Consensus-based Distributed 3D Pose Estimation with Noisy Relative Measurements

In this paper we study consensus-based tributed estimation algorithms for estimating the global translation and rotation of each agent in a multi-agent system. We consider the case in which agents measure the noisy relative pose of their neighbors and communicate their estimates to agree upon the global poses in an arbitrary reference frame. The main contribution of this paper is a formal analysis that provides necessary and sufficient conditions to guarantee stability (in a Lyapunov sense) of the estimation system''s equilibria. We prove that consensus-based algorithms will diverge, even with arbitrarily small inconsistencies on the relative pose, unless the measurements satisfy minimum consistency conditions. We determine these consistency conditions for translation-only, rotation-only, and combined 3D pose estimation using the axis-angle rotation representation over undirected graphs. We then propose an initialization method based on these conditions that guarantees consistency and stability of the estimator''s equilibria. Additionally, we show that existing distributed estimation methods in literature exploit these conditions to guarantee convergence of their algorithms. Lastly, we perform simulations that show convergence when consistency conditions hold and divergence when they do not

Managing Organizational Anxiety with Information Systems

This conceptual paper explores the issue of organizational anxiety as well as reactions and possible solutions. Building on the general solutions we explore how Information Systems can be used to manage organizational anxiety

SME Adoption of Wireless LAN Technology: Applying the UTAUT Model

Wireless network technologies present unique opportunities and challenges for businesses, and Small & Medium Enterprises (SMEs) are no exception. Recently Vankatesh et al. (2003) proposed a more complete model for the understanding of the acceptance and adoption of Information Technology. Their model builds upon and extends beyond the well established Technology Acceptance Model (TAM). This study utilizes this new Unified Theory of Acceptance and Use of Technology (UTAUT) to further validate the model and enhance our understanding of the adoption of wireless technologies as well as SME adoption

Fractal Substructure of a Nanopowder

The structural evolution of a nano-powder by repeated dispersion and settling can lead to characteristic fractal substructures. This is shown by numerical simulations of a two-dimensional model agglomerate of adhesive rigid particles. The agglomerate is cut into fragments of a characteristic size l, which then are settling under gravity. Repeating this procedure converges to a loosely packed structure, the properties of which are investigated: a) The final packing density is independent of the initialization, b) the short-range correlation function is independent of the fragment size, c) the structure is fractal up to the fragmentation scale l with a fractal dimension close to 1.7, and d) the relaxation time increases linearly with l.Comment: 4 pages, 8 figure

Decentralized Adaptive Control for Collaborative Manipulation of Rigid Bodies

In this work, we consider a group of robots working together to manipulate a rigid object to track a desired trajectory in $SE(3)$. The robots do not know the mass or friction properties of the object, or where they are attached to the object. They can, however, access a common state measurement, either from one robot broadcasting its measurements to the team, or by all robots communicating and averaging their state measurements to estimate the state of their centroid. To solve this problem, we propose a decentralized adaptive control scheme wherein each agent maintains and adapts its own estimate of the object parameters in order to track a reference trajectory. We present an analysis of the controller's behavior, and show that all closed-loop signals remain bounded, and that the system trajectory will almost always (except for initial conditions on a set of measure zero) converge to the desired trajectory. We study the proposed controller's performance using numerical simulations of a manipulation task in 3D, as well as hardware experiments which demonstrate our algorithm on a planar manipulation task. These studies, taken together, demonstrate the effectiveness of the proposed controller even in the presence of numerous unmodeled effects, such as discretization errors and complex frictional interactions

A Real-Time Game Theoretic Planner for Autonomous Two-Player Drone Racing

In this article, we propose an online 3-D planning algorithm for a drone to race competitively against a single adversary drone. The algorithm computes an approximation of the Nash equilibrium in the joint space of trajectories of the two drones at each time step, and proceeds in a receding horizon fashion. The algorithm uses a novel sensitivity term, within an iterative best response computational scheme, to approximate the amount by which the adversary will yield to the ego drone to avoid a collision. This leads to racing trajectories that are more competitive than without the sensitivity term. We prove that the fixed point of this sensitivity enhanced iterative best response satisfies the first-order optimality conditions of a Nash equilibrium. We present results of a simulation study of races with 2-D and 3-D race courses, showing that our game theoretic planner significantly outperforms amodel predictive control (MPC) racing algorithm. We also present results of multiple drone racing experiments on a 3-D track in which drones sense each others'' relative position with onboard vision. The proposed game theoretic planner again outperforms the MPC opponent in these experiments where drones reach speeds up to 1.25m/s

Unexpected systematic degeneracy in a system of two coupled Gaudin models with homogeneous couplings

