A macroscopic analytical model of collaboration in distributed robotic systems

In this article, we present a macroscopic analytical model of collaboration in a group of reactive robots. The model consists of a series of coupled differential equations that describe the dynamics of group behavior. After presenting the general model, we analyze in detail a case study of collaboration, the stick-pulling experiment, studied experimentally and in simulation by Ijspeert et al. [Autonomous Robots, 11, 149-171]. The robots' task is to pull sticks out of their holes, and it can be successfully achieved only through the collaboration of two robots. There is no explicit communication or coordination between the robots. Unlike microscopic simulations (sensor-based or using a probabilistic numerical model), in which computational time scales with the robot group size, the macroscopic model is computationally efficient, because its solutions are independent of robot group size. Analysis reproduces several qualitative conclusions of Ijspeert et al.: namely, the different dynamical regimes for different values of the ratio of robots to sticks, the existence of optimal control parameters that maximize system performance as a function of group size, and the transition from superlinear to sublinear performance as the number of robots is increased

Collective Complexity out of Individual Simplicity

The concept of Swarm Intelligence (SI) was first introduced by Gerardo Beni, Suzanne Hackwood, and Jing Wang in 1989 when they were investigating the properties of simulated, self-organizing agents in the framework of cellular robotic systems [1]. Eric Bonabeau, Marco Dorigo, and Guy Theraulaz extend the restrictive context of this early work to include “any attempt to design algorithms or distributed problem-solving devices inspired by the collective behavior of social insect colonies,” such as ants, termites, bees, wasps, “and other animal societies.” The abilities of such systems appear to transcend the abilities of the constituent individuals. In most biological cases studied so far, robust and capable high-level group behavior has been found to be mediated by nothing more than a small set of simple low-level interactions between individuals, and between individuals and the environment. The SI approach, therefore, emphasizes parallelism, distributedness, and exploitation of direct (agent-to-agent) or indirect (via the environment) local interactions among relatively simple agents

Pinniped processing and consumption: early littoral occupations at Imiwaia I site, Tierra del fuego, República Argentina

El objetivo general de este artículo es analizar los patrones de procesamiento y consumo de pinnípedos en las ocupaciones canoeras tempranas de la región del canal Beagle. A tal efecto, se evalúan las modalidades explotación de dichos mamíferos marinos a través de los conjuntos óseos recuperados en depósitos arqueológicos del sitio Imiwaia I (Tierra del Fuego, Argentina) con cronologías cercanas a 6000 AP. Se presentan los perfiles de edad y sexo de los individuos explotados, así como el estudio detallado de las modificaciones óseas. Losresultados muestran: a) un predominio de especímenes juveniles/subadultos de sexo indeterminado y machos adultos de Arctocephalus australis; b) la mayoría de las unidades anatómicas de tales individuos están representadas; y c) las marcas de corte se encuentran concentradas sobre las regiones proximales y distales de las diáfisis de huesos largos y sobre sectores proximales y mediales de las costillas. Estos datos permitirían sostener que la captura de la generalidad de las presas identificadas posiblemente no se produjo en loberías de reproducción.Los individuos probablemente ingresaron enteros al sitio, donde sufrieron una desarticulación primaria y luego la reducción en porciones más pequeñas.The main objective of this article is to analyze the processing and consumption patterns of pinnipeds in the early human occupations of the Beagle Channel region. In order to achieve this aim, the modes of exploitation of these marine mammals is evaluated on the basis of the bone assemblages recovered from archaeological deposits at Imiwaia I site (Tierra del Fuego, Argentina), dated to around 6000 years BP. The age and sex profiles of exploited animals is presented, as well as a detailed study of bone modifications. The results show: a) a clear predominance of juvenile/subadult indeterminate sex and male adult specimens of Arctocephalus australis; b) all anatomical units of these individuals are present; and c) cut marks are mostly represented on the proximal and distal regions of long bone diaphyses and on the proximal and medial areas of ribs. These data support the view that it is unlikely that most of the identified prey were captured in rookeries. The animals arrived whole at the site, where they underwent primary disarticulation and then were butchered into smaller portions.Fil: Martinoli, Maria Paz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Modeling and Analysis of Beaconless and Beacon-Based Policies for a Swarm-Intelligent Inspection System

We are developing a swarm-intelligent inspection system based on a swarm of autonomous, miniature robots, using only on-board, local sensors. To estimate intrinsic advantages and limitations of the proposed possible distributed control solution, we capture the dynamic of the system at a higher abstraction level using non-spatial probabilistic microscopic and macroscopic models. In a previous publication, we showed that we are able to predict quantitatively the performances of the swarm of robots for a given metric and a beaconless policy. In this paper, after briefly reviewing our modeling methodology, we explore the effect of adding an additional state to the individual robot controller, which allow robots to serve as a beacon for teammates and therefore bias their inspection routes. Results show that this additional complexity helps the swarm of robots to be more efficient in terms of energy consumption but not necessarily in terms of time required to complete the inspection. We also demonstrate that a beacon-based policy introduces a strong coupling among the behavior of robots, coupling which in turn results in nonlinearities at the macroscopic model level

