44,072 research outputs found
Air vehicle simulator: an application for a cable array robot
The development of autonomous air vehicles can be an expensive research pursuit. To alleviate some of the financial burden of this process, we have constructed a system consisting of four winches each attached to a central pod (the simulated air vehicle) via cables - a cable-array robot. The system is capable of precisely controlling the three dimensional position of the pod allowing effective testing of sensing and control strategies before experimentation on a free-flying vehicle. In this paper, we present a brief overview of the system and provide a practical control strategy for such a system. ©2005 IEEE
Maunakea Spectroscopic Explorer (MSE) - The Prime Focus Subsystems: Requirements and Interfaces
MSE will be a massively multiplexed survey telescope, including a segmented
primary mirror which feeds fibers at the prime focus, including an array of
approximately four thousand fibers, positioned precisely to feed banks of
spectrographs several tens of meters away. We describe the process of mapping
top-level requirements on MSE to technical specifications for subsystems
located at the MSE prime focus. This includes the overall top-level
requirements based on knowledge of similar systems at other telescopes and how
those requirements were converted into specifications so that the subsystems
could begin working on their Conceptual Design Phases. We then discuss the
verification of the engineering specifications and the compiling of lower-level
requirements and specifications into higher level performance budgets (e.g.
Image Quality). We also briefly discuss the interface specifications, their
effect on the performance of the system and the plan to manage them going
forward. We also discuss the opto-mechanical design of the telescope top end
assembly and refer readers to more details for instrumentation located at the
top end.Comment: 14 pages; Proceedings of SPIE Astronomical Telescopes +
Instrumentation 2018; Modeling, Systems Engineering, and Project Management
for Astronomy VII
Force and Motion Generation of Molecular Motors: A Generic Description
We review the properties of biological motor proteins which move along linear
filaments that are polar and periodic. The physics of the operation of such
motors can be described by simple stochastic models which are coupled to a
chemical reaction. We analyze the essential features of force and motion
generation and discuss the general properties of single motors in the framework
of two-state models. Systems which contain large numbers of motors such as
muscles and flagella motivate the study of many interacting motors within the
framework of simple models. In this case, collective effects can lead to new
types of behaviors such as dynamic instabilities of the steady states and
oscillatory motion.Comment: 29 pages, 9 figure
Modeling and inference of multisubject fMRI data
Functional magnetic resonance imaging (fMRI) is a
rapidly growing technique for studying the brain in
action. Since its creation [1], [2], cognitive scientists
have been using fMRI to understand how we remember,
manipulate, and act on information in our environment.
Working with magnetic resonance physicists, statisticians, and
engineers, these scientists are pushing the frontiers of knowledge
of how the human brain works.
The design and analysis of single-subject fMRI studies
has been well described. For example, [3], chapters 10
and 11 of [4], and chapters 11 and 14 of [5] all give accessible
overviews of fMRI methods for one subject. In contrast,
while the appropriate manner to analyze a group of
subjects has been the topic of several recent papers, we do
not feel it has been covered well in introductory texts and
review papers. Therefore, in this article, we bring together
old and new work on so-called group modeling of fMRI
data using a consistent notation to make the methods more
accessible and comparable
Information driven self-organization of complex robotic behaviors
Information theory is a powerful tool to express principles to drive
autonomous systems because it is domain invariant and allows for an intuitive
interpretation. This paper studies the use of the predictive information (PI),
also called excess entropy or effective measure complexity, of the sensorimotor
process as a driving force to generate behavior. We study nonlinear and
nonstationary systems and introduce the time-local predicting information
(TiPI) which allows us to derive exact results together with explicit update
rules for the parameters of the controller in the dynamical systems framework.
In this way the information principle, formulated at the level of behavior, is
translated to the dynamics of the synapses. We underpin our results with a
number of case studies with high-dimensional robotic systems. We show the
spontaneous cooperativity in a complex physical system with decentralized
control. Moreover, a jointly controlled humanoid robot develops a high
behavioral variety depending on its physics and the environment it is
dynamically embedded into. The behavior can be decomposed into a succession of
low-dimensional modes that increasingly explore the behavior space. This is a
promising way to avoid the curse of dimensionality which hinders learning
systems to scale well.Comment: 29 pages, 12 figure
Disentangling causal webs in the brain using functional Magnetic Resonance Imaging: A review of current approaches
In the past two decades, functional Magnetic Resonance Imaging has been used
to relate neuronal network activity to cognitive processing and behaviour.
Recently this approach has been augmented by algorithms that allow us to infer
causal links between component populations of neuronal networks. Multiple
inference procedures have been proposed to approach this research question but
so far, each method has limitations when it comes to establishing whole-brain
connectivity patterns. In this work, we discuss eight ways to infer causality
in fMRI research: Bayesian Nets, Dynamical Causal Modelling, Granger Causality,
Likelihood Ratios, LiNGAM, Patel's Tau, Structural Equation Modelling, and
Transfer Entropy. We finish with formulating some recommendations for the
future directions in this area
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