We report an unexpected systematic degeneracy between different multiplets in an inversion symmetric system of two coupled Gaudin models with homogeneous couplings, as occurring for example in the context of solid state quantum information processing. We construct the full degenerate subspace (being of macroscopic dimension), which turns out to lie in the kernel of the commutator between the two Gaudin models and the coupling term. Finally we investigate to what extend the degeneracy is related to the inversion symmetry of the system and find that indeed there is a large class of systems showing the same type of degeneracy.Comment: 13 pages, 4 figure

Unifying geometric, probabilistic, and potential field approaches to multi-robot deployment

This paper unifies and extends several different existing strategies for deploying groups of robots in an environment. A cost function is proposed that can be specialized to represent widely different multi-robot deployment tasks. It is shown that geometric and probabilistic deployment strategies that were previously seen as distinct are in fact related through this cost function, and differ only in the value of a single parameter. These strategies are also related to potential field-based controllers through the same cost function, though the relationship is not as simple. Distributed controllers are then obtained from the gradient of the cost function and are proved to converge to a local minimum of the cost function. Three special cases are derived as examples: a Voronoi-based coverage control task, a probabilistic minimum variance task, and a task using artificial potential fields. The performance of the three different controllers are compared in simulation. A result is also proved linking multi-robot deployment to non-convex optimization problems, and multi-robot consensus (i.e. all robots moving to the same point) to convex optimization problems, which implies that multi-robot deployment is inherently more difficult than multi-robot consensus.United States. Office of Naval Research. Multidisciplinary University Research Initiative. Smarts (Grant N00014-09-1-1051)United States. Army Research Office. Multidisciplinary University Research Initiative. Scalable Swarms of Autonomous Robots and Mobile Sensors Project (Grant W911NF-05-1-0219)National Science Foundation (U.S.) (Grant IIS-0513755)National Science Foundation (U.S.) (Grant IIS-0426838)National Science Foundation (U.S.) (Grant CNS-0520305)National Science Foundation (U.S.) (Grant CNS-0707601)National Science Foundation (U.S.) (Grant EFRI-0735953

The Drivers for Acceptance of Tablet PCs by Faculty in a College of Business

Utilizing the Unified Theory of Acceptance and Use of Technology (UTAUT) model developed by Venkatesh, et al. (2003) this study extends our understanding of technology acceptance, provides insights into the use of UTAUT as a tool to increase our understanding of acceptance, and identifies areas that administrators should consider when proposing a new technology in a College of Business setting. UTAUT is a useful tool for managers to predict the likelihood of success for new technology introductions and helps managers understand the drivers of acceptance in order to proactively design interventions targeted at users that may be less inclined to adopt and use new systems. The Tablet PC is a new technology being introduced in various settings including faculty and student use in higher education. This study applies UTAUT prescriptively as a management tool to asses the user acceptance of Tablet PCs by the faculty of a College of Business at a large university in the United States. The results largely validate UTAUT, although the findings suggest that certain variables, namely performance expectancy and voluntariness, are the most salient drivers of acceptance when applied to business faculty in higher education

Duplicated Hox genes in the spider Cupiennius salei

BACKGROUND: Hox genes are expressed in specific domains along the anterior posterior body axis and define the regional identity. In most animals these genes are organized in a single cluster in the genome and the order of the genes in the cluster is correlated with the anterior to posterior expression of the genes in the embryo. The conserved order of the various Hox gene orthologs in the cluster among most bilaterians implies that such a Hox cluster was present in their last common ancestor. Vertebrates are the only metazoans so far that have been shown to contain duplicated Hox clusters, while all other bilaterians seem to possess only a single cluster. RESULTS: We here show that at least three Hox genes of the spider Cupiennius salei are present as two copies in this spider. In addition to the previously described duplicated Ultrabithorax gene, we here present sequence and expression data of a second Deformed gene, and of two Sex comb reduced genes. In addition, we describe the sequence and expression of the Cupiennius proboscipedia gene. The spider Cupiennius salei is the first chelicerate for which orthologs of all ten classes of arthropod Hox genes have been described. The posterior expression boundary of all anterior Hox genes is at the tagma border of the prosoma and opisthosoma, while the posterior boundary of the posterior Hox genes is at the posterior end of the embryo. CONCLUSION: The presence of at least three duplicated Hox genes points to a major duplication event in the lineage to this spider, perhaps even of the complete Hox cluster as has taken place in the lineage to the vertebrates. The combined data of all Cupiennius Hox genes reveal the existence of two distinct posterior expression boundaries that correspond to morphological tagmata boundaries