Plant food economy and environment during the epipalaeolithic in southwest Anatolia : an investigation of the botanical macroremains from Öküzini and Karain B

Located in southwest Turkey, not far from the seacoast, the natural caves of Öküzini and Karain B were inhabited by prehistoric populations during the Late Glacial and beyond. The Epipalaeolithic populations left traces of different occupation phases dated between 16.560 ±180 uncal BP (18.200-17.400 cal BC) to 12.130 ±100 uncal BP (14.400-11.800 cal BC) in Öküzini, around 15.000 uncal BP in Karain B. The topic of this research was to examine the macrobotanical remains associated with the Epipalaeolithic occupations, with the underlying aims to acquire insights about the economy of these communities and their use of the environmental resources. A first research paper addresses the issue of plant macroremain identification, in particular the identification of „thick shelled“ plant remains. Morphological comparison with the range of potential species and present geographical distribution made it possible to refine the determination to a double species: Amygdalus orientalis or A. graeca. These plants could grow in the surroundings of the sites on rocky slopes or sandy hills and had to be collected during late summer. All wild Amygdalus seeds are toxic, so that their use as food can be disputed. However, through examination of the detoxification possibilities, nutritional properties and ethnographic analogies for the use of wild almonds, we came to the conclusion that the seeds probably played a notable role in the diet of the Epipalaeolithic population of southwest Anatolia. A comparison with further published prehistoric “nutshell” finds from the Near East supports a long and widely distributed tradition of wild almond use. The analyses of the whole plant macroremain assemblages (excluding wood charcoals) identified at least 18 taxa and “categories” of remains, mainly carbonised. The importance and the role of the plants – particularly in the diet and their bearing on the seasonality of occupation of the sites – have been evaluated with quantitative and qualitative data. Nuts (principally Amygdalus, wild almond), fruits (principally Pyrus, wild pear), bulbs, roots or tubers (underground storage organs) seem to have occupied a particularly important place in these communities during all Epipalaeolithic phases, at the expense of small-seeded plants. The attested plants would have provided carbohydrates, lipids and micronutrients complementing well the meat diet. The cost of acquisition of the major plant resources was estimated: nuts and underground storage organs were generally considered as high ranked resources, providing a resource easy to gather and to process for a high calorific return. The almonds had a higher cost of acquisition. Their richness in fats and their availability at the onset of the winter season however could justify the additional work required for their detoxification. Judging from the seasonality indices of the plants and ungulate fauna at Öküzini, the cave could have been inhabited periodically in all seasons, but particularly in spring and autumn. A third paper presented the use of firewood and palaeoenvironmental reconstruction using anthracological and other environmental data. The diversity of fuel wood used was moderate and at both sites Acer (maple), Amygdalus (wild almond) and Fraxinus (ash) were the most common and important taxa. Secondary taxa were composed of Maloideae, Pyrus (wild pear), Prunus (wild plum), Quercus (cadufoliate oak), and Rhamnus/Phillyrea (buckthorn/mock privet). No chronological changes were observed. The major difference between both caves was the presence of hygrophilous and mesophillous taxa in Öküzini, whereas Coniferous wood was more common in Karain B, leading to the interpretation of an opportunistic exploitation of the surroundings of each site. Despite the poverty of the Late Glacial vegetation, there was no indication of use of alternative fuel material. These Epipalaeolithic populations seem to have responded to shortages rather through mobility than intensification. The anthracological results have been integrated to present-day knowledge of the environment of southwest Anatolia in an attempt to reconstruct the local vegetation. Among the different models of optimal foraging, the diet breadth model predicts that the resource a forager chooses from an available set of resources depends on their efficiency rank and abundance in the environment. Knowing from former investigations what plant resources were collected by the Epipalaeolithic populations from Öküzini and Karain B, we used this model to estimate the richness of the various classes of plant resources in the environment of the sites. An exploitation of high ranked plant resources, the nuts and the roots, bulbs or tubers, instead of small seeds, probably reflected their good availability in the environment. On the other hand, although the pattern of fuel use did not show any indices of wood scarcity, the reconstruction of the vegetation resulted in an environment not particularly rich in plant resources. The density of population being low, we suppose that the Epipalaeolithic populations living in this region adapted to their natural conditions in moving regularly their camps

Identifying endocarp remains and exploring their use at Epipalaeolithic Öküzini in southwest Anatolia, Turkey

Excavation of the Epipalaeolithic levels of the cave site Öküzini in southwest Anatolia produced many "nutshell” remains, mainly endocarp fragments belonging either to Prunus or Amygdalus. Morphological comparison with the range of potential species and present geographical distribution made it possible to refine the determination to either of two species of wild almond, Amygdalus orientalis or A. graeca . These plants could grow in the surroundings of the site on rocky slopes or sandy hills and had to be collected during late summer. All wild Amygdalus seeds are toxic, so that their use as food is disputed. This paper explores the detoxification possibilities, nutritional properties and ethnographic analogies for the use of wild almonds. It comes to the conclusion that the seeds probably played a notable role in the diet of the Epipalaeolithic population of southwest Anatolia, complementing meat and other plant food. An examination of further prehistoric "nutshell” finds from Anatolia supports a long and widely distributed tradition of almond us