehe z.B. Bässler, 1976, Biol. Cybernetics, 24: 47-49). Bei der Reflexumkehr unterstützt ein Regelmechanismus, der im ruhenden Tier für die Beibehaltung einer Gelenksposition bei äußeren Störungen sorgt, im aktiven Tier eine passive Bewegung und verstärkt diese aktiv. Nimmt man nun im stemmenden Tier eine aktive Bewegung eines Gelenks an, so wirkt sich diese mechanisch vermittelt über die geschlossenen Ketten auf alle anderen Gelenke aus. Der Unterstützungsreflex in den anderen Gelenken führt dazu, dass diese die angeregte Bewegung mitmachen und verstärken. Das Ergebnis ist eine koordinierte Stemmbewegung, die von den lokal geregelten Gelenken gemeinsam ausgeführt wird, obwohl diese nicht neuronal miteinander kommunizieren und keine zentrale Instanz einen vorausberechneten Bewegungsplan ausgibt. In der vorliegenden Arbeit wird diese Hypothese aufgegriffen und quantitativ überprüft. Es werden verschiedene elastische Gelenkmodelle entwickelt, die als Grundlage für die Implementierung eines Unterstützungsreflex dienen. Der Unterstützungsreflex als solcher wird in Form von Lokaler Positiver Geschwindigkeitsrückkopplung (Local Positive Velocity Feedback, LPVF) hergeleitet und seine Funktionsfähigkeit mit einem Standardtest, dem einarmigen Kurbeln, getestet. Die wichtigste Eigenschaft, nämlich die Fähigkeit, verschiedene Gelenke ohne direkte Kommunikation zu koordinieren, wird damit nachgewiesen. In einem weiteren Schritt wird gezeigt, dass eine Erweiterung des Ansatzes durch Einführung einer Leistungssteuerung dazu führt, dass die Koordinationsfähigkeit selbst dann erhalten bleibt, wenn eine stemmende Gliedmaße große Kräfte, z.B. gegen eine äußere Trägheitskraft, aufbringen muss. Das Regelungskonzept wird auf einer dynamischen Einbeinsimulation getestet, die Funktionsfähigkeit demonstriert und mit den biologischen Daten von aktivierten Tieren verglichen. In einem letzten Schritt wird der LPVF-Regler mit einem Stehregler kombiniert. Der entstandene Gesamtregler erklärt biologische Befunde aus der Lauf- und aus der Stehdomäne

Trajectory analysis using point distribution models:algorithms, performance evaluation, and experimental validation using mobile robots

This thesis focuses on the analysis of the trajectories of a mobile agent. It presents different techniques to acquire a quantitative measure of the difference between two trajectories or two trajectory datasets. A novel approach is presented here, based on the Point Distribution Model (PDM). This model was developed by computer vision scientists to compare deformable shapes. This thesis presents the mathematical reformulation of the PDM to fit spatiotemporal data, such as trajectory information. The behavior of a mobile agent can rarely be represented by a unique trajectory, as its stochastic component will not be taken into account. Thus, the PDM focuses on the comparison of trajectory datasets. If the difference between datasets is greater than the variation within each dataset, it will be observable in the first few dimensions of the PDM. Moreover, this difference can also be quantified using the inter-cluster distance defined in this thesis. The resulting measure is much more efficient than visual comparisons of trajectories, as are often made in existing scientific literature. This thesis also compares the PDM with standard techniques, such as statistical tests, Hidden Markov Models (HMMs) or Correlated Random Walk (CRW) models. As a PDM is a linear transformation of space, it is much simpler to comprehend. Moreover, spatial representations of the deformation modes can easily be constructed in order to make the model more intuitive. This thesis also presents the limits of the PDM and offers other solutions when it is not adequate. From the different results obtained, it can be pointed out that no universal solution exists for the analysis of trajectories, however, solutions were found and described for all of the problems presented in this thesis. As the PDM requires that all the trajectories consist of the same number of points, techniques of resampling were studied. The main solution was developed for trajectories generated on a track, such as the trajectory of a car on a road or the trajectory of a pedestrian in a hallway. The different resampling techniques presented in this thesis provide solutions to all the experimental setups studied, and can easily be modified to fit other scenarios. It is however very important to understand how they work and to tune their parameters according to the characteristics of the experimental setup. The main principle of this thesis is that analysis techniques and data representations must be appropriately selected with respect to the fundamental goal. Even a simple tool such as the t-test can occasionally be sufficient to measure trajectory differences. However, if no dissimilarity can be observed, it does not necessarily mean that the trajectories are equal – it merely indicates that the analyzed feature is similar. Alternatively, other more complex methods could be used to highlight differences. Ultimately, two trajectories are equal if and only if they consist of the exact same sequence of points. Otherwise, a difference can always be found. Thus, it is important to know which trajectory features have to be compared. Finally, the diverse techniques used in this thesis offer a complete methodology to analyze trajectories